Unleashed v1.4

[unleashed.git] / kernel / os / exec.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 1988, 2010, Oracle and/or its affiliates. All rights reserved.
 */

/*      Copyright (c) 1988 AT&T */
/*        All Rights Reserved   */
/*
 * Copyright 2017 Joyent, Inc.
 */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/sysmacros.h>
#include <sys/systm.h>
#include <sys/signal.h>
#include <sys/cred_impl.h>
#include <sys/policy.h>
#include <sys/user.h>
#include <sys/errno.h>
#include <sys/file.h>
#include <sys/vfs.h>
#include <sys/vnode.h>
#include <sys/mman.h>
#include <sys/acct.h>
#include <sys/cpuvar.h>
#include <sys/proc.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/pathname.h>
#include <sys/vm.h>
#include <sys/lgrp.h>
#include <sys/vtrace.h>
#include <sys/exec.h>
#include <sys/exechdr.h>
#include <sys/kmem.h>
#include <sys/prsystm.h>
#include <sys/modctl.h>
#include <sys/vmparam.h>
#include <sys/door.h>
#include <sys/schedctl.h>
#include <sys/utrap.h>
#include <sys/systeminfo.h>
#include <sys/stack.h>
#include <sys/rctl.h>
#include <sys/dtrace.h>
#include <sys/lwpchan_impl.h>
#include <sys/pool.h>
#include <sys/sdt.h>
#include <sys/brand.h>
#include <sys/klpd.h>
#include <sys/random.h>

#include <vm/hat.h>
#include <vm/anon.h>
#include <vm/as.h>
#include <vm/seg.h>
#include <vm/seg_vn.h>
#include <vm/seg_hole.h>

#define PRIV_RESET              0x01    /* needs to reset privs */
#define PRIV_SETID              0x02    /* needs to change uids */
#define PRIV_SETUGID            0x04    /* is setuid/setgid/forced privs */
#define PRIV_INCREASE           0x08    /* child runs with more privs */
#define PRIV_FORCED             0x20    /* has forced privileges */

static int execsetid(struct vnode *, struct vattr *, uid_t *, uid_t *,
    priv_set_t *, cred_t *, const char *);
static int hold_execsw(struct execsw *);

uint_t auxv_hwcap = 0;  /* auxv AT_SUN_HWCAP value; determined on the fly */
uint_t auxv_hwcap_2 = 0;        /* AT_SUN_HWCAP2 */
#if defined(_SYSCALL32_IMPL)
uint_t auxv_hwcap32 = 0;        /* 32-bit version of auxv_hwcap */
uint_t auxv_hwcap32_2 = 0;      /* 32-bit version of auxv_hwcap2 */
#endif

#define PSUIDFLAGS              (SNOCD|SUGID)

/*
 * These are consumed within the specific exec modules, but are defined here
 * because
 *
 * 1) The exec modules are unloadable, which would make this near useless.
 *
 * 2) We want them to be common across all of them, should more than ELF come
 *    to support them.
 *
 * All must be powers of 2.
 */
size_t aslr_max_brk_skew = 16 * 1024 * 1024; /* 16MB */
#pragma weak exec_stackgap = aslr_max_stack_skew /* Old, compatible name */
size_t aslr_max_stack_skew = 64 * 1024; /* 64KB */

/*
 * Size of guard segment for 64-bit processes and minimum size it can be shrunk
 * to in the case of grow() operations.  These are kept as variables in case
 * they need to be tuned in an emergency.
 */
size_t stack_guard_seg_sz = 256 * 1024 * 1024;
size_t stack_guard_min_sz = 64 * 1024 * 1024;

/*
 * exece() - system call wrapper around exec_common()
 */
int
exece(const char *fname, const char **argp, const char **envp)
{
        int error;

        error = exec_common(fname, argp, envp, EBA_NONE);
        return (error ? (set_errno(error)) : 0);
}

int
exec_common(const char *fname, const char **argp, const char **envp,
    int brand_action)
{
        vnode_t *vp = NULL, *dir = NULL, *tmpvp = NULL;
        proc_t *p = ttoproc(curthread);
        klwp_t *lwp = ttolwp(curthread);
        struct user *up = PTOU(p);
        long execsz;            /* temporary count of exec size */
        int i;
        int error;
        char exec_file[MAXCOMLEN+1];
        struct pathname pn;
        struct pathname resolvepn;
        struct uarg args;
        struct execa ua;
        k_sigset_t savedmask;
        lwpdir_t *lwpdir = NULL;
        tidhash_t *tidhash;
        lwpdir_t *old_lwpdir = NULL;
        uint_t old_lwpdir_sz;
        tidhash_t *old_tidhash;
        uint_t old_tidhash_sz;
        ret_tidhash_t *ret_tidhash;
        lwpent_t *lep;
        boolean_t brandme = B_FALSE;

        /*
         * exec() is not supported for the /proc agent lwp.
         */
        if (curthread == p->p_agenttp)
                return (ENOTSUP);

        if (brand_action != EBA_NONE) {
                /*
                 * Brand actions are not supported for processes that are not
                 * running in a branded zone.
                 */
                if (!ZONE_IS_BRANDED(p->p_zone))
                        return (ENOTSUP);

                if (brand_action == EBA_NATIVE) {
                        /* Only branded processes can be unbranded */
                        if (!PROC_IS_BRANDED(p))
                                return (ENOTSUP);
                } else {
                        /* Only unbranded processes can be branded */
                        if (PROC_IS_BRANDED(p))
                                return (ENOTSUP);
                        brandme = B_TRUE;
                }
        } else {
                /*
                 * If this is a native zone, or if the process is already
                 * branded, then we don't need to do anything.  If this is
                 * a native process in a branded zone, we need to brand the
                 * process as it exec()s the new binary.
                 */
                if (ZONE_IS_BRANDED(p->p_zone) && !PROC_IS_BRANDED(p))
                        brandme = B_TRUE;
        }

        /*
         * Inform /proc that an exec() has started.
         * Hold signals that are ignored by default so that we will
         * not be interrupted by a signal that will be ignored after
         * successful completion of gexec().
         */
        mutex_enter(&p->p_lock);
        prexecstart();
        schedctl_finish_sigblock(curthread);
        savedmask = curthread->t_hold;
        sigorset(&curthread->t_hold, &ignoredefault);
        mutex_exit(&p->p_lock);

        /*
         * Look up path name and remember last component for later.
         * To help coreadm expand its %d token, we attempt to save
         * the directory containing the executable in p_execdir. The
         * first call to lookuppn() may fail and return EINVAL because
         * dirvpp is non-NULL. In that case, we make a second call to
         * lookuppn() with dirvpp set to NULL; p_execdir will be NULL,
         * but coreadm is allowed to expand %d to the empty string and
         * there are other cases in which that failure may occur.
         */
        if ((error = pn_get((char *)fname, UIO_USERSPACE, &pn)) != 0)
                goto out;
        pn_alloc(&resolvepn);
        if ((error = lookuppn(&pn, &resolvepn, FOLLOW, &dir, &vp)) != 0) {
                pn_free(&resolvepn);
                pn_free(&pn);
                if (error != EINVAL)
                        goto out;

                dir = NULL;
                if ((error = pn_get((char *)fname, UIO_USERSPACE, &pn)) != 0)
                        goto out;
                pn_alloc(&resolvepn);
                if ((error = lookuppn(&pn, &resolvepn, FOLLOW, NULLVPP,
                    &vp)) != 0) {
                        pn_free(&resolvepn);
                        pn_free(&pn);
                        goto out;
                }
        }
        if (vp == NULL) {
                if (dir != NULL)
                        VN_RELE(dir);
                error = ENOENT;
                pn_free(&resolvepn);
                pn_free(&pn);
                goto out;
        }

        if ((error = secpolicy_basic_exec(CRED(), vp)) != 0) {
                if (dir != NULL)
                        VN_RELE(dir);
                pn_free(&resolvepn);
                pn_free(&pn);
                VN_RELE(vp);
                goto out;
        }

        /*
         * We do not allow executing files in attribute directories.
         * We test this by determining whether the resolved path
         * contains a "/" when we're in an attribute directory;
         * only if the pathname does not contain a "/" the resolved path
         * points to a file in the current working (attribute) directory.
         */
        if ((p->p_user.u_cdir->v_flag & V_XATTRDIR) != 0 &&
            strchr(resolvepn.pn_path, '/') == NULL) {
                if (dir != NULL)
                        VN_RELE(dir);
                error = EACCES;
                pn_free(&resolvepn);
                pn_free(&pn);
                VN_RELE(vp);
                goto out;
        }

        bzero(exec_file, MAXCOMLEN+1);
        (void) strncpy(exec_file, pn.pn_path, MAXCOMLEN);
        bzero(&args, sizeof (args));
        args.pathname = resolvepn.pn_path;
        /* don't free resolvepn until we are done with args */
        pn_free(&pn);

        /*
         * If we're running in a profile shell, then call pfexecd.
         */
        if ((CR_FLAGS(p->p_cred) & PRIV_PFEXEC) != 0) {
                error = pfexec_call(p->p_cred, &resolvepn, &args.pfcred,
                    &args.scrubenv);

                /* Returning errno in case we're not allowed to execute. */
                if (error > 0) {
                        if (dir != NULL)
                                VN_RELE(dir);
                        pn_free(&resolvepn);
                        VN_RELE(vp);
                        goto out;
                }

                /* Don't change the credentials when using old ptrace. */
                if (args.pfcred != NULL &&
                    (p->p_proc_flag & P_PR_PTRACE) != 0) {
                        crfree(args.pfcred);
                        args.pfcred = NULL;
                        args.scrubenv = B_FALSE;
                }
        }

        /*
         * Specific exec handlers, or policies determined via
         * /etc/system may override the historical default.
         */
        args.stk_prot = PROT_ZFOD;
        args.dat_prot = PROT_ZFOD;

        CPU_STATS_ADD_K(sys, sysexec, 1);
        DTRACE_PROC1(exec, char *, args.pathname);

        ua.fname = fname;
        ua.argp = argp;
        ua.envp = envp;

        /* If necessary, brand this process before we start the exec. */
        if (brandme)
                brand_setbrand(p);

        if ((error = gexec(&vp, &ua, &args, NULL, 0, &execsz,
            exec_file, p->p_cred, brand_action)) != 0) {
                if (brandme)
                        brand_clearbrand(p, B_FALSE);
                VN_RELE(vp);
                if (dir != NULL)
                        VN_RELE(dir);
                pn_free(&resolvepn);
                goto fail;
        }

        /*
         * Free floating point registers (sun4u only)
         */
        ASSERT(lwp != NULL);
        lwp_freeregs(lwp, 1);

        /*
         * Free thread and process context ops.
         */
        if (curthread->t_ctx)
                freectx(curthread, 1);
        if (p->p_pctx)
                freepctx(p, 1);

        /*
         * Remember file name for accounting; clear any cached DTrace predicate.
         */
        up->u_acflag &= ~AFORK;
        bcopy(exec_file, up->u_comm, MAXCOMLEN+1);
        curthread->t_predcache = 0;

        /*
         * Clear contract template state
         */
        lwp_ctmpl_clear(lwp);

        /*
         * Save the directory in which we found the executable for expanding
         * the %d token used in core file patterns.
         */
        mutex_enter(&p->p_lock);
        tmpvp = p->p_execdir;
        p->p_execdir = dir;
        if (p->p_execdir != NULL)
                VN_HOLD(p->p_execdir);
        mutex_exit(&p->p_lock);

        if (tmpvp != NULL)
                VN_RELE(tmpvp);

        /*
         * Reset stack state to the user stack, clear set of signals
         * caught on the signal stack, and reset list of signals that
         * restart system calls; the new program's environment should
         * not be affected by detritus from the old program.  Any
         * pending held signals remain held, so don't clear t_hold.
         */
        mutex_enter(&p->p_lock);
        lwp->lwp_oldcontext = 0;
        lwp->lwp_ustack = 0;
        lwp->lwp_old_stk_ctl = 0;
        sigemptyset(&up->u_signodefer);
        sigemptyset(&up->u_sigonstack);
        sigemptyset(&up->u_sigresethand);
        lwp->lwp_sigaltstack.ss_sp = 0;
        lwp->lwp_sigaltstack.ss_size = 0;
        lwp->lwp_sigaltstack.ss_flags = SS_DISABLE;

        /*
         * Make saved resource limit == current resource limit.
         */
        for (i = 0; i < RLIM_NLIMITS; i++) {
                /*CONSTCOND*/
                if (RLIM_SAVED(i)) {
                        (void) rctl_rlimit_get(rctlproc_legacy[i], p,
                            &up->u_saved_rlimit[i]);
                }
        }

        /*
         * If the action was to catch the signal, then the action
         * must be reset to SIG_DFL.
         */
        sigdefault(p);
        p->p_flag &= ~(SNOWAIT|SJCTL);
        p->p_flag |= (SEXECED|SMSACCT|SMSFORK);
        up->u_signal[SIGCLD - 1] = SIG_DFL;

        /*
         * Delete the dot4 sigqueues/signotifies.
         */
        sigqfree(p);

        mutex_exit(&p->p_lock);

        mutex_enter(&p->p_pflock);
        p->p_prof.pr_base = NULL;
        p->p_prof.pr_size = 0;
        p->p_prof.pr_off = 0;
        p->p_prof.pr_scale = 0;
        p->p_prof.pr_samples = 0;
        mutex_exit(&p->p_pflock);

        ASSERT(curthread->t_schedctl == NULL);


        /*
         * Close all close-on-exec files.
         */
        close_exec(P_FINFO(p));
        TRACE_2(TR_FAC_PROC, TR_PROC_EXEC, "proc_exec:p %p up %p", p, up);

        /* Unbrand ourself if necessary. */
        if (PROC_IS_BRANDED(p) && (brand_action == EBA_NATIVE))
                brand_clearbrand(p, B_FALSE);

        setregs(&args);

        /* Mark this as an executable vnode */
        mutex_enter(&vp->v_lock);
        vp->v_flag |= VVMEXEC;
        mutex_exit(&vp->v_lock);

        VN_RELE(vp);
        if (dir != NULL)
                VN_RELE(dir);
        pn_free(&resolvepn);

        /*
         * Allocate a new lwp directory and lwpid hash table if necessary.
         */
        if (curthread->t_tid != 1 || p->p_lwpdir_sz != 2) {
                lwpdir = kmem_zalloc(2 * sizeof (lwpdir_t), KM_SLEEP);
                lwpdir->ld_next = lwpdir + 1;
                tidhash = kmem_zalloc(2 * sizeof (tidhash_t), KM_SLEEP);
                if (p->p_lwpdir != NULL)
                        lep = p->p_lwpdir[curthread->t_dslot].ld_entry;
                else
                        lep = kmem_zalloc(sizeof (*lep), KM_SLEEP);
        }

        if (PROC_IS_BRANDED(p))
                BROP(p)->b_exec();

        mutex_enter(&p->p_lock);
        prbarrier(p);

        /*
         * Reset lwp id to the default value of 1.
         * This is a single-threaded process now
         * and lwp #1 is lwp_wait()able by default.
         * The t_unpark flag should not be inherited.
         */
        ASSERT(p->p_lwpcnt == 1 && p->p_zombcnt == 0);
        curthread->t_tid = 1;
        kpreempt_disable();
        ASSERT(curthread->t_lpl != NULL);
        p->p_t1_lgrpid = curthread->t_lpl->lpl_lgrpid;
        kpreempt_enable();
        if (p->p_tr_lgrpid != LGRP_NONE && p->p_tr_lgrpid != p->p_t1_lgrpid) {
                lgrp_update_trthr_migrations(1);
        }
        curthread->t_unpark = 0;
        curthread->t_proc_flag |= TP_TWAIT;
        curthread->t_proc_flag &= ~TP_DAEMON;   /* daemons shouldn't exec */
        p->p_lwpdaemon = 0;                     /* but oh well ... */
        p->p_lwpid = 1;

        /*
         * Install the newly-allocated lwp directory and lwpid hash table
         * and insert the current thread into the new hash table.
         */
        if (lwpdir != NULL) {
                old_lwpdir = p->p_lwpdir;
                old_lwpdir_sz = p->p_lwpdir_sz;
                old_tidhash = p->p_tidhash;
                old_tidhash_sz = p->p_tidhash_sz;
                p->p_lwpdir = p->p_lwpfree = lwpdir;
                p->p_lwpdir_sz = 2;
                lep->le_thread = curthread;
                lep->le_lwpid = curthread->t_tid;
                lep->le_start = curthread->t_start;
                lwp_hash_in(p, lep, tidhash, 2, 0);
                p->p_tidhash = tidhash;
                p->p_tidhash_sz = 2;
        }
        ret_tidhash = p->p_ret_tidhash;
        p->p_ret_tidhash = NULL;

        /*
         * Restore the saved signal mask and
         * inform /proc that the exec() has finished.
         */
        curthread->t_hold = savedmask;
        prexecend();
        mutex_exit(&p->p_lock);
        if (old_lwpdir) {
                kmem_free(old_lwpdir, old_lwpdir_sz * sizeof (lwpdir_t));
                kmem_free(old_tidhash, old_tidhash_sz * sizeof (tidhash_t));
        }
        while (ret_tidhash != NULL) {
                ret_tidhash_t *next = ret_tidhash->rth_next;
                kmem_free(ret_tidhash->rth_tidhash,
                    ret_tidhash->rth_tidhash_sz * sizeof (tidhash_t));
                kmem_free(ret_tidhash, sizeof (*ret_tidhash));
                ret_tidhash = next;
        }

        ASSERT(error == 0);
        DTRACE_PROC(exec__success);
        return (0);

fail:
        DTRACE_PROC1(exec__failure, int, error);
out:            /* error return */
        mutex_enter(&p->p_lock);
        curthread->t_hold = savedmask;
        prexecend();
        mutex_exit(&p->p_lock);
        ASSERT(error != 0);
        return (error);
}


/*
 * Perform generic exec duties and switchout to object-file specific
 * handler.
 */
int
gexec(
        struct vnode **vpp,
        struct execa *uap,
        struct uarg *args,
        struct intpdata *idatap,
        int level,
        long *execsz,
        caddr_t exec_file,
        struct cred *cred,
        int brand_action)
{
        struct vnode *vp, *execvp = NULL;
        proc_t *pp = ttoproc(curthread);
        struct execsw *eswp;
        int error = 0;
        int suidflags = 0;
        ssize_t resid;
        uid_t uid, gid;
        struct vattr vattr;
        char magbuf[MAGIC_BYTES];
        int setid;
        cred_t *oldcred, *newcred = NULL;
        int privflags = 0;
        int setidfl;
        priv_set_t fset;
        secflagset_t old_secflags;

        secflags_copy(&old_secflags, &pp->p_secflags.psf_effective);

        /*
         * If the SNOCD or SUGID flag is set, turn it off and remember the
         * previous setting so we can restore it if we encounter an error.
         */
        if (level == 0 && (pp->p_flag & PSUIDFLAGS)) {
                mutex_enter(&pp->p_lock);
                suidflags = pp->p_flag & PSUIDFLAGS;
                pp->p_flag &= ~PSUIDFLAGS;
                mutex_exit(&pp->p_lock);
        }

        if ((error = execpermissions(*vpp, &vattr, args)) != 0)
                goto bad_noclose;

        /* need to open vnode for stateful file systems */
        if ((error = fop_open(vpp, FREAD, CRED(), NULL)) != 0)
                goto bad_noclose;
        vp = *vpp;

        /*
         * Note: to support binary compatibility with SunOS a.out
         * executables, we read in the first four bytes, as the
         * magic number is in bytes 2-3.
         */
        if (error = vn_rdwr(UIO_READ, vp, magbuf, sizeof (magbuf),
            0, UIO_SYSSPACE, 0, 0, CRED(), &resid))
                goto bad;
        if (resid != 0)
                goto bad;

        if ((eswp = findexec_by_hdr(magbuf)) == NULL)
                goto bad;

        if (level == 0 &&
            (privflags = execsetid(vp, &vattr, &uid, &gid, &fset,
            args->pfcred == NULL ? cred : args->pfcred, args->pathname)) != 0) {

                /* Pfcred is a credential with a ref count of 1 */

                if (args->pfcred != NULL) {
                        privflags |= PRIV_INCREASE|PRIV_RESET;
                        newcred = cred = args->pfcred;
                } else {
                        newcred = cred = crdup(cred);
                }

                /* If we can, drop the PA bit */
                if ((privflags & PRIV_RESET) != 0)
                        priv_adjust_PA(cred);

                if (privflags & PRIV_SETID) {
                        cred->cr_uid = uid;
                        cred->cr_gid = gid;
                        cred->cr_suid = uid;
                        cred->cr_sgid = gid;
                }

                /*
                 * Implement the privilege updates:
                 *
                 * Restrict with L:
                 *
                 *      I' = I & L
                 *
                 *      E' = P' = (I' + F) & A
                 *
                 * But if running under ptrace, we cap I and F with P.
                 */
                if ((privflags & (PRIV_RESET|PRIV_FORCED)) != 0) {
                        if ((privflags & PRIV_INCREASE) != 0 &&
                            (pp->p_proc_flag & P_PR_PTRACE) != 0) {
                                priv_intersect(&CR_OPPRIV(cred),
                                    &CR_IPRIV(cred));
                                priv_intersect(&CR_OPPRIV(cred), &fset);
                        }
                        priv_intersect(&CR_LPRIV(cred), &CR_IPRIV(cred));
                        CR_EPRIV(cred) = CR_PPRIV(cred) = CR_IPRIV(cred);
                        if (privflags & PRIV_FORCED) {
                                priv_set_PA(cred);
                                priv_union(&fset, &CR_EPRIV(cred));
                                priv_union(&fset, &CR_PPRIV(cred));
                        }
                        priv_adjust_PA(cred);
                }
        } else if (level == 0 && args->pfcred != NULL) {
                newcred = cred = args->pfcred;
                privflags |= PRIV_INCREASE;
                /* pfcred is not forced to adhere to these settings */
                priv_intersect(&CR_LPRIV(cred), &CR_IPRIV(cred));
                CR_EPRIV(cred) = CR_PPRIV(cred) = CR_IPRIV(cred);
                priv_adjust_PA(cred);
        }

        /* The new image gets the inheritable secflags as its secflags */
        secflags_promote(pp);

        /* SunOS 4.x buy-back */
        if ((vp->v_vfsp->vfs_flag & VFS_NOSETUID) &&
            (vattr.va_mode & (VSUID|VSGID))) {
                char path[MAXNAMELEN];
                refstr_t *mntpt = NULL;
                int ret = -1;

                bzero(path, sizeof (path));
                zone_hold(pp->p_zone);

                ret = vnodetopath(pp->p_zone->zone_rootvp, vp, path,
                    sizeof (path), cred);

                /* fallback to mountpoint if a path can't be found */
                if ((ret != 0) || (ret == 0 && path[0] == '\0'))
                        mntpt = vfs_getmntpoint(vp->v_vfsp);

                if (mntpt == NULL)
                        zcmn_err(pp->p_zone->zone_id, CE_NOTE,
                            "!uid %d: setuid execution not allowed, "
                            "file=%s", cred->cr_uid, path);
                else
                        zcmn_err(pp->p_zone->zone_id, CE_NOTE,
                            "!uid %d: setuid execution not allowed, "
                            "fs=%s, file=%s", cred->cr_uid,
                            ZONE_PATH_TRANSLATE(refstr_value(mntpt),
                            pp->p_zone), exec_file);

                if (!INGLOBALZONE(pp)) {
                        /* zone_rootpath always has trailing / */
                        if (mntpt == NULL)
                                cmn_err(CE_NOTE, "!zone: %s, uid: %d "
                                    "setuid execution not allowed, file=%s%s",
                                    pp->p_zone->zone_name, cred->cr_uid,
                                    pp->p_zone->zone_rootpath, path + 1);
                        else
                                cmn_err(CE_NOTE, "!zone: %s, uid: %d "
                                    "setuid execution not allowed, fs=%s, "
                                    "file=%s", pp->p_zone->zone_name,
                                    cred->cr_uid, refstr_value(mntpt),
                                    exec_file);
                }

                if (mntpt != NULL)
                        refstr_rele(mntpt);

                zone_rele(pp->p_zone);
        }

        /*
         * execsetid() told us whether or not we had to change the
         * credentials of the process.  In privflags, it told us
         * whether we gained any privileges or executed a set-uid executable.
         */
        setid = (privflags & (PRIV_SETUGID|PRIV_INCREASE|PRIV_FORCED));

        /*
         * Use /etc/system variable to determine if the stack
         * should be marked as executable by default.
         */
        if ((noexec_user_stack != 0) ||
            secflag_enabled(pp, PROC_SEC_NOEXECSTACK))
                args->stk_prot &= ~PROT_EXEC;

        args->execswp = eswp; /* Save execsw pointer in uarg for exec_func */
        args->ex_vp = vp;

        /*
         * Traditionally, the setid flags told the sub processes whether
         * the file just executed was set-uid or set-gid; this caused
         * some confusion as the 'setid' flag did not match the SUGID
         * process flag which is only set when the uids/gids do not match.
         * A script set-gid/set-uid to the real uid/gid would start with
         * /dev/fd/X but an executable would happily trust LD_LIBRARY_PATH.
         * Now we flag those cases where the calling process cannot
         * be trusted to influence the newly exec'ed process, either
         * because it runs with more privileges or when the uids/gids
         * do in fact not match.
         * This also makes the runtime linker agree with the on exec
         * values of SNOCD and SUGID.
         */
        setidfl = 0;
        if (cred->cr_uid != cred->cr_ruid || (cred->cr_rgid != cred->cr_gid &&
            !supgroupmember(cred->cr_gid, cred))) {
                setidfl |= EXECSETID_UGIDS;
        }
        if (setid & PRIV_SETUGID)
                setidfl |= EXECSETID_SETID;
        if (setid & PRIV_FORCED)
                setidfl |= EXECSETID_PRIVS;

        execvp = pp->p_exec;
        if (execvp)
                VN_HOLD(execvp);

        error = (*eswp->exec_func)(vp, uap, args, idatap, level, execsz,
            setidfl, exec_file, cred, brand_action);
        rw_exit(eswp->exec_lock);
        if (error != 0) {
                if (execvp)
                        VN_RELE(execvp);
                /*
                 * If this process's p_exec has been set to the vp of
                 * the executable by exec_func, we will return without
                 * calling fop_close because proc_exit will close it
                 * on exit.
                 */
                if (pp->p_exec == vp)
                        goto bad_noclose;
                else
                        goto bad;
        }

        if (level == 0) {
                uid_t oruid;

                if (execvp != NULL) {
                        /*
                         * Close the previous executable only if we are
                         * at level 0.
                         */
                        (void) fop_close(execvp, FREAD, 1, 0,
                            cred, NULL);
                }

                mutex_enter(&pp->p_crlock);

                oruid = pp->p_cred->cr_ruid;

                if (newcred != NULL) {
                        /*
                         * Free the old credentials, and set the new ones.
                         * Do this for both the process and the (single) thread.
                         */
                        crfree(pp->p_cred);
                        pp->p_cred = cred;      /* cred already held for proc */
                        crhold(cred);           /* hold new cred for thread */
                        /*
                         * DTrace accesses t_cred in probe context.  t_cred
                         * must always be either NULL, or point to a valid,
                         * allocated cred structure.
                         */
                        oldcred = curthread->t_cred;
                        curthread->t_cred = cred;
                        crfree(oldcred);

                        if (priv_basic_test >= 0 &&
                            !PRIV_ISMEMBER(&CR_IPRIV(newcred),
                            priv_basic_test)) {
                                pid_t pid = pp->p_pid;
                                char *fn = PTOU(pp)->u_comm;

                                cmn_err(CE_WARN, "%s[%d]: exec: basic_test "
                                    "privilege removed from E/I", fn, pid);
                        }
                }
                /*
                 * On emerging from a successful exec(), the saved
                 * uid and gid equal the effective uid and gid.
                 */
                cred->cr_suid = cred->cr_uid;
                cred->cr_sgid = cred->cr_gid;

                /*
                 * If the real and effective ids do not match, this
                 * is a setuid process that should not dump core.
                 * The group comparison is tricky; we prevent the code
                 * from flagging SNOCD when executing with an effective gid
                 * which is a supplementary group.
                 */
                if (cred->cr_ruid != cred->cr_uid ||
                    (cred->cr_rgid != cred->cr_gid &&
                    !supgroupmember(cred->cr_gid, cred)) ||
                    (privflags & PRIV_INCREASE) != 0)
                        suidflags = PSUIDFLAGS;
                else
                        suidflags = 0;

                mutex_exit(&pp->p_crlock);
                if (newcred != NULL && oruid != newcred->cr_ruid) {
                        /* Note that the process remains in the same zone. */
                        mutex_enter(&pidlock);
                        upcount_dec(oruid, crgetzoneid(newcred));
                        upcount_inc(newcred->cr_ruid, crgetzoneid(newcred));
                        mutex_exit(&pidlock);
                }
                if (suidflags) {
                        mutex_enter(&pp->p_lock);
                        pp->p_flag |= suidflags;
                        mutex_exit(&pp->p_lock);
                }
                if (setid && (pp->p_proc_flag & P_PR_PTRACE) == 0) {
                        /*
                         * If process is traced via /proc, arrange to
                         * invalidate the associated /proc vnode.
                         */
                        if (pp->p_plist || (pp->p_proc_flag & P_PR_TRACE))
                                args->traceinval = 1;
                }
                if (pp->p_proc_flag & P_PR_PTRACE)
                        psignal(pp, SIGTRAP);
                if (args->traceinval)
                        prinvalidate(&pp->p_user);
        }
        if (execvp)
                VN_RELE(execvp);
        return (0);

bad:
        (void) fop_close(vp, FREAD, 1, 0, cred, NULL);

bad_noclose:
        if (newcred != NULL)
                crfree(newcred);
        if (error == 0)
                error = ENOEXEC;

        mutex_enter(&pp->p_lock);
        if (suidflags) {
                pp->p_flag |= suidflags;
        }
        /*
         * Restore the effective secflags, to maintain the invariant they
         * never change for a given process
         */
        secflags_copy(&pp->p_secflags.psf_effective, &old_secflags);
        mutex_exit(&pp->p_lock);

        return (error);
}

extern char *execswnames[];

struct execsw *
allocate_execsw(char *name, char *magic, size_t magic_size)
{
        int i, j;
        char *ename;
        char *magicp;

        mutex_enter(&execsw_lock);
        for (i = 0; i < nexectype; i++) {
                if (execswnames[i] == NULL) {
                        ename = kmem_alloc(strlen(name) + 1, KM_SLEEP);
                        (void) strcpy(ename, name);
                        execswnames[i] = ename;
                        /*
                         * Set the magic number last so that we
                         * don't need to hold the execsw_lock in
                         * findexectype().
                         */
                        magicp = kmem_alloc(magic_size, KM_SLEEP);
                        for (j = 0; j < magic_size; j++)
                                magicp[j] = magic[j];
                        execsw[i].exec_magic = magicp;
                        mutex_exit(&execsw_lock);
                        return (&execsw[i]);
                }
        }
        mutex_exit(&execsw_lock);
        return (NULL);
}

/*
 * Find the exec switch table entry with the corresponding magic string.
 */
struct execsw *
findexecsw(char *magic)
{
        struct execsw *eswp;

        for (eswp = execsw; eswp < &execsw[nexectype]; eswp++) {
                ASSERT(eswp->exec_maglen <= MAGIC_BYTES);
                if (magic && eswp->exec_maglen != 0 &&
                    bcmp(magic, eswp->exec_magic, eswp->exec_maglen) == 0)
                        return (eswp);
        }
        return (NULL);
}

/*
 * Find the execsw[] index for the given exec header string by looking for the
 * magic string at a specified offset and length for each kind of executable
 * file format until one matches.  If no execsw[] entry is found, try to
 * autoload a module for this magic string.
 */
struct execsw *
findexec_by_hdr(char *header)
{
        struct execsw *eswp;

        for (eswp = execsw; eswp < &execsw[nexectype]; eswp++) {
                ASSERT(eswp->exec_maglen <= MAGIC_BYTES);
                if (header && eswp->exec_maglen != 0 &&
                    bcmp(&header[eswp->exec_magoff], eswp->exec_magic,
                    eswp->exec_maglen) == 0) {
                        if (hold_execsw(eswp) != 0)
                                return (NULL);
                        return (eswp);
                }
        }
        return (NULL);  /* couldn't find the type */
}

/*
 * Find the execsw[] index for the given magic string.  If no execsw[] entry
 * is found, try to autoload a module for this magic string.
 */
struct execsw *
findexec_by_magic(char *magic)
{
        struct execsw *eswp;

        for (eswp = execsw; eswp < &execsw[nexectype]; eswp++) {
                ASSERT(eswp->exec_maglen <= MAGIC_BYTES);
                if (magic && eswp->exec_maglen != 0 &&
                    bcmp(magic, eswp->exec_magic, eswp->exec_maglen) == 0) {
                        if (hold_execsw(eswp) != 0)
                                return (NULL);
                        return (eswp);
                }
        }
        return (NULL);  /* couldn't find the type */
}

static int
hold_execsw(struct execsw *eswp)
{
        char *name;

        rw_enter(eswp->exec_lock, RW_READER);
        while (!LOADED_EXEC(eswp)) {
                rw_exit(eswp->exec_lock);
                name = execswnames[eswp-execsw];
                ASSERT(name);
                if (modload("exec", name) == -1)
                        return (-1);
                rw_enter(eswp->exec_lock, RW_READER);
        }
        return (0);
}

static int
execsetid(struct vnode *vp, struct vattr *vattrp, uid_t *uidp, uid_t *gidp,
    priv_set_t *fset, cred_t *cr, const char *pathname)
{
        proc_t *pp = ttoproc(curthread);
        uid_t uid, gid;
        int privflags = 0;

        /*
         * Remember credentials.
         */
        uid = cr->cr_uid;
        gid = cr->cr_gid;

        /* Will try to reset the PRIV_AWARE bit later. */
        if ((CR_FLAGS(cr) & (PRIV_AWARE|PRIV_AWARE_INHERIT)) == PRIV_AWARE)
                privflags |= PRIV_RESET;

        if ((vp->v_vfsp->vfs_flag & VFS_NOSETUID) == 0) {
                /*
                 * If it's a set-uid root program we perform the
                 * forced privilege look-aside. This has three possible
                 * outcomes:
                 *      no look aside information -> treat as before
                 *      look aside in Limit set -> apply forced privs
                 *      look aside not in Limit set -> ignore set-uid root
                 *
                 * Ordinary set-uid root execution only allowed if the limit
                 * set holds all unsafe privileges.
                 */
                if (vattrp->va_mode & VSUID) {
                        if (vattrp->va_uid == 0) {
                                int res = get_forced_privs(cr, pathname, fset);

                                switch (res) {
                                case -1:
                                        if (priv_issubset(&priv_unsafe,
                                            &CR_LPRIV(cr))) {
                                                uid = vattrp->va_uid;
                                                privflags |= PRIV_SETUGID;
                                        }
                                        break;
                                case 0:
                                        privflags |= PRIV_FORCED|PRIV_INCREASE;
                                        break;
                                default:
                                        break;
                                }
                        } else {
                                uid = vattrp->va_uid;
                                privflags |= PRIV_SETUGID;
                        }
                }
                if (vattrp->va_mode & VSGID) {
                        gid = vattrp->va_gid;
                        privflags |= PRIV_SETUGID;
                }
        }

        /*
         * Do we need to change our credential anyway?
         * This is the case when E != I or P != I, as
         * we need to do the assignments (with F empty and A full)
         * Or when I is not a subset of L; in that case we need to
         * enforce L.
         *
         *              I' = L & I
         *
         *              E' = P' = (I' + F) & A
         * or
         *              E' = P' = I'
         */
        if (!priv_isequalset(&CR_EPRIV(cr), &CR_IPRIV(cr)) ||
            !priv_issubset(&CR_IPRIV(cr), &CR_LPRIV(cr)) ||
            !priv_isequalset(&CR_PPRIV(cr), &CR_IPRIV(cr)))
                privflags |= PRIV_RESET;

        /* Child has more privileges than parent */
        if (!priv_issubset(&CR_IPRIV(cr), &CR_PPRIV(cr)))
                privflags |= PRIV_INCREASE;

        /*
         * Set setuid/setgid protections if no ptrace() compatibility.
         * For privileged processes, honor setuid/setgid even in
         * the presence of ptrace() compatibility.
         */
        if (((pp->p_proc_flag & P_PR_PTRACE) == 0 ||
            PRIV_POLICY_ONLY(cr, PRIV_PROC_OWNER, (uid == 0))) &&
            (cr->cr_uid != uid ||
            cr->cr_gid != gid ||
            cr->cr_suid != uid ||
            cr->cr_sgid != gid)) {
                *uidp = uid;
                *gidp = gid;
                privflags |= PRIV_SETID;
        }
        return (privflags);
}

int
execpermissions(struct vnode *vp, struct vattr *vattrp, struct uarg *args)
{
        int error;
        proc_t *p = ttoproc(curthread);

        vattrp->va_mask = VATTR_MODE | VATTR_UID | VATTR_GID | VATTR_SIZE;
        if (error = fop_getattr(vp, vattrp, ATTR_EXEC, p->p_cred, NULL))
                return (error);
        /*
         * Check the access mode.
         * If VPROC, ask /proc if the file is an object file.
         */
        if ((error = fop_access(vp, VEXEC, 0, p->p_cred, NULL)) != 0 ||
            !(vp->v_type == VREG || (vp->v_type == VPROC && pr_isobject(vp))) ||
            (vp->v_vfsp->vfs_flag & VFS_NOEXEC) != 0 ||
            (vattrp->va_mode & (VEXEC|(VEXEC>>3)|(VEXEC>>6))) == 0) {
                if (error == 0)
                        error = EACCES;
                return (error);
        }

        if ((p->p_plist || (p->p_proc_flag & (P_PR_PTRACE|P_PR_TRACE))) &&
            (error = fop_access(vp, VREAD, 0, p->p_cred, NULL))) {
                /*
                 * If process is under ptrace(2) compatibility,
                 * fail the exec(2).
                 */
                if (p->p_proc_flag & P_PR_PTRACE)
                        goto bad;
                /*
                 * Process is traced via /proc.
                 * Arrange to invalidate the /proc vnode.
                 */
                args->traceinval = 1;
        }
        return (0);
bad:
        if (error == 0)
                error = ENOEXEC;
        return (error);
}

/*
 * Map a section of an executable file into the user's
 * address space.
 */
int
execmap(struct vnode *vp, caddr_t addr, size_t len, size_t zfodlen,
    off_t offset, int prot, int page, uint_t szc)
{
        int error = 0;
        off_t oldoffset;
        caddr_t zfodbase, oldaddr;
        size_t end, oldlen;
        size_t zfoddiff;
        label_t ljb;
        proc_t *p = ttoproc(curthread);

        oldaddr = addr;
        addr = (caddr_t)((uintptr_t)addr & (uintptr_t)PAGEMASK);
        if (len) {
                oldlen = len;
                len += ((size_t)oldaddr - (size_t)addr);
                oldoffset = offset;
                offset = (off_t)((uintptr_t)offset & PAGEMASK);
                if (page) {
                        spgcnt_t  prefltmem, availm, npages;
                        int preread;
                        uint_t mflag = MAP_PRIVATE | MAP_FIXED;

                        if ((prot & (PROT_WRITE | PROT_EXEC)) == PROT_EXEC) {
                                mflag |= MAP_TEXT;
                        } else {
                                mflag |= MAP_INITDATA;
                        }

                        if (valid_usr_range(addr, len, prot, p->p_as,
                            p->p_as->a_userlimit) != RANGE_OKAY) {
                                error = ENOMEM;
                                goto bad;
                        }
                        if (error = fop_map(vp, (offset_t)offset,
                            p->p_as, &addr, len, prot, PROT_ALL,
                            mflag, CRED(), NULL))
                                goto bad;

                        /*
                         * If the segment can fit, then we prefault
                         * the entire segment in.  This is based on the
                         * model that says the best working set of a
                         * small program is all of its pages.
                         */
                        npages = (spgcnt_t)btopr(len);
                        prefltmem = freemem - desfree;
                        preread =
                            (npages < prefltmem && len < PGTHRESH) ? 1 : 0;

                        /*
                         * If we aren't prefaulting the segment,
                         * increment "deficit", if necessary to ensure
                         * that pages will become available when this
                         * process starts executing.
                         */
                        availm = freemem - lotsfree;
                        if (preread == 0 && npages > availm &&
                            deficit < lotsfree) {
                                deficit += MIN((pgcnt_t)(npages - availm),
                                    lotsfree - deficit);
                        }

                        if (preread) {
                                TRACE_2(TR_FAC_PROC, TR_EXECMAP_PREREAD,
                                    "execmap preread:freemem %d size %lu",
                                    freemem, len);
                                (void) as_fault(p->p_as->a_hat, p->p_as,
                                    (caddr_t)addr, len, F_INVAL, S_READ);
                        }
                } else {
                        if (valid_usr_range(addr, len, prot, p->p_as,
                            p->p_as->a_userlimit) != RANGE_OKAY) {
                                error = ENOMEM;
                                goto bad;
                        }

                        if (error = as_map(p->p_as, addr, len,
                            segvn_create, zfod_argsp))
                                goto bad;
                        /*
                         * Read in the segment in one big chunk.
                         */
                        if (error = vn_rdwr(UIO_READ, vp, (caddr_t)oldaddr,
                            oldlen, (offset_t)oldoffset, UIO_USERSPACE, 0,
                            0, CRED(), NULL))
                                goto bad;
                        /*
                         * Now set protections.
                         */
                        if (prot != PROT_ZFOD) {
                                (void) as_setprot(p->p_as, (caddr_t)addr,
                                    len, prot);
                        }
                }
        }

        if (zfodlen) {
                struct as *as = curproc->p_as;
                struct seg *seg;
                uint_t zprot = 0;

                end = (size_t)addr + len;
                zfodbase = (caddr_t)roundup(end, PAGESIZE);
                zfoddiff = (uintptr_t)zfodbase - end;
                if (zfoddiff) {
                        /*
                         * Before we go to zero the remaining space on the last
                         * page, make sure we have write permission.
                         *
                         * Normal illumos binaries don't even hit the case
                         * where we have to change permission on the last page
                         * since their protection is typically either
                         *    PROT_USER | PROT_WRITE | PROT_READ
                         * or
                         *    PROT_ZFOD (same as PROT_ALL).
                         *
                         * We need to be careful how we zero-fill the last page
                         * if the segment protection does not include
                         * PROT_WRITE. Using as_setprot() can cause the VM
                         * segment code to call segvn_vpage(), which must
                         * allocate a page struct for each page in the segment.
                         * If we have a very large segment, this may fail, so
                         * we have to check for that, even though we ignore
                         * other return values from as_setprot.
                         */

                        AS_LOCK_ENTER(as, RW_READER);
                        seg = as_segat(curproc->p_as, (caddr_t)end);
                        if (seg != NULL)
                                (void) segop_getprot(seg, (caddr_t)end,
                                    zfoddiff - 1, &zprot);
                        AS_LOCK_EXIT(as);

                        if (seg != NULL && (zprot & PROT_WRITE) == 0) {
                                if (as_setprot(as, (caddr_t)end, zfoddiff - 1,
                                    zprot | PROT_WRITE) == ENOMEM) {
                                        error = ENOMEM;
                                        goto bad;
                                }
                        }

                        if (on_fault(&ljb)) {
                                no_fault();
                                if (seg != NULL && (zprot & PROT_WRITE) == 0)
                                        (void) as_setprot(as, (caddr_t)end,
                                            zfoddiff - 1, zprot);
                                error = EFAULT;
                                goto bad;
                        }
                        uzero((void *)end, zfoddiff);
                        no_fault();
                        if (seg != NULL && (zprot & PROT_WRITE) == 0)
                                (void) as_setprot(as, (caddr_t)end,
                                    zfoddiff - 1, zprot);
                }
                if (zfodlen > zfoddiff) {
                        struct segvn_crargs crargs =
                            SEGVN_ZFOD_ARGS(PROT_ZFOD, PROT_ALL);

                        zfodlen -= zfoddiff;
                        if (valid_usr_range(zfodbase, zfodlen, prot, p->p_as,
                            p->p_as->a_userlimit) != RANGE_OKAY) {
                                error = ENOMEM;
                                goto bad;
                        }
                        if (szc > 0) {
                                /*
                                 * ASSERT alignment because the mapelfexec()
                                 * caller for the szc > 0 case extended zfod
                                 * so it's end is pgsz aligned.
                                 */
                                size_t pgsz = page_get_pagesize(szc);
                                ASSERT(IS_P2ALIGNED(zfodbase + zfodlen, pgsz));

                                if (IS_P2ALIGNED(zfodbase, pgsz)) {
                                        crargs.szc = szc;
                                } else {
                                        crargs.szc = AS_MAP_HEAP;
                                }
                        } else {
                                crargs.szc = AS_MAP_NO_LPOOB;
                        }
                        if (error = as_map(p->p_as, (caddr_t)zfodbase,
                            zfodlen, segvn_create, &crargs))
                                goto bad;
                        if (prot != PROT_ZFOD) {
                                (void) as_setprot(p->p_as, (caddr_t)zfodbase,
                                    zfodlen, prot);
                        }
                }
        }
        return (0);
bad:
        return (error);
}

void
setexecenv(struct execenv *ep)
{
        proc_t *p = ttoproc(curthread);
        klwp_t *lwp = ttolwp(curthread);
        struct vnode *vp;

        p->p_bssbase = ep->ex_bssbase;
        p->p_brkbase = ep->ex_brkbase;
        p->p_brksize = ep->ex_brksize;
        if (p->p_exec)
                VN_RELE(p->p_exec);     /* out with the old */
        vp = p->p_exec = ep->ex_vp;
        if (vp != NULL)
                VN_HOLD(vp);            /* in with the new */

        lwp->lwp_sigaltstack.ss_sp = 0;
        lwp->lwp_sigaltstack.ss_size = 0;
        lwp->lwp_sigaltstack.ss_flags = SS_DISABLE;
}

int
execopen(struct vnode **vpp, int *fdp)
{
        struct vnode *vp = *vpp;
        file_t *fp;
        int error = 0;
        int filemode = FREAD;

        VN_HOLD(vp);            /* open reference */
        if (error = falloc(NULL, filemode, &fp, fdp)) {
                VN_RELE(vp);
                *fdp = -1;      /* just in case falloc changed value */
                return (error);
        }
        if (error = fop_open(&vp, filemode, CRED(), NULL)) {
                VN_RELE(vp);
                setf(*fdp, NULL);
                unfalloc(fp);
                *fdp = -1;
                return (error);
        }
        *vpp = vp;              /* vnode should not have changed */
        fp->f_vnode = vp;
        mutex_exit(&fp->f_tlock);
        setf(*fdp, fp);
        return (0);
}

int
execclose(int fd)
{
        return (closeandsetf(fd, NULL));
}


/*
 * noexec stub function.
 */
/*ARGSUSED*/
int
noexec(
    struct vnode *vp,
    struct execa *uap,
    struct uarg *args,
    struct intpdata *idatap,
    int level,
    long *execsz,
    int setid,
    caddr_t exec_file,
    struct cred *cred)
{
        cmn_err(CE_WARN, "missing exec capability for %s", uap->fname);
        return (ENOEXEC);
}

/*
 * Support routines for building a user stack.
 *
 * execve(path, argv, envp) must construct a new stack with the specified
 * arguments and environment variables (see exec_args() for a description
 * of the user stack layout).  To do this, we copy the arguments and
 * environment variables from the old user address space into the kernel,
 * free the old as, create the new as, and copy our buffered information
 * to the new stack.  Our kernel buffer has the following structure:
 *
 *      +-----------------------+ <--- stk_base + stk_size
 *      | string offsets        |
 *      +-----------------------+ <--- stk_offp
 *      |                       |
 *      | STK_AVAIL() space     |
 *      |                       |
 *      +-----------------------+ <--- stk_strp
 *      | strings               |
 *      +-----------------------+ <--- stk_base
 *
 * When we add a string, we store the string's contents (including the null
 * terminator) at stk_strp, and we store the offset of the string relative to
 * stk_base at --stk_offp.  At strings are added, stk_strp increases and
 * stk_offp decreases.  The amount of space remaining, STK_AVAIL(), is just
 * the difference between these pointers.  If we run out of space, we return
 * an error and exec_args() starts all over again with a buffer twice as large.
 * When we're all done, the kernel buffer looks like this:
 *
 *      +-----------------------+ <--- stk_base + stk_size
 *      | argv[0] offset        |
 *      +-----------------------+
 *      | ...                   |
 *      +-----------------------+
 *      | argv[argc-1] offset   |
 *      +-----------------------+
 *      | envp[0] offset        |
 *      +-----------------------+
 *      | ...                   |
 *      +-----------------------+
 *      | envp[envc-1] offset   |
 *      +-----------------------+
 *      | AT_SUN_PLATFORM offset|
 *      +-----------------------+
 *      | AT_SUN_EXECNAME offset|
 *      +-----------------------+ <--- stk_offp
 *      |                       |
 *      | STK_AVAIL() space     |
 *      |                       |
 *      +-----------------------+ <--- stk_strp
 *      | AT_SUN_EXECNAME offset|
 *      +-----------------------+
 *      | AT_SUN_PLATFORM offset|
 *      +-----------------------+
 *      | envp[envc-1] string   |
 *      +-----------------------+
 *      | ...                   |
 *      +-----------------------+
 *      | envp[0] string        |
 *      +-----------------------+
 *      | argv[argc-1] string   |
 *      +-----------------------+
 *      | ...                   |
 *      +-----------------------+
 *      | argv[0] string        |
 *      +-----------------------+ <--- stk_base
 */

#define STK_AVAIL(args)         ((char *)(args)->stk_offp - (args)->stk_strp)

/*
 * Add a string to the stack.
 */
static int
stk_add(uarg_t *args, const char *sp, enum uio_seg segflg)
{
        int error;
        size_t len;

        if (STK_AVAIL(args) < sizeof (int))
                return (E2BIG);
        *--args->stk_offp = args->stk_strp - args->stk_base;

        if (segflg == UIO_USERSPACE) {
                error = copyinstr(sp, args->stk_strp, STK_AVAIL(args), &len);
                if (error != 0)
                        return (error);
        } else {
                len = strlen(sp) + 1;
                if (len > STK_AVAIL(args))
                        return (E2BIG);
                bcopy(sp, args->stk_strp, len);
        }

        args->stk_strp += len;

        return (0);
}

static int
stk_getptr(uarg_t *args, char *src, char **dst)
{
        int error;

        if (args->from_model == DATAMODEL_NATIVE) {
                ulong_t ptr;
                error = fulword(src, &ptr);
                *dst = (caddr_t)ptr;
        } else {
                uint32_t ptr;
                error = fuword32(src, &ptr);
                *dst = (caddr_t)(uintptr_t)ptr;
        }
        return (error);
}

static int
stk_putptr(uarg_t *args, char *addr, char *value)
{
        if (args->to_model == DATAMODEL_NATIVE)
                return (sulword(addr, (ulong_t)value));
        else
                return (suword32(addr, (uint32_t)(uintptr_t)value));
}

static int
stk_copyin(execa_t *uap, uarg_t *args, intpdata_t *intp, void **auxvpp)
{
        char *sp;
        int argc, error;
        int argv_empty = 0;
        size_t ptrsize = args->from_ptrsize;
        size_t size, pad;
        char *argv = (char *)uap->argp;
        char *envp = (char *)uap->envp;

        /*
         * Copy interpreter's name and argument to argv[0] and argv[1].
         * In the rare case that we have nested interpreters then those names
         * and arguments are also copied to the subsequent slots in argv.
         */
        if (intp != NULL && intp->intp_name[0] != NULL) {
                int i;

                for (i = 0; i < INTP_MAXDEPTH; i++) {
                        if (intp->intp_name[i] == NULL)
                                break;
                        error = stk_add(args, intp->intp_name[i], UIO_SYSSPACE);
                        if (error != 0)
                                return (error);
                        if (intp->intp_arg[i] != NULL) {
                                error = stk_add(args, intp->intp_arg[i],
                                    UIO_SYSSPACE);
                                if (error != 0)
                                        return (error);
                        }
                }

                if (args->fname != NULL)
                        error = stk_add(args, args->fname, UIO_SYSSPACE);
                else
                        error = stk_add(args, uap->fname, UIO_USERSPACE);
                if (error)
                        return (error);

                /*
                 * Check for an empty argv[].
                 */
                if (stk_getptr(args, argv, &sp))
                        return (EFAULT);
                if (sp == NULL)
                        argv_empty = 1;

                argv += ptrsize;                /* ignore original argv[0] */
        }

        if (argv_empty == 0) {
                /*
                 * Add argv[] strings to the stack.
                 */
                for (;;) {
                        if (stk_getptr(args, argv, &sp))
                                return (EFAULT);
                        if (sp == NULL)
                                break;
                        if ((error = stk_add(args, sp, UIO_USERSPACE)) != 0)
                                return (error);
                        argv += ptrsize;
                }
        }
        argc = (int *)(args->stk_base + args->stk_size) - args->stk_offp;
        args->arglen = args->stk_strp - args->stk_base;

        /*
         * Add environ[] strings to the stack.
         */
        if (envp != NULL) {
                for (;;) {
                        char *tmp = args->stk_strp;
                        if (stk_getptr(args, envp, &sp))
                                return (EFAULT);
                        if (sp == NULL)
                                break;
                        if ((error = stk_add(args, sp, UIO_USERSPACE)) != 0)
                                return (error);
                        if (args->scrubenv && strncmp(tmp, "LD_", 3) == 0) {
                                /* Undo the copied string */
                                args->stk_strp = tmp;
                                *(args->stk_offp++) = 0;
                        }
                        envp += ptrsize;
                }
        }
        args->na = (int *)(args->stk_base + args->stk_size) - args->stk_offp;
        args->ne = args->na - argc;

        /*
         * Add AT_SUN_PLATFORM, AT_SUN_EXECNAME, AT_SUN_BRANDNAME, and
         * AT_SUN_EMULATOR strings to the stack.
         */
        if (auxvpp != NULL && *auxvpp != NULL) {
                if ((error = stk_add(args, platform, UIO_SYSSPACE)) != 0)
                        return (error);
                if ((error = stk_add(args, args->pathname, UIO_SYSSPACE)) != 0)
                        return (error);
                if (args->brandname != NULL &&
                    (error = stk_add(args, args->brandname, UIO_SYSSPACE)) != 0)
                        return (error);
                if (args->emulator != NULL &&
                    (error = stk_add(args, args->emulator, UIO_SYSSPACE)) != 0)
                        return (error);
        }

        /*
         * Compute the size of the stack.  This includes all the pointers,
         * the space reserved for the aux vector, and all the strings.
         * The total number of pointers is args->na (which is argc + envc)
         * plus 4 more: (1) a pointer's worth of space for argc; (2) the NULL
         * after the last argument (i.e. argv[argc]); (3) the NULL after the
         * last environment variable (i.e. envp[envc]); and (4) the NULL after
         * all the strings, at the very top of the stack.
         */
        size = (args->na + 4) * args->to_ptrsize + args->auxsize +
            (args->stk_strp - args->stk_base);

        /*
         * Pad the string section with zeroes to align the stack size.
         */
        pad = P2NPHASE(size, args->stk_align);

        if (STK_AVAIL(args) < pad)
                return (E2BIG);

        args->usrstack_size = size + pad;

        while (pad-- != 0)
                *args->stk_strp++ = 0;

        args->nc = args->stk_strp - args->stk_base;

        return (0);
}

static int
stk_copyout(uarg_t *args, char *usrstack, void **auxvpp, user_t *up)
{
        size_t ptrsize = args->to_ptrsize;
        ssize_t pslen;
        char *kstrp = args->stk_base;
        char *ustrp = usrstack - args->nc - ptrsize;
        char *usp = usrstack - args->usrstack_size;
        int *offp = (int *)(args->stk_base + args->stk_size);
        int envc = args->ne;
        int argc = args->na - envc;
        int i;

        /*
         * Record argc for /proc.
         */
        up->u_argc = argc;

        /*
         * Put argc on the stack.  Note that even though it's an int,
         * it always consumes ptrsize bytes (for alignment).
         */
        if (stk_putptr(args, usp, (char *)(uintptr_t)argc))
                return (-1);

        /*
         * Add argc space (ptrsize) to usp and record argv for /proc.
         */
        up->u_argv = (uintptr_t)(usp += ptrsize);

        /*
         * Put the argv[] pointers on the stack.
         */
        for (i = 0; i < argc; i++, usp += ptrsize)
                if (stk_putptr(args, usp, &ustrp[*--offp]))
                        return (-1);

        /*
         * Copy arguments to u_psargs.
         */
        pslen = MIN(args->arglen, PSARGSZ) - 1;
        for (i = 0; i < pslen; i++)
                up->u_psargs[i] = (kstrp[i] == '\0' ? ' ' : kstrp[i]);
        while (i < PSARGSZ)
                up->u_psargs[i++] = '\0';

        /*
         * Add space for argv[]'s NULL terminator (ptrsize) to usp and
         * record envp for /proc.
         */
        up->u_envp = (uintptr_t)(usp += ptrsize);

        /*
         * Put the envp[] pointers on the stack.
         */
        for (i = 0; i < envc; i++, usp += ptrsize)
                if (stk_putptr(args, usp, &ustrp[*--offp]))
                        return (-1);

        /*
         * Add space for envp[]'s NULL terminator (ptrsize) to usp and
         * remember where the stack ends, which is also where auxv begins.
         */
        args->stackend = usp += ptrsize;

        /*
         * Put all the argv[], envp[], and auxv strings on the stack.
         */
        if (copyout(args->stk_base, ustrp, args->nc))
                return (-1);

        /*
         * Fill in the aux vector now that we know the user stack addresses
         * for the AT_SUN_PLATFORM, AT_SUN_EXECNAME, AT_SUN_BRANDNAME and
         * AT_SUN_EMULATOR strings.
         */
        if (auxvpp != NULL && *auxvpp != NULL) {
                if (args->to_model == DATAMODEL_NATIVE) {
                        auxv_t **a = (auxv_t **)auxvpp;
                        ADDAUX(*a, AT_SUN_PLATFORM, (long)&ustrp[*--offp])
                        ADDAUX(*a, AT_SUN_EXECNAME, (long)&ustrp[*--offp])
                        if (args->brandname != NULL)
                                ADDAUX(*a,
                                    AT_SUN_BRANDNAME, (long)&ustrp[*--offp])
                        if (args->emulator != NULL)
                                ADDAUX(*a,
                                    AT_SUN_EMULATOR, (long)&ustrp[*--offp])
                } else {
                        auxv32_t **a = (auxv32_t **)auxvpp;
                        ADDAUX(*a,
                            AT_SUN_PLATFORM, (int)(uintptr_t)&ustrp[*--offp])
                        ADDAUX(*a,
                            AT_SUN_EXECNAME, (int)(uintptr_t)&ustrp[*--offp])
                        if (args->brandname != NULL)
                                ADDAUX(*a, AT_SUN_BRANDNAME,
                                    (int)(uintptr_t)&ustrp[*--offp])
                        if (args->emulator != NULL)
                                ADDAUX(*a, AT_SUN_EMULATOR,
                                    (int)(uintptr_t)&ustrp[*--offp])
                }
        }

        return (0);
}

/*
 * Though the actual stack base is constant, slew the %sp by a random aligned
 * amount in [0,aslr_max_stack_skew).  Mostly, this makes life slightly more
 * complicated for buffer overflows hoping to overwrite the return address.
 *
 * On some platforms this helps avoid cache thrashing when identical processes
 * simultaneously share caches that don't provide enough associativity
 * (e.g. sun4v systems). In this case stack slewing makes the same hot stack
 * variables in different processes live in different cache sets increasing
 * effective associativity.
 */
size_t
exec_get_spslew(void)
{
#ifdef sun4v
        static uint_t sp_color_stride = 16;
        static uint_t sp_color_mask = 0x1f;
        static uint_t sp_current_color = (uint_t)-1;
#endif
        size_t off;

        ASSERT(ISP2(aslr_max_stack_skew));

        if ((aslr_max_stack_skew == 0) ||
            !secflag_enabled(curproc, PROC_SEC_ASLR)) {
#ifdef sun4v
                uint_t spcolor = atomic_inc_32_nv(&sp_current_color);
                return ((size_t)((spcolor & sp_color_mask) *
                    SA(sp_color_stride)));
#else
                return (0);
#endif
        }

        (void) random_get_pseudo_bytes((uint8_t *)&off, sizeof (off));
        return (SA(P2PHASE(off, aslr_max_stack_skew)));
}

/*
 * Initialize a new user stack with the specified arguments and environment.
 * The initial user stack layout is as follows:
 *
 *      User Stack
 *      +---------------+
 *      |               |
 *      | stack guard   |
 *      | (64-bit only) |
 *      |               |
 *      +...............+ <--- stack limit (base - curproc->p_stk_ctl)
 *      .               .
 *      .               .
 *      .               .
 *      +---------------+ <--- curproc->p_usrstack
 *      |               |
 *      | slew          |
 *      |               |
 *      +---------------+
 *      | NULL          |
 *      +---------------+
 *      |               |
 *      | auxv strings  |
 *      |               |
 *      +---------------+
 *      |               |
 *      | envp strings  |
 *      |               |
 *      +---------------+
 *      |               |
 *      | argv strings  |
 *      |               |
 *      +---------------+ <--- ustrp
 *      |               |
 *      | aux vector    |
 *      |               |
 *      +---------------+ <--- auxv
 *      | NULL          |
 *      +---------------+
 *      | envp[envc-1]  |
 *      +---------------+
 *      | ...           |
 *      +---------------+
 *      | envp[0]       |
 *      +---------------+ <--- envp[]
 *      | NULL          |
 *      +---------------+
 *      | argv[argc-1]  |
 *      +---------------+
 *      | ...           |
 *      +---------------+
 *      | argv[0]       |
 *      +---------------+ <--- argv[]
 *      | argc          |
 *      +---------------+ <--- stack base
 *
 * In 64-bit processes, a stack guard segment is allocated at the address
 * immediately below where the stack limit ends.  This protects new library
 * mappings (such as the linker) from being placed in relatively dangerous
 * proximity to the stack.
 */
int
exec_args(execa_t *uap, uarg_t *args, intpdata_t *intp, void **auxvpp)
{
        size_t size;
        int error;
        proc_t *p = ttoproc(curthread);
        user_t *up = PTOU(p);
        char *usrstack;
        rctl_entity_p_t e;
        struct as *as;
        extern int use_stk_lpg;
        size_t sp_slew;
#if defined(_LP64)
        const size_t sg_sz = (stack_guard_seg_sz & PAGEMASK);
#endif /* defined(_LP64) */

        args->from_model = p->p_model;
        if (p->p_model == DATAMODEL_NATIVE) {
                args->from_ptrsize = sizeof (long);
        } else {
                args->from_ptrsize = sizeof (int32_t);
        }

        if (args->to_model == DATAMODEL_NATIVE) {
                args->to_ptrsize = sizeof (long);
                args->ncargs = NCARGS;
                args->stk_align = STACK_ALIGN;
                if (args->addr32)
                        usrstack = (char *)USRSTACK64_32;
                else
                        usrstack = (char *)USRSTACK;
        } else {
                args->to_ptrsize = sizeof (int32_t);
                args->ncargs = NCARGS32;
                args->stk_align = STACK_ALIGN32;
                usrstack = (char *)USRSTACK32;
        }

        ASSERT(P2PHASE((uintptr_t)usrstack, args->stk_align) == 0);


        for (size = PAGESIZE; ; size *= 2) {
                args->stk_size = size;
                args->stk_base = kmem_alloc(size, KM_SLEEP);
                args->stk_strp = args->stk_base;
                args->stk_offp = (int *)(args->stk_base + size);
                error = stk_copyin(uap, args, intp, auxvpp);
                if (error == 0)
                        break;
                kmem_free(args->stk_base, size);
                if (error != E2BIG && error != ENAMETOOLONG)
                        return (error);
                if (size >= args->ncargs)
                        return (E2BIG);
        }

        size = args->usrstack_size;

        ASSERT(error == 0);
        ASSERT(P2PHASE(size, args->stk_align) == 0);
        ASSERT((ssize_t)STK_AVAIL(args) >= 0);

        if (size > args->ncargs) {
                kmem_free(args->stk_base, args->stk_size);
                return (E2BIG);
        }

        /*
         * Leave only the current lwp and force the other lwps to exit.
         * If another lwp beat us to the punch by calling exit(), bail out.
         */
        if ((error = exitlwps(0)) != 0) {
                kmem_free(args->stk_base, args->stk_size);
                return (error);
        }

        /*
         * Revoke any doors created by the process.
         */
        if (p->p_door_list)
                door_exit();

        /*
         * Release schedctl data structures.
         */
        if (p->p_pagep)
                schedctl_proc_cleanup();

        /*
         * Clean up any DTrace helpers for the process.
         */
        if (p->p_dtrace_helpers != NULL) {
                ASSERT(dtrace_helpers_cleanup != NULL);
                (*dtrace_helpers_cleanup)(p);
        }

        mutex_enter(&p->p_lock);
        /*
         * Cleanup the DTrace provider associated with this process.
         */
        if (p->p_dtrace_probes) {
                ASSERT(dtrace_fasttrap_exec_ptr != NULL);
                dtrace_fasttrap_exec_ptr(p);
        }
        mutex_exit(&p->p_lock);

        /*
         * discard the lwpchan cache.
         */
        if (p->p_lcp != NULL)
                lwpchan_destroy_cache(1);

        /*
         * Delete the POSIX timers.
         */
        if (p->p_itimer != NULL)
                timer_exit();

        /*
         * Delete the ITIMER_REALPROF interval timer.
         * The other ITIMER_* interval timers are specified
         * to be inherited across exec().
         */
        delete_itimer_realprof();

        /*
         * Ensure that we don't change resource associations while we
         * change address spaces.
         */
        mutex_enter(&p->p_lock);
        pool_barrier_enter();
        mutex_exit(&p->p_lock);

        /*
         * Destroy the old address space and create a new one.
         * From here on, any errors are fatal to the exec()ing process.
         * On error we return -1, which means the caller must SIGKILL
         * the process.
         */
        relvm();

        mutex_enter(&p->p_lock);
        pool_barrier_exit();
        mutex_exit(&p->p_lock);

        up->u_execsw = args->execswp;

        p->p_brkbase = NULL;
        p->p_brksize = 0;
        p->p_brkpageszc = 0;
        p->p_stksize = 0;
        p->p_stkpageszc = 0;
        p->p_stkg_start = 0;
        p->p_stkg_end = 0;
        p->p_model = args->to_model;
        p->p_usrstack = usrstack;
        p->p_stkprot = args->stk_prot;
        p->p_datprot = args->dat_prot;

        /*
         * Reset resource controls such that all controls are again active as
         * well as appropriate to the potentially new address model for the
         * process.
         */
        e.rcep_p.proc = p;
        e.rcep_t = RCENTITY_PROCESS;
        rctl_set_reset(p->p_rctls, p, &e);

        /* Too early to call map_pgsz for the heap */
        if (use_stk_lpg) {
                p->p_stkpageszc = page_szc(map_pgsz(MAPPGSZ_STK, p, 0, 0, 0));
        }

        mutex_enter(&p->p_lock);
        p->p_flag |= SAUTOLPG;  /* kernel controls page sizes */
        mutex_exit(&p->p_lock);

        sp_slew = exec_get_spslew();
        ASSERT(P2PHASE(sp_slew, args->stk_align) == 0);
        /* Be certain we don't underflow */
        VERIFY((curproc->p_usrstack - (size + sp_slew)) < curproc->p_usrstack);
        exec_set_sp(size + sp_slew);

        as = as_alloc();
        p->p_as = as;
        as->a_proc = p;
        if (p->p_model == DATAMODEL_ILP32 || args->addr32)
                as->a_userlimit = (caddr_t)USERLIMIT32;
        (void) hat_setup(as->a_hat, HAT_ALLOC);
        hat_join_srd(as->a_hat, args->ex_vp);

        /* Write out the contents of the new stack. */
        error = stk_copyout(args, usrstack - sp_slew, auxvpp, up);
        kmem_free(args->stk_base, args->stk_size);

#if defined(_LP64)
        /* Add stack guard segment (if needed) after successful copyout */
        if (error == 0 && p->p_model == DATAMODEL_LP64 && sg_sz != 0) {
                seghole_crargs_t sca;
                caddr_t addr_end = (caddr_t)(((uintptr_t)usrstack -
                    p->p_stk_ctl) & PAGEMASK);
                caddr_t addr_start = addr_end - sg_sz;

                DTRACE_PROBE4(stack__guard__chk, proc_t *, p,
                    caddr_t, addr_start, caddr_t, addr_end, size_t, sg_sz);

                if (addr_end >= usrstack || addr_start >= addr_end ||
                    valid_usr_range(addr_start, sg_sz, PROT_NONE, as,
                    as->a_userlimit) != RANGE_OKAY) {
                        return (E2BIG);
                }

                /* Create un-mappable area in AS with seg_hole */
                sca.name = "stack_guard";
                error = as_map(as, addr_start, sg_sz, seghole_create, &sca);
                if (error == 0) {
                        p->p_stkg_start = (uintptr_t)addr_start;
                        p->p_stkg_end = (uintptr_t)addr_start + sg_sz;
                }
        }
#endif /* defined(_LP64) */

        return (error);
}