[dragonfly.git] / sys / emulation / linux / i386 / linux_sysvec.c

/*-
 * Copyright (c) 1994-1996 Søren Schmidt
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer 
 *    in this position and unchanged.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software withough specific prior written permission
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $FreeBSD: src/sys/i386/linux/linux_sysvec.c,v 1.55.2.9 2002/01/12 11:03:30 bde Exp $
 * $DragonFly: src/sys/emulation/linux/i386/linux_sysvec.c,v 1.31 2008/04/21 15:47:53 dillon Exp $
 */

/* XXX we use functions that might not exist. */
#include "opt_compat.h"

#ifndef COMPAT_43
#error "Unable to compile Linux-emulator due to missing COMPAT_43 option!"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/imgact.h>
#include <sys/imgact_aout.h>
#include <sys/imgact_elf.h>
#include <sys/kern_syscall.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/signalvar.h>
#include <sys/sysent.h>
#include <sys/sysproto.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_page.h>
#include <vm/vm_extern.h>
#include <sys/exec.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <machine/cpu.h>

#include "linux.h"
#include "linux_proto.h"
#include "../linux_signal.h"
#include "../linux_util.h"

MODULE_VERSION(linux, 1);

MALLOC_DEFINE(M_LINUX, "linux", "Linux mode structures");

#if BYTE_ORDER == LITTLE_ENDIAN
#define SHELLMAGIC      0x2123 /* #! */
#else
#define SHELLMAGIC      0x2321
#endif

/*
 * Allow the sendsig functions to use the ldebug() facility
 * even though they are not syscalls themselves. Map them
 * to syscall 0. This is slightly less bogus than using
 * ldebug(sigreturn).
 */
#define LINUX_SYS_linux_rt_sendsig      0
#define LINUX_SYS_linux_sendsig         0

extern char linux_sigcode[];
extern int linux_szsigcode;

extern struct sysent linux_sysent[LINUX_SYS_MAXSYSCALL];

static int      linux_fixup (register_t **stack_base,
                                 struct image_params *iparams);
static int      elf_linux_fixup (register_t **stack_base,
                                     struct image_params *iparams);
static void     linux_prepsyscall (struct trapframe *tf, int *args,
                                       u_int *code, caddr_t *params);
static void     linux_sendsig (sig_t catcher, int sig, sigset_t *mask,
                                   u_long code);

/*
 * Linux syscalls return negative errno's, we do positive and map them
 */
static int bsd_to_linux_errno[ELAST + 1] = {
        -0,  -1,  -2,  -3,  -4,  -5,  -6,  -7,  -8,  -9,
        -10, -35, -12, -13, -14, -15, -16, -17, -18, -19,
        -20, -21, -22, -23, -24, -25, -26, -27, -28, -29,
        -30, -31, -32, -33, -34, -11,-115,-114, -88, -89,
        -90, -91, -92, -93, -94, -95, -96, -97, -98, -99,
        -100,-101,-102,-103,-104,-105,-106,-107,-108,-109,
        -110,-111, -40, -36,-112,-113, -39, -11, -87,-122,
        -116, -66,  -6,  -6,  -6,  -6,  -6, -37, -38,  -9,
        -6, -6, -43, -42, -75, -6, -84
};

int bsd_to_linux_signal[LINUX_SIGTBLSZ] = {
        LINUX_SIGHUP, LINUX_SIGINT, LINUX_SIGQUIT, LINUX_SIGILL,
        LINUX_SIGTRAP, LINUX_SIGABRT, 0, LINUX_SIGFPE,
        LINUX_SIGKILL, LINUX_SIGBUS, LINUX_SIGSEGV, 0,
        LINUX_SIGPIPE, LINUX_SIGALRM, LINUX_SIGTERM, LINUX_SIGURG,
        LINUX_SIGSTOP, LINUX_SIGTSTP, LINUX_SIGCONT, LINUX_SIGCHLD,
        LINUX_SIGTTIN, LINUX_SIGTTOU, LINUX_SIGIO, LINUX_SIGXCPU,
        LINUX_SIGXFSZ, LINUX_SIGVTALRM, LINUX_SIGPROF, LINUX_SIGWINCH,
        0, LINUX_SIGUSR1, LINUX_SIGUSR2
};

int linux_to_bsd_signal[LINUX_SIGTBLSZ] = {
        SIGHUP, SIGINT, SIGQUIT, SIGILL,
        SIGTRAP, SIGABRT, SIGBUS, SIGFPE,
        SIGKILL, SIGUSR1, SIGSEGV, SIGUSR2,
        SIGPIPE, SIGALRM, SIGTERM, SIGBUS,
        SIGCHLD, SIGCONT, SIGSTOP, SIGTSTP,
        SIGTTIN, SIGTTOU, SIGURG, SIGXCPU,
        SIGXFSZ, SIGVTALRM, SIGPROF, SIGWINCH,
        SIGIO, SIGURG, 0
};

#define LINUX_T_UNKNOWN  255
static int _bsd_to_linux_trapcode[] = {
        LINUX_T_UNKNOWN,        /* 0 */
        6,                      /* 1  T_PRIVINFLT */
        LINUX_T_UNKNOWN,        /* 2 */
        3,                      /* 3  T_BPTFLT */
        LINUX_T_UNKNOWN,        /* 4 */
        LINUX_T_UNKNOWN,        /* 5 */
        16,                     /* 6  T_ARITHTRAP */
        254,                    /* 7  T_ASTFLT */
        LINUX_T_UNKNOWN,        /* 8 */
        13,                     /* 9  T_PROTFLT */
        1,                      /* 10 T_TRCTRAP */
        LINUX_T_UNKNOWN,        /* 11 */
        14,                     /* 12 T_PAGEFLT */
        LINUX_T_UNKNOWN,        /* 13 */
        17,                     /* 14 T_ALIGNFLT */
        LINUX_T_UNKNOWN,        /* 15 */
        LINUX_T_UNKNOWN,        /* 16 */
        LINUX_T_UNKNOWN,        /* 17 */
        0,                      /* 18 T_DIVIDE */
        2,                      /* 19 T_NMI */
        4,                      /* 20 T_OFLOW */
        5,                      /* 21 T_BOUND */
        7,                      /* 22 T_DNA */
        8,                      /* 23 T_DOUBLEFLT */
        9,                      /* 24 T_FPOPFLT */
        10,                     /* 25 T_TSSFLT */
        11,                     /* 26 T_SEGNPFLT */
        12,                     /* 27 T_STKFLT */
        18,                     /* 28 T_MCHK */
        19,                     /* 29 T_XMMFLT */
        15                      /* 30 T_RESERVED */
};
#define bsd_to_linux_trapcode(code) \
    ((code)<sizeof(_bsd_to_linux_trapcode)/sizeof(*_bsd_to_linux_trapcode)? \
     _bsd_to_linux_trapcode[(code)]: \
     LINUX_T_UNKNOWN)

/*
 * If FreeBSD & Linux have a difference of opinion about what a trap
 * means, deal with it here.
 */
static int
translate_traps(int signal, int trap_code)
{
        if (signal != SIGBUS)
                return signal;
        switch (trap_code) {
        case T_PROTFLT:
        case T_TSSFLT:
        case T_DOUBLEFLT:
        case T_PAGEFLT:
                return SIGSEGV;
        default:
                return signal;
        }
}

static int
linux_fixup(register_t **stack_base, struct image_params *imgp)
{
        register_t *argv, *envp;

        argv = *stack_base;
        envp = *stack_base + (imgp->args->argc + 1);
        (*stack_base)--;
        **stack_base = (intptr_t)(void *)envp;
        (*stack_base)--;
        **stack_base = (intptr_t)(void *)argv;
        (*stack_base)--;
        **stack_base = imgp->args->argc;
        return 0;
}

static int
elf_linux_fixup(register_t **stack_base, struct image_params *imgp)
{
        Elf32_Auxargs *args = (Elf32_Auxargs *)imgp->auxargs;
        register_t *pos;
             
        pos = *stack_base + (imgp->args->argc + imgp->args->envc + 2);  
    
        if (args->trace) {
                AUXARGS_ENTRY(pos, AT_DEBUG, 1);
        }
        if (args->execfd != -1) {
                AUXARGS_ENTRY(pos, AT_EXECFD, args->execfd);
        }       
        AUXARGS_ENTRY(pos, AT_PHDR, args->phdr);
        AUXARGS_ENTRY(pos, AT_PHENT, args->phent);
        AUXARGS_ENTRY(pos, AT_PHNUM, args->phnum);
        AUXARGS_ENTRY(pos, AT_PAGESZ, args->pagesz);
        AUXARGS_ENTRY(pos, AT_FLAGS, args->flags);
        AUXARGS_ENTRY(pos, AT_ENTRY, args->entry);
        AUXARGS_ENTRY(pos, AT_BASE, args->base);
        AUXARGS_ENTRY(pos, AT_UID, imgp->proc->p_ucred->cr_ruid);
        AUXARGS_ENTRY(pos, AT_EUID, imgp->proc->p_ucred->cr_svuid);
        AUXARGS_ENTRY(pos, AT_GID, imgp->proc->p_ucred->cr_rgid);
        AUXARGS_ENTRY(pos, AT_EGID, imgp->proc->p_ucred->cr_svgid);
        AUXARGS_ENTRY(pos, AT_NULL, 0);
        
        kfree(imgp->auxargs, M_TEMP);      
        imgp->auxargs = NULL;

        (*stack_base)--;
        **stack_base = (long)imgp->args->argc;
        return 0;
}

extern int _ucodesel, _udatasel;
extern unsigned long linux_sznonrtsigcode;

static void
linux_rt_sendsig(sig_t catcher, int sig, sigset_t *mask, u_long code)
{
        struct proc *p = curproc;
        struct lwp *lp = curthread->td_lwp;
        struct trapframe *regs;
        struct l_rt_sigframe *fp, frame;
        int oonstack;

        regs = lp->lwp_md.md_regs;
        oonstack = lp->lwp_sigstk.ss_flags & SS_ONSTACK;

#ifdef DEBUG
        if (ldebug(rt_sendsig))
                kprintf(ARGS(rt_sendsig, "%p, %d, %p, %lu"),
                    catcher, sig, (void*)mask, code);
#endif
        /*
         * Allocate space for the signal handler context.
         */
        if ((lp->lwp_flag & LWP_ALTSTACK) && !oonstack &&
            SIGISMEMBER(p->p_sigacts->ps_sigonstack, sig)) {
                fp = (struct l_rt_sigframe *)(lp->lwp_sigstk.ss_sp +
                    lp->lwp_sigstk.ss_size - sizeof(struct l_rt_sigframe));
                lp->lwp_sigstk.ss_flags |= SS_ONSTACK;
        } else
                fp = (struct l_rt_sigframe *)regs->tf_esp - 1;

        /*
         * grow() will return FALSE if the fp will not fit inside the stack
         *      and the stack can not be grown. useracc will return FALSE
         *      if access is denied.
         */
        if ((vm_map_growstack(p, (vm_offset_t)fp) != KERN_SUCCESS) ||
            !useracc((caddr_t)fp, sizeof (struct l_rt_sigframe), 
            VM_PROT_WRITE)) {
                /*
                 * Process has trashed its stack; give it an illegal
                 * instruction to halt it in its tracks.
                 */
                SIGACTION(p, SIGILL) = SIG_DFL;
                SIGDELSET(p->p_sigignore, SIGILL);
                SIGDELSET(p->p_sigcatch, SIGILL);
                SIGDELSET(lp->lwp_sigmask, SIGILL);
#ifdef DEBUG
                if (ldebug(rt_sendsig))
                        kprintf(LMSG("rt_sendsig: bad stack %p, oonstack=%x"),
                            fp, oonstack);
#endif
                lwpsignal(p, lp, SIGILL);
                return;
        }

        /*
         * Build the argument list for the signal handler.
         */
        if (p->p_sysent->sv_sigtbl)
                if (sig <= p->p_sysent->sv_sigsize)
                        sig = p->p_sysent->sv_sigtbl[_SIG_IDX(sig)];

        frame.sf_handler = catcher;
        frame.sf_sig = sig;
        frame.sf_siginfo = &fp->sf_si;
        frame.sf_ucontext = &fp->sf_sc;

        /* Fill siginfo structure. */
        frame.sf_si.lsi_signo = sig;
        frame.sf_si.lsi_code = code;
        frame.sf_si.lsi_addr = (void *)regs->tf_err;

        /*
         * Build the signal context to be used by sigreturn.
         */
        frame.sf_sc.uc_flags = 0;               /* XXX ??? */
        frame.sf_sc.uc_link = NULL;             /* XXX ??? */

        frame.sf_sc.uc_stack.ss_sp = lp->lwp_sigstk.ss_sp;
        frame.sf_sc.uc_stack.ss_size = lp->lwp_sigstk.ss_size;
        frame.sf_sc.uc_stack.ss_flags = (lp->lwp_flag & LWP_ALTSTACK)
            ? ((oonstack) ? LINUX_SS_ONSTACK : 0) : LINUX_SS_DISABLE;

        bsd_to_linux_sigset(mask, &frame.sf_sc.uc_sigmask);

        frame.sf_sc.uc_mcontext.sc_mask   = frame.sf_sc.uc_sigmask.__bits[0];
        frame.sf_sc.uc_mcontext.sc_gs     = regs->tf_gs;
        frame.sf_sc.uc_mcontext.sc_fs     = regs->tf_fs;
        frame.sf_sc.uc_mcontext.sc_es     = regs->tf_es;
        frame.sf_sc.uc_mcontext.sc_ds     = regs->tf_ds;
        frame.sf_sc.uc_mcontext.sc_edi    = regs->tf_edi;
        frame.sf_sc.uc_mcontext.sc_esi    = regs->tf_esi;
        frame.sf_sc.uc_mcontext.sc_ebp    = regs->tf_ebp;
        frame.sf_sc.uc_mcontext.sc_ebx    = regs->tf_ebx;
        frame.sf_sc.uc_mcontext.sc_edx    = regs->tf_edx;
        frame.sf_sc.uc_mcontext.sc_ecx    = regs->tf_ecx;
        frame.sf_sc.uc_mcontext.sc_eax    = regs->tf_eax;
        frame.sf_sc.uc_mcontext.sc_eip    = regs->tf_eip;
        frame.sf_sc.uc_mcontext.sc_cs     = regs->tf_cs;
        frame.sf_sc.uc_mcontext.sc_eflags = regs->tf_eflags;
        frame.sf_sc.uc_mcontext.sc_esp_at_signal = regs->tf_esp;
        frame.sf_sc.uc_mcontext.sc_ss     = regs->tf_ss;
        frame.sf_sc.uc_mcontext.sc_err    = regs->tf_err;
        frame.sf_sc.uc_mcontext.sc_trapno = bsd_to_linux_trapcode(code);

#ifdef DEBUG
        if (ldebug(rt_sendsig))
                kprintf(LMSG("rt_sendsig flags: 0x%x, sp: %p, ss: 0x%x, mask: 0x%x"),
                    frame.sf_sc.uc_stack.ss_flags, lp->lwp_sigstk.ss_sp,
                    lp->lwp_sigstk.ss_size, frame.sf_sc.uc_mcontext.sc_mask);
#endif

        if (copyout(&frame, fp, sizeof(frame)) != 0) {
                /*
                 * Process has trashed its stack; give it an illegal
                 * instruction to halt it in its tracks.
                 */
                sigexit(lp, SIGILL);
                /* NOTREACHED */
        }

        /*
         * Build context to run handler in.
         */
        regs->tf_esp = (int)fp;
        regs->tf_eip = PS_STRINGS - *(p->p_sysent->sv_szsigcode) + 
            linux_sznonrtsigcode;

        /*
         * i386 abi specifies that the direction flag must be cleared
         * on function entry
         */
        regs->tf_eflags &= ~(PSL_T | PSL_VM | PSL_D);

        regs->tf_cs = _ucodesel;
        regs->tf_ds = _udatasel;
        regs->tf_es = _udatasel;
        /* allow %fs and %gs to be inherited by the signal handler */
        /*
        regs->tf_fs = _udatasel;
        regs->tf_gs = _udatasel;
        */
        regs->tf_ss = _udatasel;
}


/*
 * Send an interrupt to process.
 *
 * Stack is set up to allow sigcode stored
 * in u. to call routine, followed by kcall
 * to sigreturn routine below.  After sigreturn
 * resets the signal mask, the stack, and the
 * frame pointer, it returns to the user
 * specified pc, psl.
 */

static void
linux_sendsig(sig_t catcher, int sig, sigset_t *mask, u_long code)
{
        struct proc *p = curproc;
        struct lwp *lp = curthread->td_lwp;
        struct trapframe *regs;
        struct l_sigframe *fp, frame;
        l_sigset_t lmask;
        int oonstack, i;

        if (SIGISMEMBER(p->p_sigacts->ps_siginfo, sig)) {
                /* Signal handler installed with SA_SIGINFO. */
                linux_rt_sendsig(catcher, sig, mask, code);
                return;
        }

        regs = lp->lwp_md.md_regs;
        oonstack = lp->lwp_sigstk.ss_flags & SS_ONSTACK;

#ifdef DEBUG
        if (ldebug(sendsig))
                kprintf(ARGS(sendsig, "%p, %d, %p, %lu"),
                    catcher, sig, (void*)mask, code);
#endif

        /*
         * Allocate space for the signal handler context.
         */
        if ((lp->lwp_flag & LWP_ALTSTACK) && !oonstack &&
            SIGISMEMBER(p->p_sigacts->ps_sigonstack, sig)) {
                fp = (struct l_sigframe *)(lp->lwp_sigstk.ss_sp +
                    lp->lwp_sigstk.ss_size - sizeof(struct l_sigframe));
                lp->lwp_sigstk.ss_flags |= SS_ONSTACK;
        } else
                fp = (struct l_sigframe *)regs->tf_esp - 1;

        /*
         * grow() will return FALSE if the fp will not fit inside the stack
         *      and the stack can not be grown. useracc will return FALSE
         *      if access is denied.
         */
        if ((vm_map_growstack(p, (vm_offset_t)fp) != KERN_SUCCESS) ||
            !useracc((caddr_t)fp, sizeof (struct l_sigframe), 
            VM_PROT_WRITE)) {
                /*
                 * Process has trashed its stack; give it an illegal
                 * instruction to halt it in its tracks.
                 */
                SIGACTION(p, SIGILL) = SIG_DFL;
                SIGDELSET(p->p_sigignore, SIGILL);
                SIGDELSET(p->p_sigcatch, SIGILL);
                SIGDELSET(lp->lwp_sigmask, SIGILL);
                lwpsignal(p, lp, SIGILL);
                return;
        }

        /*
         * Build the argument list for the signal handler.
         */
        if (p->p_sysent->sv_sigtbl)
                if (sig <= p->p_sysent->sv_sigsize)
                        sig = p->p_sysent->sv_sigtbl[_SIG_IDX(sig)];

        frame.sf_handler = catcher;
        frame.sf_sig = sig;

        bsd_to_linux_sigset(mask, &lmask);

        /*
         * Build the signal context to be used by sigreturn.
         */
        frame.sf_sc.sc_mask   = lmask.__bits[0];
        frame.sf_sc.sc_gs     = regs->tf_gs;
        frame.sf_sc.sc_fs     = regs->tf_fs;
        frame.sf_sc.sc_es     = regs->tf_es;
        frame.sf_sc.sc_ds     = regs->tf_ds;
        frame.sf_sc.sc_edi    = regs->tf_edi;
        frame.sf_sc.sc_esi    = regs->tf_esi;
        frame.sf_sc.sc_ebp    = regs->tf_ebp;
        frame.sf_sc.sc_ebx    = regs->tf_ebx;
        frame.sf_sc.sc_edx    = regs->tf_edx;
        frame.sf_sc.sc_ecx    = regs->tf_ecx;
        frame.sf_sc.sc_eax    = regs->tf_eax;
        frame.sf_sc.sc_eip    = regs->tf_eip;
        frame.sf_sc.sc_cs     = regs->tf_cs;
        frame.sf_sc.sc_eflags = regs->tf_eflags;
        frame.sf_sc.sc_esp_at_signal = regs->tf_esp;
        frame.sf_sc.sc_ss     = regs->tf_ss;
        frame.sf_sc.sc_err    = regs->tf_err;
        frame.sf_sc.sc_trapno = bsd_to_linux_trapcode(code);

        bzero(&frame.sf_fpstate, sizeof(struct l_fpstate));

        for (i = 0; i < (LINUX_NSIG_WORDS-1); i++)
                frame.sf_extramask[i] = lmask.__bits[i+1];

        if (copyout(&frame, fp, sizeof(frame)) != 0) {
                /*
                 * Process has trashed its stack; give it an illegal
                 * instruction to halt it in its tracks.
                 */
                sigexit(lp, SIGILL);
                /* NOTREACHED */
        }

        /*
         * Build context to run handler in.
         */
        regs->tf_esp = (int)fp;
        regs->tf_eip = PS_STRINGS - *(p->p_sysent->sv_szsigcode);

        /*
         * i386 abi specifies that the direction flag must be cleared
         * on function entry
         */
        regs->tf_eflags &= ~(PSL_T | PSL_VM | PSL_D);

        regs->tf_cs = _ucodesel;
        regs->tf_ds = _udatasel;
        regs->tf_es = _udatasel;
        /* Allow %fs and %gs to be inherited by the signal handler */
        /*
        regs->tf_fs = _udatasel;
        regs->tf_gs = _udatasel;
        */
        regs->tf_ss = _udatasel;
}

/*
 * System call to cleanup state after a signal
 * has been taken.  Reset signal mask and
 * stack state from context left by sendsig (above).
 * Return to previous pc and psl as specified by
 * context left by sendsig. Check carefully to
 * make sure that the user has not modified the
 * psl to gain improper privileges or to cause
 * a machine fault.
 *
 * MPSAFE
 */
int
sys_linux_sigreturn(struct linux_sigreturn_args *args)
{
        struct lwp *lp = curthread->td_lwp;
        struct l_sigframe frame;
        struct trapframe *regs;
        l_sigset_t lmask;
        int eflags, i;

        regs = lp->lwp_md.md_regs;

#ifdef DEBUG
        if (ldebug(sigreturn))
                kprintf(ARGS(sigreturn, "%p"), (void *)args->sfp);
#endif
        /*
         * The trampoline code hands us the sigframe.
         * It is unsafe to keep track of it ourselves, in the event that a
         * program jumps out of a signal handler.
         */
        if (copyin((caddr_t)args->sfp, &frame, sizeof(frame)) != 0)
                return (EFAULT);

        /*
         * Check for security violations.
         */
#define EFLAGS_SECURE(ef, oef)  ((((ef) ^ (oef)) & ~PSL_USERCHANGE) == 0)
        eflags = frame.sf_sc.sc_eflags;
        /*
         * XXX do allow users to change the privileged flag PSL_RF.  The
         * cpu sets PSL_RF in tf_eflags for faults.  Debuggers should
         * sometimes set it there too.  tf_eflags is kept in the signal
         * context during signal handling and there is no other place
         * to remember it, so the PSL_RF bit may be corrupted by the
         * signal handler without us knowing.  Corruption of the PSL_RF
         * bit at worst causes one more or one less debugger trap, so
         * allowing it is fairly harmless.
         */
        if (!EFLAGS_SECURE(eflags & ~PSL_RF, regs->tf_eflags & ~PSL_RF)) {
                return(EINVAL);
        }

        /*
         * Don't allow users to load a valid privileged %cs.  Let the
         * hardware check for invalid selectors, excess privilege in
         * other selectors, invalid %eip's and invalid %esp's.
         */
#define CS_SECURE(cs)   (ISPL(cs) == SEL_UPL)
        if (!CS_SECURE(frame.sf_sc.sc_cs)) {
                trapsignal(lp, SIGBUS, T_PROTFLT);
                return(EINVAL);
        }

        lp->lwp_sigstk.ss_flags &= ~SS_ONSTACK;
        lmask.__bits[0] = frame.sf_sc.sc_mask;
        for (i = 0; i < (LINUX_NSIG_WORDS-1); i++)
                lmask.__bits[i+1] = frame.sf_extramask[i];
        linux_to_bsd_sigset(&lmask, &lp->lwp_sigmask);
        SIG_CANTMASK(lp->lwp_sigmask);

        /*
         * Restore signal context.
         */
        /* %gs was restored by the trampoline. */
        regs->tf_fs     = frame.sf_sc.sc_fs;
        regs->tf_es     = frame.sf_sc.sc_es;
        regs->tf_ds     = frame.sf_sc.sc_ds;
        regs->tf_edi    = frame.sf_sc.sc_edi;
        regs->tf_esi    = frame.sf_sc.sc_esi;
        regs->tf_ebp    = frame.sf_sc.sc_ebp;
        regs->tf_ebx    = frame.sf_sc.sc_ebx;
        regs->tf_edx    = frame.sf_sc.sc_edx;
        regs->tf_ecx    = frame.sf_sc.sc_ecx;
        regs->tf_eax    = frame.sf_sc.sc_eax;
        regs->tf_eip    = frame.sf_sc.sc_eip;
        regs->tf_cs     = frame.sf_sc.sc_cs;
        regs->tf_eflags = eflags;
        regs->tf_esp    = frame.sf_sc.sc_esp_at_signal;
        regs->tf_ss     = frame.sf_sc.sc_ss;

        return (EJUSTRETURN);
}

/*
 * System call to cleanup state after a signal
 * has been taken.  Reset signal mask and
 * stack state from context left by rt_sendsig (above).
 * Return to previous pc and psl as specified by
 * context left by sendsig. Check carefully to
 * make sure that the user has not modified the
 * psl to gain improper privileges or to cause
 * a machine fault.
 *
 * MPSAFE
 */
int
sys_linux_rt_sigreturn(struct linux_rt_sigreturn_args *args)
{
        struct lwp *lp = curthread->td_lwp;
        struct l_ucontext uc;
        struct l_sigcontext *context;
        l_stack_t *lss;
        stack_t ss;
        struct trapframe *regs;
        int eflags;

        regs = lp->lwp_md.md_regs;

#ifdef DEBUG
        if (ldebug(rt_sigreturn))
                kprintf(ARGS(rt_sigreturn, "%p"), (void *)args->ucp);
#endif
        /*
         * The trampoline code hands us the ucontext.
         * It is unsafe to keep track of it ourselves, in the event that a
         * program jumps out of a signal handler.
         */
        if (copyin((caddr_t)args->ucp, &uc, sizeof(uc)) != 0)
                return (EFAULT);

        context = &uc.uc_mcontext;

        /*
         * Check for security violations.
         */
#define EFLAGS_SECURE(ef, oef)  ((((ef) ^ (oef)) & ~PSL_USERCHANGE) == 0)
        eflags = context->sc_eflags;
        /*
         * XXX do allow users to change the privileged flag PSL_RF.  The
         * cpu sets PSL_RF in tf_eflags for faults.  Debuggers should
         * sometimes set it there too.  tf_eflags is kept in the signal
         * context during signal handling and there is no other place
         * to remember it, so the PSL_RF bit may be corrupted by the
         * signal handler without us knowing.  Corruption of the PSL_RF
         * bit at worst causes one more or one less debugger trap, so
         * allowing it is fairly harmless.
         */
        if (!EFLAGS_SECURE(eflags & ~PSL_RF, regs->tf_eflags & ~PSL_RF)) {
                return(EINVAL);
        }

        /*
         * Don't allow users to load a valid privileged %cs.  Let the
         * hardware check for invalid selectors, excess privilege in
         * other selectors, invalid %eip's and invalid %esp's.
         */
#define CS_SECURE(cs)   (ISPL(cs) == SEL_UPL)
        if (!CS_SECURE(context->sc_cs)) {
                trapsignal(lp, SIGBUS, T_PROTFLT);
                return(EINVAL);
        }

        lp->lwp_sigstk.ss_flags &= ~SS_ONSTACK;
        linux_to_bsd_sigset(&uc.uc_sigmask, &lp->lwp_sigmask);
        SIG_CANTMASK(lp->lwp_sigmask);

        /*
         * Restore signal context
         */
        /* %gs was restored by the trampoline. */
        regs->tf_fs     = context->sc_fs;
        regs->tf_es     = context->sc_es;
        regs->tf_ds     = context->sc_ds;
        regs->tf_edi    = context->sc_edi;
        regs->tf_esi    = context->sc_esi;
        regs->tf_ebp    = context->sc_ebp;
        regs->tf_ebx    = context->sc_ebx;
        regs->tf_edx    = context->sc_edx;
        regs->tf_ecx    = context->sc_ecx;
        regs->tf_eax    = context->sc_eax;
        regs->tf_eip    = context->sc_eip;
        regs->tf_cs     = context->sc_cs;
        regs->tf_eflags = eflags;
        regs->tf_esp    = context->sc_esp_at_signal;
        regs->tf_ss     = context->sc_ss;

        /*
         * call sigaltstack & ignore results..
         */
        lss = &uc.uc_stack;
        ss.ss_sp = lss->ss_sp;
        ss.ss_size = lss->ss_size;
        ss.ss_flags = linux_to_bsd_sigaltstack(lss->ss_flags);

#ifdef DEBUG
        if (ldebug(rt_sigreturn))
                kprintf(LMSG("rt_sigret flags: 0x%x, sp: %p, ss: 0x%x, mask: 0x%x"),
                    ss.ss_flags, ss.ss_sp, ss.ss_size, context->sc_mask);
#endif
        kern_sigaltstack(&ss, NULL);

        return (EJUSTRETURN);
}

/*
 * Prep arguments.
 *
 * MUST BE MPSAFE
 */
static void
linux_prepsyscall(struct trapframe *tf, int *args, u_int *code, caddr_t *params)
{
        args[0] = tf->tf_ebx;
        args[1] = tf->tf_ecx;
        args[2] = tf->tf_edx;
        args[3] = tf->tf_esi;
        args[4] = tf->tf_edi;
        args[5] = tf->tf_ebp;
        *params = NULL;         /* no copyin */
}

/*
 * If a linux binary is exec'ing something, try this image activator 
 * first.  We override standard shell script execution in order to
 * be able to modify the interpreter path.  We only do this if a linux
 * binary is doing the exec, so we do not create an EXEC module for it.
 */
static int      exec_linux_imgact_try (struct image_params *iparams);

static int
exec_linux_imgact_try(struct image_params *imgp)
{
    const char *head = (const char *)imgp->image_header;
    int error = -1;

    /*
     * The interpreter for shell scripts run from a linux binary needs
     * to be located in /compat/linux if possible in order to recursively
     * maintain linux path emulation.
     */
    if (((const short *)head)[0] == SHELLMAGIC) {
            /*
             * Run our normal shell image activator.  If it succeeds attempt
             * to use the alternate path for the interpreter.  If an alternate
             * path is found, use our stringspace to store it.
             */
            if ((error = exec_shell_imgact(imgp)) == 0) {
                    linux_translate_path(imgp->interpreter_name,
                        MAXSHELLCMDLEN);
            }
    }
    return(error);
}

struct sysentvec linux_sysvec = {
        LINUX_SYS_MAXSYSCALL,
        linux_sysent,
        0xff,
        LINUX_SIGTBLSZ,
        bsd_to_linux_signal,
        ELAST + 1, 
        bsd_to_linux_errno,
        translate_traps,
        linux_fixup,
        linux_sendsig,
        linux_sigcode,  
        &linux_szsigcode,
        linux_prepsyscall,
        "Linux a.out",
        NULL,
        exec_linux_imgact_try,
        LINUX_MINSIGSTKSZ
};

struct sysentvec elf_linux_sysvec = {
        LINUX_SYS_MAXSYSCALL,
        linux_sysent,
        0xff,
        LINUX_SIGTBLSZ,
        bsd_to_linux_signal,
        ELAST + 1,
        bsd_to_linux_errno,
        translate_traps,
        elf_linux_fixup,
        linux_sendsig,
        linux_sigcode,
        &linux_szsigcode,
        linux_prepsyscall,
        "Linux ELF",
        elf_coredump,
        exec_linux_imgact_try,
        LINUX_MINSIGSTKSZ
};

static int      linux_match_abi_note(const Elf_Note *abi_note);
static int      linux_match_suse_note(const Elf_Note *abi_note);

static Elf32_Brandinfo linux_brand = {
                                        ELFOSABI_LINUX,
                                        "Linux",
                                        linux_match_abi_note,
                                        "/compat/linux",
                                        "/lib/ld-linux.so.1",
                                        &elf_linux_sysvec
                                 };

static Elf32_Brandinfo linux_glibc2brand = {
                                        ELFOSABI_LINUX,
                                        "Linux",
                                        linux_match_abi_note,
                                        "/compat/linux",
                                        "/lib/ld-linux.so.2",
                                        &elf_linux_sysvec
                                 };

static Elf32_Brandinfo linux_suse_brand = {
                                        ELFOSABI_LINUX,
                                        "Linux",
                                        linux_match_suse_note,
                                        "/compat/linux",
                                        "/lib/ld-linux.so.2",
                                        &elf_linux_sysvec
                                 };

Elf32_Brandinfo *linux_brandlist[] = {
                                        &linux_brand,
                                        &linux_glibc2brand,
                                        &linux_suse_brand,
                                        NULL
                                };

static int
linux_match_abi_note(const Elf_Note *abi_note)
{
        const char *abi_name = (const char *)
            ((const uint8_t *)abi_note + sizeof(*abi_note));
        const uint32_t *descr = (const uint32_t *)
            ((const uint8_t *)abi_name + abi_note->n_namesz);

        if (abi_note->n_namesz != sizeof("GNU"))
                return(FALSE);
        if (memcmp(abi_name, "GNU", sizeof("GNU")))
                return(FALSE);
        if (abi_note->n_descsz < sizeof(uint32_t))
                return(FALSE);

        if (*descr != 0)
                return(FALSE);
        return(TRUE);
}

static int
linux_match_suse_note(const Elf_Note *abi_note)
{
        const char *abi_name = (const char *)
            ((const uint8_t *)abi_note + sizeof(*abi_note));

        if (abi_note->n_namesz != sizeof("SuSE"))
                return(FALSE);
        if (memcmp(abi_name, "SuSE", sizeof("SuSE")))
                return(FALSE);

        return(TRUE);
}

static int
linux_elf_modevent(module_t mod, int type, void *data)
{
        Elf32_Brandinfo **brandinfo;
        int error;

        error = 0;

        switch(type) {
        case MOD_LOAD:
                for (brandinfo = &linux_brandlist[0]; *brandinfo != NULL;
                     ++brandinfo)
                        if (elf_insert_brand_entry(*brandinfo) < 0)
                                error = EINVAL;
                if (error == 0) {
                        if (bootverbose)
                                kprintf("Linux ELF exec handler installed\n");
                } else
                        kprintf("cannot insert Linux ELF brand handler\n");
                break;
        case MOD_UNLOAD:
                for (brandinfo = &linux_brandlist[0]; *brandinfo != NULL;
                     ++brandinfo)
                        if (elf_brand_inuse(*brandinfo))
                                error = EBUSY;
                if (error == 0) {
                        for (brandinfo = &linux_brandlist[0];
                             *brandinfo != NULL; ++brandinfo)
                                if (elf_remove_brand_entry(*brandinfo) < 0)
                                        error = EINVAL;
                }
                if (error == 0) {
                        if (bootverbose)
                                kprintf("Linux ELF exec handler removed\n");
                } else
                        kprintf("Could not deinstall ELF interpreter entry\n");
                break;
        default:
                break;
        }
        return error;
}

static moduledata_t linux_elf_mod = {
        "linuxelf",
        linux_elf_modevent,
        0
};

DECLARE_MODULE(linuxelf, linux_elf_mod, SI_SUB_EXEC, SI_ORDER_ANY);