bsd-user/freebsd/target_os_stack.h

   1 /*
   2  *  FreeBSD setup_initial_stack() implementation.
   3  *
   4  *  Copyright (c) 2013-14 Stacey D. Son
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 2 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #ifndef TARGET_OS_STACK_H
  21 #define TARGET_OS_STACK_H
  22
  23 #include <sys/param.h>
  24 #include "target_arch_sigtramp.h"
  25 #include "qemu/guest-random.h"
  26
  27 /*
  28  * The inital FreeBSD stack is as follows:
  29  * (see kern/kern_exec.c exec_copyout_strings() )
  30  *
  31  *  Hi Address -> char **ps_argvstr  (struct ps_strings for ps, w, etc.)
  32  *                unsigned ps_nargvstr
  33  *                char **ps_envstr
  34  *  PS_STRINGS -> unsigned ps_nenvstr
  35  *
  36  *                machine dependent sigcode (sv_sigcode of size
  37  *                                           sv_szsigcode)
  38  *
  39  *                execpath          (absolute image path for rtld)
  40  *
  41  *                SSP Canary        (sizeof(long) * 8)
  42  *
  43  *                page sizes array  (usually sizeof(u_long) )
  44  *
  45  *  "destp" ->    argv, env strings (up to 262144 bytes)
  46  */
  47 static inline int setup_initial_stack(struct bsd_binprm *bprm,
  48         abi_ulong *ret_addr, abi_ulong *stringp)
  49 {
  50     int i;
  51     abi_ulong stack_hi_addr;
  52     size_t execpath_len, stringspace;
  53     abi_ulong destp, argvp, envp, p;
  54     struct target_ps_strings ps_strs;
  55     char canary[sizeof(abi_long) * 8];
  56
  57     stack_hi_addr = p = target_stkbas + target_stksiz;
  58
  59     /* Save some space for ps_strings. */
  60     p -= sizeof(struct target_ps_strings);
  61
  62     /* Add machine depedent sigcode. */
  63     p -= TARGET_SZSIGCODE;
  64     if (setup_sigtramp(p, (unsigned)offsetof(struct target_sigframe, sf_uc),
  65             TARGET_FREEBSD_NR_sigreturn)) {
  66         errno = EFAULT;
  67         return -1;
  68     }
  69     if (bprm->fullpath) {
  70         execpath_len = strlen(bprm->fullpath) + 1;
  71         p -= roundup(execpath_len, sizeof(abi_ulong));
  72         if (memcpy_to_target(p, bprm->fullpath, execpath_len)) {
  73             errno = EFAULT;
  74             return -1;
  75         }
  76     }
  77     /* Add canary for SSP. */
  78     qemu_guest_getrandom_nofail(canary, sizeof(canary));
  79     p -= roundup(sizeof(canary), sizeof(abi_ulong));
  80     if (memcpy_to_target(p, canary, sizeof(canary))) {
  81         errno = EFAULT;
  82         return -1;
  83     }
  84     /* Add page sizes array. */
  85     p -= sizeof(abi_ulong);
  86     if (put_user_ual(TARGET_PAGE_SIZE, p)) {
  87         errno = EFAULT;
  88         return -1;
  89     }
  90     /*
  91      * Deviate from FreeBSD stack layout: force stack to new page here
  92      * so that signal trampoline is not sharing the page with user stack
  93      * frames. This is actively harmful in qemu as it marks pages with
  94      * code it translated as read-only, which is somewhat problematic
  95      * for user trying to use the stack as intended.
  96      */
  97     p = rounddown(p, TARGET_PAGE_SIZE);
  98
  99     /* Calculate the string space needed */
 100     stringspace = 0;
 101     for (i = 0; i < bprm->argc; ++i) {
 102         stringspace += strlen(bprm->argv[i]) + 1;
 103     }
 104     for (i = 0; i < bprm->envc; ++i) {
 105         stringspace += strlen(bprm->envp[i]) + 1;
 106     }
 107     if (stringspace > TARGET_ARG_MAX) {
 108         errno = ENOMEM;
 109         return -1;
 110     }
 111     /* Make room for the argv and envp strings */
 112     destp = rounddown(p - stringspace, sizeof(abi_ulong));
 113     p = argvp = destp - (bprm->argc + bprm->envc + 2) * sizeof(abi_ulong);
 114     /* Remember the strings pointer */
 115     if (stringp) {
 116         *stringp = destp;
 117     }
 118     /*
 119      * Add argv strings.  Note that the argv[] vectors are added by
 120      * loader_build_argptr()
 121      */
 122     /* XXX need to make room for auxargs */
 123     ps_strs.ps_argvstr = tswapl(argvp);
 124     ps_strs.ps_nargvstr = tswap32(bprm->argc);
 125     for (i = 0; i < bprm->argc; ++i) {
 126         size_t len = strlen(bprm->argv[i]) + 1;
 127
 128         if (memcpy_to_target(destp, bprm->argv[i], len)) {
 129             errno = EFAULT;
 130             return -1;
 131         }
 132         if (put_user_ual(destp, argvp)) {
 133             errno = EFAULT;
 134             return -1;
 135         }
 136         argvp += sizeof(abi_ulong);
 137         destp += len;
 138     }
 139     if (put_user_ual(0, argvp)) {
 140         errno = EFAULT;
 141         return -1;
 142     }
 143     /*
 144      * Add env strings. Note that the envp[] vectors are added by
 145      * loader_build_argptr().
 146      */
 147     envp = argvp + sizeof(abi_ulong);
 148     ps_strs.ps_envstr = tswapl(envp);
 149     ps_strs.ps_nenvstr = tswap32(bprm->envc);
 150     for (i = 0; i < bprm->envc; ++i) {
 151         size_t len = strlen(bprm->envp[i]) + 1;
 152
 153         if (memcpy_to_target(destp, bprm->envp[i], len)) {
 154             errno = EFAULT;
 155             return -1;
 156         }
 157         if (put_user_ual(destp, envp)) {
 158             errno = EFAULT;
 159             return -1;
 160         }
 161         envp += sizeof(abi_ulong);
 162         destp += len;
 163     }
 164     if (put_user_ual(0, envp)) {
 165         errno = EFAULT;
 166         return -1;
 167     }
 168     if (memcpy_to_target(stack_hi_addr - sizeof(ps_strs), &ps_strs,
 169                 sizeof(ps_strs))) {
 170         errno = EFAULT;
 171         return -1;
 172     }
 173
 174     if (ret_addr) {
 175         *ret_addr = p;
 176     }
 177
 178     return 0;
 179  }
 180
 181 #endif /* TARGET_OS_STACK_H */