Warner Losh | 534217f | 2021-08-04 13:49:21 -0600 | [diff] [blame] | 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_ */ |