projects / thirdparty / glibc.git / blame
| Commit | Line | Data |
|---|---|---|
| ecdeaac0 RM |
1 | /* Stack executability handling for GNU dynamic linker. Linux version. |
| 2 | Copyright (C) 2003 Free Software Foundation, Inc. | |
| 3 | This file is part of the GNU C Library. | |
| 4 | ||
| 5 | The GNU C Library is free software; you can redistribute it and/or | |
| 6 | modify it under the terms of the GNU Lesser General Public | |
| 7 | License as published by the Free Software Foundation; either | |
| 8 | version 2.1 of the License, or (at your option) any later version. | |
| 9 | ||
| 10 | The GNU C Library is distributed in the hope that it will be useful, | |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 | Lesser General Public License for more details. | |
| 14 | ||
| 15 | You should have received a copy of the GNU Lesser General Public | |
| 16 | License along with the GNU C Library; if not, write to the Free | |
| 17 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA | |
| 18 | 02111-1307 USA. */ | |
| 19 | ||
| 20 | #include <ldsodefs.h> | |
| 21 | #include <sys/mman.h> | |
| 22 | #include <errno.h> | |
| 23 | #include <stdbool.h> | |
| 24 | #include <stackinfo.h> | |
| 25 | ||
| 26 | extern void *__libc_stack_end; | |
| 27 | ||
| 28 | int | |
| 29 | internal_function | |
| 30 | _dl_make_stack_executable (void) | |
| 31 | { | |
| ecdeaac0 RM |
32 | #if _STACK_GROWS_DOWN |
| 33 | /* This gives us the highest page that needs to be changed. */ | |
| 34 | uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize); | |
| 35 | ||
| e95dc10c RM |
36 | /* Newer Linux kernels support a flag to make our job easy. */ |
| 37 | # ifdef PROT_GROWSDOWN | |
| 38 | static bool no_growsdown; | |
| 39 | if (! no_growsdown) | |
| 40 | { | |
| 41 | if (__mprotect ((void *) page, GL(dl_pagesize), | |
| 42 | PROT_READ|PROT_WRITE|PROT_EXEC|PROT_GROWSDOWN) == 0) | |
| 43 | return 0; | |
| 44 | if (errno != EINVAL) | |
| 45 | return errno; | |
| 46 | no_growsdown = true; | |
| 47 | } | |
| 48 | # endif | |
| 49 | ||
| ecdeaac0 RM |
50 | /* There is always a hole in the address space below the bottom of the |
| 51 | stack. So when we make an mprotect call that starts below the bottom | |
| 52 | of the stack, it will include the hole and fail with ENOMEM. | |
| 53 | ||
| 54 | We start with a random guess at how deep the stack might have gotten | |
| 55 | so as to have extended the GROWSDOWN mapping to lower pages. */ | |
| 56 | ||
| 57 | size_t size = GL(dl_pagesize) * 8; | |
| 58 | page = page + GL(dl_pagesize) - size; | |
| 59 | while (1) | |
| 60 | { | |
| 61 | if (__mprotect ((void *) page, size, | |
| 62 | PROT_READ|PROT_WRITE|PROT_EXEC) == 0) | |
| 63 | /* We got this chunk changed; loop to do another chunk below. */ | |
| 64 | page -= size; | |
| 65 | else | |
| 66 | { | |
| 67 | if (errno != ENOMEM) /* Unexpected failure mode. */ | |
| 68 | return errno; | |
| 69 | ||
| 70 | if (size == GL(dl_pagesize)) | |
| 71 | /* We just tried to mprotect the top hole page and failed. | |
| 72 | We are done. */ | |
| 73 | break; | |
| 74 | ||
| 75 | /* Our mprotect call failed because it started below the lowest | |
| 76 | stack page. Try again on just the top half of that region. */ | |
| 77 | size /= 2; | |
| 78 | page += size; | |
| 79 | } | |
| 80 | } | |
| 81 | ||
| 82 | #elif _STACK_GROWS_UP | |
| 83 | ||
| 84 | /* This gives us the lowest page that needs to be changed. */ | |
| 85 | uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize); | |
| 86 | ||
| e95dc10c RM |
87 | /* Newer Linux kernels support a flag to make our job easy. */ |
| 88 | # ifdef PROT_GROWSUP | |
| 89 | static bool no_growsup; | |
| 90 | if (! no_growsup) | |
| 91 | { | |
| 92 | if (__mprotect ((void *) page, GL(dl_pagesize), | |
| 93 | PROT_READ|PROT_WRITE|PROT_EXEC|PROT_GROWSUP) == 0) | |
| 94 | return 0; | |
| 95 | if (errno != EINVAL) | |
| 96 | return errno; | |
| 97 | no_growsup = true; | |
| 98 | } | |
| 99 | # endif | |
| 100 | ||
| ecdeaac0 RM |
101 | /* There is always a hole in the address space above the top of the |
| 102 | stack. So when we make an mprotect call that spans past the top | |
| 103 | of the stack, it will include the hole and fail with ENOMEM. | |
| 104 | ||
| 105 | We start with a random guess at how deep the stack might have gotten | |
| 106 | so as to have extended the GROWSUP mapping to higher pages. */ | |
| 107 | ||
| 108 | size_t size = GL(dl_pagesize) * 8; | |
| 109 | while (1) | |
| 110 | { | |
| 111 | if (__mprotect ((void *) page, size, | |
| 112 | PROT_READ|PROT_WRITE|PROT_EXEC) == 0) | |
| 113 | /* We got this chunk changed; loop to do another chunk below. */ | |
| 114 | page += size; | |
| 115 | else | |
| 116 | { | |
| 117 | if (errno != ENOMEM) /* Unexpected failure mode. */ | |
| 118 | return errno; | |
| 119 | ||
| 120 | if (size == GL(dl_pagesize)) | |
| 121 | /* We just tried to mprotect the lowest hole page and failed. | |
| 122 | We are done. */ | |
| 123 | break; | |
| 124 | ||
| 125 | /* Our mprotect call failed because it extended past the highest | |
| 126 | stack page. Try again on just the bottom half of that region. */ | |
| 127 | size /= 2; | |
| 128 | } | |
| 129 | } | |
| 130 | ||
| 131 | #else | |
| 132 | # error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP" | |
| 133 | #endif | |
| 134 | ||
| 69c9fa04 UD |
135 | /* Remember that we changed the permission. */ |
| 136 | GL(dl_stack_flags) |= PF_X; | |
| 137 | ||
| ecdeaac0 RM |
138 | return 0; |
| 139 | } | |
| 140 | rtld_hidden_def (_dl_make_stack_executable) |