diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/dl-execstack.c')
| -rw-r--r-- | sysdeps/unix/sysv/linux/dl-execstack.c | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/dl-execstack.c b/sysdeps/unix/sysv/linux/dl-execstack.c new file mode 100644 index 0000000000..42300b0f4d --- /dev/null +++ b/sysdeps/unix/sysv/linux/dl-execstack.c @@ -0,0 +1,115 @@ +/* Stack executability handling for GNU dynamic linker. Linux version. + Copyright (C) 2003 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <ldsodefs.h> +#include <sys/mman.h> +#include <errno.h> +#include <stdbool.h> +#include <stackinfo.h> + +extern void *__libc_stack_end; + +int +internal_function +_dl_make_stack_executable (void) +{ + if (__libc_stack_end == 0) + /* XXX for a DT_NEEDED library that requires the change, + this is not initialized yet! + */ + return ENOSYS; + +#if _STACK_GROWS_DOWN + /* This gives us the highest page that needs to be changed. */ + uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize); + + /* There is always a hole in the address space below the bottom of the + stack. So when we make an mprotect call that starts below the bottom + of the stack, it will include the hole and fail with ENOMEM. + + We start with a random guess at how deep the stack might have gotten + so as to have extended the GROWSDOWN mapping to lower pages. */ + + size_t size = GL(dl_pagesize) * 8; + page = page + GL(dl_pagesize) - size; + while (1) + { + if (__mprotect ((void *) page, size, + PROT_READ|PROT_WRITE|PROT_EXEC) == 0) + /* We got this chunk changed; loop to do another chunk below. */ + page -= size; + else + { + if (errno != ENOMEM) /* Unexpected failure mode. */ + return errno; + + if (size == GL(dl_pagesize)) + /* We just tried to mprotect the top hole page and failed. + We are done. */ + break; + + /* Our mprotect call failed because it started below the lowest + stack page. Try again on just the top half of that region. */ + size /= 2; + page += size; + } + } + +#elif _STACK_GROWS_UP + + /* This gives us the lowest page that needs to be changed. */ + uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize); + + /* There is always a hole in the address space above the top of the + stack. So when we make an mprotect call that spans past the top + of the stack, it will include the hole and fail with ENOMEM. + + We start with a random guess at how deep the stack might have gotten + so as to have extended the GROWSUP mapping to higher pages. */ + + size_t size = GL(dl_pagesize) * 8; + while (1) + { + if (__mprotect ((void *) page, size, + PROT_READ|PROT_WRITE|PROT_EXEC) == 0) + /* We got this chunk changed; loop to do another chunk below. */ + page += size; + else + { + if (errno != ENOMEM) /* Unexpected failure mode. */ + return errno; + + if (size == GL(dl_pagesize)) + /* We just tried to mprotect the lowest hole page and failed. + We are done. */ + break; + + /* Our mprotect call failed because it extended past the highest + stack page. Try again on just the bottom half of that region. */ + size /= 2; + } + } + +#else +# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP" +#endif + + return 0; +} +rtld_hidden_def (_dl_make_stack_executable) |