diff options
Diffstat (limited to 'libc/sysdeps/unix/sysv/linux/dl-execstack.c')
| -rw-r--r-- | libc/sysdeps/unix/sysv/linux/dl-execstack.c | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/libc/sysdeps/unix/sysv/linux/dl-execstack.c b/libc/sysdeps/unix/sysv/linux/dl-execstack.c new file mode 100644 index 000000000..fcac5ae24 --- /dev/null +++ b/libc/sysdeps/unix/sysv/linux/dl-execstack.c @@ -0,0 +1,154 @@ +/* Stack executability handling for GNU dynamic linker. Linux version. + Copyright (C) 2003, 2004, 2005, 2006 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 <libintl.h> +#include <stdbool.h> +#include <stackinfo.h> +#include <caller.h> +#include <sysdep.h> + +#include <kernel-features.h> + + +extern int __stack_prot attribute_relro attribute_hidden; + + +int +internal_function +_dl_make_stack_executable (void **stack_endp) +{ + /* This gives us the highest/lowest page that needs to be changed. */ + uintptr_t page = ((uintptr_t) *stack_endp + & -(intptr_t) GLRO(dl_pagesize)); + int result = 0; + + /* Challenge the caller. */ + if (__builtin_expect (__check_caller (RETURN_ADDRESS (0), + allow_ldso|allow_libpthread) != 0, 0) + || __builtin_expect (*stack_endp != __libc_stack_end, 0)) + return EPERM; + + /* Newer Linux kernels support a flag to make our job easy. */ +#if defined PROT_GROWSDOWN || defined PROT_GROWSUP +# if __ASSUME_PROT_GROWSUPDOWN == 0 + static bool no_growsupdown; + if (! no_growsupdown) +# endif + { + if (__builtin_expect (__mprotect ((void *) page, GLRO(dl_pagesize), + __stack_prot) == 0, 1)) + goto return_success; +# if __ASSUME_PROT_GROWSUPDOWN == 0 + if (errno == EINVAL) + no_growsupdown = true; + else +# endif + { + result = errno; + goto out; + } + } +#endif + + /* 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. */ + +#if __ASSUME_PROT_GROWSUPDOWN == 0 + size_t size = GLRO(dl_pagesize) * 8; + +# if _STACK_GROWS_DOWN + page = page + GLRO(dl_pagesize) - size; + while (1) + { + if (__mprotect ((void *) page, size, + __stack_prot & ~PROT_GROWSDOWN) == 0) + /* We got this chunk changed; loop to do another chunk below. */ + page -= size; + else + { + if (errno != ENOMEM) /* Unexpected failure mode. */ + { + result = errno; + goto out; + } + + if (size == GLRO(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 + while (1) + { + if (__mprotect ((void *) page, size, __stack_prot & ~PROT_GROWSUP) == 0) + /* We got this chunk changed; loop to do another chunk below. */ + page += size; + else + { + if (errno != ENOMEM) /* Unexpected failure mode. */ + { + result = errno; + goto out; + } + + if (size == GLRO(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 +#endif + + return_success: + /* Clear the address. */ + *stack_endp = NULL; + + /* Remember that we changed the permission. */ + GL(dl_stack_flags) |= PF_X; + + out: +#ifdef check_consistency + check_consistency (); +#endif + + return result; +} +rtld_hidden_def (_dl_make_stack_executable) |