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/* Stack executability handling for GNU dynamic linker. Linux version.
Copyright (C) 2003-2024 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, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <ldsodefs.h>
#include <libintl.h>
#include <list.h>
#include <pthreadP.h>
#include <stackinfo.h>
#include <stdbool.h>
#include <sys/mman.h>
#include <sysdep.h>
#include <unistd.h>
extern int __stack_prot attribute_relro attribute_hidden;
static int
make_main_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;
if (__builtin_expect (__mprotect ((void *) page, GLRO(dl_pagesize),
__stack_prot) == 0, 1))
goto return_success;
result = errno;
goto out;
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;
}
int
_dl_make_stacks_executable (void **stack_endp)
{
/* First the main thread's stack. */
int err = make_main_stack_executable (stack_endp);
if (err != 0)
return err;
lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE);
list_t *runp;
list_for_each (runp, &GL (dl_stack_used))
{
err = __nptl_change_stack_perm (list_entry (runp, struct pthread, list));
if (err != 0)
break;
}
/* Also change the permission for the currently unused stacks. This
might be wasted time but better spend it here than adding a check
in the fast path. */
if (err == 0)
list_for_each (runp, &GL (dl_stack_cache))
{
err = __nptl_change_stack_perm (list_entry (runp, struct pthread,
list));
if (err != 0)
break;
}
lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
return err;
}
int
__nptl_change_stack_perm (struct pthread *pd)
{
#if _STACK_GROWS_DOWN
void *stack = pd->stackblock + pd->guardsize;
size_t len = pd->stackblock_size - pd->guardsize;
#elif _STACK_GROWS_UP
void *stack = pd->stackblock;
size_t len = (uintptr_t) pd - pd->guardsize - (uintptr_t) pd->stackblock;
#else
# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
#endif
if (__mprotect (stack, len, PROT_READ | PROT_WRITE | PROT_EXEC) != 0)
return errno;
return 0;
}
rtld_hidden_def (__nptl_change_stack_perm)
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