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2003-09-25 Roland McGrath <roland@redhat.com>

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* sysdeps/unix/sysv/linux/dl-execstack.c (_dl_make_stack_executable):
	Don't check for zero __libc_stack_end, it should be initialized.
	[_STACK_GROWS_DOWN] [PROT_GROWSDOWN]: Try using PROT_GROWSDOWN flag
	and fall back if it fails with EINVAL.
	[_STACK_GROWS_UP] [PROT_GROWSUP]: Likewise for PROT_GROWSUP.
This commit is contained in:
Roland McGrath
2003-09-25 23:04:12 +00:00
parent 55715bfca6
commit e95dc10c40
1 changed files with 28 additions and 6 deletions
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34
sysdeps/unix/sysv/linux/dl-execstack.c
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@ -29,16 +29,24 @@ int
internal_function internal_function
_dl_make_stack_executable (void) _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 #if _STACK_GROWS_DOWN
/* This gives us the highest page that needs to be changed. */ /* This gives us the highest page that needs to be changed. */
uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize); uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize);
/* Newer Linux kernels support a flag to make our job easy. */
# ifdef PROT_GROWSDOWN
static bool no_growsdown;
if (! no_growsdown)
{
if (__mprotect ((void *) page, GL(dl_pagesize),
PROT_READ|PROT_WRITE|PROT_EXEC|PROT_GROWSDOWN) == 0)
return 0;
if (errno != EINVAL)
return errno;
no_growsdown = true;
}
# endif
/* There is always a hole in the address space below the bottom of the /* 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 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. of the stack, it will include the hole and fail with ENOMEM.
@ -76,6 +84,20 @@ _dl_make_stack_executable (void)
/* This gives us the lowest page that needs to be changed. */ /* This gives us the lowest page that needs to be changed. */
uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize); uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize);
/* Newer Linux kernels support a flag to make our job easy. */
# ifdef PROT_GROWSUP
static bool no_growsup;
if (! no_growsup)
{
if (__mprotect ((void *) page, GL(dl_pagesize),
PROT_READ|PROT_WRITE|PROT_EXEC|PROT_GROWSUP) == 0)
return 0;
if (errno != EINVAL)
return errno;
no_growsup = true;
}
# endif
/* There is always a hole in the address space above the top of the /* 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 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. of the stack, it will include the hole and fail with ENOMEM.