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elf: early conversion of elf p_flags to mprotect flags

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This patch replaces _dl_stack_flags global variable by
_dl_stack_prot_flags.
The advantage is that any convertion from p_flags to final used mprotect
flags occurs at loading of p_flags. It avoids repeated spurious
convertions of _dl_stack_flags, for example in allocate_thread_stack.

This modification was suggested in:
  https://sourceware.org/pipermail/libc-alpha/2025-March/165537.html

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Cupertino Miranda
2025-08-22 11:37:00 +01:00
committed by Adhemerval Zanella
parent 921e251e8f
commit 3b2b88ccee
30 changed files with 104 additions and 102 deletions
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9
support/support_stack_alloc.c
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@@ -64,11 +64,10 @@ support_stack_alloc (size_t size)
MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE|MAP_STACK,
-1);
/* Some architecture still requires executable stack for the signal return
trampoline, although PF_X could be overridden if PT_GNU_STACK is present.
However since glibc does not export such information with a proper ABI,
it uses the historical permissions. */
int prot = PROT_READ | PROT_WRITE
| (DEFAULT_STACK_PERMS & PF_X ? PROT_EXEC : 0);
trampoline, although PROT_EXEC could be overridden if PT_GNU_STACK is
present. However since glibc does not export such information with a
proper ABI, it uses the historical permissions. */
int prot = DEFAULT_STACK_PROT_PERMS;
xmprotect (alloc_base + guardsize, stacksize, prot);
memset (alloc_base + guardsize, 0xA5, stacksize);
return (struct support_stack) { alloc_base + guardsize, stacksize, guardsize };