glibc/sysdeps/x86_64/dl-trampoline-save.h

/* x86-64 PLT trampoline register save macros.
   Copyright (C) 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/>.  */

#ifndef DL_STACK_ALIGNMENT
/* Due to GCC bug:

   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58066

   __tls_get_addr may be called with 8-byte stack alignment.  Although
   this bug has been fixed in GCC 4.9.4, 5.3 and 6, we can't assume
   that stack will be always aligned at 16 bytes.  */
# define DL_STACK_ALIGNMENT 8
#endif

/* True if _dl_runtime_resolve should align stack for STATE_SAVE or align
   stack to 16 bytes before calling _dl_fixup.  */
#define DL_RUNTIME_RESOLVE_REALIGN_STACK \
  (STATE_SAVE_ALIGNMENT > DL_STACK_ALIGNMENT \
   || 16 > DL_STACK_ALIGNMENT)
x86: Update _dl_tlsdesc_dynamic to preserve caller-saved registers Compiler generates the following instruction sequence for GNU2 dynamic TLS access: leaq tls_var@TLSDESC(%rip), %rax call tls_var@TLSCALL(%rax) or leal tls_var@TLSDESC(%ebx), %eax call tls_var@TLSCALL(%eax) CALL instruction is transparent to compiler which assumes all registers, except for EFLAGS and RAX/EAX, are unchanged after CALL. When _dl_tlsdesc_dynamic is called, it calls __tls_get_addr on the slow path. __tls_get_addr is a normal function which doesn't preserve any caller-saved registers. _dl_tlsdesc_dynamic saved and restored integer caller-saved registers, but didn't preserve any other caller-saved registers. Add _dl_tlsdesc_dynamic IFUNC functions for FNSAVE, FXSAVE, XSAVE and XSAVEC to save and restore all caller-saved registers. This fixes BZ #31372. Add GLRO(dl_x86_64_runtime_resolve) with GLRO(dl_x86_tlsdesc_dynamic) to optimize elf_machine_runtime_setup. Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com> 2024-02-26 14:37:03 +00:00			`/* x86-64 PLT trampoline register save macros.`
			`Copyright (C) 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/>. */`

			`#ifndef DL_STACK_ALIGNMENT`
			`/* Due to GCC bug:`

			`https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58066`

			`__tls_get_addr may be called with 8-byte stack alignment. Although`
			`this bug has been fixed in GCC 4.9.4, 5.3 and 6, we can't assume`
			`that stack will be always aligned at 16 bytes. */`
			`# define DL_STACK_ALIGNMENT 8`
			`#endif`

			`/* True if _dl_runtime_resolve should align stack for STATE_SAVE or align`
			`stack to 16 bytes before calling _dl_fixup. */`
			`#define DL_RUNTIME_RESOLVE_REALIGN_STACK \`
			`(STATE_SAVE_ALIGNMENT > DL_STACK_ALIGNMENT \`
			`\|\| 16 > DL_STACK_ALIGNMENT)`