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/* Emulate AT_MINSIGSTKSZ. Linux/x86 version.
Copyright (C) 2020-2022 Free Software Foundation, Inc.
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/>. */
/* Emulate AT_MINSIGSTKSZ with XSAVE. */
static inline void
dl_check_minsigstacksize (const struct cpu_features *cpu_features)
{
/* Return if AT_MINSIGSTKSZ is provide by kernel. */
if (GLRO(dl_minsigstacksize) != 0)
return;
if (cpu_features->basic.max_cpuid >= 0xd
&& CPU_FEATURES_CPU_P (cpu_features, OSXSAVE))
{
/* Emulate AT_MINSIGSTKSZ. In Linux kernel, the signal frame data
with XSAVE is composed of the following areas and laid out as:
------------------------------
| alignment padding |
------------------------------
| xsave buffer |
------------------------------
| fsave header (32-bit only) |
------------------------------
| siginfo + ucontext |
------------------------------
*/
unsigned int sigframe_size;
#ifdef __x86_64__
/* NB: sizeof(struct rt_sigframe) + 8-byte return address in Linux
kernel. */
sigframe_size = 440 + 8;
#else
/* NB: sizeof(struct sigframe_ia32) + sizeof(struct fregs_state)) +
4-byte return address + 3 * 4-byte arguments in Linux kernel. */
sigframe_size = 736 + 112 + 4 + 3 * 4;
#endif
/* Add 15 bytes to align the stack to 16 bytes. */
sigframe_size += 15;
/* Make the space before xsave buffer multiple of 16 bytes. */
sigframe_size = ALIGN_UP (sigframe_size, 16);
/* Add (64 - 16)-byte padding to align xsave buffer at 64 bytes. */
sigframe_size += 64 - 16;
unsigned int eax, ebx, ecx, edx;
__cpuid_count (0xd, 0, eax, ebx, ecx, edx);
/* Add the size of xsave buffer. */
sigframe_size += ebx;
/* Add the size of FP_XSTATE_MAGIC2. */
#define FP_XSTATE_MAGIC2 0x46505845U
sigframe_size += sizeof (FP_XSTATE_MAGIC2);
GLRO(dl_minsigstacksize) = sigframe_size;
}
else
{
/* NB: Default to a constant MINSIGSTKSZ. */
_Static_assert (__builtin_constant_p (MINSIGSTKSZ),
"MINSIGSTKSZ is constant");
GLRO(dl_minsigstacksize) = MINSIGSTKSZ;
}
}
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