1/* Emulate AT_MINSIGSTKSZ. Linux/x86 version.
2 Copyright (C) 2020 Free Software Foundation, Inc.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18/* Emulate AT_MINSIGSTKSZ with XSAVE. */
19
20static inline void
21dl_check_minsigstacksize (const struct cpu_features *cpu_features)
22{
23 /* Return if AT_MINSIGSTKSZ is provide by kernel. */
24 if (GLRO(dl_minsigstacksize) != 0)
25 return;
26
27 if (cpu_features->basic.max_cpuid >= 0xd
28 && CPU_FEATURES_CPU_P (cpu_features, OSXSAVE))
29 {
30 /* Emulate AT_MINSIGSTKSZ. In Linux kernel, the signal frame data
31 with XSAVE is composed of the following areas and laid out as:
32 ------------------------------
33 | alignment padding |
34 ------------------------------
35 | xsave buffer |
36 ------------------------------
37 | fsave header (32-bit only) |
38 ------------------------------
39 | siginfo + ucontext |
40 ------------------------------
41 */
42
43 unsigned int sigframe_size;
44
45#ifdef __x86_64__
46 /* NB: sizeof(struct rt_sigframe) + 8-byte return address in Linux
47 kernel. */
48 sigframe_size = 440 + 8;
49#else
50 /* NB: sizeof(struct sigframe_ia32) + sizeof(struct fregs_state)) +
51 4-byte return address + 3 * 4-byte arguments in Linux kernel. */
52 sigframe_size = 736 + 112 + 4 + 3 * 4;
53#endif
54
55 /* Add 15 bytes to align the stack to 16 bytes. */
56 sigframe_size += 15;
57
58 /* Make the space before xsave buffer multiple of 16 bytes. */
59 sigframe_size = ALIGN_UP (sigframe_size, 16);
60
61 /* Add (64 - 16)-byte padding to align xsave buffer at 64 bytes. */
62 sigframe_size += 64 - 16;
63
64 unsigned int eax, ebx, ecx, edx;
65 __cpuid_count (0xd, 0, eax, ebx, ecx, edx);
66
67 /* Add the size of xsave buffer. */
68 sigframe_size += ebx;
69
70 /* Add the size of FP_XSTATE_MAGIC2. */
71#define FP_XSTATE_MAGIC2 0x46505845U
72 sigframe_size += sizeof (FP_XSTATE_MAGIC2);
73
74 GLRO(dl_minsigstacksize) = sigframe_size;
75 }
76 else
77 {
78 /* NB: Default to a constant MINSIGSTKSZ. */
79 _Static_assert (__builtin_constant_p (MINSIGSTKSZ),
80 "MINSIGSTKSZ is constant");
81 GLRO(dl_minsigstacksize) = MINSIGSTKSZ;
82 }
83}
84