| 1 | /* Emulate AT_MINSIGSTKSZ. Linux/x86 version. |
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| 2 | Copyright (C) 2020-2022 Free Software Foundation, Inc. |
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| 3 | |
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| 4 | The GNU C Library is free software; you can redistribute it and/or |
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| 5 | modify it under the terms of the GNU Lesser General Public |
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| 6 | License as published by the Free Software Foundation; either |
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| 7 | version 2.1 of the License, or (at your option) any later version. |
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| 8 | |
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| 9 | The GNU C Library is distributed in the hope that it will be useful, |
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| 10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 12 | Lesser General Public License for more details. |
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| 13 | |
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| 14 | You should have received a copy of the GNU Lesser General Public |
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| 15 | License along with the GNU C Library; if not, see |
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| 16 | <https://www.gnu.org/licenses/>. */ |
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| 17 | |
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| 18 | /* Emulate AT_MINSIGSTKSZ with XSAVE. */ |
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| 19 | |
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| 20 | static inline void |
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| 21 | dl_check_minsigstacksize (const struct cpu_features *cpu_features) |
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| 22 | { |
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| 23 | /* Return if AT_MINSIGSTKSZ is provide by kernel. */ |
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| 24 | if (GLRO(dl_minsigstacksize) != 0) |
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| 25 | return; |
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| 26 | |
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| 27 | if (cpu_features->basic.max_cpuid >= 0xd |
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| 28 | && CPU_FEATURES_CPU_P (cpu_features, OSXSAVE)) |
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| 29 | { |
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| 30 | /* Emulate AT_MINSIGSTKSZ. In Linux kernel, the signal frame data |
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| 31 | with XSAVE is composed of the following areas and laid out as: |
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| 32 | ------------------------------ |
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| 33 | | alignment padding | |
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| 34 | ------------------------------ |
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| 35 | | xsave buffer | |
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| 36 | ------------------------------ |
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| 37 | | fsave header (32-bit only) | |
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| 38 | ------------------------------ |
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| 39 | | siginfo + ucontext | |
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| 40 | ------------------------------ |
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| 41 | */ |
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| 42 | |
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| 43 | unsigned int sigframe_size; |
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| 44 | |
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| 45 | #ifdef __x86_64__ |
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| 46 | /* NB: sizeof(struct rt_sigframe) + 8-byte return address in Linux |
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| 47 | kernel. */ |
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| 48 | sigframe_size = 440 + 8; |
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| 49 | #else |
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| 50 | /* NB: sizeof(struct sigframe_ia32) + sizeof(struct fregs_state)) + |
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| 51 | 4-byte return address + 3 * 4-byte arguments in Linux kernel. */ |
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| 52 | sigframe_size = 736 + 112 + 4 + 3 * 4; |
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| 53 | #endif |
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| 54 | |
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| 55 | /* Add 15 bytes to align the stack to 16 bytes. */ |
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| 56 | sigframe_size += 15; |
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| 57 | |
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| 58 | /* Make the space before xsave buffer multiple of 16 bytes. */ |
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| 59 | sigframe_size = ALIGN_UP (sigframe_size, 16); |
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| 60 | |
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| 61 | /* Add (64 - 16)-byte padding to align xsave buffer at 64 bytes. */ |
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| 62 | sigframe_size += 64 - 16; |
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| 63 | |
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| 64 | unsigned int eax, ebx, ecx, edx; |
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| 65 | __cpuid_count (0xd, 0, eax, ebx, ecx, edx); |
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| 66 | |
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| 67 | /* Add the size of xsave buffer. */ |
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| 68 | sigframe_size += ebx; |
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| 69 | |
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| 70 | /* Add the size of FP_XSTATE_MAGIC2. */ |
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| 71 | #define FP_XSTATE_MAGIC2 0x46505845U |
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| 72 | sigframe_size += sizeof (FP_XSTATE_MAGIC2); |
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| 73 | |
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| 74 | GLRO(dl_minsigstacksize) = sigframe_size; |
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| 75 | } |
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| 76 | else |
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| 77 | { |
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| 78 | /* NB: Default to a constant MINSIGSTKSZ. */ |
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| 79 | _Static_assert (__builtin_constant_p (MINSIGSTKSZ), |
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| 80 | "MINSIGSTKSZ is constant" ); |
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| 81 | GLRO(dl_minsigstacksize) = MINSIGSTKSZ; |
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| 82 | } |
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| 83 | } |
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| 84 | |
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