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https://gitlab.com/cryptsetup/cryptsetup.git
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3a8feb8be7
The compiler may advertise function attribute support
with __has_attribute operator even though it does
not implement the feature on some architecture.
This fixes the issue with GCC 11 on ppc64le with
__attribute__((zero_call_used_regs("used"))).
Fixes: #959.
62 lines
1.5 KiB
C
62 lines
1.5 KiB
C
// SPDX-License-Identifier: LGPL-2.1-or-later
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/*
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* Safe memory utilities
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*
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* Copyright (C) 2024-2025 Milan Broz
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*/
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#include "crypto_backend_internal.h"
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#define ATTR_NOINLINE __attribute__ ((noinline))
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#define ATTR_ZERO_REGS
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#if HAVE_ATTRIBUTE_ZEROCALLUSEDREGS
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# undef ATTR_ZERO_REGS
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# define ATTR_ZERO_REGS __attribute__ ((zero_call_used_regs("used")))
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#endif
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/* Workaround for https://github.com/google/sanitizers/issues/1507 */
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#if defined __has_feature
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# if __has_feature (memory_sanitizer)
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# undef HAVE_EXPLICIT_BZERO
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# endif
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#endif
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/* Memzero helper (memset on stack can be optimized out) */
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ATTR_NOINLINE ATTR_ZERO_REGS
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void crypt_backend_memzero(void *s, size_t n)
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{
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#if HAVE_EXPLICIT_BZERO
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explicit_bzero(s, n);
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#else
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volatile uint8_t *p = (volatile uint8_t *)s;
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while(n--) *p++ = 0;
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#endif
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}
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/* Memcpy helper to avoid spilling sensitive data through additional registers */
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ATTR_NOINLINE ATTR_ZERO_REGS
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void *crypt_backend_memcpy(void *dst, const void *src, size_t n)
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{
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volatile uint8_t *d = (volatile uint8_t *)dst;
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const volatile uint8_t *s = (const volatile uint8_t *)src;
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while(n--) *d++ = *s++;
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return dst;
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}
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/* Internal implementation for constant time memory comparison */
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ATTR_NOINLINE ATTR_ZERO_REGS
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int crypt_internal_memeq(const void *m1, const void *m2, size_t n)
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{
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const unsigned char *_m1 = (const unsigned char *) m1;
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const unsigned char *_m2 = (const unsigned char *) m2;
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unsigned char result = 0;
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size_t i;
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for (i = 0; i < n; i++)
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result |= _m1[i] ^ _m2[i];
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return result;
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}
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