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Protect against compiler optimizations

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GCC 5.4 optimized the write after poisoning (the surprising thing is that
11.4 doesn't).

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2023-11-23 12:33:39 +01:00
parent ef0f01fee6
commit 895ebc30f0
1 changed files with 11 additions and 0 deletions
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11
programs/test/metatest.c
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@ -66,6 +66,15 @@ static void set_to_zero_but_the_compiler_does_not_know(volatile void *p, size_t
memset((void *) p, false_but_the_compiler_does_not_know, n); memset((void *) p, false_but_the_compiler_does_not_know, n);
} }
/* Simulate an access to the given object, to avoid compiler optimizations
* in code that prepares or consumes the object. */
static void do_nothing_with_object(void *p)
{
(void) p;
}
void(*volatile do_nothing_with_object_but_the_compiler_does_not_know)(void *) =
do_nothing_with_object;
/****************************************************************/ /****************************************************************/
/* Test framework features */ /* Test framework features */
@ -202,7 +211,9 @@ void test_memory_poison(const char *name)
if (direction == 'w') { if (direction == 'w') {
aligned.buf[start + offset] = 'b'; aligned.buf[start + offset] = 'b';
do_nothing_with_object_but_the_compiler_does_not_know(aligned.buf);
} else { } else {
do_nothing_with_object_but_the_compiler_does_not_know(aligned.buf);
mbedtls_printf("%u\n", (unsigned) aligned.buf[start + offset]); mbedtls_printf("%u\n", (unsigned) aligned.buf[start + offset]);
} }
} }