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AES clang: make x volatile in pre-fetch functions

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Latest version of clang with optimization turned right up will make the
pre-fetch functions return 0.
The pre-fetch functions are there to ensure tables are all in cache not
to calculate a value.
This commit is contained in:
Sean Parkinson
2026-02-17 08:44:24 +10:00
parent d81bb7234a
commit 299e7bd097
1 changed files with 14 additions and 8 deletions
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wolfcrypt/src/aes.c
+14 -8
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@@ -1880,15 +1880,17 @@ static WARN_UNUSED_RESULT word32 inv_col_mul(
static WARN_UNUSED_RESULT WC_INLINE word32 PreFetchTe(void) static WARN_UNUSED_RESULT WC_INLINE word32 PreFetchTe(void)
{ {
#ifndef WOLFSSL_AES_TOUCH_LINES #ifndef WOLFSSL_AES_TOUCH_LINES
word32 x = 0; volatile word32 x = 0;
int i,j; int i;
int j;
for (i = 0; i < 4; i++) { for (i = 0; i < 4; i++) {
/* 256 elements, each one is 4 bytes */ /* 256 elements, each one is 4 bytes */
for (j = 0; j < 256; j += WC_CACHE_LINE_SZ/4) { for (j = 0; j < 256; j += WC_CACHE_LINE_SZ / 4) {
x &= Te[i][j]; x &= Te[i][j];
} }
} }
return x; return x;
#else #else
return 0; return 0;
@@ -1899,12 +1901,13 @@ static WARN_UNUSED_RESULT WC_INLINE word32 PreFetchTe(void)
static WARN_UNUSED_RESULT WC_INLINE word32 PreFetchSBox(void) static WARN_UNUSED_RESULT WC_INLINE word32 PreFetchSBox(void)
{ {
#ifndef WOLFSSL_AES_TOUCH_LINES #ifndef WOLFSSL_AES_TOUCH_LINES
word32 x = 0; volatile word32 x = 0;
int i; int i;
for (i = 0; i < 256; i += WC_CACHE_LINE_SZ/4) { for (i = 0; i < 256; i += WC_CACHE_LINE_SZ/4) {
x &= Tsbox[i]; x &= Tsbox[i];
} }
return x; return x;
#else #else
return 0; return 0;
@@ -3168,15 +3171,17 @@ static WARN_UNUSED_RESULT int wc_AesEncrypt(
/* load 4 Td Tables into cache by cache line stride */ /* load 4 Td Tables into cache by cache line stride */
static WARN_UNUSED_RESULT WC_INLINE word32 PreFetchTd(void) static WARN_UNUSED_RESULT WC_INLINE word32 PreFetchTd(void)
{ {
word32 x = 0; volatile word32 x = 0;
int i,j; int i;
int j;
for (i = 0; i < 4; i++) { for (i = 0; i < 4; i++) {
/* 256 elements, each one is 4 bytes */ /* 256 elements, each one is 4 bytes */
for (j = 0; j < 256; j += WC_CACHE_LINE_SZ/4) { for (j = 0; j < 256; j += WC_CACHE_LINE_SZ / 4) {
x &= Td[i][j]; x &= Td[i][j];
} }
} }
return x; return x;
} }
#endif /* !WOLFSSL_AES_SMALL_TABLES */ #endif /* !WOLFSSL_AES_SMALL_TABLES */
@@ -3185,12 +3190,13 @@ static WARN_UNUSED_RESULT WC_INLINE word32 PreFetchTd(void)
static WARN_UNUSED_RESULT WC_INLINE word32 PreFetchTd4(void) static WARN_UNUSED_RESULT WC_INLINE word32 PreFetchTd4(void)
{ {
#ifndef WOLFSSL_AES_TOUCH_LINES #ifndef WOLFSSL_AES_TOUCH_LINES
word32 x = 0; volatile word32 x = 0;
int i; int i;
for (i = 0; i < 256; i += WC_CACHE_LINE_SZ) { for (i = 0; i < 256; i += WC_CACHE_LINE_SZ) {
x &= (word32)Td4[i]; x &= (word32)Td4[i];
} }
return x; return x;
#else #else
return 0; return 0;