The cache-test test program attempts to create a collision (using key_a
and key_a_collide) by making the first two bytes identical. The idea is
fine -- the shader cache wants to use the first four characters of a
SHA1 hex digest as the index.
The following program
unsigned char array[4] = {1, 2, 3, 4};
int *ptr = (int *)array;
for (int i = 0; i < 4; i++) {
printf("%02x", array[i]);
}
printf("\n");
printf("%08x\n", *ptr);
prints
01020304
04030201
on little endian, and
01020304
01020304
on big endian.
On big endian platforms reading the character array back as an int (as
is done in disk_cache.c) does not yield the same results as reading the
byte array.
To get the first four characters of the SHA1 hex digest when we mask
with CACHE_INDEX_KEY_MASK, we need to byte swap the int on big endian
platforms.
Bugzilla: https://bugs.freedesktop.org/103668
Bugzilla: https://bugs.gentoo.org/637060
Bugzilla: https://bugs.gentoo.org/636326
---
src/util/disk_cache.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/util/disk_cache.c b/src/util/disk_cache.c
index fde6e2e097..e95406565e 100644
--- a/src/util/disk_cache.c
+++ b/src/util/disk_cache.c
@@ -1170,7 +1170,7 @@ void
disk_cache_put_key(struct disk_cache *cache, const cache_key key)
{
const uint32_t *key_chunk = (const uint32_t *) key;
- int i = *key_chunk & CACHE_INDEX_KEY_MASK;
+ int i = CPU_TO_LE32(*key_chunk) & CACHE_INDEX_KEY_MASK;
unsigned char *entry;
entry = &cache->stored_keys[i * CACHE_KEY_SIZE];
@@ -1189,7 +1189,7 @@ bool
disk_cache_has_key(struct disk_cache *cache, const cache_key key)
{
const uint32_t *key_chunk = (const uint32_t *) key;
- int i = *key_chunk & CACHE_INDEX_KEY_MASK;
+ int i = CPU_TO_LE32(*key_chunk) & CACHE_INDEX_KEY_MASK;
unsigned char *entry;
entry = &cache->stored_keys[i * CACHE_KEY_SIZE];
--
2.13.6
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