LAV
/
FFmpeg
1
0
Fork 0
Code

avcodec/lossless_videoencdsp: Fix unaligned access 

HAVE_FAST_UNALIGNED being true does not imply that
one can simply read from any pointer via *(long*).
It is undefined behaviour in case the pointer is not
sufficiently aligned; and even if it is, it is (likely)
a violation of the effective-type rules. Fix both
of these by using the appropriate AV_[RW]N macros.

Also, the current code used sizeof(long) as if this
were the CPU's native arithmetic size, but this is
not true on 64bit Windows. This has been fixed, too.

This affected huffyuv FATE-tests.

Tested-by: Sean McGovern <gseanmcg@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2024-03-13 01:32:08 +01:00
parent 7a089ed8e0
commit cc2d2b665e
1 changed files with 19 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
libavcodec/lossless_videoencdsp.c
View File

@ -18,19 +18,31 @@
#include "config.h"
#include "libavutil/attributes.h"
#include "libavutil/intreadwrite.h"
#include "lossless_videoencdsp.h"
#include "mathops.h"
#if HAVE_FAST_64BIT
typedef uint64_t uint_native;
#define READ AV_RN64
#define READA AV_RN64A
#define WRITEA AV_WN64A
#else
typedef uint32_t uint_native;
#define READ AV_RN32
#define READA AV_RN32A
#define WRITEA AV_WN32A
#endif
// 0x7f7f7f7f or 0x7f7f7f7f7f7f7f7f or whatever, depending on the cpu's native arithmetic size
#define pb_7f (~0UL / 255 * 0x7f)
#define pb_80 (~0UL / 255 * 0x80)
#define pb_7f (~(uint_native)0 / 255 * 0x7f)
#define pb_80 (~(uint_native)0 / 255 * 0x80)
static void diff_bytes_c(uint8_t *dst, const uint8_t *src1, const uint8_t *src2, intptr_t w)
{
long i;
#if !HAVE_FAST_UNALIGNED
if (((long)src1 | (long)src2) & (sizeof(long) - 1)) {
if (((uintptr_t)src1 | (uintptr_t)src2) & (sizeof(uint_native) - 1)) {
for (i = 0; i + 7 < w; i += 8) {
dst[i + 0] = src1[i + 0] - src2[i + 0];
dst[i + 1] = src1[i + 1] - src2[i + 1];
@ -43,11 +55,10 @@ static void diff_bytes_c(uint8_t *dst, const uint8_t *src1, const uint8_t *src2,
}
} else
#endif
for (i = 0; i <= w - (int) sizeof(long); i += sizeof(long)) {
long a = *(long *) (src1 + i);
long b = *(long *) (src2 + i);
*(long *) (dst + i) = ((a | pb_80) - (b & pb_7f)) ^
((a ^ b ^ pb_80) & pb_80);
for (i = 0; i <= w - (int) sizeof(uint_native); i += sizeof(uint_native)) {
uint_native a = READA(src1 + i);
uint_native b = READ(src2 + i);
WRITEA(dst + i, ((a | pb_80) - (b & pb_7f)) ^ ((a ^ b ^ pb_80) & pb_80));
}
for (; i < w; i++)
dst[i + 0] = src1[i + 0] - src2[i + 0];