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unittester: Fix that one bug I wasn't going to fix

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I might as well not be a hypocrite here.
This commit is contained in:
GreaseMonkey
2024-01-08 12:59:02 +13:00
parent e5f467918c
commit 4648092b12
1 changed files with 11 additions and 15 deletions
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26
src/device/unittester.c
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@@ -75,9 +75,9 @@ struct unittester_state {
uint8_t status;
enum unittester_cmd cmd_id;
uint32_t write_offs;
uint32_t read_offs;
uint32_t write_len;
uint32_t read_len;
uint64_t read_offs;
uint64_t read_len;
/* Screen snapshot state */
/* Monitor to take snapshot on */
@@ -139,12 +139,12 @@ unittester_log(const char *fmt, ...)
#endif
static uint8_t
unittester_read_snap_rect_idx(uint32_t offs)
unittester_read_snap_rect_idx(uint64_t offs)
{
/* WARNING: If the width is somehow 0 and wasn't caught earlier, you'll probably get a divide by zero crash. */
uint32_t idx = (offs & 0x3);
int32_t x = (offs >> 2) % unittester.read_snap_width;
int32_t y = (offs >> 2) / unittester.read_snap_width;
int64_t x = (offs >> 2) % unittester.read_snap_width;
int64_t y = (offs >> 2) / unittester.read_snap_width;
x += unittester.read_snap_xoffs;
y += unittester.read_snap_yoffs;
@@ -353,22 +353,18 @@ unittester_write(uint16_t port, uint8_t val, UNUSED(void *priv))
/* Offset the X,Y offsets by the overscan offsets. */
unittester.read_snap_xoffs += (int16_t)unittester.snap_img_xoffs;
unittester.read_snap_yoffs += (int16_t)unittester.snap_img_yoffs;
/*BUG: If the width and height are too large, this ends up with a multiplication overflow.
In practice, this means we end up sending less than we would want to.
However:
- A width and height of that size is obscene, and goes beyond what one would reasonably want.
- The consequences of triggering this bug are that one ends up with a bunch of FF FF FF FF pixels.
- Special-casing this would add unnecessary complexity.
So, this bug is kept here.
If there is any need to fix this bug... then go and make the variables 64-bit :P
/* NOTE: Width * Height * 4 can potentially exceed a 32-bit number.
So, we use 64-bit numbers instead.
In practice, this will only happen if someone decides to request e.g. a 65535 x 65535 image,
of which most of the pixels will be out of range anyway.
*/
unittester.read_len = ((uint32_t)unittester.read_snap_width) * ((uint32_t)unittester.read_snap_height) * 4;
unittester.read_len = ((uint64_t)unittester.read_snap_width) * ((uint64_t)unittester.read_snap_height) * 4;
unittester.read_snap_crc = 0xFFFFFFFF;
if (unittester.cmd_id == UT_CMD_VERIFY_SCREEN_SNAPSHOT_RECTANGLE) {
/* Read everything and compute CRC */
uint32_t crc = 0xFFFFFFFF;
for (uint32_t i = 0; i < unittester.read_len; i++) {
for (uint64_t i = 0; i < unittester.read_len; i++) {
crc ^= 0xFF & (uint32_t)unittester_read_snap_rect_idx(i);
/* Use some bit twiddling until we have a table-based fast CRC-32 implementation */
for (uint32_t j = 0; j < 8; j++) {