dediprog: Fix small, unaligned reads

This never was a use case until now but the `--fmap` code makes it
obvious: Unaligned reads that were smaller than the `chunksize` here,
were extended without considering the length of the buffer read into.

With that fixed we run into the next problem: dediprog_spi_bulk_read()
shouldn't report an error when an empty read is unaligned.

Change-Id: Ie12b62499ebfdb467d5126c00d327c76077ddead
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/30051
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
Reviewed-on: https://review.coreboot.org/c/30380
Reviewed-by: Nico Huber <nico.h@gmx.de>

1 files changed, 4 insertions, 4 deletions

diff --git a/dediprog.c b/dediprog.c
index 2f5b441f..70660d48 100644
--- a/dediprog.c
+++ b/dediprog.c
@@ -425,15 +425,15 @@ static int dediprog_spi_bulk_read(struct flashctx *flash, uint8_t *buf, unsigned
 	struct libusb_transfer *transfers[DEDIPROG_ASYNC_TRANSFERS] = { NULL, };
 	struct libusb_transfer *transfer;
 
+	if (len == 0)
+		return 0;
+
 	if ((start % chunksize) || (len % chunksize)) {
 		msg_perr("%s: Unaligned start=%i, len=%i! Please report a bug at flashrom@flashrom.org\n",
 			 __func__, start, len);
 		return 1;
 	}
 
-	if (len == 0)
-		return 0;
-
 	/* Command packet size of protocols: new 10 B, old 5 B. */
 	uint8_t data_packet[is_new_prot() ? 10 : 5];
 	unsigned int value, idx;
@@ -503,7 +503,7 @@ static int dediprog_spi_read(struct flashctx *flash, uint8_t *buf, unsigned int
 	int ret;
 	/* chunksize must be 512, other sizes will NOT work at all. */
 	const unsigned int chunksize = 0x200;
-	unsigned int residue = start % chunksize ? chunksize - start % chunksize : 0;
+	unsigned int residue = start % chunksize ? min(len, chunksize - start % chunksize) : 0;
 	unsigned int bulklen;
 
 	dediprog_set_leds(LED_BUSY);