[PATCH 13/26] bootscan: use block size for partition table probe

With 4k byte sectors, LBA1, which would contain the GPT magic string
would start at offset 4096, which is well outside the 2048 bytes that
FILE_TYPE_SAFE_BUFSIZE expands to.

Fix this by always reading at least the first two LBAs with the block
size reported by the block device.

Signed-off-by: Ahmad Fatoum <[email protected]>
---
 common/bootscan.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/common/bootscan.c b/common/bootscan.c
index 5b70024a75aa..60eeb06b65c2 100644
--- a/common/bootscan.c
+++ b/common/bootscan.c
@@ -8,6 +8,7 @@
 #include <fs.h>
 #include <linux/stat.h>
 #include <linux/err.h>
+#include <linux/minmax.h>
 #include <mtd/ubi-user.h>
 #include <uapi/spec/dps.h>
 
@@ -86,6 +87,7 @@ int boot_scan_cdev(struct bootscanner *scanner,
 		   bool autodiscover)
 {
 	int ret, found = 0;
+	unsigned int blocksize;
 	size_t bufsize, readsize;
 	void *buf;
 	enum filetype type, filetype;
@@ -98,7 +100,8 @@ int boot_scan_cdev(struct bootscanner *scanner,
 		return 0;
 	}
 
-	bufsize = FILE_TYPE_SAFE_BUFSIZE;
+	blocksize = cdev_blocksize(cdev);
+	bufsize = max_t(size_t, FILE_TYPE_SAFE_BUFSIZE, 2 * blocksize);
 
 	buf = xzalloc(bufsize);
 
@@ -110,7 +113,7 @@ int boot_scan_cdev(struct bootscanner *scanner,
 
 	readsize = ret;
 
-	type = file_detect_partition_table(buf, readsize, SECTOR_SIZE);
+	type = file_detect_partition_table(buf, readsize, blocksize);
 	filetype = file_detect_type(buf, readsize);
 	free(buf);
 
-- 
2.47.3