From: Thomas Weißschuh <thomas@t-8ch.de>
Date: Thu, 27 Feb 2025 17:16:01 +0000 (+0100)
Subject: libc/crc32: make fill value of excluded area configurable
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=977dd748c53a24c01ed23d3be65f6489130795fc;p=thirdparty%2Futil-linux.git

libc/crc32: make fill value of excluded area configurable

A new user of crc32_exclude_offset() is going to be added which requires
a different fill value than the currently hardcoded "0".

Add a parameter where each caller can specify their own value.

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
---

diff --git a/include/crc32.h b/include/crc32.h
index 0d34da0d2..c78d291b0 100644
--- a/include/crc32.h
+++ b/include/crc32.h
@@ -10,7 +10,8 @@
 
 extern uint32_t ul_crc32(uint32_t seed, const unsigned char *buf, size_t len);
 extern uint32_t ul_crc32_exclude_offset(uint32_t seed, const unsigned char *buf, size_t len,
-		                              size_t exclude_off, size_t exclude_len);
+		                              size_t exclude_off, size_t exclude_len,
+					      uint8_t exclude_fill);
 
 #endif
 
diff --git a/lib/crc32.c b/lib/crc32.c
index 824693d01..b62b9f638 100644
--- a/lib/crc32.c
+++ b/lib/crc32.c
@@ -122,7 +122,7 @@ uint32_t ul_crc32(uint32_t seed, const unsigned char *buf, size_t len)
 }
 
 uint32_t ul_crc32_exclude_offset(uint32_t seed, const unsigned char *buf, size_t len,
-			      size_t exclude_off, size_t exclude_len)
+			      size_t exclude_off, size_t exclude_len, uint8_t exclude_fill)
 {
 	uint32_t crc = seed;
 	const unsigned char *p = buf;
@@ -132,7 +132,7 @@ uint32_t ul_crc32_exclude_offset(uint32_t seed, const unsigned char *buf, size_t
 		unsigned char x = *p++;
 
 		if (i >= exclude_off && i < exclude_off + exclude_len)
-			x = 0;
+			x = exclude_fill;
 
 		crc = crc32_add_char(crc, x);
 	}
diff --git a/libblkid/src/partitions/gpt.c b/libblkid/src/partitions/gpt.c
index a8846be21..dc5bcf3aa 100644
--- a/libblkid/src/partitions/gpt.c
+++ b/libblkid/src/partitions/gpt.c
@@ -106,7 +106,7 @@ struct gpt_entry {
 static inline uint32_t count_crc32(const unsigned char *buf, size_t len,
 				   size_t exclude_off, size_t exclude_len)
 {
-	return (ul_crc32_exclude_offset(~0L, buf, len, exclude_off, exclude_len) ^ ~0L);
+	return (ul_crc32_exclude_offset(~0L, buf, len, exclude_off, exclude_len, 0) ^ ~0L);
 }
 
 static inline const unsigned char *get_lba_buffer(blkid_probe pr,
diff --git a/libblkid/src/superblocks/cramfs.c b/libblkid/src/superblocks/cramfs.c
index 6a8731f7b..d9f3ed19d 100644
--- a/libblkid/src/superblocks/cramfs.c
+++ b/libblkid/src/superblocks/cramfs.c
@@ -64,7 +64,7 @@ static int cramfs_verify_csum(blkid_probe pr, const struct blkid_idmag *mag,
 
 	crc = ~ul_crc32_exclude_offset(~0LL, csummed, csummed_size,
 			offsetof(struct cramfs_super, info.crc),
-			sizeof_member(struct cramfs_super, info.crc));
+			sizeof_member(struct cramfs_super, info.crc), 0);
 
 	return blkid_probe_verify_csum(pr, crc, expected);
 }
diff --git a/libblkid/src/superblocks/zonefs.c b/libblkid/src/superblocks/zonefs.c
index e8fcab34f..8534e2ffe 100644
--- a/libblkid/src/superblocks/zonefs.c
+++ b/libblkid/src/superblocks/zonefs.c
@@ -54,7 +54,7 @@ static int zonefs_verify_csum(blkid_probe pr, const struct zonefs_super *sb)
 	uint32_t expected = le32_to_cpu(sb->s_crc);
 	uint32_t crc = ul_crc32_exclude_offset(
 			~0LL, (unsigned char *) sb, sizeof(*sb),
-		       offsetof(__typeof__(*sb), s_crc), sizeof(sb->s_crc));
+		       offsetof(__typeof__(*sb), s_crc), sizeof(sb->s_crc), 0);
 	return blkid_probe_verify_csum(pr, crc, expected);
 }
 
diff --git a/libfdisk/src/gpt.c b/libfdisk/src/gpt.c
index 374246ce6..2f850fa8a 100644
--- a/libfdisk/src/gpt.c
+++ b/libfdisk/src/gpt.c
@@ -1043,7 +1043,7 @@ fail:
 static inline uint32_t count_crc32(const unsigned char *buf, size_t len,
 				   size_t ex_off, size_t ex_len)
 {
-	return (ul_crc32_exclude_offset(~0L, buf, len, ex_off, ex_len) ^ ~0L);
+	return (ul_crc32_exclude_offset(~0L, buf, len, ex_off, ex_len, 0) ^ ~0L);
 }
 
 static inline uint32_t gpt_header_count_crc32(struct gpt_header *header)