commonlib/lz4_wrapper.c: do not use bitfields

Order of bits in bitfields is implementation-defined. This makes them
non-portable, especially across systems using different endianness.

This change removes bitfields and uses masking and shifting instead.

Signed-off-by: Krystian Hebel <krystian.hebel@3mdeb.com>
Change-Id: Ief7d87ddb25c9baa931f27dbd54a4ca730b6ece7
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55040
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

1 files changed, 33 insertions, 39 deletions

diff --git a/src/commonlib/bsd/lz4_wrapper.c b/src/commonlib/bsd/lz4_wrapper.c
index 73185a50515d..73a3571470cc 100644
--- a/src/commonlib/bsd/lz4_wrapper.c
+++ b/src/commonlib/bsd/lz4_wrapper.c
@@ -63,39 +63,32 @@ typedef uint64_t U64;
 
 #define LZ4F_MAGICNUMBER 0x184D2204
 
+/* Bit field endianness is implementation-defined. Use masks instead.
+ * https://stackoverflow.com/a/6044223 */
+#define RESERVED0		0x03
+#define HAS_CONTENT_CHECKSUM	0x04
+#define HAS_CONTENT_SIZE	0x08
+#define HAS_BLOCK_CHECKSUM	0x10
+#define INDEPENDENT_BLOCKS	0x20
+#define VERSION			0xC0
+#define VERSION_SHIFT		6
+
+#define RESERVED1_2		0x8F
+#define MAX_BLOCK_SIZE		0x70
+
 struct lz4_frame_header {
 	uint32_t magic;
-	union {
-		uint8_t flags;
-		struct {
-			uint8_t reserved0		: 2;
-			uint8_t has_content_checksum	: 1;
-			uint8_t has_content_size	: 1;
-			uint8_t has_block_checksum	: 1;
-			uint8_t independent_blocks	: 1;
-			uint8_t version			: 2;
-		};
-	};
-	union {
-		uint8_t block_descriptor;
-		struct {
-			uint8_t reserved1		: 4;
-			uint8_t max_block_size		: 3;
-			uint8_t reserved2		: 1;
-		};
-	};
+	uint8_t flags;
+	uint8_t block_descriptor;
 	/* + uint64_t content_size iff has_content_size is set */
 	/* + uint8_t header_checksum */
 } __packed;
 
+#define BH_SIZE			0x7FFFFFFF
+#define NOT_COMPRESSED		0x80000000
+
 struct lz4_block_header {
-	union {
-		uint32_t raw;
-		struct {
-			uint32_t size		: 31;
-			uint32_t not_compressed	: 1;
-		};
-	};
+	uint32_t raw;
 	/* + size bytes of data */
 	/* + uint32_t block_checksum iff has_block_checksum is set */
 } __packed;
@@ -114,16 +107,17 @@ size_t ulz4fn(const void *src, size_t srcn, void *dst, size_t dstn)
 			return 0;	/* input overrun */
 
 		/* We assume there's always only a single, standard frame. */
-		if (le32toh(h->magic) != LZ4F_MAGICNUMBER || h->version != 1)
+		if (le32toh(h->magic) != LZ4F_MAGICNUMBER
+		    || (h->flags & VERSION) != (1 << VERSION_SHIFT))
 			return 0;	/* unknown format */
-		if (h->reserved0 || h->reserved1 || h->reserved2)
+		if ((h->flags & RESERVED0) || (h->block_descriptor & RESERVED1_2))
 			return 0;	/* reserved must be zero */
-		if (!h->independent_blocks)
+		if (!(h->flags & INDEPENDENT_BLOCKS))
 			return 0;	/* we don't support block dependency */
-		has_block_checksum = h->has_block_checksum;
+		has_block_checksum = h->flags & HAS_BLOCK_CHECKSUM;
 
 		in += sizeof(*h);
-		if (h->has_content_size)
+		if (h->flags & HAS_CONTENT_SIZE)
 			in += sizeof(uint64_t);
 		in += sizeof(uint8_t);
 	}
@@ -133,28 +127,28 @@ size_t ulz4fn(const void *src, size_t srcn, void *dst, size_t dstn)
 			break;          /* input overrun */
 
 		struct lz4_block_header b = {
-			{ .raw = le32toh(*(const uint32_t *)in) }
+			.raw = le32toh(*(const uint32_t *)in)
 		};
 		in += sizeof(struct lz4_block_header);
 
-		if ((size_t)(in - src) + b.size > srcn)
+		if ((size_t)(in - src) + (b.raw & BH_SIZE) > srcn)
 			break;			/* input overrun */
 
-		if (!b.size) {
+		if (!(b.raw & BH_SIZE)) {
 			out_size = out - dst;
 			break;			/* decompression successful */
 		}
 
-		if (b.not_compressed) {
-			size_t size = MIN((uintptr_t)b.size, (uintptr_t)dst
+		if (b.raw & NOT_COMPRESSED) {
+			size_t size = MIN((uintptr_t)(b.raw & BH_SIZE), (uintptr_t)dst
 				+ dstn - (uintptr_t)out);
 			memcpy(out, in, size);
-			if (size < b.size)
+			if (size < (b.raw & BH_SIZE))
 				break;		/* output overrun */
 			out += size;
 		} else {
 			/* constant folding essential, do not touch params! */
-			int ret = LZ4_decompress_generic(in, out, b.size,
+			int ret = LZ4_decompress_generic(in, out, (b.raw & BH_SIZE),
 					dst + dstn - out, endOnInputSize,
 					full, 0, noDict, out, NULL, 0);
 			if (ret < 0)
@@ -162,7 +156,7 @@ size_t ulz4fn(const void *src, size_t srcn, void *dst, size_t dstn)
 			out += ret;
 		}
 
-		in += b.size;
+		in += (b.raw & BH_SIZE);
 		if (has_block_checksum)
 			in += sizeof(uint32_t);
 	}