mtd: support bad blocks within the mtd_fixtrx()

Reading MTD data with (p)read doesn't return any error when accessing
bad block. As the result, with current code, CRC32 covers "data" stored
in bad blocks.

That behavior doesn't match CFE's one (bootloader simply skips bad
blocks) and may result in:
1) Invalid CRC32
2) CFE refusing to boot firmware with a following error:
Boot program checksum is invalid

Fix that problem by checking every block before reading its content.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>

package/system/mtd/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 include $(INCLUDE_DIR)/kernel.mk
 
 PKG_NAME:=mtd
-PKG_RELEASE:=21
+PKG_RELEASE:=22
 
 PKG_BUILD_DIR := $(KERNEL_BUILD_DIR)/$(PKG_NAME)
 STAMP_PREPARED := $(STAMP_PREPARED)_$(call confvar,CONFIG_MTD_REDBOOT_PARTS)

package/system/mtd/src/trx.c

@@ -46,6 +46,12 @@ struct trx_header {
 	uint32_t offsets[3];    /* Offsets of partitions from start of header */
 };
 
+#define min(x,y) ({		\
+	typeof(x) _x = (x);	\
+	typeof(y) _y = (y);	\
+	(void) (&_x == &_y);	\
+	_x < _y ? _x : _y; })
+
 #if __BYTE_ORDER == __BIG_ENDIAN
 #define STORE32_LE(X)           ((((X) & 0x000000FF) << 24) | (((X) & 0x0000FF00) << 8) | (((X) & 0x00FF0000) >> 8) | (((X) & 0xFF000000) >> 24))
 #elif __BYTE_ORDER == __LITTLE_ENDIAN
@@ -156,7 +162,7 @@ mtd_fixtrx(const char *mtd, size_t offset, size_t data_size)
 	int fd;
 	struct trx_header *trx;
 	char *first_block;
-	char *buf;
+	char *buf, *to;
 	ssize_t res;
 	size_t block_offset;
 
@@ -214,11 +220,28 @@ mtd_fixtrx(const char *mtd, size_t offset, size_t data_size)
 		exit(1);
 	}
 
-	res = pread(fd, buf, data_size, data_offset);
-	if (res != data_size) {
-		perror("pread");
-		exit(1);
+	to = buf;
+	while (data_size) {
+		size_t read_block_offset = data_offset & ~(erasesize - 1);
+		size_t read_chunk;
+
+		read_chunk = erasesize - (data_offset & (erasesize - 1));
+		read_chunk = min(read_chunk, data_size);
+
+		/* Read from good blocks only to match CFE behavior */
+		if (!mtd_block_is_bad(fd, read_block_offset)) {
+			res = pread(fd, to, read_chunk, data_offset);
+			if (res != read_chunk) {
+				perror("pread");
+				exit(1);
+			}
+			to += read_chunk;
+		}
+
+		data_offset += read_chunk;
+		data_size -= read_chunk;
 	}
+	data_size = to - buf;
 
 	trx->len = STORE32_LE(data_size + offsetof(struct trx_header, flag_version));
 
@@ -244,4 +267,3 @@ mtd_fixtrx(const char *mtd, size_t offset, size_t data_size)
 	return 0;
 
 }
-