Write: record used composefs version in erofs image and allow reading…

… it back

Signed-off-by: Alexander Larsson <[email protected]>

libcomposefs/lcfs-erofs.h

@@ -30,7 +30,8 @@ struct lcfs_erofs_header_s {
 	uint32_t magic;
 	uint32_t version;
 	uint32_t flags;
-	uint32_t unused[5];
+	uint32_t composefs_version;
+	uint32_t unused[4];
 } __attribute__((__packed__));
 
 #endif

libcomposefs/lcfs-writer-erofs.c

@@ -1316,6 +1316,7 @@ int lcfs_write_erofs_to(struct lcfs_ctx_s *ctx)
 	struct lcfs_erofs_header_s header = {
 		.magic = lcfs_u32_to_file(LCFS_EROFS_MAGIC),
 		.version = lcfs_u32_to_file(LCFS_EROFS_VERSION),
+		.composefs_version = lcfs_u32_to_file(ctx->options->version),
 	};
 	uint32_t header_flags;
 	struct erofs_super_block superblock = {

libcomposefs/lcfs-writer.c

@@ -22,6 +22,7 @@
 #include "lcfs-writer.h"
 #include "lcfs-utils.h"
 #include "lcfs-fsverity.h"
+#include "lcfs-erofs.h"
 #include "hash.h"
 
 #include <errno.h>
@@ -680,6 +681,24 @@ struct lcfs_node_s *lcfs_load_node_from_file(int dirfd, const char *fname,
 	return steal_pointer(&ret);
 }
 
+int lcfs_version_from_fd(int fd)
+{
+	struct lcfs_erofs_header_s *header;
+
+	header = mmap(0, sizeof(struct lcfs_erofs_header_s), PROT_READ,
+		      MAP_PRIVATE, fd, 0);
+	if (header == MAP_FAILED) {
+		return -1;
+	}
+	if (lcfs_u32_from_file(header->magic) != LCFS_EROFS_MAGIC ||
+	    lcfs_u32_from_file(header->version) != LCFS_EROFS_VERSION) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	return lcfs_u32_from_file(header->composefs_version);
+}
+
 struct lcfs_node_s *lcfs_load_node_from_fd(int fd)
 {
 	struct lcfs_node_s *node;

libcomposefs/lcfs-writer.h

@@ -78,6 +78,7 @@ LCFS_EXTERN struct lcfs_node_s *lcfs_load_node_from_file(int dirfd, const char *
 LCFS_EXTERN struct lcfs_node_s *lcfs_load_node_from_image(const uint8_t *image_data,
 							  size_t image_data_size);
 LCFS_EXTERN struct lcfs_node_s *lcfs_load_node_from_fd(int fd);
+LCFS_EXTERN int lcfs_version_from_fd(int fd);
 
 LCFS_EXTERN const char *lcfs_node_get_xattr(struct lcfs_node_s *node,
 					    const char *name, size_t *length);

tests/assets/special_v1.dump.sha256

@@ -1 +1 @@
-ee8028939ca3151a50bbbbd377c52c46ab183013610c8909e624840bf496975f
+2b1dfb9ffe6938cb3134c339059572e38cbd8cc515d54758fdff55cad5a37427

tests/test-checksums.sh

@@ -48,7 +48,7 @@ for format in erofs ; do
         fi
 
         # Ensure dump reproduces the same file
-        ${VALGRIND_PREFIX} ${BINDIR}/composefs-dump $tmpfile $tmpfile2 $VERSION
+        ${VALGRIND_PREFIX} ${BINDIR}/composefs-dump $tmpfile $tmpfile2
         if ! cmp $tmpfile $tmpfile2; then
             echo Dump is not reproducible
             exit 1

tools/composefs-dump.c

@@ -43,12 +43,11 @@ static ssize_t write_cb(void *_file, void *buf, size_t count)
 int main(int argc, char **argv)
 {
 	const char *bin = argv[0];
-	int fd;
+	int fd, version;
 	struct lcfs_node_s *root;
 	const char *src_path = NULL;
 	const char *dst_path = NULL;
 	struct lcfs_write_options_s options = { 0 };
-	int format_version = LCFS_VERSION_MAX;
 
 	if (argc <= 1) {
 		fprintf(stderr, "No source path specified\n");
@@ -64,15 +63,16 @@ int main(int argc, char **argv)
 	}
 	dst_path = argv[2];
 
-	if (argc > 3) {
-		format_version = atoi(argv[3]);
-	}
-
 	fd = open(src_path, O_RDONLY | O_CLOEXEC);
 	if (fd < 0) {
 		err(EXIT_FAILURE, "Failed to open '%s'", src_path);
 	}
 
+	version = lcfs_version_from_fd(fd);
+	if (version < 0) {
+		err(EXIT_FAILURE, "Failed to get image version '%s'", src_path);
+	}
+
 	root = lcfs_load_node_from_fd(fd);
 	if (root == NULL) {
 		err(EXIT_FAILURE, "Failed to load '%s'", src_path);
@@ -81,7 +81,7 @@ int main(int argc, char **argv)
 	close(fd);
 
 	options.format = LCFS_FORMAT_EROFS;
-	options.version = format_version;
+	options.version = version;
 
 	FILE *out_file = fopen(dst_path, "we");
 	if (out_file == NULL)