erofs-utils: Provide identical functionality without libuuid

The motivation is to have standalone (statically linked) erofs binaries
for simple initrd images, that are nevertheless able to (re)create
erofs images with a given UUID.

For this reason a few of libuuid functions have implementations added
directly in erofs-utils.
A header liberofs_uuid.h provides the new functions, which are
always available. A further sideeffect is that code can be simplified
which calls into this functionality.

The uuid_unparse function replacement is always a private
implementation and split into its own file, this further restricts
the (optional) dependency on libuuid only to the erofs-mkfs tool.

Signed-off-by: Norbert Lange <nolange79@gmail.com>
Link: https://lore.kernel.org/r/20230703215803.4476-1-nolange79@gmail.com
[ Gao Xiang: a getrandom() fix since it was added in glibc 2.25. ]
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

10 files changed, 165 insertions, 33 deletions

diff --git a/configure.ac b/configure.ac
index cd6be4a..54608fb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -178,6 +178,7 @@ AC_CHECK_HEADERS(m4_flatten([
 	string.h
 	sys/ioctl.h
 	sys/mman.h
+	sys/random.h
 	sys/stat.h
 	sys/sysmacros.h
 	sys/time.h
diff --git a/dump/Makefile.am b/dump/Makefile.am
index c2bef6d..90227a5 100644
--- a/dump/Makefile.am
+++ b/dump/Makefile.am
@@ -7,4 +7,4 @@ AM_CPPFLAGS = ${libuuid_CFLAGS}
 dump_erofs_SOURCES = main.c
 dump_erofs_CFLAGS = -Wall -I$(top_srcdir)/include
 dump_erofs_LDADD = $(top_builddir)/lib/liberofs.la ${libselinux_LIBS} \
-	${libuuid_LIBS} ${liblz4_LIBS} ${liblzma_LIBS}
+	${liblz4_LIBS} ${liblzma_LIBS}
diff --git a/dump/main.c b/dump/main.c
index ae1ffa0..7e75719 100644
--- a/dump/main.c
+++ b/dump/main.c
@@ -17,10 +17,8 @@
 #include "erofs/compress.h"
 #include "erofs/fragments.h"
 #include "../lib/liberofs_private.h"
+#include "../lib/liberofs_uuid.h"
 
-#ifdef HAVE_LIBUUID
-#include <uuid.h>
-#endif
 
 struct erofsdump_cfg {
 	unsigned int totalshow;
@@ -593,7 +591,7 @@ static void erofsdump_print_statistic(void)
 static void erofsdump_show_superblock(void)
 {
 	time_t time = sbi.build_time;
-	char uuid_str[37] = "not available";
+	char uuid_str[37];
 	int i = 0;
 
 	fprintf(stdout, "Filesystem magic number:                      0x%04X\n",
@@ -621,9 +619,7 @@ static void erofsdump_show_superblock(void)
 		if (feat & feature_lists[i].flag)
 			fprintf(stdout, "%s ", feature_lists[i].name);
 	}
-#ifdef HAVE_LIBUUID
-	uuid_unparse_lower(sbi.uuid, uuid_str);
-#endif
+	erofs_uuid_unparse_lower(sbi.uuid, uuid_str);
 	fprintf(stdout, "\nFilesystem UUID:                              %s\n",
 			uuid_str);
 }
diff --git a/fsck/Makefile.am b/fsck/Makefile.am
index 9366a9d..369cb2f 100644
--- a/fsck/Makefile.am
+++ b/fsck/Makefile.am
@@ -7,7 +7,7 @@ AM_CPPFLAGS = ${libuuid_CFLAGS}
 fsck_erofs_SOURCES = main.c
 fsck_erofs_CFLAGS = -Wall -I$(top_srcdir)/include
 fsck_erofs_LDADD = $(top_builddir)/lib/liberofs.la ${libselinux_LIBS} \
-	${libuuid_LIBS} ${liblz4_LIBS} ${liblzma_LIBS}
+	${liblz4_LIBS} ${liblzma_LIBS}
 
 if ENABLE_FUZZING
 noinst_PROGRAMS   = fuzz_erofsfsck
@@ -15,5 +15,5 @@ fuzz_erofsfsck_SOURCES = main.c
 fuzz_erofsfsck_CFLAGS = -Wall -I$(top_srcdir)/include -DFUZZING
 fuzz_erofsfsck_LDFLAGS = -fsanitize=address,fuzzer
 fuzz_erofsfsck_LDADD = $(top_builddir)/lib/liberofs.la ${libselinux_LIBS} \
-	${libuuid_LIBS} ${liblz4_LIBS} ${liblzma_LIBS}
+	${liblz4_LIBS} ${liblzma_LIBS}
 endif
diff --git a/lib/Makefile.am b/lib/Makefile.am
index faa7311..e243c1c 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -29,9 +29,9 @@ noinst_HEADERS += compressor.h
 liberofs_la_SOURCES = config.c io.c cache.c super.c inode.c xattr.c exclude.c \
 		      namei.c data.c compress.c compressor.c zmap.c decompress.c \
 		      compress_hints.c hashmap.c sha256.c blobchunk.c dir.c \
-		      fragments.c rb_tree.c dedupe.c
+		      fragments.c rb_tree.c dedupe.c uuid_unparse.c uuid.c
 
-liberofs_la_CFLAGS = -Wall -I$(top_srcdir)/include
+liberofs_la_CFLAGS = -Wall ${libuuid_CFLAGS} -I$(top_srcdir)/include
 if ENABLE_LZ4
 liberofs_la_CFLAGS += ${LZ4_CFLAGS}
 liberofs_la_SOURCES += compressor_lz4.c
diff --git a/lib/liberofs_uuid.h b/lib/liberofs_uuid.h
new file mode 100644
index 0000000..63b358a
--- /dev/null
+++ b/lib/liberofs_uuid.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0 */
+#ifndef __EROFS_LIB_UUID_H
+#define __EROFS_LIB_UUID_H
+
+void erofs_uuid_generate(unsigned char *out);
+void erofs_uuid_unparse_lower(const unsigned char *buf, char *out);
+int erofs_uuid_parse(const char *in, unsigned char *uu);
+
+#endif
diff --git a/lib/uuid.c b/lib/uuid.c
new file mode 100644
index 0000000..ec0f9d9
--- /dev/null
+++ b/lib/uuid.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0
+/*
+ * Copyright (C) 2023 Norbert Lange <nolange79@gmail.com>
+ */
+
+#include <string.h>
+#include <errno.h>
+
+#include "erofs/config.h"
+#include "erofs/defs.h"
+#include "liberofs_uuid.h"
+
+#ifdef HAVE_LIBUUID
+#include <uuid.h>
+#else
+
+#include <stdlib.h>
+#ifdef HAVE_SYS_RANDOM_H
+#include <sys/random.h>
+#else
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <sys/syscall.h>
+#endif
+
+/* Flags to be used, will be modified if kernel does not support them */
+static unsigned int erofs_grnd_flag =
+#ifdef GRND_INSECURE
+	GRND_INSECURE;
+#else
+	0x0004;
+#endif
+
+static int s_getrandom(void *out, unsigned size, bool insecure)
+{
+	unsigned int kflags = erofs_grnd_flag;
+	unsigned int flags = insecure ? kflags : 0;
+
+	for (;;)
+	{
+#ifdef HAVE_SYS_RANDOM_H
+		ssize_t r = getrandom(out, size, flags);
+#else
+		ssize_t r = (ssize_t)syscall(__NR_getrandom, out, size, flags);
+#endif
+		int err;
+
+		if (r == size)
+			break;
+		err = errno;
+		if (err != EINTR) {
+			if (err == EINVAL && kflags) {
+				// Kernel likely does not support GRND_INSECURE
+				erofs_grnd_flag = 0;
+				kflags = 0;
+				continue;
+			}
+			return -err;
+		}
+	}
+	return 0;
+}
+#endif
+
+void erofs_uuid_generate(unsigned char *out)
+{
+#ifdef HAVE_LIBUUID
+	uuid_t new_uuid;
+
+	do {
+		uuid_generate(new_uuid);
+	} while (uuid_is_null(new_uuid));
+#else
+	unsigned char new_uuid[16];
+	int res __maybe_unused;
+
+	res = s_getrandom(new_uuid, sizeof(new_uuid), true);
+	BUG_ON(res != 0);
+
+	// UID type + version bits
+	new_uuid[0] = (new_uuid[4 + 2] & 0x0f) | 0x40;
+	new_uuid[1] = (new_uuid[4 + 2 + 2] & 0x3f) | 0x80;
+#endif
+	memcpy(out, new_uuid, sizeof(new_uuid));
+}
+
+int erofs_uuid_parse(const char *in, unsigned char *uu) {
+#ifdef HAVE_LIBUUID
+	return uuid_parse((char *)in, uu);
+#else
+	unsigned char new_uuid[16];
+	unsigned int hypens = ((1U << 3) | (1U << 5) | (1U << 7) | (1U << 9));
+	int i;
+
+	for (i = 0; i < sizeof(new_uuid); hypens >>= 1, i++)
+	{
+		char c[] = { in[0], in[1], '\0' };
+		char* endptr = c;
+		unsigned long val = strtoul(c, &endptr, 16);
+
+		if (endptr - c != 2)
+			return -EINVAL;
+
+		in += 2;
+
+		if ((hypens & 1U) != 0) {
+			if (*in++ != '-')
+				return -EINVAL;
+		}
+		new_uuid[i] = (unsigned char)val;
+	}
+
+	if (*in != '\0')
+		return -EINVAL;
+	memcpy(uu, new_uuid, sizeof(new_uuid));
+	return 0;
+#endif
+}
diff --git a/lib/uuid_unparse.c b/lib/uuid_unparse.c
new file mode 100644
index 0000000..3255c4b
--- /dev/null
+++ b/lib/uuid_unparse.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0
+/*
+ * Copyright (C) 2023 Norbert Lange <nolange79@gmail.com>
+ */
+
+#include <stdio.h>
+
+#include "erofs/config.h"
+#include "liberofs_uuid.h"
+
+void erofs_uuid_unparse_lower(const unsigned char *buf, char *out) {
+	sprintf(out, "%04x%04x-%04x-%04x-%04x-%04x%04x%04x",
+			(buf[0] << 8) | buf[1],
+			(buf[2] << 8) | buf[3],
+			(buf[4] << 8) | buf[5],
+			(buf[6] << 8) | buf[7],
+			(buf[8] << 8) | buf[9],
+			(buf[10] << 8) | buf[11],
+			(buf[12] << 8) | buf[13],
+			(buf[14] << 8) | buf[15]);
+}
diff --git a/mkfs/Makefile.am b/mkfs/Makefile.am
index 709d9bf..a08dc53 100644
--- a/mkfs/Makefile.am
+++ b/mkfs/Makefile.am
@@ -2,8 +2,8 @@
 
 AUTOMAKE_OPTIONS = foreign
 bin_PROGRAMS     = mkfs.erofs
-AM_CPPFLAGS = ${libuuid_CFLAGS} ${libselinux_CFLAGS}
+AM_CPPFLAGS = ${libselinux_CFLAGS}
 mkfs_erofs_SOURCES = main.c
 mkfs_erofs_CFLAGS = -Wall -I$(top_srcdir)/include
-mkfs_erofs_LDADD = ${libuuid_LIBS} $(top_builddir)/lib/liberofs.la ${libselinux_LIBS} \
-	${liblz4_LIBS} ${liblzma_LIBS}
+mkfs_erofs_LDADD = $(top_builddir)/lib/liberofs.la ${libselinux_LIBS} \
+	${libuuid_LIBS} ${liblz4_LIBS} ${liblzma_LIBS}
diff --git a/mkfs/main.c b/mkfs/main.c
index ac208e5..438bab8 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -26,10 +26,7 @@
 #include "erofs/blobchunk.h"
 #include "erofs/fragments.h"
 #include "../lib/liberofs_private.h"
-
-#ifdef HAVE_LIBUUID
-#include <uuid.h>
-#endif
+#include "../lib/liberofs_uuid.h"
 
 #define EROFS_SUPER_END (EROFS_SUPER_OFFSET + sizeof(struct erofs_super_block))
 
@@ -92,9 +89,7 @@ static void usage(void)
 	      " -EX[,...]             X=extended options\n"
 	      " -L volume-label       set the volume label (maximum 16)\n"
 	      " -T#                   set a fixed UNIX timestamp # to all files\n"
-#ifdef HAVE_LIBUUID
 	      " -UX                   use a given filesystem UUID\n"
-#endif
 	      " --all-root            make all files owned by root\n"
 	      " --blobdev=X           specify an extra device X to store chunked data\n"
 	      " --chunksize=#         generate chunk-based files with #-byte chunks\n"
@@ -336,14 +331,12 @@ static int mkfs_parse_options_cfg(int argc, char *argv[])
 			}
 			cfg.c_timeinherit = TIMESTAMP_FIXED;
 			break;
-#ifdef HAVE_LIBUUID
 		case 'U':
-			if (uuid_parse(optarg, sbi.uuid)) {
+			if (erofs_uuid_parse(optarg, sbi.uuid)) {
 				erofs_err("invalid UUID %s", optarg);
 				return -EINVAL;
 			}
 			break;
-#endif
 		case 2:
 			opt = erofs_parse_exclude_path(optarg, false);
 			if (opt) {
@@ -676,11 +669,7 @@ static void erofs_mkfs_default_options(void)
 			     EROFS_FEATURE_COMPAT_MTIME;
 
 	/* generate a default uuid first */
-#ifdef HAVE_LIBUUID
-	do {
-		uuid_generate(sbi.uuid);
-	} while (uuid_is_null(sbi.uuid));
-#endif
+	erofs_uuid_generate(sbi.uuid);
 }
 
 /* https://reproducible-builds.org/specs/source-date-epoch/ for more details */
@@ -725,7 +714,7 @@ int main(int argc, char **argv)
 	struct stat st;
 	erofs_blk_t nblocks;
 	struct timeval t;
-	char uuid_str[37] = "not available";
+	char uuid_str[37];
 	FILE *packedfile = NULL;
 
 	erofs_init_configure();
@@ -869,9 +858,7 @@ int main(int argc, char **argv)
 			  erofs_strerror(err));
 		goto exit;
 	}
-#ifdef HAVE_LIBUUID
-	uuid_unparse_lower(sbi.uuid, uuid_str);
-#endif
+	erofs_uuid_unparse_lower(sbi.uuid, uuid_str);
 	erofs_info("filesystem UUID: %s", uuid_str);
 
 	erofs_inode_manager_init();