From: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Date: Sat, 31 May 2025 11:43:32 +0000 (+0200)
Subject: random-seed: do not include file name directly in error messages
X-Git-Tag: v258-rc1~421^2~6
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=53059edcb443825603494b4129aa9db6a120f033;p=thirdparty%2Fsystemd.git

random-seed: do not include file name directly in error messages

The path is fairly long and by embedding it in the message, we get a longer
data section in our binary. By using %s, we can make the template strings
shorter, deduplicating bytes in our binary. Those are error messages, i.e. by
definition they are only used very rarely, so it's completely fine if printf
does a bit more work when generating the message.

$ strings build/systemd-random-seed.0 | rg '/var/lib/systemd/random-seed'
/var/lib/systemd/random-seed
Failed to open /var/lib/systemd/random-seed for writing: %m
Failed to open /var/lib/systemd/random-seed for reading: %m
Failed to open /var/lib/systemd/random-seed: %m
Failed to stat() seed file /var/lib/systemd/random-seed: %m
Failed to read seed from /var/lib/systemd/random-seed: %m
Seed file /var/lib/systemd/random-seed not yet initialized, proceeding.

$ strings build/systemd-random-seed | rg '/var/lib/systemd/random-seed'
/var/lib/systemd/random-seed

$ ls -l build/systemd-random-seed{,.0}
-rwxr-xr-x 1 zbyszek zbyszek 68872 May 31 13:39 build/systemd-random-seed.0
-rwxr-xr-x 1 zbyszek zbyszek 64912 May 31 13:45 build/systemd-random-seed
That's a ~6% smaller binary!
---

diff --git a/src/random-seed/random-seed-tool.c b/src/random-seed/random-seed-tool.c
index 536d1b037da..a99df0e08e4 100644
--- a/src/random-seed/random-seed-tool.c
+++ b/src/random-seed/random-seed-tool.c
@@ -102,12 +102,14 @@ static CreditEntropy may_credit(int seed_fd) {
 
 static int random_seed_size(int seed_fd, size_t *ret_size) {
         struct stat st;
+        int r;
 
         assert(ret_size);
         assert(seed_fd >= 0);
 
-        if (fstat(seed_fd, &st) < 0)
-                return log_error_errno(errno, "Failed to stat() seed file " RANDOM_SEED ": %m");
+        r = RET_NERRNO(fstat(seed_fd, &st));
+        if (r < 0)
+                return log_error_errno(r, "Failed to stat seed file %s: %m", RANDOM_SEED);
 
         /* If the seed file is larger than what the kernel expects, then honour the existing size and
          * save/restore as much as it says */
@@ -157,11 +159,11 @@ static int load_seed_file(
 
         k = loop_read(seed_fd, buf, seed_size, false);
         if (k < 0) {
-                log_warning_errno(k, "Failed to read seed from " RANDOM_SEED ": %m");
+                log_warning_errno(k, "Failed to read seed from %s: %m", RANDOM_SEED);
                 return 0;
         }
         if (k == 0) {
-                log_debug("Seed file " RANDOM_SEED " not yet initialized, proceeding.");
+                log_debug("Seed file %s not yet initialized, proceeding.", RANDOM_SEED);
                 return 0;
         }
 
@@ -384,11 +386,11 @@ static int run(int argc, char *argv[]) {
 
         r = mkdir_parents(RANDOM_SEED, 0755);
         if (r < 0)
-                return log_error_errno(r, "Failed to create directory " RANDOM_SEED_DIR ": %m");
+                return log_error_errno(r, "Failed to create directory %s: %m", RANDOM_SEED);
 
         random_fd = open("/dev/urandom", O_RDWR|O_CLOEXEC|O_NOCTTY);
         if (random_fd < 0)
-                return log_error_errno(errno, "Failed to open /dev/urandom: %m");
+                return log_error_errno(errno, "Failed to open %s: %m", "/dev/urandom");
 
         /* When we load the seed we read it and write it to the device and then immediately update the saved
          * seed with new data, to make sure the next boot gets seeded differently. */
@@ -399,20 +401,20 @@ static int run(int argc, char *argv[]) {
                  * load_machine_id() for an explanation why. */
                 load_machine_id(random_fd);
 
-                seed_fd = open(RANDOM_SEED, O_RDWR|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600);
+                seed_fd = RET_NERRNO(open(RANDOM_SEED, O_RDWR|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600));
                 if (seed_fd < 0) {
-                        int open_rw_error = -errno;
+                        int open_rw_error = seed_fd;
 
                         write_seed_file = false;
 
-                        seed_fd = open(RANDOM_SEED, O_RDONLY|O_CLOEXEC|O_NOCTTY);
+                        seed_fd = RET_NERRNO(open(RANDOM_SEED, O_RDONLY|O_CLOEXEC|O_NOCTTY));
                         if (seed_fd < 0) {
-                                bool missing = errno == ENOENT;
+                                bool missing = seed_fd == -ENOENT;
                                 int level = missing ? LOG_DEBUG : LOG_ERR;
 
-                                log_full_errno(level, open_rw_error, "Failed to open " RANDOM_SEED " for writing: %m");
-                                log_full_errno(level, errno, "Failed to open " RANDOM_SEED " for reading: %m");
-                                return missing ? 0 : -errno;
+                                log_full_errno(level, open_rw_error, "Failed to open %s for writing: %m", RANDOM_SEED);
+                                log_full_errno(level, seed_fd, "Failed to open %s for reading: %m", RANDOM_SEED);
+                                return missing ? 0 : seed_fd;
                         }
                 } else
                         write_seed_file = true;
@@ -422,9 +424,9 @@ static int run(int argc, char *argv[]) {
                 break;
 
         case ACTION_SAVE:
-                seed_fd = open(RANDOM_SEED, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600);
+                seed_fd = RET_NERRNO(open(RANDOM_SEED, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_CREAT, 0600));
                 if (seed_fd < 0)
-                        return log_error_errno(errno, "Failed to open " RANDOM_SEED ": %m");
+                        return log_error_errno(seed_fd, "Failed to open %s: %m", RANDOM_SEED);
 
                 read_seed_file = false;
                 write_seed_file = true;