tools/nolibc: support nanoseconds in stat()

Keep backwards compatibility through unions.

The compatibility macros like

 #define st_atime st_atim.tv_sec

as documented in stat(3type) don't work for nolibc because it would
break with other stat-like structures that contain the field st_atime.

The stx_atime, stx_mtime, stx_ctime are in type of 'struct
statx_timestamp', which is incompatible with 'struct timespec', should
be converted explicitly.

    /* include/uapi/linux/stat.h */

    struct statx_timestamp {
    	__s64	tv_sec;
    	__u32	tv_nsec;
    	__s32	__reserved;
    };

    /* include/uapi/linux/time.h */
    struct timespec {
    	__kernel_old_time_t	tv_sec;		/* seconds */
    	long			tv_nsec;	/* nanoseconds */
    };
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/linux-riscv/3a3edd48-1ace-4c89-89e8-9c594dd1b3c9@t-8ch.de/Co-authored-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
[wt: squashed Zhangjin & Thomas' patches into one to preserve "bisectability"]
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/include/nolibc/sys.h

@@ -1175,9 +1175,12 @@ int sys_stat(const char *path, struct stat *buf)
 	buf->st_size         = statx.stx_size;
 	buf->st_blksize      = statx.stx_blksize;
 	buf->st_blocks       = statx.stx_blocks;
-	buf->st_atime   = statx.stx_atime.tv_sec;
-	buf->st_mtime   = statx.stx_mtime.tv_sec;
-	buf->st_ctime   = statx.stx_ctime.tv_sec;
+	buf->st_atim.tv_sec  = statx.stx_atime.tv_sec;
+	buf->st_atim.tv_nsec = statx.stx_atime.tv_nsec;
+	buf->st_mtim.tv_sec  = statx.stx_mtime.tv_sec;
+	buf->st_mtim.tv_nsec = statx.stx_mtime.tv_nsec;
+	buf->st_ctim.tv_sec  = statx.stx_ctime.tv_sec;
+	buf->st_ctim.tv_nsec = statx.stx_ctime.tv_nsec;
 	return ret;
 }
 #else
@@ -1205,9 +1208,12 @@ int sys_stat(const char *path, struct stat *buf)
 	buf->st_size         = stat.st_size;
 	buf->st_blksize      = stat.st_blksize;
 	buf->st_blocks       = stat.st_blocks;
-	buf->st_atime   = stat.st_atime;
-	buf->st_mtime   = stat.st_mtime;
-	buf->st_ctime   = stat.st_ctime;
+	buf->st_atim.tv_sec  = stat.st_atime;
+	buf->st_atim.tv_nsec = stat.st_atime_nsec;
+	buf->st_mtim.tv_sec  = stat.st_mtime;
+	buf->st_mtim.tv_nsec = stat.st_mtime_nsec;
+	buf->st_ctim.tv_sec  = stat.st_ctime;
+	buf->st_ctim.tv_nsec = stat.st_ctime_nsec;
 	return ret;
 }
 #endif

tools/include/nolibc/types.h

@@ -198,9 +198,9 @@ struct stat {
 	off_t     st_size;    /* total size, in bytes */
 	blksize_t st_blksize; /* blocksize for file system I/O */
 	blkcnt_t  st_blocks;  /* number of 512B blocks allocated */
-	time_t    st_atime;   /* time of last access */
-	time_t    st_mtime;   /* time of last modification */
-	time_t    st_ctime;   /* time of last status change */
+	union { time_t st_atime; struct timespec st_atim; }; /* time of last access */
+	union { time_t st_mtime; struct timespec st_mtim; }; /* time of last modification */
+	union { time_t st_ctime; struct timespec st_ctim; }; /* time of last status change */
 };
 
 /* WARNING, it only deals with the 4096 first majors and 256 first minors */

tools/testing/selftests/nolibc/nolibc-test.c

@@ -501,6 +501,28 @@ static int test_fork(void)
 	}
 }
 
+static int test_stat_timestamps(void)
+{
+	struct stat st;
+
+	if (sizeof(st.st_atim.tv_sec) != sizeof(st.st_atime))
+		return 1;
+
+	if (stat("/proc/self/", &st))
+		return 1;
+
+	if (st.st_atim.tv_sec != st.st_atime || st.st_atim.tv_nsec > 1000000000)
+		return 1;
+
+	if (st.st_mtim.tv_sec != st.st_mtime || st.st_mtim.tv_nsec > 1000000000)
+		return 1;
+
+	if (st.st_ctim.tv_sec != st.st_ctime || st.st_ctim.tv_nsec > 1000000000)
+		return 1;
+
+	return 0;
+}
+
 /* Run syscall tests between IDs <min> and <max>.
  * Return 0 on success, non-zero on failure.
  */
@@ -589,6 +611,7 @@ int run_syscall(int min, int max)
 		CASE_TEST(select_fault);      EXPECT_SYSER(1, select(1, (void *)1, NULL, NULL, 0), -1, EFAULT); break;
 		CASE_TEST(stat_blah);         EXPECT_SYSER(1, stat("/proc/self/blah", &stat_buf), -1, ENOENT); break;
 		CASE_TEST(stat_fault);        EXPECT_SYSER(1, stat(NULL, &stat_buf), -1, EFAULT); break;
+		CASE_TEST(stat_timestamps);   EXPECT_SYSZR(1, test_stat_timestamps()); break;
 		CASE_TEST(symlink_root);      EXPECT_SYSER(1, symlink("/", "/"), -1, EEXIST); break;
 		CASE_TEST(unlink_root);       EXPECT_SYSER(1, unlink("/"), -1, EISDIR); break;
 		CASE_TEST(unlink_blah);       EXPECT_SYSER(1, unlink("/proc/self/blah"), -1, ENOENT); break;