vlibc/tests/test_stat.c

/*
 * vlibc — stat family test (todo 22).
 *
 * Exercises sys/stat.h end to end:
 *
 *   1. stat("/dev/null") reports a character device with a non-zero rdev.
 *   2. open+write a temp file, fstat shows S_ISREG with the written size;
 *      close then stat(path) agrees (and the inode matches).
 *   3. umask(0) then mkdir/mkdirat 0755/0700 — stat shows S_ISDIR with the
 *      exact requested mode; the umask is restored afterwards.
 *   4. A symlink created via raw SYS_symlink: lstat reports the link
 *      itself (S_ISLNK), stat follows it (S_ISREG); fstatat with
 *      AT_SYMLINK_NOFOLLOW does not follow.
 *   5. chmod(file, 0600) / fchmod / fchmodat update the mode.
 *   6. chown-family no-ops: fchown(fd, -1, -1) and fchownat(...,-1,-1,0)
 *      succeed without changing ownership; lchown on the symlink succeeds.
 *   7. utimensat(AT_FDCWD, file, NULL, 0) and futimens(fd, NULL) set the
 *      timestamps to the current time and return 0.
 *   8. mkfifo/mkfifoat create FIFOs (S_ISFIFO).
 *   9. Level 2: mknod/mknodat create FIFOs via S_IFIFO (no privilege
 *      needed for a FIFO).
 *
 * The -f mode runs only the failure scenarios: stat/lstat/fstatat/fstat on
 * nonexistent paths/fds, mkdir on an existing directory, mkfifo in a
 * missing directory, chmod/fchmod/fchmodat/chown/lchown/fchown/fchownat/
 * utimensat/futimens negatives, and (L2) mknod without a type bit
 * (EINVAL). Only return values are asserted — errno is never read. The
 * negative paths make the LIBRARY write errno (syscall_ret), which under
 * a host-linked binary targets glibc's private dtv slot at %fs:0+8, so -f
 * exits via raw SYS_exit_group (house pattern, tests/test_malloc.c).
 *
 * All diagnostics go through raw SYS_write (no stdio): under -Iinclude the
 * vlibc public headers shadow GCC's internal ones, so a host header would
 * not compile. Not part of the library proper; compiled manually for this
 * todo (the tests/ + make check wiring is owned by a later todo).
 */

#include <stddef.h>

#include <sys/stat.h>
#include <unistd.h>

#include "../src/internal/syscall.h"

/* Kernel-UAPI open/at flags, local to this test (include/fcntl.h is todo 21). */
#define T22_AT_FDCWD (-100)
#define T22_AT_SYMLINK_NOFOLLOW 0x100
#define T22_O_RDWR 0x2
#define T22_O_CREAT 0x40
#define T22_O_EXCL 0x80

/* Scratch paths in /tmp (test runs from an arbitrary cwd). */
#define T22_FILE "/tmp/vlibc_stat_t22_file"
#define T22_DIR "/tmp/vlibc_stat_t22_dir"
#define T22_DIR2 "/tmp/vlibc_stat_t22_dir2"
#define T22_LINK "/tmp/vlibc_stat_t22_link"
#define T22_LINK_TARGET "vlibc_stat_t22_file"
#define T22_FIFO "/tmp/vlibc_stat_t22_fifo"
#define T22_FIFO2 "/tmp/vlibc_stat_t22_fifo2"
#define T22_FIFO3 "/tmp/vlibc_stat_t22_fifo3"
#define T22_FIFO4 "/tmp/vlibc_stat_t22_fifo4"
#define T22_FDIR "/tmp/vlibc_stat_t22_fdir"
#define T22_MISSING "/nonexistent-vlibc-zzz"

static int failures;

/* Write a NUL-terminated string to fd via the raw syscall layer. The
 * optimize attribute keeps GCC from lowering the length loop into a
 * strlen call, which would leave a vlibc-owned symbol undefined in this
 * host-linked standalone binary (house idiom, see src/string). */
static __attribute__((optimize("no-tree-loop-distribute-patterns"))) void
say(int fd, const char *s)
{
    long n = 0;

    while (s[n] != '\0')
    {
        n++;
    }
    __syscall3(SYS_write, fd, (long)s, n);
}

/* Write v in decimal to fd. */
static void
say_dec(int fd, unsigned long v) // NOLINT(bugprone-easily-swappable-parameters)
{
    char buf[24];
    int i = (int)sizeof(buf);

    buf[--i] = '\0';
    if (v == 0)
    {
        buf[--i] = '0';
    }
    while (v > 0 && i > 0)
    {
        buf[--i] = (char)('0' + v % 10);
        v /= 10;
    }
    say(fd, &buf[i]);
}

static void
check(int ok, const char *msg)
{
    if (ok)
    {
        say(1, "PASS: ");
    }
    else
    {
        say(1, "FAIL: ");
        failures++;
    }
    say(1, msg);
    say(1, "\n");
}

/*
 * Host-TCB slot-1 bracket: the library's errno write on a negative path
 * lands at %fs:0+8, glibc's dtv pointer. Save and restore it around each
 * such call; only vlibc/raw-syscall code runs in between (task 13
 * technique).
 */
static unsigned long
tcb_slot1(void)
{
    return *(unsigned long *)((char *)__builtin_thread_pointer() + 8);
}

static void
tcb_slot1_set(unsigned long value)
{
    *(unsigned long *)((char *)__builtin_thread_pointer() + 8) = value;
}

/* 1. /dev/null is a character device. */
static void
dev_null_scenario(void)
{
    struct stat st = {0};

    check(sizeof(struct stat) == 144, "sizeof(struct stat) is 144");
    check(stat("/dev/null", &st) == 0, "stat(/dev/null) returns 0");
    check(S_ISCHR(st.st_mode), "st_mode classifies /dev/null as S_ISCHR");
    check(st.st_rdev != 0, "st_rdev of /dev/null is non-zero");
    check(fstatat(T22_AT_FDCWD, "/dev/null", &st, 0) == 0,
          "fstatat(AT_FDCWD, /dev/null) returns 0");
    check(S_ISCHR(st.st_mode), "fstatat st_mode classifies /dev/null as S_ISCHR");
    check(!S_ISREG(st.st_mode) && !S_ISDIR(st.st_mode) && !S_ISFIFO(st.st_mode),
          "/dev/null is not reg/dir/fifo");
}

/* 2 + 5 + 6 + 7: the temp file lifecycle. */
static void
file_scenario(void)
{
    static const char payload[] = "hello from vlibc stat\n";
    struct stat st = {0};
    struct stat st2 = {0};
    unsigned long saved;
    ssize_t wrote;
    int fd;

    fd = open(T22_FILE, T22_O_RDWR | T22_O_CREAT | T22_O_EXCL, 0644);
    check(fd >= 0, "open O_RDWR|O_CREAT|O_EXCL 0644 returns a descriptor");
    if (fd < 0)
    {
        return;
    }
    wrote = write(fd, payload, sizeof(payload) - 1);
    check(wrote == (ssize_t)(sizeof(payload) - 1), "write of 22 bytes returns 22");
    check(fstat(fd, &st) == 0, "fstat(fd) returns 0");
    check(S_ISREG(st.st_mode), "fstat st_mode classifies the file as S_ISREG");
    check(st.st_size == (off_t)(sizeof(payload) - 1), "fstat st_size equals the written bytes");
    check((st.st_mode & 0777) == 0644, "fstat st_mode permission bits are 0644 (umask(0))");
    check(st.st_nlink == 1, "fstat st_nlink is 1");
    check(st.st_atime > 0 && st.st_mtime > 0 && st.st_ctime > 0,
          "st_atime/st_mtime/st_ctime macros expose positive times");
    check(stat(T22_FILE, &st2) == 0, "stat(path) returns 0");
    check(st2.st_size == st.st_size, "stat(path) st_size matches fstat");
    check(st2.st_ino == st.st_ino, "stat(path) st_ino matches fstat");

    /* 5. chmod family. */
    check(chmod(T22_FILE, 0600) == 0, "chmod(file, 0600) returns 0");
    saved = tcb_slot1();
    check(stat(T22_FILE, &st2) == 0, "stat after chmod returns 0");
    tcb_slot1_set(saved);
    check((st2.st_mode & 0777) == 0600, "mode is 0600 after chmod");
    check(fchmod(fd, 0640) == 0, "fchmod(fd, 0640) returns 0");
    check(fchmodat(T22_AT_FDCWD, T22_FILE, 0644, 0) == 0,
          "fchmodat(AT_FDCWD, file, 0644) returns 0");
    saved = tcb_slot1();
    check(stat(T22_FILE, &st2) == 0, "stat after fchmodat returns 0");
    tcb_slot1_set(saved);
    check((st2.st_mode & 0777) == 0644, "mode is 0644 after fchmodat");

    /* 6. chown-family no-ops (-1 = leave unchanged). */
    check(fchown(fd, (uid_t)-1, (gid_t)-1) == 0, "fchown(fd, -1, -1) returns 0");
    check(fchownat(T22_AT_FDCWD, T22_FILE, (uid_t)-1, (gid_t)-1, 0) == 0,
          "fchownat(AT_FDCWD, file, -1, -1, 0) returns 0");

    /* 7. utimensat/futimens with NULL times (set to current time). */
    check(utimensat(T22_AT_FDCWD, T22_FILE, 0, 0) == 0,
          "utimensat(AT_FDCWD, file, NULL, 0) returns 0");
    check(futimens(fd, 0) == 0, "futimens(fd, NULL) returns 0");

    check(close(fd) == 0, "close of the temp file returns 0");
}

/* 3. mkdir/mkdirat with a cleared umask. */
static void
mkdir_scenario(void)
{
    struct stat st = {0};
    mode_t old;

    old = umask(0);
    check(mkdir(T22_DIR, 0755) == 0, "mkdir(dir, 0755) returns 0");
    check(mkdirat(T22_AT_FDCWD, T22_DIR2, 0700) == 0, "mkdirat(AT_FDCWD, dir2, 0700) returns 0");
    umask(old);
    check(stat(T22_DIR, &st) == 0, "stat(dir) returns 0");
    check(S_ISDIR(st.st_mode), "st_mode classifies dir as S_ISDIR");
    check((st.st_mode & 0777) == 0755, "dir mode is exactly 0755 (umask(0))");
    check(stat(T22_DIR2, &st) == 0, "stat(dir2) returns 0");
    check(S_ISDIR(st.st_mode) && (st.st_mode & 0777) == 0700, "dir2 mode is exactly 0700");
}

/* 4. symlink: lstat reports the link, stat follows. */
static void
symlink_scenario(void)
{
    struct stat st = {0};

    check(__syscall2(SYS_symlink, (long)T22_LINK_TARGET, (long)T22_LINK) == 0,
          "raw SYS_symlink creates the link");
    check(lstat(T22_LINK, &st) == 0, "lstat(link) returns 0");
    check(S_ISLNK(st.st_mode), "lstat st_mode classifies the link as S_ISLNK");
    check(!S_ISREG(st.st_mode), "lstat does not follow the link");
    check(stat(T22_LINK, &st) == 0, "stat(link) returns 0");
    check(S_ISREG(st.st_mode), "stat follows the link to S_ISREG");
    check(fstatat(T22_AT_FDCWD, T22_LINK, &st, T22_AT_SYMLINK_NOFOLLOW) == 0,
          "fstatat(link, AT_SYMLINK_NOFOLLOW) returns 0");
    check(S_ISLNK(st.st_mode), "fstatat with AT_SYMLINK_NOFOLLOW reports S_ISLNK");
    check(lchown(T22_LINK, (uid_t)-1, (gid_t)-1) == 0, "lchown(link, -1, -1) returns 0");
}

/* 8. mkfifo/mkfifoat create FIFOs. */
static void
mkfifo_scenario(void)
{
    struct stat st = {0};

    check(mkfifo(T22_FIFO, 0644) == 0, "mkfifo(fifo, 0644) returns 0");
    check(mkfifoat(T22_AT_FDCWD, T22_FIFO2, 0600) == 0,
          "mkfifoat(AT_FDCWD, fifo2, 0600) returns 0");
    check(stat(T22_FIFO, &st) == 0, "stat(fifo) returns 0");
    check(S_ISFIFO(st.st_mode), "st_mode classifies fifo as S_ISFIFO");
    check(stat(T22_FIFO2, &st) == 0, "stat(fifo2) returns 0");
    check(S_ISFIFO(st.st_mode), "st_mode classifies fifo2 as S_ISFIFO");
}

#if VLIBC_LEVEL_GE(2)
/* 9. mknod/mknodat create FIFOs (no privilege needed for S_IFIFO). */
static void
mknod_scenario(void)
{
    struct stat st = {0};

    check(mknod(T22_FIFO3, S_IFIFO | 0640, 0) == 0, "mknod(fifo3, S_IFIFO|0640, 0) returns 0");
    check(mknodat(T22_AT_FDCWD, T22_FIFO4, S_IFIFO | 0600, 0) == 0,
          "mknodat(AT_FDCWD, fifo4, S_IFIFO|0600, 0) returns 0");
    check(stat(T22_FIFO3, &st) == 0, "stat(fifo3) returns 0");
    check(S_ISFIFO(st.st_mode) && (st.st_mode & 0777) == 0640,
          "mknod fifo3 is S_ISFIFO with mode 0640");
    check(stat(T22_FIFO4, &st) == 0, "stat(fifo4) returns 0");
    check(S_ISFIFO(st.st_mode) && (st.st_mode & 0777) == 0600,
          "mknodat fifo4 is S_ISFIFO with mode 0600");
}
#endif /* VLIBC_LEVEL_GE(2) */

/* Clean up every scratch path; failures here are reported, not fatal. */
static void
cleanup_scenario(void)
{
    long r;

    r = __syscall3(SYS_unlinkat, T22_AT_FDCWD, (long)T22_LINK, 0);
    check(r == 0, "raw unlinkat removes the link");
    r = __syscall3(SYS_unlinkat, T22_AT_FDCWD, (long)T22_FILE, 0);
    check(r == 0, "raw unlinkat removes the temp file");
    r = __syscall3(SYS_unlinkat, T22_AT_FDCWD, (long)T22_FIFO, 0);
    check(r == 0, "raw unlinkat removes fifo");
    r = __syscall3(SYS_unlinkat, T22_AT_FDCWD, (long)T22_FIFO2, 0);
    check(r == 0, "raw unlinkat removes fifo2");
#if VLIBC_LEVEL_GE(2)
    r = __syscall3(SYS_unlinkat, T22_AT_FDCWD, (long)T22_FIFO3, 0);
    check(r == 0, "raw unlinkat removes fifo3");
    r = __syscall3(SYS_unlinkat, T22_AT_FDCWD, (long)T22_FIFO4, 0);
    check(r == 0, "raw unlinkat removes fifo4");
#endif /* VLIBC_LEVEL_GE(2) */
    r = __syscall1(SYS_rmdir, (long)T22_DIR);
    check(r == 0, "raw rmdir removes dir");
    r = __syscall1(SYS_rmdir, (long)T22_DIR2);
    check(r == 0, "raw rmdir removes dir2");
}

/* The failure scenarios. Exit via raw SYS_exit_group: the library's errno
 * writes on these paths corrupt glibc's private dtv slot at %fs:0+8, so
 * host cleanup must never run (house pattern). */
static void
failure_scenarios(void)
{
    struct stat st = {0};

    check(stat(T22_MISSING, &st) == -1, "stat(nonexistent) returns -1");
    check(lstat(T22_MISSING, &st) == -1, "lstat(nonexistent) returns -1");
    check(fstatat(T22_AT_FDCWD, T22_MISSING, &st, 0) == -1,
          "fstatat(AT_FDCWD, nonexistent) returns -1");
    check(fstat(-1, &st) == -1, "fstat(-1) returns -1");
    check(mkdir(T22_FDIR, 0755) == 0, "mkdir(fdir) succeeds for the negative");
    check(mkdir(T22_FDIR, 0755) == -1, "mkdir(existing dir) returns -1");
    check(mkfifo("/nonexistent-vlibc-zzz/x", 0644) == -1, "mkfifo in missing dir returns -1");
    check(chmod(T22_MISSING, 0600) == -1, "chmod(nonexistent) returns -1");
    check(fchmod(-1, 0600) == -1, "fchmod(-1) returns -1");
    check(fchmodat(T22_AT_FDCWD, T22_MISSING, 0600, 0) == -1, "fchmodat(nonexistent) returns -1");
    check(chown(T22_MISSING, (uid_t)-1, (gid_t)-1) == -1, "chown(nonexistent) returns -1");
    check(lchown(T22_MISSING, (uid_t)-1, (gid_t)-1) == -1, "lchown(nonexistent) returns -1");
    check(fchown(-1, (uid_t)-1, (gid_t)-1) == -1, "fchown(-1) returns -1");
    check(fchownat(T22_AT_FDCWD, T22_MISSING, (uid_t)-1, (gid_t)-1, 0) == -1,
          "fchownat(nonexistent) returns -1");
    check(utimensat(T22_AT_FDCWD, T22_MISSING, 0, 0) == -1, "utimensat(nonexistent) returns -1");
    check(futimens(-1, 0) == -1, "futimens(-1) returns -1");
#if VLIBC_LEVEL_GE(2)
    check(mknod(T22_FDIR, 0644, 0) == -1, "mknod without a type bit returns -1");
    check(mknodat(T22_AT_FDCWD, T22_FDIR, 0644, 0) == -1, "mknodat without a type bit returns -1");
    check(mknod("/nonexistent-vlibc-zzz/x", S_IFIFO | 0644, 0) == -1,
          "mknod in missing dir returns -1");
#endif /* VLIBC_LEVEL_GE(2) */

    __syscall1(SYS_rmdir, (long)T22_FDIR);
    if (failures == 0)
    {
        say(1, "all stat failure scenarios passed\n");
    }
    else
    {
        say(1, "FAILURES: ");
        say_dec(1, (unsigned long)failures);
        say(1, "\n");
    }
    __syscall1(SYS_exit_group, failures == 0 ? 0 : 1);
}

int
main(int argc, char **argv)
{
    if (argc > 1 && argv[1][0] == '-' && argv[1][1] == 'f' && argv[1][2] == '\0')
    {
        failure_scenarios();
    }

    dev_null_scenario();
    file_scenario();
    mkdir_scenario();
    symlink_scenario();
    mkfifo_scenario();
#if VLIBC_LEVEL_GE(2)
    mknod_scenario();
#endif /* VLIBC_LEVEL_GE(2) */
    cleanup_scenario();

    if (failures == 0)
    {
        say(1, "all stat tests passed\n");
    }
    else
    {
        say(1, "FAILURES: ");
        say_dec(1, (unsigned long)failures);
        say(1, "\n");
    }
    return failures == 0 ? 0 : 1;
}