@@ -85,6 +85,10 @@
#include <sys/kcov.h>
#endif
+#ifdef HAVE_OPENAT2_H
+#include <linux/openat2.h>
+#endif
+
#define termios host_termios
#define winsize host_winsize
#define termio host_termio
@@ -653,6 +657,10 @@ safe_syscall3(ssize_t, read, int, fd, void *, buff, size_t, count)
safe_syscall3(ssize_t, write, int, fd, const void *, buff, size_t, count)
safe_syscall4(int, openat, int, dirfd, const char *, pathname, \
int, flags, mode_t, mode)
+#ifdef HAVE_OPENAT2_H
+safe_syscall4(int, openat2, int, dirfd, const char *, pathname, \
+ const struct open_how *, how, size_t, size)
+#endif
#if defined(TARGET_NR_wait4) || defined(TARGET_NR_waitpid)
safe_syscall4(pid_t, wait4, pid_t, pid, int *, status, int, options, \
struct rusage *, rusage)
@@ -8334,8 +8342,9 @@ static int open_net_route(CPUArchState *cpu_env, int fd)
}
#endif
-int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *fname,
- int flags, mode_t mode, bool safe)
+static int maybe_do_fake_open(CPUArchState *cpu_env, int dirfd,
+ const char *fname, int flags, mode_t mode,
+ bool safe, bool *use_returned_fd)
{
g_autofree char *proc_name = NULL;
const char *pathname;
@@ -8362,6 +8371,7 @@ int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *fname,
#endif
{ NULL, NULL, NULL }
};
+ *use_returned_fd = true;
/* if this is a file from /proc/ filesystem, expand full name */
proc_name = realpath(fname, NULL);
@@ -8418,12 +8428,87 @@ int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *fname,
return fd;
}
+ *use_returned_fd = false;
+ return -1;
+}
+
+int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *fname,
+ int flags, mode_t mode, bool safe)
+{
+ bool use_returned_fd;
+ int fd = maybe_do_fake_open(cpu_env, dirfd, fname, flags, mode, safe,
+ &use_returned_fd);
+ if (use_returned_fd)
+ return fd;
+
if (safe) {
- return safe_openat(dirfd, path(pathname), flags, mode);
+ return safe_openat(dirfd, path(fname), flags, mode);
} else {
- return openat(dirfd, path(pathname), flags, mode);
+ return openat(dirfd, path(fname), flags, mode);
+ }
+}
+
+#ifdef HAVE_OPENAT2_H
+static int do_guest_openat2(CPUArchState *cpu_env, int dirfd, const char *fname,
+ struct open_how *how)
+{
+ /*
+ * Ideally we would pass "how->resolve" flags into this helper too but
+ * the lookup for files that need faking is based on "realpath()" so
+ * neither a dirfd for "proc" nor restrictions via "resolve" flags can
+ * be honored right now.
+ */
+ bool use_returned_fd;
+ int fd = maybe_do_fake_open(cpu_env, dirfd, fname, how->flags, how->mode,
+ true, &use_returned_fd);
+ if (use_returned_fd)
+ return fd;
+
+ return safe_openat2(dirfd, fname, how, sizeof(struct open_how));
+}
+
+static int do_openat2(CPUArchState *cpu_env, abi_long arg1, abi_long arg2,
+ abi_long arg3, abi_long arg4)
+{
+ struct open_how how = {0};
+ struct target_open_how *target_how = NULL;
+ int ret;
+
+ char *p = lock_user_string(arg2);
+ if (!p) {
+ ret = -TARGET_EFAULT;
+ goto out;
+ }
+ if (!(lock_user_struct(VERIFY_READ, target_how, arg3, 1))) {
+ ret = -TARGET_EFAULT;
+ goto out;
+ }
+ size_t target_open_how_struct_size = arg4;
+ if (target_open_how_struct_size < sizeof(struct target_open_how)) {
+ ret = -TARGET_EINVAL;
+ goto out;
+ }
+ if (target_open_how_struct_size > sizeof(struct target_open_how)) {
+ qemu_log_mask(LOG_UNIMP, "Unimplemented openat2 open_how size: %lu\n",
+ target_open_how_struct_size);
+ ret = -TARGET_E2BIG;
+ goto out;
}
+
+ how.flags = target_to_host_bitmask(target_how->flags, fcntl_flags_tbl);
+ how.mode = tswap64(target_how->mode);
+ how.resolve = tswap64(target_how->resolve);
+ ret = get_errno(do_guest_openat2(cpu_env, arg1, p, &how));
+
+ fd_trans_unregister(ret);
+ out:
+ if (target_how)
+ unlock_user_struct(target_how, arg3, 0);
+ if (p)
+ unlock_user(p, arg2, 0);
+ return ret;
}
+#endif
ssize_t do_guest_readlink(const char *pathname, char *buf, size_t bufsiz)
{
@@ -9197,6 +9282,11 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1,
fd_trans_unregister(ret);
unlock_user(p, arg2, 0);
return ret;
+#if defined(TARGET_NR_openat2) && defined(HAVE_OPENAT2_H)
+ case TARGET_NR_openat2:
+ ret = do_openat2(cpu_env, arg1, arg2, arg3, arg4);
+ return ret;
+#endif
#if defined(TARGET_NR_name_to_handle_at) && defined(CONFIG_OPEN_BY_HANDLE)
case TARGET_NR_name_to_handle_at:
ret = do_name_to_handle_at(arg1, arg2, arg3, arg4, arg5);
@@ -2754,4 +2754,11 @@ struct target_sched_param {
abi_int sched_priority;
};
+/* from kernel's include/uapi/linux/openat2.h */
+struct target_open_how {
+ abi_ullong flags;
+ abi_ullong mode;
+ abi_ullong resolve;
+};
+
#endif
@@ -2465,6 +2465,7 @@ config_host_data.set('CONFIG_LINUX_MAGIC_H', cc.has_header('linux/magic.h'))
config_host_data.set('CONFIG_VALGRIND_H', cc.has_header('valgrind/valgrind.h'))
config_host_data.set('HAVE_BTRFS_H', cc.has_header('linux/btrfs.h'))
config_host_data.set('HAVE_DRM_H', cc.has_header('libdrm/drm.h'))
+config_host_data.set('HAVE_OPENAT2_H', cc.has_header('linux/openat2.h'))
config_host_data.set('HAVE_PTY_H', cc.has_header('pty.h'))
config_host_data.set('HAVE_SYS_DISK_H', cc.has_header('sys/disk.h'))
config_host_data.set('HAVE_SYS_IOCCOM_H', cc.has_header('sys/ioccom.h'))
This commit adds support for the `openat2()` syscall in the `linux-user` userspace emulator. It is implemented by extracting a new helper `maybe_do_fake_open()` out of the exiting `do_guest_openat()` and share that with the new `do_guest_openat2()`. Unfortunatly we cannot just make do_guest_openat2() a superset of do_guest_openat() because the openat2() syscall is stricter with the argument checking and will return an error for invalid flags or mode combinations (which open()/openat() will ignore). Note that in this commit using openat2() for a "faked" file in /proc will ignore the "resolve" flags. This is not great but it seems similar to the exiting behavior when openat() is called with a dirfd to "/proc". Here too the fake file lookup may not catch the special file because "realpath()" is used to determine if the path is in /proc. Alternatively to ignoring we could simply fail with `-TARGET_ENOSYS` (or similar) if `resolve` flags are passed and we found something that looks like a file in /proc that needs faking. Signed-off-by: Michael Vogt <mvogt@redhat.com> Buglink: https://github.com/osbuild/bootc-image-builder/issues/619 --- linux-user/syscall.c | 98 +++++++++++++++++++++++++++++++++++++-- linux-user/syscall_defs.h | 7 +++ meson.build | 1 + 3 files changed, 102 insertions(+), 4 deletions(-)