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ostree/libglnx/glnx-fdio.c

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/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
*
* Copyright (C) 2014,2015 Colin Walters <walters@verbum.org>.
*
* Portions derived from systemd:
* Copyright 2010 Lennart Poettering
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include "config.h"
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <sys/ioctl.h>
#include <sys/sendfile.h>
#include <errno.h>
/* See linux.git/fs/btrfs/ioctl.h */
#define BTRFS_IOCTL_MAGIC 0x94
#define BTRFS_IOC_CLONE _IOW(BTRFS_IOCTL_MAGIC, 9, int)
#include <glnx-fdio.h>
#include <glnx-dirfd.h>
#include <glnx-errors.h>
#include <glnx-xattrs.h>
#include <glnx-backport-autoptr.h>
#include <glnx-local-alloc.h>
static guint8*
glnx_fd_readall_malloc (int fd,
gsize *out_len,
gboolean nul_terminate,
GCancellable *cancellable,
GError **error)
{
gboolean success = FALSE;
const guint maxreadlen = 4096;
int res;
struct stat stbuf;
guint8* buf = NULL;
gsize buf_allocated;
gsize buf_size = 0;
gssize bytes_read;
do
res = fstat (fd, &stbuf);
while (G_UNLIKELY (res == -1 && errno == EINTR));
if (res == -1)
{
glnx_set_error_from_errno (error);
goto out;
}
if (S_ISREG (stbuf.st_mode) && stbuf.st_size > 0)
buf_allocated = stbuf.st_size;
else
buf_allocated = 16;
buf = g_malloc (buf_allocated);
while (TRUE)
{
gsize readlen = MIN (buf_allocated - buf_size, maxreadlen);
if (g_cancellable_set_error_if_cancelled (cancellable, error))
goto out;
do
bytes_read = read (fd, buf + buf_size, readlen);
while (G_UNLIKELY (bytes_read == -1 && errno == EINTR));
if (G_UNLIKELY (bytes_read == -1))
{
glnx_set_error_from_errno (error);
goto out;
}
if (bytes_read == 0)
break;
buf_size += bytes_read;
if (buf_allocated - buf_size < maxreadlen)
buf = g_realloc (buf, buf_allocated *= 2);
}
if (nul_terminate)
{
if (buf_allocated - buf_size == 0)
buf = g_realloc (buf, buf_allocated + 1);
buf[buf_size] = '\0';
}
success = TRUE;
out:
if (success)
{
*out_len = buf_size;
return buf;
}
g_free (buf);
return NULL;
}
/**
* glnx_fd_readall_bytes:
* @fd: A file descriptor
* @cancellable: Cancellable:
* @error: Error
*
* Read all data from file descriptor @fd into a #GBytes. It's
* recommended to only use this for small files.
*
* Returns: (transfer full): A newly allocated #GBytes
*/
GBytes *
glnx_fd_readall_bytes (int fd,
GCancellable *cancellable,
GError **error)
{
guint8 *buf;
gsize len;
buf = glnx_fd_readall_malloc (fd, &len, FALSE, cancellable, error);
if (!buf)
return NULL;
return g_bytes_new_take (buf, len);
}
/**
* glnx_fd_readall_utf8:
* @fd: A file descriptor
* @out_len: (out): Returned length
* @cancellable: Cancellable:
* @error: Error
*
* Read all data from file descriptor @fd, validating
* the result as UTF-8.
*
* Returns: (transfer full): A string validated as UTF-8, or %NULL on error.
*/
char *
glnx_fd_readall_utf8 (int fd,
gsize *out_len,
GCancellable *cancellable,
GError **error)
{
gboolean success = FALSE;
guint8 *buf;
gsize len;
buf = glnx_fd_readall_malloc (fd, &len, TRUE, cancellable, error);
if (!buf)
goto out;
if (!g_utf8_validate ((char*)buf, len, NULL))
{
g_set_error (error,
G_IO_ERROR,
G_IO_ERROR_INVALID_DATA,
"Invalid UTF-8");
goto out;
}
success = TRUE;
out:
if (success)
{
if (out_len)
*out_len = len;
return (char*)buf;
}
g_free (buf);
return NULL;
}
/**
* glnx_file_get_contents_utf8_at:
* @dfd: Directory file descriptor
* @subpath: Path relative to @dfd
* @out_len: (out) (allow-none): Optional length
* @cancellable: Cancellable
* @error: Error
*
* Read the entire contents of the file referred
* to by @dfd and @subpath, validate the result as UTF-8.
* The length is optionally stored in @out_len.
*
* Returns: (transfer full): UTF-8 validated text, or %NULL on error
*/
char *
glnx_file_get_contents_utf8_at (int dfd,
const char *subpath,
gsize *out_len,
GCancellable *cancellable,
GError **error)
{
gboolean success = FALSE;
glnx_fd_close int fd = -1;
char *buf = NULL;
gsize len;
dfd = glnx_dirfd_canonicalize (dfd);
do
fd = openat (dfd, subpath, O_RDONLY | O_NOCTTY | O_CLOEXEC);
while (G_UNLIKELY (fd == -1 && errno == EINTR));
if (G_UNLIKELY (fd == -1))
{
glnx_set_error_from_errno (error);
goto out;
}
buf = glnx_fd_readall_utf8 (fd, &len, cancellable, error);
if (G_UNLIKELY(!buf))
goto out;
success = TRUE;
out:
if (success)
{
if (out_len)
*out_len = len;
return buf;
}
g_free (buf);
return NULL;
}
/**
* glnx_readlinkat_malloc:
* @dfd: Directory file descriptor
* @subpath: Subpath
* @cancellable: Cancellable
* @error: Error
*
* Read the value of a symlink into a dynamically
* allocated buffer.
*/
char *
glnx_readlinkat_malloc (int dfd,
const char *subpath,
GCancellable *cancellable,
GError **error)
{
size_t l = 100;
dfd = glnx_dirfd_canonicalize (dfd);
for (;;)
{
char *c;
ssize_t n;
c = g_malloc (l);
n = TEMP_FAILURE_RETRY (readlinkat (dfd, subpath, c, l-1));
if (n < 0)
{
glnx_set_error_from_errno (error);
g_free (c);
return FALSE;
}
if ((size_t) n < l-1)
{
c[n] = 0;
return c;
}
g_free (c);
l *= 2;
}
g_assert_not_reached ();
}
static gboolean
copy_symlink_at (int src_dfd,
const char *src_subpath,
const struct stat *src_stbuf,
int dest_dfd,
const char *dest_subpath,
GLnxFileCopyFlags copyflags,
GCancellable *cancellable,
GError **error)
{
gboolean ret = FALSE;
g_autofree char *buf = NULL;
buf = glnx_readlinkat_malloc (src_dfd, src_subpath, cancellable, error);
if (!buf)
goto out;
if (TEMP_FAILURE_RETRY (symlinkat (buf, dest_dfd, dest_subpath)) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
if (!(copyflags & GLNX_FILE_COPY_NOXATTRS))
{
g_autoptr(GVariant) xattrs = NULL;
if (!glnx_dfd_name_get_all_xattrs (src_dfd, src_subpath, &xattrs,
cancellable, error))
goto out;
if (!glnx_dfd_name_set_all_xattrs (dest_dfd, dest_subpath, xattrs,
cancellable, error))
goto out;
}
if (TEMP_FAILURE_RETRY (fchownat (dest_dfd, dest_subpath,
src_stbuf->st_uid, src_stbuf->st_gid,
AT_SYMLINK_NOFOLLOW)) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
ret = TRUE;
out:
return ret;
}
#define COPY_BUFFER_SIZE (16*1024)
/* From systemd */
static int btrfs_reflink(int infd, int outfd) {
int r;
g_return_val_if_fail(infd >= 0, -1);
g_return_val_if_fail(outfd >= 0, -1);
r = ioctl(outfd, BTRFS_IOC_CLONE, infd);
if (r < 0)
return -errno;
return 0;
}
static int loop_write(int fd, const void *buf, size_t nbytes) {
const uint8_t *p = buf;
g_return_val_if_fail(fd >= 0, -1);
g_return_val_if_fail(buf, -1);
errno = 0;
while (nbytes > 0) {
ssize_t k;
k = write(fd, p, nbytes);
if (k < 0) {
if (errno == EINTR)
continue;
return -errno;
}
if (k == 0) /* Can't really happen */
return -EIO;
p += k;
nbytes -= k;
}
return 0;
}
static int copy_bytes(int fdf, int fdt, off_t max_bytes, bool try_reflink) {
bool try_sendfile = true;
int r;
g_return_val_if_fail (fdf >= 0, -1);
g_return_val_if_fail (fdt >= 0, -1);
/* Try btrfs reflinks first. */
if (try_reflink && max_bytes == (off_t) -1) {
r = btrfs_reflink(fdf, fdt);
if (r >= 0)
return r;
}
for (;;) {
size_t m = COPY_BUFFER_SIZE;
ssize_t n;
if (max_bytes != (off_t) -1) {
if (max_bytes <= 0)
return -EFBIG;
if ((off_t) m > max_bytes)
m = (size_t) max_bytes;
}
/* First try sendfile(), unless we already tried */
if (try_sendfile) {
n = sendfile(fdt, fdf, NULL, m);
if (n < 0) {
if (errno != EINVAL && errno != ENOSYS)
return -errno;
try_sendfile = false;
/* use fallback below */
} else if (n == 0) /* EOF */
break;
else if (n > 0)
/* Succcess! */
goto next;
}
/* As a fallback just copy bits by hand */
{
char buf[m];
n = read(fdf, buf, m);
if (n < 0)
return -errno;
if (n == 0) /* EOF */
break;
r = loop_write(fdt, buf, (size_t) n);
if (r < 0)
return r;
}
next:
if (max_bytes != (off_t) -1) {
g_assert(max_bytes >= n);
max_bytes -= n;
}
}
return 0;
}
/**
* glnx_file_copy_at:
* @src_dfd: Source directory fd
* @src_subpath: Subpath relative to @src_dfd
* @dest_dfd: Target directory fd
* @dest_subpath: Destination name
* @copyflags: Flags
* @cancellable: cancellable
* @error: Error
*
* Perform a full copy of the regular file or
* symbolic link from @src_subpath to @dest_subpath.
*
* If @src_subpath is anything other than a regular
* file or symbolic link, an error will be returned.
*/
gboolean
glnx_file_copy_at (int src_dfd,
const char *src_subpath,
struct stat *src_stbuf,
int dest_dfd,
const char *dest_subpath,
GLnxFileCopyFlags copyflags,
GCancellable *cancellable,
GError **error)
{
gboolean ret = FALSE;
int r;
int dest_open_flags;
struct timespec ts[2];
glnx_fd_close int src_fd = -1;
glnx_fd_close int dest_fd = -1;
struct stat local_stbuf;
if (g_cancellable_set_error_if_cancelled (cancellable, error))
goto out;
src_dfd = glnx_dirfd_canonicalize (src_dfd);
dest_dfd = glnx_dirfd_canonicalize (dest_dfd);
/* Automatically do stat() if no stat buffer was supplied */
if (!src_stbuf)
{
if (fstatat (src_dfd, src_subpath, &local_stbuf, AT_SYMLINK_NOFOLLOW) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
src_stbuf = &local_stbuf;
}
if (S_ISLNK (src_stbuf->st_mode))
{
return copy_symlink_at (src_dfd, src_subpath, src_stbuf,
dest_dfd, dest_subpath,
copyflags,
cancellable, error);
}
else if (!S_ISREG (src_stbuf->st_mode))
{
g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
"Cannot copy non-regular/non-symlink file: %s", src_subpath);
goto out;
}
src_fd = TEMP_FAILURE_RETRY (openat (src_dfd, src_subpath, O_RDONLY | O_CLOEXEC | O_NOCTTY | O_NOFOLLOW));
if (src_fd == -1)
{
glnx_set_error_from_errno (error);
goto out;
}
dest_open_flags = O_WRONLY | O_CREAT | O_CLOEXEC | O_NOCTTY;
if (!(copyflags & GLNX_FILE_COPY_OVERWRITE))
dest_open_flags |= O_EXCL;
else
dest_open_flags |= O_TRUNC;
dest_fd = TEMP_FAILURE_RETRY (openat (dest_dfd, dest_subpath, dest_open_flags, src_stbuf->st_mode));
if (dest_fd == -1)
{
glnx_set_error_from_errno (error);
goto out;
}
r = copy_bytes (src_fd, dest_fd, (off_t) -1, TRUE);
if (r < 0)
{
errno = -r;
glnx_set_error_from_errno (error);
goto out;
}
if (fchown (dest_fd, src_stbuf->st_uid, src_stbuf->st_gid) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
if (fchmod (dest_fd, src_stbuf->st_mode & 07777) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
ts[0] = src_stbuf->st_atim;
ts[1] = src_stbuf->st_mtim;
(void) futimens (dest_fd, ts);
if (!(copyflags & GLNX_FILE_COPY_NOXATTRS))
{
g_autoptr(GVariant) xattrs = NULL;
if (!glnx_fd_get_all_xattrs (src_fd, &xattrs,
cancellable, error))
goto out;
if (!glnx_fd_set_all_xattrs (dest_fd, xattrs,
cancellable, error))
goto out;
}
if (copyflags & GLNX_FILE_COPY_DATASYNC)
{
if (fdatasync (dest_fd) < 0)
{
glnx_set_error_from_errno (error);
goto out;
}
}
r = close (dest_fd);
dest_fd = -1;
if (r < 0)
{
glnx_set_error_from_errno (error);
goto out;
}
ret = TRUE;
out:
if (!ret)
(void) unlinkat (dest_dfd, dest_subpath, 0);
return ret;
}
/**
* glnx_file_replace_contents_at:
* @dfd: Directory fd
* @subpath: Subpath
* @buf: (array len=len) (element-type guint8): File contents
* @len: Length (if `-1`, assume @buf is `NUL` terminated)
* @flags: Flags
* @cancellable: Cancellable
* @error: Error
*
* Create a new file, atomically replacing the contents of @subpath
* (relative to @dfd) with @buf. By default, if the file already
* existed, fdatasync() will be used before rename() to ensure stable
* contents. This and other behavior can be controlled via @flags.
*
* Note that no metadata from the existing file is preserved, such as
* uid/gid or extended attributes. The default mode will be `0666`,
* modified by umask.
*/
gboolean
glnx_file_replace_contents_at (int dfd,
const char *subpath,
const guint8 *buf,
gsize len,
GLnxFileReplaceFlags flags,
GCancellable *cancellable,
GError **error)
{
return glnx_file_replace_contents_with_perms_at (dfd, subpath, buf, len,
(mode_t) -1, (uid_t) -1, (gid_t) -1,
flags, cancellable, error);
}
/**
* glnx_file_replace_contents_with_perms_at:
* @dfd: Directory fd
* @subpath: Subpath
* @buf: (array len=len) (element-type guint8): File contents
* @len: Length (if `-1`, assume @buf is `NUL` terminated)
* @mode: File mode; if `-1`, use `0666 - umask`
* @flags: Flags
* @cancellable: Cancellable
* @error: Error
*
* Like glnx_file_replace_contents_at(), but also supports
* setting mode, and uid/gid.
*/
gboolean
glnx_file_replace_contents_with_perms_at (int dfd,
const char *subpath,
const guint8 *buf,
gsize len,
mode_t mode,
uid_t uid,
gid_t gid,
GLnxFileReplaceFlags flags,
GCancellable *cancellable,
GError **error)
{
gboolean ret = FALSE;
int r;
/* We use the /proc/self trick as there's no mkostemp_at() yet */
g_autofree char *tmppath = g_strdup_printf ("/proc/self/fd/%d/.tmpXXXXXX", dfd);
glnx_fd_close int fd = -1;
dfd = glnx_dirfd_canonicalize (dfd);
if ((fd = g_mkstemp_full (tmppath, O_WRONLY | O_CLOEXEC,
mode == (mode_t) -1 ? 0666 : mode)) == -1)
{
glnx_set_error_from_errno (error);
goto out;
}
if (len == -1)
len = strlen ((char*)buf);
/* Note that posix_fallocate does *not* set errno but returns it. */
r = posix_fallocate (fd, 0, len);
if (r != 0)
{
errno = r;
glnx_set_error_from_errno (error);
goto out;
}
if ((r = loop_write (fd, buf, len)) != 0)
{
errno = -r;
glnx_set_error_from_errno (error);
goto out;
}
if (!(flags & GLNX_FILE_REPLACE_NODATASYNC))
{
struct stat stbuf;
gboolean do_sync;
if (fstatat (dfd, subpath, &stbuf, AT_SYMLINK_NOFOLLOW) != 0)
{
if (errno != ENOENT)
{
glnx_set_error_from_errno (error);
goto out;
}
do_sync = (flags & GLNX_FILE_REPLACE_DATASYNC_NEW) > 0;
}
else
do_sync = TRUE;
if (do_sync)
{
if (fdatasync (fd) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
}
}
if (uid != (uid_t) -1)
{
if (fchown (fd, uid, gid) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
}
/* If a mode was forced, override umask */
if (mode != (mode_t) -1)
{
if (fchmod (fd, mode) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
}
if (renameat (dfd, tmppath, dfd, subpath) != 0)
{
glnx_set_error_from_errno (error);
goto out;
}
ret = TRUE;
out:
return ret;
}
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