[glib/wip/gbytes-memfd] WIP Add memfd support to GBytes
- From: David King <davidk src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [glib/wip/gbytes-memfd] WIP Add memfd support to GBytes
- Date: Wed, 26 Nov 2014 22:32:24 +0000 (UTC)
commit 90253305a2cf14c761d479b9072782a1c8d5e33f
Author: David King <amigadave amigadave com>
Date: Wed Nov 26 20:02:30 2014 +0000
WIP Add memfd support to GBytes
This code is untested.
configure.ac | 2 +-
docs/reference/glib/glib-sections.txt | 1 +
glib/gbytes.c | 188 +++++++++++++++++++++++++++++++--
glib/gbytes.h | 3 +
4 files changed, 182 insertions(+), 12 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index ced92b2..2703a32 100644
--- a/configure.ac
+++ b/configure.ac
@@ -781,7 +781,7 @@ AC_CHECK_HEADERS([sys/param.h sys/resource.h mach/mach_time.h])
AC_CHECK_HEADERS([sys/select.h stdint.h inttypes.h sched.h malloc.h])
AC_CHECK_HEADERS([sys/vfs.h sys/vmount.h sys/statfs.h sys/statvfs.h sys/filio.h])
AC_CHECK_HEADERS([mntent.h sys/mnttab.h sys/vfstab.h sys/mntctl.h fstab.h])
-AC_CHECK_HEADERS([linux/magic.h sys/prctl.h])
+AC_CHECK_HEADERS([linux/magic.h linux/memfd.h sys/prctl.h])
# Some versions of MSC lack these
AC_CHECK_HEADERS([dirent.h sys/time.h])
diff --git a/docs/reference/glib/glib-sections.txt b/docs/reference/glib/glib-sections.txt
index 20b7101..b07ea71 100644
--- a/docs/reference/glib/glib-sections.txt
+++ b/docs/reference/glib/glib-sections.txt
@@ -2470,6 +2470,7 @@ g_byte_array_free_to_bytes
GBytes
g_bytes_new
g_bytes_new_take
+g_bytes_new_take_fd
g_bytes_new_static
g_bytes_new_with_free_func
g_bytes_new_from_bytes
diff --git a/glib/gbytes.c b/glib/gbytes.c
index 1520d76..5ef8bf1 100644
--- a/glib/gbytes.c
+++ b/glib/gbytes.c
@@ -26,12 +26,53 @@
#include <glib/garray.h>
#include <glib/gstrfuncs.h>
#include <glib/gatomic.h>
+#include <glib/gmappedfile.h>
+#include <glib/gstdio.h>
#include <glib/gslice.h>
#include <glib/gtestutils.h>
#include <glib/gmem.h>
#include <glib/gmessages.h>
#include <string.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#ifdef HAVE_LINUX_MEMFD_H
+#include <fcntl.h>
+#include <linux/memfd.h>
+#include <unistd.h>
+/* FIXME: Use a similar approach to systemd/src/shared/missing.h */
+#ifndef F_LINUX_SPECIFIC_BASE
+#define F_LINUX_SPECIFIC_BASE 1024
+#endif
+
+#ifndef F_SETPIPE_SZ
+#define F_SETPIPE_SZ (F_LINUX_SPECIFIC_BASE + 7)
+#endif
+
+#ifndef F_GETPIPE_SZ
+#define F_GETPIPE_SZ (F_LINUX_SPECIFIC_BASE + 8)
+#endif
+
+#ifndef F_ADD_SEALS
+#define F_ADD_SEALS (F_LINUX_SPECIFIC_BASE + 9)
+#define F_GET_SEALS (F_LINUX_SPECIFIC_BASE + 10)
+
+#define F_SEAL_SEAL 0x0001 /* prevent further seals from being set */
+#define F_SEAL_SHRINK 0x0002 /* prevent file from shrinking */
+#define F_SEAL_GROW 0x0004 /* prevent file from growing */
+#define F_SEAL_WRITE 0x0008 /* prevent writes */
+#endif
+
+#ifndef MFD_ALLOW_SEALING
+#define MFD_ALLOW_SEALING 0x0002U
+#endif
+
+#ifndef MFD_CLOEXEC
+#define MFD_CLOEXEC 0x0001U
+#endif
+/* end FIXME. */
+#endif
/**
* GBytes:
@@ -69,8 +110,10 @@ struct _GBytes
gconstpointer data; /* may be NULL iff (size == 0) */
gsize size; /* may be 0 */
gint ref_count;
+ gint fd; /* -1 when data is not backed by an fd. */
GDestroyNotify free_func;
- gpointer user_data;
+ gpointer user_data; /* used to store a GMappedFile when backed by an fd (and
+ * only after g_bytes_get_data() has been called. */
};
/**
@@ -96,6 +139,104 @@ g_bytes_new (gconstpointer data,
return g_bytes_new_take (g_memdup (data, size), size);
}
+/*
+ * _g_bytes_new_internal:
+ * Same as g_bytes_new_with_free_func() except for the fd parameter, used by
+ * g_bytes_new_take_fd().
+ */
+static GBytes *
+_g_bytes_new_internal (gconstpointer data,
+ gsize size,
+ gint fd,
+ GDestroyNotify free_func,
+ gpointer user_data)
+{
+ GBytes *bytes;
+
+ g_return_val_if_fail (data != NULL || fd != -1, NULL);
+
+ bytes = g_slice_new (GBytes);
+ bytes->data = data;
+ bytes->size = size;
+ bytes->fd = fd;
+ bytes->free_func = free_func;
+ bytes->user_data = user_data;
+ bytes->ref_count = 1;
+
+ return (GBytes *)bytes;
+}
+
+static void
+unref_mapped_file (gpointer data)
+{
+ if (data != NULL)
+ {
+ g_mapped_file_unref ((GMappedFile *)data);
+ }
+}
+
+/**
+ * g_bytes_new_take_fd:
+ * @fd: the file descriptor containg data from which to create a #GBytes
+ *
+ * Creates a new #GBytes from @fd.
+ *
+ * This call "consumes" the file descriptor, transferring ownership to the
+ * returned #GBytes.
+ *
+ * Returns: (transfer full): a new #GBytes
+ *
+ * Since: 2.44
+ */
+GBytes *
+g_bytes_new_take_fd (gint fd)
+{
+#ifdef HAVE_LINUX_MEMFD_H
+ gint seals;
+ const gint IMMUTABLE_SEALS = F_SEAL_WRITE |
+ F_SEAL_SHRINK |
+ F_SEAL_GROW |
+ F_SEAL_SEAL;
+#endif /* HAVE_LINUX_MEMFD_H */
+ gint error;
+ struct stat sb;
+
+#ifdef HAVE_LINUX_MEMFD_H
+ /* FIXME: seal the fd if possible (only on Linux 3.17+, and if the fd was
+ * created with memfd_create()). */
+ /* FIXME: Check if the provided fd is one of the standard ones, and warn? */
+ seals = fcntl (fd, F_GET_SEALS);
+ if (seals == -1)
+ {
+ g_debug ("Retrieving fd seals failed: %s", g_strerror (errno));
+ }
+
+ /* Seal the fd, if it is not already. */
+ if ((seals & (IMMUTABLE_SEALS)) >= IMMUTABLE_SEALS)
+ {
+ g_debug ("%s", "fd already sealed");
+ }
+ else
+ {
+ error = fcntl (fd, F_ADD_SEALS, IMMUTABLE_SEALS);
+ if (error == -1)
+ {
+ g_debug ("fd sealing failed: %s", g_strerror (errno));
+ /* FIXME: use shm_open() on non-Linux, or when memfd_create() is
+ * otherwise unavailable? */
+ }
+ }
+#endif /* HAVE_LINUX_MEMFD_H */
+
+ error = fstat (fd, &sb);
+ if (error == -1)
+ {
+ g_debug ("fstat() on fd failed: %s", g_strerror (errno));
+ }
+
+ return _g_bytes_new_internal (NULL, sb.st_size, fd, NULL, unref_mapped_file);
+}
+
/**
* g_bytes_new_take:
* @data: (transfer full) (array length=size) (element-type guint8) (allow-none):
@@ -176,18 +317,9 @@ g_bytes_new_with_free_func (gconstpointer data,
GDestroyNotify free_func,
gpointer user_data)
{
- GBytes *bytes;
-
g_return_val_if_fail (data != NULL || size == 0, NULL);
- bytes = g_slice_new (GBytes);
- bytes->data = data;
- bytes->size = size;
- bytes->free_func = free_func;
- bytes->user_data = user_data;
- bytes->ref_count = 1;
-
- return (GBytes *)bytes;
+ return _g_bytes_new_internal (data, size, -1, free_func, user_data);
}
/**
@@ -242,9 +374,38 @@ gconstpointer
g_bytes_get_data (GBytes *bytes,
gsize *size)
{
+ GError *error = NULL;
+
g_return_val_if_fail (bytes != NULL, NULL);
+
if (size)
*size = bytes->size;
+
+ if (bytes->fd > -1)
+ {
+ if (bytes->user_data == NULL)
+ {
+ bytes->user_data = g_mapped_file_new_from_fd (bytes->fd, FALSE,
+ &error);
+ if (bytes->user_data == NULL)
+ {
+ g_debug ("Failed to map fd: %s", error->message);
+ *size = 0;
+ return NULL;
+ }
+
+ *size = g_mapped_file_get_length (bytes->user_data);
+ if (*size != bytes->size)
+ {
+ g_debug ("Mapped size differs from that returned by fstat(): %"
+ G_GSIZE_FORMAT " versus %" G_GOFFSET_FORMAT, *size,
+ bytes->size);
+ }
+
+ bytes->data = g_mapped_file_get_contents (bytes->user_data);
+ }
+ }
+
return bytes->data;
}
@@ -461,6 +622,11 @@ g_bytes_unref_to_data (GBytes *bytes,
* Copy: Non g_malloc (or compatible) allocator, or static memory,
* so we have to copy, and then unref.
*/
+ if (!bytes->data && bytes->fd > -1)
+ {
+ /* Map the fd if the data is to be copied. */
+ g_bytes_get_data (bytes, NULL);
+ }
result = g_memdup (bytes->data, bytes->size);
*size = bytes->size;
g_bytes_unref (bytes);
diff --git a/glib/gbytes.h b/glib/gbytes.h
index 24f1856..77bfd30 100644
--- a/glib/gbytes.h
+++ b/glib/gbytes.h
@@ -39,6 +39,9 @@ GLIB_AVAILABLE_IN_ALL
GBytes * g_bytes_new_take (gpointer data,
gsize size);
+GLIB_AVAILABLE_IN_2_44
+GBytes * g_bytes_new_take_fd (gint fd);
+
GLIB_AVAILABLE_IN_ALL
GBytes * g_bytes_new_static (gconstpointer data,
gsize size);
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