On 06/07/2019 16.57, Aleksa Sarai wrote:
--- a/fs/open.c
+++ b/fs/open.c
@@ -928,24 +928,32 @@ struct file *open_with_fake_path(const struct path *path, int flags,
}
EXPORT_SYMBOL(open_with_fake_path);
-static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
+static inline int build_open_flags(struct open_how how, struct open_flags *op)
{
How does passing such a huge struct by value affect code generation?
Does gcc actually inline the function (and does it even inline the old
one given that it's already non-trivial and has more than one caller).
int lookup_flags = 0;
- int acc_mode = ACC_MODE(flags);
+ int opath_mask = 0;
+ int acc_mode = ACC_MODE(how.flags);
+
+ if (how.resolve & ~VALID_RESOLVE_FLAGS)
+ return -EINVAL;
+ if (!(how.flags & (O_PATH | O_CREAT | __O_TMPFILE)) && how.mode != 0)
+ return -EINVAL;
+ if (memchr_inv(how.reserved, 0, sizeof(how.reserved)))
+ return -EINVAL;
How about passing how by const reference, and copy the few fields you
need to local variables. That would at least simplify this patch by
eliminating a lot of the
- flags &= VALID_OPEN_FLAGS;
+ how.flags &= VALID_OPEN_FLAGS;
- if (flags & (O_CREAT | __O_TMPFILE))
- op->mode = (mode & S_IALLUGO) | S_IFREG;
+ if (how.flags & (O_CREAT | __O_TMPFILE))
+ op->mode = (how.mode & S_IALLUGO) | S_IFREG;
churn.
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index 2868ae6c8fc1..e59917292213 100644
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -4,13 +4,26 @@
#include <uapi/linux/fcntl.h>
-/* list of all valid flags for the open/openat flags argument: */
+/* Should open_how.mode be set for older syscalls wrappers? */
+#define OPENHOW_MODE(flags, mode) \
+ (((flags) | (O_CREAT | __O_TMPFILE)) ? (mode) : 0)
+
Typo: (((flags) & (O_CREAT | __O_TMPFILE)) ? (mode) : 0)
+/**
+ * Arguments for how openat2(2) should open the target path. If @extra is zero,
+ * then openat2(2) is identical to openat(2).
+ *
+ * @flags: O_* flags (unknown flags ignored).
+ * @mode: O_CREAT file mode (ignored otherwise).
should probably say "O_CREAT/O_TMPFILE file mode".
+ * @upgrade_mask: restrict how the O_PATH may be re-opened (ignored otherwise).
+ * @resolve: RESOLVE_* flags (-EINVAL on unknown flags).
+ * @reserved: reserved for future extensions, must be zeroed.
+ */
+struct open_how {
+ __u32 flags;
+ union {
+ __u16 mode;
+ __u16 upgrade_mask;
+ };
+ __u16 resolve;
So mode and upgrade_mask are naturally u16 aka mode_t. And yes, they
probably never need to be used together, so the union works. That then
makes the next member 2-byte aligned, so using a u16 for the resolve
flags brings us to an 8-byte boundary, and 11 unused flag bits should be
enough for a while. But it seems a bit artificial to cram all this
together and then add 56 bytes of reserved space.
Rasmus
