Em 07/08/2023 09:18, Peter Zijlstra escreveu:
Futex has 3 sets of flags:
- legacy futex op bits
- futex2 flags
- internal flags
Add a few helpers to convert from the API flags into the internal
flags.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: André Almeida <andrealmeid@xxxxxxxxxx>
---
kernel/futex/futex.h | 63 +++++++++++++++++++++++++++++++++++++++++++++---
kernel/futex/syscalls.c | 24 ++++++------------
kernel/futex/waitwake.c | 4 +--
3 files changed, 71 insertions(+), 20 deletions(-)
--- a/kernel/futex/futex.h
+++ b/kernel/futex/futex.h
@@ -5,6 +5,7 @@
#include <linux/futex.h>
#include <linux/rtmutex.h>
#include <linux/sched/wake_q.h>
+#include <linux/compat.h>
#ifdef CONFIG_PREEMPT_RT
#include <linux/rcuwait.h>
@@ -16,8 +17,15 @@
* Futex flags used to encode options to functions and preserve them across
* restarts.
*/
+#define FLAGS_SIZE_8 0x00
+#define FLAGS_SIZE_16 0x01
+#define FLAGS_SIZE_32 0x02
+#define FLAGS_SIZE_64 0x03
+
Minor nit: for consistent, I would go with SIZE_U8, instead of SIZE_8
+#define FLAGS_SIZE_MASK 0x03
+
#ifdef CONFIG_MMU
-# define FLAGS_SHARED 0x01
+# define FLAGS_SHARED 0x10
#else
/*
* NOMMU does not have per process address space. Let the compiler optimize
@@ -25,8 +33,57 @@
*/
# define FLAGS_SHARED 0x00
#endif
-#define FLAGS_CLOCKRT 0x02
-#define FLAGS_HAS_TIMEOUT 0x04
+#define FLAGS_CLOCKRT 0x20
+#define FLAGS_HAS_TIMEOUT 0x40
+#define FLAGS_NUMA 0x80
+
+/* FUTEX_ to FLAGS_ */
+static inline unsigned int futex_to_flags(unsigned int op)
+{
+ unsigned int flags = FLAGS_SIZE_32;
+
+ if (!(op & FUTEX_PRIVATE_FLAG))
+ flags |= FLAGS_SHARED;
+
+ if (op & FUTEX_CLOCK_REALTIME)
+ flags |= FLAGS_CLOCKRT;
+
+ return flags;
+}
+
+/* FUTEX2_ to FLAGS_ */
+static inline unsigned int futex2_to_flags(unsigned int flags2)
+{
+ unsigned int flags = flags2 & FUTEX2_SIZE_MASK;
+
+ if (!(flags2 & FUTEX2_PRIVATE))
+ flags |= FLAGS_SHARED;
+
+ if (flags2 & FUTEX2_NUMA)
+ flags |= FLAGS_NUMA;
+
+ return flags;
+}
+
+static inline bool futex_flags_valid(unsigned int flags)
+{
+ /* Only 64bit futexes for 64bit code */
+ if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) {
+ if ((flags & FLAGS_SIZE_MASK) == FLAGS_SIZE_64)
+ return false;
+ }
+
+ /* Only 32bit futexes are implemented -- for now */
+ if ((flags & FLAGS_SIZE_MASK) != FLAGS_SIZE_32)
+ return false;
+
+ return true;
+} > +
+static inline unsigned int futex_size(unsigned int flags)
+{
+ return 1 << (flags & FLAGS_SIZE_MASK);
+}
#ifdef CONFIG_FAIL_FUTEX
extern bool should_fail_futex(bool fshared);
--- a/kernel/futex/syscalls.c
+++ b/kernel/futex/syscalls.c
@@ -1,6 +1,5 @@
// SPDX-License-Identifier: GPL-2.0-or-later
-#include <linux/compat.h>
#include <linux/syscalls.h>
#include <linux/time_namespace.h>
@@ -85,15 +84,12 @@ SYSCALL_DEFINE3(get_robust_list, int, pi
long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
u32 __user *uaddr2, u32 val2, u32 val3)
{
+ unsigned int flags = futex_to_flags(op);
int cmd = op & FUTEX_CMD_MASK;
- unsigned int flags = 0;
- if (!(op & FUTEX_PRIVATE_FLAG))
- flags |= FLAGS_SHARED;
-
- if (op & FUTEX_CLOCK_REALTIME) {
- flags |= FLAGS_CLOCKRT;
- if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI &&
+ if (flags & FLAGS_CLOCKRT) {
+ if (cmd != FUTEX_WAIT_BITSET &&
+ cmd != FUTEX_WAIT_REQUEUE_PI &&
cmd != FUTEX_LOCK_PI2)
return -ENOSYS;
}
@@ -201,21 +197,19 @@ static int futex_parse_waitv(struct fute
unsigned int i;
for (i = 0; i < nr_futexes; i++) {
+ unsigned int flags;
+
if (copy_from_user(&aux, &uwaitv[i], sizeof(aux)))
return -EFAULT;
if ((aux.flags & ~FUTEX2_VALID_MASK) || aux.__reserved)
return -EINVAL;
- if (!IS_ENABLED(CONFIG_64BIT) || in_compat_syscall()) {
- if ((aux.flags & FUTEX2_SIZE_MASK) == FUTEX2_SIZE_U64)
- return -EINVAL;
- }
-
- if ((aux.flags & FUTEX2_SIZE_MASK) != FUTEX2_SIZE_U32)
+ flags = futex2_to_flags(aux.flags);
+ if (!futex_flags_valid(flags))
return -EINVAL;
- futexv[i].w.flags = aux.flags;
+ futexv[i].w.flags = flags;
futexv[i].w.val = aux.val;
futexv[i].w.uaddr = aux.uaddr;
futexv[i].q = futex_q_init;
--- a/kernel/futex/waitwake.c
+++ b/kernel/futex/waitwake.c
@@ -419,11 +419,11 @@ static int futex_wait_multiple_setup(str
*/
retry:
for (i = 0; i < count; i++) {
- if ((vs[i].w.flags & FUTEX_PRIVATE_FLAG) && retry)
+ if (!(vs[i].w.flags & FLAGS_SHARED) && retry)
continue;
ret = get_futex_key(u64_to_user_ptr(vs[i].w.uaddr),
- !(vs[i].w.flags & FUTEX_PRIVATE_FLAG),
+ vs[i].w.flags & FLAGS_SHARED,
&vs[i].q.key, FUTEX_READ);
if (unlikely(ret))
