futex: Flag conversion

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@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: André Almeida <andrealmeid@igalia.com>
Link: https://lore.kernel.org/r/20230921105247.722140574@noisy.programming.kicks-ass.net

diff --git a/kernel/futex/futex.h b/kernel/futex/futex.h
index b5379c0e6d6d1a090d2350431a0561eb80cf5ec1..68fc052dc09be0c2dba2fa357feb4320c2560aa9 100644 (file)
--- 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
+
+#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 unsigned int futex_size(unsigned int flags)
+{
+       return 1 << (flags & FLAGS_SIZE_MASK);
+}
+
+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;
+}
 
 #ifdef CONFIG_FAIL_FUTEX
 extern bool should_fail_futex(bool fshared);

diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c
index 953f0a49de3aa506d8f71a568fd4456140080f11..948ac247c1c63d45538e7ddc72c2821f2dbad7dc 100644 (file)
--- 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 @@ err_unlock:
 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 futex_vector *futexv,
        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;

diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c
index ba01b94082033b18e2c07e7f67599862f5f12929..fa9757766103c913c6693692f65874c1dd452d03 100644 (file)
--- a/kernel/futex/waitwake.c
+++ b/kernel/futex/waitwake.c
@@ -419,11 +419,11 @@ static int futex_wait_multiple_setup(struct futex_vector *vs, int count, int *wo
         */
 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))