2023-08-07 14:07:04

by Peter Zijlstra

Subject: [PATCH v2 02/14] futex: Extend the FUTEX2 flags

Add the definition for the missing but always intended extra sizes,
and add a NUMA flag for the planned numa extention.

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
---
include/uapi/linux/futex.h | 21 ++++++++++++++++++---
kernel/futex/syscalls.c | 9 +++++++--
2 files changed, 25 insertions(+), 5 deletions(-)

--- a/include/uapi/linux/futex.h
+++ b/include/uapi/linux/futex.h
@@ -45,17 +45,32 @@

/*
* Flags for futex2 syscalls.
+ *
+ * NOTE: these are not pure flags, they can also be seen as:
+ *
+ * union {
+ * u32 flags;
+ * struct {
+ * u32 size : 2,
+ * numa : 1,
+ * : 4,
+ * private : 1;
+ * };
+ * };
*/
- /* 0x00 */
- /* 0x01 */
+#define FUTEX2_SIZE_U8 0x00
+#define FUTEX2_SIZE_U16 0x01
#define FUTEX2_SIZE_U32 0x02
- /* 0x04 */
+#define FUTEX2_SIZE_U64 0x03
+#define FUTEX2_NUMA 0x04
/* 0x08 */
/* 0x10 */
/* 0x20 */
/* 0x40 */
#define FUTEX2_PRIVATE FUTEX_PRIVATE_FLAG

+#define FUTEX2_SIZE_MASK 0x03
+
/* do not use */
#define FUTEX_32 FUTEX2_SIZE_U32 /* historical accident :-( */

--- a/kernel/futex/syscalls.c
+++ b/kernel/futex/syscalls.c
@@ -183,7 +183,7 @@ SYSCALL_DEFINE6(futex, u32 __user *, uad
return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
}

-#define FUTEX2_VALID_MASK (FUTEX2_SIZE_U32 | FUTEX2_PRIVATE)
+#define FUTEX2_VALID_MASK (FUTEX2_SIZE_MASK | FUTEX2_PRIVATE)

/**
* futex_parse_waitv - Parse a waitv array from userspace
@@ -207,7 +207,12 @@ static int futex_parse_waitv(struct fute
if ((aux.flags & ~FUTEX2_VALID_MASK) || aux.__reserved)
return -EINVAL;

- if (!(aux.flags & FUTEX2_SIZE_U32))
+ 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)
return -EINVAL;

futexv[i].w.flags = aux.flags;

2023-08-07 20:05:01

by Thomas Gleixner

Subject: Re: [PATCH v2 02/14] futex: Extend the FUTEX2 flags

On Mon, Aug 07 2023 at 14:18, Peter Zijlstra wrote:
> /*
> * Flags for futex2 syscalls.
> + *
> + * NOTE: these are not pure flags, they can also be seen as:
> + *
> + * union {
> + * u32 flags;
> + * struct {
> + * u32 size : 2,
> + * numa : 1,
> + * : 4,
> + * private : 1;
> + * };
> + * };
> */

Nice documentation

Reviewed-by: Thomas Gleixner <[email protected]>

2023-08-08 02:21:42

by André Almeida

Subject: Re: [PATCH v2 02/14] futex: Extend the FUTEX2 flags

Em 07/08/2023 09:18, Peter Zijlstra escreveu:
> Add the definition for the missing but always intended extra sizes,
> and add a NUMA flag for the planned numa extention.
>
> Signed-off-by: Peter Zijlstra (Intel) <[email protected]>

Reviewed-by: André Almeida <[email protected]>