From 23b6e4aa9510b3194d2b21a38b6c831c9e2c4f8f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Andr=C3=A9=20Almeida?= Date: Mon, 25 Oct 2021 09:49:42 -0300 Subject: [PATCH] futex: Add entry point for FUTEX_WAIT_MULTIPLE (opcode 31) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add an option to wait on multiple futexes using the old interface, that uses opcode 31 through futex() syscall. Do that by just translation the old interface to use the new code. This allows old and stable versions of Proton to still use fsync in new kernel releases. Signed-off-by: André Almeida --- include/uapi/linux/futex.h | 12 ++++++ kernel/futex.c | 75 +++++++++++++++++++++++++++++++++++++- 2 files changed, 86 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/futex.h b/include/uapi/linux/futex.h index 1666f5e4b837f..e1616d5b845b5 100644 --- a/include/uapi/linux/futex.h +++ b/include/uapi/linux/futex.h @@ -21,6 +21,7 @@ #define FUTEX_WAKE_BITSET 10 #define FUTEX_WAIT_REQUEUE_PI 11 #define FUTEX_CMP_REQUEUE_PI 12 +#define FUTEX_WAIT_MULTIPLE 31 #define FUTEX_PRIVATE_FLAG 128 #define FUTEX_CLOCK_REALTIME 256 @@ -66,6 +67,17 @@ struct futex_waitv { __u32 __reserved; }; +/** + * struct futex_wait_block - Block of futexes to be waited for + * @uaddr: User address of the futex + * @val: Futex value expected by userspace + * @bitset: Bitset for the optional bitmasked wakeup + */ +struct futex_wait_block { + __u32 __user *uaddr; + __u32 val; + __u32 bitset; +}; /* * Support for robust futexes: the kernel cleans up held futexes at diff --git a/kernel/futex.c b/kernel/futex.c index d15ec942f06f3..e8866ace3ea0e 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -3779,6 +3779,7 @@ static __always_inline bool futex_cmd_has_timeout(u32 cmd) case FUTEX_LOCK_PI: case FUTEX_WAIT_BITSET: case FUTEX_WAIT_REQUEUE_PI: + case FUTEX_WAIT_MULTIPLE: return true; } return false; @@ -3791,13 +3792,79 @@ futex_init_timeout(u32 cmd, u32 op, struct timespec64 *ts, ktime_t *t) return -EINVAL; *t = timespec64_to_ktime(*ts); - if (cmd == FUTEX_WAIT) + if (cmd == FUTEX_WAIT || cmd == FUTEX_WAIT_MULTIPLE) *t = ktime_add_safe(ktime_get(), *t); else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME)) *t = timens_ktime_to_host(CLOCK_MONOTONIC, *t); return 0; } +/** + * futex_read_wait_block - Read an array of futex_wait_block from userspace + * @uaddr: Userspace address of the block + * @count: Number of blocks to be read + * + * This function creates and allocate an array of futex_q (we zero it to + * initialize the fields) and then, for each futex_wait_block element from + * userspace, fill a futex_q element with proper values. + */ +inline struct futex_vector *futex_read_wait_block(u32 __user *uaddr, u32 count) +{ + unsigned int i; + struct futex_vector *futexv; + struct futex_wait_block fwb; + struct futex_wait_block __user *entry = + (struct futex_wait_block __user *)uaddr; + + if (!count || count > FUTEX_WAITV_MAX) + return ERR_PTR(-EINVAL); + + futexv = kcalloc(count, sizeof(*futexv), GFP_KERNEL); + if (!futexv) + return ERR_PTR(-ENOMEM); + + for (i = 0; i < count; i++) { + if (copy_from_user(&fwb, &entry[i], sizeof(fwb))) { + kfree(futexv); + return ERR_PTR(-EFAULT); + } + + futexv[i].w.flags = FUTEX_32; + futexv[i].w.val = fwb.val; + futexv[i].w.uaddr = (uintptr_t) (fwb.uaddr); + futexv[i].q = futex_q_init; + } + + return futexv; +} + +int futex_wait_multiple(struct futex_vector *vs, unsigned int count, + struct hrtimer_sleeper *to); + +int futex_opcode_31(ktime_t *abs_time, u32 __user *uaddr, int count) +{ + int ret; + struct futex_vector *vs; + struct hrtimer_sleeper *to = NULL, timeout; + + to = futex_setup_timer(abs_time, &timeout, 0, 0); + + vs = futex_read_wait_block(uaddr, count); + + if (IS_ERR(vs)) + return PTR_ERR(vs); + + ret = futex_wait_multiple(vs, count, abs_time ? to : NULL); + kfree(vs); + + if (to) { + hrtimer_cancel(&to->timer); + destroy_hrtimer_on_stack(&to->timer); + } + + return ret; +} + SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, struct __kernel_timespec __user *, utime, u32 __user *, uaddr2, u32, val3) @@ -3817,6 +3884,9 @@ SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, tp = &t; } + if (cmd == FUTEX_WAIT_MULTIPLE) + return futex_opcode_31(tp, uaddr, val); + return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3); } @@ -4318,6 +4388,9 @@ SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val, tp = &t; } + if (cmd == FUTEX_WAIT_MULTIPLE) + return futex_opcode_31(tp, uaddr, val); + return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3); } #endif /* CONFIG_COMPAT_32BIT_TIME */