[PATCH v3 5/6] uapi: futex: Add a futex waitv syscall
From: Alistair Francis <hidden>
Date: 2021-11-26 06:03:21
Also in:
lkml
Subsystem:
the rest · Maintainer:
Linus Torvalds
From: Alistair Francis <redacted> This commit adds a futex waitv syscall wrapper that is exposed to userspace. Neither the kernel or glibc currently expose a futex wrapper, so userspace is left performing raw syscalls. As the futex_waitv syscall always expects a 64-bit time_t this can be tricky for 32-bit systems to get correct. In order to avoid userspace incorrectly passing the wrong timeouts let's expose a public helper function that ensures the kernel is passed the correct timeout struct. Signed-off-by: Alistair Francis <redacted> --- include/uapi/linux/futex_syscall.h | 32 +++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/futex_syscall.h b/include/uapi/linux/futex_syscall.h
index e0305c581142..98c550990833 100644
--- a/include/uapi/linux/futex_syscall.h
+++ b/include/uapi/linux/futex_syscall.h@@ -9,12 +9,15 @@ #ifndef _UAPI_LINUX_FUTEX_SYSCALL_H #define _UAPI_LINUX_FUTEX_SYSCALL_H -#include <asm/unistd.h> +#include <unistd.h> #include <errno.h> +#include <linux/futex.h> #include <linux/types.h> #include <linux/time_types.h> #include <stdint.h> #include <sys/syscall.h> +#include <sys/types.h> +#include <time.h> /** * futex_syscall_timeout() - __NR_futex/__NR_futex_time64 syscall wrapper
@@ -86,4 +89,31 @@ __kernel_futex_syscall_nr_requeue(volatile uint32_t *uaddr, int op, uint32_t val return -1; } +/** + * futex_waitv - Wait at multiple futexes, wake on any + * @waiters: Array of waiters + * @nr_waiters: Length of waiters array + * @flags: Operation flags + * @timo: Optional timeout for operation + */ +static inline int +__kernel_futex_syscall_waitv(volatile struct futex_waitv *waiters, unsigned long nr_waiters, + unsigned long flags, struct timespec *timo, clockid_t clockid) +{ + /* futex_waitv expects a 64-bit time_t */ + if (sizeof(*timo) == sizeof(struct __kernel_timespec)) + return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, timo, clockid); + + /* If the caller supplied a 32-bit time_t, convert it to 64-bit */ + if (timo) { + struct __kernel_timespec ts_new; + + ts_new.tv_sec = timo->tv_sec; + ts_new.tv_nsec = timo->tv_nsec; + + return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, &ts_new, clockid); + } else + return syscall(__NR_futex_waitv, waiters, nr_waiters, flags, NULL, clockid); +} + #endif /* _UAPI_LINUX_FUTEX_SYSCALL_H */
--
2.31.1