[PATCH v1] futex: Add compat_sys_futex_waitv for 32bit compatibility

[Wei Gao]

From: wei gao <wegao@xxxxxxxx>

Current implementation lead LTP test case futex_waitv failed when compiled with
-m32. This patch add new compat_sys_futex_waitv to handle m32 mode syscall.

The failure reason is futex_waitv in m32 mode will deliver kernel with struct
old_timespec32 timeout, but this struct type can not directly used by current
sys_futex_waitv implementation.

The new function copy main logic of current sys_futex_waitv, just update parameter
type from "struct __kernel_timespec __user *" to "struct old_timespec32 __user *,"
and use get_old_timespec32 within the new function to get timeout value.

Signed-off-by: wei gao <wegao@xxxxxxxx>
---
 arch/x86/entry/syscalls/syscall_32.tbl |  2 +-
 kernel/futex/syscalls.c                | 61 ++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index c8fac5205803..11bd927dd417 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -453,7 +453,7 @@
 446	i386	landlock_restrict_self	sys_landlock_restrict_self
 447	i386	memfd_secret		sys_memfd_secret
 448	i386	process_mrelease	sys_process_mrelease
-449	i386	futex_waitv		sys_futex_waitv
+449	i386	futex_waitv		sys_futex_waitv  compat_sys_futex_waitv
 450	i386	set_mempolicy_home_node		sys_set_mempolicy_home_node
 451	i386	cachestat		sys_cachestat
 452	i386	fchmodat2		sys_fchmodat2
diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c
index 4b6da9116aa6..62d69f8ec34c 100644
--- a/kernel/futex/syscalls.c
+++ b/kernel/futex/syscalls.c
@@ -486,6 +486,67 @@ COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
 
 	return ret;
 }
+
+COMPAT_SYSCALL_DEFINE5(futex_waitv, struct futex_waitv __user *, waiters,
+		unsigned int, nr_futexes, unsigned int, flags,
+		struct old_timespec32 __user *, timeout, clockid_t, clockid)
+{
+	struct hrtimer_sleeper to;
+	struct futex_vector *futexv;
+	struct timespec64 ts;
+	ktime_t time;
+	int ret;
+
+	/* This syscall supports no flags for now */
+	if (flags)
+		return -EINVAL;
+
+	if (!nr_futexes || nr_futexes > FUTEX_WAITV_MAX || !waiters)
+		return -EINVAL;
+
+	if (timeout) {
+		int flag_clkid = 0, flag_init = 0;
+
+		if (clockid == CLOCK_REALTIME) {
+			flag_clkid = FLAGS_CLOCKRT;
+			flag_init = FUTEX_CLOCK_REALTIME;
+		}
+
+		if (clockid != CLOCK_REALTIME && clockid != CLOCK_MONOTONIC)
+			return -EINVAL;
+
+		if (get_old_timespec32(&ts, timeout))
+			return -EFAULT;
+
+		/*
+		 * Since there's no opcode for futex_waitv, use
+		 * FUTEX_WAIT_BITSET that uses absolute timeout as well
+		 */
+		ret = futex_init_timeout(FUTEX_WAIT_BITSET, flag_init, &ts, &time);
+		if (ret)
+			return ret;
+
+		futex_setup_timer(&time, &to, flag_clkid, 0);
+	}
+
+	futexv = kcalloc(nr_futexes, sizeof(*futexv), GFP_KERNEL);
+	if (!futexv) {
+		ret = -ENOMEM;
+		goto destroy_timer;
+	}
+
+	ret = futex_parse_waitv(futexv, waiters, nr_futexes, futex_wake_mark,
+				NULL);
+	if (!ret)
+		ret = futex_wait_multiple(futexv, nr_futexes, timeout ? &to : NULL);
+
+	kfree(futexv);
+
+destroy_timer:
+	if (timeout)
+		futex2_destroy_timeout(&to);
+	return ret;
+}
 #endif /* CONFIG_COMPAT */
 
 #ifdef CONFIG_COMPAT_32BIT_TIME
-- 
2.34.1