[PATCH 4.9 20/25] kernel, fs: Introduce and use set_restart_fn() and arch_set_restart_data()

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Oleg Nesterov <oleg@xxxxxxxxxx>

commit 5abbe51a526253b9f003e9a0a195638dc882d660 upstream.

Preparation for fixing get_nr_restart_syscall() on X86 for COMPAT.

Add a new helper which sets restart_block->fn and calls a dummy
arch_set_restart_data() helper.

Fixes: 609c19a385c8 ("x86/ptrace: Stop setting TS_COMPAT in ptrace code")
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20210201174641.GA17871@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/select.c                    |   10 ++++------
 include/linux/thread_info.h    |   13 +++++++++++++
 kernel/futex.c                 |    3 +--
 kernel/time/alarmtimer.c       |    2 +-
 kernel/time/hrtimer.c          |    2 +-
 kernel/time/posix-cpu-timers.c |    2 +-
 6 files changed, 21 insertions(+), 11 deletions(-)

--- a/fs/select.c
+++ b/fs/select.c
@@ -961,10 +961,9 @@ static long do_restart_poll(struct resta
 
 	ret = do_sys_poll(ufds, nfds, to);
 
-	if (ret == -EINTR) {
-		restart_block->fn = do_restart_poll;
-		ret = -ERESTART_RESTARTBLOCK;
-	}
+	if (ret == -EINTR)
+		ret = set_restart_fn(restart_block, do_restart_poll);
+
 	return ret;
 }
 
@@ -986,7 +985,6 @@ SYSCALL_DEFINE3(poll, struct pollfd __us
 		struct restart_block *restart_block;
 
 		restart_block = &current->restart_block;
-		restart_block->fn = do_restart_poll;
 		restart_block->poll.ufds = ufds;
 		restart_block->poll.nfds = nfds;
 
@@ -997,7 +995,7 @@ SYSCALL_DEFINE3(poll, struct pollfd __us
 		} else
 			restart_block->poll.has_timeout = 0;
 
-		ret = -ERESTART_RESTARTBLOCK;
+		ret = set_restart_fn(restart_block, do_restart_poll);
 	}
 	return ret;
 }
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -9,6 +9,7 @@
 
 #include <linux/types.h>
 #include <linux/bug.h>
+#include <linux/errno.h>
 
 struct timespec;
 struct compat_timespec;
@@ -59,6 +60,18 @@ extern long do_no_restart_syscall(struct
 
 #ifdef __KERNEL__
 
+#ifndef arch_set_restart_data
+#define arch_set_restart_data(restart) do { } while (0)
+#endif
+
+static inline long set_restart_fn(struct restart_block *restart,
+					long (*fn)(struct restart_block *))
+{
+	restart->fn = fn;
+	arch_set_restart_data(restart);
+	return -ERESTART_RESTARTBLOCK;
+}
+
 #define THREADINFO_GFP	(GFP_KERNEL_ACCOUNT | __GFP_NOTRACK | __GFP_ZERO)
 
 /*
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2822,14 +2822,13 @@ retry:
 		goto out;
 
 	restart = &current->restart_block;
-	restart->fn = futex_wait_restart;
 	restart->futex.uaddr = uaddr;
 	restart->futex.val = val;
 	restart->futex.time = abs_time->tv64;
 	restart->futex.bitset = bitset;
 	restart->futex.flags = flags | FLAGS_HAS_TIMEOUT;
 
-	ret = -ERESTART_RESTARTBLOCK;
+	ret = set_restart_fn(restart, futex_wait_restart);
 
 out:
 	if (to) {
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -809,10 +809,10 @@ static int alarm_timer_nsleep(const cloc
 	}
 
 	restart = &current->restart_block;
-	restart->fn = alarm_timer_nsleep_restart;
 	restart->nanosleep.clockid = type;
 	restart->nanosleep.expires = exp.tv64;
 	restart->nanosleep.rmtp = rmtp;
+	set_restart_fn(restart, alarm_timer_nsleep_restart);
 	ret = -ERESTART_RESTARTBLOCK;
 
 out:
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1582,10 +1582,10 @@ long hrtimer_nanosleep(struct timespec *
 	}
 
 	restart = &current->restart_block;
-	restart->fn = hrtimer_nanosleep_restart;
 	restart->nanosleep.clockid = t.timer.base->clockid;
 	restart->nanosleep.rmtp = rmtp;
 	restart->nanosleep.expires = hrtimer_get_expires_tv64(&t.timer);
+	set_restart_fn(restart, hrtimer_nanosleep_restart);
 
 	ret = -ERESTART_RESTARTBLOCK;
 out:
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -1377,10 +1377,10 @@ static int posix_cpu_nsleep(const clocki
 		if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
 			return -EFAULT;
 
-		restart_block->fn = posix_cpu_nsleep_restart;
 		restart_block->nanosleep.clockid = which_clock;
 		restart_block->nanosleep.rmtp = rmtp;
 		restart_block->nanosleep.expires = timespec_to_ns(rqtp);
+		set_restart_fn(restart_block, posix_cpu_nsleep_restart);
 	}
 	return error;
 }