Re: [PATCH 06/16] nanosleep/clock_nanosleep: teach to do compat copyouts

From: Peter Zijlstra
Date: Wed Jun 07 2017 - 06:07:31 EST

On Wed, Jun 07, 2017 at 09:42:31AM +0100, Al Viro wrote:
> From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
>
> Turn restart_block.nanosleep.{rmtp,compat_rmtp} into a tagged union
> (kind = 1 -> native, kind = 2 -> compat, kind = 0 -> nothing) and
> make the places doing actual copyout handle compat as well as
> native (that will become a helper in the next commit). Result:
> compat wrappers, messing with reassignments, etc. are gone.

I found something like the below on top slightly easier to read. Ignore
if hated..

---
include/linux/restart_block.h | 10 +++++++++-
kernel/time/alarmtimer.c | 2 +-
kernel/time/hrtimer.c | 23 +++++++++++++++--------
kernel/time/posix-cpu-timers.c | 2 +-
kernel/time/posix-stubs.c | 4 ++--
kernel/time/posix-timers.c | 4 ++--
6 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/include/linux/restart_block.h b/include/linux/restart_block.h
index 4509944bd953..0834e4a8ce69 100644
--- a/include/linux/restart_block.h
+++ b/include/linux/restart_block.h
@@ -11,6 +11,14 @@ struct timespec;
struct compat_timespec;
struct pollfd;

+enum timespec_type {
+ tt_nothing = 0,
+ tt_native = 1,
+#ifdef CONFIG_COMPAT
+ tt_compat = 2,
+#endif
+};
+
/*
* System call restart block.
*/
@@ -29,7 +37,7 @@ struct restart_block {
/* For nanosleep */
struct {
clockid_t clockid;
- int kind;
+ enum timespec_type type;
union {
struct timespec __user *rmtp;
#ifdef CONFIG_COMPAT
diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index 80154e795535..734920be9d4b 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -711,7 +711,7 @@ static int alarmtimer_do_nsleep(struct alarm *alarm, ktime_t absexp,
if (freezing(current))
alarmtimer_freezerset(absexp, type);
restart = &current->restart_block;
- if (restart->nanosleep.kind) {
+ if (restart->nanosleep.type) {
struct timespec rmt;
ktime_t rem;

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 5dd4b3a34495..e1e06a8b6c43 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1442,15 +1442,22 @@ EXPORT_SYMBOL_GPL(hrtimer_init_sleeper);

int nanosleep_copyout(struct restart_block *restart, struct timespec *ts)
{
- BUG_ON(!restart->nanosleep.kind);
+ switch(restart->nanosleep.type) {
#ifdef CONFIG_COMPAT
- if (restart->nanosleep.kind == 2) {
+ case tt_compat:
if (compat_put_timespec(ts, restart->nanosleep.compat_rmtp))
return -EFAULT;
- } else
+ break;
#endif
- if (copy_to_user(restart->nanosleep.rmtp, ts, sizeof(struct timespec)))
- return -EFAULT;
+ case tt_native:
+ if (copy_to_user(restart->nanosleep.rmtp, ts, sizeof(struct timespec)))
+ return -EFAULT;
+ break;
+
+ case tt_nothing:
+ BUG();
+ }
+
return -ERESTART_RESTARTBLOCK;
}

@@ -1477,7 +1484,7 @@ static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mod
return 0;

restart = &current->restart_block;
- if (restart->nanosleep.kind) {
+ if (restart->nanosleep.type) {
struct timespec rmt;
ktime_t rem = hrtimer_expires_remaining(&t->timer);
if (rem <= 0)
@@ -1549,7 +1556,7 @@ SYSCALL_DEFINE2(nanosleep, struct timespec __user *, rqtp,
if (!timespec64_valid(&tu64))
return -EINVAL;

- current->restart_block.nanosleep.kind = rmtp ? 1 : 0;
+ current->restart_block.nanosleep.type = rmtp ? tt_native : tt_nothing;
current->restart_block.nanosleep.rmtp = rmtp;
return hrtimer_nanosleep(&tu64, HRTIMER_MODE_REL, CLOCK_MONOTONIC);
}
@@ -1569,7 +1576,7 @@ COMPAT_SYSCALL_DEFINE2(nanosleep, struct compat_timespec __user *, rqtp,
if (!timespec64_valid(&tu64))
return -EINVAL;

- current->restart_block.nanosleep.kind = rmtp ? 2 : 0;
+ current->restart_block.nanosleep.type = rmtp ? tt_compat : tt_nothing;
current->restart_block.nanosleep.compat_rmtp = rmtp;
return hrtimer_nanosleep(&tu64, HRTIMER_MODE_REL, CLOCK_MONOTONIC);
}
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index f6c5f77b944d..929499e6b4ac 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -1313,7 +1313,7 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
*/
restart = &current->restart_block;
restart->nanosleep.expires = timespec64_to_ns(rqtp);
- if (restart->nanosleep.kind) {
+ if (restart->nanosleep.type) {
struct timespec ts;
ts = timespec64_to_timespec(it.it_value);
error = nanosleep_copyout(restart, &ts);
diff --git a/kernel/time/posix-stubs.c b/kernel/time/posix-stubs.c
index c0c18701a4da..4b54dcf8d517 100644
--- a/kernel/time/posix-stubs.c
+++ b/kernel/time/posix-stubs.c
@@ -125,7 +125,7 @@ SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags,
return -EINVAL;
if (flags & TIMER_ABSTIME)
rmtp = NULL;
- current->restart_block.nanosleep.kind = rmtp ? 1 : 0;
+ current->restart_block.nanosleep.type = rmtp ? tt_native : tt_nothing;
current->restart_block.nanosleep.rmtp = rmtp;
return hrtimer_nanosleep(&t64, flags & TIMER_ABSTIME ?
HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
@@ -206,7 +206,7 @@ COMPAT_SYSCALL_DEFINE4(clock_nanosleep, clockid_t, which_clock, int, flags,
return -EINVAL;
if (flags & TIMER_ABSTIME)
rmtp = NULL;
- current->restart_block.nanosleep.kind = rmtp ? 2 : 0;
+ current->restart_block.nanosleep.type = rmtp ? tt_compat : tt_nothing;
current->restart_block.nanosleep.compat_rmtp = rmtp;
return hrtimer_nanosleep(&t64, flags & TIMER_ABSTIME ?
HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 014e6ff8982e..3c85d6762690 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -1228,7 +1228,7 @@ SYSCALL_DEFINE4(clock_nanosleep, const clockid_t, which_clock, int, flags,
return -EINVAL;
if (flags & TIMER_ABSTIME)
rmtp = NULL;
- current->restart_block.nanosleep.kind = rmtp ? 1 : 0;
+ current->restart_block.nanosleep.type = rmtp ? tt_native : tt_nothing;
current->restart_block.nanosleep.rmtp = rmtp;

return kc->nsleep(which_clock, flags, &t64);
@@ -1256,7 +1256,7 @@ COMPAT_SYSCALL_DEFINE4(clock_nanosleep, clockid_t, which_clock, int, flags,
return -EINVAL;
if (flags & TIMER_ABSTIME)
rmtp = NULL;
- current->restart_block.nanosleep.kind = rmtp ? 2 : 0;
+ current->restart_block.nanosleep.type = rmtp ? tt_compat : tt_nothing;
current->restart_block.nanosleep.compat_rmtp = rmtp;

return kc->nsleep(which_clock, flags, &t64);