lkml.org 
[lkml]   [2020]   [Aug]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC PATCH v1 18/19] powerpc/signal32: Add and use unsafe_put_sigset_t()
Date
put_sigset_t() calls copy_to_user() for copying two words.

Because INLINE_COPY_TO_USER is not defined on powerpc,
copy_to_user() doesn't get optimised and falls back to
copy_tofrom_user() with the relevant glue. This is terribly
inefficient for copying two words.

By switching to unsafe_put_user(), we end up with something as
simple as:

3cc: 81 3d 00 00 lwz r9,0(r29)
3d0: 91 26 00 b4 stw r9,180(r6)
3d4: 81 3d 00 04 lwz r9,4(r29)
3d8: 91 26 00 b8 stw r9,184(r6)

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/kernel/signal_32.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index d03ba3d8eb68..6cbff0293ff4 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -87,6 +87,8 @@ static inline int put_sigset_t(compat_sigset_t __user *uset, sigset_t *set)
return put_compat_sigset(uset, set, sizeof(*uset));
}

+#define unsafe_put_sigset_t unsafe_put_compat_sigset
+
static inline int get_sigset_t(sigset_t *set,
const compat_sigset_t __user *uset)
{
@@ -143,6 +145,13 @@ static inline int put_sigset_t(sigset_t __user *uset, sigset_t *set)
return copy_to_user(uset, set, sizeof(*uset));
}

+#define unsafe_put_sigset_t(uset, set, label) do { \
+ sigset_t __user *__us = uset ; \
+ const sigset_t *__s = set; \
+ \
+ unsafe_copy_to_user(__us, __s, sizeof(*__us), label); \
+} while (0)
+
static inline int get_sigset_t(sigset_t *set, const sigset_t __user *uset)
{
return copy_from_user(set, uset, sizeof(*uset));
@@ -820,10 +829,11 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset,
{
unsafe_put_user(0, &rt_sf->uc.uc_link, failed);
}
+
+ unsafe_put_sigset_t(&rt_sf->uc.uc_sigmask, oldset, failed);
+
user_write_access_end();

- if (put_sigset_t(&rt_sf->uc.uc_sigmask, oldset))
- goto badframe;
if (copy_siginfo_to_user(&rt_sf->info, &ksig->info))
goto badframe;

--
2.25.0
\
 
 \ /
  Last update: 2020-08-12 14:07    [W:0.081 / U:0.832 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site