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powerpc/signal32: Add and use unsafe_put_sigset_t() 

put_sigset_t() calls copy_to_user() for copying two words.

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>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/06def97e87ac1c4ae8e3197e0982e1fab7b3c8ae.1597770847.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2020-08-18 17:19:33 +00:00 committed by Michael Ellerman
parent 14026b94cc
commit de781ebdf6
1 changed files with 11 additions and 2 deletions
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13
arch/powerpc/kernel/signal_32.c
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@ -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)
{
@ -141,6 +143,13 @@ 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));
@ -780,10 +789,10 @@ int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset,
failed);
unsafe_put_user(PPC_INST_SC, &mctx->mc_pad[1], failed);
}
unsafe_put_sigset_t(&frame->uc.uc_sigmask, oldset, failed);
user_write_access_end();
if (put_sigset_t(&frame->uc.uc_sigmask, oldset))
goto badframe;
if (copy_siginfo_to_user(&frame->info, &ksig->info))
goto badframe;