From: Daniel Axtens <d...@axtens.net>
Previously setup_trampoline() performed a costly KUAP switch on every
uaccess operation. These repeated uaccess switches cause a significant
drop in signal handling performance.
Rewrite setup_trampoline() to assume that a userspace write access
window is open. Replace all uaccess functions with their 'unsafe'
versions to avoid the repeated uaccess switches.
Signed-off-by: Daniel Axtens <d...@axtens.net>
Signed-off-by: Christopher M. Riedl <c...@codefail.de>
---
arch/powerpc/kernel/signal_64.c | 32 +++++++++++++++++++-------------
1 file changed, 19 insertions(+), 13 deletions(-)
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index bd92064e5576..6d4f7a5c4fbf 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -600,30 +600,33 @@ static long restore_tm_sigcontexts(struct task_struct
*tsk,
/*
* Setup the trampoline code on the stack
*/
-static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
+#define unsafe_setup_trampoline(syscall, tramp, e) \
+ unsafe_op_wrap(__unsafe_setup_trampoline(syscall, tramp), e)
+static long notrace __unsafe_setup_trampoline(unsigned int syscall,
+ unsigned int __user *tramp)
{
int i;
- long err = 0;
/* bctrl # call the handler */
- err |= __put_user(PPC_INST_BCTRL, &tramp[0]);
+ unsafe_put_user(PPC_INST_BCTRL, &tramp[0], err);
/* addi r1, r1, __SIGNAL_FRAMESIZE # Pop the dummy stackframe */
- err |= __put_user(PPC_INST_ADDI | __PPC_RT(R1) | __PPC_RA(R1) |
- (__SIGNAL_FRAMESIZE & 0xffff), &tramp[1]);
+ unsafe_put_user(PPC_INST_ADDI | __PPC_RT(R1) | __PPC_RA(R1) |
+ (__SIGNAL_FRAMESIZE & 0xffff), &tramp[1], err);
/* li r0, __NR_[rt_]sigreturn| */
- err |= __put_user(PPC_INST_ADDI | (syscall & 0xffff), &tramp[2]);
+ unsafe_put_user(PPC_INST_ADDI | (syscall & 0xffff), &tramp[2], err);
/* sc */
- err |= __put_user(PPC_INST_SC, &tramp[3]);
+ unsafe_put_user(PPC_INST_SC, &tramp[3], err);
/* Minimal traceback info */
for (i=TRAMP_TRACEBACK; i < TRAMP_SIZE ;i++)
- err |= __put_user(0, &tramp[i]);
+ unsafe_put_user(0, &tramp[i], err);
- if (!err)
- flush_icache_range((unsigned long) &tramp[0],
- (unsigned long) &tramp[TRAMP_SIZE]);
+ flush_icache_range((unsigned long)&tramp[0],
+ (unsigned long)&tramp[TRAMP_SIZE]);
- return err;
+ return 0;
+err:
+ return 1;
}
/*
@@ -888,7 +891,10 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
if (vdso64_rt_sigtramp && tsk->mm->context.vdso_base) {
regs->nip = tsk->mm->context.vdso_base + vdso64_rt_sigtramp;
} else {
- err |= setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
+ if (!user_write_access_begin(frame, sizeof(struct rt_sigframe)))
+ return -EFAULT;
+ err |= __unsafe_setup_trampoline(__NR_rt_sigreturn,
&frame->tramp[0]);
+ user_write_access_end();
if (err)
goto badframe;
regs->nip = (unsigned long) &frame->tramp[0];
--
2.28.0
