| Message ID | 20210203184323.20792-7-cmr@codefail.de (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Improve signal performance on PPC64 with KUAP | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (44158b256b30415079588d0fcb1bccbdc2ccd009) |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 135 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
Hi Chris, > Previously setup_sigcontext() performed a costly KUAP switch on every > uaccess operation. These repeated uaccess switches cause a significant > drop in signal handling performance. > > Rewrite setup_sigcontext() to assume that a userspace write access window > is open. Replace all uaccess functions with their 'unsafe' versions > which avoid the repeated uaccess switches. Just to clarify the commit message a bit: you're also changing the callers of the old safe versions to first open the window, then call the unsafe variants, then close the window again. > Signed-off-by: Christopher M. Riedl <cmr@codefail.de> > --- > arch/powerpc/kernel/signal_64.c | 70 ++++++++++++++++++++------------- > 1 file changed, 43 insertions(+), 27 deletions(-) > > diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c > index 8e1d804ce552..4248e4489ff1 100644 > --- a/arch/powerpc/kernel/signal_64.c > +++ b/arch/powerpc/kernel/signal_64.c > @@ -101,9 +101,13 @@ static void prepare_setup_sigcontext(struct task_struct *tsk, int ctx_has_vsx_re > * Set up the sigcontext for the signal frame. > */ > > -static long setup_sigcontext(struct sigcontext __user *sc, > - struct task_struct *tsk, int signr, sigset_t *set, > - unsigned long handler, int ctx_has_vsx_region) > +#define unsafe_setup_sigcontext(sc, tsk, signr, set, handler, \ > + ctx_has_vsx_region, e) \ > + unsafe_op_wrap(__unsafe_setup_sigcontext(sc, tsk, signr, set, \ > + handler, ctx_has_vsx_region), e) > +static long notrace __unsafe_setup_sigcontext(struct sigcontext __user *sc, > + struct task_struct *tsk, int signr, sigset_t *set, > + unsigned long handler, int ctx_has_vsx_region) > { > /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the > * process never used altivec yet (MSR_VEC is zero in pt_regs of > @@ -118,20 +122,19 @@ static long setup_sigcontext(struct sigcontext __user *sc, > #endif > struct pt_regs *regs = tsk->thread.regs; > unsigned long msr = regs->msr; > - long err = 0; > /* Force usr to alway see softe as 1 (interrupts enabled) */ > unsigned long softe = 0x1; > > BUG_ON(tsk != current); > > #ifdef CONFIG_ALTIVEC > - err |= __put_user(v_regs, &sc->v_regs); > + unsafe_put_user(v_regs, &sc->v_regs, efault_out); > > /* save altivec registers */ > if (tsk->thread.used_vr) { > /* Copy 33 vec registers (vr0..31 and vscr) to the stack */ > - err |= __copy_to_user(v_regs, &tsk->thread.vr_state, > - 33 * sizeof(vector128)); > + unsafe_copy_to_user(v_regs, &tsk->thread.vr_state, > + 33 * sizeof(vector128), efault_out); > /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg) > * contains valid data. > */ > @@ -140,12 +143,12 @@ static long setup_sigcontext(struct sigcontext __user *sc, > /* We always copy to/from vrsave, it's 0 if we don't have or don't > * use altivec. > */ > - err |= __put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33]); > + unsafe_put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33], efault_out); > #else /* CONFIG_ALTIVEC */ > - err |= __put_user(0, &sc->v_regs); > + unsafe_put_user(0, &sc->v_regs, efault_out); > #endif /* CONFIG_ALTIVEC */ > /* copy fpr regs and fpscr */ > - err |= copy_fpr_to_user(&sc->fp_regs, tsk); > + unsafe_copy_fpr_to_user(&sc->fp_regs, tsk, efault_out); > > /* > * Clear the MSR VSX bit to indicate there is no valid state attached > @@ -160,24 +163,27 @@ static long setup_sigcontext(struct sigcontext __user *sc, > */ > if (tsk->thread.used_vsr && ctx_has_vsx_region) { > v_regs += ELF_NVRREG; > - err |= copy_vsx_to_user(v_regs, tsk); > + unsafe_copy_vsx_to_user(v_regs, tsk, efault_out); > /* set MSR_VSX in the MSR value in the frame to > * indicate that sc->vs_reg) contains valid data. > */ > msr |= MSR_VSX; > } > #endif /* CONFIG_VSX */ > - err |= __put_user(&sc->gp_regs, &sc->regs); > + unsafe_put_user(&sc->gp_regs, &sc->regs, efault_out); > WARN_ON(!FULL_REGS(regs)); > - err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE); > - err |= __put_user(msr, &sc->gp_regs[PT_MSR]); > - err |= __put_user(softe, &sc->gp_regs[PT_SOFTE]); > - err |= __put_user(signr, &sc->signal); > - err |= __put_user(handler, &sc->handler); > + unsafe_copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE, efault_out); > + unsafe_put_user(msr, &sc->gp_regs[PT_MSR], efault_out); > + unsafe_put_user(softe, &sc->gp_regs[PT_SOFTE], efault_out); > + unsafe_put_user(signr, &sc->signal, efault_out); > + unsafe_put_user(handler, &sc->handler, efault_out); > if (set != NULL) > - err |= __put_user(set->sig[0], &sc->oldmask); > + unsafe_put_user(set->sig[0], &sc->oldmask, efault_out); > > - return err; > + return 0; > + > +efault_out: > + return -EFAULT; > } > > #ifdef CONFIG_PPC_TRANSACTIONAL_MEM > @@ -664,12 +670,15 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx, > > if (old_ctx != NULL) { > prepare_setup_sigcontext(current, ctx_has_vsx_region); > - if (!access_ok(old_ctx, ctx_size) > - || setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL, 0, > - ctx_has_vsx_region) > - || __copy_to_user(&old_ctx->uc_sigmask, > - ¤t->blocked, sizeof(sigset_t))) > + if (!user_write_access_begin(old_ctx, ctx_size)) > return -EFAULT; I notice we get rid of access_ok, but that's fine because user_write_access_begin includes access_ok since Linus decided that was a good idea. > + > + unsafe_setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL, > + 0, ctx_has_vsx_region, efault_out); > + unsafe_copy_to_user(&old_ctx->uc_sigmask, ¤t->blocked, > + sizeof(sigset_t), efault_out); > + > + user_write_access_end(); > } > if (new_ctx == NULL) > return 0; > @@ -698,6 +707,10 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx, > /* This returns like rt_sigreturn */ > set_thread_flag(TIF_RESTOREALL); > return 0; > + > +efault_out: > + user_write_access_end(); > + return -EFAULT; > } > > > @@ -850,9 +863,12 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set, > } else { > err |= __put_user(0, &frame->uc.uc_link); > prepare_setup_sigcontext(tsk, 1); > - err |= setup_sigcontext(&frame->uc.uc_mcontext, tsk, ksig->sig, > - NULL, (unsigned long)ksig->ka.sa.sa_handler, > - 1); > + if (!user_write_access_begin(frame, sizeof(struct rt_sigframe))) > + return -EFAULT; Here you're opening a window for all of `frame`... > + err |= __unsafe_setup_sigcontext(&frame->uc.uc_mcontext, tsk, ... but here you're only passing in frame->uc.uc_mcontext for writing. ISTR that the underlying AMR switch is fully on / fully off so I don't think it really matters, but in this case should you be calling user_write_access_begin() with &frame->uc.uc_mcontext and the size of that? > + ksig->sig, NULL, > + (unsigned long)ksig->ka.sa.sa_handler, 1); > + user_write_access_end(); > } > err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)); > if (err) Apart from the size thing, everything looks good to me. I checked that all the things you've changed from safe to unsafe pass the same parameters, and they all looked good to me. With those caveats, Reviewed-by: Daniel Axtens <dja@axtens.net> Kind regards, Daniel
On Thu Feb 11, 2021 at 11:41 PM CST, Daniel Axtens wrote: > Hi Chris, > > > Previously setup_sigcontext() performed a costly KUAP switch on every > > uaccess operation. These repeated uaccess switches cause a significant > > drop in signal handling performance. > > > > Rewrite setup_sigcontext() to assume that a userspace write access window > > is open. Replace all uaccess functions with their 'unsafe' versions > > which avoid the repeated uaccess switches. > > Just to clarify the commit message a bit: you're also changing the > callers of the old safe versions to first open the window, then call the > unsafe variants, then close the window again. Noted! > > > Signed-off-by: Christopher M. Riedl <cmr@codefail.de> > > --- > > arch/powerpc/kernel/signal_64.c | 70 ++++++++++++++++++++------------- > > 1 file changed, 43 insertions(+), 27 deletions(-) > > > > diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c > > index 8e1d804ce552..4248e4489ff1 100644 > > --- a/arch/powerpc/kernel/signal_64.c > > +++ b/arch/powerpc/kernel/signal_64.c > > @@ -101,9 +101,13 @@ static void prepare_setup_sigcontext(struct task_struct *tsk, int ctx_has_vsx_re > > * Set up the sigcontext for the signal frame. > > */ > > > > -static long setup_sigcontext(struct sigcontext __user *sc, > > - struct task_struct *tsk, int signr, sigset_t *set, > > - unsigned long handler, int ctx_has_vsx_region) > > +#define unsafe_setup_sigcontext(sc, tsk, signr, set, handler, \ > > + ctx_has_vsx_region, e) \ > > + unsafe_op_wrap(__unsafe_setup_sigcontext(sc, tsk, signr, set, \ > > + handler, ctx_has_vsx_region), e) > > +static long notrace __unsafe_setup_sigcontext(struct sigcontext __user *sc, > > + struct task_struct *tsk, int signr, sigset_t *set, > > + unsigned long handler, int ctx_has_vsx_region) > > { > > /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the > > * process never used altivec yet (MSR_VEC is zero in pt_regs of > > @@ -118,20 +122,19 @@ static long setup_sigcontext(struct sigcontext __user *sc, > > #endif > > struct pt_regs *regs = tsk->thread.regs; > > unsigned long msr = regs->msr; > > - long err = 0; > > /* Force usr to alway see softe as 1 (interrupts enabled) */ > > unsigned long softe = 0x1; > > > > BUG_ON(tsk != current); > > > > #ifdef CONFIG_ALTIVEC > > - err |= __put_user(v_regs, &sc->v_regs); > > + unsafe_put_user(v_regs, &sc->v_regs, efault_out); > > > > /* save altivec registers */ > > if (tsk->thread.used_vr) { > > /* Copy 33 vec registers (vr0..31 and vscr) to the stack */ > > - err |= __copy_to_user(v_regs, &tsk->thread.vr_state, > > - 33 * sizeof(vector128)); > > + unsafe_copy_to_user(v_regs, &tsk->thread.vr_state, > > + 33 * sizeof(vector128), efault_out); > > /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg) > > * contains valid data. > > */ > > @@ -140,12 +143,12 @@ static long setup_sigcontext(struct sigcontext __user *sc, > > /* We always copy to/from vrsave, it's 0 if we don't have or don't > > * use altivec. > > */ > > - err |= __put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33]); > > + unsafe_put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33], efault_out); > > #else /* CONFIG_ALTIVEC */ > > - err |= __put_user(0, &sc->v_regs); > > + unsafe_put_user(0, &sc->v_regs, efault_out); > > #endif /* CONFIG_ALTIVEC */ > > /* copy fpr regs and fpscr */ > > - err |= copy_fpr_to_user(&sc->fp_regs, tsk); > > + unsafe_copy_fpr_to_user(&sc->fp_regs, tsk, efault_out); > > > > /* > > * Clear the MSR VSX bit to indicate there is no valid state attached > > @@ -160,24 +163,27 @@ static long setup_sigcontext(struct sigcontext __user *sc, > > */ > > if (tsk->thread.used_vsr && ctx_has_vsx_region) { > > v_regs += ELF_NVRREG; > > - err |= copy_vsx_to_user(v_regs, tsk); > > + unsafe_copy_vsx_to_user(v_regs, tsk, efault_out); > > /* set MSR_VSX in the MSR value in the frame to > > * indicate that sc->vs_reg) contains valid data. > > */ > > msr |= MSR_VSX; > > } > > #endif /* CONFIG_VSX */ > > - err |= __put_user(&sc->gp_regs, &sc->regs); > > + unsafe_put_user(&sc->gp_regs, &sc->regs, efault_out); > > WARN_ON(!FULL_REGS(regs)); > > - err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE); > > - err |= __put_user(msr, &sc->gp_regs[PT_MSR]); > > - err |= __put_user(softe, &sc->gp_regs[PT_SOFTE]); > > - err |= __put_user(signr, &sc->signal); > > - err |= __put_user(handler, &sc->handler); > > + unsafe_copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE, efault_out); > > + unsafe_put_user(msr, &sc->gp_regs[PT_MSR], efault_out); > > + unsafe_put_user(softe, &sc->gp_regs[PT_SOFTE], efault_out); > > + unsafe_put_user(signr, &sc->signal, efault_out); > > + unsafe_put_user(handler, &sc->handler, efault_out); > > if (set != NULL) > > - err |= __put_user(set->sig[0], &sc->oldmask); > > + unsafe_put_user(set->sig[0], &sc->oldmask, efault_out); > > > > - return err; > > + return 0; > > + > > +efault_out: > > + return -EFAULT; > > } > > > > #ifdef CONFIG_PPC_TRANSACTIONAL_MEM > > @@ -664,12 +670,15 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx, > > > > if (old_ctx != NULL) { > > prepare_setup_sigcontext(current, ctx_has_vsx_region); > > - if (!access_ok(old_ctx, ctx_size) > > - || setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL, 0, > > - ctx_has_vsx_region) > > - || __copy_to_user(&old_ctx->uc_sigmask, > > - ¤t->blocked, sizeof(sigset_t))) > > + if (!user_write_access_begin(old_ctx, ctx_size)) > > return -EFAULT; > > I notice we get rid of access_ok, but that's fine because > user_write_access_begin includes access_ok since Linus decided that was > a good idea. > > > + > > + unsafe_setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL, > > + 0, ctx_has_vsx_region, efault_out); > > + unsafe_copy_to_user(&old_ctx->uc_sigmask, ¤t->blocked, > > + sizeof(sigset_t), efault_out); > > + > > + user_write_access_end(); > > } > > if (new_ctx == NULL) > > return 0; > > @@ -698,6 +707,10 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx, > > /* This returns like rt_sigreturn */ > > set_thread_flag(TIF_RESTOREALL); > > return 0; > > + > > +efault_out: > > + user_write_access_end(); > > + return -EFAULT; > > } > > > > > > @@ -850,9 +863,12 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set, > > } else { > > err |= __put_user(0, &frame->uc.uc_link); > > prepare_setup_sigcontext(tsk, 1); > > - err |= setup_sigcontext(&frame->uc.uc_mcontext, tsk, ksig->sig, > > - NULL, (unsigned long)ksig->ka.sa.sa_handler, > > - 1); > > + if (!user_write_access_begin(frame, sizeof(struct rt_sigframe))) > > + return -EFAULT; > > Here you're opening a window for all of `frame`... > > > + err |= __unsafe_setup_sigcontext(&frame->uc.uc_mcontext, tsk, > ... but here you're only passing in frame->uc.uc_mcontext for writing. > > ISTR that the underlying AMR switch is fully on / fully off so I don't > think it really matters, but in this case should you be calling > user_write_access_begin() with &frame->uc.uc_mcontext and the size of > that? You are correct that it doesn't _really_ matter w/ the current implementation of KUAP/AMR. It's still inconsistent and could cause problems in the future so I will fix this to pass the proper size. > > > + ksig->sig, NULL, > > + (unsigned long)ksig->ka.sa.sa_handler, 1); > > + user_write_access_end(); > > } > > err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)); > > if (err) > > > Apart from the size thing, everything looks good to me. I checked that > all the things you've changed from safe to unsafe pass the same > parameters, and they all looked good to me. Thanks! > > With those caveats, > Reviewed-by: Daniel Axtens <dja@axtens.net> > > Kind regards, > Daniel
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c index 8e1d804ce552..4248e4489ff1 100644 --- a/arch/powerpc/kernel/signal_64.c +++ b/arch/powerpc/kernel/signal_64.c @@ -101,9 +101,13 @@ static void prepare_setup_sigcontext(struct task_struct *tsk, int ctx_has_vsx_re * Set up the sigcontext for the signal frame. */ -static long setup_sigcontext(struct sigcontext __user *sc, - struct task_struct *tsk, int signr, sigset_t *set, - unsigned long handler, int ctx_has_vsx_region) +#define unsafe_setup_sigcontext(sc, tsk, signr, set, handler, \ + ctx_has_vsx_region, e) \ + unsafe_op_wrap(__unsafe_setup_sigcontext(sc, tsk, signr, set, \ + handler, ctx_has_vsx_region), e) +static long notrace __unsafe_setup_sigcontext(struct sigcontext __user *sc, + struct task_struct *tsk, int signr, sigset_t *set, + unsigned long handler, int ctx_has_vsx_region) { /* When CONFIG_ALTIVEC is set, we _always_ setup v_regs even if the * process never used altivec yet (MSR_VEC is zero in pt_regs of @@ -118,20 +122,19 @@ static long setup_sigcontext(struct sigcontext __user *sc, #endif struct pt_regs *regs = tsk->thread.regs; unsigned long msr = regs->msr; - long err = 0; /* Force usr to alway see softe as 1 (interrupts enabled) */ unsigned long softe = 0x1; BUG_ON(tsk != current); #ifdef CONFIG_ALTIVEC - err |= __put_user(v_regs, &sc->v_regs); + unsafe_put_user(v_regs, &sc->v_regs, efault_out); /* save altivec registers */ if (tsk->thread.used_vr) { /* Copy 33 vec registers (vr0..31 and vscr) to the stack */ - err |= __copy_to_user(v_regs, &tsk->thread.vr_state, - 33 * sizeof(vector128)); + unsafe_copy_to_user(v_regs, &tsk->thread.vr_state, + 33 * sizeof(vector128), efault_out); /* set MSR_VEC in the MSR value in the frame to indicate that sc->v_reg) * contains valid data. */ @@ -140,12 +143,12 @@ static long setup_sigcontext(struct sigcontext __user *sc, /* We always copy to/from vrsave, it's 0 if we don't have or don't * use altivec. */ - err |= __put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33]); + unsafe_put_user(tsk->thread.vrsave, (u32 __user *)&v_regs[33], efault_out); #else /* CONFIG_ALTIVEC */ - err |= __put_user(0, &sc->v_regs); + unsafe_put_user(0, &sc->v_regs, efault_out); #endif /* CONFIG_ALTIVEC */ /* copy fpr regs and fpscr */ - err |= copy_fpr_to_user(&sc->fp_regs, tsk); + unsafe_copy_fpr_to_user(&sc->fp_regs, tsk, efault_out); /* * Clear the MSR VSX bit to indicate there is no valid state attached @@ -160,24 +163,27 @@ static long setup_sigcontext(struct sigcontext __user *sc, */ if (tsk->thread.used_vsr && ctx_has_vsx_region) { v_regs += ELF_NVRREG; - err |= copy_vsx_to_user(v_regs, tsk); + unsafe_copy_vsx_to_user(v_regs, tsk, efault_out); /* set MSR_VSX in the MSR value in the frame to * indicate that sc->vs_reg) contains valid data. */ msr |= MSR_VSX; } #endif /* CONFIG_VSX */ - err |= __put_user(&sc->gp_regs, &sc->regs); + unsafe_put_user(&sc->gp_regs, &sc->regs, efault_out); WARN_ON(!FULL_REGS(regs)); - err |= __copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE); - err |= __put_user(msr, &sc->gp_regs[PT_MSR]); - err |= __put_user(softe, &sc->gp_regs[PT_SOFTE]); - err |= __put_user(signr, &sc->signal); - err |= __put_user(handler, &sc->handler); + unsafe_copy_to_user(&sc->gp_regs, regs, GP_REGS_SIZE, efault_out); + unsafe_put_user(msr, &sc->gp_regs[PT_MSR], efault_out); + unsafe_put_user(softe, &sc->gp_regs[PT_SOFTE], efault_out); + unsafe_put_user(signr, &sc->signal, efault_out); + unsafe_put_user(handler, &sc->handler, efault_out); if (set != NULL) - err |= __put_user(set->sig[0], &sc->oldmask); + unsafe_put_user(set->sig[0], &sc->oldmask, efault_out); - return err; + return 0; + +efault_out: + return -EFAULT; } #ifdef CONFIG_PPC_TRANSACTIONAL_MEM @@ -664,12 +670,15 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx, if (old_ctx != NULL) { prepare_setup_sigcontext(current, ctx_has_vsx_region); - if (!access_ok(old_ctx, ctx_size) - || setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL, 0, - ctx_has_vsx_region) - || __copy_to_user(&old_ctx->uc_sigmask, - ¤t->blocked, sizeof(sigset_t))) + if (!user_write_access_begin(old_ctx, ctx_size)) return -EFAULT; + + unsafe_setup_sigcontext(&old_ctx->uc_mcontext, current, 0, NULL, + 0, ctx_has_vsx_region, efault_out); + unsafe_copy_to_user(&old_ctx->uc_sigmask, ¤t->blocked, + sizeof(sigset_t), efault_out); + + user_write_access_end(); } if (new_ctx == NULL) return 0; @@ -698,6 +707,10 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx, /* This returns like rt_sigreturn */ set_thread_flag(TIF_RESTOREALL); return 0; + +efault_out: + user_write_access_end(); + return -EFAULT; } @@ -850,9 +863,12 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set, } else { err |= __put_user(0, &frame->uc.uc_link); prepare_setup_sigcontext(tsk, 1); - err |= setup_sigcontext(&frame->uc.uc_mcontext, tsk, ksig->sig, - NULL, (unsigned long)ksig->ka.sa.sa_handler, - 1); + if (!user_write_access_begin(frame, sizeof(struct rt_sigframe))) + return -EFAULT; + err |= __unsafe_setup_sigcontext(&frame->uc.uc_mcontext, tsk, + ksig->sig, NULL, + (unsigned long)ksig->ka.sa.sa_handler, 1); + user_write_access_end(); } err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)); if (err)
Previously setup_sigcontext() performed a costly KUAP switch on every uaccess operation. These repeated uaccess switches cause a significant drop in signal handling performance. Rewrite setup_sigcontext() to assume that a userspace write access window is open. Replace all uaccess functions with their 'unsafe' versions which avoid the repeated uaccess switches. Signed-off-by: Christopher M. Riedl <cmr@codefail.de> --- arch/powerpc/kernel/signal_64.c | 70 ++++++++++++++++++++------------- 1 file changed, 43 insertions(+), 27 deletions(-)