iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

powerpc/signal64: Replace setup_sigcontext() w/ unsafe_setup_sigcontext()

Browse Source 
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 by replacing all uaccess functions with their 'unsafe' versions.
Modify the callers to first open, call unsafe_setup_sigcontext() and
then close the uaccess window.

Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210227011259.11992-7-cmr@codefail.de
This commit is contained in:
Christopher M. Riedl 2021-02-26 19:12:55 -06:00 committed by Michael Ellerman
parent 2d19630e20
commit 7bb081c8f0
1 changed files with 45 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

72
arch/powerpc/kernel/signal_64.c
View File

@ -101,9 +101,14 @@ static void prepare_setup_sigcontext(struct task_struct *tsk)
* 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, label)\
do { \
if (__unsafe_setup_sigcontext(sc, tsk, signr, set, handler, ctx_has_vsx_region))\
goto label; \
} while (0)
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 +123,19 @@ 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 +144,12 @@ 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 +164,27 @@ 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
@ -670,12 +677,15 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
if (old_ctx != NULL) {
prepare_setup_sigcontext(current);
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,
&current->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, &current->blocked,
sizeof(sigset_t), efault_out);
user_write_access_end();
}
if (new_ctx == NULL)
return 0;
@ -704,6 +714,10 @@ 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;
}
@ -854,9 +868,13 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
} else {
err |= __put_user(0, &frame->uc.uc_link);
prepare_setup_sigcontext(tsk);
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->uc.uc_mcontext,
sizeof(frame->uc.uc_mcontext)))
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)