[PATCH 4/8] powerpc/signal64: Replace setup_sigcontext() w/ unsafe_setup_sigcontext()
From: Christopher M. Riedl <hidden>
Date: 2020-10-15 15:29:06
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
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 <redacted> --- arch/powerpc/kernel/signal_64.c | 71 ++++++++++++++++++++------------- 1 file changed, 44 insertions(+), 27 deletions(-)
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 7df088b9ad0f..26934ceeb925 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c@@ -83,9 +83,13 @@ static elf_vrreg_t __user *sigcontext_vmx_regs(struct sigcontext __user *sc) * 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
@@ -101,21 +105,20 @@ 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) { flush_altivec_to_thread(tsk); /* 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. */
@@ -130,13 +133,13 @@ static long setup_sigcontext(struct sigcontext __user *sc, tsk->thread.vrsave = vrsave; } - err |= __put_user(vrsave, (u32 __user *)&v_regs[33]); + unsafe_put_user(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 */ flush_fp_to_thread(tsk); /* 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
@@ -152,24 +155,27 @@ static long setup_sigcontext(struct sigcontext __user *sc, if (tsk->thread.used_vsr && ctx_has_vsx_region) { flush_vsx_to_thread(tsk); 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
@@ -655,12 +661,15 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx, ctx_has_vsx_region = 1; if (old_ctx != NULL) { - 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;
@@ -689,6 +698,10 @@ 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; }
@@ -842,9 +855,13 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set, #endif { err |= __put_user(0, &frame->uc.uc_link); - 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)
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2.28.0