From be286b8637d417a7d7eb25dc3a509c10d0afef66 Mon Sep 17 00:00:00 2001 From: Rohan McLure Date: Wed, 10 May 2023 13:31:10 +1000 Subject: [PATCH] powerpc: Mark [h]ssr_valid accesses in check_return_regs_valid Checks to see if the [H]SRR registers have been clobbered by (soft) NMI interrupts imply the possibility for a data race on the [h]srr_valid entries in the PACA. Annotate accesses to these fields with READ_ONCE, removing the need for the barrier. The diagnostic can use plain-access reads and writes, but annotate with data_race. Signed-off-by: Rohan McLure Reported-by: Michael Ellerman Reviewed-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://msgid.link/20230510033117.1395895-5-rmclure@linux.ibm.com --- arch/powerpc/include/asm/ptrace.h | 4 ++-- arch/powerpc/kernel/interrupt.c | 14 ++++++-------- 2 files changed, 8 insertions(+), 10 deletions(-) diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h index 0eb90a0..9db8b16 100644 --- a/arch/powerpc/include/asm/ptrace.h +++ b/arch/powerpc/include/asm/ptrace.h @@ -180,8 +180,8 @@ void do_syscall_trace_leave(struct pt_regs *regs); static inline void set_return_regs_changed(void) { #ifdef CONFIG_PPC_BOOK3S_64 - local_paca->hsrr_valid = 0; - local_paca->srr_valid = 0; + WRITE_ONCE(local_paca->hsrr_valid, 0); + WRITE_ONCE(local_paca->srr_valid, 0); #endif } diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c index f3fc5fe..c4f6d3c 100644 --- a/arch/powerpc/kernel/interrupt.c +++ b/arch/powerpc/kernel/interrupt.c @@ -125,7 +125,7 @@ static notrace void check_return_regs_valid(struct pt_regs *regs) case 0x1600: case 0x1800: validp = &local_paca->hsrr_valid; - if (!*validp) + if (!READ_ONCE(*validp)) return; srr0 = mfspr(SPRN_HSRR0); @@ -135,7 +135,7 @@ static notrace void check_return_regs_valid(struct pt_regs *regs) break; default: validp = &local_paca->srr_valid; - if (!*validp) + if (!READ_ONCE(*validp)) return; srr0 = mfspr(SPRN_SRR0); @@ -161,19 +161,17 @@ static notrace void check_return_regs_valid(struct pt_regs *regs) * such things will get caught most of the time, statistically * enough to be able to get a warning out. */ - barrier(); - - if (!*validp) + if (!READ_ONCE(*validp)) return; - if (!warned) { - warned = true; + if (!data_race(warned)) { + data_race(warned = true); printk("%sSRR0 was: %lx should be: %lx\n", h, srr0, regs->nip); printk("%sSRR1 was: %lx should be: %lx\n", h, srr1, regs->msr); show_regs(regs); } - *validp = 0; /* fixup */ + WRITE_ONCE(*validp, 0); /* fixup */ #endif } -- 2.7.4