[PATCH v2 04/11] powerpc: Mark [h]ssr_valid accesses in check_return_regs_valid
From: Rohan McLure <hidden>
Date: 2023-05-10 03:40:13
Subsystem:
linux for powerpc (32-bit and 64-bit), ptrace support, the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Oleg Nesterov, Linus Torvalds
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 <redacted> Reported-by: Michael Ellerman <mpe@ellerman.id.au> Reviewed-by: Nicholas Piggin <npiggin@gmail.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 0eb90a013346..9db8b16567e2 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 e34c72285b4e..1f033f11b871 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 }
--
2.37.2