Commit be286b86 authored by Rohan McLure's avatar Rohan McLure Committed by Michael Ellerman
Browse files

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: default avatarRohan McLure <rmclure@linux.ibm.com>
Reported-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Reviewed-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230510033117.1395895-5-rmclure@linux.ibm.com
parent 6f313632

arch/powerpc/include/asm/ptrace.h

+2 −2
Original line number Diff line number Diff line
@@ -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

}

arch/powerpc/kernel/interrupt.c

+6 −8
Original line number Diff line number Diff line
@@ -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

}