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powerpc: Mark [h]ssr_valid accesses in check_return_regs_valid

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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 <rmclure@linux.ibm.com>
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230510033117.1395895-5-rmclure@linux.ibm.com
This commit is contained in:
Rohan McLure 2023-05-10 13:31:10 +10:00 committed by Michael Ellerman
parent 6f3136326e
commit be286b8637
2 changed files with 8 additions and 10 deletions
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4
arch/powerpc/include/asm/ptrace.h
View File

@ -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
}

14
arch/powerpc/kernel/interrupt.c
View File

@ -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
}