The PPC_RFI_SRR_DEBUG check added by patch "powerpc/64s: avoid reloading
(H)SRR registers if they are still valid" has a few deficiencies. It
does not fix the actual problem, it's not enabled by default, and it
causes a program check interrupt which can cause more difficulties.
However there are a lot of paths which may clobber SRRs or change return
regs, and difficult to have a high confidence that all paths are covered
without wider testing.
Add a relatively low overhead always-enabled check that catches most
such cases, reports once, and fixes it so the kernel can continue.
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
arch/powerpc/kernel/interrupt.c | 58 +++++++++++++++++++++++++++++++++
1 file changed, 58 insertions(+)
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 05fa3ae56e25..5920a3e8d1d5 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -231,6 +231,56 @@ static notrace void booke_load_dbcr0(void)
#endif
}
+#include <linux/sched/debug.h> /* for show_regs */
+static void check_return_regs_valid(struct pt_regs *regs)
+{
+#ifdef CONFIG_PPC_BOOK3S_64
+ static bool warned = false;
+
+ if (regs->trap == 0x980 || regs->trap == 0xe00 || regs->trap == 0xe20 ||
+ regs->trap == 0xe40 || regs->trap == 0xe60 || regs->trap == 0xe80 ||
+ regs->trap == 0xea0 || regs->trap == 0xf80 || regs->trap == 0x1200
||
+ regs->trap == 0x1500 || regs->trap == 0x1600 || regs->trap ==
0x1800) {
+ if (local_paca->hsrr_valid) {
+ unsigned long hsrr0 = mfspr(SPRN_HSRR0);
+ unsigned long hsrr1 = mfspr(SPRN_HSRR1);
+
+ if (hsrr0 == regs->nip && hsrr1 == regs->msr)
+ return;
+
+ if (!warned) {
+ warned = true;
+ printk("HSRR0 was: %lx should be: %lx\n",
+ hsrr0, regs->nip);
+ printk("HSRR1 was: %lx should be: %lx\n",
+ hsrr1, regs->msr);
+ show_regs(regs);
+ }
+ local_paca->hsrr_valid = 0; /* fixup */
+ }
+
+ } else if (regs->trap != 0x3000) {
+ if (local_paca->srr_valid) {
+ unsigned long srr0 = mfspr(SPRN_SRR0);
+ unsigned long srr1 = mfspr(SPRN_SRR1);
+
+ if (srr0 == regs->nip && srr1 == regs->msr)
+ return;
+
+ if (!warned) {
+ warned = true;
+ printk("SRR0 was: %lx should be: %lx\n",
+ srr0, regs->nip);
+ printk("SRR1 was: %lx should be: %lx\n",
+ srr1, regs->msr);
+ show_regs(regs);
+ }
+ local_paca->srr_valid = 0; /* fixup */
+ }
+ }
+#endif
+}
+
/*
* This should be called after a syscall returns, with r3 the return value
* from the syscall. If this function returns non-zero, the system call
@@ -327,6 +377,8 @@ notrace unsigned long syscall_exit_prepare(unsigned long r3,
}
}
+ check_return_regs_valid(regs);
+
user_enter_irqoff();
/* scv need not set RI=0 because SRRs are not used */
@@ -405,6 +457,8 @@ notrace unsigned long interrupt_exit_user_prepare(struct
pt_regs *regs)
}
}
+ check_return_regs_valid(regs);
+
user_enter_irqoff();
if (unlikely(!__prep_irq_for_enabled_exit(true))) {
@@ -469,9 +523,13 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct
pt_regs *regs)
}
}
+ check_return_regs_valid(regs);
+
if (unlikely(!prep_irq_for_enabled_exit(true,
!irqs_disabled_flags(flags))))
goto again;
} else {
+ check_return_regs_valid(regs);
+
/* Returning to a kernel context with local irqs disabled. */
__hard_EE_RI_disable();
#ifdef CONFIG_PPC64
--
2.23.0
