[PATCH 4.14 185/189] ARM: kexec: fix kdump register saving on panic()

Greg Kroah-Hartman
2018-06-18T08:38:42Z

From: Russell King <rmk+kernel@armlinux.org.uk>

[ Upstream commit 2d7b3c64431245c95b05a441669c074da10db943 ]

When a panic() occurs, the kexec code uses smp_send_stop() to stop
the other CPUs, but this results in the CPU register state not being
saved, and gdb is unable to inspect the state of other CPUs.

Commit 0ee59413c967 ("x86/panic: replace smp_send_stop() with kdump
friendly version in panic path") addressed the issue on x86, but
ignored other architectures. Address the issue on ARM by splitting
out the crash stop implementation to crash_smp_send_stop() and
adding the necessary protection.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm/kernel/machine_kexec.c | 34 ++++++++++++++++++++++------------
1 file changed, 22 insertions(+), 12 deletions(-)

--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -95,6 +95,27 @@ void machine_crash_nonpanic_core(void *u
cpu_relax();
}

+void crash_smp_send_stop(void)
+{
+ static int cpus_stopped;
+ unsigned long msecs;
+
+ if (cpus_stopped)
+ return;
+
+ atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
+ smp_call_function(machine_crash_nonpanic_core, NULL, false);
+ msecs = 1000; /* Wait at most a second for the other cpus to stop */
+ while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
+ mdelay(1);
+ msecs--;
+ }
+ if (atomic_read(&waiting_for_crash_ipi) > 0)
+ pr_warn("Non-crashing CPUs did not react to IPI\n");
+
+ cpus_stopped = 1;
+}
+
static void machine_kexec_mask_interrupts(void)
{
unsigned int i;
@@ -120,19 +141,8 @@ static void machine_kexec_mask_interrupt

void machine_crash_shutdown(struct pt_regs *regs)
{
- unsigned long msecs;
-
local_irq_disable();
-
- atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
- smp_call_function(machine_crash_nonpanic_core, NULL, false);
- msecs = 1000; /* Wait at most a second for the other cpus to stop */
- while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
- mdelay(1);
- msecs--;
- }
- if (atomic_read(&waiting_for_crash_ipi) > 0)
- pr_warn("Non-crashing CPUs did not react to IPI\n");
+ crash_smp_send_stop();

crash_save_cpu(regs, smp_processor_id());
machine_kexec_mask_interrupts();