[PATCH v2] powerpc: Fix save_stack_trace_regs() to have running function as first entry
From: Christophe Leroy
Date: Wed Mar 03 2021 - 13:57:26 EST
It seems like other architectures, namely x86 and arm64
at least, include the running function as top entry when saving
stack trace with save_stack_trace_regs().
Functionnalities like KFENCE expect it.
Do the same on powerpc, it allows KFENCE to properly identify the faulting
function as depicted below. Before the patch KFENCE was identifying
finish_task_switch.isra as the faulting function.
[ 14.937370] ==================================================================
[ 14.948692] BUG: KFENCE: invalid read in test_invalid_access+0x54/0x108
[ 14.948692]
[ 14.956814] Invalid read at 0xdf98800a:
[ 14.960664] test_invalid_access+0x54/0x108
[ 14.964876] finish_task_switch.isra.0+0x54/0x23c
[ 14.969606] kunit_try_run_case+0x5c/0xd0
[ 14.973658] kunit_generic_run_threadfn_adapter+0x24/0x30
[ 14.979079] kthread+0x15c/0x174
[ 14.982342] ret_from_kernel_thread+0x14/0x1c
[ 14.986731]
[ 14.988236] CPU: 0 PID: 111 Comm: kunit_try_catch Tainted: G B 5.12.0-rc1-01537-g95f6e2088d7e-dirty #4682
[ 14.999795] NIP: c016ec2c LR: c02f517c CTR: c016ebd8
[ 15.004851] REGS: e2449d90 TRAP: 0301 Tainted: G B (5.12.0-rc1-01537-g95f6e2088d7e-dirty)
[ 15.015274] MSR: 00009032 <EE,ME,IR,DR,RI> CR: 22000004 XER: 00000000
[ 15.022043] DAR: df98800a DSISR: 20000000
[ 15.022043] GPR00: c02f517c e2449e50 c1142080 e100dd24 c084b13c 00000008 c084b32b c016ebd8
[ 15.022043] GPR08: c0850000 df988000 c0d10000 e2449eb0 22000288
[ 15.040581] NIP [c016ec2c] test_invalid_access+0x54/0x108
[ 15.046010] LR [c02f517c] kunit_try_run_case+0x5c/0xd0
[ 15.051181] Call Trace:
[ 15.053637] [e2449e50] [c005a68c] finish_task_switch.isra.0+0x54/0x23c (unreliable)
[ 15.061338] [e2449eb0] [c02f517c] kunit_try_run_case+0x5c/0xd0
[ 15.067215] [e2449ed0] [c02f648c] kunit_generic_run_threadfn_adapter+0x24/0x30
[ 15.074472] [e2449ef0] [c004e7b0] kthread+0x15c/0x174
[ 15.079571] [e2449f30] [c001317c] ret_from_kernel_thread+0x14/0x1c
[ 15.085798] Instruction dump:
[ 15.088784] 8129d608 38e7ebd8 81020280 911f004c 39000000 995f0024 907f0028 90ff001c
[ 15.096613] 3949000a 915f0020 3d40c0d1 3d00c085 <8929000a> 3908adb0 812a4b98 3d40c02f
[ 15.104612] ==================================================================
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Fixes: 35de3b1aa168 ("powerpc: Implement save_stack_trace_regs() to enable kprobe stack tracing")
Cc: stable@xxxxxxxxxxxxxxx
Acked-by: Marco Elver <elver@xxxxxxxxxx>
---
arch/powerpc/kernel/stacktrace.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)
diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c
index b6440657ef92..a99bd3697286 100644
--- a/arch/powerpc/kernel/stacktrace.c
+++ b/arch/powerpc/kernel/stacktrace.c
@@ -23,6 +23,18 @@
#include <asm/paca.h>
+static bool save_entry(struct stack_trace *trace, unsigned long ip, int savesched)
+{
+ if (savesched || !in_sched_functions(ip)) {
+ if (!trace->skip)
+ trace->entries[trace->nr_entries++] = ip;
+ else
+ trace->skip--;
+ }
+ /* Returns true when the trace is full */
+ return trace->nr_entries >= trace->max_entries;
+}
+
/*
* Save stack-backtrace addresses into a stack_trace buffer.
*/
@@ -39,14 +51,7 @@ static void save_context_stack(struct stack_trace *trace, unsigned long sp,
newsp = stack[0];
ip = stack[STACK_FRAME_LR_SAVE];
- if (savesched || !in_sched_functions(ip)) {
- if (!trace->skip)
- trace->entries[trace->nr_entries++] = ip;
- else
- trace->skip--;
- }
-
- if (trace->nr_entries >= trace->max_entries)
+ if (save_entry(trace, ip, savesched))
return;
sp = newsp;
@@ -84,6 +89,9 @@ EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
void
save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
{
+ if (save_entry(trace, regs->nip, 0))
+ return;
+
save_context_stack(trace, regs->gpr[1], current, 0);
}
EXPORT_SYMBOL_GPL(save_stack_trace_regs);
--
2.25.0