From a2308836880bf1501ff9373c611dc2970247d42b Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Tue, 16 Mar 2021 07:57:16 +0000 Subject: [PATCH] powerpc: Fix arch_stack_walk() to have running function as first entry It seems like other architectures, namely x86 and arm64 and riscv 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 and other users 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 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] ================================================================== Fixes: 35de3b1aa168 ("powerpc: Implement save_stack_trace_regs() to enable kprobe stack tracing") Signed-off-by: Christophe Leroy Acked-by: Marco Elver Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/21324f9e2f21d1640c8397b4d1d857a9355a2283.1615881400.git.christophe.leroy@csgroup.eu --- arch/powerpc/kernel/stacktrace.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c index 80f92f5b5393..1deb1bf331dd 100644 --- a/arch/powerpc/kernel/stacktrace.c +++ b/arch/powerpc/kernel/stacktrace.c @@ -28,6 +28,9 @@ void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie, { unsigned long sp; + if (regs && !consume_entry(cookie, regs->nip)) + return; + if (regs) sp = regs->gpr[1]; else if (task == current)