From 09cffecaa7703fd4c54b25f6c21c3a93e87c2e8f Mon Sep 17 00:00:00 2001 From: Zhen Lei Date: Wed, 3 Aug 2022 08:44:58 +0100 Subject: ARM: 9224/1: Dump the stack traces based on the parameter 'regs' of show_regs() Function show_regs() is usually called in interrupt handler or exception handler, it prints the registers specified by the parameter 'regs', then dump the stack traces. Although not explicitly documented, dump the stack traces based on'regs' seems to make the most sense. Although dump_stack() can finally dump the desired content, because 'regs' are saved by the entry of current interrupt or exception. In the following example we can see: 1) The backtrace of interrupt or exception handler is not expected, it causes confusion. 2) Something is printed repeatedly. The line with the kernel version "CPU: 0 PID: 70 Comm: test0 Not tainted 5.19.0+ #8", the registers saved in "Exception stack" which 'regs' actually point to. For example: rcu: INFO: rcu_sched self-detected stall on CPU rcu: 0-....: (499 ticks this GP) idle=379/1/0x40000002 softirq=91/91 fqs=249 (t=500 jiffies g=-911 q=13 ncpus=4) CPU: 0 PID: 70 Comm: test0 Not tainted 5.19.0+ #8 Hardware name: ARM-Versatile Express PC is at ktime_get+0x4c/0xe8 LR is at ktime_get+0x4c/0xe8 pc : 8019a474 lr : 8019a474 psr: 60000013 sp : cabd1f28 ip : 00000001 fp : 00000005 r10: 527bf1b8 r9 : 431bde82 r8 : d7b634db r7 : 0000156e r6 : 61f234f8 r5 : 00000001 r4 : 80ca86c0 r3 : ffffffff r2 : fe5bce0b r1 : 00000000 r0 : 01a431f4 Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: 6121406a DAC: 00000051 CPU: 0 PID: 70 Comm: test0 Not tainted 5.19.0+ #8 <-----------start---------- Hardware name: ARM-Versatile Express | unwind_backtrace from show_stack+0x10/0x14 | show_stack from dump_stack_lvl+0x40/0x4c | dump_stack_lvl from rcu_dump_cpu_stacks+0x10c/0x134 | rcu_dump_cpu_stacks from rcu_sched_clock_irq+0x780/0xaf4 | rcu_sched_clock_irq from update_process_times+0x54/0x74 | update_process_times from tick_periodic+0x3c/0xd4 | tick_periodic from tick_handle_periodic+0x20/0x80 worthless tick_handle_periodic from twd_handler+0x30/0x40 or twd_handler from handle_percpu_devid_irq+0x8c/0x1c8 duplicated handle_percpu_devid_irq from generic_handle_domain_irq+0x24/0x34 | generic_handle_domain_irq from gic_handle_irq+0x74/0x88 | gic_handle_irq from generic_handle_arch_irq+0x34/0x44 | generic_handle_arch_irq from call_with_stack+0x18/0x20 | call_with_stack from __irq_svc+0x98/0xb0 | Exception stack(0xcabd1ed8 to 0xcabd1f20) | 1ec0: 01a431f4 00000000 | 1ee0: fe5bce0b ffffffff 80ca86c0 00000001 61f234f8 0000156e d7b634db 431bde82 | 1f00: 527bf1b8 00000005 00000001 cabd1f28 8019a474 8019a474 60000013 ffffffff | __irq_svc from ktime_get+0x4c/0xe8 <---------end-------------- ktime_get from test_task+0x44/0x110 test_task from kthread+0xd8/0xf4 kthread from ret_from_fork+0x14/0x2c Exception stack(0xcabd1fb0 to 0xcabd1ff8) 1fa0: 00000000 00000000 00000000 00000000 1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 1fe0: 00000000 00000000 00000000 00000000 00000013 00000000 After replacing dump_stack() with dump_backtrace(): rcu: INFO: rcu_sched self-detected stall on CPU rcu: 0-....: (500 ticks this GP) idle=8f7/1/0x40000002 softirq=129/129 fqs=241 (t=500 jiffies g=-915 q=13 ncpus=4) CPU: 0 PID: 69 Comm: test0 Not tainted 5.19.0+ #9 Hardware name: ARM-Versatile Express PC is at ktime_get+0x4c/0xe8 LR is at ktime_get+0x4c/0xe8 pc : 8019a494 lr : 8019a494 psr: 60000013 sp : cabddf28 ip : 00000001 fp : 00000002 r10: 0779cb48 r9 : 431bde82 r8 : d7b634db r7 : 00000a66 r6 : e835ab70 r5 : 00000001 r4 : 80ca86c0 r3 : ffffffff r2 : ff337d39 r1 : 00000000 r0 : 00cc82c6 Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: 611d006a DAC: 00000051 ktime_get from test_task+0x44/0x110 test_task from kthread+0xd8/0xf4 kthread from ret_from_fork+0x14/0x2c Exception stack(0xcabddfb0 to 0xcabddff8) dfa0: 00000000 00000000 00000000 00000000 dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 dfe0: 00000000 00000000 00000000 00000000 00000013 00000000 Signed-off-by: Zhen Lei Signed-off-by: Russell King (Oracle) --- arch/arm/include/asm/stacktrace.h | 2 ++ arch/arm/kernel/process.c | 2 +- arch/arm/kernel/traps.c | 8 ++++---- 3 files changed, 7 insertions(+), 5 deletions(-) (limited to 'arch') diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h index 3e78f921b8b2..dd19a46f781a 100644 --- a/arch/arm/include/asm/stacktrace.h +++ b/arch/arm/include/asm/stacktrace.h @@ -41,5 +41,7 @@ extern void walk_stackframe(struct stackframe *frame, int (*fn)(struct stackframe *, void *), void *data); extern void dump_mem(const char *lvl, const char *str, unsigned long bottom, unsigned long top); +extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, + const char *loglvl); #endif /* __ASM_STACKTRACE_H */ diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 3d9cace63884..96f3fbd51764 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -201,7 +201,7 @@ void __show_regs(struct pt_regs *regs) void show_regs(struct pt_regs * regs) { __show_regs(regs); - dump_stack(); + dump_backtrace(regs, NULL, KERN_DEFAULT); } ATOMIC_NOTIFIER_HEAD(thread_notify_head); diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index a24d26eaa2cb..20b2db6dcd1c 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -205,14 +205,14 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) } #ifdef CONFIG_ARM_UNWIND -static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, - const char *loglvl) +void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, + const char *loglvl) { unwind_backtrace(regs, tsk, loglvl); } #else -static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, - const char *loglvl) +void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk, + const char *loglvl) { unsigned int fp, mode; int ok = 1; -- cgit v1.2.3-58-ga151