Re: [PATCH 1/1] x86/oprofile: Fix the calltrace upon profiling some specified events with oprofile

[wyang1 <Wei.Yang@windriver.com>]

On 08/28/2012 05:17 PM, Robert Richter wrote:
> On 27.08.12 09:32:13, Wei.Yang@windriver.com wrote:
>> From: Wei Yang<Wei.Yang@windriver.com>
>>
>> Upon enabling the call-graph functionality of oprofile, A few minutes
>> later the following calltrace will always occur.
>>
>> BUG: unable to handle kernel paging request at 656d6153
> This is probably the same I found to yesterday. Will test your fix.

OK, I have already tested it on some boards based on intel atom e6xx and 
intel atom n4xx & d5xx.

Thanks
Wei
> -Robert
>
>> IP: [<c10050f5>] print_context_stack+0x55/0x110
>> *pde = 00000000
>> Oops: 0000 [#1] PREEMPT SMP
>> Modules linked in:
>> Pid: 0, comm: swapper/0 Not tainted 3.6.0-rc3-WR5.0+snapshot-20120820_standard
>> EIP: 0060:[<c10050f5>] EFLAGS: 00010093 CPU: 0
>> EIP is at print_context_stack+0x55/0x110
>> EAX: 656d7ffc EBX: 656d6153 ECX: c1837ee0 EDX: 656d6153
>> ESI: 00000000 EDI: ffffe000 EBP: f600deac ESP: f600de88
>> DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
>> CR0: 8005003b CR2: 656d6153 CR3: 01934000 CR4: 000007d0
>> DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
>> DR6: ffff0ff0 DR7: 00000400
>> Process swapper/0 (pid: 0, ti=f600c000 task=c18411a0 task.ti=c1836000)
>> Stack:
>> 1a7f76ea 656d7ffc 656d6000 c1837ee0 ffffe000 c1837ee0 656d6153 c188e27c
>> 656d6000 f600dedc c10040f8 c188e27c f600def0 00000000 f600dec8 c1837ee0
>> 00000000 f600ded4 c1837ee0 f600dfc4 0000001f f600df08 c1564d22 00000000
>> Call Trace:
>> [<c10040f8>] dump_trace+0x68/0xf0
>> [<c1564d22>] x86_backtrace+0xb2/0xc0
>> [<c1562dd2>] oprofile_add_sample+0xa2/0xc0
>> [<c1003fbf>] ? do_softirq+0x6f/0xa0
>> [<c1566519>] ppro_check_ctrs+0x79/0x100
>> [<c15664a0>] ? ppro_shutdown+0x60/0x60
>> [<c156552f>] profile_exceptions_notify+0x8f/0xb0
>> [<c1672248>] nmi_handle.isra.0+0x48/0x70
>> [<c1672343>] do_nmi+0xd3/0x3c0
>> [<c1033d39>] ? __local_bh_enable+0x29/0x70
>> [<c1034620>] ? ftrace_define_fields_irq_handler_entry+0x80/0x80
>> [<c1671a0d>] nmi_stack_correct+0x28/0x2d
>> [<c1034620>] ? ftrace_define_fields_irq_handler_entry+0x80/0x80
>> [<c1003fbf>] ? do_softirq+0x6f/0xa0
>> <IRQ>
>> [<c1034ad5>] irq_exit+0x65/0x70
>> [<c16776f9>] smp_apic_timer_interrupt+0x59/0x89
>> [<c16717da>] apic_timer_interrupt+0x2a/0x30
>> [<c135164d>] ? acpi_idle_enter_bm+0x245/0x273
>> [<c14f3a25>] cpuidle_enter+0x15/0x20
>> [<c14f4070>] cpuidle_idle_call+0xa0/0x320
>> [<c1009705>] cpu_idle+0x55/0xb0
>> [<c16519a8>] rest_init+0x6c/0x74
>> [<c18a291b>] start_kernel+0x2ec/0x2f3
>> [<c18a2467>] ? repair_env_string+0x51/0x51
>> [<c18a22a2>] i386_start_kernel+0x78/0x7d
>> Code: e0 ff ff 89 7d ec 74 5a 8d b4 26 00 00 00 00 8d bc 27 00 00
>> 00 00 39 f3 72 0c 8b 45 f0 8d 64 24 18 5b 5e 5f 5d c3 3b 5d ec 72
>> ef<8b>  3b 89 f8 89 7d dc e8 ef 40 04 00 85 c0 74 20 8b 40
>> EIP: [<c10050f5>] print_context_stack+0x55/0x110 SS:ESP 0068:f600de88
>> CR2: 00000000656d6153
>> ---[ end trace 751c9b47c6ff5e29 ]---
>>
>> Let's assume a scenario that do_softirq() switches the stack to a soft irq
>> stack, and the soft irq stack is totally empty. At this moment, a nmi interrupt
>> occurs, subsequently, CPU does not automatically save SS and SP registers
>> and switch any stack, but instead only stores EFLAGS, CS and IP to the soft irq
>> stack. since the CPU is in kernel mode when the NMI exception occurs.
>> the layout of the current soft irq stack is this:
>>
>>    +--------------+<-----the top of soft irq
>>    |   EFLAGS     |
>>    +--------------+
>>    |    CS        |
>>    +--------------+
>>    |    IP        |
>>    +--------------+
>>    |   SAVE_ALL   |
>>    +--------------+
>>
>> but the return value of the function kernel_stack_pointer() is'&regs->sp'
>> (for x86_32 CPU), which is invoked by the x86_backtrace function. Since
>> the type of regs pointer is a pt_regs structure, the return value is not
>> in the range of the soft irq stack, as the SP register is not save in the
>> soft irq stack. Therefore, we need to check if the return value of the function
>> resides in valid range. Additionally, the changes has no impact on the normal
>> NMI exception.
>>
>> Signed-off-by: Yang Wei<wei.yang@windriver.com>
>> ---
>>   arch/x86/oprofile/backtrace.c |   10 ++++++++++
>>   1 files changed, 10 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/x86/oprofile/backtrace.c b/arch/x86/oprofile/backtrace.c
>> index d6aa6e8..a5fca0b 100644
>> --- a/arch/x86/oprofile/backtrace.c
>> +++ b/arch/x86/oprofile/backtrace.c
>> @@ -17,6 +17,11 @@
>>   #include<asm/ptrace.h>
>>   #include<asm/stacktrace.h>
>>
>> +static inline int valid_stack_ptr(struct thread_info *tinfo, void *p)
>> +{
>> +	void *t = tinfo;
>> +	return p>  t + sizeof(struct thread_info)&&  p<  t + THREAD_SIZE;
>> +}
>>   static int backtrace_stack(void *data, char *name)
>>   {
>>   	/* Yes, we want all stacks */
>> @@ -110,9 +115,14 @@ void
>>   x86_backtrace(struct pt_regs * const regs, unsigned int depth)
>>   {
>>   	struct stack_frame *head = (struct stack_frame *)frame_pointer(regs);
>> +	struct thread_info *context;
>>
>>   	if (!user_mode_vm(regs)) {
>>   		unsigned long stack = kernel_stack_pointer(regs);
>> +		context = (struct thread_info *)
>> +			(stack&  (~(THREAD_SIZE - 1)));
>> +		if (!valid_stack_ptr(context, (void *)stack))
>> +			return;
>>   		if (depth)
>>   			dump_trace(NULL, regs, (unsigned long *)stack, 0,
>>   				&backtrace_ops,&depth);
>> -- 
>> 1.7.0.2
>>
>>