Messages in this thread | | | Subject | Re: [PATCH v2] tracing: Function stack size and its name mismatch in arm64 | From | Jiping Ma <> | Date | Fri, 2 Aug 2019 10:43:03 +0800 |
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On 2019年08月01日 17:41, Will Deacon wrote: > On Thu, Aug 01, 2019 at 04:33:40PM +0800, Jiping Ma wrote: >> In arm64, the PC of the frame is matched to the last frame function, >> rather than the function of his frame. For the following example, the >> stack size of occupy_stack_init function should be 3376, rather than 176. >> >> Wrong info: >> Depth Size Location (16 entries) >> ----- ---- -------- >> 0) 5400 16 __update_load_avg_se.isra.2+0x28/0x220 >> 1) 5384 96 put_prev_entity+0x250/0x338 >> 2) 5288 80 pick_next_task_fair+0x4c4/0x508 >> 3) 5208 72 __schedule+0x100/0x600 >> 4) 5136 184 preempt_schedule_common+0x28/0x48 >> 5) 4952 32 preempt_schedule+0x28/0x30 >> 6) 4920 16 vprintk_emit+0x170/0x1f8 >> 7) 4904 128 vprintk_default+0x48/0x58 >> 8) 4776 64 vprintk_func+0xf8/0x1c8 >> 9) 4712 112 printk+0x70/0x90 >> 10) 4600 176 occupy_stack_init+0x64/0xc0 [kernel_stack] >> 11) 4424 3376 do_one_initcall+0x68/0x248 >> 12) 1048 144 do_init_module+0x60/0x1f0 >> 13) 904 48 load_module+0x1d50/0x2340 >> 14) 856 352 sys_finit_module+0xd0/0xe8 >> 15) 504 504 el0_svc_naked+0x30/0x34 >> >> Correct info: >> Depth Size Location (18 entries) >> ----- ---- -------- >> 0) 5464 48 cgroup_rstat_updated+0x20/0x100 >> 1) 5416 32 cgroup_base_stat_cputime_account_end.isra.0+0x30/0x60 >> 2) 5384 32 __cgroup_account_cputime+0x3c/0x48 >> 3) 5352 64 update_curr+0xc4/0x1d0 >> 4) 5288 72 pick_next_task_fair+0x444/0x508 >> 5) 5216 184 __schedule+0x100/0x600 >> 6) 5032 32 preempt_schedule_common+0x28/0x48 >> 7) 5000 16 preempt_schedule+0x28/0x30 >> 8) 4984 128 vprintk_emit+0x170/0x1f8 >> 9) 4856 64 vprintk_default+0x48/0x58 >> 10) 4792 112 vprintk_func+0xf8/0x1c8 >> 11) 4680 176 printk+0x70/0x90 >> 12) 4504 80 func_test+0x7c/0xb8 [kernel_stack] >> 13) 4424 3376 occupy_stack_init+0x7c/0xc0 [kernel_stack] >> 14) 1048 144 do_one_initcall+0x68/0x248 >> 15) 904 48 do_init_module+0x60/0x1f0 >> 16) 856 352 load_module+0x1d50/0x2340 >> 17) 504 504 sys_finit_module+0xd0/0xe8 >> >> Signed-off-by: Jiping Ma <jiping.ma2@windriver.com> >> --- >> kernel/trace/trace_stack.c | 28 ++++++++++++++++++++++++++-- >> 1 file changed, 26 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c >> index 5d16f73898db..ed80b95abf06 100644 >> --- a/kernel/trace/trace_stack.c >> +++ b/kernel/trace/trace_stack.c >> @@ -40,16 +40,28 @@ static void print_max_stack(void) >> >> pr_emerg(" Depth Size Location (%d entries)\n" >> " ----- ---- --------\n", >> +#ifdef CONFIG_ARM64 >> + stack_trace_nr_entries - 1); >> +#else >> stack_trace_nr_entries); > Sorry, but I have no idea what the problem is here. All I know is that the > solution looks highly dubious and I find it very hard to believe that the > arm64 backtracing code is uniquely special as to deserve being called out > like this. I suspect there's a bug lurking somewhere, but you really need > to do a better job of explaining the issue rather than simply providing a > couple of backtraces with no context. > > *Why* does the frame appear to be off-by-one? Because the PC is LR in ARM64 stack actually. Following is ARM64 stack layout. Please refer to the figure 3 in http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055b/IHI0055B_aapcs64.pdf LR FP ...... LR FP Jiping > > Will
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