| Message ID | A601CC3C-4B09-4D8B-8564-558349D45815@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Jul 16, 2015, at 10:29 PM, Jungseok Lee wrote: > On Jul 16, 2015, at 10:08 AM, AKASHI Takahiro wrote: > > Hi, AKASHI > >> On 07/16/2015 09:27 AM, AKASHI Takahiro wrote: >>> On 07/16/2015 01:13 AM, Steven Rostedt wrote: >>>> On Wed, 15 Jul 2015 10:55:36 -0400 >>>> Steven Rostedt <rostedt@goodmis.org> wrote: >>>> >>>> >>>>> I'll take a look at it and try to clean up the code. >>>> >>>> Does the following patch make sense for you? >>> >>> Looks nice. The patch greatly simplifies changes on arm64 side. >> >> As follows: >> >> - Takahiro AKASHI >> >> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h >> index c5534fa..868d6f1 100644 >> --- a/arch/arm64/include/asm/ftrace.h >> +++ b/arch/arm64/include/asm/ftrace.h >> @@ -15,6 +15,7 @@ >> >> #define MCOUNT_ADDR ((unsigned long)_mcount) >> #define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE >> +#define FTRACE_STACK_FRAME_OFFSET 4 /* sync it up with stacktrace.c */ > > How about binding it to -4 in unwind_frame function? > IMHO, it would help other developers trying to change stack trace code > be aware of this stack tracer feature. > >> #ifndef __ASSEMBLY__ >> #include <linux/compat.h> >> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h >> index 1da6029..2c1bf7d 100644 >> --- a/include/linux/ftrace.h >> +++ b/include/linux/ftrace.h >> @@ -260,6 +260,13 @@ static inline void ftrace_kill(void) { } >> #endif /* CONFIG_FUNCTION_TRACER */ >> >> #ifdef CONFIG_STACK_TRACER >> +/* >> + * the offset value to add to return address from save_stack_trace() >> + */ >> +#ifndef FTRACE_STACK_FRAME_OFFSET >> +#define FTRACE_STACK_FRAME_OFFSET 0 >> +#endif >> + >> extern int stack_tracer_enabled; >> int >> stack_trace_sysctl(struct ctl_table *table, int write, >> diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c >> index 9384647..c5b9748 100644 >> --- a/kernel/trace/trace_stack.c >> +++ b/kernel/trace/trace_stack.c >> @@ -105,7 +105,7 @@ check_stack(unsigned long ip, unsigned long *stack) >> >> /* Skip over the overhead of the stack tracer itself */ >> for (i = 0; i < max_stack_trace.nr_entries; i++) { >> - if (stack_dump_trace[i] == ip) >> + if ((stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET) == ip) >> break; >> } >> >> @@ -131,7 +131,8 @@ check_stack(unsigned long ip, unsigned long *stack) >> p = start; >> >> for (; p < top && i < max_stack_trace.nr_entries; p++) { >> - if (*p == stack_dump_trace[i]) { >> + if (*p == (stack_dump_trace[i] >> + + FTRACE_STACK_FRAME_OFFSET)) { >> stack_dump_trace[x] = stack_dump_trace[i++]; >> this_size = stack_dump_index[x++] = >> (top - p) * sizeof(unsigned long); >> -- > > I've prepared a kernel with the following patches and reviewed them. > > 1) Steve's clean up patch > 2) This patch > 3) [RFC 2/3] > > AFAIU, [RFC 3/3] is not needed any more thanks to Steve's patch. > > First of all, let's look at the following data. > > 1) stack_trace data > Depth Size Location (55 entries) > ----- ---- -------- > 0) 4808 16 notifier_call_chain+0x2c/0x94 > 1) 4792 64 raw_notifier_call_chain+0x34/0x44 > 2) 4728 48 timekeeping_update.constprop.9+0xb8/0x114 > 3) 4680 48 update_wall_time+0x408/0x6dc > 4) 4632 128 tick_do_update_jiffies64+0xd8/0x154 > 5) 4504 80 tick_sched_do_timer+0x50/0x60 > 6) 4424 32 tick_sched_timer+0x34/0x90 > 7) 4392 48 __run_hrtimer+0x60/0x258 > 8) 4344 64 hrtimer_interrupt+0xe8/0x260 > 9) 4280 128 arch_timer_handler_virt+0x38/0x48 > 10) 4152 32 handle_percpu_devid_irq+0x84/0x188 > 11) 4120 64 generic_handle_irq+0x38/0x54 > 12) 4056 32 __handle_domain_irq+0x68/0xbc > 13) 4024 64 gic_handle_irq+0x38/0x88 > 14) 3960 336 el1_irq+0x64/0xd8 > 15) 3624 16 netif_rx_internal+0x14/0x198 > 16) 3608 64 netif_rx+0x20/0xa4 > 17) 3544 32 loopback_xmit+0x64/0xf4 > 18) 3512 48 dev_hard_start_xmit+0x25c/0x3f8 > 19) 3464 160 __dev_queue_xmit+0x440/0x4dc > 20) 3304 96 dev_queue_xmit_sk+0x20/0x30 > 21) 3208 32 ip_finish_output+0x1e0/0xabc > 22) 3176 96 ip_output+0xf0/0x120 > 23) 3080 64 ip_local_out_sk+0x44/0x54 > 24) 3016 32 ip_send_skb+0x24/0xbc > 25) 2984 48 ip_push_pending_frames+0x40/0x60 > 26) 2936 64 icmp_push_reply+0x104/0x144 > 27) 2872 96 icmp_send+0x3c0/0x3c8 > 28) 2776 192 __udp4_lib_rcv+0x5b8/0x684 > 29) 2584 96 udp_rcv+0x2c/0x3c > 30) 2488 32 ip_local_deliver+0xa0/0x224 > 31) 2456 48 ip_rcv+0x360/0x57c > 32) 2408 64 __netif_receive_skb_core+0x4d0/0x80c > 33) 2344 128 __netif_receive_skb+0x24/0x84 > 34) 2216 32 process_backlog+0x9c/0x15c > 35) 2184 80 net_rx_action+0x1ec/0x32c > 36) 2104 160 __do_softirq+0x114/0x2f0 > 37) 1944 128 do_softirq+0x60/0x68 > 38) 1816 32 __local_bh_enable_ip+0xb0/0xd4 > 39) 1784 32 ip_finish_output+0x1f4/0xabc > 40) 1752 96 ip_output+0xf0/0x120 > 41) 1656 64 ip_local_out_sk+0x44/0x54 > 42) 1592 32 ip_send_skb+0x24/0xbc > 43) 1560 48 udp_send_skb+0x1b4/0x2f4 > 44) 1512 80 udp_sendmsg+0x2a8/0x7a0 > 45) 1432 272 inet_sendmsg+0xa0/0xd0 > 46) 1160 48 sock_sendmsg+0x30/0x78 > 47) 1112 32 ___sys_sendmsg+0x15c/0x26c > 48) 1080 400 __sys_sendmmsg+0x94/0x180 > 49) 680 320 SyS_sendmmsg+0x38/0x54 > 50) 360 360 el0_svc_naked+0x20/0x28 > > 2) stack_max_size data > 4888 > > The data looks odd in two points. > 1) the number of entry > There is a mismatch between start token and real data > > 2) 80-byte gap > stack_max_size is not aligned with "Depth" field of the first entry of stack_trace. > > IMHO, two items are not considered in this series as digging them out. > > 1) skipped entries > As x variable is introduced in Steve's patch, it is needed to track down > how many entries are recorded in both stack_dump_trace and stack_dump_index. > > 2) max_stack_trace.skip value > max_stack_trace.skip is 0 as applying Steve's patch. The above gap could be > observed unless the value is not considered in arch code. In the above example, > 80-byte gap is save_stack_trace function in arch/arm64/kernel/stacktrace.c. > > As applying the following fix, stack_trace and stack_max_size are okay. > However, I'm not sure which code, arch or generic ftrace, should handle trace->skip. > The latter one is responsible for it under current implementation, not Steve's change. > > Please correct me if I am wrong. > > Best Regards > Jungseok Lee > > ----8<---- > > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index 978c923..5f6f4df 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -137,7 +137,9 @@ void save_stack_trace(struct stack_trace *trace) > > frame.fp = (unsigned long)__builtin_frame_address(0); > frame.sp = current_stack_pointer; > - frame.pc = (unsigned long)save_stack_trace_tsk; > + frame.pc = (unsigned long)save_stack_trace; > + > + trace->skip += 4; > > __save_stack_trace(&frame, trace, 0); > } > diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c > index c5b9748..5635683 100644 > --- a/kernel/trace/trace_stack.c > +++ b/kernel/trace/trace_stack.c > @@ -158,6 +158,9 @@ check_stack(unsigned long ip, unsigned long *stack) > i++; > } > > + /* We do not want to include skipped entries */ > + max_stack_trace.nr_entries -= (i - x); > + > for (; x < max_stack_trace.nr_entries; x++) This line should be changed as follows. for (; x < i; x++) Sorry for confusion. Best Regards Jungseok Lee
Jungseok, Thank you for your testing and reviews. On 07/16/2015 10:29 PM, Jungseok Lee wrote: > On Jul 16, 2015, at 10:08 AM, AKASHI Takahiro wrote: > > Hi, AKASHI > >> On 07/16/2015 09:27 AM, AKASHI Takahiro wrote: >>> On 07/16/2015 01:13 AM, Steven Rostedt wrote: >>>> On Wed, 15 Jul 2015 10:55:36 -0400 >>>> Steven Rostedt <rostedt@goodmis.org> wrote: >>>> >>>> >>>>> I'll take a look at it and try to clean up the code. >>>> >>>> Does the following patch make sense for you? >>> >>> Looks nice. The patch greatly simplifies changes on arm64 side. >> >> As follows: >> >> - Takahiro AKASHI >> >> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h >> index c5534fa..868d6f1 100644 >> --- a/arch/arm64/include/asm/ftrace.h >> +++ b/arch/arm64/include/asm/ftrace.h >> @@ -15,6 +15,7 @@ >> >> #define MCOUNT_ADDR ((unsigned long)_mcount) >> #define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE >> +#define FTRACE_STACK_FRAME_OFFSET 4 /* sync it up with stacktrace.c */ Well, #define FTRACE_STACK_FRAME_OFFSET AARCH64_INSN_SIZE might be better. > How about binding it to -4 in unwind_frame function? Do you mean like this? In unwind_frame(), frame->pc = *(unsigned long*)(fp + 8) - AARCH64_INSN_SIZE; > IMHO, it would help other developers trying to change stack trace code > be aware of this stack tracer feature. > >> #ifndef __ASSEMBLY__ >> #include <linux/compat.h> >> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h >> index 1da6029..2c1bf7d 100644 >> --- a/include/linux/ftrace.h >> +++ b/include/linux/ftrace.h >> @@ -260,6 +260,13 @@ static inline void ftrace_kill(void) { } >> #endif /* CONFIG_FUNCTION_TRACER */ >> >> #ifdef CONFIG_STACK_TRACER >> +/* >> + * the offset value to add to return address from save_stack_trace() >> + */ >> +#ifndef FTRACE_STACK_FRAME_OFFSET >> +#define FTRACE_STACK_FRAME_OFFSET 0 >> +#endif >> + >> extern int stack_tracer_enabled; >> int >> stack_trace_sysctl(struct ctl_table *table, int write, >> diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c >> index 9384647..c5b9748 100644 >> --- a/kernel/trace/trace_stack.c >> +++ b/kernel/trace/trace_stack.c >> @@ -105,7 +105,7 @@ check_stack(unsigned long ip, unsigned long *stack) >> >> /* Skip over the overhead of the stack tracer itself */ >> for (i = 0; i < max_stack_trace.nr_entries; i++) { >> - if (stack_dump_trace[i] == ip) >> + if ((stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET) == ip) >> break; >> } >> >> @@ -131,7 +131,8 @@ check_stack(unsigned long ip, unsigned long *stack) >> p = start; >> >> for (; p < top && i < max_stack_trace.nr_entries; p++) { >> - if (*p == stack_dump_trace[i]) { >> + if (*p == (stack_dump_trace[i] >> + + FTRACE_STACK_FRAME_OFFSET)) { >> stack_dump_trace[x] = stack_dump_trace[i++]; >> this_size = stack_dump_index[x++] = >> (top - p) * sizeof(unsigned long); >> -- > > I've prepared a kernel with the following patches and reviewed them. > > 1) Steve's clean up patch > 2) This patch > 3) [RFC 2/3] > > AFAIU, [RFC 3/3] is not needed any more thanks to Steve's patch. We don't need [2/3]. > First of all, let's look at the following data. > > 1) stack_trace data > Depth Size Location (55 entries) > ----- ---- -------- > 0) 4808 16 notifier_call_chain+0x2c/0x94 > 1) 4792 64 raw_notifier_call_chain+0x34/0x44 > 2) 4728 48 timekeeping_update.constprop.9+0xb8/0x114 > 3) 4680 48 update_wall_time+0x408/0x6dc > 4) 4632 128 tick_do_update_jiffies64+0xd8/0x154 > 5) 4504 80 tick_sched_do_timer+0x50/0x60 > 6) 4424 32 tick_sched_timer+0x34/0x90 > 7) 4392 48 __run_hrtimer+0x60/0x258 > 8) 4344 64 hrtimer_interrupt+0xe8/0x260 > 9) 4280 128 arch_timer_handler_virt+0x38/0x48 > 10) 4152 32 handle_percpu_devid_irq+0x84/0x188 > 11) 4120 64 generic_handle_irq+0x38/0x54 > 12) 4056 32 __handle_domain_irq+0x68/0xbc > 13) 4024 64 gic_handle_irq+0x38/0x88 > 14) 3960 336 el1_irq+0x64/0xd8 > 15) 3624 16 netif_rx_internal+0x14/0x198 > 16) 3608 64 netif_rx+0x20/0xa4 > 17) 3544 32 loopback_xmit+0x64/0xf4 > 18) 3512 48 dev_hard_start_xmit+0x25c/0x3f8 > 19) 3464 160 __dev_queue_xmit+0x440/0x4dc > 20) 3304 96 dev_queue_xmit_sk+0x20/0x30 > 21) 3208 32 ip_finish_output+0x1e0/0xabc > 22) 3176 96 ip_output+0xf0/0x120 > 23) 3080 64 ip_local_out_sk+0x44/0x54 > 24) 3016 32 ip_send_skb+0x24/0xbc > 25) 2984 48 ip_push_pending_frames+0x40/0x60 > 26) 2936 64 icmp_push_reply+0x104/0x144 > 27) 2872 96 icmp_send+0x3c0/0x3c8 > 28) 2776 192 __udp4_lib_rcv+0x5b8/0x684 > 29) 2584 96 udp_rcv+0x2c/0x3c > 30) 2488 32 ip_local_deliver+0xa0/0x224 > 31) 2456 48 ip_rcv+0x360/0x57c > 32) 2408 64 __netif_receive_skb_core+0x4d0/0x80c > 33) 2344 128 __netif_receive_skb+0x24/0x84 > 34) 2216 32 process_backlog+0x9c/0x15c > 35) 2184 80 net_rx_action+0x1ec/0x32c > 36) 2104 160 __do_softirq+0x114/0x2f0 > 37) 1944 128 do_softirq+0x60/0x68 > 38) 1816 32 __local_bh_enable_ip+0xb0/0xd4 > 39) 1784 32 ip_finish_output+0x1f4/0xabc > 40) 1752 96 ip_output+0xf0/0x120 > 41) 1656 64 ip_local_out_sk+0x44/0x54 > 42) 1592 32 ip_send_skb+0x24/0xbc > 43) 1560 48 udp_send_skb+0x1b4/0x2f4 > 44) 1512 80 udp_sendmsg+0x2a8/0x7a0 > 45) 1432 272 inet_sendmsg+0xa0/0xd0 > 46) 1160 48 sock_sendmsg+0x30/0x78 > 47) 1112 32 ___sys_sendmsg+0x15c/0x26c > 48) 1080 400 __sys_sendmmsg+0x94/0x180 > 49) 680 320 SyS_sendmmsg+0x38/0x54 > 50) 360 360 el0_svc_naked+0x20/0x28 > > 2) stack_max_size data > 4888 > > The data looks odd in two points. > 1) the number of entry > There is a mismatch between start token and real data > > 2) 80-byte gap > stack_max_size is not aligned with "Depth" field of the first entry of stack_trace. > > IMHO, two items are not considered in this series as digging them out. > > 1) skipped entries > As x variable is introduced in Steve's patch, it is needed to track down > how many entries are recorded in both stack_dump_trace and stack_dump_index. > > 2) max_stack_trace.skip value > max_stack_trace.skip is 0 as applying Steve's patch. The above gap could be > observed unless the value is not considered in arch code. In the above example, > 80-byte gap is save_stack_trace function in arch/arm64/kernel/stacktrace.c. > > As applying the following fix, stack_trace and stack_max_size are okay. > However, I'm not sure which code, arch or generic ftrace, should handle trace->skip. > The latter one is responsible for it under current implementation, not Steve's change. > > Please correct me if I am wrong. I will address these issues in my later replies. Thanks, -Takahiro AKASHI > Best Regards > Jungseok Lee > > ----8<---- > > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c > index 978c923..5f6f4df 100644 > --- a/arch/arm64/kernel/stacktrace.c > +++ b/arch/arm64/kernel/stacktrace.c > @@ -137,7 +137,9 @@ void save_stack_trace(struct stack_trace *trace) > > frame.fp = (unsigned long)__builtin_frame_address(0); > frame.sp = current_stack_pointer; > - frame.pc = (unsigned long)save_stack_trace_tsk; > + frame.pc = (unsigned long)save_stack_trace; > + > + trace->skip += 4; > > __save_stack_trace(&frame, trace, 0); > } > diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c > index c5b9748..5635683 100644 > --- a/kernel/trace/trace_stack.c > +++ b/kernel/trace/trace_stack.c > @@ -158,6 +158,9 @@ check_stack(unsigned long ip, unsigned long *stack) > i++; > } > > + /* We do not want to include skipped entries */ > + max_stack_trace.nr_entries -= (i - x); > + > for (; x < max_stack_trace.nr_entries; x++) > stack_dump_trace[x] = ULONG_MAX; > > @@ -330,7 +333,7 @@ static int t_show(struct seq_file *m, void *v) > seq_printf(m, " Depth Size Location" > " (%d entries)\n" > " ----- ---- --------\n", > - max_stack_trace.nr_entries - 1); > + max_stack_trace.nr_entries); > > if (!stack_tracer_enabled && !max_stack_size) > print_disabled(m); > > ----8<---- > > 1) stack_trace data > Depth Size Location (47 entries) > ----- ---- -------- > 0) 4648 16 notifier_call_chain+0x2c/0x94 > 1) 4632 64 raw_notifier_call_chain+0x34/0x44 > 2) 4568 48 timekeeping_update.constprop.9+0xb8/0x114 > 3) 4520 48 update_wall_time+0x408/0x6dc > 4) 4472 128 tick_do_update_jiffies64+0xd8/0x154 > 5) 4344 80 tick_sched_do_timer+0x50/0x60 > 6) 4264 32 tick_sched_timer+0x34/0x90 > 7) 4232 48 __run_hrtimer+0x60/0x258 > 8) 4184 64 hrtimer_interrupt+0xe8/0x260 > 9) 4120 128 arch_timer_handler_virt+0x38/0x48 > 10) 3992 32 handle_percpu_devid_irq+0x84/0x188 > 11) 3960 64 generic_handle_irq+0x38/0x54 > 12) 3896 32 __handle_domain_irq+0x68/0xbc > 13) 3864 64 gic_handle_irq+0x38/0x88 > 14) 3800 336 el1_irq+0x64/0xd8 > 15) 3464 48 __kmalloc_track_caller+0x40/0x2f8 > 16) 3416 16 __kmalloc_reserve.isra.46+0x44/0x9c > 17) 3400 144 __alloc_skb+0x70/0x180 > 18) 3256 96 alloc_skb_with_frags+0x74/0x234 > 19) 3160 112 sock_alloc_send_pskb+0x1d0/0x294 > 20) 3048 160 sock_alloc_send_skb+0x44/0x54 > 21) 2888 64 __ip_append_data.isra.40+0x78c/0xb48 > 22) 2824 224 ip_append_data.part.42+0x98/0xe8 > 23) 2600 112 ip_append_data+0x68/0x7c > 24) 2488 96 icmp_push_reply+0x7c/0x144 > 25) 2392 96 icmp_send+0x3c0/0x3c8 > 26) 2296 192 __udp4_lib_rcv+0x5b8/0x684 > 27) 2104 96 udp_rcv+0x2c/0x3c > 28) 2008 32 ip_local_deliver+0xa0/0x224 > 29) 1976 48 ip_rcv+0x360/0x57c > 30) 1928 64 __netif_receive_skb_core+0x4d0/0x80c > 31) 1864 128 __netif_receive_skb+0x24/0x84 > 32) 1736 32 process_backlog+0x9c/0x15c > 33) 1704 80 net_rx_action+0x1ec/0x32c > 34) 1624 160 __do_softirq+0x114/0x2f0 > 35) 1464 128 do_softirq+0x60/0x68 > 36) 1336 32 __local_bh_enable_ip+0xb0/0xd4 > 37) 1304 32 ip_finish_output+0x1f4/0xabc > 38) 1272 96 ip_output+0xf0/0x120 > 39) 1176 64 ip_local_out_sk+0x44/0x54 > 40) 1112 32 ip_send_skb+0x24/0xbc > 41) 1080 48 udp_send_skb+0x1b4/0x2f4 > 42) 1032 80 udp_sendmsg+0x2a8/0x7a0 > 43) 952 272 inet_sendmsg+0xa0/0xd0 > 44) 680 48 sock_sendmsg+0x30/0x78 > 45) 632 32 SyS_sendto+0xc4/0x108 > 46) 600 600 el0_svc_naked+0x20/0x28 > > 2) stack_max_size data > 4648 >
On Jul 17, 2015, at 11:04 AM, AKASHI Takahiro wrote: > Jungseok, > > Thank you for your testing and reviews. You're welcome. > On 07/16/2015 10:29 PM, Jungseok Lee wrote: >> On Jul 16, 2015, at 10:08 AM, AKASHI Takahiro wrote: >> >> Hi, AKASHI >> >>> On 07/16/2015 09:27 AM, AKASHI Takahiro wrote: >>>> On 07/16/2015 01:13 AM, Steven Rostedt wrote: >>>>> On Wed, 15 Jul 2015 10:55:36 -0400 >>>>> Steven Rostedt <rostedt@goodmis.org> wrote: >>>>> >>>>> >>>>>> I'll take a look at it and try to clean up the code. >>>>> >>>>> Does the following patch make sense for you? >>>> >>>> Looks nice. The patch greatly simplifies changes on arm64 side. >>> >>> As follows: >>> >>> - Takahiro AKASHI >>> >>> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h >>> index c5534fa..868d6f1 100644 >>> --- a/arch/arm64/include/asm/ftrace.h >>> +++ b/arch/arm64/include/asm/ftrace.h >>> @@ -15,6 +15,7 @@ >>> >>> #define MCOUNT_ADDR ((unsigned long)_mcount) >>> #define MCOUNT_INSN_SIZE AARCH64_INSN_SIZE >>> +#define FTRACE_STACK_FRAME_OFFSET 4 /* sync it up with stacktrace.c */ > > Well, > #define FTRACE_STACK_FRAME_OFFSET AARCH64_INSN_SIZE > might be better. Agree. > >> How about binding it to -4 in unwind_frame function? > > Do you mean like this? > In unwind_frame(), > frame->pc = *(unsigned long*)(fp + 8) - AARCH64_INSN_SIZE; Exactly. > >> IMHO, it would help other developers trying to change stack trace code >> be aware of this stack tracer feature. >> >>> #ifndef __ASSEMBLY__ >>> #include <linux/compat.h> >>> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h >>> index 1da6029..2c1bf7d 100644 >>> --- a/include/linux/ftrace.h >>> +++ b/include/linux/ftrace.h >>> @@ -260,6 +260,13 @@ static inline void ftrace_kill(void) { } >>> #endif /* CONFIG_FUNCTION_TRACER */ >>> >>> #ifdef CONFIG_STACK_TRACER >>> +/* >>> + * the offset value to add to return address from save_stack_trace() >>> + */ >>> +#ifndef FTRACE_STACK_FRAME_OFFSET >>> +#define FTRACE_STACK_FRAME_OFFSET 0 >>> +#endif >>> + >>> extern int stack_tracer_enabled; >>> int >>> stack_trace_sysctl(struct ctl_table *table, int write, >>> diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c >>> index 9384647..c5b9748 100644 >>> --- a/kernel/trace/trace_stack.c >>> +++ b/kernel/trace/trace_stack.c >>> @@ -105,7 +105,7 @@ check_stack(unsigned long ip, unsigned long *stack) >>> >>> /* Skip over the overhead of the stack tracer itself */ >>> for (i = 0; i < max_stack_trace.nr_entries; i++) { >>> - if (stack_dump_trace[i] == ip) >>> + if ((stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET) == ip) >>> break; >>> } >>> >>> @@ -131,7 +131,8 @@ check_stack(unsigned long ip, unsigned long *stack) >>> p = start; >>> >>> for (; p < top && i < max_stack_trace.nr_entries; p++) { >>> - if (*p == stack_dump_trace[i]) { >>> + if (*p == (stack_dump_trace[i] >>> + + FTRACE_STACK_FRAME_OFFSET)) { >>> stack_dump_trace[x] = stack_dump_trace[i++]; >>> this_size = stack_dump_index[x++] = >>> (top - p) * sizeof(unsigned long); >>> -- >> >> I've prepared a kernel with the following patches and reviewed them. >> >> 1) Steve's clean up patch >> 2) This patch >> 3) [RFC 2/3] >> >> AFAIU, [RFC 3/3] is not needed any more thanks to Steve's patch. > > We don't need [2/3]. Okay. So, I've played a kernel including Steve's latest patch and only [1/3]. Best Regards Jungseok Lee
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 978c923..5f6f4df 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -137,7 +137,9 @@ void save_stack_trace(struct stack_trace *trace) frame.fp = (unsigned long)__builtin_frame_address(0); frame.sp = current_stack_pointer; - frame.pc = (unsigned long)save_stack_trace_tsk; + frame.pc = (unsigned long)save_stack_trace; + + trace->skip += 4; __save_stack_trace(&frame, trace, 0); } diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index c5b9748..5635683 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -158,6 +158,9 @@ check_stack(unsigned long ip, unsigned long *stack) i++; } + /* We do not want to include skipped entries */ + max_stack_trace.nr_entries -= (i - x); + for (; x < max_stack_trace.nr_entries; x++) stack_dump_trace[x] = ULONG_MAX; @@ -330,7 +333,7 @@ static int t_show(struct seq_file *m, void *v) seq_printf(m, " Depth Size Location" " (%d entries)\n" " ----- ---- --------\n", - max_stack_trace.nr_entries - 1); + max_stack_trace.nr_entries); if (!stack_tracer_enabled && !max_stack_size) print_disabled(m);