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Message-ID: <ZqzHgFB2t+SWy5o9@shell.armlinux.org.uk>
Date: Fri, 2 Aug 2024 12:48:16 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Jinjie Ruan <ruanjinjie@...wei.com>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
namhyung@...nel.org, mark.rutland@....com,
alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
irogers@...gle.com, adrian.hunter@...el.com,
kan.liang@...ux.intel.com, will@...nel.org, arnd@...db.de,
afd@...com, linus.walleij@...aro.org, akpm@...ux-foundation.org,
masahiroy@...nel.org, eric.devolder@...cle.com,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v2] ARM: stacktrace: Add USER_STACKTRACE support
On Tue, Jul 30, 2024 at 10:15:32AM +0800, Jinjie Ruan wrote:
> Currently, userstacktrace is unsupported for ARM. So use the
> perf_callchain_user() code as blueprint to implement the
> arch_stack_walk_user() which add userstacktrace support on ARM.
> Meanwhile, we can use arch_stack_walk_user() to simplify the implementation
> of perf_callchain_user().
>
> A ftrace test case is shown as below:
> # cd /sys/kernel/debug/tracing
> # echo 1 > options/userstacktrace
> # echo 1 > options/sym-userobj
> # echo 1 > events/sched/sched_process_fork/enable
> # cat trace
>
> ......
> sh-100 [000] ..... 51.779261: sched_process_fork: comm=sh pid=100 child_comm=sh child_pid=108
> sh-100 [000] ..... 51.779285: <user stack trace>
> => /lib/libc.so.6[+0xb3c8c]
> => /bin/busybox[+0xffb901f1]
>
> Also a simple perf test is ok as below:
> # perf record -e cpu-clock --call-graph fp top
> # perf report --call-graph
>
> .....
> [[31m 65.00%[[m 0.00% top [kernel.kallsyms] [k] __ret_fast_syscall
>
> |
> ---__ret_fast_syscall
> |
> |--[[31m30.00%[[m--__se_sys_getdents64
> | iterate_dir
> | |
> | |--[[31m25.00%[[m--proc_pid_readdir
>
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
Do you have a use case for this feature?
Given that userspace is free to do whatever it likes with stack frames,
I think this is going to be hit and miss whether it works.
--
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