From: Gyokhan Kochmarla <gyokhan@amazon•de>
To: <stable@vger•kernel.org>, <gregkh@linuxfoundation•org>
Cc: <yangfeng@kylinos•cn>, <rostedt@goodmis•org>,
<mhiramat@kernel•org>, <mark.rutland@arm•com>,
<catalin.marinas@arm•com>, <will@kernel•org>, <jolsa@kernel•org>,
<linux-trace-kernel@vger•kernel.org>,
<linux-arm-kernel@lists•infradead.org>, <bpf@vger•kernel.org>,
"Gyokhan Kochmarla" <gyokhan@amazon•de>
Subject: [PATCH 6.12] tracing: Fix the bug where bpf_get_stackid returns -EFAULT on the ARM64
Date: Tue, 26 May 2026 19:20:12 +0000 [thread overview]
Message-ID: <20260526192012.76223-1-gyokhan@amazon.de> (raw)
From: Feng Yang <yangfeng@kylinos•cn>
commit fd2f74f8f3d3c1a524637caf5bead9757fae4332 upstream.
When using bpf_program__attach_kprobe_multi_opts on ARM64 to hook a BPF program
that contains the bpf_get_stackid function, the BPF program fails
to obtain the stack trace and returns -EFAULT.
This is because ftrace_partial_regs omits the configuration of the pstate register,
leaving pstate at the default value of 0. When get_perf_callchain executes,
it uses user_mode(regs) to determine whether it is in kernel mode.
This leads to a misjudgment that the code is in user mode,
so perf_callchain_kernel is not executed and the function returns directly.
As a result, trace->nr becomes 0, and finally -EFAULT is returned.
Therefore, the assignment of the pstate register is added here.
Fixes: b9b55c8912ce ("tracing: Add ftrace_partial_regs() for converting ftrace_regs to pt_regs")
Closes: https://lore.kernel.org/bpf/20250919071902.554223-1-yangfeng59949@163.com/
Signed-off-by: Feng Yang <yangfeng@kylinos•cn>
Tested-by: Jiri Olsa <jolsa@kernel•org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel•org>
Signed-off-by: Will Deacon <will@kernel•org>
Signed-off-by: Gyokhan Kochmarla <gyokhan@amazon•de>
---
arch/arm64/include/asm/ftrace.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index 10e56522122a..46d4300dd48d 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -145,6 +145,7 @@ ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
regs->pc = afregs->pc;
regs->regs[29] = afregs->fp;
regs->regs[30] = afregs->lr;
+ regs->pstate = PSR_MODE_EL1h;
return regs;
}
--
2.47.3
Amazon Web Services Development Center Germany GmbH
Tamara-Danz-Str. 13
10243 Berlin
Geschaeftsfuehrung: Christof Hellmis, Andreas Stieger
Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B
Sitz: Berlin
Ust-ID: DE 365 538 597
next reply other threads:[~2026-05-26 19:21 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-26 19:20 Gyokhan Kochmarla [this message]
2026-05-27 19:49 ` [PATCH 6.12] tracing: Fix the bug where bpf_get_stackid returns -EFAULT on the ARM64 Sasha Levin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260526192012.76223-1-gyokhan@amazon.de \
--to=gyokhan@amazon$(echo .)de \
--cc=bpf@vger$(echo .)kernel.org \
--cc=catalin.marinas@arm$(echo .)com \
--cc=gregkh@linuxfoundation$(echo .)org \
--cc=jolsa@kernel$(echo .)org \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
--cc=linux-trace-kernel@vger$(echo .)kernel.org \
--cc=mark.rutland@arm$(echo .)com \
--cc=mhiramat@kernel$(echo .)org \
--cc=rostedt@goodmis$(echo .)org \
--cc=stable@vger$(echo .)kernel.org \
--cc=will@kernel$(echo .)org \
--cc=yangfeng@kylinos$(echo .)cn \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox