[PATCH] tracing: Fix the bug where bpf_get_stackid returns -EFAULT on the ARM64

[Will Deacon]

On Thu, 25 Sep 2025 10:08:22 +0800, Feng Yang wrote:
> 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.
> 
> [...]

Applied to arm64 (for-next/core), thanks!

[1/1] tracing: Fix the bug where bpf_get_stackid returns -EFAULT on the ARM64
      https://git.kernel.org/arm64/c/fd2f74f8f3d3

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
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