6.17-stable review patch. If anyone has any objections, please let me know.
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From: Feng Yang yangfeng@kylinos.cn
[ Upstream commit fd2f74f8f3d3c1a524637caf5bead9757fae4332 ]
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: Sasha Levin sashal@kernel.org --- 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 bfe3ce9df1978..ba7cf7fec5e97 100644 --- a/arch/arm64/include/asm/ftrace.h +++ b/arch/arm64/include/asm/ftrace.h @@ -153,6 +153,7 @@ 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; }