From: Feng Yang <[email protected]>
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/[email protected]/
Signed-off-by: Feng Yang <[email protected]>
---
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 bfe3ce9df197..ba7cf7fec5e9 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;
}
--
2.25.1
