linux-kernel - [for-next][PATCH 35/40] arm64: kprobes: Record frame pointer with kretprobe instance

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Message-ID: <20211022204844.638189907@goodmis.org>
Date:   Fri, 22 Oct 2021 16:48:31 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: [for-next][PATCH 35/40] arm64: kprobes: Record frame pointer with kretprobe instance

From: Masami Hiramatsu <mhiramat@...nel.org>

Record the frame pointer instead of stack address with kretprobe
instance as the identifier on the instance list.
Since arm64 always enable CONFIG_FRAME_POINTER, we can use the
actual frame pointer (x29).

This will allow the stacktrace code to find the original return
address from the FP alone.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Acked-by: Will Deacon <will@...nel.org>
Acked-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 arch/arm64/kernel/probes/kprobes.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index e7ad6da980e8..d9dfa82c1f18 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -401,14 +401,14 @@ int __init arch_populate_kprobe_blacklist(void)
 
 void __kprobes __used *trampoline_probe_handler(struct pt_regs *regs)
 {
-	return (void *)kretprobe_trampoline_handler(regs, (void *)kernel_stack_pointer(regs));
+	return (void *)kretprobe_trampoline_handler(regs, (void *)regs->regs[29]);
 }
 
 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 				      struct pt_regs *regs)
 {
 	ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
-	ri->fp = (void *)kernel_stack_pointer(regs);
+	ri->fp = (void *)regs->regs[29];
 
 	/* replace return addr (x30) with trampoline */
 	regs->regs[30] = (long)&__kretprobe_trampoline;
-- 
2.33.0