linux-kernel - [for-linus][PATCH 22/27] arm: kprobes: Make space for instruction pointer on stack

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Date:   Tue, 05 Oct 2021 09:57:55 -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>
Subject: [for-linus][PATCH 22/27] arm: kprobes: Make space for instruction pointer on stack

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

Since arm's __kretprobe_trampoline() saves partial 'pt_regs' on the
stack, 'regs->ARM_pc' (instruction pointer) is not accessible from
the kretprobe handler. This means if instruction_pointer_set() is
used from kretprobe handler, it will break the data on the stack.

Make space for instruction pointer (ARM_pc) on the stack in the
__kretprobe_trampoline() for fixing this problem.

Link: https://lkml.kernel.org/r/163163052262.489837.10327621053231461255.stgit@devnote2

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 arch/arm/probes/kprobes/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
index 67ce7eb8f285..95f23b47ba27 100644
--- a/arch/arm/probes/kprobes/core.c
+++ b/arch/arm/probes/kprobes/core.c
@@ -376,11 +376,13 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 void __naked __kprobes __kretprobe_trampoline(void)
 {
 	__asm__ __volatile__ (
+		"sub	sp, sp, #16		\n\t"
 		"stmdb	sp!, {r0 - r11}		\n\t"
 		"mov	r0, sp			\n\t"
 		"bl	trampoline_handler	\n\t"
 		"mov	lr, r0			\n\t"
 		"ldmia	sp!, {r0 - r11}		\n\t"
+		"add	sp, sp, #16		\n\t"
 #ifdef CONFIG_THUMB2_KERNEL
 		"bx	lr			\n\t"
 #else
-- 
2.32.0