From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masami Hiramatsu Date: Tue, 23 Mar 2021 00:04:29 +0000 Subject: Re: [PATCH -tip v4 08/12] arm: kprobes: Make a space for regs->ARM_pc at kretprobe_trampoline Message-Id: <20210323090429.da18461654ef9907581dab95@kernel.org> List-Id: References: <161639518354.895304.15627519393073806809.stgit@devnote2> <161639527851.895304.14313883616251450754.stgit@devnote2> In-Reply-To: <161639527851.895304.14313883616251450754.stgit@devnote2> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Masami Hiramatsu Cc: Steven Rostedt , Ingo Molnar , X86 ML , Daniel Xu , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, tglx@linutronix.de, kernel-team@fb.com, yhs@fb.com, Josh Poimboeuf , linux-ia64@vger.kernel.org, Abhishek Sagar On Mon, 22 Mar 2021 15:41:18 +0900 Masami Hiramatsu wrote: > Change kretprobe_trampoline to make a space for regs->ARM_pc so that > kretprobe_trampoline_handler can call instruction_pointer_set() > safely. BTW, if kretprobe_trampoline is replaced with the assembly code, I think it should fill all the regs as much as possible, because originally it is written by a software break. Thus the regs->sp should point the stack address at the entry of kretprobe_trampoline, and also regs->lr and regs->pc will be kretprobe_trampoline, so that user handler can access caller stack. Thanks, > > Signed-off-by: Masami Hiramatsu > --- > 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 1782b41df095..5f3c2b42787f 100644 > --- a/arch/arm/probes/kprobes/core.c > +++ b/arch/arm/probes/kprobes/core.c > @@ -397,11 +397,13 @@ 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 > -- Masami Hiramatsu