Re: [PATCH v11 8/9] arm64: Add kernel return probes support (kretprobes)

From: David Long
Date: Mon Mar 21 2016 - 09:34:14 EST

On 03/17/2016 08:58 AM, 平松雅巳 / HIRAMATU,MASAMI wrote:
From: 平松雅巳 / HIRAMATU,MASAMI []


From: Sandeepa Prabhu <sandeepa.s.prabhu@xxxxxxxxx>

The pre-handler of this special 'trampoline' kprobe executes the return
probe handler functions and restores original return address in ELR_EL1.
This way the saved pt_regs still hold the original register context to be
carried back to the probed kernel function.

This patch seems not well separated.

diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c
index bd3f233..13d3333 100644
--- a/arch/arm64/kernel/kprobes.c
+++ b/arch/arm64/kernel/kprobes.c


+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
+ struct pt_regs *regs)
+ ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
+ /* replace return addr (x30) with trampoline */
+ regs->regs[30] = (long)&kretprobe_trampoline;

So, where is the kretprobe_trampoline? It seems that function is
defined in other patch.

+int __kprobes arch_trampoline_kprobe(struct kprobe *p)
+ return 0;

And what this function is for??

Ah, sorry, this was my fault. Yes, this function is required.
But this implementation also means there is an asm-based trampoline
function which should be included in this patch.

David, could you tell me the repository which I can get the latest
version of this series? I'd like to see the whole code of kprobes/arm64.

Thank you,

It can be found in: the kprobes64-v11 branch.