Re: [RFC][PATCH] ftrace/x86: Emulate call function while updating in breakpoint handler

On Wed, May 01, 2019 at 02:58:24PM -0400, Steven Rostedt wrote:

...

• if (ftrace_location(ip)) {

• int3_emulate_call(regs, ftrace_update_func_call);
  

Should be:

int3_emulate_call(regs, (unsigned long)ftrace_regs_caller);

Ah, I lost the plot a little there.

...

• return 1;
  

• } else if (is_ftrace_caller(ip)) {

• if (!ftrace_update_func_call) {
  

• 	int3_emulate_jmp(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
  

I see what you did here, but I think:

	int3_emulate_jmp(regs, ip + CALL_INSN_SIZE);

looks better. But that said, we could in the beginning do:

ip = regs->ip - INT3_INSN_SIZE;

instead of

ip = regs->ip - 1;

I made these updates and posted them to Linus.

I was actually considering:

static inline void int3_emulate_nop(struct pt_regs *regs, unsigned long size) { int3_emulate_jmp(regs, regs->ip - INT3_INSN_SIZE + size); }

And then the above becomes:

int3_emulate_nop(regs, CALL_INSN_SIZE);

Hmm?