Re: [PATCH v3 1/6] x86/alternatives: Teach text_poke_bp() to emulate instructions

[Daniel Bristot de Oliveira]

On 07/10/2019 10:17, Peter Zijlstra wrote:
> In preparation for static_call and variable size jump_label support,
> teach text_poke_bp() to emulate instructions, namely:
> 
>   JMP32, JMP8, CALL, NOP2, NOP_ATOMIC5, INT3
> 
> The current text_poke_bp() takes a @handler argument which is used as
> a jump target when the temporary INT3 is hit by a different CPU.
> 
> When patching CALL instructions, this doesn't work because we'd miss
> the PUSH of the return address. Instead, teach poke_int3_handler() to
> emulate an instruction, typically the instruction we're patching in.
> 
> This fits almost all text_poke_bp() users, except
> arch_unoptimize_kprobe() which restores random text, and for that site
> we have to build an explicit emulate instruction.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>

Reviewed-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>

Thanks!
-- Daniel