Messages in this thread | | | Date | Tue, 8 Oct 2019 10:40:10 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH v3 1/6] x86/alternatives: Teach text_poke_bp() to emulate instructions |
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On Tue, 8 Oct 2019 16:29:24 +0200 Borislav Petkov <bp@alien8.de> wrote:
> On Mon, Oct 07, 2019 at 10:17:17AM +0200, 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. > > ... > > > @@ -63,8 +66,17 @@ static inline void int3_emulate_jmp(stru > > regs->ip = ip; > > } > > > > -#define INT3_INSN_SIZE 1 > > -#define CALL_INSN_SIZE 5 > > +#define INT3_INSN_SIZE 1 > > +#define INT3_INSN_OPCODE 0xCC > > + > > +#define CALL_INSN_SIZE 5 > > +#define CALL_INSN_OPCODE 0xE8 > > + > > +#define JMP32_INSN_SIZE 5 > > +#define JMP32_INSN_OPCODE 0xE9 > > + > > +#define JMP8_INSN_SIZE 2 > > +#define JMP8_INSN_OPCODE 0xEB > > You probably should switch those to have the name prefix come first and > make them even shorter: > > OPCODE_CALL > INSN_SIZE_CALL > OPCODE_JMP32 > INSN_SIZE_JMP32 > OPCODE_JMP8 > ... > > This way you have the opcodes prefixed with OPCODE_ and the insn sizes > with INSN_SIZE_. I.e., what they actually are.
Honestly, I like the original way better.
Seeing OPCODE_JMP32 and INSN_SIZE_JMP32 doesn't look like they are related to me.
-- Steve
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