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Date: Tue, 8 Oct 2019 15:23:49 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, rostedt@...dmis.org,
mhiramat@...nel.org, bristot@...hat.com, jbaron@...mai.com,
torvalds@...ux-foundation.org, tglx@...utronix.de,
mingo@...nel.org, namit@...are.com, hpa@...or.com, luto@...nel.org,
ard.biesheuvel@...aro.org, jpoimboe@...hat.com
Subject: Re: [PATCH v3 4/6] x86/alternatives: Add and use text_gen_insn()
helper
On Mon, 07 Oct 2019 10:17:20 +0200
Peter Zijlstra <peterz@...radead.org> wrote:
> Provide a simple helper function to create common instruction
> encodings.
Thanks for using correct INSN_OPCODE:)
This looks good to me.
Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>
Thanks,
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> ---
> arch/x86/include/asm/text-patching.h | 2 +
> arch/x86/kernel/alternative.c | 36 +++++++++++++++++++++++++++++++++++
> arch/x86/kernel/jump_label.c | 31 ++++++++++--------------------
> arch/x86/kernel/kprobes/opt.c | 7 ------
> 4 files changed, 50 insertions(+), 26 deletions(-)
>
> --- a/arch/x86/include/asm/text-patching.h
> +++ b/arch/x86/include/asm/text-patching.h
> @@ -49,6 +49,8 @@ extern void text_poke_bp(void *addr, con
> extern void text_poke_queue(void *addr, const void *opcode, size_t len, const void *emulate);
> extern void text_poke_finish(void);
>
> +extern void *text_gen_insn(u8 opcode, const void *addr, const void *dest);
> +
> extern int after_bootmem;
> extern __ro_after_init struct mm_struct *poking_mm;
> extern __ro_after_init unsigned long poking_addr;
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -1237,3 +1237,39 @@ void text_poke_bp(void *addr, const void
> text_poke_loc_init(&tp, addr, opcode, len, emulate);
> text_poke_bp_batch(&tp, 1);
> }
> +
> +union text_poke_insn {
> + u8 text[POKE_MAX_OPCODE_SIZE];
> + struct {
> + u8 opcode;
> + s32 disp;
> + } __attribute__((packed));
> +};
> +
> +void *text_gen_insn(u8 opcode, const void *addr, const void *dest)
> +{
> + static union text_poke_insn insn; /* text_mutex */
> + int size = 0;
> +
> + lockdep_assert_held(&text_mutex);
> +
> + insn.opcode = opcode;
> +
> +#define __CASE(insn) \
> + case insn##_INSN_OPCODE: size = insn##_INSN_SIZE; break
> +
> + switch(opcode) {
> + __CASE(INT3);
> + __CASE(CALL);
> + __CASE(JMP32);
> + __CASE(JMP8);
> + }
> +
> + if (size > 1) {
> + insn.disp = (long)dest - (long)(addr + size);
> + if (size == 2)
> + BUG_ON((insn.disp >> 31) != (insn.disp >> 7));
> + }
> +
> + return &insn.text;
> +}
> --- a/arch/x86/kernel/jump_label.c
> +++ b/arch/x86/kernel/jump_label.c
> @@ -16,15 +16,7 @@
> #include <asm/alternative.h>
> #include <asm/text-patching.h>
>
> -union jump_code_union {
> - char code[JUMP_LABEL_NOP_SIZE];
> - struct {
> - char jump;
> - int offset;
> - } __attribute__((packed));
> -};
> -
> -static void bug_at(unsigned char *ip, int line)
> +static void bug_at(const void *ip, int line)
> {
> /*
> * The location is not an op that we were expecting.
> @@ -38,33 +30,32 @@ static void bug_at(unsigned char *ip, in
> static const void *
> __jump_label_set_jump_code(struct jump_entry *entry, enum jump_label_type type, int init)
> {
> - static union jump_code_union code; /* relies on text_mutex */
> const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
> const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
> - const void *expect;
> + const void *expect, *code;
> + const void *addr, *dest;
> int line;
>
> - lockdep_assert_held(&text_mutex);
> + addr = (void *)jump_entry_code(entry);
> + dest = (void *)jump_entry_target(entry);
>
> - code.jump = JMP32_INSN_OPCODE;
> - code.offset = jump_entry_target(entry) -
> - (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
> + code = text_gen_insn(JMP32_INSN_OPCODE, addr, dest);
>
> if (init) {
> expect = default_nop; line = __LINE__;
> } else if (type == JUMP_LABEL_JMP) {
> expect = ideal_nop; line = __LINE__;
> } else {
> - expect = code.code; line = __LINE__;
> + expect = code; line = __LINE__;
> }
>
> - if (memcmp((void *)jump_entry_code(entry), expect, JUMP_LABEL_NOP_SIZE))
> - bug_at((void *)jump_entry_code(entry), line);
> + if (memcmp(addr, expect, JUMP_LABEL_NOP_SIZE))
> + bug_at(addr, line);
>
> if (type == JUMP_LABEL_NOP)
> - memcpy(&code, ideal_nop, JUMP_LABEL_NOP_SIZE);
> + code = ideal_nop;
>
> - return &code;
> + return code;
> }
>
> static void inline __jump_label_transform(struct jump_entry *entry,
> --- a/arch/x86/kernel/kprobes/opt.c
> +++ b/arch/x86/kernel/kprobes/opt.c
> @@ -447,18 +447,13 @@ void arch_optimize_kprobes(struct list_h
> void arch_unoptimize_kprobe(struct optimized_kprobe *op)
> {
> u8 insn_buff[RELATIVEJUMP_SIZE];
> - u8 emulate_buff[RELATIVEJUMP_SIZE];
>
> /* Set int3 to first byte for kprobes */
> insn_buff[0] = BREAKPOINT_INSTRUCTION;
> memcpy(insn_buff + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
>
> - emulate_buff[0] = RELATIVEJUMP_OPCODE;
> - *(s32 *)(&emulate_buff[1]) = (s32)((long)op->optinsn.insn -
> - ((long)op->kp.addr + RELATIVEJUMP_SIZE));
> -
> text_poke_bp(op->kp.addr, insn_buff, RELATIVEJUMP_SIZE,
> - emulate_buff);
> + text_gen_insn(JMP32_INSN_OPCODE, op->kp.addr, op->optinsn.insn));
> }
>
> /*
>
>
--
Masami Hiramatsu <mhiramat@...nel.org>
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