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Date: Thu, 23 Apr 2020 17:40:38 +0200
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: Peter Zijlstra <peterz@...radead.org>, jpoimboe@...hat.com
Cc: linux-kernel@...r.kernel.org, jthierry@...hat.com,
tglx@...utronix.de, x86@...nel.org, mbenes@...e.cz
Subject: Re: [PATCH 3/8] objtool: Rework allocating stack_ops on decode
On 4/23/20 2:47 PM, Peter Zijlstra wrote:
> Wrap each stack_op in a macro that allocates and adds it to the list.
> This simplifies trying to figure out what to do with the pre-allocated
> stack_op at the end.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
> tools/objtool/arch/x86/decode.c | 257 +++++++++++++++++++++++-----------------
> 1 file changed, 153 insertions(+), 104 deletions(-)
>
> --- a/tools/objtool/arch/x86/decode.c
> +++ b/tools/objtool/arch/x86/decode.c
> @@ -77,6 +77,17 @@ unsigned long arch_jump_destination(stru
> return insn->offset + insn->len + insn->immediate;
> }
>
> +#define PUSH_OP(op) \
> +({ \
> + list_add_tail(&op->list, ops_list); \
> + NULL; \
> +})
> +
> +#define ADD_OP(op) \
> + if (!(op = calloc(1, sizeof(*op)))) \
> + return -1; \
> + else for (; op; op = PUSH_OP(op))
> +
I would better have a function to alloc+add op instead of weird macros,
for example:
static struct stack_op *add_op(void)
{
struct stack *op;
op = calloc(1, sizeof(*op));
if (!op)
return NULL;
list_add_tail(&op->list, ops_list);
}
Then it requires two more lines when using it but I think the code is much
cleaner and clearer, e.g.:
op = add_op();
if (!op)
return -1;
op->src.type = OP_SRC_ADD;
op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
op->dest.type = OP_DEST_REG;
op->dest.reg = CFI_SP;
alex.
> int arch_decode_instruction(struct elf *elf, struct section *sec,
> unsigned long offset, unsigned int maxlen,
> unsigned int *len, enum insn_type *type,
> @@ -88,7 +99,7 @@ int arch_decode_instruction(struct elf *
> unsigned char op1, op2, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0,
> rex_x = 0, modrm = 0, modrm_mod = 0, modrm_rm = 0,
> modrm_reg = 0, sib = 0;
> - struct stack_op *op;
> + struct stack_op *op = NULL;
>
> x86_64 = is_x86_64(elf);
> if (x86_64 == -1)
> @@ -129,10 +140,6 @@ int arch_decode_instruction(struct elf *
> if (insn.sib.nbytes)
> sib = insn.sib.bytes[0];
>
> - op = calloc(1, sizeof(*op));
> - if (!op)
> - return -1;
> -
> switch (op1) {
>
> case 0x1:
> @@ -141,10 +148,12 @@ int arch_decode_instruction(struct elf *
>
> /* add/sub reg, %rsp */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_ADD;
> - op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = CFI_SP;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_ADD;
> + op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = CFI_SP;
> + }
> }
> break;
>
> @@ -152,9 +161,11 @@ int arch_decode_instruction(struct elf *
>
> /* push reg */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_REG;
> - op->src.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
> - op->dest.type = OP_DEST_PUSH;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_REG;
> + op->src.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
> + op->dest.type = OP_DEST_PUSH;
> + }
>
> break;
>
> @@ -162,9 +173,11 @@ int arch_decode_instruction(struct elf *
>
> /* pop reg */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_POP;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
> + ADD_OP(op) {
> + op->src.type = OP_SRC_POP;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
> + }
>
> break;
>
> @@ -172,8 +185,10 @@ int arch_decode_instruction(struct elf *
> case 0x6a:
> /* push immediate */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_CONST;
> - op->dest.type = OP_DEST_PUSH;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_CONST;
> + op->dest.type = OP_DEST_PUSH;
> + }
> break;
>
> case 0x70 ... 0x7f:
> @@ -188,11 +203,13 @@ int arch_decode_instruction(struct elf *
> if (modrm == 0xe4) {
> /* and imm, %rsp */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_AND;
> - op->src.reg = CFI_SP;
> - op->src.offset = insn.immediate.value;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = CFI_SP;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_AND;
> + op->src.reg = CFI_SP;
> + op->src.offset = insn.immediate.value;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = CFI_SP;
> + }
> break;
> }
>
> @@ -205,11 +222,13 @@ int arch_decode_instruction(struct elf *
>
> /* add/sub imm, %rsp */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_ADD;
> - op->src.reg = CFI_SP;
> - op->src.offset = insn.immediate.value * sign;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = CFI_SP;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_ADD;
> + op->src.reg = CFI_SP;
> + op->src.offset = insn.immediate.value * sign;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = CFI_SP;
> + }
> break;
>
> case 0x89:
> @@ -217,10 +236,12 @@ int arch_decode_instruction(struct elf *
>
> /* mov %rsp, reg */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_REG;
> - op->src.reg = CFI_SP;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = op_to_cfi_reg[modrm_rm][rex_b];
> + ADD_OP(op) {
> + op->src.type = OP_SRC_REG;
> + op->src.reg = CFI_SP;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = op_to_cfi_reg[modrm_rm][rex_b];
> + }
> break;
> }
>
> @@ -228,10 +249,12 @@ int arch_decode_instruction(struct elf *
>
> /* mov reg, %rsp */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_REG;
> - op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = CFI_SP;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_REG;
> + op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = CFI_SP;
> + }
> break;
> }
>
> @@ -242,21 +265,25 @@ int arch_decode_instruction(struct elf *
>
> /* mov reg, disp(%rbp) */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_REG;
> - op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
> - op->dest.type = OP_DEST_REG_INDIRECT;
> - op->dest.reg = CFI_BP;
> - op->dest.offset = insn.displacement.value;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_REG;
> + op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
> + op->dest.type = OP_DEST_REG_INDIRECT;
> + op->dest.reg = CFI_BP;
> + op->dest.offset = insn.displacement.value;
> + }
>
> } else if (rex_w && !rex_b && modrm_rm == 4 && sib == 0x24) {
>
> /* mov reg, disp(%rsp) */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_REG;
> - op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
> - op->dest.type = OP_DEST_REG_INDIRECT;
> - op->dest.reg = CFI_SP;
> - op->dest.offset = insn.displacement.value;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_REG;
> + op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
> + op->dest.type = OP_DEST_REG_INDIRECT;
> + op->dest.reg = CFI_SP;
> + op->dest.offset = insn.displacement.value;
> + }
> }
>
> break;
> @@ -266,22 +293,26 @@ int arch_decode_instruction(struct elf *
>
> /* mov disp(%rbp), reg */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_REG_INDIRECT;
> - op->src.reg = CFI_BP;
> - op->src.offset = insn.displacement.value;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
> + ADD_OP(op) {
> + op->src.type = OP_SRC_REG_INDIRECT;
> + op->src.reg = CFI_BP;
> + op->src.offset = insn.displacement.value;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
> + }
>
> } else if (rex_w && !rex_b && sib == 0x24 &&
> modrm_mod != 3 && modrm_rm == 4) {
>
> /* mov disp(%rsp), reg */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_REG_INDIRECT;
> - op->src.reg = CFI_SP;
> - op->src.offset = insn.displacement.value;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
> + ADD_OP(op) {
> + op->src.type = OP_SRC_REG_INDIRECT;
> + op->src.reg = CFI_SP;
> + op->src.offset = insn.displacement.value;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
> + }
> }
>
> break;
> @@ -290,27 +321,31 @@ int arch_decode_instruction(struct elf *
> if (sib == 0x24 && rex_w && !rex_b && !rex_x) {
>
> *type = INSN_STACK;
> - if (!insn.displacement.value) {
> - /* lea (%rsp), reg */
> - op->src.type = OP_SRC_REG;
> - } else {
> - /* lea disp(%rsp), reg */
> - op->src.type = OP_SRC_ADD;
> - op->src.offset = insn.displacement.value;
> + ADD_OP(op) {
> + if (!insn.displacement.value) {
> + /* lea (%rsp), reg */
> + op->src.type = OP_SRC_REG;
> + } else {
> + /* lea disp(%rsp), reg */
> + op->src.type = OP_SRC_ADD;
> + op->src.offset = insn.displacement.value;
> + }
> + op->src.reg = CFI_SP;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
> }
> - op->src.reg = CFI_SP;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
>
> } else if (rex == 0x48 && modrm == 0x65) {
>
> /* lea disp(%rbp), %rsp */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_ADD;
> - op->src.reg = CFI_BP;
> - op->src.offset = insn.displacement.value;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = CFI_SP;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_ADD;
> + op->src.reg = CFI_BP;
> + op->src.offset = insn.displacement.value;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = CFI_SP;
> + }
>
> } else if (rex == 0x49 && modrm == 0x62 &&
> insn.displacement.value == -8) {
> @@ -322,11 +357,13 @@ int arch_decode_instruction(struct elf *
> * stack realignment.
> */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_ADD;
> - op->src.reg = CFI_R10;
> - op->src.offset = -8;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = CFI_SP;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_ADD;
> + op->src.reg = CFI_R10;
> + op->src.offset = -8;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = CFI_SP;
> + }
>
> } else if (rex == 0x49 && modrm == 0x65 &&
> insn.displacement.value == -16) {
> @@ -338,11 +375,13 @@ int arch_decode_instruction(struct elf *
> * stack realignment.
> */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_ADD;
> - op->src.reg = CFI_R13;
> - op->src.offset = -16;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = CFI_SP;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_ADD;
> + op->src.reg = CFI_R13;
> + op->src.offset = -16;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = CFI_SP;
> + }
> }
>
> break;
> @@ -350,8 +389,10 @@ int arch_decode_instruction(struct elf *
> case 0x8f:
> /* pop to mem */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_POP;
> - op->dest.type = OP_DEST_MEM;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_POP;
> + op->dest.type = OP_DEST_MEM;
> + }
> break;
>
> case 0x90:
> @@ -361,15 +402,19 @@ int arch_decode_instruction(struct elf *
> case 0x9c:
> /* pushf */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_CONST;
> - op->dest.type = OP_DEST_PUSHF;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_CONST;
> + op->dest.type = OP_DEST_PUSHF;
> + }
> break;
>
> case 0x9d:
> /* popf */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_POPF;
> - op->dest.type = OP_DEST_MEM;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_POPF;
> + op->dest.type = OP_DEST_MEM;
> + }
> break;
>
> case 0x0f:
> @@ -405,15 +450,19 @@ int arch_decode_instruction(struct elf *
>
> /* push fs/gs */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_CONST;
> - op->dest.type = OP_DEST_PUSH;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_CONST;
> + op->dest.type = OP_DEST_PUSH;
> + }
>
> } else if (op2 == 0xa1 || op2 == 0xa9) {
>
> /* pop fs/gs */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_POP;
> - op->dest.type = OP_DEST_MEM;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_POP;
> + op->dest.type = OP_DEST_MEM;
> + }
> }
>
> break;
> @@ -427,7 +476,8 @@ int arch_decode_instruction(struct elf *
> * pop bp
> */
> *type = INSN_STACK;
> - op->dest.type = OP_DEST_LEAVE;
> + ADD_OP(op)
> + op->dest.type = OP_DEST_LEAVE;
>
> break;
>
> @@ -449,12 +499,14 @@ int arch_decode_instruction(struct elf *
> case 0xcf: /* iret */
> *type = INSN_EXCEPTION_RETURN;
>
> - /* add $40, %rsp */
> - op->src.type = OP_SRC_ADD;
> - op->src.reg = CFI_SP;
> - op->src.offset = 5*8;
> - op->dest.type = OP_DEST_REG;
> - op->dest.reg = CFI_SP;
> + ADD_OP(op) {
> + /* add $40, %rsp */
> + op->src.type = OP_SRC_ADD;
> + op->src.reg = CFI_SP;
> + op->src.offset = 5*8;
> + op->dest.type = OP_DEST_REG;
> + op->dest.reg = CFI_SP;
> + }
> break;
>
> case 0xca: /* retf */
> @@ -492,8 +544,10 @@ int arch_decode_instruction(struct elf *
>
> /* push from mem */
> *type = INSN_STACK;
> - op->src.type = OP_SRC_CONST;
> - op->dest.type = OP_DEST_PUSH;
> + ADD_OP(op) {
> + op->src.type = OP_SRC_CONST;
> + op->dest.type = OP_DEST_PUSH;
> + }
> }
>
> break;
> @@ -504,11 +558,6 @@ int arch_decode_instruction(struct elf *
>
> *immediate = insn.immediate.nbytes ? insn.immediate.value : 0;
>
> - if (*type == INSN_STACK || *type == INSN_EXCEPTION_RETURN)
> - list_add_tail(&op->list, ops_list);
> - else
> - free(op);
> -
> return 0;
> }
>
>
>
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