Re: [PATCH 8/9] x86/bpf: Convert asm comments to AT&T syntax

From: Song Liu
Date: Thu Jun 13 2019 - 14:59:17 EST

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In reply to: Josh Poimboeuf: "[PATCH 8/9] x86/bpf: Convert asm comments to AT&T syntax"
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> On Jun 13, 2019, at 6:21 AM, Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
>
> Convert the BPF JIT assembly comments to AT&T syntax to reduce
> confusion. AT&T syntax is the default standard, used throughout Linux
> and by the GNU assembler.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> ---
> arch/x86/net/bpf_jit_comp.c | 156 ++++++++++++++++++------------------
> 1 file changed, 78 insertions(+), 78 deletions(-)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index bb1968fea50a..a92c2445441d 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -58,7 +58,7 @@ static bool is_uimm32(u64 value)
> return value == (u64)(u32)value;
> }
>
> -/* mov dst, src */
> +/* mov src, dst */
> #define EMIT_mov(DST, SRC) \
> do { \
> if (DST != SRC) \
> @@ -202,21 +202,21 @@ static void emit_prologue(u8 **pprog, u32 stack_depth)
> u8 *prog = *pprog;
> int cnt = 0;
>
> - /* push rbp */
> + /* push %rbp */
> EMIT1(0x55);
>
> - /* mov rbp, rsp */
> + /* mov %rsp, %rbp */
> EMIT3(0x48, 0x89, 0xE5);
>
> - /* push r15 */
> + /* push %r15 */
> EMIT2(0x41, 0x57);
> - /* push r14 */
> + /* push %r14 */
> EMIT2(0x41, 0x56);
> - /* push r13 */
> + /* push %r13 */
> EMIT2(0x41, 0x55);
> - /* push r12 */
> + /* push %r12 */
> EMIT2(0x41, 0x54);
> - /* push rbx */
> + /* push %rbx */
> EMIT1(0x53);
>
> /*
> @@ -231,11 +231,11 @@ static void emit_prologue(u8 **pprog, u32 stack_depth)
> * R12 is used for the BPF program's FP register. It points to the end
> * of the program's stack area.
> *
> - * mov r12, rsp
> + * mov %rsp, %r12
> */
> EMIT3(0x49, 0x89, 0xE4);
>
> - /* sub rsp, rounded_stack_depth */
> + /* sub rounded_stack_depth, %rsp */
> EMIT3_off32(0x48, 0x81, 0xEC, round_up(stack_depth, 8));
>
> BUILD_BUG_ON(cnt != PROLOGUE_SIZE);
> @@ -248,20 +248,20 @@ static void emit_epilogue(u8 **pprog)
> u8 *prog = *pprog;
> int cnt = 0;
>
> - /* lea rsp, [rbp-0x28] */
> + /* lea -0x28(%rbp), %rsp */
> EMIT4(0x48, 0x8D, 0x65, 0xD8);
>
> - /* pop rbx */
> + /* pop %rbx */
> EMIT1(0x5B);
> - /* pop r12 */
> + /* pop %r12 */
> EMIT2(0x41, 0x5C);
> - /* pop r13 */
> + /* pop %r13 */
> EMIT2(0x41, 0x5D);
> - /* pop r14 */
> + /* pop %r14 */
> EMIT2(0x41, 0x5E);
> - /* pop r15 */
> + /* pop %r15 */
> EMIT2(0x41, 0x5F);
> - /* pop rbp */
> + /* pop %rbp */
> EMIT1(0x5D);
>
> /* ret */
> @@ -300,8 +300,8 @@ static void emit_bpf_tail_call(u8 **pprog)
> * if (index >= array->map.max_entries)
> * goto out;
> */
> - EMIT2(0x89, 0xD2); /* mov edx, edx */
> - EMIT3(0x39, 0x56, /* cmp dword ptr [rsi + 16], edx */
> + EMIT2(0x89, 0xD2); /* mov %edx, %edx */
> + EMIT3(0x39, 0x56, /* cmp %edx, 0x10(%rsi) */
> offsetof(struct bpf_array, map.max_entries));
> #define OFFSET1 (35 + RETPOLINE_RAX_BPF_JIT_SIZE) /* Number of bytes to jump */
> EMIT2(X86_JBE, OFFSET1); /* jbe out */
> @@ -311,31 +311,31 @@ static void emit_bpf_tail_call(u8 **pprog)
> * if (tail_call_cnt > MAX_TAIL_CALL_CNT)
> * goto out;
> */
> - EMIT3(0x8B, 0x45, 0xD4); /* mov eax, dword ptr [rbp - 44] */
> - EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp eax, MAX_TAIL_CALL_CNT */
> + EMIT3(0x8B, 0x45, 0xD4); /* mov -0x2c(%rbp), %eax */
> + EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp MAX_TAIL_CALL_CNT, %eax */
> #define OFFSET2 (27 + RETPOLINE_RAX_BPF_JIT_SIZE)
> EMIT2(X86_JA, OFFSET2); /* ja out */
> label2 = cnt;
> - EMIT3(0x83, 0xC0, 0x01); /* add eax, 1 */
> - EMIT3(0x89, 0x45, 0xD4); /* mov dword ptr [rbp - 44], eax */
> + EMIT3(0x83, 0xC0, 0x01); /* add $0x1, %eax */
> + EMIT3(0x89, 0x45, 0xD4); /* mov %eax, -0x2c(%rbp) */
>
> /* prog = array->ptrs[index]; */
> - EMIT4_off32(0x48, 0x8B, 0x84, 0xD6, /* mov rax, [rsi + rdx * 8 + offsetof(...)] */
> + EMIT4_off32(0x48, 0x8B, 0x84, 0xD6, /* mov offsetof(ptrs)(%rsi,%rdx,8), %rax */
> offsetof(struct bpf_array, ptrs));
>
> /*
> * if (prog == NULL)
> * goto out;
> */
> - EMIT3(0x48, 0x85, 0xC0); /* test rax,rax */
> + EMIT3(0x48, 0x85, 0xC0); /* test %rax, %rax */
> #define OFFSET3 (8 + RETPOLINE_RAX_BPF_JIT_SIZE)
> EMIT2(X86_JE, OFFSET3); /* je out */
> label3 = cnt;
>
> /* goto *(prog->bpf_func + prologue_size); */
> - EMIT4(0x48, 0x8B, 0x40, /* mov rax, qword ptr [rax + 32] */
> + EMIT4(0x48, 0x8B, 0x40, /* mov offsetof(bpf_func)(%rax), %rax */
> offsetof(struct bpf_prog, bpf_func));
> - EMIT4(0x48, 0x83, 0xC0, PROLOGUE_SIZE); /* add rax, prologue_size */
> + EMIT4(0x48, 0x83, 0xC0, PROLOGUE_SIZE); /* add $PROLOGUE_SIZE, %rax */
>
> /*
> * Wow we're ready to jump into next BPF program
> @@ -359,11 +359,11 @@ static void emit_mov_imm32(u8 **pprog, bool sign_propagate,
> int cnt = 0;
>
> /*
> - * Optimization: if imm32 is positive, use 'mov %eax, imm32'
> + * Optimization: if imm32 is positive, use 'mov imm32, %eax'
> * (which zero-extends imm32) to save 2 bytes.
> */
> if (sign_propagate && (s32)imm32 < 0) {
> - /* 'mov %rax, imm32' sign extends imm32 */
> + /* 'mov imm32, %rax' sign extends imm32 */
> b1 = add_1mod(0x48, dst_reg);
> b2 = 0xC7;
> b3 = 0xC0;
> @@ -384,7 +384,7 @@ static void emit_mov_imm32(u8 **pprog, bool sign_propagate,
> goto done;
> }
>
> - /* mov %eax, imm32 */
> + /* mov imm32, %eax */
> if (is_ereg(dst_reg))
> EMIT1(add_1mod(0x40, dst_reg));
> EMIT1_off32(add_1reg(0xB8, dst_reg), imm32);
> @@ -403,11 +403,11 @@ static void emit_mov_imm64(u8 **pprog, u32 dst_reg,
> * For emitting plain u32, where sign bit must not be
> * propagated LLVM tends to load imm64 over mov32
> * directly, so save couple of bytes by just doing
> - * 'mov %eax, imm32' instead.
> + * 'mov imm32, %eax' instead.
> */
> emit_mov_imm32(&prog, false, dst_reg, imm32_lo);
> } else {
> - /* movabsq %rax, imm64 */
> + /* movabs imm64, %rax */

^^^^^ Should this be moveabsq?

> EMIT2(add_1mod(0x48, dst_reg), add_1reg(0xB8, dst_reg));
> EMIT(imm32_lo, 4);
> EMIT(imm32_hi, 4);
> @@ -422,10 +422,10 @@ static void emit_mov_reg(u8 **pprog, bool is64, u32 dst_reg, u32 src_reg)
> int cnt = 0;
>
> if (is64) {
> - /* mov dst, src */
> + /* mov src, dst */
> EMIT_mov(dst_reg, src_reg);
> } else {
> - /* mov32 dst, src */
> + /* mov32 src, dst */
> if (is_ereg(dst_reg) || is_ereg(src_reg))
> EMIT1(add_2mod(0x40, dst_reg, src_reg));
> EMIT2(0x89, add_2reg(0xC0, dst_reg, src_reg));
> @@ -571,43 +571,43 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> case BPF_ALU64 | BPF_DIV | BPF_X:
> case BPF_ALU64 | BPF_MOD | BPF_K:
> case BPF_ALU64 | BPF_DIV | BPF_K:
> - EMIT1(0x50); /* push rax */
> - EMIT1(0x52); /* push rdx */
> + EMIT1(0x50); /* push %rax */
> + EMIT1(0x52); /* push %rdx */
>
> if (BPF_SRC(insn->code) == BPF_X)
> - /* mov r11, src_reg */
> + /* mov src_reg, %r11 */
> EMIT_mov(AUX_REG, src_reg);
> else
> - /* mov r11, imm32 */
> + /* mov imm32, %r11 */
> EMIT3_off32(0x49, 0xC7, 0xC3, imm32);
>
> - /* mov rax, dst_reg */
> + /* mov dst_reg, %rax */
> EMIT_mov(BPF_REG_0, dst_reg);
>
> /*
> - * xor edx, edx
> - * equivalent to 'xor rdx, rdx', but one byte less
> + * xor %edx, %edx
> + * equivalent to 'xor %rdx, %rdx', but one byte less
> */
> EMIT2(0x31, 0xd2);
>
> if (BPF_CLASS(insn->code) == BPF_ALU64)
> - /* div r11 */
> + /* div %r11 */
> EMIT3(0x49, 0xF7, 0xF3);
> else
> - /* div r11d */
> + /* div %r11d */
> EMIT3(0x41, 0xF7, 0xF3);
>
> if (BPF_OP(insn->code) == BPF_MOD)
> - /* mov r11, rdx */
> + /* mov %r11, %rdx */
> EMIT3(0x49, 0x89, 0xD3);
> else
> - /* mov r11, rax */
> + /* mov %r11, %rax */
> EMIT3(0x49, 0x89, 0xC3);
>
> - EMIT1(0x5A); /* pop rdx */
> - EMIT1(0x58); /* pop rax */
> + EMIT1(0x5A); /* pop %rdx */
> + EMIT1(0x58); /* pop %rax */
>
> - /* mov dst_reg, r11 */
> + /* mov %r11, dst_reg */
> EMIT_mov(dst_reg, AUX_REG);
> break;
>
> @@ -619,11 +619,11 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> bool is64 = BPF_CLASS(insn->code) == BPF_ALU64;
>
> if (dst_reg != BPF_REG_0)
> - EMIT1(0x50); /* push rax */
> + EMIT1(0x50); /* push %rax */
> if (dst_reg != BPF_REG_3)
> - EMIT1(0x52); /* push rdx */
> + EMIT1(0x52); /* push %rdx */
>
> - /* mov r11, dst_reg */
> + /* mov dst_reg, %r11 */
> EMIT_mov(AUX_REG, dst_reg);
>
> if (BPF_SRC(insn->code) == BPF_X)
> @@ -635,15 +635,15 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> EMIT1(add_1mod(0x48, AUX_REG));
> else if (is_ereg(AUX_REG))
> EMIT1(add_1mod(0x40, AUX_REG));
> - /* mul(q) r11 */
> + /* mul(q) %r11 */
> EMIT2(0xF7, add_1reg(0xE0, AUX_REG));
>
> if (dst_reg != BPF_REG_3)
> - EMIT1(0x5A); /* pop rdx */
> + EMIT1(0x5A); /* pop %rdx */
> if (dst_reg != BPF_REG_0) {
> - /* mov dst_reg, rax */
> + /* mov %rax, dst_reg */
> EMIT_mov(dst_reg, BPF_REG_0);
> - EMIT1(0x58); /* pop rax */
> + EMIT1(0x58); /* pop %rax */
> }
> break;
> }
> @@ -678,21 +678,21 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> case BPF_ALU64 | BPF_RSH | BPF_X:
> case BPF_ALU64 | BPF_ARSH | BPF_X:
>
> - /* Check for bad case when dst_reg == rcx */
> + /* Check for bad case when dst_reg == %rcx */
> if (dst_reg == BPF_REG_4) {
> - /* mov r11, dst_reg */
> + /* mov dst_reg, %r11 */
> EMIT_mov(AUX_REG, dst_reg);
> dst_reg = AUX_REG;
> }
>
> if (src_reg != BPF_REG_4) { /* common case */
> - EMIT1(0x51); /* push rcx */
> + EMIT1(0x51); /* push %rcx */
>
> - /* mov rcx, src_reg */
> + /* mov src_reg, %rcx */
> EMIT_mov(BPF_REG_4, src_reg);
> }
>
> - /* shl %rax, %cl | shr %rax, %cl | sar %rax, %cl */
> + /* shl %cl, %rax | shr %cl, %rax | sar %cl, %rax */
> if (BPF_CLASS(insn->code) == BPF_ALU64)
> EMIT1(add_1mod(0x48, dst_reg));
> else if (is_ereg(dst_reg))
> @@ -706,23 +706,23 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> EMIT2(0xD3, add_1reg(b3, dst_reg));
>
> if (src_reg != BPF_REG_4)
> - EMIT1(0x59); /* pop rcx */
> + EMIT1(0x59); /* pop %rcx */
>
> if (insn->dst_reg == BPF_REG_4)
> - /* mov dst_reg, r11 */
> + /* mov %r11, dst_reg */
> EMIT_mov(insn->dst_reg, AUX_REG);
> break;
>
> case BPF_ALU | BPF_END | BPF_FROM_BE:
> switch (imm32) {
> case 16:
> - /* Emit 'ror %ax, 8' to swap lower 2 bytes */
> + /* Emit 'ror $0x8, %ax' to swap lower 2 bytes */
> EMIT1(0x66);
> if (is_ereg(dst_reg))
> EMIT1(0x41);
> EMIT3(0xC1, add_1reg(0xC8, dst_reg), 8);
>
> - /* Emit 'movzwl eax, ax' */
> + /* Emit 'movzwl %ax, %eax' */
> if (is_ereg(dst_reg))
> EMIT3(0x45, 0x0F, 0xB7);
> else
> @@ -730,7 +730,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> EMIT1(add_2reg(0xC0, dst_reg, dst_reg));
> break;
> case 32:
> - /* Emit 'bswap eax' to swap lower 4 bytes */
> + /* Emit 'bswap %eax' to swap lower 4 bytes */
> if (is_ereg(dst_reg))
> EMIT2(0x41, 0x0F);
> else
> @@ -738,7 +738,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> EMIT1(add_1reg(0xC8, dst_reg));
> break;
> case 64:
> - /* Emit 'bswap rax' to swap 8 bytes */
> + /* Emit 'bswap %rax' to swap 8 bytes */
> EMIT3(add_1mod(0x48, dst_reg), 0x0F,
> add_1reg(0xC8, dst_reg));
> break;
> @@ -749,7 +749,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> switch (imm32) {
> case 16:
> /*
> - * Emit 'movzwl eax, ax' to zero extend 16-bit
> + * Emit 'movzwl %ax, %eax' to zero extend 16-bit
> * into 64 bit
> */
> if (is_ereg(dst_reg))
> @@ -759,7 +759,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> EMIT1(add_2reg(0xC0, dst_reg, dst_reg));
> break;
> case 32:
> - /* Emit 'mov eax, eax' to clear upper 32-bits */
> + /* Emit 'mov %eax, %eax' to clear upper 32-bits */
> if (is_ereg(dst_reg))
> EMIT1(0x45);
> EMIT2(0x89, add_2reg(0xC0, dst_reg, dst_reg));
> @@ -811,7 +811,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
>
> /* STX: *(u8*)(dst_reg + off) = src_reg */
> case BPF_STX | BPF_MEM | BPF_B:
> - /* Emit 'mov byte ptr [rax + off], al' */
> + /* Emit 'mov %al, off(%rax)' */
> if (is_ereg(dst_reg) || is_ereg(src_reg) ||
> /* We have to add extra byte for x86 SIL, DIL regs */
> src_reg == BPF_REG_1 || src_reg == BPF_REG_2)
> @@ -850,22 +850,22 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
>
> /* LDX: dst_reg = *(u8*)(src_reg + off) */
> case BPF_LDX | BPF_MEM | BPF_B:
> - /* Emit 'movzx rax, byte ptr [rax + off]' */
> + /* Emit 'movzbl off(%rax), %rax' */
> EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xB6);
> goto ldx;
> case BPF_LDX | BPF_MEM | BPF_H:
> - /* Emit 'movzx rax, word ptr [rax + off]' */
> + /* Emit 'movzwl off(%rax), %rax' */
> EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xB7);
> goto ldx;
> case BPF_LDX | BPF_MEM | BPF_W:
> - /* Emit 'mov eax, dword ptr [rax+0x14]' */
> + /* Emit 'mov 0x14(%rax), %eax' */
> if (is_ereg(dst_reg) || is_ereg(src_reg))
> EMIT2(add_2mod(0x40, src_reg, dst_reg), 0x8B);
> else
> EMIT1(0x8B);
> goto ldx;
> case BPF_LDX | BPF_MEM | BPF_DW:
> - /* Emit 'mov rax, qword ptr [rax+0x14]' */
> + /* Emit 'mov 0x14(%rax), %rax' */
> EMIT2(add_2mod(0x48, src_reg, dst_reg), 0x8B);
> ldx:
> /*
> @@ -889,7 +889,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
>
> /* STX XADD: lock *(u32*)(dst_reg + off) += src_reg */
> case BPF_STX | BPF_XADD | BPF_W:
> - /* Emit 'lock add dword ptr [rax + off], eax' */
> + /* Emit 'lock add %eax, off(%rax)' */
> if (is_ereg(dst_reg) || is_ereg(src_reg))
> EMIT3(0xF0, add_2mod(0x40, dst_reg, src_reg), 0x01);
> else
> @@ -949,7 +949,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> case BPF_JMP32 | BPF_JSLT | BPF_X:
> case BPF_JMP32 | BPF_JSGE | BPF_X:
> case BPF_JMP32 | BPF_JSLE | BPF_X:
> - /* cmp dst_reg, src_reg */
> + /* cmp src_reg, dst_reg */
> if (BPF_CLASS(insn->code) == BPF_JMP)
> EMIT1(add_2mod(0x48, dst_reg, src_reg));
> else if (is_ereg(dst_reg) || is_ereg(src_reg))
> @@ -959,7 +959,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
>
> case BPF_JMP | BPF_JSET | BPF_X:
> case BPF_JMP32 | BPF_JSET | BPF_X:
> - /* test dst_reg, src_reg */
> + /* test src_reg, dst_reg */
> if (BPF_CLASS(insn->code) == BPF_JMP)
> EMIT1(add_2mod(0x48, dst_reg, src_reg));
> else if (is_ereg(dst_reg) || is_ereg(src_reg))
> @@ -969,7 +969,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
>
> case BPF_JMP | BPF_JSET | BPF_K:
> case BPF_JMP32 | BPF_JSET | BPF_K:
> - /* test dst_reg, imm32 */
> + /* test imm32, dst_reg */
> if (BPF_CLASS(insn->code) == BPF_JMP)
> EMIT1(add_1mod(0x48, dst_reg));
> else if (is_ereg(dst_reg))
> @@ -997,7 +997,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
> case BPF_JMP32 | BPF_JSLT | BPF_K:
> case BPF_JMP32 | BPF_JSGE | BPF_K:
> case BPF_JMP32 | BPF_JSLE | BPF_K:
> - /* cmp dst_reg, imm8/32 */
> + /* cmp imm8/32, dst_reg */
> if (BPF_CLASS(insn->code) == BPF_JMP)
> EMIT1(add_1mod(0x48, dst_reg));
> else if (is_ereg(dst_reg))
> --
> 2.20.1
>

Next message: Rodrigo Siqueira: "Re: Drop use of DRM_WAIT_ON() [Was: drm/drm_vblank: Change EINVAL by the correct errno]"
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Next in thread: Josh Poimboeuf: "Re: [PATCH 8/9] x86/bpf: Convert asm comments to AT&T syntax"
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