diff options
author | Ingo Molnar <mingo@kernel.org> | 2018-04-27 12:54:40 +0300 |
---|---|---|
committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-05-02 17:12:02 +0300 |
commit | a2c7a98301d9f9bcfc4244de04252a04c0b68a79 (patch) | |
tree | b3dc9b67f2dd5e08acabf2ade847d36536791115 /arch/x86 | |
parent | a3fe1f6f2adaa01c620793666d489a584211ecba (diff) | |
download | linux-a2c7a98301d9f9bcfc4244de04252a04c0b68a79.tar.xz |
x86/bpf: Clean up non-standard comments, to make the code more readable
So by chance I looked into x86 assembly in arch/x86/net/bpf_jit_comp.c and
noticed the weird and inconsistent comment style it mistakenly learned from
the networking code:
/* Multi-line comment ...
* ... looks like this.
*/
Fix this to use the standard comment style specified in Documentation/CodingStyle
and used in arch/x86/ as well:
/*
* Multi-line comment ...
* ... looks like this.
*/
Also, to quote Linus's ... more explicit views about this:
http://article.gmane.org/gmane.linux.kernel.cryptoapi/21066
> But no, the networking code picked *none* of the above sane formats.
> Instead, it picked these two models that are just half-arsed
> shit-for-brains:
>
> (no)
> /* This is disgusting drug-induced
> * crap, and should die
> */
>
> (no-no-no)
> /* This is also very nasty
> * and visually unbalanced */
>
> Please. The networking code actually has the *worst* possible comment
> style. You can literally find that (no-no-no) style, which is just
> really horribly disgusting and worse than the otherwise fairly similar
> (d) in pretty much every way.
Also improve the comments and some other details while at it:
- Don't mix same-line and previous-line comment style on otherwise
identical code patterns within the same function,
- capitalize 'BPF' and x86 register names consistently,
- capitalize sentences consistently,
- instead of 'x64' use 'x86-64': x64 is a Microsoft specific term,
- use more consistent punctuation,
- use standard coding style in macros as well,
- fix typos and a few other minor details.
Consistent coding style is not optional, at least in arch/x86/.
No change in functionality.
( In case this commit causes conflicts with pending development code
I'll be glad to help resolve any conflicts! )
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'arch/x86')
-rw-r--r-- | arch/x86/net/bpf_jit_comp.c | 233 |
1 files changed, 133 insertions, 100 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index abce27ceb411..1c3c81ddeb87 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1,4 +1,5 @@ -/* bpf_jit_comp.c : BPF JIT compiler +/* + * bpf_jit_comp.c: BPF JIT compiler * * Copyright (C) 2011-2013 Eric Dumazet (eric.dumazet@gmail.com) * Internal BPF Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com @@ -17,7 +18,7 @@ #include <asm/nospec-branch.h> /* - * assembly code in arch/x86/net/bpf_jit.S + * Assembly code in arch/x86/net/bpf_jit.S */ extern u8 sk_load_word[], sk_load_half[], sk_load_byte[]; extern u8 sk_load_word_positive_offset[], sk_load_half_positive_offset[]; @@ -45,14 +46,15 @@ static u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len) #define EMIT2(b1, b2) EMIT((b1) + ((b2) << 8), 2) #define EMIT3(b1, b2, b3) EMIT((b1) + ((b2) << 8) + ((b3) << 16), 3) #define EMIT4(b1, b2, b3, b4) EMIT((b1) + ((b2) << 8) + ((b3) << 16) + ((b4) << 24), 4) + #define EMIT1_off32(b1, off) \ - do {EMIT1(b1); EMIT(off, 4); } while (0) + do { EMIT1(b1); EMIT(off, 4); } while (0) #define EMIT2_off32(b1, b2, off) \ - do {EMIT2(b1, b2); EMIT(off, 4); } while (0) + do { EMIT2(b1, b2); EMIT(off, 4); } while (0) #define EMIT3_off32(b1, b2, b3, off) \ - do {EMIT3(b1, b2, b3); EMIT(off, 4); } while (0) + do { EMIT3(b1, b2, b3); EMIT(off, 4); } while (0) #define EMIT4_off32(b1, b2, b3, b4, off) \ - do {EMIT4(b1, b2, b3, b4); EMIT(off, 4); } while (0) + do { EMIT4(b1, b2, b3, b4); EMIT(off, 4); } while (0) static bool is_imm8(int value) { @@ -70,9 +72,10 @@ static bool is_uimm32(u64 value) } /* mov dst, src */ -#define EMIT_mov(DST, SRC) \ - do {if (DST != SRC) \ - EMIT3(add_2mod(0x48, DST, SRC), 0x89, add_2reg(0xC0, DST, SRC)); \ +#define EMIT_mov(DST, SRC) \ + do { \ + if (DST != SRC) \ + EMIT3(add_2mod(0x48, DST, SRC), 0x89, add_2reg(0xC0, DST, SRC)); \ } while (0) static int bpf_size_to_x86_bytes(int bpf_size) @@ -89,7 +92,8 @@ static int bpf_size_to_x86_bytes(int bpf_size) return 0; } -/* list of x86 cond jumps opcodes (. + s8) +/* + * List of x86 cond jumps opcodes (. + s8) * Add 0x10 (and an extra 0x0f) to generate far jumps (. + s32) */ #define X86_JB 0x72 @@ -106,35 +110,37 @@ static int bpf_size_to_x86_bytes(int bpf_size) #define CHOOSE_LOAD_FUNC(K, func) \ ((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset) -/* pick a register outside of BPF range for JIT internal work */ +/* Pick a register outside of BPF range for JIT internal work */ #define AUX_REG (MAX_BPF_JIT_REG + 1) -/* The following table maps BPF registers to x64 registers. +/* + * The following table maps BPF registers to x86-64 registers. * - * x64 register r12 is unused, since if used as base address + * x86-64 register R12 is unused, since if used as base address * register in load/store instructions, it always needs an * extra byte of encoding and is callee saved. * - * r9 caches skb->len - skb->data_len - * r10 caches skb->data, and used for blinding (if enabled) + * R9 caches skb->len - skb->data_len + * R10 caches skb->data, and used for blinding (if enabled) */ static const int reg2hex[] = { - [BPF_REG_0] = 0, /* rax */ - [BPF_REG_1] = 7, /* rdi */ - [BPF_REG_2] = 6, /* rsi */ - [BPF_REG_3] = 2, /* rdx */ - [BPF_REG_4] = 1, /* rcx */ - [BPF_REG_5] = 0, /* r8 */ - [BPF_REG_6] = 3, /* rbx callee saved */ - [BPF_REG_7] = 5, /* r13 callee saved */ - [BPF_REG_8] = 6, /* r14 callee saved */ - [BPF_REG_9] = 7, /* r15 callee saved */ - [BPF_REG_FP] = 5, /* rbp readonly */ - [BPF_REG_AX] = 2, /* r10 temp register */ - [AUX_REG] = 3, /* r11 temp register */ + [BPF_REG_0] = 0, /* RAX */ + [BPF_REG_1] = 7, /* RDI */ + [BPF_REG_2] = 6, /* RSI */ + [BPF_REG_3] = 2, /* RDX */ + [BPF_REG_4] = 1, /* RCX */ + [BPF_REG_5] = 0, /* R8 */ + [BPF_REG_6] = 3, /* RBX callee saved */ + [BPF_REG_7] = 5, /* R13 callee saved */ + [BPF_REG_8] = 6, /* R14 callee saved */ + [BPF_REG_9] = 7, /* R15 callee saved */ + [BPF_REG_FP] = 5, /* RBP readonly */ + [BPF_REG_AX] = 2, /* R10 temp register */ + [AUX_REG] = 3, /* R11 temp register */ }; -/* is_ereg() == true if BPF register 'reg' maps to x64 r8..r15 +/* + * is_ereg() == true if BPF register 'reg' maps to x86-64 r8..r15 * which need extra byte of encoding. * rax,rcx,...,rbp have simpler encoding */ @@ -153,7 +159,7 @@ static bool is_axreg(u32 reg) return reg == BPF_REG_0; } -/* add modifiers if 'reg' maps to x64 registers r8..r15 */ +/* Add modifiers if 'reg' maps to x86-64 registers R8..R15 */ static u8 add_1mod(u8 byte, u32 reg) { if (is_ereg(reg)) @@ -170,13 +176,13 @@ static u8 add_2mod(u8 byte, u32 r1, u32 r2) return byte; } -/* encode 'dst_reg' register into x64 opcode 'byte' */ +/* Encode 'dst_reg' register into x86-64 opcode 'byte' */ static u8 add_1reg(u8 byte, u32 dst_reg) { return byte + reg2hex[dst_reg]; } -/* encode 'dst_reg' and 'src_reg' registers into x64 opcode 'byte' */ +/* Encode 'dst_reg' and 'src_reg' registers into x86-64 opcode 'byte' */ static u8 add_2reg(u8 byte, u32 dst_reg, u32 src_reg) { return byte + reg2hex[dst_reg] + (reg2hex[src_reg] << 3); @@ -184,27 +190,28 @@ static u8 add_2reg(u8 byte, u32 dst_reg, u32 src_reg) static void jit_fill_hole(void *area, unsigned int size) { - /* fill whole space with int3 instructions */ + /* Fill whole space with INT3 instructions */ memset(area, 0xcc, size); } struct jit_context { - int cleanup_addr; /* epilogue code offset */ + int cleanup_addr; /* Epilogue code offset */ bool seen_ld_abs; bool seen_ax_reg; }; -/* maximum number of bytes emitted while JITing one eBPF insn */ +/* Maximum number of bytes emitted while JITing one eBPF insn */ #define BPF_MAX_INSN_SIZE 128 #define BPF_INSN_SAFETY 64 #define AUX_STACK_SPACE \ - (32 /* space for rbx, r13, r14, r15 */ + \ - 8 /* space for skb_copy_bits() buffer */) + (32 /* Space for RBX, R13, R14, R15 */ + \ + 8 /* Space for skb_copy_bits() buffer */) #define PROLOGUE_SIZE 37 -/* emit x64 prologue code for BPF program and check it's size. +/* + * Emit x86-64 prologue code for BPF program and check its size. * bpf_tail_call helper will skip it while jumping into another program */ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf) @@ -212,8 +219,11 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf) u8 *prog = *pprog; int cnt = 0; - EMIT1(0x55); /* push rbp */ - EMIT3(0x48, 0x89, 0xE5); /* mov rbp,rsp */ + /* push rbp */ + EMIT1(0x55); + + /* mov rbp,rsp */ + EMIT3(0x48, 0x89, 0xE5); /* sub rsp, rounded_stack_depth + AUX_STACK_SPACE */ EMIT3_off32(0x48, 0x81, 0xEC, @@ -222,14 +232,15 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf) /* sub rbp, AUX_STACK_SPACE */ EMIT4(0x48, 0x83, 0xED, AUX_STACK_SPACE); - /* all classic BPF filters use R6(rbx) save it */ + /* All classic BPF filters use R6(rbx) save it */ /* mov qword ptr [rbp+0],rbx */ EMIT4(0x48, 0x89, 0x5D, 0); - /* bpf_convert_filter() maps classic BPF register X to R7 and uses R8 - * as temporary, so all tcpdump filters need to spill/fill R7(r13) and - * R8(r14). R9(r15) spill could be made conditional, but there is only + /* + * bpf_convert_filter() maps classic BPF register X to R7 and uses R8 + * as temporary, so all tcpdump filters need to spill/fill R7(R13) and + * R8(R14). R9(R15) spill could be made conditional, but there is only * one 'bpf_error' return path out of helper functions inside bpf_jit.S * The overhead of extra spill is negligible for any filter other * than synthetic ones. Therefore not worth adding complexity. @@ -243,9 +254,10 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf) EMIT4(0x4C, 0x89, 0x7D, 24); if (!ebpf_from_cbpf) { - /* Clear the tail call counter (tail_call_cnt): for eBPF tail + /* + * Clear the tail call counter (tail_call_cnt): for eBPF tail * calls we need to reset the counter to 0. It's done in two - * instructions, resetting rax register to 0, and moving it + * instructions, resetting RAX register to 0, and moving it * to the counter location. */ @@ -260,7 +272,9 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf) *pprog = prog; } -/* generate the following code: +/* + * Generate the following code: + * * ... bpf_tail_call(void *ctx, struct bpf_array *array, u64 index) ... * if (index >= array->map.max_entries) * goto out; @@ -278,23 +292,26 @@ static void emit_bpf_tail_call(u8 **pprog) int label1, label2, label3; int cnt = 0; - /* rdi - pointer to ctx + /* + * rdi - pointer to ctx * rsi - pointer to bpf_array * rdx - index in bpf_array */ - /* if (index >= array->map.max_entries) - * goto out; + /* + * if (index >= array->map.max_entries) + * goto out; */ EMIT2(0x89, 0xD2); /* mov edx, edx */ EMIT3(0x39, 0x56, /* cmp dword ptr [rsi + 16], edx */ offsetof(struct bpf_array, map.max_entries)); -#define OFFSET1 (41 + RETPOLINE_RAX_BPF_JIT_SIZE) /* number of bytes to jump */ +#define OFFSET1 (41 + RETPOLINE_RAX_BPF_JIT_SIZE) /* Number of bytes to jump */ EMIT2(X86_JBE, OFFSET1); /* jbe out */ label1 = cnt; - /* if (tail_call_cnt > MAX_TAIL_CALL_CNT) - * goto out; + /* + * if (tail_call_cnt > MAX_TAIL_CALL_CNT) + * goto out; */ EMIT2_off32(0x8B, 0x85, 36); /* mov eax, dword ptr [rbp + 36] */ EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp eax, MAX_TAIL_CALL_CNT */ @@ -308,8 +325,9 @@ static void emit_bpf_tail_call(u8 **pprog) EMIT4_off32(0x48, 0x8B, 0x84, 0xD6, /* mov rax, [rsi + rdx * 8 + offsetof(...)] */ offsetof(struct bpf_array, ptrs)); - /* if (prog == NULL) - * goto out; + /* + * if (prog == NULL) + * goto out; */ EMIT3(0x48, 0x85, 0xC0); /* test rax,rax */ #define OFFSET3 (8 + RETPOLINE_RAX_BPF_JIT_SIZE) @@ -321,7 +339,8 @@ static void emit_bpf_tail_call(u8 **pprog) offsetof(struct bpf_prog, bpf_func)); EMIT4(0x48, 0x83, 0xC0, PROLOGUE_SIZE); /* add rax, prologue_size */ - /* now we're ready to jump into next BPF program + /* + * Wow we're ready to jump into next BPF program * rdi == ctx (1st arg) * rax == prog->bpf_func + prologue_size */ @@ -340,7 +359,8 @@ static void emit_load_skb_data_hlen(u8 **pprog) u8 *prog = *pprog; int cnt = 0; - /* r9d = skb->len - skb->data_len (headlen) + /* + * r9d = skb->len - skb->data_len (headlen) * r10 = skb->data */ /* mov %r9d, off32(%rdi) */ @@ -361,7 +381,8 @@ static void emit_mov_imm32(u8 **pprog, bool sign_propagate, u8 b1, b2, b3; int cnt = 0; - /* optimization: if imm32 is positive, use 'mov %eax, imm32' + /* + * Optimization: if imm32 is positive, use 'mov %eax, imm32' * (which zero-extends imm32) to save 2 bytes. */ if (sign_propagate && (s32)imm32 < 0) { @@ -373,7 +394,8 @@ static void emit_mov_imm32(u8 **pprog, bool sign_propagate, goto done; } - /* optimization: if imm32 is zero, use 'xor %eax, %eax' + /* + * Optimization: if imm32 is zero, use 'xor %eax, %eax' * to save 3 bytes. */ if (imm32 == 0) { @@ -400,7 +422,8 @@ static void emit_mov_imm64(u8 **pprog, u32 dst_reg, int cnt = 0; if (is_uimm32(((u64)imm32_hi << 32) | (u32)imm32_lo)) { - /* For emitting plain u32, where sign bit must not be + /* + * 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. @@ -525,7 +548,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, else if (is_ereg(dst_reg)) EMIT1(add_1mod(0x40, dst_reg)); - /* b3 holds 'normal' opcode, b2 short form only valid + /* + * b3 holds 'normal' opcode, b2 short form only valid * in case dst is eax/rax. */ switch (BPF_OP(insn->code)) { @@ -593,7 +617,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, /* mov rax, dst_reg */ EMIT_mov(BPF_REG_0, dst_reg); - /* xor edx, edx + /* + * xor edx, edx * equivalent to 'xor rdx, rdx', but one byte less */ EMIT2(0x31, 0xd2); @@ -655,7 +680,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, } break; } - /* shifts */ + /* Shifts */ case BPF_ALU | BPF_LSH | BPF_K: case BPF_ALU | BPF_RSH | BPF_K: case BPF_ALU | BPF_ARSH | BPF_K: @@ -686,7 +711,7 @@ 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 */ EMIT_mov(AUX_REG, dst_reg); @@ -724,13 +749,13 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, case BPF_ALU | BPF_END | BPF_FROM_BE: switch (imm32) { case 16: - /* emit 'ror %ax, 8' to swap lower 2 bytes */ + /* Emit 'ror %ax, 8' 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 eax, ax' */ if (is_ereg(dst_reg)) EMIT3(0x45, 0x0F, 0xB7); else @@ -738,7 +763,7 @@ 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 @@ -746,7 +771,7 @@ 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; @@ -756,7 +781,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, case BPF_ALU | BPF_END | BPF_FROM_LE: switch (imm32) { case 16: - /* emit 'movzwl eax, ax' to zero extend 16-bit + /* + * Emit 'movzwl eax, ax' to zero extend 16-bit * into 64 bit */ if (is_ereg(dst_reg)) @@ -766,7 +792,7 @@ 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)); @@ -809,9 +835,9 @@ st: if (is_imm8(insn->off)) /* STX: *(u8*)(dst_reg + off) = src_reg */ case BPF_STX | BPF_MEM | BPF_B: - /* emit 'mov byte ptr [rax + off], al' */ + /* Emit 'mov byte ptr [rax + off], al' */ if (is_ereg(dst_reg) || is_ereg(src_reg) || - /* have to add extra byte for x86 SIL, DIL regs */ + /* We have to add extra byte for x86 SIL, DIL regs */ src_reg == BPF_REG_1 || src_reg == BPF_REG_2) EMIT2(add_2mod(0x40, dst_reg, src_reg), 0x88); else @@ -840,25 +866,26 @@ stx: if (is_imm8(insn->off)) /* LDX: dst_reg = *(u8*)(src_reg + off) */ case BPF_LDX | BPF_MEM | BPF_B: - /* emit 'movzx rax, byte ptr [rax + off]' */ + /* Emit 'movzx rax, byte ptr [rax + off]' */ 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 'movzx rax, word ptr [rax + off]' */ 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 eax, dword ptr [rax+0x14]' */ 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 rax, qword ptr [rax+0x14]' */ EMIT2(add_2mod(0x48, src_reg, dst_reg), 0x8B); -ldx: /* if insn->off == 0 we can save one extra byte, but - * special case of x86 r13 which always needs an offset +ldx: /* + * If insn->off == 0 we can save one extra byte, but + * special case of x86 R13 which always needs an offset * is not worth the hassle */ if (is_imm8(insn->off)) @@ -870,7 +897,7 @@ ldx: /* if insn->off == 0 we can save one extra byte, but /* 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 dword ptr [rax + off], eax' */ if (is_ereg(dst_reg) || is_ereg(src_reg)) EMIT3(0xF0, add_2mod(0x40, dst_reg, src_reg), 0x01); else @@ -897,14 +924,15 @@ xadd: if (is_imm8(insn->off)) } else { EMIT2(0x41, 0x52); /* push %r10 */ EMIT2(0x41, 0x51); /* push %r9 */ - /* need to adjust jmp offset, since + /* + * We need to adjust jmp offset, since * pop %r9, pop %r10 take 4 bytes after call insn */ jmp_offset += 4; } } if (!imm32 || !is_simm32(jmp_offset)) { - pr_err("unsupported bpf func %d addr %p image %p\n", + pr_err("unsupported BPF func %d addr %p image %p\n", imm32, func, image); return -EINVAL; } @@ -970,7 +998,7 @@ xadd: if (is_imm8(insn->off)) else EMIT2_off32(0x81, add_1reg(0xF8, dst_reg), imm32); -emit_cond_jmp: /* convert BPF opcode to x86 */ +emit_cond_jmp: /* Convert BPF opcode to x86 */ switch (BPF_OP(insn->code)) { case BPF_JEQ: jmp_cond = X86_JE; @@ -996,22 +1024,22 @@ emit_cond_jmp: /* convert BPF opcode to x86 */ jmp_cond = X86_JBE; break; case BPF_JSGT: - /* signed '>', GT in x86 */ + /* Signed '>', GT in x86 */ jmp_cond = X86_JG; break; case BPF_JSLT: - /* signed '<', LT in x86 */ + /* Signed '<', LT in x86 */ jmp_cond = X86_JL; break; case BPF_JSGE: - /* signed '>=', GE in x86 */ + /* Signed '>=', GE in x86 */ jmp_cond = X86_JGE; break; case BPF_JSLE: - /* signed '<=', LE in x86 */ + /* Signed '<=', LE in x86 */ jmp_cond = X86_JLE; break; - default: /* to silence gcc warning */ + default: /* to silence GCC warning */ return -EFAULT; } jmp_offset = addrs[i + insn->off] - addrs[i]; @@ -1039,7 +1067,7 @@ emit_cond_jmp: /* convert BPF opcode to x86 */ jmp_offset = addrs[i + insn->off] - addrs[i]; if (!jmp_offset) - /* optimize out nop jumps */ + /* Optimize out nop jumps */ break; emit_jmp: if (is_imm8(jmp_offset)) { @@ -1061,7 +1089,7 @@ common_load: ctx->seen_ld_abs = seen_ld_abs = true; jmp_offset = func - (image + addrs[i]); if (!func || !is_simm32(jmp_offset)) { - pr_err("unsupported bpf func %d addr %p image %p\n", + pr_err("unsupported BPF func %d addr %p image %p\n", imm32, func, image); return -EINVAL; } @@ -1080,7 +1108,8 @@ common_load: EMIT2_off32(0x81, 0xC6, imm32); } } - /* skb pointer is in R6 (%rbx), it will be copied into + /* + * skb pointer is in R6 (%rbx), it will be copied into * %rdi if skb_copy_bits() call is necessary. * sk_load_* helpers also use %r10 and %r9d. * See bpf_jit.S @@ -1111,7 +1140,7 @@ common_load: goto emit_jmp; } seen_exit = true; - /* update cleanup_addr */ + /* Update cleanup_addr */ ctx->cleanup_addr = proglen; /* mov rbx, qword ptr [rbp+0] */ EMIT4(0x48, 0x8B, 0x5D, 0); @@ -1129,10 +1158,11 @@ common_load: break; default: - /* By design x64 JIT should support all BPF instructions + /* + * By design x86-64 JIT should support all BPF instructions. * This error will be seen if new instruction was added - * to interpreter, but not to JIT - * or if there is junk in bpf_prog + * to the interpreter, but not to the JIT, or if there is + * junk in bpf_prog. */ pr_err("bpf_jit: unknown opcode %02x\n", insn->code); return -EINVAL; @@ -1184,7 +1214,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) return orig_prog; tmp = bpf_jit_blind_constants(prog); - /* If blinding was requested and we failed during blinding, + /* + * If blinding was requested and we failed during blinding, * we must fall back to the interpreter. */ if (IS_ERR(tmp)) @@ -1218,8 +1249,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) goto out_addrs; } - /* Before first pass, make a rough estimation of addrs[] - * each bpf instruction is translated to less than 64 bytes + /* + * Before first pass, make a rough estimation of addrs[] + * each BPF instruction is translated to less than 64 bytes */ for (proglen = 0, i = 0; i < prog->len; i++) { proglen += 64; @@ -1228,10 +1260,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) ctx.cleanup_addr = proglen; skip_init_addrs: - /* JITed image shrinks with every pass and the loop iterates - * until the image stops shrinking. Very large bpf programs + /* + * JITed image shrinks with every pass and the loop iterates + * until the image stops shrinking. Very large BPF programs * may converge on the last pass. In such case do one more - * pass to emit the final image + * pass to emit the final image. */ for (pass = 0; pass < 20 || image; pass++) { proglen = do_jit(prog, addrs, image, oldproglen, &ctx); |