Skip to content

L
linux
Commit a2c7a983 authored by Ingo Molnar's avatar Ingo Molnar Committed by Daniel Borkmann
Browse files
Options

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: default avatarThomas 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: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent a3fe1f6f
Show whitespace changes
Inline Side-by-side
Showing with 133 additions and 100 deletions
arch/x86/net/bpf_jit_comp.c
View file @ a2c7a983
/* bpf_jit_comp.c : BPF JIT compiler /*
* bpf_jit_comp.c: BPF JIT compiler
* *
* Copyright (C) 2011-2013 Eric Dumazet (eric.dumazet@gmail.com) * Copyright (C) 2011-2013 Eric Dumazet (eric.dumazet@gmail.com)
* Internal BPF Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com * Internal BPF Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
...@@ -17,7 +18,7 @@ ...@@ -17,7 +18,7 @@
#include <asm/nospec-branch.h> #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[], sk_load_half[], sk_load_byte[];
extern u8 sk_load_word_positive_offset[], sk_load_half_positive_offset[]; 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) ...@@ -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 EMIT2(b1, b2) EMIT((b1) + ((b2) << 8), 2)
#define EMIT3(b1, b2, b3) EMIT((b1) + ((b2) << 8) + ((b3) << 16), 3) #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 EMIT4(b1, b2, b3, b4) EMIT((b1) + ((b2) << 8) + ((b3) << 16) + ((b4) << 24), 4)
#define EMIT1_off32(b1, off) \ #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) \ #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) \ #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) \ #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) static bool is_imm8(int value)
{ {
...@@ -71,7 +73,8 @@ static bool is_uimm32(u64 value) ...@@ -71,7 +73,8 @@ static bool is_uimm32(u64 value)
/* mov dst, src */ /* mov dst, src */
#define EMIT_mov(DST, SRC) \ #define EMIT_mov(DST, SRC) \
do {if (DST != SRC) \ do { \
if (DST != SRC) \
EMIT3(add_2mod(0x48, DST, SRC), 0x89, add_2reg(0xC0, DST, SRC)); \ EMIT3(add_2mod(0x48, DST, SRC), 0x89, add_2reg(0xC0, DST, SRC)); \
} while (0) } while (0)
...@@ -89,7 +92,8 @@ 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; 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) * Add 0x10 (and an extra 0x0f) to generate far jumps (. + s32)
*/ */
#define X86_JB 0x72 #define X86_JB 0x72
...@@ -106,35 +110,37 @@ static int bpf_size_to_x86_bytes(int bpf_size) ...@@ -106,35 +110,37 @@ static int bpf_size_to_x86_bytes(int bpf_size)
#define CHOOSE_LOAD_FUNC(K, func) \ #define CHOOSE_LOAD_FUNC(K, func) \
((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset) ((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) #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 * register in load/store instructions, it always needs an
* extra byte of encoding and is callee saved. * extra byte of encoding and is callee saved.
* *
* r9 caches skb->len - skb->data_len * R9 caches skb->len - skb->data_len
* r10 caches skb->data, and used for blinding (if enabled) * R10 caches skb->data, and used for blinding (if enabled)
*/ */
static const int reg2hex[] = { static const int reg2hex[] = {
[BPF_REG_0] = 0, /* rax */ [BPF_REG_0] = 0, /* RAX */
[BPF_REG_1] = 7, /* rdi */ [BPF_REG_1] = 7, /* RDI */
[BPF_REG_2] = 6, /* rsi */ [BPF_REG_2] = 6, /* RSI */
[BPF_REG_3] = 2, /* rdx */ [BPF_REG_3] = 2, /* RDX */
[BPF_REG_4] = 1, /* rcx */ [BPF_REG_4] = 1, /* RCX */
[BPF_REG_5] = 0, /* r8 */ [BPF_REG_5] = 0, /* R8 */
[BPF_REG_6] = 3, /* rbx callee saved */ [BPF_REG_6] = 3, /* RBX callee saved */
[BPF_REG_7] = 5, /* r13 callee saved */ [BPF_REG_7] = 5, /* R13 callee saved */
[BPF_REG_8] = 6, /* r14 callee saved */ [BPF_REG_8] = 6, /* R14 callee saved */
[BPF_REG_9] = 7, /* r15 callee saved */ [BPF_REG_9] = 7, /* R15 callee saved */
[BPF_REG_FP] = 5, /* rbp readonly */ [BPF_REG_FP] = 5, /* RBP readonly */
[BPF_REG_AX] = 2, /* r10 temp register */ [BPF_REG_AX] = 2, /* R10 temp register */
[AUX_REG] = 3, /* r11 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. * which need extra byte of encoding.
* rax,rcx,...,rbp have simpler encoding * rax,rcx,...,rbp have simpler encoding
*/ */
...@@ -153,7 +159,7 @@ static bool is_axreg(u32 reg) ...@@ -153,7 +159,7 @@ static bool is_axreg(u32 reg)
return reg == BPF_REG_0; 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) static u8 add_1mod(u8 byte, u32 reg)
{ {
if (is_ereg(reg)) if (is_ereg(reg))
...@@ -170,13 +176,13 @@ static u8 add_2mod(u8 byte, u32 r1, u32 r2) ...@@ -170,13 +176,13 @@ static u8 add_2mod(u8 byte, u32 r1, u32 r2)
return byte; 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) static u8 add_1reg(u8 byte, u32 dst_reg)
{ {
return byte + reg2hex[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) static u8 add_2reg(u8 byte, u32 dst_reg, u32 src_reg)
{ {
return byte + reg2hex[dst_reg] + (reg2hex[src_reg] << 3); 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) ...@@ -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) 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); memset(area, 0xcc, size);
} }
struct jit_context { struct jit_context {
int cleanup_addr; /* epilogue code offset */ int cleanup_addr; /* Epilogue code offset */
bool seen_ld_abs; bool seen_ld_abs;
bool seen_ax_reg; 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_MAX_INSN_SIZE 128
#define BPF_INSN_SAFETY 64 #define BPF_INSN_SAFETY 64
#define AUX_STACK_SPACE \ #define AUX_STACK_SPACE \
(32 /* space for rbx, r13, r14, r15 */ + \ (32 /* Space for RBX, R13, R14, R15 */ + \
8 /* space for skb_copy_bits() buffer */) 8 /* Space for skb_copy_bits() buffer */)
#define PROLOGUE_SIZE 37 #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 * 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) 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) ...@@ -212,8 +219,11 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf)
u8 *prog = *pprog; u8 *prog = *pprog;
int cnt = 0; int cnt = 0;
EMIT1(0x55); /* push rbp */ /* push rbp */
EMIT3(0x48, 0x89, 0xE5); /* mov rbp,rsp */ EMIT1(0x55);
/* mov rbp,rsp */
EMIT3(0x48, 0x89, 0xE5);
/* sub rsp, rounded_stack_depth + AUX_STACK_SPACE */ /* sub rsp, rounded_stack_depth + AUX_STACK_SPACE */
EMIT3_off32(0x48, 0x81, 0xEC, EMIT3_off32(0x48, 0x81, 0xEC,
...@@ -222,14 +232,15 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf) ...@@ -222,14 +232,15 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf)
/* sub rbp, AUX_STACK_SPACE */ /* sub rbp, AUX_STACK_SPACE */
EMIT4(0x48, 0x83, 0xED, 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 */ /* mov qword ptr [rbp+0],rbx */
EMIT4(0x48, 0x89, 0x5D, 0); 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 * bpf_convert_filter() maps classic BPF register X to R7 and uses R8
* R8(r14). R9(r15) spill could be made conditional, but there is only * 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 * one 'bpf_error' return path out of helper functions inside bpf_jit.S
* The overhead of extra spill is negligible for any filter other * The overhead of extra spill is negligible for any filter other
* than synthetic ones. Therefore not worth adding complexity. * 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) ...@@ -243,9 +254,10 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf)
EMIT4(0x4C, 0x89, 0x7D, 24); EMIT4(0x4C, 0x89, 0x7D, 24);
if (!ebpf_from_cbpf) { 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 * 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. * to the counter location.
*/ */
...@@ -260,7 +272,9 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf) ...@@ -260,7 +272,9 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf)
*pprog = prog; *pprog = prog;
} }
/* generate the following code: /*
* Generate the following code:
*
* ... bpf_tail_call(void *ctx, struct bpf_array *array, u64 index) ... * ... bpf_tail_call(void *ctx, struct bpf_array *array, u64 index) ...
* if (index >= array->map.max_entries) * if (index >= array->map.max_entries)
* goto out; * goto out;
...@@ -278,22 +292,25 @@ static void emit_bpf_tail_call(u8 **pprog) ...@@ -278,22 +292,25 @@ static void emit_bpf_tail_call(u8 **pprog)
int label1, label2, label3; int label1, label2, label3;
int cnt = 0; int cnt = 0;
/* rdi - pointer to ctx /*
* rdi - pointer to ctx
* rsi - pointer to bpf_array * rsi - pointer to bpf_array
* rdx - index in bpf_array * rdx - index in bpf_array
*/ */
/* if (index >= array->map.max_entries) /*
* if (index >= array->map.max_entries)
* goto out; * goto out;
*/ */
EMIT2(0x89, 0xD2); /* mov edx, edx */ EMIT2(0x89, 0xD2); /* mov edx, edx */
EMIT3(0x39, 0x56, /* cmp dword ptr [rsi + 16], edx */ EMIT3(0x39, 0x56, /* cmp dword ptr [rsi + 16], edx */
offsetof(struct bpf_array, map.max_entries)); 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 */ EMIT2(X86_JBE, OFFSET1); /* jbe out */
label1 = cnt; label1 = cnt;
/* if (tail_call_cnt > MAX_TAIL_CALL_CNT) /*
* if (tail_call_cnt > MAX_TAIL_CALL_CNT)
* goto out; * goto out;
*/ */
EMIT2_off32(0x8B, 0x85, 36); /* mov eax, dword ptr [rbp + 36] */ EMIT2_off32(0x8B, 0x85, 36); /* mov eax, dword ptr [rbp + 36] */
...@@ -308,7 +325,8 @@ static void emit_bpf_tail_call(u8 **pprog) ...@@ -308,7 +325,8 @@ static void emit_bpf_tail_call(u8 **pprog)
EMIT4_off32(0x48, 0x8B, 0x84, 0xD6, /* mov rax, [rsi + rdx * 8 + offsetof(...)] */ EMIT4_off32(0x48, 0x8B, 0x84, 0xD6, /* mov rax, [rsi + rdx * 8 + offsetof(...)] */
offsetof(struct bpf_array, ptrs)); offsetof(struct bpf_array, ptrs));
/* if (prog == NULL) /*
* if (prog == NULL)
* goto out; * goto out;
*/ */
EMIT3(0x48, 0x85, 0xC0); /* test rax,rax */ EMIT3(0x48, 0x85, 0xC0); /* test rax,rax */
...@@ -321,7 +339,8 @@ static void emit_bpf_tail_call(u8 **pprog) ...@@ -321,7 +339,8 @@ static void emit_bpf_tail_call(u8 **pprog)
offsetof(struct bpf_prog, bpf_func)); offsetof(struct bpf_prog, bpf_func));
EMIT4(0x48, 0x83, 0xC0, PROLOGUE_SIZE); /* add rax, prologue_size */ 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) * rdi == ctx (1st arg)
* rax == prog->bpf_func + prologue_size * rax == prog->bpf_func + prologue_size
*/ */
...@@ -340,7 +359,8 @@ static void emit_load_skb_data_hlen(u8 **pprog) ...@@ -340,7 +359,8 @@ static void emit_load_skb_data_hlen(u8 **pprog)
u8 *prog = *pprog; u8 *prog = *pprog;
int cnt = 0; int cnt = 0;
/* r9d = skb->len - skb->data_len (headlen) /*
* r9d = skb->len - skb->data_len (headlen)
* r10 = skb->data * r10 = skb->data
*/ */
/* mov %r9d, off32(%rdi) */ /* mov %r9d, off32(%rdi) */
...@@ -361,7 +381,8 @@ static void emit_mov_imm32(u8 **pprog, bool sign_propagate, ...@@ -361,7 +381,8 @@ static void emit_mov_imm32(u8 **pprog, bool sign_propagate,
u8 b1, b2, b3; u8 b1, b2, b3;
int cnt = 0; 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. * (which zero-extends imm32) to save 2 bytes.
*/ */
if (sign_propagate && (s32)imm32 < 0) { if (sign_propagate && (s32)imm32 < 0) {
...@@ -373,7 +394,8 @@ static void emit_mov_imm32(u8 **pprog, bool sign_propagate, ...@@ -373,7 +394,8 @@ static void emit_mov_imm32(u8 **pprog, bool sign_propagate,
goto done; goto done;
} }
/* optimization: if imm32 is zero, use 'xor %eax, %eax' /*
* Optimization: if imm32 is zero, use 'xor %eax, %eax'
* to save 3 bytes. * to save 3 bytes.
*/ */
if (imm32 == 0) { if (imm32 == 0) {
...@@ -400,7 +422,8 @@ static void emit_mov_imm64(u8 **pprog, u32 dst_reg, ...@@ -400,7 +422,8 @@ static void emit_mov_imm64(u8 **pprog, u32 dst_reg,
int cnt = 0; int cnt = 0;
if (is_uimm32(((u64)imm32_hi << 32) | (u32)imm32_lo)) { 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 * propagated LLVM tends to load imm64 over mov32
* directly, so save couple of bytes by just doing * directly, so save couple of bytes by just doing
* 'mov %eax, imm32' instead. * 'mov %eax, imm32' instead.
...@@ -525,7 +548,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, ...@@ -525,7 +548,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
else if (is_ereg(dst_reg)) else if (is_ereg(dst_reg))
EMIT1(add_1mod(0x40, 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. * in case dst is eax/rax.
*/ */
switch (BPF_OP(insn->code)) { switch (BPF_OP(insn->code)) {
...@@ -593,7 +617,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, ...@@ -593,7 +617,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
/* mov rax, dst_reg */ /* mov rax, dst_reg */
EMIT_mov(BPF_REG_0, dst_reg); EMIT_mov(BPF_REG_0, dst_reg);
/* xor edx, edx /*
* xor edx, edx
* equivalent to 'xor rdx, rdx', but one byte less * equivalent to 'xor rdx, rdx', but one byte less
*/ */
EMIT2(0x31, 0xd2); EMIT2(0x31, 0xd2);
...@@ -655,7 +680,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, ...@@ -655,7 +680,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
} }
break; break;
} }
/* shifts */ /* Shifts */
case BPF_ALU | BPF_LSH | BPF_K: case BPF_ALU | BPF_LSH | BPF_K:
case BPF_ALU | BPF_RSH | BPF_K: case BPF_ALU | BPF_RSH | BPF_K:
case BPF_ALU | BPF_ARSH | 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, ...@@ -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_RSH | BPF_X:
case BPF_ALU64 | BPF_ARSH | 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) { if (dst_reg == BPF_REG_4) {
/* mov r11, dst_reg */ /* mov r11, dst_reg */
EMIT_mov(AUX_REG, 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, ...@@ -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: case BPF_ALU | BPF_END | BPF_FROM_BE:
switch (imm32) { switch (imm32) {
case 16: case 16:
/* emit 'ror %ax, 8' to swap lower 2 bytes */ /* Emit 'ror %ax, 8' to swap lower 2 bytes */
EMIT1(0x66); EMIT1(0x66);
if (is_ereg(dst_reg)) if (is_ereg(dst_reg))
EMIT1(0x41); EMIT1(0x41);
EMIT3(0xC1, add_1reg(0xC8, dst_reg), 8); EMIT3(0xC1, add_1reg(0xC8, dst_reg), 8);
/* emit 'movzwl eax, ax' */ /* Emit 'movzwl eax, ax' */
if (is_ereg(dst_reg)) if (is_ereg(dst_reg))
EMIT3(0x45, 0x0F, 0xB7); EMIT3(0x45, 0x0F, 0xB7);
else else
...@@ -738,7 +763,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, ...@@ -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)); EMIT1(add_2reg(0xC0, dst_reg, dst_reg));
break; break;
case 32: case 32:
/* emit 'bswap eax' to swap lower 4 bytes */ /* Emit 'bswap eax' to swap lower 4 bytes */
if (is_ereg(dst_reg)) if (is_ereg(dst_reg))
EMIT2(0x41, 0x0F); EMIT2(0x41, 0x0F);
else else
...@@ -746,7 +771,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, ...@@ -746,7 +771,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
EMIT1(add_1reg(0xC8, dst_reg)); EMIT1(add_1reg(0xC8, dst_reg));
break; break;
case 64: case 64:
/* emit 'bswap rax' to swap 8 bytes */ /* Emit 'bswap rax' to swap 8 bytes */
EMIT3(add_1mod(0x48, dst_reg), 0x0F, EMIT3(add_1mod(0x48, dst_reg), 0x0F,
add_1reg(0xC8, dst_reg)); add_1reg(0xC8, dst_reg));
break; break;
...@@ -756,7 +781,8 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, ...@@ -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: case BPF_ALU | BPF_END | BPF_FROM_LE:
switch (imm32) { switch (imm32) {
case 16: case 16:
/* emit 'movzwl eax, ax' to zero extend 16-bit /*
* Emit 'movzwl eax, ax' to zero extend 16-bit
* into 64 bit * into 64 bit
*/ */
if (is_ereg(dst_reg)) if (is_ereg(dst_reg))
...@@ -766,7 +792,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, ...@@ -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)); EMIT1(add_2reg(0xC0, dst_reg, dst_reg));
break; break;
case 32: 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)) if (is_ereg(dst_reg))
EMIT1(0x45); EMIT1(0x45);
EMIT2(0x89, add_2reg(0xC0, dst_reg, dst_reg)); EMIT2(0x89, add_2reg(0xC0, dst_reg, dst_reg));
...@@ -809,9 +835,9 @@ st: if (is_imm8(insn->off)) ...@@ -809,9 +835,9 @@ st: if (is_imm8(insn->off))
/* STX: *(u8*)(dst_reg + off) = src_reg */ /* STX: *(u8*)(dst_reg + off) = src_reg */
case BPF_STX | BPF_MEM | BPF_B: 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) || 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) src_reg == BPF_REG_1 || src_reg == BPF_REG_2)
EMIT2(add_2mod(0x40, dst_reg, src_reg), 0x88); EMIT2(add_2mod(0x40, dst_reg, src_reg), 0x88);
else else
...@@ -840,25 +866,26 @@ stx: if (is_imm8(insn->off)) ...@@ -840,25 +866,26 @@ stx: if (is_imm8(insn->off))
/* LDX: dst_reg = *(u8*)(src_reg + off) */ /* LDX: dst_reg = *(u8*)(src_reg + off) */
case BPF_LDX | BPF_MEM | BPF_B: 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); EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xB6);
goto ldx; goto ldx;
case BPF_LDX | BPF_MEM | BPF_H: 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); EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xB7);
goto ldx; goto ldx;
case BPF_LDX | BPF_MEM | BPF_W: 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)) if (is_ereg(dst_reg) || is_ereg(src_reg))
EMIT2(add_2mod(0x40, src_reg, dst_reg), 0x8B); EMIT2(add_2mod(0x40, src_reg, dst_reg), 0x8B);
else else
EMIT1(0x8B); EMIT1(0x8B);
goto ldx; goto ldx;
case BPF_LDX | BPF_MEM | BPF_DW: 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); EMIT2(add_2mod(0x48, src_reg, dst_reg), 0x8B);
ldx: /* if insn->off == 0 we can save one extra byte, but ldx: /*
* special case of x86 r13 which always needs an offset * 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 * is not worth the hassle
*/ */
if (is_imm8(insn->off)) if (is_imm8(insn->off))
...@@ -870,7 +897,7 @@ stx: if (is_imm8(insn->off)) ...@@ -870,7 +897,7 @@ stx: if (is_imm8(insn->off))
/* STX XADD: lock *(u32*)(dst_reg + off) += src_reg */ /* STX XADD: lock *(u32*)(dst_reg + off) += src_reg */
case BPF_STX | BPF_XADD | BPF_W: 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)) if (is_ereg(dst_reg) || is_ereg(src_reg))
EMIT3(0xF0, add_2mod(0x40, dst_reg, src_reg), 0x01); EMIT3(0xF0, add_2mod(0x40, dst_reg, src_reg), 0x01);
else else
...@@ -897,14 +924,15 @@ xadd: if (is_imm8(insn->off)) ...@@ -897,14 +924,15 @@ xadd: if (is_imm8(insn->off))
} else { } else {
EMIT2(0x41, 0x52); /* push %r10 */ EMIT2(0x41, 0x52); /* push %r10 */
EMIT2(0x41, 0x51); /* push %r9 */ 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 * pop %r9, pop %r10 take 4 bytes after call insn
*/ */
jmp_offset += 4; jmp_offset += 4;
} }
} }
if (!imm32 || !is_simm32(jmp_offset)) { 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); imm32, func, image);
return -EINVAL; return -EINVAL;
} }
...@@ -970,7 +998,7 @@ xadd: if (is_imm8(insn->off)) ...@@ -970,7 +998,7 @@ xadd: if (is_imm8(insn->off))
else else
EMIT2_off32(0x81, add_1reg(0xF8, dst_reg), imm32); 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)) { switch (BPF_OP(insn->code)) {
case BPF_JEQ: case BPF_JEQ:
jmp_cond = X86_JE; jmp_cond = X86_JE;
...@@ -996,22 +1024,22 @@ xadd: if (is_imm8(insn->off)) ...@@ -996,22 +1024,22 @@ xadd: if (is_imm8(insn->off))
jmp_cond = X86_JBE; jmp_cond = X86_JBE;
break; break;
case BPF_JSGT: case BPF_JSGT:
/* signed '>', GT in x86 */ /* Signed '>', GT in x86 */
jmp_cond = X86_JG; jmp_cond = X86_JG;
break; break;
case BPF_JSLT: case BPF_JSLT:
/* signed '<', LT in x86 */ /* Signed '<', LT in x86 */
jmp_cond = X86_JL; jmp_cond = X86_JL;
break; break;
case BPF_JSGE: case BPF_JSGE:
/* signed '>=', GE in x86 */ /* Signed '>=', GE in x86 */
jmp_cond = X86_JGE; jmp_cond = X86_JGE;
break; break;
case BPF_JSLE: case BPF_JSLE:
/* signed '<=', LE in x86 */ /* Signed '<=', LE in x86 */
jmp_cond = X86_JLE; jmp_cond = X86_JLE;
break; break;
default: /* to silence gcc warning */ default: /* to silence GCC warning */
return -EFAULT; return -EFAULT;
} }
jmp_offset = addrs[i + insn->off] - addrs[i]; jmp_offset = addrs[i + insn->off] - addrs[i];
...@@ -1039,7 +1067,7 @@ xadd: if (is_imm8(insn->off)) ...@@ -1039,7 +1067,7 @@ xadd: if (is_imm8(insn->off))
jmp_offset = addrs[i + insn->off] - addrs[i]; jmp_offset = addrs[i + insn->off] - addrs[i];
if (!jmp_offset) if (!jmp_offset)
/* optimize out nop jumps */ /* Optimize out nop jumps */
break; break;
emit_jmp: emit_jmp:
if (is_imm8(jmp_offset)) { if (is_imm8(jmp_offset)) {
...@@ -1061,7 +1089,7 @@ xadd: if (is_imm8(insn->off)) ...@@ -1061,7 +1089,7 @@ xadd: if (is_imm8(insn->off))
ctx->seen_ld_abs = seen_ld_abs = true; ctx->seen_ld_abs = seen_ld_abs = true;
jmp_offset = func - (image + addrs[i]); jmp_offset = func - (image + addrs[i]);
if (!func || !is_simm32(jmp_offset)) { 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); imm32, func, image);
return -EINVAL; return -EINVAL;
} }
...@@ -1080,7 +1108,8 @@ xadd: if (is_imm8(insn->off)) ...@@ -1080,7 +1108,8 @@ xadd: if (is_imm8(insn->off))
EMIT2_off32(0x81, 0xC6, imm32); 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. * %rdi if skb_copy_bits() call is necessary.
* sk_load_* helpers also use %r10 and %r9d. * sk_load_* helpers also use %r10 and %r9d.
* See bpf_jit.S * See bpf_jit.S
...@@ -1111,7 +1140,7 @@ xadd: if (is_imm8(insn->off)) ...@@ -1111,7 +1140,7 @@ xadd: if (is_imm8(insn->off))
goto emit_jmp; goto emit_jmp;
} }
seen_exit = true; seen_exit = true;
/* update cleanup_addr */ /* Update cleanup_addr */
ctx->cleanup_addr = proglen; ctx->cleanup_addr = proglen;
/* mov rbx, qword ptr [rbp+0] */ /* mov rbx, qword ptr [rbp+0] */
EMIT4(0x48, 0x8B, 0x5D, 0); EMIT4(0x48, 0x8B, 0x5D, 0);
...@@ -1129,10 +1158,11 @@ xadd: if (is_imm8(insn->off)) ...@@ -1129,10 +1158,11 @@ xadd: if (is_imm8(insn->off))
break; break;
default: 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 * This error will be seen if new instruction was added
* to interpreter, but not to JIT * to the interpreter, but not to the JIT, or if there is
* or if there is junk in bpf_prog * junk in bpf_prog.
*/ */
pr_err("bpf_jit: unknown opcode %02x\n", insn->code); pr_err("bpf_jit: unknown opcode %02x\n", insn->code);
return -EINVAL; return -EINVAL;
...@@ -1184,7 +1214,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) ...@@ -1184,7 +1214,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
return orig_prog; return orig_prog;
tmp = bpf_jit_blind_constants(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. * we must fall back to the interpreter.
*/ */
if (IS_ERR(tmp)) if (IS_ERR(tmp))
...@@ -1218,8 +1249,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) ...@@ -1218,8 +1249,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
goto out_addrs; 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++) { for (proglen = 0, i = 0; i < prog->len; i++) {
proglen += 64; proglen += 64;
...@@ -1228,10 +1260,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) ...@@ -1228,10 +1260,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
ctx.cleanup_addr = proglen; ctx.cleanup_addr = proglen;
skip_init_addrs: 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 * 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++) { for (pass = 0; pass < 20 || image; pass++) {
proglen = do_jit(prog, addrs, image, oldproglen, &ctx); proglen = do_jit(prog, addrs, image, oldproglen, &ctx);
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7