-/* 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
#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[];
#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)
{
}
/* 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)
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
#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
*/
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))
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);
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)
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,
/* 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.
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.
*/
*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;
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 */
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)
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
*/
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) */
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) {
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) {
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.
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)) {
/* 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);
}
break;
}
- /* shifts */
+ /* Shifts */
case BPF_ALU | BPF_LSH | BPF_K:
case BPF_ALU | BPF_RSH | BPF_K:
case BPF_ALU | BPF_ARSH | BPF_K:
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);
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
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
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;
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))
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));
/* 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
/* 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))
/* 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
} 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;
}
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;
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];
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)) {
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;
}
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
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);
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;
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))
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;
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);
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