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bpf_jit_comp.c
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// SPDX-License-Identifier: GPL-2.0-only
/*
* BPF JIT compiler
*
* Copyright (C) 2011-2013 Eric Dumazet ([email protected])
* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
*/
#include <linux/netdevice.h>
#include <linux/filter.h>
#include <linux/if_vlan.h>
#include <linux/bpf.h>
#include <linux/memory.h>
#include <linux/sort.h>
#include <asm/extable.h>
#include <asm/set_memory.h>
#include <asm/nospec-branch.h>
#include <asm/text-patching.h>
static u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len)
{
if (len == 1)
*ptr = bytes;
else if (len == 2)
*(u16 *)ptr = bytes;
else {
*(u32 *)ptr = bytes;
barrier();
}
return ptr + len;
}
#define EMIT(bytes, len) \
do { prog = emit_code(prog, bytes, len); } while (0)
#define EMIT1(b1) EMIT(b1, 1)
#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)
#define EMIT2_off32(b1, b2, off) \
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)
#define EMIT4_off32(b1, b2, b3, b4, off) \
do { EMIT4(b1, b2, b3, b4); EMIT(off, 4); } while (0)
#ifdef CONFIG_X86_KERNEL_IBT
#define EMIT_ENDBR() EMIT(gen_endbr(), 4)
#else
#define EMIT_ENDBR()
#endif
static bool is_imm8(int value)
{
return value <= 127 && value >= -128;
}
static bool is_simm32(s64 value)
{
return value == (s64)(s32)value;
}
static bool is_uimm32(u64 value)
{
return value == (u64)(u32)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)); \
} while (0)
static int bpf_size_to_x86_bytes(int bpf_size)
{
if (bpf_size == BPF_W)
return 4;
else if (bpf_size == BPF_H)
return 2;
else if (bpf_size == BPF_B)
return 1;
else if (bpf_size == BPF_DW)
return 4; /* imm32 */
else
return 0;
}
/*
* List of x86 cond jumps opcodes (. + s8)
* Add 0x10 (and an extra 0x0f) to generate far jumps (. + s32)
*/
#define X86_JB 0x72
#define X86_JAE 0x73
#define X86_JE 0x74
#define X86_JNE 0x75
#define X86_JBE 0x76
#define X86_JA 0x77
#define X86_JL 0x7C
#define X86_JGE 0x7D
#define X86_JLE 0x7E
#define X86_JG 0x7F
/* Pick a register outside of BPF range for JIT internal work */
#define AUX_REG (MAX_BPF_JIT_REG + 1)
#define X86_REG_R9 (MAX_BPF_JIT_REG + 2)
/*
* The following table maps BPF registers to x86-64 registers.
*
* 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.
*
* x86-64 register R9 is not used by BPF programs, but can be used by BPF
* trampoline. x86-64 register R10 is 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 */
[X86_REG_R9] = 1, /* R9 register, 6th function argument */
};
static const int reg2pt_regs[] = {
[BPF_REG_0] = offsetof(struct pt_regs, ax),
[BPF_REG_1] = offsetof(struct pt_regs, di),
[BPF_REG_2] = offsetof(struct pt_regs, si),
[BPF_REG_3] = offsetof(struct pt_regs, dx),
[BPF_REG_4] = offsetof(struct pt_regs, cx),
[BPF_REG_5] = offsetof(struct pt_regs, r8),
[BPF_REG_6] = offsetof(struct pt_regs, bx),
[BPF_REG_7] = offsetof(struct pt_regs, r13),
[BPF_REG_8] = offsetof(struct pt_regs, r14),
[BPF_REG_9] = offsetof(struct pt_regs, 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
*/
static bool is_ereg(u32 reg)
{
return (1 << reg) & (BIT(BPF_REG_5) |
BIT(AUX_REG) |
BIT(BPF_REG_7) |
BIT(BPF_REG_8) |
BIT(BPF_REG_9) |
BIT(X86_REG_R9) |
BIT(BPF_REG_AX));
}
/*
* is_ereg_8l() == true if BPF register 'reg' is mapped to access x86-64
* lower 8-bit registers dil,sil,bpl,spl,r8b..r15b, which need extra byte
* of encoding. al,cl,dl,bl have simpler encoding.
*/
static bool is_ereg_8l(u32 reg)
{
return is_ereg(reg) ||
(1 << reg) & (BIT(BPF_REG_1) |
BIT(BPF_REG_2) |
BIT(BPF_REG_FP));
}
static bool is_axreg(u32 reg)
{
return reg == BPF_REG_0;
}
/* Add modifiers if 'reg' maps to x86-64 registers R8..R15 */
static u8 add_1mod(u8 byte, u32 reg)
{
if (is_ereg(reg))
byte |= 1;
return byte;
}
static u8 add_2mod(u8 byte, u32 r1, u32 r2)
{
if (is_ereg(r1))
byte |= 1;
if (is_ereg(r2))
byte |= 4;
return 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 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);
}
/* Some 1-byte opcodes for binary ALU operations */
static u8 simple_alu_opcodes[] = {
[BPF_ADD] = 0x01,
[BPF_SUB] = 0x29,
[BPF_AND] = 0x21,
[BPF_OR] = 0x09,
[BPF_XOR] = 0x31,
[BPF_LSH] = 0xE0,
[BPF_RSH] = 0xE8,
[BPF_ARSH] = 0xF8,
};
static void jit_fill_hole(void *area, unsigned int size)
{
/* Fill whole space with INT3 instructions */
memset(area, 0xcc, size);
}
int bpf_arch_text_invalidate(void *dst, size_t len)
{
return IS_ERR_OR_NULL(text_poke_set(dst, 0xcc, len));
}
struct jit_context {
int cleanup_addr; /* Epilogue code offset */
/*
* Program specific offsets of labels in the code; these rely on the
* JIT doing at least 2 passes, recording the position on the first
* pass, only to generate the correct offset on the second pass.
*/
int tail_call_direct_label;
int tail_call_indirect_label;
};
/* Maximum number of bytes emitted while JITing one eBPF insn */
#define BPF_MAX_INSN_SIZE 128
#define BPF_INSN_SAFETY 64
/* Number of bytes emit_patch() needs to generate instructions */
#define X86_PATCH_SIZE 5
/* Number of bytes that will be skipped on tailcall */
#define X86_TAIL_CALL_OFFSET (11 + ENDBR_INSN_SIZE)
static void push_callee_regs(u8 **pprog, bool *callee_regs_used)
{
u8 *prog = *pprog;
if (callee_regs_used[0])
EMIT1(0x53); /* push rbx */
if (callee_regs_used[1])
EMIT2(0x41, 0x55); /* push r13 */
if (callee_regs_used[2])
EMIT2(0x41, 0x56); /* push r14 */
if (callee_regs_used[3])
EMIT2(0x41, 0x57); /* push r15 */
*pprog = prog;
}
static void pop_callee_regs(u8 **pprog, bool *callee_regs_used)
{
u8 *prog = *pprog;
if (callee_regs_used[3])
EMIT2(0x41, 0x5F); /* pop r15 */
if (callee_regs_used[2])
EMIT2(0x41, 0x5E); /* pop r14 */
if (callee_regs_used[1])
EMIT2(0x41, 0x5D); /* pop r13 */
if (callee_regs_used[0])
EMIT1(0x5B); /* pop rbx */
*pprog = prog;
}
/*
* Emit x86-64 prologue code for BPF program.
* bpf_tail_call helper will skip the first X86_TAIL_CALL_OFFSET bytes
* while jumping to another program
*/
static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf,
bool tail_call_reachable, bool is_subprog)
{
u8 *prog = *pprog;
/* BPF trampoline can be made to work without these nops,
* but let's waste 5 bytes for now and optimize later
*/
EMIT_ENDBR();
memcpy(prog, x86_nops[5], X86_PATCH_SIZE);
prog += X86_PATCH_SIZE;
if (!ebpf_from_cbpf) {
if (tail_call_reachable && !is_subprog)
EMIT2(0x31, 0xC0); /* xor eax, eax */
else
EMIT2(0x66, 0x90); /* nop2 */
}
EMIT1(0x55); /* push rbp */
EMIT3(0x48, 0x89, 0xE5); /* mov rbp, rsp */
/* X86_TAIL_CALL_OFFSET is here */
EMIT_ENDBR();
/* sub rsp, rounded_stack_depth */
if (stack_depth)
EMIT3_off32(0x48, 0x81, 0xEC, round_up(stack_depth, 8));
if (tail_call_reachable)
EMIT1(0x50); /* push rax */
*pprog = prog;
}
static int emit_patch(u8 **pprog, void *func, void *ip, u8 opcode)
{
u8 *prog = *pprog;
s64 offset;
offset = func - (ip + X86_PATCH_SIZE);
if (!is_simm32(offset)) {
pr_err("Target call %p is out of range\n", func);
return -ERANGE;
}
EMIT1_off32(opcode, offset);
*pprog = prog;
return 0;
}
static int emit_call(u8 **pprog, void *func, void *ip)
{
return emit_patch(pprog, func, ip, 0xE8);
}
static int emit_jump(u8 **pprog, void *func, void *ip)
{
return emit_patch(pprog, func, ip, 0xE9);
}
static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
void *old_addr, void *new_addr)
{
const u8 *nop_insn = x86_nops[5];
u8 old_insn[X86_PATCH_SIZE];
u8 new_insn[X86_PATCH_SIZE];
u8 *prog;
int ret;
memcpy(old_insn, nop_insn, X86_PATCH_SIZE);
if (old_addr) {
prog = old_insn;
ret = t == BPF_MOD_CALL ?
emit_call(&prog, old_addr, ip) :
emit_jump(&prog, old_addr, ip);
if (ret)
return ret;
}
memcpy(new_insn, nop_insn, X86_PATCH_SIZE);
if (new_addr) {
prog = new_insn;
ret = t == BPF_MOD_CALL ?
emit_call(&prog, new_addr, ip) :
emit_jump(&prog, new_addr, ip);
if (ret)
return ret;
}
ret = -EBUSY;
mutex_lock(&text_mutex);
if (memcmp(ip, old_insn, X86_PATCH_SIZE))
goto out;
ret = 1;
if (memcmp(ip, new_insn, X86_PATCH_SIZE)) {
text_poke_bp(ip, new_insn, X86_PATCH_SIZE, NULL);
ret = 0;
}
out:
mutex_unlock(&text_mutex);
return ret;
}
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
void *old_addr, void *new_addr)
{
if (!is_kernel_text((long)ip) &&
!is_bpf_text_address((long)ip))
/* BPF poking in modules is not supported */
return -EINVAL;
/*
* See emit_prologue(), for IBT builds the trampoline hook is preceded
* with an ENDBR instruction.
*/
if (is_endbr(*(u32 *)ip))
ip += ENDBR_INSN_SIZE;
return __bpf_arch_text_poke(ip, t, old_addr, new_addr);
}
#define EMIT_LFENCE() EMIT3(0x0F, 0xAE, 0xE8)
static void emit_indirect_jump(u8 **pprog, int reg, u8 *ip)
{
u8 *prog = *pprog;
if (cpu_feature_enabled(X86_FEATURE_RETPOLINE_LFENCE)) {
EMIT_LFENCE();
EMIT2(0xFF, 0xE0 + reg);
} else if (cpu_feature_enabled(X86_FEATURE_RETPOLINE)) {
OPTIMIZER_HIDE_VAR(reg);
emit_jump(&prog, &__x86_indirect_thunk_array[reg], ip);
} else {
EMIT2(0xFF, 0xE0 + reg);
}
*pprog = prog;
}
static void emit_return(u8 **pprog, u8 *ip)
{
u8 *prog = *pprog;
if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) {
emit_jump(&prog, &__x86_return_thunk, ip);
} else {
EMIT1(0xC3); /* ret */
if (IS_ENABLED(CONFIG_SLS))
EMIT1(0xCC); /* int3 */
}
*pprog = prog;
}
/*
* Generate the following code:
*
* ... bpf_tail_call(void *ctx, struct bpf_array *array, u64 index) ...
* if (index >= array->map.max_entries)
* goto out;
* if (tail_call_cnt++ >= MAX_TAIL_CALL_CNT)
* goto out;
* prog = array->ptrs[index];
* if (prog == NULL)
* goto out;
* goto *(prog->bpf_func + prologue_size);
* out:
*/
static void emit_bpf_tail_call_indirect(u8 **pprog, bool *callee_regs_used,
u32 stack_depth, u8 *ip,
struct jit_context *ctx)
{
int tcc_off = -4 - round_up(stack_depth, 8);
u8 *prog = *pprog, *start = *pprog;
int offset;
/*
* rdi - pointer to ctx
* rsi - pointer to bpf_array
* rdx - index in bpf_array
*/
/*
* 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));
offset = ctx->tail_call_indirect_label - (prog + 2 - start);
EMIT2(X86_JBE, offset); /* jbe out */
/*
* if (tail_call_cnt++ >= MAX_TAIL_CALL_CNT)
* goto out;
*/
EMIT2_off32(0x8B, 0x85, tcc_off); /* mov eax, dword ptr [rbp - tcc_off] */
EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp eax, MAX_TAIL_CALL_CNT */
offset = ctx->tail_call_indirect_label - (prog + 2 - start);
EMIT2(X86_JAE, offset); /* jae out */
EMIT3(0x83, 0xC0, 0x01); /* add eax, 1 */
EMIT2_off32(0x89, 0x85, tcc_off); /* mov dword ptr [rbp - tcc_off], eax */
/* prog = array->ptrs[index]; */
EMIT4_off32(0x48, 0x8B, 0x8C, 0xD6, /* mov rcx, [rsi + rdx * 8 + offsetof(...)] */
offsetof(struct bpf_array, ptrs));
/*
* if (prog == NULL)
* goto out;
*/
EMIT3(0x48, 0x85, 0xC9); /* test rcx,rcx */
offset = ctx->tail_call_indirect_label - (prog + 2 - start);
EMIT2(X86_JE, offset); /* je out */
pop_callee_regs(&prog, callee_regs_used);
EMIT1(0x58); /* pop rax */
if (stack_depth)
EMIT3_off32(0x48, 0x81, 0xC4, /* add rsp, sd */
round_up(stack_depth, 8));
/* goto *(prog->bpf_func + X86_TAIL_CALL_OFFSET); */
EMIT4(0x48, 0x8B, 0x49, /* mov rcx, qword ptr [rcx + 32] */
offsetof(struct bpf_prog, bpf_func));
EMIT4(0x48, 0x83, 0xC1, /* add rcx, X86_TAIL_CALL_OFFSET */
X86_TAIL_CALL_OFFSET);
/*
* Now we're ready to jump into next BPF program
* rdi == ctx (1st arg)
* rcx == prog->bpf_func + X86_TAIL_CALL_OFFSET
*/
emit_indirect_jump(&prog, 1 /* rcx */, ip + (prog - start));
/* out: */
ctx->tail_call_indirect_label = prog - start;
*pprog = prog;
}
static void emit_bpf_tail_call_direct(struct bpf_jit_poke_descriptor *poke,
u8 **pprog, u8 *ip,
bool *callee_regs_used, u32 stack_depth,
struct jit_context *ctx)
{
int tcc_off = -4 - round_up(stack_depth, 8);
u8 *prog = *pprog, *start = *pprog;
int offset;
/*
* if (tail_call_cnt++ >= MAX_TAIL_CALL_CNT)
* goto out;
*/
EMIT2_off32(0x8B, 0x85, tcc_off); /* mov eax, dword ptr [rbp - tcc_off] */
EMIT3(0x83, 0xF8, MAX_TAIL_CALL_CNT); /* cmp eax, MAX_TAIL_CALL_CNT */
offset = ctx->tail_call_direct_label - (prog + 2 - start);
EMIT2(X86_JAE, offset); /* jae out */
EMIT3(0x83, 0xC0, 0x01); /* add eax, 1 */
EMIT2_off32(0x89, 0x85, tcc_off); /* mov dword ptr [rbp - tcc_off], eax */
poke->tailcall_bypass = ip + (prog - start);
poke->adj_off = X86_TAIL_CALL_OFFSET;
poke->tailcall_target = ip + ctx->tail_call_direct_label - X86_PATCH_SIZE;
poke->bypass_addr = (u8 *)poke->tailcall_target + X86_PATCH_SIZE;
emit_jump(&prog, (u8 *)poke->tailcall_target + X86_PATCH_SIZE,
poke->tailcall_bypass);
pop_callee_regs(&prog, callee_regs_used);
EMIT1(0x58); /* pop rax */
if (stack_depth)
EMIT3_off32(0x48, 0x81, 0xC4, round_up(stack_depth, 8));
memcpy(prog, x86_nops[5], X86_PATCH_SIZE);
prog += X86_PATCH_SIZE;
/* out: */
ctx->tail_call_direct_label = prog - start;
*pprog = prog;
}
static void bpf_tail_call_direct_fixup(struct bpf_prog *prog)
{
struct bpf_jit_poke_descriptor *poke;
struct bpf_array *array;
struct bpf_prog *target;
int i, ret;
for (i = 0; i < prog->aux->size_poke_tab; i++) {
poke = &prog->aux->poke_tab[i];
if (poke->aux && poke->aux != prog->aux)
continue;
WARN_ON_ONCE(READ_ONCE(poke->tailcall_target_stable));
if (poke->reason != BPF_POKE_REASON_TAIL_CALL)
continue;
array = container_of(poke->tail_call.map, struct bpf_array, map);
mutex_lock(&array->aux->poke_mutex);
target = array->ptrs[poke->tail_call.key];
if (target) {
ret = __bpf_arch_text_poke(poke->tailcall_target,
BPF_MOD_JUMP, NULL,
(u8 *)target->bpf_func +
poke->adj_off);
BUG_ON(ret < 0);
ret = __bpf_arch_text_poke(poke->tailcall_bypass,
BPF_MOD_JUMP,
(u8 *)poke->tailcall_target +
X86_PATCH_SIZE, NULL);
BUG_ON(ret < 0);
}
WRITE_ONCE(poke->tailcall_target_stable, true);
mutex_unlock(&array->aux->poke_mutex);
}
}
static void emit_mov_imm32(u8 **pprog, bool sign_propagate,
u32 dst_reg, const u32 imm32)
{
u8 *prog = *pprog;
u8 b1, b2, b3;
/*
* Optimization: if imm32 is positive, use 'mov %eax, imm32'
* (which zero-extends imm32) to save 2 bytes.
*/
if (sign_propagate && (s32)imm32 < 0) {
/* 'mov %rax, imm32' sign extends imm32 */
b1 = add_1mod(0x48, dst_reg);
b2 = 0xC7;
b3 = 0xC0;
EMIT3_off32(b1, b2, add_1reg(b3, dst_reg), imm32);
goto done;
}
/*
* Optimization: if imm32 is zero, use 'xor %eax, %eax'
* to save 3 bytes.
*/
if (imm32 == 0) {
if (is_ereg(dst_reg))
EMIT1(add_2mod(0x40, dst_reg, dst_reg));
b2 = 0x31; /* xor */
b3 = 0xC0;
EMIT2(b2, add_2reg(b3, dst_reg, dst_reg));
goto done;
}
/* mov %eax, imm32 */
if (is_ereg(dst_reg))
EMIT1(add_1mod(0x40, dst_reg));
EMIT1_off32(add_1reg(0xB8, dst_reg), imm32);
done:
*pprog = prog;
}
static void emit_mov_imm64(u8 **pprog, u32 dst_reg,
const u32 imm32_hi, const u32 imm32_lo)
{
u8 *prog = *pprog;
if (is_uimm32(((u64)imm32_hi << 32) | (u32)imm32_lo)) {
/*
* 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.
*/
emit_mov_imm32(&prog, false, dst_reg, imm32_lo);
} else {
/* movabsq %rax, imm64 */
EMIT2(add_1mod(0x48, dst_reg), add_1reg(0xB8, dst_reg));
EMIT(imm32_lo, 4);
EMIT(imm32_hi, 4);
}
*pprog = prog;
}
static void emit_mov_reg(u8 **pprog, bool is64, u32 dst_reg, u32 src_reg)
{
u8 *prog = *pprog;
if (is64) {
/* mov dst, src */
EMIT_mov(dst_reg, src_reg);
} else {
/* mov32 dst, src */
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));
}
*pprog = prog;
}
/* Emit the suffix (ModR/M etc) for addressing *(ptr_reg + off) and val_reg */
static void emit_insn_suffix(u8 **pprog, u32 ptr_reg, u32 val_reg, int off)
{
u8 *prog = *pprog;
if (is_imm8(off)) {
/* 1-byte signed displacement.
*
* If off == 0 we could skip this and save one extra byte, but
* special case of x86 R13 which always needs an offset is not
* worth the hassle
*/
EMIT2(add_2reg(0x40, ptr_reg, val_reg), off);
} else {
/* 4-byte signed displacement */
EMIT1_off32(add_2reg(0x80, ptr_reg, val_reg), off);
}
*pprog = prog;
}
/*
* Emit a REX byte if it will be necessary to address these registers
*/
static void maybe_emit_mod(u8 **pprog, u32 dst_reg, u32 src_reg, bool is64)
{
u8 *prog = *pprog;
if (is64)
EMIT1(add_2mod(0x48, dst_reg, src_reg));
else if (is_ereg(dst_reg) || is_ereg(src_reg))
EMIT1(add_2mod(0x40, dst_reg, src_reg));
*pprog = prog;
}
/*
* Similar version of maybe_emit_mod() for a single register
*/
static void maybe_emit_1mod(u8 **pprog, u32 reg, bool is64)
{
u8 *prog = *pprog;
if (is64)
EMIT1(add_1mod(0x48, reg));
else if (is_ereg(reg))
EMIT1(add_1mod(0x40, reg));
*pprog = prog;
}
/* LDX: dst_reg = *(u8*)(src_reg + off) */
static void emit_ldx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
{
u8 *prog = *pprog;
switch (size) {
case BPF_B:
/* Emit 'movzx rax, byte ptr [rax + off]' */
EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xB6);
break;
case BPF_H:
/* Emit 'movzx rax, word ptr [rax + off]' */
EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xB7);
break;
case BPF_W:
/* 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);
break;
case BPF_DW:
/* Emit 'mov rax, qword ptr [rax+0x14]' */
EMIT2(add_2mod(0x48, src_reg, dst_reg), 0x8B);
break;
}
emit_insn_suffix(&prog, src_reg, dst_reg, off);
*pprog = prog;
}
/* STX: *(u8*)(dst_reg + off) = src_reg */
static void emit_stx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
{
u8 *prog = *pprog;
switch (size) {
case BPF_B:
/* Emit 'mov byte ptr [rax + off], al' */
if (is_ereg(dst_reg) || is_ereg_8l(src_reg))
/* Add extra byte for eregs or SIL,DIL,BPL in src_reg */
EMIT2(add_2mod(0x40, dst_reg, src_reg), 0x88);
else
EMIT1(0x88);
break;
case BPF_H:
if (is_ereg(dst_reg) || is_ereg(src_reg))
EMIT3(0x66, add_2mod(0x40, dst_reg, src_reg), 0x89);
else
EMIT2(0x66, 0x89);
break;
case BPF_W:
if (is_ereg(dst_reg) || is_ereg(src_reg))
EMIT2(add_2mod(0x40, dst_reg, src_reg), 0x89);
else
EMIT1(0x89);
break;
case BPF_DW:
EMIT2(add_2mod(0x48, dst_reg, src_reg), 0x89);
break;
}
emit_insn_suffix(&prog, dst_reg, src_reg, off);
*pprog = prog;
}
static int emit_atomic(u8 **pprog, u8 atomic_op,
u32 dst_reg, u32 src_reg, s16 off, u8 bpf_size)
{
u8 *prog = *pprog;
EMIT1(0xF0); /* lock prefix */
maybe_emit_mod(&prog, dst_reg, src_reg, bpf_size == BPF_DW);
/* emit opcode */
switch (atomic_op) {
case BPF_ADD:
case BPF_AND:
case BPF_OR:
case BPF_XOR:
/* lock *(u32/u64*)(dst_reg + off) <op>= src_reg */
EMIT1(simple_alu_opcodes[atomic_op]);
break;
case BPF_ADD | BPF_FETCH:
/* src_reg = atomic_fetch_add(dst_reg + off, src_reg); */
EMIT2(0x0F, 0xC1);
break;
case BPF_XCHG:
/* src_reg = atomic_xchg(dst_reg + off, src_reg); */
EMIT1(0x87);
break;
case BPF_CMPXCHG:
/* r0 = atomic_cmpxchg(dst_reg + off, r0, src_reg); */
EMIT2(0x0F, 0xB1);
break;
default:
pr_err("bpf_jit: unknown atomic opcode %02x\n", atomic_op);
return -EFAULT;
}
emit_insn_suffix(&prog, dst_reg, src_reg, off);
*pprog = prog;
return 0;
}
bool ex_handler_bpf(const struct exception_table_entry *x, struct pt_regs *regs)
{
u32 reg = x->fixup >> 8;
/* jump over faulting load and clear dest register */
*(unsigned long *)((void *)regs + reg) = 0;
regs->ip += x->fixup & 0xff;
return true;
}
static void detect_reg_usage(struct bpf_insn *insn, int insn_cnt,
bool *regs_used, bool *tail_call_seen)
{
int i;
for (i = 1; i <= insn_cnt; i++, insn++) {
if (insn->code == (BPF_JMP | BPF_TAIL_CALL))
*tail_call_seen = true;
if (insn->dst_reg == BPF_REG_6 || insn->src_reg == BPF_REG_6)
regs_used[0] = true;
if (insn->dst_reg == BPF_REG_7 || insn->src_reg == BPF_REG_7)
regs_used[1] = true;
if (insn->dst_reg == BPF_REG_8 || insn->src_reg == BPF_REG_8)
regs_used[2] = true;
if (insn->dst_reg == BPF_REG_9 || insn->src_reg == BPF_REG_9)
regs_used[3] = true;
}
}
static void emit_nops(u8 **pprog, int len)
{
u8 *prog = *pprog;
int i, noplen;
while (len > 0) {
noplen = len;
if (noplen > ASM_NOP_MAX)
noplen = ASM_NOP_MAX;
for (i = 0; i < noplen; i++)
EMIT1(x86_nops[noplen][i]);
len -= noplen;
}
*pprog = prog;
}
#define INSN_SZ_DIFF (((addrs[i] - addrs[i - 1]) - (prog - temp)))
static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, u8 *rw_image,
int oldproglen, struct jit_context *ctx, bool jmp_padding)
{
bool tail_call_reachable = bpf_prog->aux->tail_call_reachable;
struct bpf_insn *insn = bpf_prog->insnsi;
bool callee_regs_used[4] = {};
int insn_cnt = bpf_prog->len;
bool tail_call_seen = false;
bool seen_exit = false;
u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY];
int i, excnt = 0;
int ilen, proglen = 0;
u8 *prog = temp;
int err;
detect_reg_usage(insn, insn_cnt, callee_regs_used,
&tail_call_seen);
/* tail call's presence in current prog implies it is reachable */
tail_call_reachable |= tail_call_seen;
emit_prologue(&prog, bpf_prog->aux->stack_depth,
bpf_prog_was_classic(bpf_prog), tail_call_reachable,
bpf_prog->aux->func_idx != 0);
push_callee_regs(&prog, callee_regs_used);
ilen = prog - temp;
if (rw_image)
memcpy(rw_image + proglen, temp, ilen);
proglen += ilen;
addrs[0] = proglen;
prog = temp;
for (i = 1; i <= insn_cnt; i++, insn++) {
const s32 imm32 = insn->imm;
u32 dst_reg = insn->dst_reg;
u32 src_reg = insn->src_reg;
u8 b2 = 0, b3 = 0;
u8 *start_of_ldx;
s64 jmp_offset;
u8 jmp_cond;
u8 *func;
int nops;
switch (insn->code) {
/* ALU */
case BPF_ALU | BPF_ADD | BPF_X:
case BPF_ALU | BPF_SUB | BPF_X:
case BPF_ALU | BPF_AND | BPF_X:
case BPF_ALU | BPF_OR | BPF_X:
case BPF_ALU | BPF_XOR | BPF_X:
case BPF_ALU64 | BPF_ADD | BPF_X:
case BPF_ALU64 | BPF_SUB | BPF_X:
case BPF_ALU64 | BPF_AND | BPF_X:
case BPF_ALU64 | BPF_OR | BPF_X:
case BPF_ALU64 | BPF_XOR | BPF_X:
maybe_emit_mod(&prog, dst_reg, src_reg,
BPF_CLASS(insn->code) == BPF_ALU64);
b2 = simple_alu_opcodes[BPF_OP(insn->code)];
EMIT2(b2, add_2reg(0xC0, dst_reg, src_reg));
break;
case BPF_ALU64 | BPF_MOV | BPF_X:
case BPF_ALU | BPF_MOV | BPF_X:
emit_mov_reg(&prog,
BPF_CLASS(insn->code) == BPF_ALU64,
dst_reg, src_reg);
break;
/* neg dst */
case BPF_ALU | BPF_NEG:
case BPF_ALU64 | BPF_NEG:
maybe_emit_1mod(&prog, dst_reg,
BPF_CLASS(insn->code) == BPF_ALU64);
EMIT2(0xF7, add_1reg(0xD8, dst_reg));
break;
case BPF_ALU | BPF_ADD | BPF_K:
case BPF_ALU | BPF_SUB | BPF_K:
case BPF_ALU | BPF_AND | BPF_K:
case BPF_ALU | BPF_OR | BPF_K:
case BPF_ALU | BPF_XOR | BPF_K:
case BPF_ALU64 | BPF_ADD | BPF_K:
case BPF_ALU64 | BPF_SUB | BPF_K:
case BPF_ALU64 | BPF_AND | BPF_K:
case BPF_ALU64 | BPF_OR | BPF_K:
case BPF_ALU64 | BPF_XOR | BPF_K:
maybe_emit_1mod(&prog, dst_reg,
BPF_CLASS(insn->code) == BPF_ALU64);
/*
* b3 holds 'normal' opcode, b2 short form only valid
* in case dst is eax/rax.
*/
switch (BPF_OP(insn->code)) {
case BPF_ADD:
b3 = 0xC0;
b2 = 0x05;
break;
case BPF_SUB:
b3 = 0xE8;
b2 = 0x2D;
break;
case BPF_AND:
b3 = 0xE0;
b2 = 0x25;
break;