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linux/arch/x86/net/bpf_jit_comp.c
Peter Zijlstra d77cfe594a x86/bpf: Use alternative RET encoding 
Use the return thunk in eBPF generated code, if needed.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
2022-06-27 10:33:58 +02:00

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// SPDX-License-Identifier: GPL-2.0-only
/*
* BPF JIT compiler
*
* Copyright (C) 2011-2013 Eric Dumazet (eric.dumazet@gmail.com)
* 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;
case BPF_OR:
b3 = 0xC8;
b2 = 0x0D;
break;
case BPF_XOR:
b3 = 0xF0;
b2 = 0x35;
break;
}
if (is_imm8(imm32))
EMIT3(0x83, add_1reg(b3, dst_reg), imm32);
else if (is_axreg(dst_reg))
EMIT1_off32(b2, imm32);
else
EMIT2_off32(0x81, add_1reg(b3, dst_reg), imm32);
break;
case BPF_ALU64 | BPF_MOV | BPF_K:
case BPF_ALU | BPF_MOV | BPF_K:
emit_mov_imm32(&prog, BPF_CLASS(insn->code) == BPF_ALU64,
dst_reg, imm32);
break;
case BPF_LD | BPF_IMM | BPF_DW:
emit_mov_imm64(&prog, dst_reg, insn[1].imm, insn[0].imm);
insn++;
i++;
break;
/* dst %= src, dst /= src, dst %= imm32, dst /= imm32 */
case BPF_ALU | BPF_MOD | BPF_X:
case BPF_ALU | BPF_DIV | BPF_X:
case BPF_ALU | BPF_MOD | BPF_K:
case BPF_ALU | BPF_DIV | BPF_K:
case BPF_ALU64 | BPF_MOD | BPF_X:
case BPF_ALU64 | BPF_DIV | BPF_X:
case BPF_ALU64 | BPF_MOD | BPF_K:
case BPF_ALU64 | BPF_DIV | BPF_K: {
bool is64 = BPF_CLASS(insn->code) == BPF_ALU64;
if (dst_reg != BPF_REG_0)
EMIT1(0x50); /* push rax */
if (dst_reg != BPF_REG_3)
EMIT1(0x52); /* push rdx */
if (BPF_SRC(insn->code) == BPF_X) {
if (src_reg == BPF_REG_0 ||
src_reg == BPF_REG_3) {
/* mov r11, src_reg */
EMIT_mov(AUX_REG, src_reg);
src_reg = AUX_REG;
}
} else {
/* mov r11, imm32 */
EMIT3_off32(0x49, 0xC7, 0xC3, imm32);
src_reg = AUX_REG;
}
if (dst_reg != BPF_REG_0)
/* mov rax, dst_reg */
emit_mov_reg(&prog, is64, BPF_REG_0, dst_reg);
/*
* xor edx, edx
* equivalent to 'xor rdx, rdx', but one byte less
*/
EMIT2(0x31, 0xd2);
/* div src_reg */
maybe_emit_1mod(&prog, src_reg, is64);
EMIT2(0xF7, add_1reg(0xF0, src_reg));
if (BPF_OP(insn->code) == BPF_MOD &&
dst_reg != BPF_REG_3)
/* mov dst_reg, rdx */
emit_mov_reg(&prog, is64, dst_reg, BPF_REG_3);
else if (BPF_OP(insn->code) == BPF_DIV &&
dst_reg != BPF_REG_0)
/* mov dst_reg, rax */
emit_mov_reg(&prog, is64, dst_reg, BPF_REG_0);
if (dst_reg != BPF_REG_3)
EMIT1(0x5A); /* pop rdx */
if (dst_reg != BPF_REG_0)
EMIT1(0x58); /* pop rax */
break;
}
case BPF_ALU | BPF_MUL | BPF_K:
case BPF_ALU64 | BPF_MUL | BPF_K:
maybe_emit_mod(&prog, dst_reg, dst_reg,
BPF_CLASS(insn->code) == BPF_ALU64);
if (is_imm8(imm32))
/* imul dst_reg, dst_reg, imm8 */
EMIT3(0x6B, add_2reg(0xC0, dst_reg, dst_reg),
imm32);
else
/* imul dst_reg, dst_reg, imm32 */
EMIT2_off32(0x69,
add_2reg(0xC0, dst_reg, dst_reg),
imm32);
break;
case BPF_ALU | BPF_MUL | BPF_X:
case BPF_ALU64 | BPF_MUL | BPF_X:
maybe_emit_mod(&prog, src_reg, dst_reg,
BPF_CLASS(insn->code) == BPF_ALU64);
/* imul dst_reg, src_reg */
EMIT3(0x0F, 0xAF, add_2reg(0xC0, src_reg, dst_reg));
break;
/* 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_LSH | BPF_K:
case BPF_ALU64 | BPF_RSH | BPF_K:
case BPF_ALU64 | BPF_ARSH | BPF_K:
maybe_emit_1mod(&prog, dst_reg,
BPF_CLASS(insn->code) == BPF_ALU64);
b3 = simple_alu_opcodes[BPF_OP(insn->code)];
if (imm32 == 1)
EMIT2(0xD1, add_1reg(b3, dst_reg));
else
EMIT3(0xC1, add_1reg(b3, dst_reg), imm32);
break;
case BPF_ALU | BPF_LSH | BPF_X:
case BPF_ALU | BPF_RSH | BPF_X:
case BPF_ALU | BPF_ARSH | BPF_X:
case BPF_ALU64 | BPF_LSH | BPF_X:
case BPF_ALU64 | BPF_RSH | BPF_X:
case BPF_ALU64 | BPF_ARSH | BPF_X:
/* Check for bad case when dst_reg == rcx */
if (dst_reg == BPF_REG_4) {
/* mov r11, dst_reg */
EMIT_mov(AUX_REG, dst_reg);
dst_reg = AUX_REG;
}
if (src_reg != BPF_REG_4) { /* common case */
EMIT1(0x51); /* push rcx */
/* mov rcx, src_reg */
EMIT_mov(BPF_REG_4, src_reg);
}
/* shl %rax, %cl | shr %rax, %cl | sar %rax, %cl */
maybe_emit_1mod(&prog, dst_reg,
BPF_CLASS(insn->code) == BPF_ALU64);
b3 = simple_alu_opcodes[BPF_OP(insn->code)];
EMIT2(0xD3, add_1reg(b3, dst_reg));
if (src_reg != BPF_REG_4)
EMIT1(0x59); /* pop rcx */
if (insn->dst_reg == BPF_REG_4)
/* mov dst_reg, r11 */
EMIT_mov(insn->dst_reg, AUX_REG);
break;
case BPF_ALU | BPF_END | BPF_FROM_BE:
switch (imm32) {
case 16:
/* Emit 'ror %ax, 8' to swap lower 2 bytes */
EMIT1(0x66);
if (is_ereg(dst_reg))
EMIT1(0x41);
EMIT3(0xC1, add_1reg(0xC8, dst_reg), 8);
/* Emit 'movzwl eax, ax' */
if (is_ereg(dst_reg))
EMIT3(0x45, 0x0F, 0xB7);
else
EMIT2(0x0F, 0xB7);
EMIT1(add_2reg(0xC0, dst_reg, dst_reg));
break;
case 32:
/* Emit 'bswap eax' to swap lower 4 bytes */
if (is_ereg(dst_reg))
EMIT2(0x41, 0x0F);
else
EMIT1(0x0F);
EMIT1(add_1reg(0xC8, dst_reg));
break;
case 64:
/* Emit 'bswap rax' to swap 8 bytes */
EMIT3(add_1mod(0x48, dst_reg), 0x0F,
add_1reg(0xC8, dst_reg));
break;
}
break;
case BPF_ALU | BPF_END | BPF_FROM_LE:
switch (imm32) {
case 16:
/*
* Emit 'movzwl eax, ax' to zero extend 16-bit
* into 64 bit
*/
if (is_ereg(dst_reg))
EMIT3(0x45, 0x0F, 0xB7);
else
EMIT2(0x0F, 0xB7);
EMIT1(add_2reg(0xC0, dst_reg, dst_reg));
break;
case 32:
/* 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));
break;
case 64:
/* nop */
break;
}
break;
/* speculation barrier */
case BPF_ST | BPF_NOSPEC:
if (boot_cpu_has(X86_FEATURE_XMM2))
EMIT_LFENCE();
break;
/* ST: *(u8*)(dst_reg + off) = imm */
case BPF_ST | BPF_MEM | BPF_B:
if (is_ereg(dst_reg))
EMIT2(0x41, 0xC6);
else
EMIT1(0xC6);
goto st;
case BPF_ST | BPF_MEM | BPF_H:
if (is_ereg(dst_reg))
EMIT3(0x66, 0x41, 0xC7);
else
EMIT2(0x66, 0xC7);
goto st;
case BPF_ST | BPF_MEM | BPF_W:
if (is_ereg(dst_reg))
EMIT2(0x41, 0xC7);
else
EMIT1(0xC7);
goto st;
case BPF_ST | BPF_MEM | BPF_DW:
EMIT2(add_1mod(0x48, dst_reg), 0xC7);
st: if (is_imm8(insn->off))
EMIT2(add_1reg(0x40, dst_reg), insn->off);
else
EMIT1_off32(add_1reg(0x80, dst_reg), insn->off);
EMIT(imm32, bpf_size_to_x86_bytes(BPF_SIZE(insn->code)));
break;
/* STX: *(u8*)(dst_reg + off) = src_reg */
case BPF_STX | BPF_MEM | BPF_B:
case BPF_STX | BPF_MEM | BPF_H:
case BPF_STX | BPF_MEM | BPF_W:
case BPF_STX | BPF_MEM | BPF_DW:
emit_stx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn->off);
break;
/* LDX: dst_reg = *(u8*)(src_reg + off) */
case BPF_LDX | BPF_MEM | BPF_B:
case BPF_LDX | BPF_PROBE_MEM | BPF_B:
case BPF_LDX | BPF_MEM | BPF_H:
case BPF_LDX | BPF_PROBE_MEM | BPF_H:
case BPF_LDX | BPF_MEM | BPF_W:
case BPF_LDX | BPF_PROBE_MEM | BPF_W:
case BPF_LDX | BPF_MEM | BPF_DW:
case BPF_LDX | BPF_PROBE_MEM | BPF_DW:
if (BPF_MODE(insn->code) == BPF_PROBE_MEM) {
/* Though the verifier prevents negative insn->off in BPF_PROBE_MEM
* add abs(insn->off) to the limit to make sure that negative
* offset won't be an issue.
* insn->off is s16, so it won't affect valid pointers.
*/
u64 limit = TASK_SIZE_MAX + PAGE_SIZE + abs(insn->off);
u8 *end_of_jmp1, *end_of_jmp2;
/* Conservatively check that src_reg + insn->off is a kernel address:
* 1. src_reg + insn->off >= limit
* 2. src_reg + insn->off doesn't become small positive.
* Cannot do src_reg + insn->off >= limit in one branch,
* since it needs two spare registers, but JIT has only one.
*/
/* movabsq r11, limit */
EMIT2(add_1mod(0x48, AUX_REG), add_1reg(0xB8, AUX_REG));
EMIT((u32)limit, 4);
EMIT(limit >> 32, 4);
/* cmp src_reg, r11 */
maybe_emit_mod(&prog, src_reg, AUX_REG, true);
EMIT2(0x39, add_2reg(0xC0, src_reg, AUX_REG));
/* if unsigned '<' goto end_of_jmp2 */
EMIT2(X86_JB, 0);
end_of_jmp1 = prog;
/* mov r11, src_reg */
emit_mov_reg(&prog, true, AUX_REG, src_reg);
/* add r11, insn->off */
maybe_emit_1mod(&prog, AUX_REG, true);
EMIT2_off32(0x81, add_1reg(0xC0, AUX_REG), insn->off);
/* jmp if not carry to start_of_ldx
* Otherwise ERR_PTR(-EINVAL) + 128 will be the user addr
* that has to be rejected.
*/
EMIT2(0x73 /* JNC */, 0);
end_of_jmp2 = prog;
/* xor dst_reg, dst_reg */
emit_mov_imm32(&prog, false, dst_reg, 0);
/* jmp byte_after_ldx */
EMIT2(0xEB, 0);
/* populate jmp_offset for JB above to jump to xor dst_reg */
end_of_jmp1[-1] = end_of_jmp2 - end_of_jmp1;
/* populate jmp_offset for JNC above to jump to start_of_ldx */
start_of_ldx = prog;
end_of_jmp2[-1] = start_of_ldx - end_of_jmp2;
}
emit_ldx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn->off);
if (BPF_MODE(insn->code) == BPF_PROBE_MEM) {
struct exception_table_entry *ex;
u8 *_insn = image + proglen + (start_of_ldx - temp);
s64 delta;
/* populate jmp_offset for JMP above */
start_of_ldx[-1] = prog - start_of_ldx;
if (!bpf_prog->aux->extable)
break;
if (excnt >= bpf_prog->aux->num_exentries) {
pr_err("ex gen bug\n");
return -EFAULT;
}
ex = &bpf_prog->aux->extable[excnt++];
delta = _insn - (u8 *)&ex->insn;
if (!is_simm32(delta)) {
pr_err("extable->insn doesn't fit into 32-bit\n");
return -EFAULT;
}
/* switch ex to rw buffer for writes */
ex = (void *)rw_image + ((void *)ex - (void *)image);
ex->insn = delta;
ex->data = EX_TYPE_BPF;
if (dst_reg > BPF_REG_9) {
pr_err("verifier error\n");
return -EFAULT;
}
/*
* Compute size of x86 insn and its target dest x86 register.
* ex_handler_bpf() will use lower 8 bits to adjust
* pt_regs->ip to jump over this x86 instruction
* and upper bits to figure out which pt_regs to zero out.
* End result: x86 insn "mov rbx, qword ptr [rax+0x14]"
* of 4 bytes will be ignored and rbx will be zero inited.
*/
ex->fixup = (prog - start_of_ldx) | (reg2pt_regs[dst_reg] << 8);
}
break;
case BPF_STX | BPF_ATOMIC | BPF_W:
case BPF_STX | BPF_ATOMIC | BPF_DW:
if (insn->imm == (BPF_AND | BPF_FETCH) ||
insn->imm == (BPF_OR | BPF_FETCH) ||
insn->imm == (BPF_XOR | BPF_FETCH)) {
bool is64 = BPF_SIZE(insn->code) == BPF_DW;
u32 real_src_reg = src_reg;
u32 real_dst_reg = dst_reg;
u8 *branch_target;
/*
* Can't be implemented with a single x86 insn.
* Need to do a CMPXCHG loop.
*/
/* Will need RAX as a CMPXCHG operand so save R0 */
emit_mov_reg(&prog, true, BPF_REG_AX, BPF_REG_0);
if (src_reg == BPF_REG_0)
real_src_reg = BPF_REG_AX;
if (dst_reg == BPF_REG_0)
real_dst_reg = BPF_REG_AX;
branch_target = prog;
/* Load old value */
emit_ldx(&prog, BPF_SIZE(insn->code),
BPF_REG_0, real_dst_reg, insn->off);
/*
* Perform the (commutative) operation locally,
* put the result in the AUX_REG.
*/
emit_mov_reg(&prog, is64, AUX_REG, BPF_REG_0);
maybe_emit_mod(&prog, AUX_REG, real_src_reg, is64);
EMIT2(simple_alu_opcodes[BPF_OP(insn->imm)],
add_2reg(0xC0, AUX_REG, real_src_reg));
/* Attempt to swap in new value */
err = emit_atomic(&prog, BPF_CMPXCHG,
real_dst_reg, AUX_REG,
insn->off,
BPF_SIZE(insn->code));
if (WARN_ON(err))
return err;
/*
* ZF tells us whether we won the race. If it's
* cleared we need to try again.
*/
EMIT2(X86_JNE, -(prog - branch_target) - 2);
/* Return the pre-modification value */
emit_mov_reg(&prog, is64, real_src_reg, BPF_REG_0);
/* Restore R0 after clobbering RAX */
emit_mov_reg(&prog, true, BPF_REG_0, BPF_REG_AX);
break;
}
err = emit_atomic(&prog, insn->imm, dst_reg, src_reg,
insn->off, BPF_SIZE(insn->code));
if (err)
return err;
break;
/* call */
case BPF_JMP | BPF_CALL:
func = (u8 *) __bpf_call_base + imm32;
if (tail_call_reachable) {
/* mov rax, qword ptr [rbp - rounded_stack_depth - 8] */
EMIT3_off32(0x48, 0x8B, 0x85,
-round_up(bpf_prog->aux->stack_depth, 8) - 8);
if (!imm32 || emit_call(&prog, func, image + addrs[i - 1] + 7))
return -EINVAL;
} else {
if (!imm32 || emit_call(&prog, func, image + addrs[i - 1]))
return -EINVAL;
}
break;
case BPF_JMP | BPF_TAIL_CALL:
if (imm32)
emit_bpf_tail_call_direct(&bpf_prog->aux->poke_tab[imm32 - 1],
&prog, image + addrs[i - 1],
callee_regs_used,
bpf_prog->aux->stack_depth,
ctx);
else
emit_bpf_tail_call_indirect(&prog,
callee_regs_used,
bpf_prog->aux->stack_depth,
image + addrs[i - 1],
ctx);
break;
/* cond jump */
case BPF_JMP | BPF_JEQ | BPF_X:
case BPF_JMP | BPF_JNE | BPF_X:
case BPF_JMP | BPF_JGT | BPF_X:
case BPF_JMP | BPF_JLT | BPF_X:
case BPF_JMP | BPF_JGE | BPF_X:
case BPF_JMP | BPF_JLE | BPF_X:
case BPF_JMP | BPF_JSGT | BPF_X:
case BPF_JMP | BPF_JSLT | BPF_X:
case BPF_JMP | BPF_JSGE | BPF_X:
case BPF_JMP | BPF_JSLE | BPF_X:
case BPF_JMP32 | BPF_JEQ | BPF_X:
case BPF_JMP32 | BPF_JNE | BPF_X:
case BPF_JMP32 | BPF_JGT | BPF_X:
case BPF_JMP32 | BPF_JLT | BPF_X:
case BPF_JMP32 | BPF_JGE | BPF_X:
case BPF_JMP32 | BPF_JLE | BPF_X:
case BPF_JMP32 | BPF_JSGT | BPF_X:
case BPF_JMP32 | BPF_JSLT | BPF_X:
case BPF_JMP32 | BPF_JSGE | BPF_X:
case BPF_JMP32 | BPF_JSLE | BPF_X:
/* cmp dst_reg, src_reg */
maybe_emit_mod(&prog, dst_reg, src_reg,
BPF_CLASS(insn->code) == BPF_JMP);
EMIT2(0x39, add_2reg(0xC0, dst_reg, src_reg));
goto emit_cond_jmp;
case BPF_JMP | BPF_JSET | BPF_X:
case BPF_JMP32 | BPF_JSET | BPF_X:
/* test dst_reg, src_reg */
maybe_emit_mod(&prog, dst_reg, src_reg,
BPF_CLASS(insn->code) == BPF_JMP);
EMIT2(0x85, add_2reg(0xC0, dst_reg, src_reg));
goto emit_cond_jmp;
case BPF_JMP | BPF_JSET | BPF_K:
case BPF_JMP32 | BPF_JSET | BPF_K:
/* test dst_reg, imm32 */
maybe_emit_1mod(&prog, dst_reg,
BPF_CLASS(insn->code) == BPF_JMP);
EMIT2_off32(0xF7, add_1reg(0xC0, dst_reg), imm32);
goto emit_cond_jmp;
case BPF_JMP | BPF_JEQ | BPF_K:
case BPF_JMP | BPF_JNE | BPF_K:
case BPF_JMP | BPF_JGT | BPF_K:
case BPF_JMP | BPF_JLT | BPF_K:
case BPF_JMP | BPF_JGE | BPF_K:
case BPF_JMP | BPF_JLE | BPF_K:
case BPF_JMP | BPF_JSGT | BPF_K:
case BPF_JMP | BPF_JSLT | BPF_K:
case BPF_JMP | BPF_JSGE | BPF_K:
case BPF_JMP | BPF_JSLE | BPF_K:
case BPF_JMP32 | BPF_JEQ | BPF_K:
case BPF_JMP32 | BPF_JNE | BPF_K:
case BPF_JMP32 | BPF_JGT | BPF_K:
case BPF_JMP32 | BPF_JLT | BPF_K:
case BPF_JMP32 | BPF_JGE | BPF_K:
case BPF_JMP32 | BPF_JLE | BPF_K:
case BPF_JMP32 | BPF_JSGT | BPF_K:
case BPF_JMP32 | BPF_JSLT | BPF_K:
case BPF_JMP32 | BPF_JSGE | BPF_K:
case BPF_JMP32 | BPF_JSLE | BPF_K:
/* test dst_reg, dst_reg to save one extra byte */
if (imm32 == 0) {
maybe_emit_mod(&prog, dst_reg, dst_reg,
BPF_CLASS(insn->code) == BPF_JMP);
EMIT2(0x85, add_2reg(0xC0, dst_reg, dst_reg));
goto emit_cond_jmp;
}
/* cmp dst_reg, imm8/32 */
maybe_emit_1mod(&prog, dst_reg,
BPF_CLASS(insn->code) == BPF_JMP);
if (is_imm8(imm32))
EMIT3(0x83, add_1reg(0xF8, dst_reg), imm32);
else
EMIT2_off32(0x81, add_1reg(0xF8, dst_reg), imm32);
emit_cond_jmp: /* Convert BPF opcode to x86 */
switch (BPF_OP(insn->code)) {
case BPF_JEQ:
jmp_cond = X86_JE;
break;
case BPF_JSET:
case BPF_JNE:
jmp_cond = X86_JNE;
break;
case BPF_JGT:
/* GT is unsigned '>', JA in x86 */
jmp_cond = X86_JA;
break;
case BPF_JLT:
/* LT is unsigned '<', JB in x86 */
jmp_cond = X86_JB;
break;
case BPF_JGE:
/* GE is unsigned '>=', JAE in x86 */
jmp_cond = X86_JAE;
break;
case BPF_JLE:
/* LE is unsigned '<=', JBE in x86 */
jmp_cond = X86_JBE;
break;
case BPF_JSGT:
/* Signed '>', GT in x86 */
jmp_cond = X86_JG;
break;
case BPF_JSLT:
/* Signed '<', LT in x86 */
jmp_cond = X86_JL;
break;
case BPF_JSGE:
/* Signed '>=', GE in x86 */
jmp_cond = X86_JGE;
break;
case BPF_JSLE:
/* Signed '<=', LE in x86 */
jmp_cond = X86_JLE;
break;
default: /* to silence GCC warning */
return -EFAULT;
}
jmp_offset = addrs[i + insn->off] - addrs[i];
if (is_imm8(jmp_offset)) {
if (jmp_padding) {
/* To keep the jmp_offset valid, the extra bytes are
* padded before the jump insn, so we subtract the
* 2 bytes of jmp_cond insn from INSN_SZ_DIFF.
*
* If the previous pass already emits an imm8
* jmp_cond, then this BPF insn won't shrink, so
* "nops" is 0.
*
* On the other hand, if the previous pass emits an
* imm32 jmp_cond, the extra 4 bytes(*) is padded to
* keep the image from shrinking further.
*
* (*) imm32 jmp_cond is 6 bytes, and imm8 jmp_cond
* is 2 bytes, so the size difference is 4 bytes.
*/
nops = INSN_SZ_DIFF - 2;
if (nops != 0 && nops != 4) {
pr_err("unexpected jmp_cond padding: %d bytes\n",
nops);
return -EFAULT;
}
emit_nops(&prog, nops);
}
EMIT2(jmp_cond, jmp_offset);
} else if (is_simm32(jmp_offset)) {
EMIT2_off32(0x0F, jmp_cond + 0x10, jmp_offset);
} else {
pr_err("cond_jmp gen bug %llx\n", jmp_offset);
return -EFAULT;
}
break;
case BPF_JMP | BPF_JA:
if (insn->off == -1)
/* -1 jmp instructions will always jump
* backwards two bytes. Explicitly handling
* this case avoids wasting too many passes
* when there are long sequences of replaced
* dead code.
*/
jmp_offset = -2;
else
jmp_offset = addrs[i + insn->off] - addrs[i];
if (!jmp_offset) {
/*
* If jmp_padding is enabled, the extra nops will
* be inserted. Otherwise, optimize out nop jumps.
*/
if (jmp_padding) {
/* There are 3 possible conditions.
* (1) This BPF_JA is already optimized out in
* the previous run, so there is no need
* to pad any extra byte (0 byte).
* (2) The previous pass emits an imm8 jmp,
* so we pad 2 bytes to match the previous
* insn size.
* (3) Similarly, the previous pass emits an
* imm32 jmp, and 5 bytes is padded.
*/
nops = INSN_SZ_DIFF;
if (nops != 0 && nops != 2 && nops != 5) {
pr_err("unexpected nop jump padding: %d bytes\n",
nops);
return -EFAULT;
}
emit_nops(&prog, nops);
}
break;
}
emit_jmp:
if (is_imm8(jmp_offset)) {
if (jmp_padding) {
/* To avoid breaking jmp_offset, the extra bytes
* are padded before the actual jmp insn, so
* 2 bytes is subtracted from INSN_SZ_DIFF.
*
* If the previous pass already emits an imm8
* jmp, there is nothing to pad (0 byte).
*
* If it emits an imm32 jmp (5 bytes) previously
* and now an imm8 jmp (2 bytes), then we pad
* (5 - 2 = 3) bytes to stop the image from
* shrinking further.
*/
nops = INSN_SZ_DIFF - 2;
if (nops != 0 && nops != 3) {
pr_err("unexpected jump padding: %d bytes\n",
nops);
return -EFAULT;
}
emit_nops(&prog, INSN_SZ_DIFF - 2);
}
EMIT2(0xEB, jmp_offset);
} else if (is_simm32(jmp_offset)) {
EMIT1_off32(0xE9, jmp_offset);
} else {
pr_err("jmp gen bug %llx\n", jmp_offset);
return -EFAULT;
}
break;
case BPF_JMP | BPF_EXIT:
if (seen_exit) {
jmp_offset = ctx->cleanup_addr - addrs[i];
goto emit_jmp;
}
seen_exit = true;
/* Update cleanup_addr */
ctx->cleanup_addr = proglen;
pop_callee_regs(&prog, callee_regs_used);
EMIT1(0xC9); /* leave */
emit_return(&prog, image + addrs[i - 1] + (prog - temp));
break;
default:
/*
* By design x86-64 JIT should support all BPF instructions.
* This error will be seen if new instruction was added
* 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;
}
ilen = prog - temp;
if (ilen > BPF_MAX_INSN_SIZE) {
pr_err("bpf_jit: fatal insn size error\n");
return -EFAULT;
}
if (image) {
/*
* When populating the image, assert that:
*
* i) We do not write beyond the allocated space, and
* ii) addrs[i] did not change from the prior run, in order
* to validate assumptions made for computing branch
* displacements.
*/
if (unlikely(proglen + ilen > oldproglen ||
proglen + ilen != addrs[i])) {
pr_err("bpf_jit: fatal error\n");
return -EFAULT;
}
memcpy(rw_image + proglen, temp, ilen);
}
proglen += ilen;
addrs[i] = proglen;
prog = temp;
}
if (image && excnt != bpf_prog->aux->num_exentries) {
pr_err("extable is not populated\n");
return -EFAULT;
}
return proglen;
}
static void save_regs(const struct btf_func_model *m, u8 **prog, int nr_args,
int stack_size)
{
int i;
/* Store function arguments to stack.
* For a function that accepts two pointers the sequence will be:
* mov QWORD PTR [rbp-0x10],rdi
* mov QWORD PTR [rbp-0x8],rsi
*/
for (i = 0; i < min(nr_args, 6); i++)
emit_stx(prog, bytes_to_bpf_size(m->arg_size[i]),
BPF_REG_FP,
i == 5 ? X86_REG_R9 : BPF_REG_1 + i,
-(stack_size - i * 8));
}
static void restore_regs(const struct btf_func_model *m, u8 **prog, int nr_args,
int stack_size)
{
int i;
/* Restore function arguments from stack.
* For a function that accepts two pointers the sequence will be:
* EMIT4(0x48, 0x8B, 0x7D, 0xF0); mov rdi,QWORD PTR [rbp-0x10]
* EMIT4(0x48, 0x8B, 0x75, 0xF8); mov rsi,QWORD PTR [rbp-0x8]
*/
for (i = 0; i < min(nr_args, 6); i++)
emit_ldx(prog, bytes_to_bpf_size(m->arg_size[i]),
i == 5 ? X86_REG_R9 : BPF_REG_1 + i,
BPF_REG_FP,
-(stack_size - i * 8));
}
static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,
struct bpf_tramp_link *l, int stack_size,
int run_ctx_off, bool save_ret)
{
u8 *prog = *pprog;
u8 *jmp_insn;
int ctx_cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);
struct bpf_prog *p = l->link.prog;
u64 cookie = l->cookie;
/* mov rdi, cookie */
emit_mov_imm64(&prog, BPF_REG_1, (long) cookie >> 32, (u32) (long) cookie);
/* Prepare struct bpf_tramp_run_ctx.
*
* bpf_tramp_run_ctx is already preserved by
* arch_prepare_bpf_trampoline().
*
* mov QWORD PTR [rbp - run_ctx_off + ctx_cookie_off], rdi
*/
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_1, -run_ctx_off + ctx_cookie_off);
/* arg1: mov rdi, progs[i] */
emit_mov_imm64(&prog, BPF_REG_1, (long) p >> 32, (u32) (long) p);
/* arg2: lea rsi, [rbp - ctx_cookie_off] */
EMIT4(0x48, 0x8D, 0x75, -run_ctx_off);
if (emit_call(&prog,
p->aux->sleepable ? __bpf_prog_enter_sleepable :
__bpf_prog_enter, prog))
return -EINVAL;
/* remember prog start time returned by __bpf_prog_enter */
emit_mov_reg(&prog, true, BPF_REG_6, BPF_REG_0);
/* if (__bpf_prog_enter*(prog) == 0)
* goto skip_exec_of_prog;
*/
EMIT3(0x48, 0x85, 0xC0); /* test rax,rax */
/* emit 2 nops that will be replaced with JE insn */
jmp_insn = prog;
emit_nops(&prog, 2);
/* arg1: lea rdi, [rbp - stack_size] */
EMIT4(0x48, 0x8D, 0x7D, -stack_size);
/* arg2: progs[i]->insnsi for interpreter */
if (!p->jited)
emit_mov_imm64(&prog, BPF_REG_2,
(long) p->insnsi >> 32,
(u32) (long) p->insnsi);
/* call JITed bpf program or interpreter */
if (emit_call(&prog, p->bpf_func, prog))
return -EINVAL;
/*
* BPF_TRAMP_MODIFY_RETURN trampolines can modify the return
* of the previous call which is then passed on the stack to
* the next BPF program.
*
* BPF_TRAMP_FENTRY trampoline may need to return the return
* value of BPF_PROG_TYPE_STRUCT_OPS prog.
*/
if (save_ret)
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
/* replace 2 nops with JE insn, since jmp target is known */
jmp_insn[0] = X86_JE;
jmp_insn[1] = prog - jmp_insn - 2;
/* arg1: mov rdi, progs[i] */
emit_mov_imm64(&prog, BPF_REG_1, (long) p >> 32, (u32) (long) p);
/* arg2: mov rsi, rbx <- start time in nsec */
emit_mov_reg(&prog, true, BPF_REG_2, BPF_REG_6);
/* arg3: lea rdx, [rbp - run_ctx_off] */
EMIT4(0x48, 0x8D, 0x55, -run_ctx_off);
if (emit_call(&prog,
p->aux->sleepable ? __bpf_prog_exit_sleepable :
__bpf_prog_exit, prog))
return -EINVAL;
*pprog = prog;
return 0;
}
static void emit_align(u8 **pprog, u32 align)
{
u8 *target, *prog = *pprog;
target = PTR_ALIGN(prog, align);
if (target != prog)
emit_nops(&prog, target - prog);
*pprog = prog;
}
static int emit_cond_near_jump(u8 **pprog, void *func, void *ip, u8 jmp_cond)
{
u8 *prog = *pprog;
s64 offset;
offset = func - (ip + 2 + 4);
if (!is_simm32(offset)) {
pr_err("Target %p is out of range\n", func);
return -EINVAL;
}
EMIT2_off32(0x0F, jmp_cond + 0x10, offset);
*pprog = prog;
return 0;
}
static int invoke_bpf(const struct btf_func_model *m, u8 **pprog,
struct bpf_tramp_links *tl, int stack_size,
int run_ctx_off, bool save_ret)
{
int i;
u8 *prog = *pprog;
for (i = 0; i < tl->nr_links; i++) {
if (invoke_bpf_prog(m, &prog, tl->links[i], stack_size,
run_ctx_off, save_ret))
return -EINVAL;
}
*pprog = prog;
return 0;
}
static int invoke_bpf_mod_ret(const struct btf_func_model *m, u8 **pprog,
struct bpf_tramp_links *tl, int stack_size,
int run_ctx_off, u8 **branches)
{
u8 *prog = *pprog;
int i;
/* The first fmod_ret program will receive a garbage return value.
* Set this to 0 to avoid confusing the program.
*/
emit_mov_imm32(&prog, false, BPF_REG_0, 0);
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
for (i = 0; i < tl->nr_links; i++) {
if (invoke_bpf_prog(m, &prog, tl->links[i], stack_size, run_ctx_off, true))
return -EINVAL;
/* mod_ret prog stored return value into [rbp - 8]. Emit:
* if (*(u64 *)(rbp - 8) != 0)
* goto do_fexit;
*/
/* cmp QWORD PTR [rbp - 0x8], 0x0 */
EMIT4(0x48, 0x83, 0x7d, 0xf8); EMIT1(0x00);
/* Save the location of the branch and Generate 6 nops
* (4 bytes for an offset and 2 bytes for the jump) These nops
* are replaced with a conditional jump once do_fexit (i.e. the
* start of the fexit invocation) is finalized.
*/
branches[i] = prog;
emit_nops(&prog, 4 + 2);
}
*pprog = prog;
return 0;
}
static bool is_valid_bpf_tramp_flags(unsigned int flags)
{
if ((flags & BPF_TRAMP_F_RESTORE_REGS) &&
(flags & BPF_TRAMP_F_SKIP_FRAME))
return false;
/*
* BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops,
* and it must be used alone.
*/
if ((flags & BPF_TRAMP_F_RET_FENTRY_RET) &&
(flags & ~BPF_TRAMP_F_RET_FENTRY_RET))
return false;
return true;
}
/* Example:
* __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev);
* its 'struct btf_func_model' will be nr_args=2
* The assembly code when eth_type_trans is executing after trampoline:
*
* push rbp
* mov rbp, rsp
* sub rsp, 16 // space for skb and dev
* push rbx // temp regs to pass start time
* mov qword ptr [rbp - 16], rdi // save skb pointer to stack
* mov qword ptr [rbp - 8], rsi // save dev pointer to stack
* call __bpf_prog_enter // rcu_read_lock and preempt_disable
* mov rbx, rax // remember start time in bpf stats are enabled
* lea rdi, [rbp - 16] // R1==ctx of bpf prog
* call addr_of_jited_FENTRY_prog
* movabsq rdi, 64bit_addr_of_struct_bpf_prog // unused if bpf stats are off
* mov rsi, rbx // prog start time
* call __bpf_prog_exit // rcu_read_unlock, preempt_enable and stats math
* mov rdi, qword ptr [rbp - 16] // restore skb pointer from stack
* mov rsi, qword ptr [rbp - 8] // restore dev pointer from stack
* pop rbx
* leave
* ret
*
* eth_type_trans has 5 byte nop at the beginning. These 5 bytes will be
* replaced with 'call generated_bpf_trampoline'. When it returns
* eth_type_trans will continue executing with original skb and dev pointers.
*
* The assembly code when eth_type_trans is called from trampoline:
*
* push rbp
* mov rbp, rsp
* sub rsp, 24 // space for skb, dev, return value
* push rbx // temp regs to pass start time
* mov qword ptr [rbp - 24], rdi // save skb pointer to stack
* mov qword ptr [rbp - 16], rsi // save dev pointer to stack
* call __bpf_prog_enter // rcu_read_lock and preempt_disable
* mov rbx, rax // remember start time if bpf stats are enabled
* lea rdi, [rbp - 24] // R1==ctx of bpf prog
* call addr_of_jited_FENTRY_prog // bpf prog can access skb and dev
* movabsq rdi, 64bit_addr_of_struct_bpf_prog // unused if bpf stats are off
* mov rsi, rbx // prog start time
* call __bpf_prog_exit // rcu_read_unlock, preempt_enable and stats math
* mov rdi, qword ptr [rbp - 24] // restore skb pointer from stack
* mov rsi, qword ptr [rbp - 16] // restore dev pointer from stack
* call eth_type_trans+5 // execute body of eth_type_trans
* mov qword ptr [rbp - 8], rax // save return value
* call __bpf_prog_enter // rcu_read_lock and preempt_disable
* mov rbx, rax // remember start time in bpf stats are enabled
* lea rdi, [rbp - 24] // R1==ctx of bpf prog
* call addr_of_jited_FEXIT_prog // bpf prog can access skb, dev, return value
* movabsq rdi, 64bit_addr_of_struct_bpf_prog // unused if bpf stats are off
* mov rsi, rbx // prog start time
* call __bpf_prog_exit // rcu_read_unlock, preempt_enable and stats math
* mov rax, qword ptr [rbp - 8] // restore eth_type_trans's return value
* pop rbx
* leave
* add rsp, 8 // skip eth_type_trans's frame
* ret // return to its caller
*/
int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *image_end,
const struct btf_func_model *m, u32 flags,
struct bpf_tramp_links *tlinks,
void *orig_call)
{
int ret, i, nr_args = m->nr_args;
int regs_off, ip_off, args_off, stack_size = nr_args * 8, run_ctx_off;
struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY];
struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT];
struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN];
u8 **branches = NULL;
u8 *prog;
bool save_ret;
/* x86-64 supports up to 6 arguments. 7+ can be added in the future */
if (nr_args > 6)
return -ENOTSUPP;
if (!is_valid_bpf_tramp_flags(flags))
return -EINVAL;
/* Generated trampoline stack layout:
*
* RBP + 8 [ return address ]
* RBP + 0 [ RBP ]
*
* RBP - 8 [ return value ] BPF_TRAMP_F_CALL_ORIG or
* BPF_TRAMP_F_RET_FENTRY_RET flags
*
* [ reg_argN ] always
* [ ... ]
* RBP - regs_off [ reg_arg1 ] program's ctx pointer
*
* RBP - args_off [ args count ] always
*
* RBP - ip_off [ traced function ] BPF_TRAMP_F_IP_ARG flag
*
* RBP - run_ctx_off [ bpf_tramp_run_ctx ]
*/
/* room for return value of orig_call or fentry prog */
save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET);
if (save_ret)
stack_size += 8;
regs_off = stack_size;
/* args count */
stack_size += 8;
args_off = stack_size;
if (flags & BPF_TRAMP_F_IP_ARG)
stack_size += 8; /* room for IP address argument */
ip_off = stack_size;
stack_size += (sizeof(struct bpf_tramp_run_ctx) + 7) & ~0x7;
run_ctx_off = stack_size;
if (flags & BPF_TRAMP_F_SKIP_FRAME) {
/* skip patched call instruction and point orig_call to actual
* body of the kernel function.
*/
if (is_endbr(*(u32 *)orig_call))
orig_call += ENDBR_INSN_SIZE;
orig_call += X86_PATCH_SIZE;
}
prog = image;
EMIT_ENDBR();
EMIT1(0x55); /* push rbp */
EMIT3(0x48, 0x89, 0xE5); /* mov rbp, rsp */
EMIT4(0x48, 0x83, 0xEC, stack_size); /* sub rsp, stack_size */
EMIT1(0x53); /* push rbx */
/* Store number of arguments of the traced function:
* mov rax, nr_args
* mov QWORD PTR [rbp - args_off], rax
*/
emit_mov_imm64(&prog, BPF_REG_0, 0, (u32) nr_args);
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -args_off);
if (flags & BPF_TRAMP_F_IP_ARG) {
/* Store IP address of the traced function:
* mov rax, QWORD PTR [rbp + 8]
* sub rax, X86_PATCH_SIZE
* mov QWORD PTR [rbp - ip_off], rax
*/
emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8);
EMIT4(0x48, 0x83, 0xe8, X86_PATCH_SIZE);
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -ip_off);
}
save_regs(m, &prog, nr_args, regs_off);
if (flags & BPF_TRAMP_F_CALL_ORIG) {
/* arg1: mov rdi, im */
emit_mov_imm64(&prog, BPF_REG_1, (long) im >> 32, (u32) (long) im);
if (emit_call(&prog, __bpf_tramp_enter, prog)) {
ret = -EINVAL;
goto cleanup;
}
}
if (fentry->nr_links)
if (invoke_bpf(m, &prog, fentry, regs_off, run_ctx_off,
flags & BPF_TRAMP_F_RET_FENTRY_RET))
return -EINVAL;
if (fmod_ret->nr_links) {
branches = kcalloc(fmod_ret->nr_links, sizeof(u8 *),
GFP_KERNEL);
if (!branches)
return -ENOMEM;
if (invoke_bpf_mod_ret(m, &prog, fmod_ret, regs_off,
run_ctx_off, branches)) {
ret = -EINVAL;
goto cleanup;
}
}
if (flags & BPF_TRAMP_F_CALL_ORIG) {
restore_regs(m, &prog, nr_args, regs_off);
/* call original function */
if (emit_call(&prog, orig_call, prog)) {
ret = -EINVAL;
goto cleanup;
}
/* remember return value in a stack for bpf prog to access */
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
im->ip_after_call = prog;
memcpy(prog, x86_nops[5], X86_PATCH_SIZE);
prog += X86_PATCH_SIZE;
}
if (fmod_ret->nr_links) {
/* From Intel 64 and IA-32 Architectures Optimization
* Reference Manual, 3.4.1.4 Code Alignment, Assembly/Compiler
* Coding Rule 11: All branch targets should be 16-byte
* aligned.
*/
emit_align(&prog, 16);
/* Update the branches saved in invoke_bpf_mod_ret with the
* aligned address of do_fexit.
*/
for (i = 0; i < fmod_ret->nr_links; i++)
emit_cond_near_jump(&branches[i], prog, branches[i],
X86_JNE);
}
if (fexit->nr_links)
if (invoke_bpf(m, &prog, fexit, regs_off, run_ctx_off, false)) {
ret = -EINVAL;
goto cleanup;
}
if (flags & BPF_TRAMP_F_RESTORE_REGS)
restore_regs(m, &prog, nr_args, regs_off);
/* This needs to be done regardless. If there were fmod_ret programs,
* the return value is only updated on the stack and still needs to be
* restored to R0.
*/
if (flags & BPF_TRAMP_F_CALL_ORIG) {
im->ip_epilogue = prog;
/* arg1: mov rdi, im */
emit_mov_imm64(&prog, BPF_REG_1, (long) im >> 32, (u32) (long) im);
if (emit_call(&prog, __bpf_tramp_exit, prog)) {
ret = -EINVAL;
goto cleanup;
}
}
/* restore return value of orig_call or fentry prog back into RAX */
if (save_ret)
emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -8);
EMIT1(0x5B); /* pop rbx */
EMIT1(0xC9); /* leave */
if (flags & BPF_TRAMP_F_SKIP_FRAME)
/* skip our return address and return to parent */
EMIT4(0x48, 0x83, 0xC4, 8); /* add rsp, 8 */
emit_return(&prog, prog);
/* Make sure the trampoline generation logic doesn't overflow */
if (WARN_ON_ONCE(prog > (u8 *)image_end - BPF_INSN_SAFETY)) {
ret = -EFAULT;
goto cleanup;
}
ret = prog - (u8 *)image;
cleanup:
kfree(branches);
return ret;
}
static int emit_bpf_dispatcher(u8 **pprog, int a, int b, s64 *progs)
{
u8 *jg_reloc, *prog = *pprog;
int pivot, err, jg_bytes = 1;
s64 jg_offset;
if (a == b) {
/* Leaf node of recursion, i.e. not a range of indices
* anymore.
*/
EMIT1(add_1mod(0x48, BPF_REG_3)); /* cmp rdx,func */
if (!is_simm32(progs[a]))
return -1;
EMIT2_off32(0x81, add_1reg(0xF8, BPF_REG_3),
progs[a]);
err = emit_cond_near_jump(&prog, /* je func */
(void *)progs[a], prog,
X86_JE);
if (err)
return err;
emit_indirect_jump(&prog, 2 /* rdx */, prog);
*pprog = prog;
return 0;
}
/* Not a leaf node, so we pivot, and recursively descend into
* the lower and upper ranges.
*/
pivot = (b - a) / 2;
EMIT1(add_1mod(0x48, BPF_REG_3)); /* cmp rdx,func */
if (!is_simm32(progs[a + pivot]))
return -1;
EMIT2_off32(0x81, add_1reg(0xF8, BPF_REG_3), progs[a + pivot]);
if (pivot > 2) { /* jg upper_part */
/* Require near jump. */
jg_bytes = 4;
EMIT2_off32(0x0F, X86_JG + 0x10, 0);
} else {
EMIT2(X86_JG, 0);
}
jg_reloc = prog;
err = emit_bpf_dispatcher(&prog, a, a + pivot, /* emit lower_part */
progs);
if (err)
return err;
/* From Intel 64 and IA-32 Architectures Optimization
* Reference Manual, 3.4.1.4 Code Alignment, Assembly/Compiler
* Coding Rule 11: All branch targets should be 16-byte
* aligned.
*/
emit_align(&prog, 16);
jg_offset = prog - jg_reloc;
emit_code(jg_reloc - jg_bytes, jg_offset, jg_bytes);
err = emit_bpf_dispatcher(&prog, a + pivot + 1, /* emit upper_part */
b, progs);
if (err)
return err;
*pprog = prog;
return 0;
}
static int cmp_ips(const void *a, const void *b)
{
const s64 *ipa = a;
const s64 *ipb = b;
if (*ipa > *ipb)
return 1;
if (*ipa < *ipb)
return -1;
return 0;
}
int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs)
{
u8 *prog = image;
sort(funcs, num_funcs, sizeof(funcs[0]), cmp_ips, NULL);
return emit_bpf_dispatcher(&prog, 0, num_funcs - 1, funcs);
}
struct x64_jit_data {
struct bpf_binary_header *rw_header;
struct bpf_binary_header *header;
int *addrs;
u8 *image;
int proglen;
struct jit_context ctx;
};
#define MAX_PASSES 20
#define PADDING_PASSES (MAX_PASSES - 5)
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
{
struct bpf_binary_header *rw_header = NULL;
struct bpf_binary_header *header = NULL;
struct bpf_prog *tmp, *orig_prog = prog;
struct x64_jit_data *jit_data;
int proglen, oldproglen = 0;
struct jit_context ctx = {};
bool tmp_blinded = false;
bool extra_pass = false;
bool padding = false;
u8 *rw_image = NULL;
u8 *image = NULL;
int *addrs;
int pass;
int i;
if (!prog->jit_requested)
return orig_prog;
tmp = bpf_jit_blind_constants(prog);
/*
* If blinding was requested and we failed during blinding,
* we must fall back to the interpreter.
*/
if (IS_ERR(tmp))
return orig_prog;
if (tmp != prog) {
tmp_blinded = true;
prog = tmp;
}
jit_data = prog->aux->jit_data;
if (!jit_data) {
jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
if (!jit_data) {
prog = orig_prog;
goto out;
}
prog->aux->jit_data = jit_data;
}
addrs = jit_data->addrs;
if (addrs) {
ctx = jit_data->ctx;
oldproglen = jit_data->proglen;
image = jit_data->image;
header = jit_data->header;
rw_header = jit_data->rw_header;
rw_image = (void *)rw_header + ((void *)image - (void *)header);
extra_pass = true;
padding = true;
goto skip_init_addrs;
}
addrs = kvmalloc_array(prog->len + 1, sizeof(*addrs), GFP_KERNEL);
if (!addrs) {
prog = orig_prog;
goto out_addrs;
}
/*
* 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;
addrs[i] = proglen;
}
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
* may converge on the last pass. In such case do one more
* pass to emit the final image.
*/
for (pass = 0; pass < MAX_PASSES || image; pass++) {
if (!padding && pass >= PADDING_PASSES)
padding = true;
proglen = do_jit(prog, addrs, image, rw_image, oldproglen, &ctx, padding);
if (proglen <= 0) {
out_image:
image = NULL;
if (header) {
bpf_arch_text_copy(&header->size, &rw_header->size,
sizeof(rw_header->size));
bpf_jit_binary_pack_free(header, rw_header);
}
/* Fall back to interpreter mode */
prog = orig_prog;
if (extra_pass) {
prog->bpf_func = NULL;
prog->jited = 0;
prog->jited_len = 0;
}
goto out_addrs;
}
if (image) {
if (proglen != oldproglen) {
pr_err("bpf_jit: proglen=%d != oldproglen=%d\n",
proglen, oldproglen);
goto out_image;
}
break;
}
if (proglen == oldproglen) {
/*
* The number of entries in extable is the number of BPF_LDX
* insns that access kernel memory via "pointer to BTF type".
* The verifier changed their opcode from LDX|MEM|size
* to LDX|PROBE_MEM|size to make JITing easier.
*/
u32 align = __alignof__(struct exception_table_entry);
u32 extable_size = prog->aux->num_exentries *
sizeof(struct exception_table_entry);
/* allocate module memory for x86 insns and extable */
header = bpf_jit_binary_pack_alloc(roundup(proglen, align) + extable_size,
&image, align, &rw_header, &rw_image,
jit_fill_hole);
if (!header) {
prog = orig_prog;
goto out_addrs;
}
prog->aux->extable = (void *) image + roundup(proglen, align);
}
oldproglen = proglen;
cond_resched();
}
if (bpf_jit_enable > 1)
bpf_jit_dump(prog->len, proglen, pass + 1, image);
if (image) {
if (!prog->is_func || extra_pass) {
/*
* bpf_jit_binary_pack_finalize fails in two scenarios:
* 1) header is not pointing to proper module memory;
* 2) the arch doesn't support bpf_arch_text_copy().
*
* Both cases are serious bugs and justify WARN_ON.
*/
if (WARN_ON(bpf_jit_binary_pack_finalize(prog, header, rw_header))) {
/* header has been freed */
header = NULL;
goto out_image;
}
bpf_tail_call_direct_fixup(prog);
} else {
jit_data->addrs = addrs;
jit_data->ctx = ctx;
jit_data->proglen = proglen;
jit_data->image = image;
jit_data->header = header;
jit_data->rw_header = rw_header;
}
prog->bpf_func = (void *)image;
prog->jited = 1;
prog->jited_len = proglen;
} else {
prog = orig_prog;
}
if (!image || !prog->is_func || extra_pass) {
if (image)
bpf_prog_fill_jited_linfo(prog, addrs + 1);
out_addrs:
kvfree(addrs);
kfree(jit_data);
prog->aux->jit_data = NULL;
}
out:
if (tmp_blinded)
bpf_jit_prog_release_other(prog, prog == orig_prog ?
tmp : orig_prog);
return prog;
}
bool bpf_jit_supports_kfunc_call(void)
{
return true;
}
void *bpf_arch_text_copy(void *dst, void *src, size_t len)
{
if (text_poke_copy(dst, src, len) == NULL)
return ERR_PTR(-EINVAL);
return dst;
}
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