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linux-zen-desktop/arch/arm64/net/bpf_jit_comp.c

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Initial commit
2023-08-30 17:31:07 +02:00
// SPDX-License-Identifier: GPL-2.0-only
/*
* BPF JIT compiler for ARM64
*
* Copyright (C) 2014-2016 Zi Shen Lim <zlim.lnx@gmail.com>
*/
#define pr_fmt(fmt) "bpf_jit: " fmt
#include <linux/bitfield.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/memory.h>
#include <linux/printk.h>
#include <linux/slab.h>
#include <asm/asm-extable.h>
#include <asm/byteorder.h>
#include <asm/cacheflush.h>
#include <asm/debug-monitors.h>
#include <asm/insn.h>
#include <asm/patching.h>
#include <asm/set_memory.h>
#include "bpf_jit.h"
#define TMP_REG_1 (MAX_BPF_JIT_REG + 0)
#define TMP_REG_2 (MAX_BPF_JIT_REG + 1)
#define TCALL_CNT (MAX_BPF_JIT_REG + 2)
#define TMP_REG_3 (MAX_BPF_JIT_REG + 3)
#define FP_BOTTOM (MAX_BPF_JIT_REG + 4)
#define check_imm(bits, imm) do { \
if ((((imm) > 0) && ((imm) >> (bits))) || \
(((imm) < 0) && (~(imm) >> (bits)))) { \
pr_info("[%2d] imm=%d(0x%x) out of range\n", \
i, imm, imm); \
return -EINVAL; \
} \
} while (0)
#define check_imm19(imm) check_imm(19, imm)
#define check_imm26(imm) check_imm(26, imm)
/* Map BPF registers to A64 registers */
static const int bpf2a64[] = {
/* return value from in-kernel function, and exit value from eBPF */
[BPF_REG_0] = A64_R(7),
/* arguments from eBPF program to in-kernel function */
[BPF_REG_1] = A64_R(0),
[BPF_REG_2] = A64_R(1),
[BPF_REG_3] = A64_R(2),
[BPF_REG_4] = A64_R(3),
[BPF_REG_5] = A64_R(4),
/* callee saved registers that in-kernel function will preserve */
[BPF_REG_6] = A64_R(19),
[BPF_REG_7] = A64_R(20),
[BPF_REG_8] = A64_R(21),
[BPF_REG_9] = A64_R(22),
/* read-only frame pointer to access stack */
[BPF_REG_FP] = A64_R(25),
/* temporary registers for BPF JIT */
[TMP_REG_1] = A64_R(10),
[TMP_REG_2] = A64_R(11),
[TMP_REG_3] = A64_R(12),
/* tail_call_cnt */
[TCALL_CNT] = A64_R(26),
/* temporary register for blinding constants */
[BPF_REG_AX] = A64_R(9),
[FP_BOTTOM] = A64_R(27),
};
struct jit_ctx {
const struct bpf_prog *prog;
int idx;
int epilogue_offset;
int *offset;
int exentry_idx;
__le32 *image;
u32 stack_size;
int fpb_offset;
};
struct bpf_plt {
u32 insn_ldr; /* load target */
u32 insn_br; /* branch to target */
u64 target; /* target value */
};
#define PLT_TARGET_SIZE sizeof_field(struct bpf_plt, target)
#define PLT_TARGET_OFFSET offsetof(struct bpf_plt, target)
static inline void emit(const u32 insn, struct jit_ctx *ctx)
{
if (ctx->image != NULL)
ctx->image[ctx->idx] = cpu_to_le32(insn);
ctx->idx++;
}
static inline void emit_a64_mov_i(const int is64, const int reg,
const s32 val, struct jit_ctx *ctx)
{
u16 hi = val >> 16;
u16 lo = val & 0xffff;
if (hi & 0x8000) {
if (hi == 0xffff) {
emit(A64_MOVN(is64, reg, (u16)~lo, 0), ctx);
} else {
emit(A64_MOVN(is64, reg, (u16)~hi, 16), ctx);
if (lo != 0xffff)
emit(A64_MOVK(is64, reg, lo, 0), ctx);
}
} else {
emit(A64_MOVZ(is64, reg, lo, 0), ctx);
if (hi)
emit(A64_MOVK(is64, reg, hi, 16), ctx);
}
}
static int i64_i16_blocks(const u64 val, bool inverse)
{
return (((val >> 0) & 0xffff) != (inverse ? 0xffff : 0x0000)) +
(((val >> 16) & 0xffff) != (inverse ? 0xffff : 0x0000)) +
(((val >> 32) & 0xffff) != (inverse ? 0xffff : 0x0000)) +
(((val >> 48) & 0xffff) != (inverse ? 0xffff : 0x0000));
}
static inline void emit_a64_mov_i64(const int reg, const u64 val,
struct jit_ctx *ctx)
{
u64 nrm_tmp = val, rev_tmp = ~val;
bool inverse;
int shift;
if (!(nrm_tmp >> 32))
return emit_a64_mov_i(0, reg, (u32)val, ctx);
inverse = i64_i16_blocks(nrm_tmp, true) < i64_i16_blocks(nrm_tmp, false);
shift = max(round_down((inverse ? (fls64(rev_tmp) - 1) :
(fls64(nrm_tmp) - 1)), 16), 0);
if (inverse)
emit(A64_MOVN(1, reg, (rev_tmp >> shift) & 0xffff, shift), ctx);
else
emit(A64_MOVZ(1, reg, (nrm_tmp >> shift) & 0xffff, shift), ctx);
shift -= 16;
while (shift >= 0) {
if (((nrm_tmp >> shift) & 0xffff) != (inverse ? 0xffff : 0x0000))
emit(A64_MOVK(1, reg, (nrm_tmp >> shift) & 0xffff, shift), ctx);
shift -= 16;
}
}
static inline void emit_bti(u32 insn, struct jit_ctx *ctx)
{
if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL))
emit(insn, ctx);
}
/*
* Kernel addresses in the vmalloc space use at most 48 bits, and the
* remaining bits are guaranteed to be 0x1. So we can compose the address
* with a fixed length movn/movk/movk sequence.
*/
static inline void emit_addr_mov_i64(const int reg, const u64 val,
struct jit_ctx *ctx)
{
u64 tmp = val;
int shift = 0;
emit(A64_MOVN(1, reg, ~tmp & 0xffff, shift), ctx);
while (shift < 32) {
tmp >>= 16;
shift += 16;
emit(A64_MOVK(1, reg, tmp & 0xffff, shift), ctx);
}
}
static inline void emit_call(u64 target, struct jit_ctx *ctx)
{
u8 tmp = bpf2a64[TMP_REG_1];
emit_addr_mov_i64(tmp, target, ctx);
emit(A64_BLR(tmp), ctx);
}
static inline int bpf2a64_offset(int bpf_insn, int off,
const struct jit_ctx *ctx)
{
/* BPF JMP offset is relative to the next instruction */
bpf_insn++;
/*
* Whereas arm64 branch instructions encode the offset
* from the branch itself, so we must subtract 1 from the
* instruction offset.
*/
return ctx->offset[bpf_insn + off] - (ctx->offset[bpf_insn] - 1);
}
static void jit_fill_hole(void *area, unsigned int size)
{
__le32 *ptr;
/* We are guaranteed to have aligned memory. */
for (ptr = area; size >= sizeof(u32); size -= sizeof(u32))
*ptr++ = cpu_to_le32(AARCH64_BREAK_FAULT);
}
static inline int epilogue_offset(const struct jit_ctx *ctx)
{
int to = ctx->epilogue_offset;
int from = ctx->idx;
return to - from;
}
static bool is_addsub_imm(u32 imm)
{
/* Either imm12 or shifted imm12. */
return !(imm & ~0xfff) || !(imm & ~0xfff000);
}
/*
* There are 3 types of AArch64 LDR/STR (immediate) instruction:
* Post-index, Pre-index, Unsigned offset.
*
* For BPF ldr/str, the "unsigned offset" type is sufficient.
*
* "Unsigned offset" type LDR(immediate) format:
*
* 3 2 1 0
* 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |x x|1 1 1 0 0 1 0 1| imm12 | Rn | Rt |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* scale
*
* "Unsigned offset" type STR(immediate) format:
* 3 2 1 0
* 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* |x x|1 1 1 0 0 1 0 0| imm12 | Rn | Rt |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* scale
*
* The offset is calculated from imm12 and scale in the following way:
*
* offset = (u64)imm12 << scale
*/
static bool is_lsi_offset(int offset, int scale)
{
if (offset < 0)
return false;
if (offset > (0xFFF << scale))
return false;
if (offset & ((1 << scale) - 1))
return false;
return true;
}
/* generated prologue:
* bti c // if CONFIG_ARM64_BTI_KERNEL
* mov x9, lr
* nop // POKE_OFFSET
* paciasp // if CONFIG_ARM64_PTR_AUTH_KERNEL
* stp x29, lr, [sp, #-16]!
* mov x29, sp
* stp x19, x20, [sp, #-16]!
* stp x21, x22, [sp, #-16]!
* stp x25, x26, [sp, #-16]!
* stp x27, x28, [sp, #-16]!
* mov x25, sp
* mov tcc, #0
* // PROLOGUE_OFFSET
*/
#define BTI_INSNS (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) ? 1 : 0)
#define PAC_INSNS (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL) ? 1 : 0)
/* Offset of nop instruction in bpf prog entry to be poked */
#define POKE_OFFSET (BTI_INSNS + 1)
/* Tail call offset to jump into */
#define PROLOGUE_OFFSET (BTI_INSNS + 2 + PAC_INSNS + 8)
static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf)
{
const struct bpf_prog *prog = ctx->prog;
const bool is_main_prog = prog->aux->func_idx == 0;
const u8 r6 = bpf2a64[BPF_REG_6];
const u8 r7 = bpf2a64[BPF_REG_7];
const u8 r8 = bpf2a64[BPF_REG_8];
const u8 r9 = bpf2a64[BPF_REG_9];
const u8 fp = bpf2a64[BPF_REG_FP];
const u8 tcc = bpf2a64[TCALL_CNT];
const u8 fpb = bpf2a64[FP_BOTTOM];
const int idx0 = ctx->idx;
int cur_offset;
/*
* BPF prog stack layout
*
* high
* original A64_SP => 0:+-----+ BPF prologue
* |FP/LR|
* current A64_FP => -16:+-----+
* | ... | callee saved registers
* BPF fp register => -64:+-----+ <= (BPF_FP)
* | |
* | ... | BPF prog stack
* | |
* +-----+ <= (BPF_FP - prog->aux->stack_depth)
* |RSVD | padding
* current A64_SP => +-----+ <= (BPF_FP - ctx->stack_size)
* | |
* | ... | Function call stack
* | |
* +-----+
* low
*
*/
6.5.5
2023-10-24 12:59:35 +02:00
/* bpf function may be invoked by 3 instruction types:
* 1. bl, attached via freplace to bpf prog via short jump
* 2. br, attached via freplace to bpf prog via long jump
* 3. blr, working as a function pointer, used by emit_call.
* So BTI_JC should used here to support both br and blr.
*/
emit_bti(A64_BTI_JC, ctx);
Initial commit
2023-08-30 17:31:07 +02:00
emit(A64_MOV(1, A64_R(9), A64_LR), ctx);
emit(A64_NOP, ctx);
/* Sign lr */
if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL))
emit(A64_PACIASP, ctx);
/* Save FP and LR registers to stay align with ARM64 AAPCS */
emit(A64_PUSH(A64_FP, A64_LR, A64_SP), ctx);
emit(A64_MOV(1, A64_FP, A64_SP), ctx);
/* Save callee-saved registers */
emit(A64_PUSH(r6, r7, A64_SP), ctx);
emit(A64_PUSH(r8, r9, A64_SP), ctx);
emit(A64_PUSH(fp, tcc, A64_SP), ctx);
emit(A64_PUSH(fpb, A64_R(28), A64_SP), ctx);
/* Set up BPF prog stack base register */
emit(A64_MOV(1, fp, A64_SP), ctx);
if (!ebpf_from_cbpf && is_main_prog) {
/* Initialize tail_call_cnt */
emit(A64_MOVZ(1, tcc, 0, 0), ctx);
cur_offset = ctx->idx - idx0;
if (cur_offset != PROLOGUE_OFFSET) {
pr_err_once("PROLOGUE_OFFSET = %d, expected %d!\n",
cur_offset, PROLOGUE_OFFSET);
return -1;
}
/* BTI landing pad for the tail call, done with a BR */
emit_bti(A64_BTI_J, ctx);
}
emit(A64_SUB_I(1, fpb, fp, ctx->fpb_offset), ctx);
/* Stack must be multiples of 16B */
ctx->stack_size = round_up(prog->aux->stack_depth, 16);
/* Set up function call stack */
emit(A64_SUB_I(1, A64_SP, A64_SP, ctx->stack_size), ctx);
return 0;
}
static int out_offset = -1; /* initialized on the first pass of build_body() */
static int emit_bpf_tail_call(struct jit_ctx *ctx)
{
/* bpf_tail_call(void *prog_ctx, struct bpf_array *array, u64 index) */
const u8 r2 = bpf2a64[BPF_REG_2];
const u8 r3 = bpf2a64[BPF_REG_3];
const u8 tmp = bpf2a64[TMP_REG_1];
const u8 prg = bpf2a64[TMP_REG_2];
const u8 tcc = bpf2a64[TCALL_CNT];
const int idx0 = ctx->idx;
#define cur_offset (ctx->idx - idx0)
#define jmp_offset (out_offset - (cur_offset))
size_t off;
/* if (index >= array->map.max_entries)
* goto out;
*/
off = offsetof(struct bpf_array, map.max_entries);
emit_a64_mov_i64(tmp, off, ctx);
emit(A64_LDR32(tmp, r2, tmp), ctx);
emit(A64_MOV(0, r3, r3), ctx);
emit(A64_CMP(0, r3, tmp), ctx);
emit(A64_B_(A64_COND_CS, jmp_offset), ctx);
/*
* if (tail_call_cnt >= MAX_TAIL_CALL_CNT)
* goto out;
* tail_call_cnt++;
*/
emit_a64_mov_i64(tmp, MAX_TAIL_CALL_CNT, ctx);
emit(A64_CMP(1, tcc, tmp), ctx);
emit(A64_B_(A64_COND_CS, jmp_offset), ctx);
emit(A64_ADD_I(1, tcc, tcc, 1), ctx);
/* prog = array->ptrs[index];
* if (prog == NULL)
* goto out;
*/
off = offsetof(struct bpf_array, ptrs);
emit_a64_mov_i64(tmp, off, ctx);
emit(A64_ADD(1, tmp, r2, tmp), ctx);
emit(A64_LSL(1, prg, r3, 3), ctx);
emit(A64_LDR64(prg, tmp, prg), ctx);
emit(A64_CBZ(1, prg, jmp_offset), ctx);
/* goto *(prog->bpf_func + prologue_offset); */
off = offsetof(struct bpf_prog, bpf_func);
emit_a64_mov_i64(tmp, off, ctx);
emit(A64_LDR64(tmp, prg, tmp), ctx);
emit(A64_ADD_I(1, tmp, tmp, sizeof(u32) * PROLOGUE_OFFSET), ctx);
emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_size), ctx);
emit(A64_BR(tmp), ctx);
/* out: */
if (out_offset == -1)
out_offset = cur_offset;
if (cur_offset != out_offset) {
pr_err_once("tail_call out_offset = %d, expected %d!\n",
cur_offset, out_offset);
return -1;
}
return 0;
#undef cur_offset
#undef jmp_offset
}
#ifdef CONFIG_ARM64_LSE_ATOMICS
static int emit_lse_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
{
const u8 code = insn->code;
const u8 dst = bpf2a64[insn->dst_reg];
const u8 src = bpf2a64[insn->src_reg];
const u8 tmp = bpf2a64[TMP_REG_1];
const u8 tmp2 = bpf2a64[TMP_REG_2];
const bool isdw = BPF_SIZE(code) == BPF_DW;
const s16 off = insn->off;
u8 reg;
if (!off) {
reg = dst;
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_ADD(1, tmp, tmp, dst), ctx);
reg = tmp;
}
switch (insn->imm) {
/* lock *(u32/u64 *)(dst_reg + off) <op>= src_reg */
case BPF_ADD:
emit(A64_STADD(isdw, reg, src), ctx);
break;
case BPF_AND:
emit(A64_MVN(isdw, tmp2, src), ctx);
emit(A64_STCLR(isdw, reg, tmp2), ctx);
break;
case BPF_OR:
emit(A64_STSET(isdw, reg, src), ctx);
break;
case BPF_XOR:
emit(A64_STEOR(isdw, reg, src), ctx);
break;
/* src_reg = atomic_fetch_<op>(dst_reg + off, src_reg) */
case BPF_ADD | BPF_FETCH:
emit(A64_LDADDAL(isdw, src, reg, src), ctx);
break;
case BPF_AND | BPF_FETCH:
emit(A64_MVN(isdw, tmp2, src), ctx);
emit(A64_LDCLRAL(isdw, src, reg, tmp2), ctx);
break;
case BPF_OR | BPF_FETCH:
emit(A64_LDSETAL(isdw, src, reg, src), ctx);
break;
case BPF_XOR | BPF_FETCH:
emit(A64_LDEORAL(isdw, src, reg, src), ctx);
break;
/* src_reg = atomic_xchg(dst_reg + off, src_reg); */
case BPF_XCHG:
emit(A64_SWPAL(isdw, src, reg, src), ctx);
break;
/* r0 = atomic_cmpxchg(dst_reg + off, r0, src_reg); */
case BPF_CMPXCHG:
emit(A64_CASAL(isdw, src, reg, bpf2a64[BPF_REG_0]), ctx);
break;
default:
pr_err_once("unknown atomic op code %02x\n", insn->imm);
return -EINVAL;
}
return 0;
}
#else
static inline int emit_lse_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
{
return -EINVAL;
}
#endif
static int emit_ll_sc_atomic(const struct bpf_insn *insn, struct jit_ctx *ctx)
{
const u8 code = insn->code;
const u8 dst = bpf2a64[insn->dst_reg];
const u8 src = bpf2a64[insn->src_reg];
const u8 tmp = bpf2a64[TMP_REG_1];
const u8 tmp2 = bpf2a64[TMP_REG_2];
const u8 tmp3 = bpf2a64[TMP_REG_3];
const int i = insn - ctx->prog->insnsi;
const s32 imm = insn->imm;
const s16 off = insn->off;
const bool isdw = BPF_SIZE(code) == BPF_DW;
u8 reg;
s32 jmp_offset;
if (!off) {
reg = dst;
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_ADD(1, tmp, tmp, dst), ctx);
reg = tmp;
}
if (imm == BPF_ADD || imm == BPF_AND ||
imm == BPF_OR || imm == BPF_XOR) {
/* lock *(u32/u64 *)(dst_reg + off) <op>= src_reg */
emit(A64_LDXR(isdw, tmp2, reg), ctx);
if (imm == BPF_ADD)
emit(A64_ADD(isdw, tmp2, tmp2, src), ctx);
else if (imm == BPF_AND)
emit(A64_AND(isdw, tmp2, tmp2, src), ctx);
else if (imm == BPF_OR)
emit(A64_ORR(isdw, tmp2, tmp2, src), ctx);
else
emit(A64_EOR(isdw, tmp2, tmp2, src), ctx);
emit(A64_STXR(isdw, tmp2, reg, tmp3), ctx);
jmp_offset = -3;
check_imm19(jmp_offset);
emit(A64_CBNZ(0, tmp3, jmp_offset), ctx);
} else if (imm == (BPF_ADD | BPF_FETCH) ||
imm == (BPF_AND | BPF_FETCH) ||
imm == (BPF_OR | BPF_FETCH) ||
imm == (BPF_XOR | BPF_FETCH)) {
/* src_reg = atomic_fetch_<op>(dst_reg + off, src_reg) */
const u8 ax = bpf2a64[BPF_REG_AX];
emit(A64_MOV(isdw, ax, src), ctx);
emit(A64_LDXR(isdw, src, reg), ctx);
if (imm == (BPF_ADD | BPF_FETCH))
emit(A64_ADD(isdw, tmp2, src, ax), ctx);
else if (imm == (BPF_AND | BPF_FETCH))
emit(A64_AND(isdw, tmp2, src, ax), ctx);
else if (imm == (BPF_OR | BPF_FETCH))
emit(A64_ORR(isdw, tmp2, src, ax), ctx);
else
emit(A64_EOR(isdw, tmp2, src, ax), ctx);
emit(A64_STLXR(isdw, tmp2, reg, tmp3), ctx);
jmp_offset = -3;
check_imm19(jmp_offset);
emit(A64_CBNZ(0, tmp3, jmp_offset), ctx);
emit(A64_DMB_ISH, ctx);
} else if (imm == BPF_XCHG) {
/* src_reg = atomic_xchg(dst_reg + off, src_reg); */
emit(A64_MOV(isdw, tmp2, src), ctx);
emit(A64_LDXR(isdw, src, reg), ctx);
emit(A64_STLXR(isdw, tmp2, reg, tmp3), ctx);
jmp_offset = -2;
check_imm19(jmp_offset);
emit(A64_CBNZ(0, tmp3, jmp_offset), ctx);
emit(A64_DMB_ISH, ctx);
} else if (imm == BPF_CMPXCHG) {
/* r0 = atomic_cmpxchg(dst_reg + off, r0, src_reg); */
const u8 r0 = bpf2a64[BPF_REG_0];
emit(A64_MOV(isdw, tmp2, r0), ctx);
emit(A64_LDXR(isdw, r0, reg), ctx);
emit(A64_EOR(isdw, tmp3, r0, tmp2), ctx);
jmp_offset = 4;
check_imm19(jmp_offset);
emit(A64_CBNZ(isdw, tmp3, jmp_offset), ctx);
emit(A64_STLXR(isdw, src, reg, tmp3), ctx);
jmp_offset = -4;
check_imm19(jmp_offset);
emit(A64_CBNZ(0, tmp3, jmp_offset), ctx);
emit(A64_DMB_ISH, ctx);
} else {
pr_err_once("unknown atomic op code %02x\n", imm);
return -EINVAL;
}
return 0;
}
void dummy_tramp(void);
asm (
" .pushsection .text, \"ax\", @progbits\n"
" .global dummy_tramp\n"
" .type dummy_tramp, %function\n"
"dummy_tramp:"
#if IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)
" bti j\n" /* dummy_tramp is called via "br x10" */
#endif
" mov x10, x30\n"
" mov x30, x9\n"
" ret x10\n"
" .size dummy_tramp, .-dummy_tramp\n"
" .popsection\n"
);
/* build a plt initialized like this:
*
* plt:
* ldr tmp, target
* br tmp
* target:
* .quad dummy_tramp
*
* when a long jump trampoline is attached, target is filled with the
* trampoline address, and when the trampoline is removed, target is
* restored to dummy_tramp address.
*/
static void build_plt(struct jit_ctx *ctx)
{
const u8 tmp = bpf2a64[TMP_REG_1];
struct bpf_plt *plt = NULL;
/* make sure target is 64-bit aligned */
if ((ctx->idx + PLT_TARGET_OFFSET / AARCH64_INSN_SIZE) % 2)
emit(A64_NOP, ctx);
plt = (struct bpf_plt *)(ctx->image + ctx->idx);
/* plt is called via bl, no BTI needed here */
emit(A64_LDR64LIT(tmp, 2 * AARCH64_INSN_SIZE), ctx);
emit(A64_BR(tmp), ctx);
if (ctx->image)
plt->target = (u64)&dummy_tramp;
}
static void build_epilogue(struct jit_ctx *ctx)
{
const u8 r0 = bpf2a64[BPF_REG_0];
const u8 r6 = bpf2a64[BPF_REG_6];
const u8 r7 = bpf2a64[BPF_REG_7];
const u8 r8 = bpf2a64[BPF_REG_8];
const u8 r9 = bpf2a64[BPF_REG_9];
const u8 fp = bpf2a64[BPF_REG_FP];
const u8 fpb = bpf2a64[FP_BOTTOM];
/* We're done with BPF stack */
emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_size), ctx);
/* Restore x27 and x28 */
emit(A64_POP(fpb, A64_R(28), A64_SP), ctx);
/* Restore fs (x25) and x26 */
emit(A64_POP(fp, A64_R(26), A64_SP), ctx);
/* Restore callee-saved register */
emit(A64_POP(r8, r9, A64_SP), ctx);
emit(A64_POP(r6, r7, A64_SP), ctx);
/* Restore FP/LR registers */
emit(A64_POP(A64_FP, A64_LR, A64_SP), ctx);
/* Set return value */
emit(A64_MOV(1, A64_R(0), r0), ctx);
/* Authenticate lr */
if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL))
emit(A64_AUTIASP, ctx);
emit(A64_RET(A64_LR), ctx);
}
#define BPF_FIXUP_OFFSET_MASK GENMASK(26, 0)
#define BPF_FIXUP_REG_MASK GENMASK(31, 27)
bool ex_handler_bpf(const struct exception_table_entry *ex,
struct pt_regs *regs)
{
off_t offset = FIELD_GET(BPF_FIXUP_OFFSET_MASK, ex->fixup);
int dst_reg = FIELD_GET(BPF_FIXUP_REG_MASK, ex->fixup);
regs->regs[dst_reg] = 0;
regs->pc = (unsigned long)&ex->fixup - offset;
return true;
}
/* For accesses to BTF pointers, add an entry to the exception table */
static int add_exception_handler(const struct bpf_insn *insn,
struct jit_ctx *ctx,
int dst_reg)
{
off_t offset;
unsigned long pc;
struct exception_table_entry *ex;
if (!ctx->image)
/* First pass */
return 0;
if (BPF_MODE(insn->code) != BPF_PROBE_MEM)
return 0;
if (!ctx->prog->aux->extable ||
WARN_ON_ONCE(ctx->exentry_idx >= ctx->prog->aux->num_exentries))
return -EINVAL;
ex = &ctx->prog->aux->extable[ctx->exentry_idx];
pc = (unsigned long)&ctx->image[ctx->idx - 1];
offset = pc - (long)&ex->insn;
if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
return -ERANGE;
ex->insn = offset;
/*
* Since the extable follows the program, the fixup offset is always
* negative and limited to BPF_JIT_REGION_SIZE. Store a positive value
* to keep things simple, and put the destination register in the upper
* bits. We don't need to worry about buildtime or runtime sort
* modifying the upper bits because the table is already sorted, and
* isn't part of the main exception table.
*/
offset = (long)&ex->fixup - (pc + AARCH64_INSN_SIZE);
if (!FIELD_FIT(BPF_FIXUP_OFFSET_MASK, offset))
return -ERANGE;
ex->fixup = FIELD_PREP(BPF_FIXUP_OFFSET_MASK, offset) |
FIELD_PREP(BPF_FIXUP_REG_MASK, dst_reg);
ex->type = EX_TYPE_BPF;
ctx->exentry_idx++;
return 0;
}
/* JITs an eBPF instruction.
* Returns:
* 0 - successfully JITed an 8-byte eBPF instruction.
* >0 - successfully JITed a 16-byte eBPF instruction.
* <0 - failed to JIT.
*/
static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
bool extra_pass)
{
const u8 code = insn->code;
const u8 dst = bpf2a64[insn->dst_reg];
const u8 src = bpf2a64[insn->src_reg];
const u8 tmp = bpf2a64[TMP_REG_1];
const u8 tmp2 = bpf2a64[TMP_REG_2];
const u8 fp = bpf2a64[BPF_REG_FP];
const u8 fpb = bpf2a64[FP_BOTTOM];
const s16 off = insn->off;
const s32 imm = insn->imm;
const int i = insn - ctx->prog->insnsi;
const bool is64 = BPF_CLASS(code) == BPF_ALU64 ||
BPF_CLASS(code) == BPF_JMP;
u8 jmp_cond;
s32 jmp_offset;
u32 a64_insn;
u8 src_adj;
u8 dst_adj;
int off_adj;
int ret;
switch (code) {
/* dst = src */
case BPF_ALU | BPF_MOV | BPF_X:
case BPF_ALU64 | BPF_MOV | BPF_X:
emit(A64_MOV(is64, dst, src), ctx);
break;
/* dst = dst OP src */
case BPF_ALU | BPF_ADD | BPF_X:
case BPF_ALU64 | BPF_ADD | BPF_X:
emit(A64_ADD(is64, dst, dst, src), ctx);
break;
case BPF_ALU | BPF_SUB | BPF_X:
case BPF_ALU64 | BPF_SUB | BPF_X:
emit(A64_SUB(is64, dst, dst, src), ctx);
break;
case BPF_ALU | BPF_AND | BPF_X:
case BPF_ALU64 | BPF_AND | BPF_X:
emit(A64_AND(is64, dst, dst, src), ctx);
break;
case BPF_ALU | BPF_OR | BPF_X:
case BPF_ALU64 | BPF_OR | BPF_X:
emit(A64_ORR(is64, dst, dst, src), ctx);
break;
case BPF_ALU | BPF_XOR | BPF_X:
case BPF_ALU64 | BPF_XOR | BPF_X:
emit(A64_EOR(is64, dst, dst, src), ctx);
break;
case BPF_ALU | BPF_MUL | BPF_X:
case BPF_ALU64 | BPF_MUL | BPF_X:
emit(A64_MUL(is64, dst, dst, src), ctx);
break;
case BPF_ALU | BPF_DIV | BPF_X:
case BPF_ALU64 | BPF_DIV | BPF_X:
emit(A64_UDIV(is64, dst, dst, src), ctx);
break;
case BPF_ALU | BPF_MOD | BPF_X:
case BPF_ALU64 | BPF_MOD | BPF_X:
emit(A64_UDIV(is64, tmp, dst, src), ctx);
emit(A64_MSUB(is64, dst, dst, tmp, src), ctx);
break;
case BPF_ALU | BPF_LSH | BPF_X:
case BPF_ALU64 | BPF_LSH | BPF_X:
emit(A64_LSLV(is64, dst, dst, src), ctx);
break;
case BPF_ALU | BPF_RSH | BPF_X:
case BPF_ALU64 | BPF_RSH | BPF_X:
emit(A64_LSRV(is64, dst, dst, src), ctx);
break;
case BPF_ALU | BPF_ARSH | BPF_X:
case BPF_ALU64 | BPF_ARSH | BPF_X:
emit(A64_ASRV(is64, dst, dst, src), ctx);
break;
/* dst = -dst */
case BPF_ALU | BPF_NEG:
case BPF_ALU64 | BPF_NEG:
emit(A64_NEG(is64, dst, dst), ctx);
break;
/* dst = BSWAP##imm(dst) */
case BPF_ALU | BPF_END | BPF_FROM_LE:
case BPF_ALU | BPF_END | BPF_FROM_BE:
#ifdef CONFIG_CPU_BIG_ENDIAN
if (BPF_SRC(code) == BPF_FROM_BE)
goto emit_bswap_uxt;
#else /* !CONFIG_CPU_BIG_ENDIAN */
if (BPF_SRC(code) == BPF_FROM_LE)
goto emit_bswap_uxt;
#endif
switch (imm) {
case 16:
emit(A64_REV16(is64, dst, dst), ctx);
/* zero-extend 16 bits into 64 bits */
emit(A64_UXTH(is64, dst, dst), ctx);
break;
case 32:
emit(A64_REV32(is64, dst, dst), ctx);
/* upper 32 bits already cleared */
break;
case 64:
emit(A64_REV64(dst, dst), ctx);
break;
}
break;
emit_bswap_uxt:
switch (imm) {
case 16:
/* zero-extend 16 bits into 64 bits */
emit(A64_UXTH(is64, dst, dst), ctx);
break;
case 32:
/* zero-extend 32 bits into 64 bits */
emit(A64_UXTW(is64, dst, dst), ctx);
break;
case 64:
/* nop */
break;
}
break;
/* dst = imm */
case BPF_ALU | BPF_MOV | BPF_K:
case BPF_ALU64 | BPF_MOV | BPF_K:
emit_a64_mov_i(is64, dst, imm, ctx);
break;
/* dst = dst OP imm */
case BPF_ALU | BPF_ADD | BPF_K:
case BPF_ALU64 | BPF_ADD | BPF_K:
if (is_addsub_imm(imm)) {
emit(A64_ADD_I(is64, dst, dst, imm), ctx);
} else if (is_addsub_imm(-imm)) {
emit(A64_SUB_I(is64, dst, dst, -imm), ctx);
} else {
emit_a64_mov_i(is64, tmp, imm, ctx);
emit(A64_ADD(is64, dst, dst, tmp), ctx);
}
break;
case BPF_ALU | BPF_SUB | BPF_K:
case BPF_ALU64 | BPF_SUB | BPF_K:
if (is_addsub_imm(imm)) {
emit(A64_SUB_I(is64, dst, dst, imm), ctx);
} else if (is_addsub_imm(-imm)) {
emit(A64_ADD_I(is64, dst, dst, -imm), ctx);
} else {
emit_a64_mov_i(is64, tmp, imm, ctx);
emit(A64_SUB(is64, dst, dst, tmp), ctx);
}
break;
case BPF_ALU | BPF_AND | BPF_K:
case BPF_ALU64 | BPF_AND | BPF_K:
a64_insn = A64_AND_I(is64, dst, dst, imm);
if (a64_insn != AARCH64_BREAK_FAULT) {
emit(a64_insn, ctx);
} else {
emit_a64_mov_i(is64, tmp, imm, ctx);
emit(A64_AND(is64, dst, dst, tmp), ctx);
}
break;
case BPF_ALU | BPF_OR | BPF_K:
case BPF_ALU64 | BPF_OR | BPF_K:
a64_insn = A64_ORR_I(is64, dst, dst, imm);
if (a64_insn != AARCH64_BREAK_FAULT) {
emit(a64_insn, ctx);
} else {
emit_a64_mov_i(is64, tmp, imm, ctx);
emit(A64_ORR(is64, dst, dst, tmp), ctx);
}
break;
case BPF_ALU | BPF_XOR | BPF_K:
case BPF_ALU64 | BPF_XOR | BPF_K:
a64_insn = A64_EOR_I(is64, dst, dst, imm);
if (a64_insn != AARCH64_BREAK_FAULT) {
emit(a64_insn, ctx);
} else {
emit_a64_mov_i(is64, tmp, imm, ctx);
emit(A64_EOR(is64, dst, dst, tmp), ctx);
}
break;
case BPF_ALU | BPF_MUL | BPF_K:
case BPF_ALU64 | BPF_MUL | BPF_K:
emit_a64_mov_i(is64, tmp, imm, ctx);
emit(A64_MUL(is64, dst, dst, tmp), ctx);
break;
case BPF_ALU | BPF_DIV | BPF_K:
case BPF_ALU64 | BPF_DIV | BPF_K:
emit_a64_mov_i(is64, tmp, imm, ctx);
emit(A64_UDIV(is64, dst, dst, tmp), ctx);
break;
case BPF_ALU | BPF_MOD | BPF_K:
case BPF_ALU64 | BPF_MOD | BPF_K:
emit_a64_mov_i(is64, tmp2, imm, ctx);
emit(A64_UDIV(is64, tmp, dst, tmp2), ctx);
emit(A64_MSUB(is64, dst, dst, tmp, tmp2), ctx);
break;
case BPF_ALU | BPF_LSH | BPF_K:
case BPF_ALU64 | BPF_LSH | BPF_K:
emit(A64_LSL(is64, dst, dst, imm), ctx);
break;
case BPF_ALU | BPF_RSH | BPF_K:
case BPF_ALU64 | BPF_RSH | BPF_K:
emit(A64_LSR(is64, dst, dst, imm), ctx);
break;
case BPF_ALU | BPF_ARSH | BPF_K:
case BPF_ALU64 | BPF_ARSH | BPF_K:
emit(A64_ASR(is64, dst, dst, imm), ctx);
break;
/* JUMP off */
case BPF_JMP | BPF_JA:
jmp_offset = bpf2a64_offset(i, off, ctx);
check_imm26(jmp_offset);
emit(A64_B(jmp_offset), ctx);
break;
/* IF (dst COND src) JUMP off */
case BPF_JMP | BPF_JEQ | 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_JNE | 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_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_JNE | 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:
emit(A64_CMP(is64, dst, src), ctx);
emit_cond_jmp:
jmp_offset = bpf2a64_offset(i, off, ctx);
check_imm19(jmp_offset);
switch (BPF_OP(code)) {
case BPF_JEQ:
jmp_cond = A64_COND_EQ;
break;
case BPF_JGT:
jmp_cond = A64_COND_HI;
break;
case BPF_JLT:
jmp_cond = A64_COND_CC;
break;
case BPF_JGE:
jmp_cond = A64_COND_CS;
break;
case BPF_JLE:
jmp_cond = A64_COND_LS;
break;
case BPF_JSET:
case BPF_JNE:
jmp_cond = A64_COND_NE;
break;
case BPF_JSGT:
jmp_cond = A64_COND_GT;
break;
case BPF_JSLT:
jmp_cond = A64_COND_LT;
break;
case BPF_JSGE:
jmp_cond = A64_COND_GE;
break;
case BPF_JSLE:
jmp_cond = A64_COND_LE;
break;
default:
return -EFAULT;
}
emit(A64_B_(jmp_cond, jmp_offset), ctx);
break;
case BPF_JMP | BPF_JSET | BPF_X:
case BPF_JMP32 | BPF_JSET | BPF_X:
emit(A64_TST(is64, dst, src), ctx);
goto emit_cond_jmp;
/* IF (dst COND imm) JUMP off */
case BPF_JMP | BPF_JEQ | 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_JNE | 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_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_JNE | 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:
if (is_addsub_imm(imm)) {
emit(A64_CMP_I(is64, dst, imm), ctx);
} else if (is_addsub_imm(-imm)) {
emit(A64_CMN_I(is64, dst, -imm), ctx);
} else {
emit_a64_mov_i(is64, tmp, imm, ctx);
emit(A64_CMP(is64, dst, tmp), ctx);
}
goto emit_cond_jmp;
case BPF_JMP | BPF_JSET | BPF_K:
case BPF_JMP32 | BPF_JSET | BPF_K:
a64_insn = A64_TST_I(is64, dst, imm);
if (a64_insn != AARCH64_BREAK_FAULT) {
emit(a64_insn, ctx);
} else {
emit_a64_mov_i(is64, tmp, imm, ctx);
emit(A64_TST(is64, dst, tmp), ctx);
}
goto emit_cond_jmp;
/* function call */
case BPF_JMP | BPF_CALL:
{
const u8 r0 = bpf2a64[BPF_REG_0];
bool func_addr_fixed;
u64 func_addr;
ret = bpf_jit_get_func_addr(ctx->prog, insn, extra_pass,
&func_addr, &func_addr_fixed);
if (ret < 0)
return ret;
emit_call(func_addr, ctx);
emit(A64_MOV(1, r0, A64_R(0)), ctx);
break;
}
/* tail call */
case BPF_JMP | BPF_TAIL_CALL:
if (emit_bpf_tail_call(ctx))
return -EFAULT;
break;
/* function return */
case BPF_JMP | BPF_EXIT:
/* Optimization: when last instruction is EXIT,
simply fallthrough to epilogue. */
if (i == ctx->prog->len - 1)
break;
jmp_offset = epilogue_offset(ctx);
check_imm26(jmp_offset);
emit(A64_B(jmp_offset), ctx);
break;
/* dst = imm64 */
case BPF_LD | BPF_IMM | BPF_DW:
{
const struct bpf_insn insn1 = insn[1];
u64 imm64;
imm64 = (u64)insn1.imm << 32 | (u32)imm;
if (bpf_pseudo_func(insn))
emit_addr_mov_i64(dst, imm64, ctx);
else
emit_a64_mov_i64(dst, imm64, ctx);
return 1;
}
/* LDX: dst = *(size *)(src + off) */
case BPF_LDX | BPF_MEM | BPF_W:
case BPF_LDX | BPF_MEM | BPF_H:
case BPF_LDX | BPF_MEM | BPF_B:
case BPF_LDX | BPF_MEM | BPF_DW:
case BPF_LDX | BPF_PROBE_MEM | BPF_DW:
case BPF_LDX | BPF_PROBE_MEM | BPF_W:
case BPF_LDX | BPF_PROBE_MEM | BPF_H:
case BPF_LDX | BPF_PROBE_MEM | BPF_B:
if (ctx->fpb_offset > 0 && src == fp) {
src_adj = fpb;
off_adj = off + ctx->fpb_offset;
} else {
src_adj = src;
off_adj = off;
}
switch (BPF_SIZE(code)) {
case BPF_W:
if (is_lsi_offset(off_adj, 2)) {
emit(A64_LDR32I(dst, src_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_LDR32(dst, src, tmp), ctx);
}
break;
case BPF_H:
if (is_lsi_offset(off_adj, 1)) {
emit(A64_LDRHI(dst, src_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_LDRH(dst, src, tmp), ctx);
}
break;
case BPF_B:
if (is_lsi_offset(off_adj, 0)) {
emit(A64_LDRBI(dst, src_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_LDRB(dst, src, tmp), ctx);
}
break;
case BPF_DW:
if (is_lsi_offset(off_adj, 3)) {
emit(A64_LDR64I(dst, src_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_LDR64(dst, src, tmp), ctx);
}
break;
}
ret = add_exception_handler(insn, ctx, dst);
if (ret)
return ret;
break;
/* speculation barrier */
case BPF_ST | BPF_NOSPEC:
/*
* Nothing required here.
*
* In case of arm64, we rely on the firmware mitigation of
* Speculative Store Bypass as controlled via the ssbd kernel
* parameter. Whenever the mitigation is enabled, it works
* for all of the kernel code with no need to provide any
* additional instructions.
*/
break;
/* ST: *(size *)(dst + off) = imm */
case BPF_ST | BPF_MEM | BPF_W:
case BPF_ST | BPF_MEM | BPF_H:
case BPF_ST | BPF_MEM | BPF_B:
case BPF_ST | BPF_MEM | BPF_DW:
if (ctx->fpb_offset > 0 && dst == fp) {
dst_adj = fpb;
off_adj = off + ctx->fpb_offset;
} else {
dst_adj = dst;
off_adj = off;
}
/* Load imm to a register then store it */
emit_a64_mov_i(1, tmp, imm, ctx);
switch (BPF_SIZE(code)) {
case BPF_W:
if (is_lsi_offset(off_adj, 2)) {
emit(A64_STR32I(tmp, dst_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp2, off, ctx);
emit(A64_STR32(tmp, dst, tmp2), ctx);
}
break;
case BPF_H:
if (is_lsi_offset(off_adj, 1)) {
emit(A64_STRHI(tmp, dst_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp2, off, ctx);
emit(A64_STRH(tmp, dst, tmp2), ctx);
}
break;
case BPF_B:
if (is_lsi_offset(off_adj, 0)) {
emit(A64_STRBI(tmp, dst_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp2, off, ctx);
emit(A64_STRB(tmp, dst, tmp2), ctx);
}
break;
case BPF_DW:
if (is_lsi_offset(off_adj, 3)) {
emit(A64_STR64I(tmp, dst_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp2, off, ctx);
emit(A64_STR64(tmp, dst, tmp2), ctx);
}
break;
}
break;
/* STX: *(size *)(dst + off) = src */
case BPF_STX | BPF_MEM | BPF_W:
case BPF_STX | BPF_MEM | BPF_H:
case BPF_STX | BPF_MEM | BPF_B:
case BPF_STX | BPF_MEM | BPF_DW:
if (ctx->fpb_offset > 0 && dst == fp) {
dst_adj = fpb;
off_adj = off + ctx->fpb_offset;
} else {
dst_adj = dst;
off_adj = off;
}
switch (BPF_SIZE(code)) {
case BPF_W:
if (is_lsi_offset(off_adj, 2)) {
emit(A64_STR32I(src, dst_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_STR32(src, dst, tmp), ctx);
}
break;
case BPF_H:
if (is_lsi_offset(off_adj, 1)) {
emit(A64_STRHI(src, dst_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_STRH(src, dst, tmp), ctx);
}
break;
case BPF_B:
if (is_lsi_offset(off_adj, 0)) {
emit(A64_STRBI(src, dst_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_STRB(src, dst, tmp), ctx);
}
break;
case BPF_DW:
if (is_lsi_offset(off_adj, 3)) {
emit(A64_STR64I(src, dst_adj, off_adj), ctx);
} else {
emit_a64_mov_i(1, tmp, off, ctx);
emit(A64_STR64(src, dst, tmp), ctx);
}
break;
}
break;
case BPF_STX | BPF_ATOMIC | BPF_W:
case BPF_STX | BPF_ATOMIC | BPF_DW:
if (cpus_have_cap(ARM64_HAS_LSE_ATOMICS))
ret = emit_lse_atomic(insn, ctx);
else
ret = emit_ll_sc_atomic(insn, ctx);
if (ret)
return ret;
break;
default:
pr_err_once("unknown opcode %02x\n", code);
return -EINVAL;
}
return 0;
}
/*
* Return 0 if FP may change at runtime, otherwise find the minimum negative
* offset to FP, converts it to positive number, and align down to 8 bytes.
*/
static int find_fpb_offset(struct bpf_prog *prog)
{
int i;
int offset = 0;
for (i = 0; i < prog->len; i++) {
const struct bpf_insn *insn = &prog->insnsi[i];
const u8 class = BPF_CLASS(insn->code);
const u8 mode = BPF_MODE(insn->code);
const u8 src = insn->src_reg;
const u8 dst = insn->dst_reg;
const s32 imm = insn->imm;
const s16 off = insn->off;
switch (class) {
case BPF_STX:
case BPF_ST:
/* fp holds atomic operation result */
if (class == BPF_STX && mode == BPF_ATOMIC &&
((imm == BPF_XCHG ||
imm == (BPF_FETCH | BPF_ADD) ||
imm == (BPF_FETCH | BPF_AND) ||
imm == (BPF_FETCH | BPF_XOR) ||
imm == (BPF_FETCH | BPF_OR)) &&
src == BPF_REG_FP))
return 0;
if (mode == BPF_MEM && dst == BPF_REG_FP &&
off < offset)
offset = insn->off;
break;
case BPF_JMP32:
case BPF_JMP:
break;
case BPF_LDX:
case BPF_LD:
/* fp holds load result */
if (dst == BPF_REG_FP)
return 0;
if (class == BPF_LDX && mode == BPF_MEM &&
src == BPF_REG_FP && off < offset)
offset = off;
break;
case BPF_ALU:
case BPF_ALU64:
default:
/* fp holds ALU result */
if (dst == BPF_REG_FP)
return 0;
}
}
if (offset < 0) {
/*
* safely be converted to a positive 'int', since insn->off
* is 's16'
*/
offset = -offset;
/* align down to 8 bytes */
offset = ALIGN_DOWN(offset, 8);
}
return offset;
}
static int build_body(struct jit_ctx *ctx, bool extra_pass)
{
const struct bpf_prog *prog = ctx->prog;
int i;
/*
* - offset[0] offset of the end of prologue,
* start of the 1st instruction.
* - offset[1] - offset of the end of 1st instruction,
* start of the 2nd instruction
* [....]
* - offset[3] - offset of the end of 3rd instruction,
* start of 4th instruction
*/
for (i = 0; i < prog->len; i++) {
const struct bpf_insn *insn = &prog->insnsi[i];
int ret;
if (ctx->image == NULL)
ctx->offset[i] = ctx->idx;
ret = build_insn(insn, ctx, extra_pass);
if (ret > 0) {
i++;
if (ctx->image == NULL)
ctx->offset[i] = ctx->idx;
continue;
}
if (ret)
return ret;
}
/*
* offset is allocated with prog->len + 1 so fill in
* the last element with the offset after the last
* instruction (end of program)
*/
if (ctx->image == NULL)
ctx->offset[i] = ctx->idx;
return 0;
}
static int validate_code(struct jit_ctx *ctx)
{
int i;
for (i = 0; i < ctx->idx; i++) {
u32 a64_insn = le32_to_cpu(ctx->image[i]);
if (a64_insn == AARCH64_BREAK_FAULT)
return -1;
}
return 0;
}
static int validate_ctx(struct jit_ctx *ctx)
{
if (validate_code(ctx))
return -1;
if (WARN_ON_ONCE(ctx->exentry_idx != ctx->prog->aux->num_exentries))
return -1;
return 0;
}
static inline void bpf_flush_icache(void *start, void *end)
{
flush_icache_range((unsigned long)start, (unsigned long)end);
}
struct arm64_jit_data {
struct bpf_binary_header *header;
u8 *image;
struct jit_ctx ctx;
};
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
{
int image_size, prog_size, extable_size, extable_align, extable_offset;
struct bpf_prog *tmp, *orig_prog = prog;
struct bpf_binary_header *header;
struct arm64_jit_data *jit_data;
bool was_classic = bpf_prog_was_classic(prog);
bool tmp_blinded = false;
bool extra_pass = false;
struct jit_ctx ctx;
u8 *image_ptr;
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;
}
if (jit_data->ctx.offset) {
ctx = jit_data->ctx;
image_ptr = jit_data->image;
header = jit_data->header;
extra_pass = true;
prog_size = sizeof(u32) * ctx.idx;
goto skip_init_ctx;
}
memset(&ctx, 0, sizeof(ctx));
ctx.prog = prog;
ctx.offset = kvcalloc(prog->len + 1, sizeof(int), GFP_KERNEL);
if (ctx.offset == NULL) {
prog = orig_prog;
goto out_off;
}
ctx.fpb_offset = find_fpb_offset(prog);
/*
* 1. Initial fake pass to compute ctx->idx and ctx->offset.
*
* BPF line info needs ctx->offset[i] to be the offset of
* instruction[i] in jited image, so build prologue first.
*/
if (build_prologue(&ctx, was_classic)) {
prog = orig_prog;
goto out_off;
}
if (build_body(&ctx, extra_pass)) {
prog = orig_prog;
goto out_off;
}
ctx.epilogue_offset = ctx.idx;
build_epilogue(&ctx);
build_plt(&ctx);
extable_align = __alignof__(struct exception_table_entry);
extable_size = prog->aux->num_exentries *
sizeof(struct exception_table_entry);
/* Now we know the actual image size. */
prog_size = sizeof(u32) * ctx.idx;
/* also allocate space for plt target */
extable_offset = round_up(prog_size + PLT_TARGET_SIZE, extable_align);
image_size = extable_offset + extable_size;
header = bpf_jit_binary_alloc(image_size, &image_ptr,
sizeof(u32), jit_fill_hole);
if (header == NULL) {
prog = orig_prog;
goto out_off;
}
/* 2. Now, the actual pass. */
ctx.image = (__le32 *)image_ptr;
if (extable_size)
prog->aux->extable = (void *)image_ptr + extable_offset;
skip_init_ctx:
ctx.idx = 0;
ctx.exentry_idx = 0;
build_prologue(&ctx, was_classic);
if (build_body(&ctx, extra_pass)) {
bpf_jit_binary_free(header);
prog = orig_prog;
goto out_off;
}
build_epilogue(&ctx);
build_plt(&ctx);
/* 3. Extra pass to validate JITed code. */
if (validate_ctx(&ctx)) {
bpf_jit_binary_free(header);
prog = orig_prog;
goto out_off;
}
/* And we're done. */
if (bpf_jit_enable > 1)
bpf_jit_dump(prog->len, prog_size, 2, ctx.image);
bpf_flush_icache(header, ctx.image + ctx.idx);
if (!prog->is_func || extra_pass) {
if (extra_pass && ctx.idx != jit_data->ctx.idx) {
pr_err_once("multi-func JIT bug %d != %d\n",
ctx.idx, jit_data->ctx.idx);
bpf_jit_binary_free(header);
prog->bpf_func = NULL;
prog->jited = 0;
prog->jited_len = 0;
goto out_off;
}
bpf_jit_binary_lock_ro(header);
} else {
jit_data->ctx = ctx;
jit_data->image = image_ptr;
jit_data->header = header;
}
prog->bpf_func = (void *)ctx.image;
prog->jited = 1;
prog->jited_len = prog_size;
if (!prog->is_func || extra_pass) {
int i;
/* offset[prog->len] is the size of program */
for (i = 0; i <= prog->len; i++)
ctx.offset[i] *= AARCH64_INSN_SIZE;
bpf_prog_fill_jited_linfo(prog, ctx.offset + 1);
out_off:
kvfree(ctx.offset);
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;
}
u64 bpf_jit_alloc_exec_limit(void)
{
return VMALLOC_END - VMALLOC_START;
}
void *bpf_jit_alloc_exec(unsigned long size)
{
/* Memory is intended to be executable, reset the pointer tag. */
return kasan_reset_tag(vmalloc(size));
}
void bpf_jit_free_exec(void *addr)
{
return vfree(addr);
}
/* Indicate the JIT backend supports mixing bpf2bpf and tailcalls. */
bool bpf_jit_supports_subprog_tailcalls(void)
{
return true;
}
static void invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
int args_off, int retval_off, int run_ctx_off,
bool save_ret)
{
__le32 *branch;
u64 enter_prog;
u64 exit_prog;
struct bpf_prog *p = l->link.prog;
int cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);
enter_prog = (u64)bpf_trampoline_enter(p);
exit_prog = (u64)bpf_trampoline_exit(p);
if (l->cookie == 0) {
/* if cookie is zero, one instruction is enough to store it */
emit(A64_STR64I(A64_ZR, A64_SP, run_ctx_off + cookie_off), ctx);
} else {
emit_a64_mov_i64(A64_R(10), l->cookie, ctx);
emit(A64_STR64I(A64_R(10), A64_SP, run_ctx_off + cookie_off),
ctx);
}
/* save p to callee saved register x19 to avoid loading p with mov_i64
* each time.
*/
emit_addr_mov_i64(A64_R(19), (const u64)p, ctx);
/* arg1: prog */
emit(A64_MOV(1, A64_R(0), A64_R(19)), ctx);
/* arg2: &run_ctx */
emit(A64_ADD_I(1, A64_R(1), A64_SP, run_ctx_off), ctx);
emit_call(enter_prog, ctx);
/* if (__bpf_prog_enter(prog) == 0)
* goto skip_exec_of_prog;
*/
branch = ctx->image + ctx->idx;
emit(A64_NOP, ctx);
/* save return value to callee saved register x20 */
emit(A64_MOV(1, A64_R(20), A64_R(0)), ctx);
emit(A64_ADD_I(1, A64_R(0), A64_SP, args_off), ctx);
if (!p->jited)
emit_addr_mov_i64(A64_R(1), (const u64)p->insnsi, ctx);
emit_call((const u64)p->bpf_func, ctx);
if (save_ret)
emit(A64_STR64I(A64_R(0), A64_SP, retval_off), ctx);
if (ctx->image) {
int offset = &ctx->image[ctx->idx] - branch;
*branch = cpu_to_le32(A64_CBZ(1, A64_R(0), offset));
}
/* arg1: prog */
emit(A64_MOV(1, A64_R(0), A64_R(19)), ctx);
/* arg2: start time */
emit(A64_MOV(1, A64_R(1), A64_R(20)), ctx);
/* arg3: &run_ctx */
emit(A64_ADD_I(1, A64_R(2), A64_SP, run_ctx_off), ctx);
emit_call(exit_prog, ctx);
}
static void invoke_bpf_mod_ret(struct jit_ctx *ctx, struct bpf_tramp_links *tl,
int args_off, int retval_off, int run_ctx_off,
__le32 **branches)
{
int i;
/* The first fmod_ret program will receive a garbage return value.
* Set this to 0 to avoid confusing the program.
*/
emit(A64_STR64I(A64_ZR, A64_SP, retval_off), ctx);
for (i = 0; i < tl->nr_links; i++) {
invoke_bpf_prog(ctx, tl->links[i], args_off, retval_off,
run_ctx_off, true);
/* if (*(u64 *)(sp + retval_off) != 0)
* goto do_fexit;
*/
emit(A64_LDR64I(A64_R(10), A64_SP, retval_off), ctx);
/* Save the location of branch, and generate a nop.
* This nop will be replaced with a cbnz later.
*/
branches[i] = ctx->image + ctx->idx;
emit(A64_NOP, ctx);
}
}
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static void save_args(struct jit_ctx *ctx, int args_off, int nregs)
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{
int i;
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for (i = 0; i < nregs; i++) {
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emit(A64_STR64I(i, A64_SP, args_off), ctx);
args_off += 8;
}
}
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static void restore_args(struct jit_ctx *ctx, int args_off, int nregs)
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{
int i;
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for (i = 0; i < nregs; i++) {
Initial commit
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emit(A64_LDR64I(i, A64_SP, args_off), ctx);
args_off += 8;
}
}
/* Based on the x86's implementation of arch_prepare_bpf_trampoline().
*
* bpf prog and function entry before bpf trampoline hooked:
* mov x9, lr
* nop
*
* bpf prog and function entry after bpf trampoline hooked:
* mov x9, lr
* bl <bpf_trampoline or plt>
*
*/
static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
struct bpf_tramp_links *tlinks, void *orig_call,
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int nregs, u32 flags)
Initial commit
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{
int i;
int stack_size;
int retaddr_off;
int regs_off;
int retval_off;
int args_off;
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int nregs_off;
Initial commit
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int ip_off;
int 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];
bool save_ret;
__le32 **branches = NULL;
/* trampoline stack layout:
* [ parent ip ]
* [ FP ]
* SP + retaddr_off [ self ip ]
* [ FP ]
*
* [ padding ] align SP to multiples of 16
*
* [ x20 ] callee saved reg x20
* SP + regs_off [ x19 ] callee saved reg x19
*
* SP + retval_off [ return value ] BPF_TRAMP_F_CALL_ORIG or
* BPF_TRAMP_F_RET_FENTRY_RET
*
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* [ arg reg N ]
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* [ ... ]
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* SP + args_off [ arg reg 1 ]
Initial commit
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*
6.5.5
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* SP + nregs_off [ arg regs count ]
Initial commit
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*
* SP + ip_off [ traced function ] BPF_TRAMP_F_IP_ARG flag
*
* SP + run_ctx_off [ bpf_tramp_run_ctx ]
*/
stack_size = 0;
run_ctx_off = stack_size;
/* room for bpf_tramp_run_ctx */
stack_size += round_up(sizeof(struct bpf_tramp_run_ctx), 8);
ip_off = stack_size;
/* room for IP address argument */
if (flags & BPF_TRAMP_F_IP_ARG)
stack_size += 8;
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nregs_off = stack_size;
Initial commit
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/* room for args count */
stack_size += 8;
args_off = stack_size;
/* room for args */
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stack_size += nregs * 8;
Initial commit
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/* room for return value */
retval_off = stack_size;
save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET);
if (save_ret)
stack_size += 8;
/* room for callee saved registers, currently x19 and x20 are used */
regs_off = stack_size;
stack_size += 16;
/* round up to multiples of 16 to avoid SPAlignmentFault */
stack_size = round_up(stack_size, 16);
/* return address locates above FP */
retaddr_off = stack_size + 8;
/* bpf trampoline may be invoked by 3 instruction types:
* 1. bl, attached to bpf prog or kernel function via short jump
* 2. br, attached to bpf prog or kernel function via long jump
* 3. blr, working as a function pointer, used by struct_ops.
* So BTI_JC should used here to support both br and blr.
*/
emit_bti(A64_BTI_JC, ctx);
/* frame for parent function */
emit(A64_PUSH(A64_FP, A64_R(9), A64_SP), ctx);
emit(A64_MOV(1, A64_FP, A64_SP), ctx);
/* frame for patched function */
emit(A64_PUSH(A64_FP, A64_LR, A64_SP), ctx);
emit(A64_MOV(1, A64_FP, A64_SP), ctx);
/* allocate stack space */
emit(A64_SUB_I(1, A64_SP, A64_SP, stack_size), ctx);
if (flags & BPF_TRAMP_F_IP_ARG) {
/* save ip address of the traced function */
emit_addr_mov_i64(A64_R(10), (const u64)orig_call, ctx);
emit(A64_STR64I(A64_R(10), A64_SP, ip_off), ctx);
}
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/* save arg regs count*/
emit(A64_MOVZ(1, A64_R(10), nregs, 0), ctx);
emit(A64_STR64I(A64_R(10), A64_SP, nregs_off), ctx);
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/* save arg regs */
save_args(ctx, args_off, nregs);
Initial commit
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/* save callee saved registers */
emit(A64_STR64I(A64_R(19), A64_SP, regs_off), ctx);
emit(A64_STR64I(A64_R(20), A64_SP, regs_off + 8), ctx);
if (flags & BPF_TRAMP_F_CALL_ORIG) {
emit_addr_mov_i64(A64_R(0), (const u64)im, ctx);
emit_call((const u64)__bpf_tramp_enter, ctx);
}
for (i = 0; i < fentry->nr_links; i++)
invoke_bpf_prog(ctx, fentry->links[i], args_off,
retval_off, run_ctx_off,
flags & BPF_TRAMP_F_RET_FENTRY_RET);
if (fmod_ret->nr_links) {
branches = kcalloc(fmod_ret->nr_links, sizeof(__le32 *),
GFP_KERNEL);
if (!branches)
return -ENOMEM;
invoke_bpf_mod_ret(ctx, fmod_ret, args_off, retval_off,
run_ctx_off, branches);
}
if (flags & BPF_TRAMP_F_CALL_ORIG) {
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restore_args(ctx, args_off, nregs);
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/* call original func */
emit(A64_LDR64I(A64_R(10), A64_SP, retaddr_off), ctx);
emit(A64_ADR(A64_LR, AARCH64_INSN_SIZE * 2), ctx);
emit(A64_RET(A64_R(10)), ctx);
/* store return value */
emit(A64_STR64I(A64_R(0), A64_SP, retval_off), ctx);
/* reserve a nop for bpf_tramp_image_put */
im->ip_after_call = ctx->image + ctx->idx;
emit(A64_NOP, ctx);
}
/* update the branches saved in invoke_bpf_mod_ret with cbnz */
for (i = 0; i < fmod_ret->nr_links && ctx->image != NULL; i++) {
int offset = &ctx->image[ctx->idx] - branches[i];
*branches[i] = cpu_to_le32(A64_CBNZ(1, A64_R(10), offset));
}
for (i = 0; i < fexit->nr_links; i++)
invoke_bpf_prog(ctx, fexit->links[i], args_off, retval_off,
run_ctx_off, false);
if (flags & BPF_TRAMP_F_CALL_ORIG) {
im->ip_epilogue = ctx->image + ctx->idx;
emit_addr_mov_i64(A64_R(0), (const u64)im, ctx);
emit_call((const u64)__bpf_tramp_exit, ctx);
}
if (flags & BPF_TRAMP_F_RESTORE_REGS)
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restore_args(ctx, args_off, nregs);
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/* restore callee saved register x19 and x20 */
emit(A64_LDR64I(A64_R(19), A64_SP, regs_off), ctx);
emit(A64_LDR64I(A64_R(20), A64_SP, regs_off + 8), ctx);
if (save_ret)
emit(A64_LDR64I(A64_R(0), A64_SP, retval_off), ctx);
/* reset SP */
emit(A64_MOV(1, A64_SP, A64_FP), ctx);
/* pop frames */
emit(A64_POP(A64_FP, A64_LR, A64_SP), ctx);
emit(A64_POP(A64_FP, A64_R(9), A64_SP), ctx);
if (flags & BPF_TRAMP_F_SKIP_FRAME) {
/* skip patched function, return to parent */
emit(A64_MOV(1, A64_LR, A64_R(9)), ctx);
emit(A64_RET(A64_R(9)), ctx);
} else {
/* return to patched function */
emit(A64_MOV(1, A64_R(10), A64_LR), ctx);
emit(A64_MOV(1, A64_LR, A64_R(9)), ctx);
emit(A64_RET(A64_R(10)), ctx);
}
if (ctx->image)
bpf_flush_icache(ctx->image, ctx->image + ctx->idx);
kfree(branches);
return ctx->idx;
}
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 i, ret;
6.5.5
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int nregs = m->nr_args;
Initial commit
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int max_insns = ((long)image_end - (long)image) / AARCH64_INSN_SIZE;
struct jit_ctx ctx = {
.image = NULL,
.idx = 0,
};
6.5.5
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/* extra registers needed for struct argument */
Initial commit
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for (i = 0; i < MAX_BPF_FUNC_ARGS; i++) {
6.5.5
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/* The arg_size is at most 16 bytes, enforced by the verifier. */
Initial commit
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if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG)
6.5.5
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nregs += (m->arg_size[i] + 7) / 8 - 1;
Initial commit
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}
6.5.5
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/* the first 8 registers are used for arguments */
if (nregs > 8)
return -ENOTSUPP;
ret = prepare_trampoline(&ctx, im, tlinks, orig_call, nregs, flags);
Initial commit
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if (ret < 0)
return ret;
if (ret > max_insns)
return -EFBIG;
ctx.image = image;
ctx.idx = 0;
jit_fill_hole(image, (unsigned int)(image_end - image));
6.5.5
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ret = prepare_trampoline(&ctx, im, tlinks, orig_call, nregs, flags);
Initial commit
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if (ret > 0 && validate_code(&ctx) < 0)
ret = -EINVAL;
if (ret > 0)
ret *= AARCH64_INSN_SIZE;
return ret;
}
static bool is_long_jump(void *ip, void *target)
{
long offset;
/* NULL target means this is a NOP */
if (!target)
return false;
offset = (long)target - (long)ip;
return offset < -SZ_128M || offset >= SZ_128M;
}
static int gen_branch_or_nop(enum aarch64_insn_branch_type type, void *ip,
void *addr, void *plt, u32 *insn)
{
void *target;
if (!addr) {
*insn = aarch64_insn_gen_nop();
return 0;
}
if (is_long_jump(ip, addr))
target = plt;
else
target = addr;
*insn = aarch64_insn_gen_branch_imm((unsigned long)ip,
(unsigned long)target,
type);
return *insn != AARCH64_BREAK_FAULT ? 0 : -EFAULT;
}
/* Replace the branch instruction from @ip to @old_addr in a bpf prog or a bpf
* trampoline with the branch instruction from @ip to @new_addr. If @old_addr
* or @new_addr is NULL, the old or new instruction is NOP.
*
* When @ip is the bpf prog entry, a bpf trampoline is being attached or
* detached. Since bpf trampoline and bpf prog are allocated separately with
* vmalloc, the address distance may exceed 128MB, the maximum branch range.
* So long jump should be handled.
*
* When a bpf prog is constructed, a plt pointing to empty trampoline
* dummy_tramp is placed at the end:
*
* bpf_prog:
* mov x9, lr
* nop // patchsite
* ...
* ret
*
* plt:
* ldr x10, target
* br x10
* target:
* .quad dummy_tramp // plt target
*
* This is also the state when no trampoline is attached.
*
* When a short-jump bpf trampoline is attached, the patchsite is patched
* to a bl instruction to the trampoline directly:
*
* bpf_prog:
* mov x9, lr
* bl <short-jump bpf trampoline address> // patchsite
* ...
* ret
*
* plt:
* ldr x10, target
* br x10
* target:
* .quad dummy_tramp // plt target
*
* When a long-jump bpf trampoline is attached, the plt target is filled with
* the trampoline address and the patchsite is patched to a bl instruction to
* the plt:
*
* bpf_prog:
* mov x9, lr
* bl plt // patchsite
* ...
* ret
*
* plt:
* ldr x10, target
* br x10
* target:
* .quad <long-jump bpf trampoline address> // plt target
*
* The dummy_tramp is used to prevent another CPU from jumping to unknown
* locations during the patching process, making the patching process easier.
*/
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
void *old_addr, void *new_addr)
{
int ret;
u32 old_insn;
u32 new_insn;
u32 replaced;
struct bpf_plt *plt = NULL;
unsigned long size = 0UL;
unsigned long offset = ~0UL;
enum aarch64_insn_branch_type branch_type;
char namebuf[KSYM_NAME_LEN];
void *image = NULL;
u64 plt_target = 0ULL;
bool poking_bpf_entry;
if (!__bpf_address_lookup((unsigned long)ip, &size, &offset, namebuf))
/* Only poking bpf text is supported. Since kernel function
* entry is set up by ftrace, we reply on ftrace to poke kernel
* functions.
*/
return -ENOTSUPP;
image = ip - offset;
/* zero offset means we're poking bpf prog entry */
poking_bpf_entry = (offset == 0UL);
/* bpf prog entry, find plt and the real patchsite */
if (poking_bpf_entry) {
/* plt locates at the end of bpf prog */
plt = image + size - PLT_TARGET_OFFSET;
/* skip to the nop instruction in bpf prog entry:
* bti c // if BTI enabled
* mov x9, x30
* nop
*/
ip = image + POKE_OFFSET * AARCH64_INSN_SIZE;
}
/* long jump is only possible at bpf prog entry */
if (WARN_ON((is_long_jump(ip, new_addr) || is_long_jump(ip, old_addr)) &&
!poking_bpf_entry))
return -EINVAL;
if (poke_type == BPF_MOD_CALL)
branch_type = AARCH64_INSN_BRANCH_LINK;
else
branch_type = AARCH64_INSN_BRANCH_NOLINK;
if (gen_branch_or_nop(branch_type, ip, old_addr, plt, &old_insn) < 0)
return -EFAULT;
if (gen_branch_or_nop(branch_type, ip, new_addr, plt, &new_insn) < 0)
return -EFAULT;
if (is_long_jump(ip, new_addr))
plt_target = (u64)new_addr;
else if (is_long_jump(ip, old_addr))
/* if the old target is a long jump and the new target is not,
* restore the plt target to dummy_tramp, so there is always a
* legal and harmless address stored in plt target, and we'll
* never jump from plt to an unknown place.
*/
plt_target = (u64)&dummy_tramp;
if (plt_target) {
/* non-zero plt_target indicates we're patching a bpf prog,
* which is read only.
*/
if (set_memory_rw(PAGE_MASK & ((uintptr_t)&plt->target), 1))
return -EFAULT;
WRITE_ONCE(plt->target, plt_target);
set_memory_ro(PAGE_MASK & ((uintptr_t)&plt->target), 1);
/* since plt target points to either the new trampoline
* or dummy_tramp, even if another CPU reads the old plt
* target value before fetching the bl instruction to plt,
* it will be brought back by dummy_tramp, so no barrier is
* required here.
*/
}
/* if the old target and the new target are both long jumps, no
* patching is required
*/
if (old_insn == new_insn)
return 0;
mutex_lock(&text_mutex);
if (aarch64_insn_read(ip, &replaced)) {
ret = -EFAULT;
goto out;
}
if (replaced != old_insn) {
ret = -EFAULT;
goto out;
}
/* We call aarch64_insn_patch_text_nosync() to replace instruction
* atomically, so no other CPUs will fetch a half-new and half-old
* instruction. But there is chance that another CPU executes the
* old instruction after the patching operation finishes (e.g.,
* pipeline not flushed, or icache not synchronized yet).
*
* 1. when a new trampoline is attached, it is not a problem for
* different CPUs to jump to different trampolines temporarily.
*
* 2. when an old trampoline is freed, we should wait for all other
* CPUs to exit the trampoline and make sure the trampoline is no
* longer reachable, since bpf_tramp_image_put() function already
* uses percpu_ref and task-based rcu to do the sync, no need to call
* the sync version here, see bpf_tramp_image_put() for details.
*/
ret = aarch64_insn_patch_text_nosync(ip, new_insn);
out:
mutex_unlock(&text_mutex);
return ret;
}