bpf_jit_core.c
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// SPDX-License-Identifier: GPL-2.0
/*
* Common functionality for RV32 and RV64 BPF JIT compilers
*
* Copyright (c) 2019 Björn Töpel <bjorn.topel@gmail.com>
*
*/
#include <linux/bpf.h>
#include <linux/filter.h>
#include "bpf_jit.h"
/* Number of iterations to try until offsets converge. */
#define NR_JIT_ITERATIONS 16
static int build_body(struct rv_jit_context *ctx, bool extra_pass, int *offset)
{
const struct bpf_prog *prog = ctx->prog;
int i;
for (i = 0; i < prog->len; i++) {
const struct bpf_insn *insn = &prog->insnsi[i];
int ret;
ret = bpf_jit_emit_insn(insn, ctx, extra_pass);
/* BPF_LD | BPF_IMM | BPF_DW: skip the next instruction. */
if (ret > 0)
i++;
if (offset)
offset[i] = ctx->ninsns;
if (ret < 0)
return ret;
}
return 0;
}
bool bpf_jit_needs_zext(void)
{
return true;
}
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
{
bool tmp_blinded = false, extra_pass = false;
struct bpf_prog *tmp, *orig_prog = prog;
int pass = 0, prev_ninsns = 0, i;
struct rv_jit_data *jit_data;
struct rv_jit_context *ctx;
unsigned int image_size = 0;
if (!prog->jit_requested)
return orig_prog;
tmp = bpf_jit_blind_constants(prog);
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;
}
ctx = &jit_data->ctx;
if (ctx->offset) {
extra_pass = true;
image_size = sizeof(*ctx->insns) * ctx->ninsns;
goto skip_init_ctx;
}
ctx->prog = prog;
ctx->offset = kcalloc(prog->len, sizeof(int), GFP_KERNEL);
if (!ctx->offset) {
prog = orig_prog;
goto out_offset;
}
for (i = 0; i < prog->len; i++) {
prev_ninsns += 32;
ctx->offset[i] = prev_ninsns;
}
for (i = 0; i < NR_JIT_ITERATIONS; i++) {
pass++;
ctx->ninsns = 0;
if (build_body(ctx, extra_pass, ctx->offset)) {
prog = orig_prog;
goto out_offset;
}
bpf_jit_build_prologue(ctx);
ctx->epilogue_offset = ctx->ninsns;
bpf_jit_build_epilogue(ctx);
if (ctx->ninsns == prev_ninsns) {
if (jit_data->header)
break;
image_size = sizeof(*ctx->insns) * ctx->ninsns;
jit_data->header =
bpf_jit_binary_alloc(image_size,
&jit_data->image,
sizeof(u32),
bpf_fill_ill_insns);
if (!jit_data->header) {
prog = orig_prog;
goto out_offset;
}
ctx->insns = (u16 *)jit_data->image;
/*
* Now, when the image is allocated, the image can
* potentially shrink more (auipc/jalr -> jal).
*/
}
prev_ninsns = ctx->ninsns;
}
if (i == NR_JIT_ITERATIONS) {
pr_err("bpf-jit: image did not converge in <%d passes!\n", i);
bpf_jit_binary_free(jit_data->header);
prog = orig_prog;
goto out_offset;
}
skip_init_ctx:
pass++;
ctx->ninsns = 0;
bpf_jit_build_prologue(ctx);
if (build_body(ctx, extra_pass, NULL)) {
bpf_jit_binary_free(jit_data->header);
prog = orig_prog;
goto out_offset;
}
bpf_jit_build_epilogue(ctx);
if (bpf_jit_enable > 1)
bpf_jit_dump(prog->len, image_size, pass, ctx->insns);
prog->bpf_func = (void *)ctx->insns;
prog->jited = 1;
prog->jited_len = image_size;
bpf_flush_icache(jit_data->header, ctx->insns + ctx->ninsns);
if (!prog->is_func || extra_pass) {
out_offset:
kfree(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;
}