70 lines
1.8 KiB
C
70 lines
1.8 KiB
C
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// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
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#include <bpf/bpf.h>
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#include "disasm.h"
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struct print_insn_context {
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char scratch[16];
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char *buf;
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size_t sz;
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};
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static void print_insn_cb(void *private_data, const char *fmt, ...)
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{
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struct print_insn_context *ctx = private_data;
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va_list args;
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va_start(args, fmt);
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vsnprintf(ctx->buf, ctx->sz, fmt, args);
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va_end(args);
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}
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static const char *print_call_cb(void *private_data, const struct bpf_insn *insn)
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{
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struct print_insn_context *ctx = private_data;
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/* For pseudo calls verifier.c:jit_subprogs() hides original
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* imm to insn->off and changes insn->imm to be an index of
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* the subprog instead.
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*/
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if (insn->src_reg == BPF_PSEUDO_CALL) {
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snprintf(ctx->scratch, sizeof(ctx->scratch), "%+d", insn->off);
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return ctx->scratch;
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}
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return NULL;
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}
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struct bpf_insn *disasm_insn(struct bpf_insn *insn, char *buf, size_t buf_sz)
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{
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struct print_insn_context ctx = {
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.buf = buf,
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.sz = buf_sz,
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};
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struct bpf_insn_cbs cbs = {
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.cb_print = print_insn_cb,
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.cb_call = print_call_cb,
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.private_data = &ctx,
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};
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char *tmp, *pfx_end, *sfx_start;
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bool double_insn;
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int len;
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print_bpf_insn(&cbs, insn, true);
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/* We share code with kernel BPF disassembler, it adds '(FF) ' prefix
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* for each instruction (FF stands for instruction `code` byte).
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* Remove the prefix inplace, and also simplify call instructions.
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* E.g.: "(85) call foo#10" -> "call foo".
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* Also remove newline in the end (the 'max(strlen(buf) - 1, 0)' thing).
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*/
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pfx_end = buf + 5;
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sfx_start = buf + max((int)strlen(buf) - 1, 0);
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if (strncmp(pfx_end, "call ", 5) == 0 && (tmp = strrchr(buf, '#')))
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sfx_start = tmp;
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len = sfx_start - pfx_end;
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memmove(buf, pfx_end, len);
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buf[len] = 0;
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double_insn = insn->code == (BPF_LD | BPF_IMM | BPF_DW);
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return insn + (double_insn ? 2 : 1);
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}
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