static int add_exception_handler()

in net/bpf_jit_comp64.c [474:520]

• 30 lines of code
• 11 McCabe index (conditional complexity)

static int add_exception_handler(const struct bpf_insn *insn,
				 struct rv_jit_context *ctx,
				 int dst_reg, int insn_len)
{
	struct exception_table_entry *ex;
	unsigned long pc;
	off_t offset;

	if (!ctx->insns || !ctx->prog->aux->extable || BPF_MODE(insn->code) != BPF_PROBE_MEM)
		return 0;

	if (WARN_ON_ONCE(ctx->nexentries >= ctx->prog->aux->num_exentries))
		return -EINVAL;

	if (WARN_ON_ONCE(insn_len > ctx->ninsns))
		return -EINVAL;

	if (WARN_ON_ONCE(!rvc_enabled() && insn_len == 1))
		return -EINVAL;

	ex = &ctx->prog->aux->extable[ctx->nexentries];
	pc = (unsigned long)&ctx->insns[ctx->ninsns - insn_len];

	offset = pc - (long)&ex->insn;
	if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN))
		return -ERANGE;
	ex->insn = pc;

	/*
	 * 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 + insn_len * sizeof(u16));
	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->nexentries++;
	return 0;
}