void bpf_jit_build_prologue()

in net/bpf_jit_comp64.c [1182:1262]

• 63 lines of code
• 19 McCabe index (conditional complexity)

void bpf_jit_build_prologue(struct rv_jit_context *ctx)
{
	int stack_adjust = 0, store_offset, bpf_stack_adjust;

	bpf_stack_adjust = round_up(ctx->prog->aux->stack_depth, 16);
	if (bpf_stack_adjust)
		mark_fp(ctx);

	if (seen_reg(RV_REG_RA, ctx))
		stack_adjust += 8;
	stack_adjust += 8; /* RV_REG_FP */
	if (seen_reg(RV_REG_S1, ctx))
		stack_adjust += 8;
	if (seen_reg(RV_REG_S2, ctx))
		stack_adjust += 8;
	if (seen_reg(RV_REG_S3, ctx))
		stack_adjust += 8;
	if (seen_reg(RV_REG_S4, ctx))
		stack_adjust += 8;
	if (seen_reg(RV_REG_S5, ctx))
		stack_adjust += 8;
	if (seen_reg(RV_REG_S6, ctx))
		stack_adjust += 8;

	stack_adjust = round_up(stack_adjust, 16);
	stack_adjust += bpf_stack_adjust;

	store_offset = stack_adjust - 8;

	/* First instruction is always setting the tail-call-counter
	 * (TCC) register. This instruction is skipped for tail calls.
	 * Force using a 4-byte (non-compressed) instruction.
	 */
	emit(rv_addi(RV_REG_TCC, RV_REG_ZERO, MAX_TAIL_CALL_CNT), ctx);

	emit_addi(RV_REG_SP, RV_REG_SP, -stack_adjust, ctx);

	if (seen_reg(RV_REG_RA, ctx)) {
		emit_sd(RV_REG_SP, store_offset, RV_REG_RA, ctx);
		store_offset -= 8;
	}
	emit_sd(RV_REG_SP, store_offset, RV_REG_FP, ctx);
	store_offset -= 8;
	if (seen_reg(RV_REG_S1, ctx)) {
		emit_sd(RV_REG_SP, store_offset, RV_REG_S1, ctx);
		store_offset -= 8;
	}
	if (seen_reg(RV_REG_S2, ctx)) {
		emit_sd(RV_REG_SP, store_offset, RV_REG_S2, ctx);
		store_offset -= 8;
	}
	if (seen_reg(RV_REG_S3, ctx)) {
		emit_sd(RV_REG_SP, store_offset, RV_REG_S3, ctx);
		store_offset -= 8;
	}
	if (seen_reg(RV_REG_S4, ctx)) {
		emit_sd(RV_REG_SP, store_offset, RV_REG_S4, ctx);
		store_offset -= 8;
	}
	if (seen_reg(RV_REG_S5, ctx)) {
		emit_sd(RV_REG_SP, store_offset, RV_REG_S5, ctx);
		store_offset -= 8;
	}
	if (seen_reg(RV_REG_S6, ctx)) {
		emit_sd(RV_REG_SP, store_offset, RV_REG_S6, ctx);
		store_offset -= 8;
	}

	emit_addi(RV_REG_FP, RV_REG_SP, stack_adjust, ctx);

	if (bpf_stack_adjust)
		emit_addi(RV_REG_S5, RV_REG_SP, bpf_stack_adjust, ctx);

	/* Program contains calls and tail calls, so RV_REG_TCC need
	 * to be saved across calls.
	 */
	if (seen_tail_call(ctx) && seen_call(ctx))
		emit_mv(RV_REG_TCC_SAVED, RV_REG_TCC, ctx);

	ctx->stack_size = stack_adjust;
}