tools/testing/selftests/bpf/progs/epilogue_exit.c

// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */

#include <vmlinux.h>
#include <bpf/bpf_tracing.h>
#include "bpf_misc.h"
#include "../bpf_testmod/bpf_testmod.h"
#include "../bpf_testmod/bpf_testmod_kfunc.h"

char _license[] SEC("license") = "GPL";

__success
/* save __u64 *ctx to stack */
__xlated("0: *(u64 *)(r10 -8) = r1")
/* main prog */
__xlated("1: r1 = *(u64 *)(r1 +0)")
__xlated("2: r2 = *(u64 *)(r1 +0)")
__xlated("3: r3 = 0")
__xlated("4: r4 = 1")
__xlated("5: if r2 == 0x0 goto pc+10")
__xlated("6: r0 = 0")
__xlated("7: *(u64 *)(r1 +0) = r3")
/* epilogue */
__xlated("8: r1 = *(u64 *)(r10 -8)")
__xlated("9: r1 = *(u64 *)(r1 +0)")
__xlated("10: r6 = *(u64 *)(r1 +0)")
__xlated("11: r6 += 10000")
__xlated("12: *(u64 *)(r1 +0) = r6")
__xlated("13: r0 = r6")
__xlated("14: r0 *= 2")
__xlated("15: exit")
/* 2nd part of the main prog after the first exit */
__xlated("16: *(u64 *)(r1 +0) = r4")
__xlated("17: r0 = 1")
/* Clear the r1 to ensure it does not have
 * off-by-1 error and ensure it jumps back to the
 * beginning of epilogue which initializes
 * the r1 with the ctx ptr.
 */
__xlated("18: r1 = 0")
__xlated("19: gotol pc-12")
SEC("struct_ops/test_epilogue_exit")
__naked int test_epilogue_exit(void)
{
	asm volatile (
	"r1 = *(u64 *)(r1 +0);"
	"r2 = *(u64 *)(r1 +0);"
	"r3 = 0;"
	"r4 = 1;"
	"if r2 == 0 goto +3;"
	"r0 = 0;"
	"*(u64 *)(r1 + 0) = r3;"
	"exit;"
	"*(u64 *)(r1 + 0) = r4;"
	"r0 = 1;"
	"r1 = 0;"
	"exit;"
	::: __clobber_all);
}

SEC(".struct_ops.link")
struct bpf_testmod_st_ops epilogue_exit = {
	.test_epilogue = (void *)test_epilogue_exit,
};

SEC("syscall")
__retval(20000)
int syscall_epilogue_exit0(void *ctx)
{
	struct st_ops_args args = { .a = 1 };

	return bpf_kfunc_st_ops_test_epilogue(&args);
}

SEC("syscall")
__retval(20002)
int syscall_epilogue_exit1(void *ctx)
{
	struct st_ops_args args = {};

	return bpf_kfunc_st_ops_test_epilogue(&args);
}