ba0cbe2bb4
The verifier in the kernel ensures that the struct_ops operators behave
correctly by checking that they access parameters and context
appropriately. The verifier will approve a program as long as it correctly
accesses the context/parameters, regardless of its function signature. In
contrast, libbpf should not verify the signature of function pointers and
functions to enable flexibility in loading various implementations of an
operator even if the signature of the function pointer does not match those
in the implementations or the kernel.
With this flexibility, user space applications can adapt to different
kernel versions by loading a specific implementation of an operator based
on feature detection.
This is a follow-up of the commit c911fc61a7 ("libbpf: Skip zeroed or
null fields if not found in the kernel type.")
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240404232342.991414-1-thinker.li@gmail.com
83 lines
1.7 KiB
C
83 lines
1.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
|
|
#include <vmlinux.h>
|
|
#include <bpf/bpf_helpers.h>
|
|
#include <bpf/bpf_tracing.h>
|
|
#include "../bpf_testmod/bpf_testmod.h"
|
|
|
|
char _license[] SEC("license") = "GPL";
|
|
|
|
int test_1_result = 0;
|
|
int test_2_result = 0;
|
|
|
|
SEC("struct_ops/test_1")
|
|
int BPF_PROG(test_1)
|
|
{
|
|
test_1_result = 0xdeadbeef;
|
|
return 0;
|
|
}
|
|
|
|
SEC("struct_ops/test_2")
|
|
void BPF_PROG(test_2, int a, int b)
|
|
{
|
|
test_2_result = a + b;
|
|
}
|
|
|
|
SEC("?struct_ops/test_3")
|
|
int BPF_PROG(test_3, int a, int b)
|
|
{
|
|
test_2_result = a + b + 3;
|
|
return a + b + 3;
|
|
}
|
|
|
|
SEC(".struct_ops.link")
|
|
struct bpf_testmod_ops testmod_1 = {
|
|
.test_1 = (void *)test_1,
|
|
.test_2 = (void *)test_2,
|
|
.data = 0x1,
|
|
};
|
|
|
|
SEC("struct_ops/test_2")
|
|
void BPF_PROG(test_2_v2, int a, int b)
|
|
{
|
|
test_2_result = a * b;
|
|
}
|
|
|
|
struct bpf_testmod_ops___v2 {
|
|
int (*test_1)(void);
|
|
void (*test_2)(int a, int b);
|
|
int (*test_maybe_null)(int dummy, struct task_struct *task);
|
|
};
|
|
|
|
SEC(".struct_ops.link")
|
|
struct bpf_testmod_ops___v2 testmod_2 = {
|
|
.test_1 = (void *)test_1,
|
|
.test_2 = (void *)test_2_v2,
|
|
};
|
|
|
|
struct bpf_testmod_ops___zeroed {
|
|
int (*test_1)(void);
|
|
void (*test_2)(int a, int b);
|
|
int (*test_maybe_null)(int dummy, struct task_struct *task);
|
|
void (*zeroed_op)(int a, int b);
|
|
int zeroed;
|
|
};
|
|
|
|
SEC(".struct_ops.link")
|
|
struct bpf_testmod_ops___zeroed testmod_zeroed = {
|
|
.test_1 = (void *)test_1,
|
|
.test_2 = (void *)test_2_v2,
|
|
};
|
|
|
|
struct bpf_testmod_ops___incompatible {
|
|
int (*test_1)(void);
|
|
void (*test_2)(int *a);
|
|
int data;
|
|
};
|
|
|
|
SEC(".struct_ops.link")
|
|
struct bpf_testmod_ops___incompatible testmod_incompatible = {
|
|
.test_1 = (void *)test_1,
|
|
.test_2 = (void *)test_2,
|
|
.data = 3,
|
|
};
|