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bpf: Support ->fill_link_info for kprobe_multi

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With the addition of support for fill_link_info to the kprobe_multi link,
users will gain the ability to inspect it conveniently using the
`bpftool link show`. This enhancement provides valuable information to the
user, including the count of probed functions and their respective
addresses. It's important to note that if the kptr_restrict setting is not
permitted, the probed address will not be exposed, ensuring security.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230709025630.3735-2-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Yafang Shao 2023-07-09 02:56:21 +00:00 committed by Alexei Starovoitov
parent 07018b5706
commit 7ac8d0d261
3 changed files with 47 additions and 0 deletions
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5
include/uapi/linux/bpf.h
View file

@ -6439,6 +6439,11 @@ struct bpf_link_info {
__s32 priority;
__u32 flags;
} netfilter;
struct {
__aligned_u64 addrs;
__u32 count; /* in/out: kprobe_multi function count */
__u32 flags;
} kprobe_multi;
};
} __attribute__((aligned(8)));

37
kernel/trace/bpf_trace.c
View file

@ -2469,6 +2469,7 @@ struct bpf_kprobe_multi_link {
u32 cnt;
u32 mods_cnt;
struct module **mods;
u32 flags;
};
struct bpf_kprobe_multi_run_ctx {
@ -2558,9 +2559,44 @@ static void bpf_kprobe_multi_link_dealloc(struct bpf_link *link)
kfree(kmulti_link);
}
static int bpf_kprobe_multi_link_fill_link_info(const struct bpf_link *link,
struct bpf_link_info *info)
{
u64 __user *uaddrs = u64_to_user_ptr(info->kprobe_multi.addrs);
struct bpf_kprobe_multi_link *kmulti_link;
u32 ucount = info->kprobe_multi.count;
int err = 0, i;
if (!uaddrs ^ !ucount)
return -EINVAL;
kmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);
info->kprobe_multi.count = kmulti_link->cnt;
info->kprobe_multi.flags = kmulti_link->flags;
if (!uaddrs)
return 0;
if (ucount < kmulti_link->cnt)
err = -ENOSPC;
else
ucount = kmulti_link->cnt;
if (kallsyms_show_value(current_cred())) {
if (copy_to_user(uaddrs, kmulti_link->addrs, ucount * sizeof(u64)))
return -EFAULT;
} else {
for (i = 0; i < ucount; i++) {
if (put_user(0, uaddrs + i))
return -EFAULT;
}
}
return err;
}
static const struct bpf_link_ops bpf_kprobe_multi_link_lops = {
.release = bpf_kprobe_multi_link_release,
.dealloc = bpf_kprobe_multi_link_dealloc,
.fill_link_info = bpf_kprobe_multi_link_fill_link_info,
};
static void bpf_kprobe_multi_cookie_swap(void *a, void *b, int size, const void *priv)
@ -2872,6 +2908,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
link->addrs = addrs;
link->cookies = cookies;
link->cnt = cnt;
link->flags = flags;
if (cookies) {
/*

5
tools/include/uapi/linux/bpf.h
View file

@ -6439,6 +6439,11 @@ struct bpf_link_info {
__s32 priority;
__u32 flags;
} netfilter;
struct {
__aligned_u64 addrs;
__u32 count; /* in/out: kprobe_multi function count */
__u32 flags;
} kprobe_multi;
};
} __attribute__((aligned(8)));