Commit 7ac8d0d2 authored by Yafang Shao's avatar Yafang Shao Committed by Alexei Starovoitov
Browse files

bpf: Support ->fill_link_info for kprobe_multi 



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: default avatarYafang Shao <laoar.shao@gmail.com>
Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230709025630.3735-2-laoar.shao@gmail.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 07018b57

include/uapi/linux/bpf.h

+5 −0
Original line number Diff line number Diff line
@@ -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)));

kernel/trace/bpf_trace.c

+37 −0
Original line number Diff line number Diff line
@@ -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) {

		/*

tools/include/uapi/linux/bpf.h

+5 −0
Original line number Diff line number Diff line
@@ -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)));