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Date:   Wed, 11 Dec 2019 19:38:11 +0000
From:   Martin Lau <kafai@...com>
To:     Andrii Nakryiko <andriin@...com>
CC:     "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "andrii.nakryiko@...il.com" <andrii.nakryiko@...il.com>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [Potential Spoof] [PATCH bpf-next 06/15] libbpf: expose BPF
 program's function name

On Mon, Dec 09, 2019 at 05:14:29PM -0800, Andrii Nakryiko wrote:
> Add APIs to get BPF program function name, as opposed to bpf_program__title(),
> which returns BPF program function's section name. Function name has a benefit
> of being a valid C identifier and uniquely identifies a specific BPF program,
> while section name can be duplicated across multiple independent BPF programs.
> 
> Add also bpf_object__find_program_by_name(), similar to
> bpf_object__find_program_by_title(), to facilitate looking up BPF programs by
> their C function names.
> 
> Convert one of selftests to new API for look up.
> 
> Signed-off-by: Andrii Nakryiko <andriin@...com>
> ---
>  tools/lib/bpf/libbpf.c                        | 28 +++++++++++++++----
>  tools/lib/bpf/libbpf.h                        |  9 ++++--
>  tools/lib/bpf/libbpf.map                      |  2 ++
>  .../selftests/bpf/prog_tests/rdonly_maps.c    | 11 +++-----
>  4 files changed, 36 insertions(+), 14 deletions(-)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index edfe1cf1e940..f13752c4d271 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -209,8 +209,8 @@ static const char * const libbpf_type_to_btf_name[] = {
>  };
>  
>  struct bpf_map {
> -	int fd;
>  	char *name;
> +	int fd;
This change, and

>  	int sec_idx;
>  	size_t sec_offset;
>  	int map_ifindex;
> @@ -1384,7 +1384,7 @@ static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
>  }
>  
>  static int bpf_object__init_maps(struct bpf_object *obj,
> -				 struct bpf_object_open_opts *opts)
> +				 const struct bpf_object_open_opts *opts)
here, and a few other const changes,

are all good changes.  If they are not in a separate patch, it will be useful
to the reviewer if there is commit messages mentioning there are some
unrelated cleanup changes.  I have been looking at where it may cause
compiler warning because of this change, or I missed something?

>  {
>  	const char *pin_root_path = OPTS_GET(opts, pin_root_path, NULL);
>  	bool strict = !OPTS_GET(opts, relaxed_maps, false);
> @@ -1748,6 +1748,19 @@ bpf_object__find_program_by_title(const struct bpf_object *obj,
>  	return NULL;
>  }
>  
> +struct bpf_program *
> +bpf_object__find_program_by_name(const struct bpf_object *obj,
> +				 const char *name)
> +{
> +	struct bpf_program *prog;
> +
> +	bpf_object__for_each_program(prog, obj) {
> +		if (!strcmp(prog->name, name))
> +			return prog;
> +	}
> +	return NULL;
> +}
> +
>  static bool bpf_object__shndx_is_data(const struct bpf_object *obj,
>  				      int shndx)
>  {
> @@ -3893,7 +3906,7 @@ static int libbpf_find_attach_btf_id(const char *name,
>  				     __u32 attach_prog_fd);
>  static struct bpf_object *
>  __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
> -		   struct bpf_object_open_opts *opts)
> +		   const struct bpf_object_open_opts *opts)
>  {
>  	struct bpf_program *prog;
>  	struct bpf_object *obj;
> @@ -4002,7 +4015,7 @@ struct bpf_object *bpf_object__open(const char *path)
>  }
>  
>  struct bpf_object *
> -bpf_object__open_file(const char *path, struct bpf_object_open_opts *opts)
> +bpf_object__open_file(const char *path, const struct bpf_object_open_opts *opts)
>  {
>  	if (!path)
>  		return ERR_PTR(-EINVAL);
> @@ -4014,7 +4027,7 @@ bpf_object__open_file(const char *path, struct bpf_object_open_opts *opts)
>  
>  struct bpf_object *
>  bpf_object__open_mem(const void *obj_buf, size_t obj_buf_sz,
> -		     struct bpf_object_open_opts *opts)
> +		     const struct bpf_object_open_opts *opts)
>  {
>  	if (!obj_buf || obj_buf_sz == 0)
>  		return ERR_PTR(-EINVAL);
> @@ -4819,6 +4832,11 @@ void bpf_program__set_ifindex(struct bpf_program *prog, __u32 ifindex)
>  	prog->prog_ifindex = ifindex;
>  }
>  
> +const char *bpf_program__name(const struct bpf_program *prog)
> +{
> +	return prog->name;
> +}
> +
>  const char *bpf_program__title(const struct bpf_program *prog, bool needs_copy)
>  {
>  	const char *title;
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index fa803dde1f46..7fa583ebe56f 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -114,10 +114,10 @@ struct bpf_object_open_opts {
>  
>  LIBBPF_API struct bpf_object *bpf_object__open(const char *path);
>  LIBBPF_API struct bpf_object *
> -bpf_object__open_file(const char *path, struct bpf_object_open_opts *opts);
> +bpf_object__open_file(const char *path, const struct bpf_object_open_opts *opts);
>  LIBBPF_API struct bpf_object *
>  bpf_object__open_mem(const void *obj_buf, size_t obj_buf_sz,
> -		     struct bpf_object_open_opts *opts);
> +		     const struct bpf_object_open_opts *opts);
>  
>  /* deprecated bpf_object__open variants */
>  LIBBPF_API struct bpf_object *
> @@ -156,6 +156,7 @@ struct bpf_object_load_attr {
>  LIBBPF_API int bpf_object__load(struct bpf_object *obj);
>  LIBBPF_API int bpf_object__load_xattr(struct bpf_object_load_attr *attr);
>  LIBBPF_API int bpf_object__unload(struct bpf_object *obj);
> +
>  LIBBPF_API const char *bpf_object__name(const struct bpf_object *obj);
>  LIBBPF_API unsigned int bpf_object__kversion(const struct bpf_object *obj);
>  
> @@ -166,6 +167,9 @@ LIBBPF_API int bpf_object__btf_fd(const struct bpf_object *obj);
>  LIBBPF_API struct bpf_program *
>  bpf_object__find_program_by_title(const struct bpf_object *obj,
>  				  const char *title);
> +LIBBPF_API struct bpf_program *
> +bpf_object__find_program_by_name(const struct bpf_object *obj,
> +				 const char *name);
>  
>  LIBBPF_API struct bpf_object *bpf_object__next(struct bpf_object *prev);
>  #define bpf_object__for_each_safe(pos, tmp)			\
> @@ -209,6 +213,7 @@ LIBBPF_API void *bpf_program__priv(const struct bpf_program *prog);
>  LIBBPF_API void bpf_program__set_ifindex(struct bpf_program *prog,
>  					 __u32 ifindex);
>  
> +LIBBPF_API const char *bpf_program__name(const struct bpf_program *prog);
>  LIBBPF_API const char *bpf_program__title(const struct bpf_program *prog,
>  					  bool needs_copy);
>  
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 757a88f64b5a..f2b2fa0f5c2a 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -211,5 +211,7 @@ LIBBPF_0.0.6 {
>  
>  LIBBPF_0.0.7 {
>  	global:
> +		bpf_object__find_program_by_name;
>  		bpf_program__attach;
> +		bpf_program__name;
>  } LIBBPF_0.0.6;
> diff --git a/tools/testing/selftests/bpf/prog_tests/rdonly_maps.c b/tools/testing/selftests/bpf/prog_tests/rdonly_maps.c
> index d90acc13d1ec..563e12120e77 100644
> --- a/tools/testing/selftests/bpf/prog_tests/rdonly_maps.c
> +++ b/tools/testing/selftests/bpf/prog_tests/rdonly_maps.c
> @@ -16,14 +16,11 @@ struct rdonly_map_subtest {
>  
>  void test_rdonly_maps(void)
>  {
> -	const char *prog_name_skip_loop = "raw_tracepoint/sys_enter:skip_loop";
> -	const char *prog_name_part_loop = "raw_tracepoint/sys_enter:part_loop";
> -	const char *prog_name_full_loop = "raw_tracepoint/sys_enter:full_loop";
>  	const char *file = "test_rdonly_maps.o";
>  	struct rdonly_map_subtest subtests[] = {
> -		{ "skip loop", prog_name_skip_loop, 0, 0 },
> -		{ "part loop", prog_name_part_loop, 3, 2 + 3 + 4 },
> -		{ "full loop", prog_name_full_loop, 4, 2 + 3 + 4 + 5 },
> +		{ "skip loop", "skip_loop", 0, 0 },
> +		{ "part loop", "part_loop", 3, 2 + 3 + 4 },
> +		{ "full loop", "full_loop", 4, 2 + 3 + 4 + 5 },
>  	};
>  	int i, err, zero = 0, duration = 0;
>  	struct bpf_link *link = NULL;
> @@ -50,7 +47,7 @@ void test_rdonly_maps(void)
>  		if (!test__start_subtest(t->subtest_name))
>  			continue;
>  
> -		prog = bpf_object__find_program_by_title(obj, t->prog_name);
> +		prog = bpf_object__find_program_by_name(obj, t->prog_name);
>  		if (CHECK(!prog, "find_prog", "prog '%s' not found\n",
>  			  t->prog_name))
>  			goto cleanup;
> -- 
> 2.17.1
> 

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