Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 34be1646 authored by Song Liu's avatar Song Liu Committed by Arnaldo Carvalho de Melo
Browse files

tools lib bpf: Introduce bpf_program__get_prog_info_linear() 



Currently, bpf_prog_info includes 9 arrays. The user has the option to
fetch any combination of these arrays. However, this requires a lot of
handling.

This work becomes more tricky when we need to store bpf_prog_info to a
file, because these arrays are allocated independently.

This patch introduces 'struct bpf_prog_info_linear', which stores arrays
of bpf_prog_info in continuous memory.

Helper functions are introduced to unify the work to get different sets
of bpf_prog_info.  Specifically, bpf_program__get_prog_info_linear()
allows the user to select which arrays to fetch, and handles details for
the user.

Please see the comments right before 'enum bpf_prog_info_array' for more
details and examples.

Signed-off-by: default avatarSong Liu <songliubraving@fb.com>
Reviewed-by: default avatarJiri Olsa <jolsa@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lkml.kernel.org/r/ce92c091-e80d-a0c1-4aa0-987706c42b20@iogearbox.net


Tested-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: kernel-team@fb.com
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stanislav Fomichev <sdf@google.com>
Link: http://lkml.kernel.org/r/20190312053051.2690567-3-songliubraving@fb.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 71184c6a

tools/lib/bpf/libbpf.c

+251 −0
Original line number Diff line number Diff line
@@ -112,6 +112,11 @@ void libbpf_print(enum libbpf_print_level level, const char *format, ...) 
# define LIBBPF_ELF_C_READ_MMAP ELF_C_READ

#endif



static inline __u64 ptr_to_u64(const void *ptr)

{

	return (__u64) (unsigned long) ptr;

}



struct bpf_capabilities {

	/* v4.14: kernel support for program & map names. */

	__u32 name:1;
@@ -2997,3 +3002,249 @@ bpf_perf_event_read_simple(void *mmap_mem, size_t mmap_size, size_t page_size, 
	ring_buffer_write_tail(header, data_tail);

	return ret;

}



struct bpf_prog_info_array_desc {

	int	array_offset;	/* e.g. offset of jited_prog_insns */

	int	count_offset;	/* e.g. offset of jited_prog_len */

	int	size_offset;	/* > 0: offset of rec size,

				 * < 0: fix size of -size_offset

				 */

};



static struct bpf_prog_info_array_desc bpf_prog_info_array_desc[] = {

	[BPF_PROG_INFO_JITED_INSNS] = {

		offsetof(struct bpf_prog_info, jited_prog_insns),

		offsetof(struct bpf_prog_info, jited_prog_len),

		-1,

	},

	[BPF_PROG_INFO_XLATED_INSNS] = {

		offsetof(struct bpf_prog_info, xlated_prog_insns),

		offsetof(struct bpf_prog_info, xlated_prog_len),

		-1,

	},

	[BPF_PROG_INFO_MAP_IDS] = {

		offsetof(struct bpf_prog_info, map_ids),

		offsetof(struct bpf_prog_info, nr_map_ids),

		-(int)sizeof(__u32),

	},

	[BPF_PROG_INFO_JITED_KSYMS] = {

		offsetof(struct bpf_prog_info, jited_ksyms),

		offsetof(struct bpf_prog_info, nr_jited_ksyms),

		-(int)sizeof(__u64),

	},

	[BPF_PROG_INFO_JITED_FUNC_LENS] = {

		offsetof(struct bpf_prog_info, jited_func_lens),

		offsetof(struct bpf_prog_info, nr_jited_func_lens),

		-(int)sizeof(__u32),

	},

	[BPF_PROG_INFO_FUNC_INFO] = {

		offsetof(struct bpf_prog_info, func_info),

		offsetof(struct bpf_prog_info, nr_func_info),

		offsetof(struct bpf_prog_info, func_info_rec_size),

	},

	[BPF_PROG_INFO_LINE_INFO] = {

		offsetof(struct bpf_prog_info, line_info),

		offsetof(struct bpf_prog_info, nr_line_info),

		offsetof(struct bpf_prog_info, line_info_rec_size),

	},

	[BPF_PROG_INFO_JITED_LINE_INFO] = {

		offsetof(struct bpf_prog_info, jited_line_info),

		offsetof(struct bpf_prog_info, nr_jited_line_info),

		offsetof(struct bpf_prog_info, jited_line_info_rec_size),

	},

	[BPF_PROG_INFO_PROG_TAGS] = {

		offsetof(struct bpf_prog_info, prog_tags),

		offsetof(struct bpf_prog_info, nr_prog_tags),

		-(int)sizeof(__u8) * BPF_TAG_SIZE,

	},



};



static __u32 bpf_prog_info_read_offset_u32(struct bpf_prog_info *info, int offset)

{

	__u32 *array = (__u32 *)info;



	if (offset >= 0)

		return array[offset / sizeof(__u32)];

	return -(int)offset;

}



static __u64 bpf_prog_info_read_offset_u64(struct bpf_prog_info *info, int offset)

{

	__u64 *array = (__u64 *)info;



	if (offset >= 0)

		return array[offset / sizeof(__u64)];

	return -(int)offset;

}



static void bpf_prog_info_set_offset_u32(struct bpf_prog_info *info, int offset,

					 __u32 val)

{

	__u32 *array = (__u32 *)info;



	if (offset >= 0)

		array[offset / sizeof(__u32)] = val;

}



static void bpf_prog_info_set_offset_u64(struct bpf_prog_info *info, int offset,

					 __u64 val)

{

	__u64 *array = (__u64 *)info;



	if (offset >= 0)

		array[offset / sizeof(__u64)] = val;

}



struct bpf_prog_info_linear *

bpf_program__get_prog_info_linear(int fd, __u64 arrays)

{

	struct bpf_prog_info_linear *info_linear;

	struct bpf_prog_info info = {};

	__u32 info_len = sizeof(info);

	__u32 data_len = 0;

	int i, err;

	void *ptr;



	if (arrays >> BPF_PROG_INFO_LAST_ARRAY)

		return ERR_PTR(-EINVAL);



	/* step 1: get array dimensions */

	err = bpf_obj_get_info_by_fd(fd, &info, &info_len);

	if (err) {

		pr_debug("can't get prog info: %s", strerror(errno));

		return ERR_PTR(-EFAULT);

	}



	/* step 2: calculate total size of all arrays */

	for (i = BPF_PROG_INFO_FIRST_ARRAY; i < BPF_PROG_INFO_LAST_ARRAY; ++i) {

		bool include_array = (arrays & (1UL << i)) > 0;

		struct bpf_prog_info_array_desc *desc;

		__u32 count, size;



		desc = bpf_prog_info_array_desc + i;



		/* kernel is too old to support this field */

		if (info_len < desc->array_offset + sizeof(__u32) ||

		    info_len < desc->count_offset + sizeof(__u32) ||

		    (desc->size_offset > 0 && info_len < desc->size_offset))

			include_array = false;



		if (!include_array) {

			arrays &= ~(1UL << i);	/* clear the bit */

			continue;

		}



		count = bpf_prog_info_read_offset_u32(&info, desc->count_offset);

		size  = bpf_prog_info_read_offset_u32(&info, desc->size_offset);



		data_len += count * size;

	}



	/* step 3: allocate continuous memory */

	data_len = roundup(data_len, sizeof(__u64));

	info_linear = malloc(sizeof(struct bpf_prog_info_linear) + data_len);

	if (!info_linear)

		return ERR_PTR(-ENOMEM);



	/* step 4: fill data to info_linear->info */

	info_linear->arrays = arrays;

	memset(&info_linear->info, 0, sizeof(info));

	ptr = info_linear->data;



	for (i = BPF_PROG_INFO_FIRST_ARRAY; i < BPF_PROG_INFO_LAST_ARRAY; ++i) {

		struct bpf_prog_info_array_desc *desc;

		__u32 count, size;



		if ((arrays & (1UL << i)) == 0)

			continue;



		desc  = bpf_prog_info_array_desc + i;

		count = bpf_prog_info_read_offset_u32(&info, desc->count_offset);

		size  = bpf_prog_info_read_offset_u32(&info, desc->size_offset);

		bpf_prog_info_set_offset_u32(&info_linear->info,

					     desc->count_offset, count);

		bpf_prog_info_set_offset_u32(&info_linear->info,

					     desc->size_offset, size);

		bpf_prog_info_set_offset_u64(&info_linear->info,

					     desc->array_offset,

					     ptr_to_u64(ptr));

		ptr += count * size;

	}



	/* step 5: call syscall again to get required arrays */

	err = bpf_obj_get_info_by_fd(fd, &info_linear->info, &info_len);

	if (err) {

		pr_debug("can't get prog info: %s", strerror(errno));

		free(info_linear);

		return ERR_PTR(-EFAULT);

	}



	/* step 6: verify the data */

	for (i = BPF_PROG_INFO_FIRST_ARRAY; i < BPF_PROG_INFO_LAST_ARRAY; ++i) {

		struct bpf_prog_info_array_desc *desc;

		__u32 v1, v2;



		if ((arrays & (1UL << i)) == 0)

			continue;



		desc = bpf_prog_info_array_desc + i;

		v1 = bpf_prog_info_read_offset_u32(&info, desc->count_offset);

		v2 = bpf_prog_info_read_offset_u32(&info_linear->info,

						   desc->count_offset);

		if (v1 != v2)

			pr_warning("%s: mismatch in element count\n", __func__);



		v1 = bpf_prog_info_read_offset_u32(&info, desc->size_offset);

		v2 = bpf_prog_info_read_offset_u32(&info_linear->info,

						   desc->size_offset);

		if (v1 != v2)

			pr_warning("%s: mismatch in rec size\n", __func__);

	}



	/* step 7: update info_len and data_len */

	info_linear->info_len = sizeof(struct bpf_prog_info);

	info_linear->data_len = data_len;



	return info_linear;

}



void bpf_program__bpil_addr_to_offs(struct bpf_prog_info_linear *info_linear)

{

	int i;



	for (i = BPF_PROG_INFO_FIRST_ARRAY; i < BPF_PROG_INFO_LAST_ARRAY; ++i) {

		struct bpf_prog_info_array_desc *desc;

		__u64 addr, offs;



		if ((info_linear->arrays & (1UL << i)) == 0)

			continue;



		desc = bpf_prog_info_array_desc + i;

		addr = bpf_prog_info_read_offset_u64(&info_linear->info,

						     desc->array_offset);

		offs = addr - ptr_to_u64(info_linear->data);

		bpf_prog_info_set_offset_u64(&info_linear->info,

					     desc->array_offset, offs);

	}

}



void bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear)

{

	int i;



	for (i = BPF_PROG_INFO_FIRST_ARRAY; i < BPF_PROG_INFO_LAST_ARRAY; ++i) {

		struct bpf_prog_info_array_desc *desc;

		__u64 addr, offs;



		if ((info_linear->arrays & (1UL << i)) == 0)

			continue;



		desc = bpf_prog_info_array_desc + i;

		offs = bpf_prog_info_read_offset_u64(&info_linear->info,

						     desc->array_offset);

		addr = offs + ptr_to_u64(info_linear->data);

		bpf_prog_info_set_offset_u64(&info_linear->info,

					     desc->array_offset, addr);

	}

}

tools/lib/bpf/libbpf.h

+63 −0
Original line number Diff line number Diff line
@@ -378,6 +378,69 @@ LIBBPF_API bool bpf_probe_map_type(enum bpf_map_type map_type, __u32 ifindex); 
LIBBPF_API bool bpf_probe_helper(enum bpf_func_id id,

				 enum bpf_prog_type prog_type, __u32 ifindex);



/*

 * Get bpf_prog_info in continuous memory

 *

 * struct bpf_prog_info has multiple arrays. The user has option to choose

 * arrays to fetch from kernel. The following APIs provide an uniform way to

 * fetch these data. All arrays in bpf_prog_info are stored in a single

 * continuous memory region. This makes it easy to store the info in a

 * file.

 *

 * Before writing bpf_prog_info_linear to files, it is necessary to

 * translate pointers in bpf_prog_info to offsets. Helper functions

 * bpf_program__bpil_addr_to_offs() and bpf_program__bpil_offs_to_addr()

 * are introduced to switch between pointers and offsets.

 *

 * Examples:

 *   # To fetch map_ids and prog_tags:

 *   __u64 arrays = (1UL << BPF_PROG_INFO_MAP_IDS) |

 *           (1UL << BPF_PROG_INFO_PROG_TAGS);

 *   struct bpf_prog_info_linear *info_linear =

 *           bpf_program__get_prog_info_linear(fd, arrays);

 *

 *   # To save data in file

 *   bpf_program__bpil_addr_to_offs(info_linear);

 *   write(f, info_linear, sizeof(*info_linear) + info_linear->data_len);

 *

 *   # To read data from file

 *   read(f, info_linear, <proper_size>);

 *   bpf_program__bpil_offs_to_addr(info_linear);

 */

enum bpf_prog_info_array {

	BPF_PROG_INFO_FIRST_ARRAY = 0,

	BPF_PROG_INFO_JITED_INSNS = 0,

	BPF_PROG_INFO_XLATED_INSNS,

	BPF_PROG_INFO_MAP_IDS,

	BPF_PROG_INFO_JITED_KSYMS,

	BPF_PROG_INFO_JITED_FUNC_LENS,

	BPF_PROG_INFO_FUNC_INFO,

	BPF_PROG_INFO_LINE_INFO,

	BPF_PROG_INFO_JITED_LINE_INFO,

	BPF_PROG_INFO_PROG_TAGS,

	BPF_PROG_INFO_LAST_ARRAY,

};



struct bpf_prog_info_linear {

	/* size of struct bpf_prog_info, when the tool is compiled */

	__u32			info_len;

	/* total bytes allocated for data, round up to 8 bytes */

	__u32			data_len;

	/* which arrays are included in data */

	__u64			arrays;

	struct bpf_prog_info	info;

	__u8			data[];

};



LIBBPF_API struct bpf_prog_info_linear *

bpf_program__get_prog_info_linear(int fd, __u64 arrays);



LIBBPF_API void

bpf_program__bpil_addr_to_offs(struct bpf_prog_info_linear *info_linear);



LIBBPF_API void

bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear);



#ifdef __cplusplus

} /* extern "C" */

#endif

tools/lib/bpf/libbpf.map

+3 −0
Original line number Diff line number Diff line
@@ -153,4 +153,7 @@ LIBBPF_0.0.2 { 
		xsk_socket__delete;

		xsk_umem__fd;

		xsk_socket__fd;

		bpf_program__get_prog_info_linear;

		bpf_program__bpil_addr_to_offs;

		bpf_program__bpil_offs_to_addr;

} LIBBPF_0.0.1;