Commit d5ae04da authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Daniel Borkmann
Browse files

bpftool: Translate prog_id to its bpf prog_name 



The kernel struct_ops obj has kernel's func ptrs implemented by bpf_progs.
The bpf prog_id is stored as the value of the func ptr for introspection
purpose.  In the latter patch, a struct_ops dump subcmd will be added
to introspect these func ptrs.  It is desired to print the actual bpf
prog_name instead of only printing the prog_id.

Since struct_ops is the only usecase storing prog_id in the func ptr,
this patch adds a prog_id_as_func_ptr bool (default is false) to
"struct btf_dumper" in order not to mis-interpret the ptr value
for the other existing use-cases.

While printing a func_ptr as a bpf prog_name,
this patch also prefix the bpf prog_name with the ptr's func_proto.
[ Note that it is the ptr's func_proto instead of the bpf prog's
  func_proto ]
It reuses the current btf_dump_func() to obtain the ptr's func_proto
string.

Here is an example from the bpf_cubic.c:
"void (struct sock *, u32, u32) bictcp_cong_avoid/prog_id:140"

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarQuentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20200318171650.129252-1-kafai@fb.com
parent 30255d31

tools/bpf/bpftool/btf_dumper.c

+106 −12
Original line number Diff line number Diff line
@@ -4,11 +4,13 @@ 
#include <ctype.h>

#include <stdio.h> /* for (FILE *) used by json_writer */

#include <string.h>

#include <unistd.h>

#include <asm/byteorder.h>

#include <linux/bitops.h>

#include <linux/btf.h>

#include <linux/err.h>

#include <bpf/btf.h>

#include <bpf/bpf.h>



#include "json_writer.h"

#include "main.h"
@@ -22,13 +24,102 @@ 
static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id,

			      __u8 bit_offset, const void *data);



static void btf_dumper_ptr(const void *data, json_writer_t *jw,

			   bool is_plain_text)

static int btf_dump_func(const struct btf *btf, char *func_sig,

			 const struct btf_type *func_proto,

			 const struct btf_type *func, int pos, int size);



static int dump_prog_id_as_func_ptr(const struct btf_dumper *d,

				    const struct btf_type *func_proto,

				    __u32 prog_id)

{

	if (is_plain_text)

		jsonw_printf(jw, "%p", *(void **)data);

	struct bpf_prog_info_linear *prog_info = NULL;

	const struct btf_type *func_type;

	const char *prog_name = NULL;

	struct bpf_func_info *finfo;

	struct btf *prog_btf = NULL;

	struct bpf_prog_info *info;

	int prog_fd, func_sig_len;

	char prog_str[1024];



	/* Get the ptr's func_proto */

	func_sig_len = btf_dump_func(d->btf, prog_str, func_proto, NULL, 0,

				     sizeof(prog_str));

	if (func_sig_len == -1)

		return -1;



	if (!prog_id)

		goto print;



	/* Get the bpf_prog's name.  Obtain from func_info. */

	prog_fd = bpf_prog_get_fd_by_id(prog_id);

	if (prog_fd == -1)

		goto print;



	prog_info = bpf_program__get_prog_info_linear(prog_fd,

						1UL << BPF_PROG_INFO_FUNC_INFO);

	close(prog_fd);

	if (IS_ERR(prog_info)) {

		prog_info = NULL;

		goto print;

	}

	info = &prog_info->info;



	if (!info->btf_id || !info->nr_func_info ||

	    btf__get_from_id(info->btf_id, &prog_btf))

		goto print;

	finfo = (struct bpf_func_info *)info->func_info;

	func_type = btf__type_by_id(prog_btf, finfo->type_id);

	if (!func_type || !btf_is_func(func_type))

		goto print;



	prog_name = btf__name_by_offset(prog_btf, func_type->name_off);



print:

	if (!prog_id)

		snprintf(&prog_str[func_sig_len],

			 sizeof(prog_str) - func_sig_len, " 0");

	else if (prog_name)

		snprintf(&prog_str[func_sig_len],

			 sizeof(prog_str) - func_sig_len,

			 " %s/prog_id:%u", prog_name, prog_id);

	else

		snprintf(&prog_str[func_sig_len],

			 sizeof(prog_str) - func_sig_len,

			 " <unknown_prog_name>/prog_id:%u", prog_id);



	prog_str[sizeof(prog_str) - 1] = '\0';

	jsonw_string(d->jw, prog_str);

	btf__free(prog_btf);

	free(prog_info);

	return 0;

}



static void btf_dumper_ptr(const struct btf_dumper *d,

			   const struct btf_type *t,

			   const void *data)

{

	unsigned long value = *(unsigned long *)data;

	const struct btf_type *ptr_type;

	__s32 ptr_type_id;



	if (!d->prog_id_as_func_ptr || value > UINT32_MAX)

		goto print_ptr_value;



	ptr_type_id = btf__resolve_type(d->btf, t->type);

	if (ptr_type_id < 0)

		goto print_ptr_value;

	ptr_type = btf__type_by_id(d->btf, ptr_type_id);

	if (!ptr_type || !btf_is_func_proto(ptr_type))

		goto print_ptr_value;



	if (!dump_prog_id_as_func_ptr(d, ptr_type, value))

		return;



print_ptr_value:

	if (d->is_plain_text)

		jsonw_printf(d->jw, "%p", (void *)value);

	else

		jsonw_printf(jw, "%lu", *(unsigned long *)data);

		jsonw_printf(d->jw, "%lu", value);

}



static int btf_dumper_modifier(const struct btf_dumper *d, __u32 type_id,
@@ -442,7 +533,7 @@ static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id, 
	case BTF_KIND_ENUM:

		return btf_dumper_enum(d, t, data);

	case BTF_KIND_PTR:

		btf_dumper_ptr(data, d->jw, d->is_plain_text);

		btf_dumper_ptr(d, t, data);

		return 0;

	case BTF_KIND_UNKN:

		jsonw_printf(d->jw, "(unknown)");
@@ -487,10 +578,6 @@ int btf_dumper_type(const struct btf_dumper *d, __u32 type_id, 
			return -1;					\

	} while (0)



static int btf_dump_func(const struct btf *btf, char *func_sig,

			 const struct btf_type *func_proto,

			 const struct btf_type *func, int pos, int size);



static int __btf_dumper_type_only(const struct btf *btf, __u32 type_id,

				  char *func_sig, int pos, int size)

{
@@ -599,8 +686,15 @@ static int btf_dump_func(const struct btf *btf, char *func_sig, 
			BTF_PRINT_ARG(", ");

		if (arg->type) {

			BTF_PRINT_TYPE(arg->type);

			if (arg->name_off)

				BTF_PRINT_ARG("%s",

					      btf__name_by_offset(btf, arg->name_off));

			else if (pos && func_sig[pos - 1] == ' ')

				/* Remove unnecessary space for

				 * FUNC_PROTO that does not have

				 * arg->name_off

				 */

				func_sig[--pos] = '\0';

		} else {

			BTF_PRINT_ARG("...");

		}

tools/bpf/bpftool/main.h

+1 −0
Original line number Diff line number Diff line
@@ -205,6 +205,7 @@ struct btf_dumper { 
	const struct btf *btf;

	json_writer_t *jw;

	bool is_plain_text;

	bool prog_id_as_func_ptr;

};



/* btf_dumper_type - print data along with type information

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