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bpftool: Translate prog_id to its bpf prog_name

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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: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20200318171650.129252-1-kafai@fb.com
This commit is contained in:
Martin KaFai Lau 2020-03-18 10:16:50 -07:00 committed by Daniel Borkmann
parent 30255d3175
commit d5ae04da34
2 changed files with 107 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

118
tools/bpf/bpftool/btf_dumper.c
View File

@ -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
jsonw_printf(jw, "%lu", *(unsigned long *)data);
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(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);
BTF_PRINT_ARG("%s",
btf__name_by_offset(btf, arg->name_off));
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("...");
}

1
tools/bpf/bpftool/main.h
View File

@ -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