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"
Acked-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
---
tools/bpf/bpftool/btf_dumper.c | 118 +++++++++++++++++++++++++++++----
tools/bpf/bpftool/main.h | 1 +
2 files changed, 107 insertions(+), 12 deletions(-)
diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c
index 3a9dc8bc97a8..76a807b963e0 100644
--- a/tools/bpf/bpftool/btf_dumper.c
+++ b/tools/bpf/bpftool/btf_dumper.c
@@ -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,
@@ -443,7 +534,7 @@ static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id,
btf_dumper_enum(d, t, data);
return 0;
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)");
@@ -488,10 +579,6 @@ 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)
{
@@ -600,8 +687,15 @@ 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("...");
}
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 5f6dccd43622..6db2398ae7e9 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -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
--
2.17.1
