Display vmlinux BTF name and kernel module names when listing available BTFs
on the system.
In human-readable output mode, module BTFs are reported with "name
[module-name]", while vmlinux BTF will be reported as "name [vmlinux]".
Square brackets are added by bpftool and follow kernel convention when
displaying modules in human-readable text outputs.
[vmuser@archvm bpf]$ sudo ../../../bpf/bpftool/bpftool btf s
1: name [vmlinux] size 4082281B
6: size 2365B prog_ids 8,6 map_ids 3
7: name [button] size 46895B
8: name [pcspkr] size 42328B
9: name [serio_raw] size 39375B
10: name [floppy] size 57185B
11: name [i2c_core] size 76186B
12: name [crc32c_intel] size 16036B
13: name [i2c_piix4] size 50497B
14: name [irqbypass] size 14124B
15: name [kvm] size 197985B
16: name [kvm_intel] size 123564B
17: name [cryptd] size 42466B
18: name [crypto_simd] size 17187B
19: name [glue_helper] size 39205B
20: name [aesni_intel] size 41034B
25: size 36150B
pids bpftool(2519)
In JSON mode, two fields (boolean "kernel" and string "name") are reported for
each BTF object. vmlinux BTF is reported with name "vmlinux" (kernel itself
returns and empty name for vmlinux BTF).
[vmuser@archvm bpf]$ sudo ../../../bpf/bpftool/bpftool btf s -jp
[{
"id": 1,
"size": 4082281,
"prog_ids": [],
"map_ids": [],
"kernel": true,
"name": "vmlinux"
},{
"id": 6,
"size": 2365,
"prog_ids": [8,6
],
"map_ids": [3
],
"kernel": false
},{
"id": 7,
"size": 46895,
"prog_ids": [],
"map_ids": [],
"kernel": true,
"name": "button"
},{
...
Signed-off-by: Andrii Nakryiko <[email protected]>
---
tools/bpf/bpftool/btf.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
index c96b56e8e3a4..ed5e97157241 100644
--- a/tools/bpf/bpftool/btf.c
+++ b/tools/bpf/bpftool/btf.c
@@ -742,9 +742,14 @@ show_btf_plain(struct bpf_btf_info *info, int fd,
struct btf_attach_table *btf_map_table)
{
struct btf_attach_point *obj;
+ const char *name = u64_to_ptr(info->name);
int n;
printf("%u: ", info->id);
+ if (info->kernel_btf)
+ printf("name [%s] ", name);
+ else if (name && name[0])
+ printf("name %s ", name);
printf("size %uB", info->btf_size);
n = 0;
@@ -771,6 +776,7 @@ show_btf_json(struct bpf_btf_info *info, int fd,
struct btf_attach_table *btf_map_table)
{
struct btf_attach_point *obj;
+ const char *name = u64_to_ptr(info->name);
jsonw_start_object(json_wtr); /* btf object */
jsonw_uint_field(json_wtr, "id", info->id);
@@ -796,6 +802,11 @@ show_btf_json(struct bpf_btf_info *info, int fd,
emit_obj_refs_json(&refs_table, info->id, json_wtr); /* pids */
+ jsonw_bool_field(json_wtr, "kernel", info->kernel_btf);
+
+ if (name && name[0])
+ jsonw_string_field(json_wtr, "name", name);
+
jsonw_end_object(json_wtr); /* btf object */
}
@@ -803,15 +814,30 @@ static int
show_btf(int fd, struct btf_attach_table *btf_prog_table,
struct btf_attach_table *btf_map_table)
{
- struct bpf_btf_info info = {};
+ struct bpf_btf_info info;
__u32 len = sizeof(info);
+ char name[64];
int err;
+ memset(&info, 0, sizeof(info));
err = bpf_obj_get_info_by_fd(fd, &info, &len);
if (err) {
p_err("can't get BTF object info: %s", strerror(errno));
return -1;
}
+ /* if kernel support emitting BTF object name, pass name pointer */
+ if (info.name_len) {
+ memset(&info, 0, sizeof(info));
+ info.name_len = sizeof(name);
+ info.name = ptr_to_u64(name);
+ len = sizeof(info);
+
+ err = bpf_obj_get_info_by_fd(fd, &info, &len);
+ if (err) {
+ p_err("can't get BTF object info: %s", strerror(errno));
+ return -1;
+ }
+ }
if (json_output)
show_btf_json(&info, fd, btf_prog_table, btf_map_table);
--
2.24.1
On Thu, 5 Nov 2020, Andrii Nakryiko wrote:
> Display vmlinux BTF name and kernel module names when listing available BTFs
> on the system.
>
> In human-readable output mode, module BTFs are reported with "name
> [module-name]", while vmlinux BTF will be reported as "name [vmlinux]".
> Square brackets are added by bpftool and follow kernel convention when
> displaying modules in human-readable text outputs.
>
I had a go at testing this and all looks good, but I was curious
if "bpftool btf dump" is expected to work with module BTF? I see
the various modules in /sys/kernel/btf, but if I run:
# bpftool btf dump file /sys/kernel/btf/ixgbe
Error: failed to load BTF from /sys/kernel/btf/ixgbe: Invalid argument
...while it still works for vmlinux:
# bpftool btf dump file /sys/kernel/btf/vmlinux
[1] INT '(anon)' size=4 bits_offset=0 nr_bits=32 encoding=(none)
[2] INT 'long unsigned int' size=8 bits_offset=0 nr_bits=64
encoding=(none)
...
"bpftool btf show" works for ixgbe:
# bpftool btf show|grep ixgbe
19: name [ixgbe] size 182074B
Is this perhaps not expected to work yet? (I updated pahole
to the latest changes etc and BTF generation seemed to work
fine for modules during kernel build).
For the "bpftool btf show" functionality, feel free to add
Tested-by: Alan Maguire <[email protected]>
Thanks!
Alan
On Mon, Nov 9, 2020 at 8:43 AM Alan Maguire <[email protected]> wrote:
>
> On Thu, 5 Nov 2020, Andrii Nakryiko wrote:
>
> > Display vmlinux BTF name and kernel module names when listing available BTFs
> > on the system.
> >
> > In human-readable output mode, module BTFs are reported with "name
> > [module-name]", while vmlinux BTF will be reported as "name [vmlinux]".
> > Square brackets are added by bpftool and follow kernel convention when
> > displaying modules in human-readable text outputs.
> >
>
> I had a go at testing this and all looks good, but I was curious
> if "bpftool btf dump" is expected to work with module BTF? I see
> the various modules in /sys/kernel/btf, but if I run:
>
> # bpftool btf dump file /sys/kernel/btf/ixgbe
You need to specify vmlinux as a base BTF. There is a -B flag for
that, added in [0]. So just add -B /sys/kernel/btf/vmlinux. I think we
might want to teach bpftool to do this automatically if we see that
file points at module BTF in /sys/kernel/btf, as a convenience
feature.
[0] https://patchwork.kernel.org/project/netdevbpf/patch/[email protected]/
> Error: failed to load BTF from /sys/kernel/btf/ixgbe: Invalid argument
>
> ...while it still works for vmlinux:
>
> # bpftool btf dump file /sys/kernel/btf/vmlinux
> [1] INT '(anon)' size=4 bits_offset=0 nr_bits=32 encoding=(none)
> [2] INT 'long unsigned int' size=8 bits_offset=0 nr_bits=64
> encoding=(none)
> ...
>
> "bpftool btf show" works for ixgbe:
>
> # bpftool btf show|grep ixgbe
> 19: name [ixgbe] size 182074B
>
> Is this perhaps not expected to work yet? (I updated pahole
> to the latest changes etc and BTF generation seemed to work
> fine for modules during kernel build).
>
> For the "bpftool btf show" functionality, feel free to add
>
> Tested-by: Alan Maguire <[email protected]>
Ok, thanks.
>
> Thanks!
>
> Alan