* [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target
@ 2020-02-13 15:04 Eelco Chaudron
2020-02-13 15:32 ` Toke Høiland-Jørgensen
` (2 more replies)
0 siblings, 3 replies; 8+ messages in thread
From: Eelco Chaudron @ 2020-02-13 15:04 UTC (permalink / raw)
To: bpf; +Cc: davem, netdev, ast, daniel, kafai, songliubraving, yhs, andriin, toke
Currently when you want to attach a trace program to a bpf program
the section name needs to match the tracepoint/function semantics.
However the addition of the bpf_program__set_attach_target() API
allows you to specify the tracepoint/function dynamically.
The call flow would look something like this:
xdp_fd = bpf_prog_get_fd_by_id(id);
trace_obj = bpf_object__open_file("func.o", NULL);
prog = bpf_object__find_program_by_title(trace_obj,
"fentry/myfunc");
bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
bpf_program__set_attach_target(prog, xdp_fd,
"xdpfilt_blk_all");
bpf_object__load(trace_obj)
Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
---
v1 -> v2: Remove requirement for attach type name in API
tools/lib/bpf/libbpf.c | 33 +++++++++++++++++++++++++++++++--
tools/lib/bpf/libbpf.h | 4 ++++
tools/lib/bpf/libbpf.map | 1 +
3 files changed, 36 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 514b1a524abb..9b8cab995580 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4939,8 +4939,8 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
{
int err = 0, fd, i, btf_id;
- if (prog->type == BPF_PROG_TYPE_TRACING ||
- prog->type == BPF_PROG_TYPE_EXT) {
+ if ((prog->type == BPF_PROG_TYPE_TRACING ||
+ prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {
btf_id = libbpf_find_attach_btf_id(prog);
if (btf_id <= 0)
return btf_id;
@@ -8132,6 +8132,35 @@ void bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear)
}
}
+int bpf_program__set_attach_target(struct bpf_program *prog,
+ int attach_prog_fd,
+ const char *attach_func_name)
+{
+ int btf_id;
+
+ if (!prog || attach_prog_fd < 0 || !attach_func_name)
+ return -EINVAL;
+
+ if (attach_prog_fd)
+ btf_id = libbpf_find_prog_btf_id(attach_func_name,
+ attach_prog_fd);
+ else
+ btf_id = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
+ attach_func_name,
+ prog->expected_attach_type);
+
+ if (btf_id <= 0) {
+ if (!attach_prog_fd)
+ pr_warn("%s is not found in vmlinux BTF\n",
+ attach_func_name);
+ return btf_id;
+ }
+
+ prog->attach_btf_id = btf_id;
+ prog->attach_prog_fd = attach_prog_fd;
+ return 0;
+}
+
int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz)
{
int err = 0, n, len, start, end = -1;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 3fe12c9d1f92..02fc58a21a7f 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -334,6 +334,10 @@ LIBBPF_API void
bpf_program__set_expected_attach_type(struct bpf_program *prog,
enum bpf_attach_type type);
+LIBBPF_API int
+bpf_program__set_attach_target(struct bpf_program *prog, int attach_prog_fd,
+ const char *attach_func_name);
+
LIBBPF_API bool bpf_program__is_socket_filter(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_tracepoint(const struct bpf_program *prog);
LIBBPF_API bool bpf_program__is_raw_tracepoint(const struct bpf_program *prog);
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index b035122142bb..8aba5438a3f0 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -230,6 +230,7 @@ LIBBPF_0.0.7 {
bpf_program__name;
bpf_program__is_extension;
bpf_program__is_struct_ops;
+ bpf_program__set_attach_target;
bpf_program__set_extension;
bpf_program__set_struct_ops;
btf__align_of;
^ permalink raw reply related [flat|nested] 8+ messages in thread* Re: [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target
2020-02-13 15:04 [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target Eelco Chaudron
@ 2020-02-13 15:32 ` Toke Høiland-Jørgensen
2020-02-13 17:00 ` Eelco Chaudron
2020-02-13 17:13 ` Toke Høiland-Jørgensen
2020-02-13 17:42 ` Andrii Nakryiko
2 siblings, 1 reply; 8+ messages in thread
From: Toke Høiland-Jørgensen @ 2020-02-13 15:32 UTC (permalink / raw)
To: Eelco Chaudron, bpf
Cc: davem, netdev, ast, daniel, kafai, songliubraving, yhs, andriin
Eelco Chaudron <echaudro@redhat.com> writes:
> Currently when you want to attach a trace program to a bpf program
> the section name needs to match the tracepoint/function semantics.
>
> However the addition of the bpf_program__set_attach_target() API
> allows you to specify the tracepoint/function dynamically.
>
> The call flow would look something like this:
>
> xdp_fd = bpf_prog_get_fd_by_id(id);
> trace_obj = bpf_object__open_file("func.o", NULL);
> prog = bpf_object__find_program_by_title(trace_obj,
> "fentry/myfunc");
> bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
> bpf_program__set_attach_target(prog, xdp_fd,
> "xdpfilt_blk_all");
> bpf_object__load(trace_obj)
>
> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Hmm, one question about the attach_prog_fd usage:
> +int bpf_program__set_attach_target(struct bpf_program *prog,
> + int attach_prog_fd,
> + const char *attach_func_name)
> +{
> + int btf_id;
> +
> + if (!prog || attach_prog_fd < 0 || !attach_func_name)
> + return -EINVAL;
> +
> + if (attach_prog_fd)
> + btf_id = libbpf_find_prog_btf_id(attach_func_name,
> + attach_prog_fd);
> + else
> + btf_id = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
> + attach_func_name,
> + prog->expected_attach_type);
This implies that no one would end up using fd 0 as a legitimate prog
fd. This already seems to be the case for the existing code, but is that
really a safe assumption? Couldn't a caller that closes fd 0 (for
instance while forking) end up having it reused? Seems like this could
result in weird hard-to-debug bugs?
-Toke
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target
2020-02-13 15:32 ` Toke Høiland-Jørgensen
@ 2020-02-13 17:00 ` Eelco Chaudron
2020-02-13 17:13 ` Toke Høiland-Jørgensen
0 siblings, 1 reply; 8+ messages in thread
From: Eelco Chaudron @ 2020-02-13 17:00 UTC (permalink / raw)
To: Toke Høiland-Jørgensen
Cc: bpf, davem, netdev, ast, daniel, kafai, songliubraving, yhs, andriin
On 13 Feb 2020, at 16:32, Toke Høiland-Jørgensen wrote:
> Eelco Chaudron <echaudro@redhat.com> writes:
>
>> Currently when you want to attach a trace program to a bpf program
>> the section name needs to match the tracepoint/function semantics.
>>
>> However the addition of the bpf_program__set_attach_target() API
>> allows you to specify the tracepoint/function dynamically.
>>
>> The call flow would look something like this:
>>
>> xdp_fd = bpf_prog_get_fd_by_id(id);
>> trace_obj = bpf_object__open_file("func.o", NULL);
>> prog = bpf_object__find_program_by_title(trace_obj,
>> "fentry/myfunc");
>> bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
>> bpf_program__set_attach_target(prog, xdp_fd,
>> "xdpfilt_blk_all");
>> bpf_object__load(trace_obj)
>>
>> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
>
> Hmm, one question about the attach_prog_fd usage:
>
>> +int bpf_program__set_attach_target(struct bpf_program *prog,
>> + int attach_prog_fd,
>> + const char *attach_func_name)
>> +{
>> + int btf_id;
>> +
>> + if (!prog || attach_prog_fd < 0 || !attach_func_name)
>> + return -EINVAL;
>> +
>> + if (attach_prog_fd)
>> + btf_id = libbpf_find_prog_btf_id(attach_func_name,
>> + attach_prog_fd);
>> + else
>> + btf_id = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
>> + attach_func_name,
>> + prog->expected_attach_type);
>
> This implies that no one would end up using fd 0 as a legitimate prog
> fd. This already seems to be the case for the existing code, but is
> that
> really a safe assumption? Couldn't a caller that closes fd 0 (for
> instance while forking) end up having it reused? Seems like this could
> result in weird hard-to-debug bugs?
Yes, in theory, this can happen but it has nothing to do with this
specific patch. The existing code already assumes that attach_prog_fd ==
0 means attach to a kernel function :(
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target
2020-02-13 17:00 ` Eelco Chaudron
@ 2020-02-13 17:13 ` Toke Høiland-Jørgensen
0 siblings, 0 replies; 8+ messages in thread
From: Toke Høiland-Jørgensen @ 2020-02-13 17:13 UTC (permalink / raw)
To: Eelco Chaudron
Cc: bpf, davem, netdev, ast, daniel, kafai, songliubraving, yhs, andriin
"Eelco Chaudron" <echaudro@redhat.com> writes:
> On 13 Feb 2020, at 16:32, Toke Høiland-Jørgensen wrote:
>
>> Eelco Chaudron <echaudro@redhat.com> writes:
>>
>>> Currently when you want to attach a trace program to a bpf program
>>> the section name needs to match the tracepoint/function semantics.
>>>
>>> However the addition of the bpf_program__set_attach_target() API
>>> allows you to specify the tracepoint/function dynamically.
>>>
>>> The call flow would look something like this:
>>>
>>> xdp_fd = bpf_prog_get_fd_by_id(id);
>>> trace_obj = bpf_object__open_file("func.o", NULL);
>>> prog = bpf_object__find_program_by_title(trace_obj,
>>> "fentry/myfunc");
>>> bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
>>> bpf_program__set_attach_target(prog, xdp_fd,
>>> "xdpfilt_blk_all");
>>> bpf_object__load(trace_obj)
>>>
>>> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
>>
>> Hmm, one question about the attach_prog_fd usage:
>>
>>> +int bpf_program__set_attach_target(struct bpf_program *prog,
>>> + int attach_prog_fd,
>>> + const char *attach_func_name)
>>> +{
>>> + int btf_id;
>>> +
>>> + if (!prog || attach_prog_fd < 0 || !attach_func_name)
>>> + return -EINVAL;
>>> +
>>> + if (attach_prog_fd)
>>> + btf_id = libbpf_find_prog_btf_id(attach_func_name,
>>> + attach_prog_fd);
>>> + else
>>> + btf_id = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
>>> + attach_func_name,
>>> + prog->expected_attach_type);
>>
>> This implies that no one would end up using fd 0 as a legitimate prog
>> fd. This already seems to be the case for the existing code, but is
>> that
>> really a safe assumption? Couldn't a caller that closes fd 0 (for
>> instance while forking) end up having it reused? Seems like this could
>> result in weird hard-to-debug bugs?
>
>
> Yes, in theory, this can happen but it has nothing to do with this
> specific patch. The existing code already assumes that attach_prog_fd ==
> 0 means attach to a kernel function :(
Yup, I do realise you're just sticking to the existing behaviour. Seems
even the kernel does that check for fd != 0, so I guess that's ABI now.
Still not sure I believe this will not trip anyone up, though... :/
-Toke
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target
2020-02-13 15:04 [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target Eelco Chaudron
2020-02-13 15:32 ` Toke Høiland-Jørgensen
@ 2020-02-13 17:13 ` Toke Høiland-Jørgensen
2020-02-13 17:42 ` Andrii Nakryiko
2 siblings, 0 replies; 8+ messages in thread
From: Toke Høiland-Jørgensen @ 2020-02-13 17:13 UTC (permalink / raw)
To: Eelco Chaudron, bpf
Cc: davem, netdev, ast, daniel, kafai, songliubraving, yhs, andriin
Eelco Chaudron <echaudro@redhat.com> writes:
> Currently when you want to attach a trace program to a bpf program
> the section name needs to match the tracepoint/function semantics.
>
> However the addition of the bpf_program__set_attach_target() API
> allows you to specify the tracepoint/function dynamically.
>
> The call flow would look something like this:
>
> xdp_fd = bpf_prog_get_fd_by_id(id);
> trace_obj = bpf_object__open_file("func.o", NULL);
> prog = bpf_object__find_program_by_title(trace_obj,
> "fentry/myfunc");
> bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
> bpf_program__set_attach_target(prog, xdp_fd,
> "xdpfilt_blk_all");
> bpf_object__load(trace_obj)
>
> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target
2020-02-13 15:04 [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target Eelco Chaudron
2020-02-13 15:32 ` Toke Høiland-Jørgensen
2020-02-13 17:13 ` Toke Høiland-Jørgensen
@ 2020-02-13 17:42 ` Andrii Nakryiko
2020-02-14 7:34 ` Eelco Chaudron
2 siblings, 1 reply; 8+ messages in thread
From: Andrii Nakryiko @ 2020-02-13 17:42 UTC (permalink / raw)
To: Eelco Chaudron
Cc: bpf, David S. Miller, Networking, Alexei Starovoitov,
Daniel Borkmann, Martin Lau, Song Liu, Yonghong Song,
Andrii Nakryiko, Toke Høiland-Jørgensen
On Thu, Feb 13, 2020 at 7:05 AM Eelco Chaudron <echaudro@redhat.com> wrote:
>
> Currently when you want to attach a trace program to a bpf program
> the section name needs to match the tracepoint/function semantics.
>
> However the addition of the bpf_program__set_attach_target() API
> allows you to specify the tracepoint/function dynamically.
>
> The call flow would look something like this:
>
> xdp_fd = bpf_prog_get_fd_by_id(id);
> trace_obj = bpf_object__open_file("func.o", NULL);
> prog = bpf_object__find_program_by_title(trace_obj,
> "fentry/myfunc");
> bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
> bpf_program__set_attach_target(prog, xdp_fd,
> "xdpfilt_blk_all");
> bpf_object__load(trace_obj)
>
> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
> ---
API-wise this looks good, thanks! Please address feedback below and
re-submit once bpf-next opens. Can you please also convert one of
existing selftests using open_opts's attach_prog_fd to use this API
instead to have a demonstration there?
> v1 -> v2: Remove requirement for attach type name in API
>
> tools/lib/bpf/libbpf.c | 33 +++++++++++++++++++++++++++++++--
> tools/lib/bpf/libbpf.h | 4 ++++
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 36 insertions(+), 2 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 514b1a524abb..9b8cab995580 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -4939,8 +4939,8 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
> {
> int err = 0, fd, i, btf_id;
>
> - if (prog->type == BPF_PROG_TYPE_TRACING ||
> - prog->type == BPF_PROG_TYPE_EXT) {
> + if ((prog->type == BPF_PROG_TYPE_TRACING ||
> + prog->type == BPF_PROG_TYPE_EXT) && !prog->attach_btf_id) {
> btf_id = libbpf_find_attach_btf_id(prog);
> if (btf_id <= 0)
> return btf_id;
> @@ -8132,6 +8132,35 @@ void bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear)
> }
> }
>
> +int bpf_program__set_attach_target(struct bpf_program *prog,
> + int attach_prog_fd,
> + const char *attach_func_name)
> +{
> + int btf_id;
> +
> + if (!prog || attach_prog_fd < 0 || !attach_func_name)
> + return -EINVAL;
> +
> + if (attach_prog_fd)
> + btf_id = libbpf_find_prog_btf_id(attach_func_name,
> + attach_prog_fd);
> + else
> + btf_id = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
> + attach_func_name,
> + prog->expected_attach_type);
> +
> + if (btf_id <= 0) {
> + if (!attach_prog_fd)
> + pr_warn("%s is not found in vmlinux BTF\n",
> + attach_func_name);
libbpf_find_attach_btf_id's error reporting is misleading (it always
reports as if error happened with vmlinux BTF, even if attach_prog_fd
> 0). Could you please fix that and add better error reporting here
for attach_prog_fd>0 case here?
> + return btf_id;
> + }
> +
> + prog->attach_btf_id = btf_id;
> + prog->attach_prog_fd = attach_prog_fd;
> + return 0;
> +}
> +
> int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz)
> {
> int err = 0, n, len, start, end = -1;
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 3fe12c9d1f92..02fc58a21a7f 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -334,6 +334,10 @@ LIBBPF_API void
> bpf_program__set_expected_attach_type(struct bpf_program *prog,
> enum bpf_attach_type type);
>
> +LIBBPF_API int
> +bpf_program__set_attach_target(struct bpf_program *prog, int attach_prog_fd,
> + const char *attach_func_name);
> +
> LIBBPF_API bool bpf_program__is_socket_filter(const struct bpf_program *prog);
> LIBBPF_API bool bpf_program__is_tracepoint(const struct bpf_program *prog);
> LIBBPF_API bool bpf_program__is_raw_tracepoint(const struct bpf_program *prog);
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index b035122142bb..8aba5438a3f0 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -230,6 +230,7 @@ LIBBPF_0.0.7 {
> bpf_program__name;
> bpf_program__is_extension;
> bpf_program__is_struct_ops;
> + bpf_program__set_attach_target;
This will have to go into LIBBPF_0.0.8 once bpf-next opens. Please
rebase and re-send then.
> bpf_program__set_extension;
> bpf_program__set_struct_ops;
> btf__align_of;
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target
2020-02-13 17:42 ` Andrii Nakryiko
@ 2020-02-14 7:34 ` Eelco Chaudron
2020-02-14 17:53 ` Andrii Nakryiko
0 siblings, 1 reply; 8+ messages in thread
From: Eelco Chaudron @ 2020-02-14 7:34 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: bpf, David S. Miller, Networking, Alexei Starovoitov,
Daniel Borkmann, Martin Lau, Song Liu, Yonghong Song,
Andrii Nakryiko, Toke Høiland-Jørgensen
On 13 Feb 2020, at 18:42, Andrii Nakryiko wrote:
> On Thu, Feb 13, 2020 at 7:05 AM Eelco Chaudron <echaudro@redhat.com>
> wrote:
>>
>> Currently when you want to attach a trace program to a bpf program
>> the section name needs to match the tracepoint/function semantics.
>>
>> However the addition of the bpf_program__set_attach_target() API
>> allows you to specify the tracepoint/function dynamically.
>>
>> The call flow would look something like this:
>>
>> xdp_fd = bpf_prog_get_fd_by_id(id);
>> trace_obj = bpf_object__open_file("func.o", NULL);
>> prog = bpf_object__find_program_by_title(trace_obj,
>> "fentry/myfunc");
>> bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
>> bpf_program__set_attach_target(prog, xdp_fd,
>> "xdpfilt_blk_all");
>> bpf_object__load(trace_obj)
>>
>> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
>> ---
>
> API-wise this looks good, thanks! Please address feedback below and
> re-submit once bpf-next opens. Can you please also convert one of
> existing selftests using open_opts's attach_prog_fd to use this API
> instead to have a demonstration there?
Yes will update the one I added for bfp2bpf testing…
>> v1 -> v2: Remove requirement for attach type name in API
>>
>> tools/lib/bpf/libbpf.c | 33 +++++++++++++++++++++++++++++++--
>> tools/lib/bpf/libbpf.h | 4 ++++
>> tools/lib/bpf/libbpf.map | 1 +
>> 3 files changed, 36 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 514b1a524abb..9b8cab995580 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -4939,8 +4939,8 @@ int bpf_program__load(struct bpf_program *prog,
>> char *license, __u32 kern_ver)
>> {
>> int err = 0, fd, i, btf_id;
>>
>> - if (prog->type == BPF_PROG_TYPE_TRACING ||
>> - prog->type == BPF_PROG_TYPE_EXT) {
>> + if ((prog->type == BPF_PROG_TYPE_TRACING ||
>> + prog->type == BPF_PROG_TYPE_EXT) &&
>> !prog->attach_btf_id) {
>> btf_id = libbpf_find_attach_btf_id(prog);
>> if (btf_id <= 0)
>> return btf_id;
>> @@ -8132,6 +8132,35 @@ void bpf_program__bpil_offs_to_addr(struct
>> bpf_prog_info_linear *info_linear)
>> }
>> }
>>
>> +int bpf_program__set_attach_target(struct bpf_program *prog,
>> + int attach_prog_fd,
>> + const char *attach_func_name)
>> +{
>> + int btf_id;
>> +
>> + if (!prog || attach_prog_fd < 0 || !attach_func_name)
>> + return -EINVAL;
>> +
>> + if (attach_prog_fd)
>> + btf_id = libbpf_find_prog_btf_id(attach_func_name,
>> + attach_prog_fd);
>> + else
>> + btf_id =
>> __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
>> + attach_func_name,
>> +
>> prog->expected_attach_type);
>> +
>> + if (btf_id <= 0) {
>> + if (!attach_prog_fd)
>> + pr_warn("%s is not found in vmlinux BTF\n",
>> + attach_func_name);
>
> libbpf_find_attach_btf_id's error reporting is misleading (it always
> reports as if error happened with vmlinux BTF, even if attach_prog_fd
> 0). Could you please fix that and add better error reporting here
> for attach_prog_fd>0 case here?
>
I did not add log messages for the btf_id > 0 case as they are covered
in the libbpf_find_prog_btf_id() function. Please let me know if this is
not enough.
>> + return btf_id;
>> + }
>> +
>> + prog->attach_btf_id = btf_id;
>> + prog->attach_prog_fd = attach_prog_fd;
>> + return 0;
>> +}
>> +
>> int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz)
>> {
>> int err = 0, n, len, start, end = -1;
>> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
>> index 3fe12c9d1f92..02fc58a21a7f 100644
>> --- a/tools/lib/bpf/libbpf.h
>> +++ b/tools/lib/bpf/libbpf.h
>> @@ -334,6 +334,10 @@ LIBBPF_API void
>> bpf_program__set_expected_attach_type(struct bpf_program *prog,
>> enum bpf_attach_type type);
>>
>> +LIBBPF_API int
>> +bpf_program__set_attach_target(struct bpf_program *prog, int
>> attach_prog_fd,
>> + const char *attach_func_name);
>> +
>> LIBBPF_API bool bpf_program__is_socket_filter(const struct
>> bpf_program *prog);
>> LIBBPF_API bool bpf_program__is_tracepoint(const struct bpf_program
>> *prog);
>> LIBBPF_API bool bpf_program__is_raw_tracepoint(const struct
>> bpf_program *prog);
>> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
>> index b035122142bb..8aba5438a3f0 100644
>> --- a/tools/lib/bpf/libbpf.map
>> +++ b/tools/lib/bpf/libbpf.map
>> @@ -230,6 +230,7 @@ LIBBPF_0.0.7 {
>> bpf_program__name;
>> bpf_program__is_extension;
>> bpf_program__is_struct_ops;
>> + bpf_program__set_attach_target;
>
> This will have to go into LIBBPF_0.0.8 once bpf-next opens. Please
> rebase and re-send then.
Will do…
>> bpf_program__set_extension;
>> bpf_program__set_struct_ops;
>> btf__align_of;
>>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target
2020-02-14 7:34 ` Eelco Chaudron
@ 2020-02-14 17:53 ` Andrii Nakryiko
0 siblings, 0 replies; 8+ messages in thread
From: Andrii Nakryiko @ 2020-02-14 17:53 UTC (permalink / raw)
To: Eelco Chaudron
Cc: bpf, David S. Miller, Networking, Alexei Starovoitov,
Daniel Borkmann, Martin Lau, Song Liu, Yonghong Song,
Andrii Nakryiko, Toke Høiland-Jørgensen
On Thu, Feb 13, 2020 at 11:34 PM Eelco Chaudron <echaudro@redhat.com> wrote:
>
>
>
> On 13 Feb 2020, at 18:42, Andrii Nakryiko wrote:
>
> > On Thu, Feb 13, 2020 at 7:05 AM Eelco Chaudron <echaudro@redhat.com>
> > wrote:
> >>
> >> Currently when you want to attach a trace program to a bpf program
> >> the section name needs to match the tracepoint/function semantics.
> >>
> >> However the addition of the bpf_program__set_attach_target() API
> >> allows you to specify the tracepoint/function dynamically.
> >>
> >> The call flow would look something like this:
> >>
> >> xdp_fd = bpf_prog_get_fd_by_id(id);
> >> trace_obj = bpf_object__open_file("func.o", NULL);
> >> prog = bpf_object__find_program_by_title(trace_obj,
> >> "fentry/myfunc");
> >> bpf_program__set_expected_attach_type(prog, BPF_TRACE_FENTRY);
> >> bpf_program__set_attach_target(prog, xdp_fd,
> >> "xdpfilt_blk_all");
> >> bpf_object__load(trace_obj)
> >>
> >> Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
> >> ---
> >
> > API-wise this looks good, thanks! Please address feedback below and
> > re-submit once bpf-next opens. Can you please also convert one of
> > existing selftests using open_opts's attach_prog_fd to use this API
> > instead to have a demonstration there?
>
> Yes will update the one I added for bfp2bpf testing…
>
> >> v1 -> v2: Remove requirement for attach type name in API
> >>
> >> tools/lib/bpf/libbpf.c | 33 +++++++++++++++++++++++++++++++--
> >> tools/lib/bpf/libbpf.h | 4 ++++
> >> tools/lib/bpf/libbpf.map | 1 +
> >> 3 files changed, 36 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> >> index 514b1a524abb..9b8cab995580 100644
> >> --- a/tools/lib/bpf/libbpf.c
> >> +++ b/tools/lib/bpf/libbpf.c
> >> @@ -4939,8 +4939,8 @@ int bpf_program__load(struct bpf_program *prog,
> >> char *license, __u32 kern_ver)
> >> {
> >> int err = 0, fd, i, btf_id;
> >>
> >> - if (prog->type == BPF_PROG_TYPE_TRACING ||
> >> - prog->type == BPF_PROG_TYPE_EXT) {
> >> + if ((prog->type == BPF_PROG_TYPE_TRACING ||
> >> + prog->type == BPF_PROG_TYPE_EXT) &&
> >> !prog->attach_btf_id) {
> >> btf_id = libbpf_find_attach_btf_id(prog);
> >> if (btf_id <= 0)
> >> return btf_id;
> >> @@ -8132,6 +8132,35 @@ void bpf_program__bpil_offs_to_addr(struct
> >> bpf_prog_info_linear *info_linear)
> >> }
> >> }
> >>
> >> +int bpf_program__set_attach_target(struct bpf_program *prog,
> >> + int attach_prog_fd,
> >> + const char *attach_func_name)
> >> +{
> >> + int btf_id;
> >> +
> >> + if (!prog || attach_prog_fd < 0 || !attach_func_name)
> >> + return -EINVAL;
> >> +
> >> + if (attach_prog_fd)
> >> + btf_id = libbpf_find_prog_btf_id(attach_func_name,
> >> + attach_prog_fd);
> >> + else
> >> + btf_id =
> >> __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
> >> + attach_func_name,
> >> +
> >> prog->expected_attach_type);
> >> +
> >> + if (btf_id <= 0) {
> >> + if (!attach_prog_fd)
> >> + pr_warn("%s is not found in vmlinux BTF\n",
> >> + attach_func_name);
> >
> > libbpf_find_attach_btf_id's error reporting is misleading (it always
> > reports as if error happened with vmlinux BTF, even if attach_prog_fd
> > 0). Could you please fix that and add better error reporting here
> > for attach_prog_fd>0 case here?
> >
>
> I did not add log messages for the btf_id > 0 case as they are covered
> in the libbpf_find_prog_btf_id() function. Please let me know if this is
> not enough.
I see... libbpf_find_attach_btf_id is still wrong, so maybe let's move
this warning into __find_vmlinux_btf_id for more symmetrical (with
libbpf_find_prog_btf_id) error reporting?
>
> >> + return btf_id;
> >> + }
> >> +
> >> + prog->attach_btf_id = btf_id;
> >> + prog->attach_prog_fd = attach_prog_fd;
> >> + return 0;
> >> +}
> >> +
> >> int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz)
> >> {
> >> int err = 0, n, len, start, end = -1;
> >> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> >> index 3fe12c9d1f92..02fc58a21a7f 100644
> >> --- a/tools/lib/bpf/libbpf.h
> >> +++ b/tools/lib/bpf/libbpf.h
> >> @@ -334,6 +334,10 @@ LIBBPF_API void
> >> bpf_program__set_expected_attach_type(struct bpf_program *prog,
> >> enum bpf_attach_type type);
> >>
> >> +LIBBPF_API int
> >> +bpf_program__set_attach_target(struct bpf_program *prog, int
> >> attach_prog_fd,
> >> + const char *attach_func_name);
> >> +
> >> LIBBPF_API bool bpf_program__is_socket_filter(const struct
> >> bpf_program *prog);
> >> LIBBPF_API bool bpf_program__is_tracepoint(const struct bpf_program
> >> *prog);
> >> LIBBPF_API bool bpf_program__is_raw_tracepoint(const struct
> >> bpf_program *prog);
> >> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> >> index b035122142bb..8aba5438a3f0 100644
> >> --- a/tools/lib/bpf/libbpf.map
> >> +++ b/tools/lib/bpf/libbpf.map
> >> @@ -230,6 +230,7 @@ LIBBPF_0.0.7 {
> >> bpf_program__name;
> >> bpf_program__is_extension;
> >> bpf_program__is_struct_ops;
> >> + bpf_program__set_attach_target;
> >
> > This will have to go into LIBBPF_0.0.8 once bpf-next opens. Please
> > rebase and re-send then.
>
> Will do…
>
> >> bpf_program__set_extension;
> >> bpf_program__set_struct_ops;
> >> btf__align_of;
> >>
>
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2020-02-14 17:54 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-02-13 15:04 [PATCH bpf-next v2] libbpf: Add support for dynamic program attach target Eelco Chaudron
2020-02-13 15:32 ` Toke Høiland-Jørgensen
2020-02-13 17:00 ` Eelco Chaudron
2020-02-13 17:13 ` Toke Høiland-Jørgensen
2020-02-13 17:13 ` Toke Høiland-Jørgensen
2020-02-13 17:42 ` Andrii Nakryiko
2020-02-14 7:34 ` Eelco Chaudron
2020-02-14 17:53 ` Andrii Nakryiko
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