* [PATCH bpf-next] libbpf: Allow kprobe attach using legacy debugfs interface
@ 2022-03-26 14:43 Hengqi Chen
2022-03-29 23:18 ` Andrii Nakryiko
0 siblings, 1 reply; 8+ messages in thread
From: Hengqi Chen @ 2022-03-26 14:43 UTC (permalink / raw)
To: bpf, andrii; +Cc: songliubraving, hengqi.chen
On some old kernels, kprobe auto-attach may fail when attach to symbols
like udp_send_skb.isra.52 . This is because the kernel has kprobe PMU
but don't allow attach to a symbol with '.' ([0]). Add a new option to
bpf_kprobe_opts to allow using the legacy kprobe attach directly.
This way, users can use bpf_program__attach_kprobe_opts in a dedicated
custom sec handler to handle such case.
[0]: https://github.com/torvalds/linux/blob/v4.18/kernel/trace/trace_kprobe.c#L340-L343
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---
tools/lib/bpf/libbpf.c | 9 ++++++++-
tools/lib/bpf/libbpf.h | 4 +++-
2 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 809fe209cdcc..9a294bb84bad 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10097,9 +10097,16 @@ static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
const char *kfunc_name, size_t offset)
{
static int index = 0;
+ int i;
snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
__sync_fetch_and_add(&index, 1));
+
+ /* sanitize .isra.$n symbols */
+ for (i = 0; buf[i]; i++) {
+ if (!isalnum(buf[i]))
+ buf[i] = '_';
+ }
}
static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,
@@ -10189,7 +10196,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog,
offset = OPTS_GET(opts, offset, 0);
pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0);
- legacy = determine_kprobe_perf_type() < 0;
+ legacy = OPTS_GET(opts, legacy, false) || determine_kprobe_perf_type() < 0;
if (!legacy) {
pfd = perf_event_open_probe(false /* uprobe */, retprobe,
func_name, offset,
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 05dde85e19a6..88a3624e3f15 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -413,9 +413,11 @@ struct bpf_kprobe_opts {
size_t offset;
/* kprobe is return probe */
bool retprobe;
+ /* use the legacy debugfs interface */
+ bool legacy;
size_t :0;
};
-#define bpf_kprobe_opts__last_field retprobe
+#define bpf_kprobe_opts__last_field legacy
LIBBPF_API struct bpf_link *
bpf_program__attach_kprobe(const struct bpf_program *prog, bool retprobe,
--
2.30.2
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH bpf-next] libbpf: Allow kprobe attach using legacy debugfs interface
2022-03-26 14:43 [PATCH bpf-next] libbpf: Allow kprobe attach using legacy debugfs interface Hengqi Chen
@ 2022-03-29 23:18 ` Andrii Nakryiko
2022-03-30 2:30 ` Hengqi Chen
0 siblings, 1 reply; 8+ messages in thread
From: Andrii Nakryiko @ 2022-03-29 23:18 UTC (permalink / raw)
To: Hengqi Chen; +Cc: bpf, Andrii Nakryiko, Song Liu
On Sat, Mar 26, 2022 at 7:43 AM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>
> On some old kernels, kprobe auto-attach may fail when attach to symbols
> like udp_send_skb.isra.52 . This is because the kernel has kprobe PMU
> but don't allow attach to a symbol with '.' ([0]). Add a new option to
> bpf_kprobe_opts to allow using the legacy kprobe attach directly.
> This way, users can use bpf_program__attach_kprobe_opts in a dedicated
> custom sec handler to handle such case.
>
> [0]: https://github.com/torvalds/linux/blob/v4.18/kernel/trace/trace_kprobe.c#L340-L343
>
> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> ---
It's sad, but it makes sense. But, let's have a selftests that
validates uses legacy option explicitly (e.g., in
prog_tests/attach_probe.c). Also, let's fix this limitation in the
kernel? It makes no sense to limit attaching to a proper kallsym
symbol.
> tools/lib/bpf/libbpf.c | 9 ++++++++-
> tools/lib/bpf/libbpf.h | 4 +++-
> 2 files changed, 11 insertions(+), 2 deletions(-)
>
[...]
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH bpf-next] libbpf: Allow kprobe attach using legacy debugfs interface
2022-03-29 23:18 ` Andrii Nakryiko
@ 2022-03-30 2:30 ` Hengqi Chen
2022-03-30 2:50 ` Andrii Nakryiko
0 siblings, 1 reply; 8+ messages in thread
From: Hengqi Chen @ 2022-03-30 2:30 UTC (permalink / raw)
To: Andrii Nakryiko; +Cc: bpf, Andrii Nakryiko, Song Liu
Hello, Andrii
On 2022/3/30 7:18 AM, Andrii Nakryiko wrote:
> On Sat, Mar 26, 2022 at 7:43 AM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>>
>> On some old kernels, kprobe auto-attach may fail when attach to symbols
>> like udp_send_skb.isra.52 . This is because the kernel has kprobe PMU
>> but don't allow attach to a symbol with '.' ([0]). Add a new option to
>> bpf_kprobe_opts to allow using the legacy kprobe attach directly.
>> This way, users can use bpf_program__attach_kprobe_opts in a dedicated
>> custom sec handler to handle such case.
>>
>> [0]: https://github.com/torvalds/linux/blob/v4.18/kernel/trace/trace_kprobe.c#L340-L343
>>
>> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
>> ---
>
> It's sad, but it makes sense. But, let's have a selftests that
> validates uses legacy option explicitly (e.g., in
> prog_tests/attach_probe.c). Also, let's fix this limitation in the
OK, will add a selftest to exercise the new option.
> kernel? It makes no sense to limit attaching to a proper kallsym
> symbol.
This limitation is lifted in newer kernel. Kernel v5.4 don't have this issue.
>
>> tools/lib/bpf/libbpf.c | 9 ++++++++-
>> tools/lib/bpf/libbpf.h | 4 +++-
>> 2 files changed, 11 insertions(+), 2 deletions(-)
>>
>
> [...]
--
Hengqi
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH bpf-next] libbpf: Allow kprobe attach using legacy debugfs interface
2022-03-30 2:30 ` Hengqi Chen
@ 2022-03-30 2:50 ` Andrii Nakryiko
2022-03-30 3:03 ` Hengqi Chen
0 siblings, 1 reply; 8+ messages in thread
From: Andrii Nakryiko @ 2022-03-30 2:50 UTC (permalink / raw)
To: Hengqi Chen; +Cc: bpf, Andrii Nakryiko, Song Liu
On Tue, Mar 29, 2022 at 7:30 PM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>
> Hello, Andrii
>
> On 2022/3/30 7:18 AM, Andrii Nakryiko wrote:
> > On Sat, Mar 26, 2022 at 7:43 AM Hengqi Chen <hengqi.chen@gmail.com> wrote:
> >>
> >> On some old kernels, kprobe auto-attach may fail when attach to symbols
> >> like udp_send_skb.isra.52 . This is because the kernel has kprobe PMU
> >> but don't allow attach to a symbol with '.' ([0]). Add a new option to
> >> bpf_kprobe_opts to allow using the legacy kprobe attach directly.
> >> This way, users can use bpf_program__attach_kprobe_opts in a dedicated
> >> custom sec handler to handle such case.
> >>
> >> [0]: https://github.com/torvalds/linux/blob/v4.18/kernel/trace/trace_kprobe.c#L340-L343
> >>
> >> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> >> ---
> >
> > It's sad, but it makes sense. But, let's have a selftests that
> > validates uses legacy option explicitly (e.g., in
> > prog_tests/attach_probe.c). Also, let's fix this limitation in the
>
> OK, will add a selftest to exercise the new option.
>
> > kernel? It makes no sense to limit attaching to a proper kallsym
> > symbol.
>
> This limitation is lifted in newer kernel. Kernel v5.4 don't have this issue.
Oh, ok. So how about another plan of attack then: if kprobe target
function has '.' *and* we are on the kernel that doesn't support that,
switch to legacy kprobe automatically? No need for a new option,
libbpf handles this transparently.
Still need a test for kprobe with '.' in it, though not sure how
reliable that will be... We can use kallsyms cache to check if
expected xxx.isra.0 (or whatever) is present, and if not - skip
subtest?
>
> >
> >> tools/lib/bpf/libbpf.c | 9 ++++++++-
> >> tools/lib/bpf/libbpf.h | 4 +++-
> >> 2 files changed, 11 insertions(+), 2 deletions(-)
> >>
> >
> > [...]
>
> --
> Hengqi
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH bpf-next] libbpf: Allow kprobe attach using legacy debugfs interface
2022-03-30 2:50 ` Andrii Nakryiko
@ 2022-03-30 3:03 ` Hengqi Chen
2022-03-31 9:27 ` Alan Maguire
2022-03-31 17:29 ` Andrii Nakryiko
0 siblings, 2 replies; 8+ messages in thread
From: Hengqi Chen @ 2022-03-30 3:03 UTC (permalink / raw)
To: Andrii Nakryiko; +Cc: bpf, Andrii Nakryiko, Song Liu
On 2022/3/30 10:50 AM, Andrii Nakryiko wrote:
> On Tue, Mar 29, 2022 at 7:30 PM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>>
>> Hello, Andrii
>>
>> On 2022/3/30 7:18 AM, Andrii Nakryiko wrote:
>>> On Sat, Mar 26, 2022 at 7:43 AM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>>>>
>>>> On some old kernels, kprobe auto-attach may fail when attach to symbols
>>>> like udp_send_skb.isra.52 . This is because the kernel has kprobe PMU
>>>> but don't allow attach to a symbol with '.' ([0]). Add a new option to
>>>> bpf_kprobe_opts to allow using the legacy kprobe attach directly.
>>>> This way, users can use bpf_program__attach_kprobe_opts in a dedicated
>>>> custom sec handler to handle such case.
>>>>
>>>> [0]: https://github.com/torvalds/linux/blob/v4.18/kernel/trace/trace_kprobe.c#L340-L343
>>>>
>>>> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
>>>> ---
>>>
>>> It's sad, but it makes sense. But, let's have a selftests that
>>> validates uses legacy option explicitly (e.g., in
>>> prog_tests/attach_probe.c). Also, let's fix this limitation in the
>>
>> OK, will add a selftest to exercise the new option.
>>
>>> kernel? It makes no sense to limit attaching to a proper kallsym
>>> symbol.
>>
>> This limitation is lifted in newer kernel. Kernel v5.4 don't have this issue.
>
> Oh, ok. So how about another plan of attack then: if kprobe target
> function has '.' *and* we are on the kernel that doesn't support that,
> switch to legacy kprobe automatically? No need for a new option,
> libbpf handles this transparently.
>
That's better, and also eliminate the need for custom SEC() handler.
> Still need a test for kprobe with '.' in it, though not sure how
> reliable that will be... We can use kallsyms cache to check if
> expected xxx.isra.0 (or whatever) is present, and if not - skip
> subtest?
>
Not sure how to do that. Even if such symbol exists, how to reliably
trigger it is another problem.
>>
>>>
>>>> tools/lib/bpf/libbpf.c | 9 ++++++++-
>>>> tools/lib/bpf/libbpf.h | 4 +++-
>>>> 2 files changed, 11 insertions(+), 2 deletions(-)
>>>>
>>>
>>> [...]
>>
>> --
>> Hengqi
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH bpf-next] libbpf: Allow kprobe attach using legacy debugfs interface
2022-03-30 3:03 ` Hengqi Chen
@ 2022-03-31 9:27 ` Alan Maguire
2022-03-31 13:34 ` Hengqi Chen
2022-03-31 17:29 ` Andrii Nakryiko
1 sibling, 1 reply; 8+ messages in thread
From: Alan Maguire @ 2022-03-31 9:27 UTC (permalink / raw)
To: Hengqi Chen; +Cc: Andrii Nakryiko, bpf, Andrii Nakryiko, Song Liu
On Wed, 30 Mar 2022, Hengqi Chen wrote:
>
>
> On 2022/3/30 10:50 AM, Andrii Nakryiko wrote:
> > On Tue, Mar 29, 2022 at 7:30 PM Hengqi Chen <hengqi.chen@gmail.com> wrote:
> >>
> >> Hello, Andrii
> >>
> >> On 2022/3/30 7:18 AM, Andrii Nakryiko wrote:
> >>> On Sat, Mar 26, 2022 at 7:43 AM Hengqi Chen <hengqi.chen@gmail.com> wrote:
> >>>>
> >>>> On some old kernels, kprobe auto-attach may fail when attach to symbols
> >>>> like udp_send_skb.isra.52 . This is because the kernel has kprobe PMU
> >>>> but don't allow attach to a symbol with '.' ([0]). Add a new option to
> >>>> bpf_kprobe_opts to allow using the legacy kprobe attach directly.
> >>>> This way, users can use bpf_program__attach_kprobe_opts in a dedicated
> >>>> custom sec handler to handle such case.
> >>>>
> >>>> [0]: https://github.com/torvalds/linux/blob/v4.18/kernel/trace/trace_kprobe.c#L340-L343
> >>>>
> >>>> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> >>>> ---
> >>>
> >>> It's sad, but it makes sense. But, let's have a selftests that
> >>> validates uses legacy option explicitly (e.g., in
> >>> prog_tests/attach_probe.c). Also, let's fix this limitation in the
> >>
> >> OK, will add a selftest to exercise the new option.
> >>
> >>> kernel? It makes no sense to limit attaching to a proper kallsym
> >>> symbol.
> >>
> >> This limitation is lifted in newer kernel. Kernel v5.4 don't have this issue.
> >
> > Oh, ok. So how about another plan of attack then: if kprobe target
> > function has '.' *and* we are on the kernel that doesn't support that,
> > switch to legacy kprobe automatically? No need for a new option,
> > libbpf handles this transparently.
> >
>
> That's better, and also eliminate the need for custom SEC() handler.
>
> > Still need a test for kprobe with '.' in it, though not sure how
> > reliable that will be... We can use kallsyms cache to check if
> > expected xxx.isra.0 (or whatever) is present, and if not - skip
> > subtest?
> >
>
> Not sure how to do that. Even if such symbol exists, how to reliably
> trigger it is another problem.
>
could we add a function to bpf testmod that is easily triggered
and likely to be .isra-ed maybe?
Experimenting, the following function becomes .isra-ed at when
compiled with -fipa-sra:
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
b/tools/testing/selftests/bpf/bpf
index e585e1c..bb51e21 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -88,6 +88,17 @@ __weak noinline struct file *bpf_testmod_return_ptr(int
arg)
}
}
+struct testisra {
+ int val1;
+ int val2;
+ int val3;
+};
+
+static noinline void bpf_testmod_test_isra(struct testisra *t, int val1,
int val2)
+{
+ t->val3 = val1 + val2;
+}
+
noinline ssize_t
bpf_testmod_test_read(struct file *file, struct kobject *kobj,
struct bin_attribute *bin_attr,
@@ -98,8 +109,14 @@ __weak noinline struct file
*bpf_testmod_return_ptr(int arg)
.off = off,
.len = len,
};
+ struct testisra t = {
+ .val1 = off,
+ .val2 = len
+ };
int i = 1;
+ bpf_testmod_test_isra(&t, t.val1, t.val2);
+
while (bpf_testmod_return_ptr(i))
i++;
Tested on gcc 9; possibly different results on different versions..
Alan
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH bpf-next] libbpf: Allow kprobe attach using legacy debugfs interface
2022-03-31 9:27 ` Alan Maguire
@ 2022-03-31 13:34 ` Hengqi Chen
0 siblings, 0 replies; 8+ messages in thread
From: Hengqi Chen @ 2022-03-31 13:34 UTC (permalink / raw)
To: Alan Maguire; +Cc: Andrii Nakryiko, bpf, Andrii Nakryiko, Song Liu
Hello, Alan
On 2022/3/31 5:27 PM, Alan Maguire wrote:
> On Wed, 30 Mar 2022, Hengqi Chen wrote:
>
>>
>>
>> On 2022/3/30 10:50 AM, Andrii Nakryiko wrote:
>>> On Tue, Mar 29, 2022 at 7:30 PM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>>>>
>>>> Hello, Andrii
>>>>
>>>> On 2022/3/30 7:18 AM, Andrii Nakryiko wrote:
>>>>> On Sat, Mar 26, 2022 at 7:43 AM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>>>>>>
>>>>>> On some old kernels, kprobe auto-attach may fail when attach to symbols
>>>>>> like udp_send_skb.isra.52 . This is because the kernel has kprobe PMU
>>>>>> but don't allow attach to a symbol with '.' ([0]). Add a new option to
>>>>>> bpf_kprobe_opts to allow using the legacy kprobe attach directly.
>>>>>> This way, users can use bpf_program__attach_kprobe_opts in a dedicated
>>>>>> custom sec handler to handle such case.
>>>>>>
>>>>>> [0]: https://github.com/torvalds/linux/blob/v4.18/kernel/trace/trace_kprobe.c#L340-L343
>>>>>>
>>>>>> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
>>>>>> ---
>>>>>
>>>>> It's sad, but it makes sense. But, let's have a selftests that
>>>>> validates uses legacy option explicitly (e.g., in
>>>>> prog_tests/attach_probe.c). Also, let's fix this limitation in the
>>>>
>>>> OK, will add a selftest to exercise the new option.
>>>>
>>>>> kernel? It makes no sense to limit attaching to a proper kallsym
>>>>> symbol.
>>>>
>>>> This limitation is lifted in newer kernel. Kernel v5.4 don't have this issue.
>>>
>>> Oh, ok. So how about another plan of attack then: if kprobe target
>>> function has '.' *and* we are on the kernel that doesn't support that,
>>> switch to legacy kprobe automatically? No need for a new option,
>>> libbpf handles this transparently.
>>>
>>
>> That's better, and also eliminate the need for custom SEC() handler.
>>
>>> Still need a test for kprobe with '.' in it, though not sure how
>>> reliable that will be... We can use kallsyms cache to check if
>>> expected xxx.isra.0 (or whatever) is present, and if not - skip
>>> subtest?
>>>
>>
>> Not sure how to do that. Even if such symbol exists, how to reliably
>> trigger it is another problem.
>>
>
> could we add a function to bpf testmod that is easily triggered
> and likely to be .isra-ed maybe?
>
> Experimenting, the following function becomes .isra-ed at when
> compiled with -fipa-sra:
>
> diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> b/tools/testing/selftests/bpf/bpf
> index e585e1c..bb51e21 100644
> --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
> @@ -88,6 +88,17 @@ __weak noinline struct file *bpf_testmod_return_ptr(int
> arg)
> }
> }
>
> +struct testisra {
> + int val1;
> + int val2;
> + int val3;
> +};
> +
> +static noinline void bpf_testmod_test_isra(struct testisra *t, int val1,
> int val2)
> +{
> + t->val3 = val1 + val2;
> +}
> +
> noinline ssize_t
> bpf_testmod_test_read(struct file *file, struct kobject *kobj,
> struct bin_attribute *bin_attr,
> @@ -98,8 +109,14 @@ __weak noinline struct file
> *bpf_testmod_return_ptr(int arg)
> .off = off,
> .len = len,
> };
> + struct testisra t = {
> + .val1 = off,
> + .val2 = len
> + };
> int i = 1;
>
> + bpf_testmod_test_isra(&t, t.val1, t.val2);
> +
> while (bpf_testmod_return_ptr(i))
> i++;
>
>
> Tested on gcc 9; possibly different results on different versions..
>
> Alan
Thanks for the pointer, will give it a try.
Hengqi
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH bpf-next] libbpf: Allow kprobe attach using legacy debugfs interface
2022-03-30 3:03 ` Hengqi Chen
2022-03-31 9:27 ` Alan Maguire
@ 2022-03-31 17:29 ` Andrii Nakryiko
1 sibling, 0 replies; 8+ messages in thread
From: Andrii Nakryiko @ 2022-03-31 17:29 UTC (permalink / raw)
To: Hengqi Chen; +Cc: bpf, Andrii Nakryiko, Song Liu
On Tue, Mar 29, 2022 at 8:03 PM Hengqi Chen <hengqi.chen@gmail.com> wrote:
>
>
>
> On 2022/3/30 10:50 AM, Andrii Nakryiko wrote:
> > On Tue, Mar 29, 2022 at 7:30 PM Hengqi Chen <hengqi.chen@gmail.com> wrote:
> >>
> >> Hello, Andrii
> >>
> >> On 2022/3/30 7:18 AM, Andrii Nakryiko wrote:
> >>> On Sat, Mar 26, 2022 at 7:43 AM Hengqi Chen <hengqi.chen@gmail.com> wrote:
> >>>>
> >>>> On some old kernels, kprobe auto-attach may fail when attach to symbols
> >>>> like udp_send_skb.isra.52 . This is because the kernel has kprobe PMU
> >>>> but don't allow attach to a symbol with '.' ([0]). Add a new option to
> >>>> bpf_kprobe_opts to allow using the legacy kprobe attach directly.
> >>>> This way, users can use bpf_program__attach_kprobe_opts in a dedicated
> >>>> custom sec handler to handle such case.
> >>>>
> >>>> [0]: https://github.com/torvalds/linux/blob/v4.18/kernel/trace/trace_kprobe.c#L340-L343
> >>>>
> >>>> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> >>>> ---
> >>>
> >>> It's sad, but it makes sense. But, let's have a selftests that
> >>> validates uses legacy option explicitly (e.g., in
> >>> prog_tests/attach_probe.c). Also, let's fix this limitation in the
> >>
> >> OK, will add a selftest to exercise the new option.
> >>
> >>> kernel? It makes no sense to limit attaching to a proper kallsym
> >>> symbol.
> >>
> >> This limitation is lifted in newer kernel. Kernel v5.4 don't have this issue.
> >
> > Oh, ok. So how about another plan of attack then: if kprobe target
> > function has '.' *and* we are on the kernel that doesn't support that,
> > switch to legacy kprobe automatically? No need for a new option,
> > libbpf handles this transparently.
> >
>
> That's better, and also eliminate the need for custom SEC() handler.
>
> > Still need a test for kprobe with '.' in it, though not sure how
> > reliable that will be... We can use kallsyms cache to check if
> > expected xxx.isra.0 (or whatever) is present, and if not - skip
> > subtest?
> >
>
> Not sure how to do that. Even if such symbol exists, how to reliably
> trigger it is another problem.
In addition to what Alan proposed, which relies on compiler to do this
whole isra thingy. I wonder if we can just create an alias symbol with
dots in its name? I haven't tried, but would be curious to see if that
works in bpf_testmod.
>
> >>
> >>>
> >>>> tools/lib/bpf/libbpf.c | 9 ++++++++-
> >>>> tools/lib/bpf/libbpf.h | 4 +++-
> >>>> 2 files changed, 11 insertions(+), 2 deletions(-)
> >>>>
> >>>
> >>> [...]
> >>
> >> --
> >> Hengqi
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-03-31 17:30 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-03-26 14:43 [PATCH bpf-next] libbpf: Allow kprobe attach using legacy debugfs interface Hengqi Chen
2022-03-29 23:18 ` Andrii Nakryiko
2022-03-30 2:30 ` Hengqi Chen
2022-03-30 2:50 ` Andrii Nakryiko
2022-03-30 3:03 ` Hengqi Chen
2022-03-31 9:27 ` Alan Maguire
2022-03-31 13:34 ` Hengqi Chen
2022-03-31 17:29 ` Andrii Nakryiko
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).