This avoids
ld: kernel/trace/bpf_trace.o: in function `bpf_sock_from_file':
bpf_trace.c:(.text+0xe23): undefined reference to `sock_from_file'
When compiling a kernel with BPF and without NET.
Reported-by: Randy Dunlap <[email protected]>
Signed-off-by: Florent Revest <[email protected]>
---
kernel/trace/bpf_trace.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 0cf0a6331482..29ec2b3b1cc4 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1272,7 +1272,11 @@ const struct bpf_func_proto bpf_snprintf_btf_proto = {
BPF_CALL_1(bpf_sock_from_file, struct file *, file)
{
+#ifdef CONFIG_NET
return (unsigned long) sock_from_file(file);
+#else
+ return 0;
+#endif
}
BTF_ID_LIST(bpf_sock_from_file_btf_ids)
--
2.29.2.576.ga3fc446d84-goog
On 12/7/20 12:06 PM, Florent Revest wrote:
> This avoids
> ld: kernel/trace/bpf_trace.o: in function `bpf_sock_from_file':
> bpf_trace.c:(.text+0xe23): undefined reference to `sock_from_file'
> When compiling a kernel with BPF and without NET.
>
> Reported-by: Randy Dunlap <[email protected]>
> Signed-off-by: Florent Revest <[email protected]>
Acked-by: Randy Dunlap <[email protected]> # build-tested
Thanks.
> ---
> kernel/trace/bpf_trace.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 0cf0a6331482..29ec2b3b1cc4 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1272,7 +1272,11 @@ const struct bpf_func_proto bpf_snprintf_btf_proto = {
>
> BPF_CALL_1(bpf_sock_from_file, struct file *, file)
> {
> +#ifdef CONFIG_NET
> return (unsigned long) sock_from_file(file);
> +#else
> + return 0;
> +#endif
> }
>
> BTF_ID_LIST(bpf_sock_from_file_btf_ids)
>
--
~Randy
On Mon, Dec 07, 2020 at 09:06:05PM +0100, Florent Revest wrote:
> This avoids
> ld: kernel/trace/bpf_trace.o: in function `bpf_sock_from_file':
> bpf_trace.c:(.text+0xe23): undefined reference to `sock_from_file'
> When compiling a kernel with BPF and without NET.
>
> Reported-by: Randy Dunlap <[email protected]>
> Signed-off-by: Florent Revest <[email protected]>
> ---
> kernel/trace/bpf_trace.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 0cf0a6331482..29ec2b3b1cc4 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1272,7 +1272,11 @@ const struct bpf_func_proto bpf_snprintf_btf_proto = {
>
> BPF_CALL_1(bpf_sock_from_file, struct file *, file)
> {
> +#ifdef CONFIG_NET
> return (unsigned long) sock_from_file(file);
> +#else
> + return 0;
> +#endif
> }
Should bpf_sock_from_file_proto belong to
tracing_prog_func_proto() instead of bpf_tracing_func_proto()?
bpf_skc_to_*_proto is also in tracing_prog_func_proto()
where there is an existing "#ifdef CONFIG_NET".
>
> BTF_ID_LIST(bpf_sock_from_file_btf_ids)
> --
> 2.29.2.576.ga3fc446d84-goog
>
On Mon, 2020-12-07 at 13:33 -0800, Martin KaFai Lau wrote:
> On Mon, Dec 07, 2020 at 09:06:05PM +0100, Florent Revest wrote:
> > This avoids
> > ld: kernel/trace/bpf_trace.o: in function `bpf_sock_from_file':
> > bpf_trace.c:(.text+0xe23): undefined reference to
> > `sock_from_file'
> > When compiling a kernel with BPF and without NET.
> >
> > Reported-by: Randy Dunlap <[email protected]>
> > Signed-off-by: Florent Revest <[email protected]>
> > ---
> > kernel/trace/bpf_trace.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index 0cf0a6331482..29ec2b3b1cc4 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -1272,7 +1272,11 @@ const struct bpf_func_proto
> > bpf_snprintf_btf_proto = {
> >
> > BPF_CALL_1(bpf_sock_from_file, struct file *, file)
> > {
> > +#ifdef CONFIG_NET
> > return (unsigned long) sock_from_file(file);
> > +#else
> > + return 0;
> > +#endif
> > }
> Should bpf_sock_from_file_proto belong to
> tracing_prog_func_proto() instead of bpf_tracing_func_proto()?
> bpf_skc_to_*_proto is also in tracing_prog_func_proto()
> where there is an existing "#ifdef CONFIG_NET".
I'm happy to move bpf_sock_from_file to tracing_prog_func_proto if
you'd prefer that. I'm actually unsure what the difference would be,
those function names are confusing, but this works for our use-case. :)
However, by itself, that wouldn't address the problem reported by Randy
since the helper definition would still be compiled and have an
undefined reference to sock_from_file. The existing socket helpers (for
example skc_to_tcp_sock) can get away without a patch like mine because
they are defined in net/core/filter.c which only gets compiled with
CONFIG_NET.
I will send a v3 where I move the sock_from_file helper definition to
net/core/filter.c and also move the usage of the helper to
tracing_prog_func_proto under CONFIG_NET and then you can feel free to
merge v2 or v3 depending on which approach you prefer (or a followup
version if I mess up again... :D)