2020-12-07 20:01:33

by Florent Revest

Subject: [PATCH bpf-next] bpf: Only call sock_from_file with CONFIG_NET

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..877123bae71f 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 NULL;
+#endif
}

BTF_ID_LIST(bpf_sock_from_file_btf_ids)
--
2.29.2.576.ga3fc446d84-goog

2020-12-07 20:08:31

by Florent Revest

Subject: Re: [PATCH bpf-next] bpf: Only call sock_from_file with CONFIG_NET

On Mon, 2020-12-07 at 20:55 +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..877123bae71f 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 NULL;

Ugh, and of course I messed up my fix... :) Now this causes a:

./include/linux/stddef.h:8:14: warning: returning ‘void *’ from a
function with return type ‘u64’ {aka ‘long long unsigned int’} makes
integer from pointer without a cast [-Wint-conversion]
8 | #define NULL ((void *)0)
| ^
kernel/trace/bpf_trace.c:1278:9: note: in expansion of macro ‘NULL’
1278 | return NULL;

So I'm sending a v2!