[PATCH net-next 0/2] libbpf: minor fix and API update

Hello,

Here's a small patchset on libbpf fixing two issues I've encountered
when adding some eBPF related features to Suricata.

Patchset statistics:
 tools/lib/bpf/libbpf.c | 16 +++++++---------
 tools/lib/bpf/libbpf.h |  4 +++-
 2 files changed, 10 insertions(+), 10 deletions(-)

BR,

The include of err.h is not explicitely needed in exported
functions and it was causing include conflict with some existing
code due to redefining some macros.

Signed-off-by: Eric Leblond <redacted>
---
 tools/lib/bpf/libbpf.c | 1 +
 tools/lib/bpf/libbpf.h | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b699aea..7872ff6 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -31,6 +31,7 @@
 #include <linux/kernel.h>
 #include <linux/bpf.h>
 #include <linux/list.h>
+#include <linux/err.h>
 #include <libelf.h>
 #include <gelf.h>
 

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index dd7a513..a6c5cde 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h

@@ -23,7 +23,6 @@
 
 #include <stdio.h>
 #include <stdbool.h>
-#include <linux/err.h>
 
 enum libbpf_errno {
 	__LIBBPF_ERRNO__START = 4000,

-- 
2.8.1

Current API was not allowing the user to set a type like socket
filter. To avoid a setter function for each type, the patch simply
exports a set function that takes the type in parameter.

Signed-off-by: Eric Leblond <redacted>
---
 tools/lib/bpf/libbpf.c | 15 ++++++---------
 tools/lib/bpf/libbpf.h |  3 +++
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7872ff6..ff2a8c6 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -1336,26 +1336,23 @@ int bpf_program__nth_fd(struct bpf_program *prog, int n)
 	return fd;
 }
 
-static void bpf_program__set_type(struct bpf_program *prog,
+int bpf_program__set_type(struct bpf_program *prog,
 				  enum bpf_prog_type type)
 {
+	if (!prog)
+		return -EINVAL;
 	prog->type = type;
+	return 0;
 }
 
 int bpf_program__set_tracepoint(struct bpf_program *prog)
 {
-	if (!prog)
-		return -EINVAL;
-	bpf_program__set_type(prog, BPF_PROG_TYPE_TRACEPOINT);
-	return 0;
+	return bpf_program__set_type(prog, BPF_PROG_TYPE_TRACEPOINT);
 }
 
 int bpf_program__set_kprobe(struct bpf_program *prog)
 {
-	if (!prog)
-		return -EINVAL;
-	bpf_program__set_type(prog, BPF_PROG_TYPE_KPROBE);
-	return 0;
+	return bpf_program__set_type(prog, BPF_PROG_TYPE_KPROBE);
 }
 
 static bool bpf_program__is_type(struct bpf_program *prog,

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index a6c5cde..6a84d7a 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h

@@ -173,6 +173,9 @@ int bpf_program__set_kprobe(struct bpf_program *prog);
 bool bpf_program__is_tracepoint(struct bpf_program *prog);
 bool bpf_program__is_kprobe(struct bpf_program *prog);
 
+int bpf_program__set_type(struct bpf_program *prog,
+				  enum bpf_prog_type type);
+
 /*
  * We don't need __attribute__((packed)) now since it is
  * unnecessary for 'bpf_map_def' because they are all aligned.

-- 
2.8.1

I think you should cc linux-kernel@vger.kernel.org for code in
tools/ .

Thank you.

On 2016/8/13 20:17, Eric Leblond wrote:

Hello,

Here's a small patchset on libbpf fixing two issues I've encountered
when adding some eBPF related features to Suricata.

Patchset statistics:
  tools/lib/bpf/libbpf.c | 16 +++++++---------
  tools/lib/bpf/libbpf.h |  4 +++-
  2 files changed, 10 insertions(+), 10 deletions(-)

BR,
--
Eric Leblond

On 2016/8/13 20:17, Eric Leblond wrote:

Functions declared in this header require PTR_ERR
to decode error number. Logically speaking, this
header depends linux/err.h, so this include is
required. If not, there must have another way for
caller to decode error numbers.

I know the problem you try to solve. Please have a look at thread

https://lkml.org/lkml/2015/12/17/20

At that time I think we should create a wrapper in libbpf.h like this:

#ifdef USE_LINUX_ERR
#include <linux/err.h>
#endif
...
int libbpf_ptr_err(void *ptr);
...

It is acceptable but ugly. Can you find a better method?

Thank you.

  enum libbpf_errno {
  	__LIBBPF_ERRNO__START = 4000,

On 2016/8/13 20:17, Eric Leblond wrote:

We'd better add a sanity check here to prevent setting invalid
program type. Plase have a look at

https://lkml.org/lkml/2015/12/17/13

This makes libbpf.h depend on kernel's uapi/linux/bpf.h.
Although I did this in the above patch, I don't like this
dependency. This is the reason why I introduce

int bpf_program__set_tracepoint(struct bpf_program *prog);
int bpf_program__set_kprobe(struct bpf_program *prog);

bool bpf_program__is_tracepoint(struct bpf_program *prog);
bool bpf_program__is_kprobe(struct bpf_program *prog);

and hide bpf_program__set_type inside the .c file.

Please add type setting functions, or pass int value to
bpf_program__set_type and add sanity checking.

Thank you.