[bpf-next v4] libbpf: Add pathname_concat() helper

[bpf-next v4] libbpf: Add pathname_concat() helper

[Wang Yufen]

Move snprintf and len check to common helper pathname_concat() to make the
code simpler.

Signed-off-by: Wang Yufen <wangyufen@huawei.com>
---
 tools/lib/bpf/libbpf.c | 76 +++++++++++++++++++-------------------------------
 1 file changed, 29 insertions(+), 47 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2ca30cc..2d8b195 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2096,19 +2096,30 @@ static bool get_map_field_int(const char *map_name, const struct btf *btf,
 	return true;
 }
 
+static int pathname_concat(const char *path, const char *name, char *buf, size_t buflen)
+{
+	int len;
+
+	len = snprintf(buf, buflen, "%s/%s", path, name);
+	if (len < 0)
+		return libbpf_err(-EINVAL);
+	if (len >= buflen)
+		return libbpf_err(-ENAMETOOLONG);
+
+	return 0;
+}
+
 static int build_map_pin_path(struct bpf_map *map, const char *path)
 {
 	char buf[PATH_MAX];
-	int len;
+	int err;
 
 	if (!path)
 		path = "/sys/fs/bpf";
 
-	len = snprintf(buf, PATH_MAX, "%s/%s", path, bpf_map__name(map));
-	if (len < 0)
-		return -EINVAL;
-	else if (len >= PATH_MAX)
-		return -ENAMETOOLONG;
+	err = pathname_concat(path, bpf_map__name(map), buf, sizeof(buf));
+	if (err)
+		return libbpf_err(err);
 
 	return bpf_map__set_pin_path(map, buf);
 }
@@ -7961,17 +7972,9 @@ int bpf_object__pin_maps(struct bpf_object *obj, const char *path)
 			continue;
 
 		if (path) {
-			int len;
-
-			len = snprintf(buf, PATH_MAX, "%s/%s", path,
-				       bpf_map__name(map));
-			if (len < 0) {
-				err = -EINVAL;
-				goto err_unpin_maps;
-			} else if (len >= PATH_MAX) {
-				err = -ENAMETOOLONG;
+			err = pathname_concat(path, bpf_map__name(map), buf, sizeof(buf));
+			if (err)
 				goto err_unpin_maps;
-			}
 			sanitize_pin_path(buf);
 			pin_path = buf;
 		} else if (!map->pin_path) {
@@ -8009,14 +8012,9 @@ int bpf_object__unpin_maps(struct bpf_object *obj, const char *path)
 		char buf[PATH_MAX];
 
 		if (path) {
-			int len;
-
-			len = snprintf(buf, PATH_MAX, "%s/%s", path,
-				       bpf_map__name(map));
-			if (len < 0)
-				return libbpf_err(-EINVAL);
-			else if (len >= PATH_MAX)
-				return libbpf_err(-ENAMETOOLONG);
+			err = pathname_concat(path, bpf_map__name(map), buf, sizeof(buf));
+			if (err)
+				return libbpf_err(err);
 			sanitize_pin_path(buf);
 			pin_path = buf;
 		} else if (!map->pin_path) {
@@ -8034,6 +8032,7 @@ int bpf_object__unpin_maps(struct bpf_object *obj, const char *path)
 int bpf_object__pin_programs(struct bpf_object *obj, const char *path)
 {
 	struct bpf_program *prog;
+	char buf[PATH_MAX];
 	int err;
 
 	if (!obj)
@@ -8045,17 +8044,9 @@ int bpf_object__pin_programs(struct bpf_object *obj, const char *path)
 	}
 
 	bpf_object__for_each_program(prog, obj) {
-		char buf[PATH_MAX];
-		int len;
-
-		len = snprintf(buf, PATH_MAX, "%s/%s", path, prog->name);
-		if (len < 0) {
-			err = -EINVAL;
-			goto err_unpin_programs;
-		} else if (len >= PATH_MAX) {
-			err = -ENAMETOOLONG;
+		err = pathname_concat(path, prog->name, buf, sizeof(buf));
+		if (err)
 			goto err_unpin_programs;
-		}
 
 		err = bpf_program__pin(prog, buf);
 		if (err)
@@ -8066,13 +8057,7 @@ int bpf_object__pin_programs(struct bpf_object *obj, const char *path)
 
 err_unpin_programs:
 	while ((prog = bpf_object__prev_program(obj, prog))) {
-		char buf[PATH_MAX];
-		int len;
-
-		len = snprintf(buf, PATH_MAX, "%s/%s", path, prog->name);
-		if (len < 0)
-			continue;
-		else if (len >= PATH_MAX)
+		if (pathname_concat(path, prog->name, buf, sizeof(buf)))
 			continue;
 
 		bpf_program__unpin(prog, buf);
@@ -8091,13 +8076,10 @@ int bpf_object__unpin_programs(struct bpf_object *obj, const char *path)
 
 	bpf_object__for_each_program(prog, obj) {
 		char buf[PATH_MAX];
-		int len;
 
-		len = snprintf(buf, PATH_MAX, "%s/%s", path, prog->name);
-		if (len < 0)
-			return libbpf_err(-EINVAL);
-		else if (len >= PATH_MAX)
-			return libbpf_err(-ENAMETOOLONG);
+		err = pathname_concat(path, prog->name, buf, sizeof(buf));
+		if (err)
+			return libbpf_err(err);
 
 		err = bpf_program__unpin(prog, buf);
 		if (err)
-- 
1.8.3.1

Re: [bpf-next v4] libbpf: Add pathname_concat() helper

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Thu, 22 Sep 2022 14:28:44 +0800 you wrote:
> Move snprintf and len check to common helper pathname_concat() to make the
> code simpler.
> 
> Signed-off-by: Wang Yufen <wangyufen@huawei.com>
> ---
>  tools/lib/bpf/libbpf.c | 76 +++++++++++++++++++-------------------------------
>  1 file changed, 29 insertions(+), 47 deletions(-)

Here is the summary with links:
  - [bpf-next,v4] libbpf: Add pathname_concat() helper
    https://git.kernel.org/bpf/bpf-next/c/e588c116df6c

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [bpf-next v4] libbpf: Add pathname_concat() helper

[Andrii Nakryiko]

On Wed, Sep 21, 2022 at 11:08 PM Wang Yufen <wangyufen@huawei.com> wrote:
>
> Move snprintf and len check to common helper pathname_concat() to make the
> code simpler.
>
> Signed-off-by: Wang Yufen <wangyufen@huawei.com>
> ---
>  tools/lib/bpf/libbpf.c | 76 +++++++++++++++++++-------------------------------
>  1 file changed, 29 insertions(+), 47 deletions(-)
>

You went a bit overboard with libbpf_err(). We need it only in
directly user-facing functions. I've fixed it up while applying. Also
moved buf and buffer size to be first two arguments to match
snprintf() order of arguments a bit closer. Applied to bpf-next,
thanks.

> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 2ca30cc..2d8b195 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -2096,19 +2096,30 @@ static bool get_map_field_int(const char *map_name, const struct btf *btf,
>         return true;
>  }

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