Re: [bpf-next 2/2] libbpf: Add pathname_concat() helper

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在 2022/9/10 1:16, sdf@xxxxxxxxxx 写道:
On 09/09, Wang Yufen wrote:
Move snprintf and len check to common helper pathname_concat() to make the
code simpler.

Signed-off-by: Wang Yufen <wangyufen@xxxxxxxxxx>
---
  tools/lib/bpf/libbpf.c | 74 ++++++++++++++++++--------------------------------
  1 file changed, 27 insertions(+), 47 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 5854b92..238a03e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2096,20 +2096,31 @@ static bool get_map_field_int(const char *map_name, const struct btf *btf,
      return true;
  }

-static int build_map_pin_path(struct bpf_map *map, const char *path)
+static int pathname_concat(const char *path, const char *name, char *buf)
  {
-    char buf[PATH_MAX];
      int len;

-    if (!path)
-        path = "/sys/fs/bpf";
-
-    len = snprintf(buf, PATH_MAX, "%s/%s", path, bpf_map__name(map));
+    len = snprintf(buf, PATH_MAX, "%s/%s", path, name);
      if (len < 0)
          return -EINVAL;
      else if (len >= PATH_MAX)
          return -ENAMETOOLONG;

+    return 0;
+}
+
+static int build_map_pin_path(struct bpf_map *map, const char *path)
+{
+    char buf[PATH_MAX];
+    int err;
+
+    if (!path)
+        path = "/sys/fs/bpf";
+
+    err = pathname_concat(path, bpf_map__name(map), buf);
+    if (err)
+        return err;
+
      return bpf_map__set_pin_path(map, buf);
  }

@@ -7959,17 +7970,8 @@ 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;

[..]

+            if (pathname_concat(path, bpf_map__name(map), buf))
                  goto err_unpin_maps;
-            }

You're breaking error reporting here and in a bunch of other places.
Should be:

err = pathname_concat();
if (err)
    goto err_unpin_maps;

Thanks for your comments.

Sure, my bad.

I have the same attitude towards this patch as the first one in the
series: not worth it. Nothing is currently broken, the code as is relatively readable, this version is not much simpler, it just looks slightly different
taste-wise..

How about this: if you really want to push this kind of cleanup, send
selftests that exercise all these error cases? :-)

Ok. I will try.  :-)



              sanitize_pin_path(buf);
              pin_path = buf;
          } else if (!map->pin_path) {
@@ -8007,14 +8009,9 @@ 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);
+            if (err)
+                return err;
              sanitize_pin_path(buf);
              pin_path = buf;
          } else if (!map->pin_path) {
@@ -8032,6 +8029,7 @@ 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)
@@ -8043,17 +8041,8 @@ 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;
+        if (pathname_concat(path, prog->name, buf))
              goto err_unpin_programs;
-        } else if (len >= PATH_MAX) {
-            err = -ENAMETOOLONG;
-            goto err_unpin_programs;
-        }

          err = bpf_program__pin(prog, buf);
          if (err)
@@ -8064,13 +8053,7 @@ 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))
              continue;

          bpf_program__unpin(prog, buf);
@@ -8089,13 +8072,10 @@ 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);
+        if (err)
+            return libbpf_err(err);

          err = bpf_program__unpin(prog, buf);
          if (err)
--
1.8.3.1




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