scripts/bpf_doc.py: update logic to not assume sequential enum values

Relax bpf_doc.py's expectation of all BPF_FUNC_xxx enumerators having
sequential values increasing by one. Instead, only make sure that
relative order of BPF helper descriptions in comments matches
enumerators definitions order.

Also additionally make sure that helper IDs are not duplicated.

And also make sure that for cases when we have multiple descriptions for
the same BPF helper (e.g., for bpf_get_socket_cookie()), all such
descriptions are grouped together.

Such checks should capture all the same (and more) issues in upstream
UAPI headers, but also handle backported kernels correctly.

Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/r/20221006042452.2089843-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

scripts/bpf_doc.py

@@ -97,6 +97,7 @@ class HeaderParser(object):
         self.desc_unique_helpers = set()
         self.define_unique_helpers = []
         self.helper_enum_vals = {}
+        self.helper_enum_pos = {}
         self.desc_syscalls = []
         self.enum_syscalls = []
 
@@ -264,42 +265,60 @@ class HeaderParser(object):
         # Searches for one FN(\w+) define or a backslash for newline
         p = re.compile('\s*FN\((\w+), (\d+), ##ctx\)|\\\\')
         fn_defines_str = ''
+        i = 0
         while True:
             capture = p.match(self.line)
             if capture:
                 fn_defines_str += self.line
-                self.helper_enum_vals[capture.expand(r'bpf_\1')] = int(capture[2])
+                helper_name = capture.expand(r'bpf_\1')
+                self.helper_enum_vals[helper_name] = int(capture[2])
+                self.helper_enum_pos[helper_name] = i
+                i += 1
             else:
                 break
             self.line = self.reader.readline()
         # Find the number of occurences of FN(\w+)
         self.define_unique_helpers = re.findall('FN\(\w+, \d+, ##ctx\)', fn_defines_str)
 
-    def assign_helper_values(self):
+    def validate_helpers(self):
+        last_helper = ''
         seen_helpers = set()
+        seen_enum_vals = set()
+        i = 0
         for helper in self.helpers:
             proto = helper.proto_break_down()
             name = proto['name']
             try:
                 enum_val = self.helper_enum_vals[name]
+                enum_pos = self.helper_enum_pos[name]
             except KeyError:
                 raise Exception("Helper %s is missing from enum bpf_func_id" % name)
 
+            if name in seen_helpers:
+                if last_helper != name:
+                    raise Exception("Helper %s has multiple descriptions which are not grouped together" % name)
+                continue
+
             # Enforce current practice of having the descriptions ordered
             # by enum value.
+            if enum_pos != i:
+                raise Exception("Helper %s (ID %d) comment order (#%d) must be aligned with its position (#%d) in enum bpf_func_id" % (name, enum_val, i + 1, enum_pos + 1))
+            if enum_val in seen_enum_vals:
+                raise Exception("Helper %s has duplicated value %d" % (name, enum_val))
+
             seen_helpers.add(name)
-            desc_val = len(seen_helpers)
-            if desc_val != enum_val:
-                raise Exception("Helper %s comment order (#%d) must be aligned with its position (#%d) in enum bpf_func_id" % (name, desc_val, enum_val))
+            last_helper = name
+            seen_enum_vals.add(enum_val)
 
             helper.enum_val = enum_val
+            i += 1
 
     def run(self):
         self.parse_desc_syscall()
         self.parse_enum_syscall()
         self.parse_desc_helpers()
         self.parse_define_helpers()
-        self.assign_helper_values()
+        self.validate_helpers()
         self.reader.close()
 
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