bpf/scripts: Raise an exception if the correct number of sycalls are not generated

Currently the syscalls rst and subsequently man page are auto-generated
using function documentation present in bpf.h. If the documentation for the
syscall is missing or doesn't follow a specific format, then that syscall
is not dumped in the auto-generated rst.

This patch checks the number of syscalls documented within the header file
with those present as part of the enum bpf_cmd and raises an Exception if
they don't match. It is not needed with the currently documented upstream
syscalls, but can help in debugging when developing new syscalls when
there might be missing or misformatted documentation.

The function helper_number_check is moved to the Printer parent
class and renamed to elem_number_check as all the most derived children
classes are using this function now.
Signed-off-by: Usama Arif <usama.arif@bytedance.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20220119114442.1452088-3-usama.arif@bytedance.com

scripts/bpf_doc.py

@@ -89,6 +89,8 @@ class HeaderParser(object):
         self.commands = []
         self.desc_unique_helpers = set()
         self.define_unique_helpers = []
+        self.desc_syscalls = []
+        self.enum_syscalls = []
 
     def parse_element(self):
         proto    = self.parse_symbol()
@@ -103,7 +105,7 @@ class HeaderParser(object):
         return Helper(proto=proto, desc=desc, ret=ret)
 
     def parse_symbol(self):
-        p = re.compile(' \* ?(.+)$')
+        p = re.compile(' \* ?(BPF\w+)$')
         capture = p.match(self.line)
         if not capture:
             raise NoSyscallCommandFound
@@ -181,26 +183,55 @@ class HeaderParser(object):
             raise Exception("No return found for " + proto)
         return ret
 
-    def seek_to(self, target, help_message):
+    def seek_to(self, target, help_message, discard_lines = 1):
         self.reader.seek(0)
         offset = self.reader.read().find(target)
         if offset == -1:
             raise Exception(help_message)
         self.reader.seek(offset)
         self.reader.readline()
-        self.reader.readline()
+        for _ in range(discard_lines):
+            self.reader.readline()
         self.line = self.reader.readline()
 
-    def parse_syscall(self):
+    def parse_desc_syscall(self):
         self.seek_to('* DOC: eBPF Syscall Commands',
                      'Could not find start of eBPF syscall descriptions list')
         while True:
             try:
                 command = self.parse_element()
                 self.commands.append(command)
+                self.desc_syscalls.append(command.proto)
+
             except NoSyscallCommandFound:
                 break
 
+    def parse_enum_syscall(self):
+        self.seek_to('enum bpf_cmd {',
+                     'Could not find start of bpf_cmd enum', 0)
+        # Searches for either one or more BPF\w+ enums
+        bpf_p = re.compile('\s*(BPF\w+)+')
+        # Searches for an enum entry assigned to another entry,
+        # for e.g. BPF_PROG_RUN = BPF_PROG_TEST_RUN, which is
+        # not documented hence should be skipped in check to
+        # determine if the right number of syscalls are documented
+        assign_p = re.compile('\s*(BPF\w+)\s*=\s*(BPF\w+)')
+        bpf_cmd_str = ''
+        while True:
+            capture = assign_p.match(self.line)
+            if capture:
+                # Skip line if an enum entry is assigned to another entry
+                self.line = self.reader.readline()
+                continue
+            capture = bpf_p.match(self.line)
+            if capture:
+                bpf_cmd_str += self.line
+            else:
+                break
+            self.line = self.reader.readline()
+        # Find the number of occurences of BPF\w+
+        self.enum_syscalls = re.findall('(BPF\w+)+', bpf_cmd_str)
+
     def parse_desc_helpers(self):
         self.seek_to('* Start of BPF helper function descriptions:',
                      'Could not find start of eBPF helper descriptions list')
@@ -234,7 +265,8 @@ class HeaderParser(object):
         self.define_unique_helpers = re.findall('FN\(\w+\)', fn_defines_str)
 
     def run(self):
-        self.parse_syscall()
+        self.parse_desc_syscall()
+        self.parse_enum_syscall()
         self.parse_desc_helpers()
         self.parse_define_helpers()
         self.reader.close()
@@ -266,6 +298,25 @@ class Printer(object):
             self.print_one(elem)
         self.print_footer()
 
+    def elem_number_check(self, desc_unique_elem, define_unique_elem, type, instance):
+        """
+        Checks the number of helpers/syscalls documented within the header file
+        description with those defined as part of enum/macro and raise an
+        Exception if they don't match.
+        """
+        nr_desc_unique_elem = len(desc_unique_elem)
+        nr_define_unique_elem = len(define_unique_elem)
+        if nr_desc_unique_elem != nr_define_unique_elem:
+            exception_msg = '''
+The number of unique %s in description (%d) doesn\'t match the number of unique %s defined in %s (%d)
+''' % (type, nr_desc_unique_elem, type, instance, nr_define_unique_elem)
+            if nr_desc_unique_elem < nr_define_unique_elem:
+                # Function description is parsed until no helper is found (which can be due to
+                # misformatting). Hence, only print the first missing/misformatted helper/enum.
+                exception_msg += '''
+The description for %s is not present or formatted correctly.
+''' % (define_unique_elem[nr_desc_unique_elem])
+            raise Exception(exception_msg)
 
 class PrinterRST(Printer):
     """
@@ -326,26 +377,6 @@ class PrinterRST(Printer):
 
         print('')
 
-def helper_number_check(desc_unique_helpers, define_unique_helpers):
-    """
-    Checks the number of functions documented within the header file
-    with those present as part of #define __BPF_FUNC_MAPPER and raise an
-    Exception if they don't match.
-    """
-    nr_desc_unique_helpers = len(desc_unique_helpers)
-    nr_define_unique_helpers = len(define_unique_helpers)
-    if nr_desc_unique_helpers != nr_define_unique_helpers:
-        helper_exception = '''
-The number of unique helpers in description (%d) doesn\'t match the number of unique helpers defined in __BPF_FUNC_MAPPER (%d)
-''' % (nr_desc_unique_helpers, nr_define_unique_helpers)
-        if nr_desc_unique_helpers < nr_define_unique_helpers:
-            # Function description is parsed until no helper is found (which can be due to
-            # misformatting). Hence, only print the first missing/misformatted function.
-            helper_exception += '''
-The description for %s is not present or formatted correctly.
-''' % (define_unique_helpers[nr_desc_unique_helpers])
-        raise Exception(helper_exception)
-
 class PrinterHelpersRST(PrinterRST):
     """
     A printer for dumping collected information about helpers as a ReStructured
@@ -355,7 +386,7 @@ class PrinterHelpersRST(PrinterRST):
     """
     def __init__(self, parser):
         self.elements = parser.helpers
-        helper_number_check(parser.desc_unique_helpers, parser.define_unique_helpers)
+        self.elem_number_check(parser.desc_unique_helpers, parser.define_unique_helpers, 'helper', '__BPF_FUNC_MAPPER')
 
     def print_header(self):
         header = '''\
@@ -529,6 +560,7 @@ class PrinterSyscallRST(PrinterRST):
     """
     def __init__(self, parser):
         self.elements = parser.commands
+        self.elem_number_check(parser.desc_syscalls, parser.enum_syscalls, 'syscall', 'bpf_cmd')
 
     def print_header(self):
         header = '''\
@@ -560,7 +592,7 @@ class PrinterHelpers(Printer):
     """
     def __init__(self, parser):
         self.elements = parser.helpers
-        helper_number_check(parser.desc_unique_helpers, parser.define_unique_helpers)
+        self.elem_number_check(parser.desc_unique_helpers, parser.define_unique_helpers, 'helper', '__BPF_FUNC_MAPPER')
 
     type_fwds = [
             'struct bpf_fib_lookup',