On 12/01/2022 10:01, Quentin Monnet wrote:
2022-01-11 18:44 UTC+0000 ~ Usama Arif <usama.arif@xxxxxxxxxxxxx>
Currently bpf_helper_defs.h and the bpf helpers man page are auto-generated
using function documentation present in bpf.h. If the documentation for the
helper is missing or doesn't follow a specific format for e.g. if a function
is documented as:
* long bpf_kallsyms_lookup_name( const char *name, int name_sz, int flags, u64 *res )
instead of
* long bpf_kallsyms_lookup_name(const char *name, int name_sz, int flags, u64 *res)
(notice the extra space at the start and end of function arguments)
then that helper is not dumped in the auto-generated header and results in
an invalid call during eBPF runtime, even if all the code specific to the
helper is correct.
This patch checks the number of functions documented within the header file
with those present as part of #define __BPF_FUNC_MAPPER and generates an
error in the header file and the man page if they don't match. It is not
needed with the currently documented upstream functions, but can help in
debugging when developing new helpers when there might be missing or
misformatted documentation.
Signed-off-by: Usama Arif <usama.arif@xxxxxxxxxxxxx>
---
v4->v5:
- Converted warning to error incase of missing/misformatted helper doc
(suggested by Song Liu)
I don't think it was converted to an error in the sense that Song meant
it? Unless I'm missing something you simply changed the message so that
it prints "error" instead of "warning", but the script still goes on
without returning any error code, and a failure won't be detected by the
CI for example.
Could you make the script break out on errors, and print a message to
stderr so that it's visible even if the generated output is redirected
to a file, please?
It does now print an error to stdout while building an eBPF application.
For e.g. if you introduce a space in the doc as in the commit message like:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index ba5af15e25f5..5bf80dbb820b 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4908,7 +4908,7 @@ union bpf_attr {
*
* **-ENOENT** if architecture does not support branch
records.
*
- * long bpf_trace_vprintk(const char *fmt, u32 fmt_size, const void
*data, u32 data_len)
+ * long bpf_trace_vprintk( const char *fmt, u32 fmt_size, const void
*data, u32 data_len)
* Description
* Behaves like **bpf_trace_printk**\ () helper, but takes
an array of u64
* to format and can handle more format args as a result.
@@ -4938,6 +4938,12 @@ union bpf_attr {
* **-ENOENT** if symbol is not found.
*
* **-EPERM** if caller does not have permission to obtain
kernel address.
and build samples/bpf:
make LLVM_STRIP=llvm-strip-13 M=samples/bpf > /tmp/samplesbuild.out
you get the following at stderr returning an error code
make[2]: *** [Makefile:186:
/data/usaari01/ebpf/linux/samples/bpf/bpftool/pid_iter.bpf.o] Error 1
make[2]: *** Waiting for unfinished jobs....
In file included from skeleton/profiler.bpf.c:4:
In file included from
/data/usaari01/ebpf/linux/samples/bpf/bpftool//bootstrap/libbpf//include/bpf/bpf_helpers.h:11:
/data/usaari01/ebpf/linux/samples/bpf/bpftool//bootstrap/libbpf//include/bpf/bpf_helper_defs.h:5:2:
error: The number of unique helpers in description (176) don't match the
number of unique helpers defined in __BPF_FUNC_MAPPER (180)
#error The number of unique helpers in description (176) don't match the
number of unique helpers defined in __BPF_FUNC_MAPPER (180)
^
/data/usaari01/ebpf/linux/samples/bpf/bpftool//bootstrap/libbpf//include/bpf/bpf_helper_defs.h:7:2:
error: The description for FN(trace_vprintk) is not present or formatted
correctly.
#error The description for FN(trace_vprintk) is not present or formatted
correctly.
^
But i am guessing that you want an error while the script is run as well?
If we do this:
diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
index adf08fa963a4..4ce982ce58f2 100755
--- a/scripts/bpf_doc.py
+++ b/scripts/bpf_doc.py
@@ -397,6 +397,7 @@ HELPERS
The description for %s is not present or formatted correctly.
''' % (self.define_unique_helpers[nr_desc_unique_helpers])
print(header_error)
+ print(header_error, file = sys.stderr)
print(header_description)
@@ -693,6 +694,7 @@ class PrinterHelpers(Printer):
#error The description for %s is not present or formatted correctly.
''' % (self.define_unique_helpers[nr_desc_unique_helpers])
print(header_error)
+ print(header_error, file = sys.stderr)
for fwd in self.type_fwds:
print('%s;' % fwd)
then an error will be printed while the script is run and also later
while the eBPF application is compiled. I can send this in next version
if thats the preference?
v3->v4:
- Added comments to make code clearer
- Added warning to man page as well (suggested by Quentin Monnet)
v2->v3:
- Removed check if value is already in set (suggested by Song Liu)
v1->v2:
- Fix CI error reported by Alexei Starovoitov
---
scripts/bpf_doc.py | 74 +++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 70 insertions(+), 4 deletions(-)
diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
index a6403ddf5de7..adf08fa963a4 100755
--- a/scripts/bpf_doc.py
+++ b/scripts/bpf_doc.py
@@ -87,6 +87,8 @@ class HeaderParser(object):
self.line = ''
self.helpers = []
self.commands = []
+ self.desc_unique_helpers = set()
+ self.define_unique_helpers = []
def parse_element(self):
proto = self.parse_symbol()
@@ -193,19 +195,42 @@ class HeaderParser(object):
except NoSyscallCommandFound:
break
- def parse_helpers(self):
+ def parse_desc_helpers(self):
self.seek_to('* Start of BPF helper function descriptions:',
'Could not find start of eBPF helper descriptions list')
while True:
try:
helper = self.parse_helper()
self.helpers.append(helper)
+ proto = helper.proto_break_down()
+ self.desc_unique_helpers.add(proto['name'])
except NoHelperFound:
break
+ def parse_define_helpers(self):
+ # Parse the number of FN(...) in #define __BPF_FUNC_MAPPER to compare
+ # later with the number of unique function names present in description.
+ # Note: seek_to(..) discards the first line below the target search text,
+ # resulting in FN(unspec) being skipped and not added to self.define_unique_helpers.
+ self.seek_to('#define __BPF_FUNC_MAPPER(FN)',
+ 'Could not find start of eBPF helper definition list')
+ # Searches for either one or more FN(\w+) defines or a backslash for newline
+ p = re.compile('\s*(FN\(\w+\))+|\\\\')
+ fn_defines_str = ''
+ while True:
+ capture = p.match(self.line)
+ if capture:
+ fn_defines_str += self.line
+ else:
+ break
+ self.line = self.reader.readline()
+ # Find the number of occurences of FN(\w+)
+ self.define_unique_helpers = re.findall('FN\(\w+\)', fn_defines_str)
+
def run(self):
self.parse_syscall()
- self.parse_helpers()
+ self.parse_desc_helpers()
+ self.parse_define_helpers()
self.reader.close()
###############################################################################
@@ -305,9 +330,11 @@ class PrinterHelpersRST(PrinterRST):
"""
def __init__(self, parser):
self.elements = parser.helpers
+ self.desc_unique_helpers = parser.desc_unique_helpers
+ self.define_unique_helpers = parser.define_unique_helpers
def print_header(self):
- header = '''\
+ header_name = '''\
===========
BPF-HELPERS
===========
@@ -317,6 +344,8 @@ list of eBPF helper functions
:Manual section: 7
+'''
+ header_description = '''
DESCRIPTION
===========
@@ -349,7 +378,27 @@ HELPERS
=======
'''
PrinterRST.print_license(self)
- print(header)
+
+ print(header_name)
+
+ # Add an error if the correct number of helpers are not auto-generated.
+ nr_desc_unique_helpers = len(self.desc_unique_helpers)
+ nr_define_unique_helpers = len(self.define_unique_helpers)
+ if nr_desc_unique_helpers != nr_define_unique_helpers:
+ header_error = '''
+.. error::
+ The number of unique helpers in description (%d) don\'t match the number of unique helpers defined in __BPF_FUNC_MAPPER (%d)
don\'t -> doesn\'t
+''' % (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.
+ header_error += '''
+.. error::
+ The description for %s is not present or formatted correctly.
+''' % (self.define_unique_helpers[nr_desc_unique_helpers])
+ print(header_error)
+
+ print(header_description)
def print_footer(self):
footer = '''
@@ -509,6 +558,8 @@ class PrinterHelpers(Printer):
"""
def __init__(self, parser):
self.elements = parser.helpers
+ self.desc_unique_helpers = parser.desc_unique_helpers
+ self.define_unique_helpers = parser.define_unique_helpers
type_fwds = [
'struct bpf_fib_lookup',
@@ -628,6 +679,21 @@ class PrinterHelpers(Printer):
/* Forward declarations of BPF structs */'''
print(header)
+
+ nr_desc_unique_helpers = len(self.desc_unique_helpers)
+ nr_define_unique_helpers = len(self.define_unique_helpers)
+ if nr_desc_unique_helpers != nr_define_unique_helpers:
+ header_error = '''
+#error The number of unique helpers in description (%d) don\'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.
+ header_error += '''
+#error The description for %s is not present or formatted correctly.
+''' % (self.define_unique_helpers[nr_desc_unique_helpers])
+ print(header_error)
+
for fwd in self.type_fwds:
print('%s;' % fwd)
print('')
