[PATCH v4] bpf/scripts: Generate GCC compatible helper defs header
From: James Hilliard
Date: Fri Aug 05 2022 - 04:18:43 EST
The current bpf_helper_defs.h helpers are llvm specific and don't work
correctly with gcc.
GCC requires kernel helper funcs to have the following attribute set:
__attribute__((kernel_helper(NUM)))
Generate gcc compatible headers based on the format in bpf-helpers.h.
This leaves the bpf_helper_defs.h entirely unchanged and generates a
fully separate GCC compatible bpf_helper_defs_attr.h header file
which is conditionally included if the GCC kernel_helper attribute
is supported.
This adds GCC attribute style kernel helpers in bpf_helper_defs_attr.h:
void *bpf_map_lookup_elem(void *map, const void *key) __attribute__((kernel_helper(1)));
long bpf_map_update_elem(void *map, const void *key, const void *value, __u64 flags) __attribute__((kernel_helper(2)));
See:
https://github.com/gcc-mirror/gcc/blob/releases/gcc-12.1.0/gcc/config/bpf/bpf-helpers.h#L24-L27
This fixes the following build error:
error: indirect call in function, which are not supported by eBPF
Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx>
---
Changes v3 -> v4:
- don't modify bpf_helper_defs.h
- generate bpf_helper_defs_attr.h for GCC
- check __has_attribute(kernel_helper) for selecting GCC defs
Changes v2 -> v3:
- use a conditional helper macro
Changes v1 -> v2:
- more details in commit log
---
scripts/bpf_doc.py | 58 ++++++++++++++++++++++---------------
tools/lib/bpf/Makefile | 7 ++++-
tools/lib/bpf/bpf_helpers.h | 4 +++
3 files changed, 45 insertions(+), 24 deletions(-)
diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
index dfb260de17a8..c4e8fa3619d8 100755
--- a/scripts/bpf_doc.py
+++ b/scripts/bpf_doc.py
@@ -570,9 +570,10 @@ class PrinterHelpers(Printer):
be included from BPF program.
@parser: A HeaderParser with Helper objects to print to standard output
"""
- def __init__(self, parser):
+ def __init__(self, parser, attr_header):
self.elements = parser.helpers
self.elem_number_check(parser.desc_unique_helpers, parser.define_unique_helpers, 'helper', '__BPF_FUNC_MAPPER')
+ self.attr_header = attr_header
type_fwds = [
'struct bpf_fib_lookup',
@@ -719,6 +720,24 @@ class PrinterHelpers(Printer):
seen_helpers = set()
+ def print_args(self, proto):
+ comma = ''
+ for i, a in enumerate(proto['args']):
+ t = a['type']
+ n = a['name']
+ if proto['name'] in self.overloaded_helpers and i == 0:
+ t = 'void'
+ n = 'ctx'
+ one_arg = '{}{}'.format(comma, self.map_type(t))
+ if n:
+ if a['star']:
+ one_arg += ' {}'.format(a['star'])
+ else:
+ one_arg += ' '
+ one_arg += '{}'.format(n)
+ comma = ', '
+ print(one_arg, end='')
+
def print_one(self, helper):
proto = helper.proto_break_down()
@@ -742,26 +761,16 @@ class PrinterHelpers(Printer):
print(' *{}{}'.format(' \t' if line else '', line))
print(' */')
- print('static %s %s(*%s)(' % (self.map_type(proto['ret_type']),
- proto['ret_star'], proto['name']), end='')
- comma = ''
- for i, a in enumerate(proto['args']):
- t = a['type']
- n = a['name']
- if proto['name'] in self.overloaded_helpers and i == 0:
- t = 'void'
- n = 'ctx'
- one_arg = '{}{}'.format(comma, self.map_type(t))
- if n:
- if a['star']:
- one_arg += ' {}'.format(a['star'])
- else:
- one_arg += ' '
- one_arg += '{}'.format(n)
- comma = ', '
- print(one_arg, end='')
-
- print(') = (void *) %d;' % len(self.seen_helpers))
+ if self.attr_header:
+ print('%s %s%s(' % (self.map_type(proto['ret_type']),
+ proto['ret_star'], proto['name']), end='')
+ self.print_args(proto)
+ print(') __attribute__((kernel_helper(%d)));' % len(self.seen_helpers))
+ else:
+ print('static %s %s(*%s)(' % (self.map_type(proto['ret_type']),
+ proto['ret_star'], proto['name']), end='')
+ self.print_args(proto)
+ print(') = (void *) %d;' % len(self.seen_helpers))
print('')
###############################################################################
@@ -785,6 +794,8 @@ rst2man utility.
""")
argParser.add_argument('--header', action='store_true',
help='generate C header file')
+argParser.add_argument('--attr-header', action='store_true',
+ help='generate GCC attr style C header file')
if (os.path.isfile(bpfh)):
argParser.add_argument('--filename', help='path to include/uapi/linux/bpf.h',
default=bpfh)
@@ -799,10 +810,11 @@ headerParser = HeaderParser(args.filename)
headerParser.run()
# Print formatted output to standard output.
-if args.header:
+if args.header or args.attr_header:
if args.target != 'helpers':
raise NotImplementedError('Only helpers header generation is supported')
- printer = PrinterHelpers(headerParser)
+ attr_header = True if args.attr_header else False
+ printer = PrinterHelpers(headerParser, attr_header)
else:
printer = printers[args.target](headerParser)
printer.print_all()
diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index 4c904ef0b47e..cf9efe764030 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -116,7 +116,8 @@ STATIC_OBJDIR := $(OUTPUT)staticobjs/
BPF_IN_SHARED := $(SHARED_OBJDIR)libbpf-in.o
BPF_IN_STATIC := $(STATIC_OBJDIR)libbpf-in.o
BPF_HELPER_DEFS := $(OUTPUT)bpf_helper_defs.h
-BPF_GENERATED := $(BPF_HELPER_DEFS)
+BPF_HELPER_DEFS_ATTR := $(OUTPUT)bpf_helper_defs_attr.h
+BPF_GENERATED := $(BPF_HELPER_DEFS) $(BPF_HELPER_DEFS_ATTR)
LIB_TARGET := $(addprefix $(OUTPUT),$(LIB_TARGET))
LIB_FILE := $(addprefix $(OUTPUT),$(LIB_FILE))
@@ -160,6 +161,10 @@ $(BPF_HELPER_DEFS): $(srctree)/tools/include/uapi/linux/bpf.h
$(QUIET_GEN)$(srctree)/scripts/bpf_doc.py --header \
--file $(srctree)/tools/include/uapi/linux/bpf.h > $(BPF_HELPER_DEFS)
+$(BPF_HELPER_DEFS_ATTR): $(srctree)/tools/include/uapi/linux/bpf.h
+ $(QUIET_GEN)$(srctree)/scripts/bpf_doc.py --attr-header \
+ --file $(srctree)/tools/include/uapi/linux/bpf.h > $(BPF_HELPER_DEFS_ATTR)
+
$(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION)
$(OUTPUT)libbpf.so.$(LIBBPF_VERSION): $(BPF_IN_SHARED) $(VERSION_SCRIPT)
diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index 7349b16b8e2f..b7573e7d3feb 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -8,7 +8,11 @@
* in advance since bpf_helper_defs.h uses such types
* as __u64.
*/
+#if __has_attribute(kernel_helper)
+#include "bpf_helper_defs_attr.h"
+#else
#include "bpf_helper_defs.h"
+#endif
#define __uint(name, val) int (*name)[val]
#define __type(name, val) typeof(val) *name
--
2.34.1