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bpf: refactor skeleton generation

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This should hopefully fix cross compilation for the bpf programs.
This commit is contained in:
James Hilliard 2021-08-11 21:59:19 -06:00 committed by Zbigniew Jędrzejewski-Szmek
parent d4f8cd4d83
commit d40ce01814
12 changed files with 155 additions and 157 deletions
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5
meson.build
View File

@ -1008,11 +1008,9 @@ else
# We check for 'bpftool' first, honouring $PATH, and in /usr/sbin/ for Debian.
bpftool = find_program('bpftool', '/usr/sbin/bpftool', required : bpf_framework_required)
bpf_arches = ['x86_64']
deps_found = libbpf.found() and clang.found() and llvm_strip.found() and bpftool.found()
# Can build BPF program from source code in restricted C
conf.set10('BPF_FRAMEWORK',
bpf_arches.contains(host_machine.cpu_family()) and deps_found)
conf.set10('BPF_FRAMEWORK', deps_found)
endif
libmount = dependency('mount',
@ -1685,7 +1683,6 @@ subdir('src/boot/efi')
############################################################
build_bpf_skel_py = find_program('tools/build-bpf-skel.py')
generate_gperfs = find_program('tools/generate-gperfs.py')
make_autosuspend_rules_py = find_program('tools/make-autosuspend-rules.py')
make_directive_index_py = find_program('tools/make-directive-index.py')

2
src/core/bpf-socket-bind.c
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@ -11,7 +11,7 @@
/* libbpf, clang, llvm and bpftool compile time dependencies are satisfied */
#include "bpf-dlopen.h"
#include "bpf-link.h"
#include "bpf/socket_bind/socket-bind.skel.h"
#include "bpf/socket_bind/socket-bind-skel.h"
#include "bpf/socket_bind/socket-bind-api.bpf.h"
static struct socket_bind_bpf *socket_bind_bpf_free(struct socket_bind_bpf *obj) {

61
src/core/bpf/meson.build Normal file
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@ -0,0 +1,61 @@
# SPDX-License-Identifier: LGPL-2.1+
if conf.get('BPF_FRAMEWORK') == 1
clang_flags = [
'-Wno-compare-distinct-pointer-types',
'-O2',
'-target',
'bpf',
'-g',
'-c',
]
clang_arch_flag = '-D__@0@__'.format(host_machine.cpu_family())
if meson.version().version_compare('>= 0.58')
libbpf_include_dir = libbpf.get_variable('includedir')
else
libbpf_include_dir = libbpf.get_variable(pkgconfig : 'includedir')
endif
bpf_o_unstripped_cmd = [
clang,
clang_flags,
clang_arch_flag,
'-I.'
]
if not meson.is_cross_build()
target_triplet_cmd = run_command('gcc', '-dumpmachine', check: false)
if target_triplet_cmd.returncode() == 0
target_triplet = target_triplet_cmd.stdout().strip()
bpf_o_unstripped_cmd += [
'-isystem',
'/usr/include/@0@'.format(target_triplet)
]
endif
endif
bpf_o_unstripped_cmd += [
'-idirafter',
libbpf_include_dir,
'@INPUT@',
'-o',
'@OUTPUT@'
]
bpf_o_cmd = [
llvm_strip,
'-g',
'@INPUT@',
'-o',
'@OUTPUT@'
]
skel_h_cmd = [
bpftool,
'g',
's',
'@INPUT@'
]
endif

26
src/core/bpf/restrict_fs/meson.build
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@ -1,14 +1,22 @@
# SPDX-License-Identifier: LGPL-2.1-or-later
if conf.get('BPF_FRAMEWORK') == 1
restrict_fs_skel_h = custom_target(
'restrict-fs-skel.h',
restrict_fs_bpf_o_unstripped = custom_target(
'restrict-fs.bpf.unstripped.o',
input : 'restrict-fs.bpf.c',
output : 'restrict-fs-skel.h',
command : [build_bpf_skel_py,
'--clang_exec', clang.path(),
'--llvm_strip_exec', llvm_strip.path(),
'--bpftool_exec', bpftool.path(),
'--arch', host_machine.cpu_family(),
'@INPUT@', '@OUTPUT@'])
output : 'restrict-fs.bpf.unstripped.o',
command : bpf_o_unstripped_cmd)
restrict_fs_bpf_o = custom_target(
'restrict-fs.bpf.o',
input : restrict_fs_bpf_o_unstripped,
output : 'restrict-fs.bpf.o',
command : bpf_o_cmd)
restrict_fs_skel_h = custom_target(
'restrict-fs.skel.h',
input : restrict_fs_bpf_o,
output : 'restrict-fs.skel.h',
command : skel_h_cmd,
capture : true)
endif

14
src/core/bpf/restrict_fs/restrict-fs-skel.h Normal file
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@ -0,0 +1,14 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/* The SPDX header above is actually correct in claiming this was
* LGPL-2.1-or-later, because it is. Since the kernel doesn't consider that
* compatible with GPL we will claim this to be GPL however, which should be
* fine given that LGPL-2.1-or-later downgrades to GPL if needed.
*/
/* libbpf is used via dlopen(), so rename symbols */
#define bpf_object__open_skeleton sym_bpf_object__open_skeleton
#define bpf_object__load_skeleton sym_bpf_object__load_skeleton
#define bpf_object__destroy_skeleton sym_bpf_object__destroy_skeleton
#include "bpf/restrict_fs/restrict-fs.skel.h"

22
src/core/bpf/restrict_ifaces/meson.build
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@ -1,14 +1,22 @@
# SPDX-License-Identifier: LGPL-2.1-or-later
if conf.get('BPF_FRAMEWORK') == 1
restrict_ifaces_bpf_o_unstripped = custom_target(
'restrict-ifaces.bpf.unstripped.o',
input : 'restrict-ifaces.bpf.c',
output : 'restrict-ifaces.bpf.unstripped.o',
command : bpf_o_unstripped_cmd)
restrict_ifaces_bpf_o = custom_target(
'restrict-ifaces.bpf.o',
input : restrict_ifaces_bpf_o_unstripped,
output : 'restrict-ifaces.bpf.o',
command : bpf_o_cmd)
restrict_ifaces_skel_h = custom_target(
'restrict-ifaces.skel.h',
input : 'restrict-ifaces.bpf.c',
input : restrict_ifaces_bpf_o,
output : 'restrict-ifaces.skel.h',
command : [build_bpf_skel_py,
'--clang_exec', clang.path(),
'--llvm_strip_exec', llvm_strip.path(),
'--bpftool_exec', bpftool.path(),
'--arch', host_machine.cpu_family(),
'@INPUT@', '@OUTPUT@'])
command : skel_h_cmd,
capture : true)
endif

14
src/core/bpf/restrict_ifaces/restrict-ifaces-skel.h Normal file
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@ -0,0 +1,14 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/* The SPDX header above is actually correct in claiming this was
* LGPL-2.1-or-later, because it is. Since the kernel doesn't consider that
* compatible with GPL we will claim this to be GPL however, which should be
* fine given that LGPL-2.1-or-later downgrades to GPL if needed.
*/
/* libbpf is used via dlopen(), so rename symbols */
#define bpf_object__open_skeleton sym_bpf_object__open_skeleton
#define bpf_object__load_skeleton sym_bpf_object__load_skeleton
#define bpf_object__destroy_skeleton sym_bpf_object__destroy_skeleton
#include "bpf/restrict_ifaces/restrict-ifaces.skel.h"

22
src/core/bpf/socket_bind/meson.build
View File

@ -1,14 +1,22 @@
# SPDX-License-Identifier: LGPL-2.1-or-later
if conf.get('BPF_FRAMEWORK') == 1
socket_bind_bpf_o_unstripped = custom_target(
'socket-bind.bpf.unstripped.o',
input : 'socket-bind.bpf.c',
output : 'socket-bind.bpf.unstripped.o',
command : bpf_o_unstripped_cmd)
socket_bind_bpf_o = custom_target(
'socket-bind.bpf.o',
input : socket_bind_bpf_o_unstripped,
output : 'socket-bind.bpf.o',
command : bpf_o_cmd)
socket_bind_skel_h = custom_target(
'socket-bind.skel.h',
input : 'socket-bind.bpf.c',
input : socket_bind_bpf_o,
output : 'socket-bind.skel.h',
command : [build_bpf_skel_py,
'--clang_exec', clang.path(),
'--llvm_strip_exec', llvm_strip.path(),
'--bpftool_exec', bpftool.path(),
'--arch', host_machine.cpu_family(),
'@INPUT@', '@OUTPUT@'])
command : skel_h_cmd,
capture : true)
endif

14
src/core/bpf/socket_bind/socket-bind-skel.h Normal file
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@ -0,0 +1,14 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/* The SPDX header above is actually correct in claiming this was
* LGPL-2.1-or-later, because it is. Since the kernel doesn't consider that
* compatible with GPL we will claim this to be GPL however, which should be
* fine given that LGPL-2.1-or-later downgrades to GPL if needed.
*/
/* libbpf is used via dlopen(), so rename symbols */
#define bpf_object__open_skeleton sym_bpf_object__open_skeleton
#define bpf_object__load_skeleton sym_bpf_object__load_skeleton
#define bpf_object__destroy_skeleton sym_bpf_object__destroy_skeleton
#include "bpf/socket_bind/socket-bind.skel.h"

2
src/core/meson.build
View File

@ -133,6 +133,8 @@ libcore_sources = '''
unit.h
'''.split()
subdir('bpf')
subdir('bpf/socket_bind')
if conf.get('BPF_FRAMEWORK') == 1
libcore_sources += [socket_bind_skel_h]

2
src/core/restrict-ifaces.c
View File

@ -10,7 +10,7 @@
#include "bpf-dlopen.h"
#include "bpf-link.h"
#include "bpf/restrict_ifaces/restrict-ifaces.skel.h"
#include "bpf/restrict_ifaces/restrict-ifaces-skel.h"
static struct restrict_ifaces_bpf *restrict_ifaces_bpf_free(struct restrict_ifaces_bpf *obj) {
restrict_ifaces_bpf__destroy(obj);

128
tools/build-bpf-skel.py
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@ -1,128 +0,0 @@
#!/usr/bin/env python3
# SPDX-License-Identifier: LGPL-2.1-or-later
import argparse
import logging
import pathlib
import re
import subprocess
import sys
def clang_arch_flag(arch):
return '-D__{}__'.format(arch)
def target_triplet():
gcc_exec = 'gcc'
try:
return subprocess.check_output([gcc_exec, '-dumpmachine'],
universal_newlines=True).strip()
except subprocess.CalledProcessError as e:
logging.error('Failed to get target triplet: {}'.format(e))
except FileNotFoundError:
logging.error('gcc not installed')
return None
def clang_compile(clang_exec, clang_flags, src_c, out_file, target_arch,
target_triplet):
clang_args = [clang_exec, *clang_flags, target_arch, '-I.']
if target_triplet:
clang_args += [
'-isystem',
'/usr/include/{}'.format(target_triplet)]
clang_args += [
'-idirafter',
'/usr/local/include',
'-idirafter',
'/usr/include']
clang_args += [src_c, '-o', out_file]
logging.debug('{}'.format(' '.join(clang_args)))
subprocess.check_call(clang_args)
def llvm_strip(llvm_strip_exec, in_file):
llvm_strip_args = [llvm_strip_exec, '-g', in_file]
logging.debug('Stripping useless DWARF info:')
logging.debug('{}'.format(' '.join(llvm_strip_args)))
subprocess.check_call(llvm_strip_args)
def gen_bpf_skeleton(bpftool_exec, in_file, out_fd):
bpftool_args = [bpftool_exec, 'g', 's', in_file]
logging.debug('Generating BPF skeleton:')
logging.debug('{}'.format(' '.join(bpftool_args)))
skel = subprocess.check_output(bpftool_args, universal_newlines=True)
# libbpf is used via dlopen(), so rename symbols as defined
# in src/shared/bpf-dlopen.h
skel = re.sub(r'(bpf_object__\w+_skeleton)', r'sym_\1', skel)
out_fd.write(skel)
def bpf_build(args):
clang_flags = [
'-Wno-compare-distinct-pointer-types',
'-O2',
'-target',
'bpf',
'-g',
'-c',
]
clang_out_path = pathlib.Path(args.bpf_src_c).with_suffix('.o')
with clang_out_path.open(mode='w') as clang_out, \
open(args.bpf_skel_h, mode='w') as bpf_skel_h:
clang_compile(clang_exec=args.clang_exec,
clang_flags=clang_flags,
src_c=args.bpf_src_c,
out_file=clang_out.name,
target_arch=clang_arch_flag(args.arch),
target_triplet=target_triplet())
llvm_strip(llvm_strip_exec=args.llvm_strip_exec, in_file=clang_out.name)
gen_bpf_skeleton(bpftool_exec=args.bpftool_exec,
in_file=clang_out.name,
out_fd=bpf_skel_h)
if __name__ == '__main__':
parser = argparse.ArgumentParser()
parser.add_argument(
'bpf_src_c',
help='Path to *.c source of BPF program in systemd source tree \
relative to the work directory')
parser.add_argument(
'bpf_skel_h',
help='Path to C header file')
parser.add_argument(
'--clang_exec',
help='Path to clang exec')
parser.add_argument(
'--llvm_strip_exec',
help='Path to llvm-strip exec')
parser.add_argument(
'--bpftool_exec',
help='Path to bpftool exec')
parser.add_argument(
'--arch',
help='Target CPU architecture',
default='x86_64')
args = parser.parse_args();
logging.basicConfig(stream=sys.stderr, level=logging.WARNING)
bpf_build(args)