@@ -635,12 +635,12 @@ test coverage.
Q: clang flag for target bpf?
-----------------------------
-Q: In some cases clang flag ``-target bpf`` is used but in other cases the
+Q: In some cases clang flag ``--target=bpf`` is used but in other cases the
default clang target, which matches the underlying architecture, is used.
What is the difference and when I should use which?
A: Although LLVM IR generation and optimization try to stay architecture
-independent, ``-target <arch>`` still has some impact on generated code:
+independent, ``--target=<arch>`` still has some impact on generated code:
- BPF program may recursively include header file(s) with file scope
inline assembly codes. The default target can handle this well,
@@ -658,7 +658,7 @@ independent, ``-target <arch>`` still has some impact on generated code:
The clang option ``-fno-jump-tables`` can be used to disable
switch table generation.
-- For clang ``-target bpf``, it is guaranteed that pointer or long /
+- For clang ``--target=bpf``, it is guaranteed that pointer or long /
unsigned long types will always have a width of 64 bit, no matter
whether underlying clang binary or default target (or kernel) is
32 bit. However, when native clang target is used, then it will
@@ -668,7 +668,7 @@ independent, ``-target <arch>`` still has some impact on generated code:
while the BPF LLVM back end still operates in 64 bit. The native
target is mostly needed in tracing for the case of walking ``pt_regs``
or other kernel structures where CPU's register width matters.
- Otherwise, ``clang -target bpf`` is generally recommended.
+ Otherwise, ``clang --target=bpf`` is generally recommended.
You should use default target when:
@@ -685,7 +685,7 @@ when:
into these structures is verified by the BPF verifier and may result
in verification failures if the native architecture is not aligned with
the BPF architecture, e.g. 64-bit. An example of this is
- BPF_PROG_TYPE_SK_MSG require ``-target bpf``
+ BPF_PROG_TYPE_SK_MSG require ``--target=bpf``
.. Links
@@ -990,7 +990,7 @@ format.::
} g2;
int main() { return 0; }
int test() { return 0; }
- -bash-4.4$ clang -c -g -O2 -target bpf t2.c
+ -bash-4.4$ clang -c -g -O2 --target=bpf t2.c
-bash-4.4$ readelf -S t2.o
......
[ 8] .BTF PROGBITS 0000000000000000 00000247
@@ -1000,7 +1000,7 @@ format.::
[10] .rel.BTF.ext REL 0000000000000000 000007e0
0000000000000040 0000000000000010 16 9 8
......
- -bash-4.4$ clang -S -g -O2 -target bpf t2.c
+ -bash-4.4$ clang -S -g -O2 --target=bpf t2.c
-bash-4.4$ cat t2.s
......
.section .BTF,"",@progbits
@@ -28,7 +28,7 @@ For example, for the following code::
return g1 + g2 + l1 + l2;
}
-Compiled with ``clang -target bpf -O2 -c test.c``, the following is
+Compiled with ``clang --target=bpf -O2 -c test.c``, the following is
the code with ``llvm-objdump -dr test.o``::
0: 18 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r1 = 0 ll
@@ -155,7 +155,7 @@ and ``call`` instructions. For example::
return gfunc(a, b) + lfunc(a, b) + global;
}
-Compiled with ``clang -target bpf -O2 -c test.c``, we will have
+Compiled with ``clang --target=bpf -O2 -c test.c``, we will have
following code with `llvm-objdump -dr test.o``::
Disassembly of section .text:
@@ -201,7 +201,7 @@ The following is an example to show how R_BPF_64_ABS64 could be generated::
int global() { return 0; }
struct t { void *g; } gbl = { global };
-Compiled with ``clang -target bpf -O2 -g -c test.c``, we will see a
+Compiled with ``clang --target=bpf -O2 -g -c test.c``, we will see a
relocation below in ``.data`` section with command
``llvm-readelf -r test.o``::
@@ -58,7 +58,7 @@ entrypoints.lskel.h: $(OUTPUT)/entrypoints.bpf.o | $(BPFTOOL)
$(OUTPUT)/entrypoints.bpf.o: entrypoints.bpf.c $(OUTPUT)/vmlinux.h $(BPFOBJ) | $(OUTPUT)
$(call msg,BPF,$@)
- $(Q)$(CLANG) -g -O2 -target bpf $(INCLUDES) \
+ $(Q)$(CLANG) -g -O2 --target=bpf $(INCLUDES) \
-c $(filter %.c,$^) -o $@ && \
$(LLVM_STRIP) -g $@
@@ -50,7 +50,7 @@ iterators.lskel-%.h: $(OUTPUT)/%/iterators.bpf.o | $(BPFTOOL)
$(OUTPUT)/%/iterators.bpf.o: iterators.bpf.c $(BPFOBJ) | $(OUTPUT)
$(call msg,BPF,$@)
$(Q)mkdir -p $(@D)
- $(Q)$(CLANG) -g -O2 -target bpf -m$* $(INCLUDES) \
+ $(Q)$(CLANG) -g -O2 --target=bpf -m$* $(INCLUDES) \
-c $(filter %.c,$^) -o $@ && \
$(LLVM_STRIP) -g $@
@@ -248,7 +248,7 @@ BTF_LLC_PROBE := $(shell $(LLC) -march=bpf -mattr=help 2>&1 | grep dwarfris)
BTF_PAHOLE_PROBE := $(shell $(BTF_PAHOLE) --help 2>&1 | grep BTF)
BTF_OBJCOPY_PROBE := $(shell $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm')
BTF_LLVM_PROBE := $(shell echo "int main() { return 0; }" | \
- $(CLANG) -target bpf -O2 -g -c -x c - -o ./llvm_btf_verify.o; \
+ $(CLANG) --target=bpf -O2 -g -c -x c - -o ./llvm_btf_verify.o; \
$(LLVM_READELF) -S ./llvm_btf_verify.o | grep BTF; \
/bin/rm -f ./llvm_btf_verify.o)
@@ -370,7 +370,7 @@ endif
clean-files += vmlinux.h
# Get Clang's default includes on this system, as opposed to those seen by
-# '-target bpf'. This fixes "missing" files on some architectures/distros,
+# '--target=bpf'. This fixes "missing" files on some architectures/distros,
# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
#
# Use '-idirafter': Don't interfere with include mechanics except where the
@@ -392,7 +392,7 @@ $(obj)/xdp_router_ipv4.bpf.o: $(obj)/xdp_sample.bpf.o
$(obj)/%.bpf.o: $(src)/%.bpf.c $(obj)/vmlinux.h $(src)/xdp_sample.bpf.h $(src)/xdp_sample_shared.h
@echo " CLANG-BPF " $@
- $(Q)$(CLANG) -g -O2 -target bpf -D__TARGET_ARCH_$(SRCARCH) \
+ $(Q)$(CLANG) -g -O2 --target=bpf -D__TARGET_ARCH_$(SRCARCH) \
-Wno-compare-distinct-pointer-types -I$(srctree)/include \
-I$(srctree)/samples/bpf -I$(srctree)/tools/include \
-I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES) \
@@ -1 +1,2 @@
-/* dummy .h to trick /usr/include/features.h to work with 'clang -target bpf' */
+/* SPDX-License-Identifier: GPL-2.0 */
+/* dummy .h to trick /usr/include/features.h to work with 'clang --target=bpf' */
@@ -376,7 +376,7 @@ DST_MAC=$(lookup_mac $VETH1 $NS1)
SRC_MAC=$(lookup_mac $VETH0)
DST_IFINDEX=$(cat /sys/class/net/$VETH0/ifindex)
-CLANG_OPTS="-O2 -target bpf -I ../include/"
+CLANG_OPTS="-O2 --target=bpf -I ../include/"
CLANG_OPTS+=" -DSRC_MAC=$SRC_MAC -DDST_MAC=$DST_MAC -DDST_IFINDEX=$DST_IFINDEX"
clang $CLANG_OPTS -c $PROG_SRC -o $BPF_PROG
@@ -86,7 +86,7 @@ BTF_LLC_PROBE := $(shell $(LLC) -march=bpf -mattr=help 2>&1 | grep dwarfris)
BTF_PAHOLE_PROBE := $(shell $(BTF_PAHOLE) --help 2>&1 | grep BTF)
BTF_OBJCOPY_PROBE := $(shell $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm')
BTF_LLVM_PROBE := $(shell echo "int main() { return 0; }" | \
- $(CLANG) -target bpf -O2 -g -c -x c - -o ./llvm_btf_verify.o; \
+ $(CLANG) --target=bpf -O2 -g -c -x c - -o ./llvm_btf_verify.o; \
$(LLVM_READELF) -S ./llvm_btf_verify.o | grep BTF; \
/bin/rm -f ./llvm_btf_verify.o)
@@ -181,7 +181,7 @@ endif
clean-files += vmlinux.h
# Get Clang's default includes on this system, as opposed to those seen by
-# '-target bpf'. This fixes "missing" files on some architectures/distros,
+# '--target=bpf'. This fixes "missing" files on some architectures/distros,
# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
#
# Use '-idirafter': Don't interfere with include mechanics except where the
@@ -198,7 +198,7 @@ EXTRA_BPF_HEADERS_SRC := $(addprefix $(src)/,$(EXTRA_BPF_HEADERS))
$(obj)/%.bpf.o: $(src)/%.bpf.c $(EXTRA_BPF_HEADERS_SRC) $(obj)/vmlinux.h
@echo " CLANG-BPF " $@
- $(Q)$(CLANG) -g -O2 -target bpf -D__TARGET_ARCH_$(SRCARCH) \
+ $(Q)$(CLANG) -g -O2 --target=bpf -D__TARGET_ARCH_$(SRCARCH) \
-Wno-compare-distinct-pointer-types -I$(srctree)/include \
-I$(srctree)/samples/bpf -I$(srctree)/tools/include \
-I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES) \
@@ -260,9 +260,9 @@ EXAMPLES
This is example BPF application with two BPF programs and a mix of BPF maps
and global variables. Source code is split across two source code files.
-**$ clang -target bpf -g example1.bpf.c -o example1.bpf.o**
+**$ clang --target=bpf -g example1.bpf.c -o example1.bpf.o**
-**$ clang -target bpf -g example2.bpf.c -o example2.bpf.o**
+**$ clang --target=bpf -g example2.bpf.c -o example2.bpf.o**
**$ bpftool gen object example.bpf.o example1.bpf.o example2.bpf.o**
@@ -216,7 +216,7 @@ $(OUTPUT)%.bpf.o: skeleton/%.bpf.c $(OUTPUT)vmlinux.h $(LIBBPF_BOOTSTRAP)
-I$(srctree)/tools/include/uapi/ \
-I$(LIBBPF_BOOTSTRAP_INCLUDE) \
-g -O2 -Wall -fno-stack-protector \
- -target bpf -c $< -o $@
+ --target=bpf -c $< -o $@
$(Q)$(LLVM_STRIP) -g $@
$(OUTPUT)%.skel.h: $(OUTPUT)%.bpf.o $(BPFTOOL_BOOTSTRAP)
@@ -62,7 +62,7 @@ $(OUTPUT)/%.skel.h: $(OUTPUT)/%.bpf.o | $(BPFTOOL)
$(QUIET_GEN)$(BPFTOOL) gen skeleton $< > $@
$(OUTPUT)/%.bpf.o: %.bpf.c $(BPFOBJ) | $(OUTPUT)
- $(QUIET_GEN)$(CLANG) -g -O2 -target bpf $(INCLUDES) \
+ $(QUIET_GEN)$(CLANG) -g -O2 --target=bpf $(INCLUDES) \
-c $(filter %.c,$^) -o $@ && \
$(LLVM_STRIP) -g $@
@@ -372,7 +372,7 @@ $(OUTPUT)test-libzstd.bin:
$(BUILD) -lzstd
$(OUTPUT)test-clang-bpf-co-re.bin:
- $(CLANG) -S -g -target bpf -o - $(patsubst %.bin,%.c,$(@F)) | \
+ $(CLANG) -S -g --target=bpf -o - $(patsubst %.bin,%.c,$(@F)) | \
grep BTF_KIND_VAR
$(OUTPUT)test-file-handle.bin:
@@ -669,7 +669,7 @@ llvm.*::
"$CLANG_OPTIONS $PERF_BPF_INC_OPTIONS $KERNEL_INC_OPTIONS " \
"-Wno-unused-value -Wno-pointer-sign " \
"-working-directory $WORKING_DIR " \
- "-c \"$CLANG_SOURCE\" -target bpf $CLANG_EMIT_LLVM -O2 -o - $LLVM_OPTIONS_PIPE"
+ "-c \"$CLANG_SOURCE\" --target=bpf $CLANG_EMIT_LLVM -O2 -o - $LLVM_OPTIONS_PIPE"
llvm.clang-opt::
Options passed to clang.
@@ -1057,7 +1057,7 @@ $(SKEL_TMP_OUT) $(LIBAPI_OUTPUT) $(LIBBPF_OUTPUT) $(LIBPERF_OUTPUT) $(LIBSUBCMD_
ifdef BUILD_BPF_SKEL
BPFTOOL := $(SKEL_TMP_OUT)/bootstrap/bpftool
# Get Clang's default includes on this system, as opposed to those seen by
-# '-target bpf'. This fixes "missing" files on some architectures/distros,
+# '--target=bpf'. This fixes "missing" files on some architectures/distros,
# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
#
# Use '-idirafter': Don't interfere with include mechanics except where the
@@ -1081,7 +1081,7 @@ $(BPFTOOL): | $(SKEL_TMP_OUT)
OUTPUT=$(SKEL_TMP_OUT)/ bootstrap
$(SKEL_TMP_OUT)/%.bpf.o: util/bpf_skel/%.bpf.c $(LIBBPF) | $(SKEL_TMP_OUT)
- $(QUIET_CLANG)$(CLANG) -g -O2 -target bpf -Wall -Werror $(BPF_INCLUDE) $(TOOLS_UAPI_INCLUDE) \
+ $(QUIET_CLANG)$(CLANG) -g -O2 --target=bpf -Wall -Werror $(BPF_INCLUDE) $(TOOLS_UAPI_INCLUDE) \
-c $(filter util/bpf_skel/%.bpf.c,$^) -o $@
$(SKEL_OUT)/%.skel.h: $(SKEL_TMP_OUT)/%.bpf.o | $(BPFTOOL)
@@ -25,7 +25,7 @@
"$CLANG_OPTIONS $PERF_BPF_INC_OPTIONS $KERNEL_INC_OPTIONS " \
"-Wno-unused-value -Wno-pointer-sign " \
"-working-directory $WORKING_DIR " \
- "-c \"$CLANG_SOURCE\" -target bpf $CLANG_EMIT_LLVM -g -O2 -o - $LLVM_OPTIONS_PIPE"
+ "-c \"$CLANG_SOURCE\" --target=bpf $CLANG_EMIT_LLVM -g -O2 -o - $LLVM_OPTIONS_PIPE"
struct llvm_param llvm_param = {
.clang_path = "clang",
@@ -569,7 +569,7 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
pr_err("ERROR:\tunable to compile %s\n", path);
pr_err("Hint:\tCheck error message shown above.\n");
pr_err("Hint:\tYou can also pre-compile it into .o using:\n");
- pr_err(" \t\tclang -target bpf -O2 -c %s\n", path);
+ pr_err(" \t\tclang --target=bpf -O2 -c %s\n", path);
pr_err(" \twith proper -I and -D options.\n");
goto errout;
}
@@ -332,7 +332,7 @@ $(RESOLVE_BTFIDS): $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/resolve_btfids \
OUTPUT=$(HOST_BUILD_DIR)/resolve_btfids/ BPFOBJ=$(HOST_BPFOBJ)
# Get Clang's default includes on this system, as opposed to those seen by
-# '-target bpf'. This fixes "missing" files on some architectures/distros,
+# '--target=bpf'. This fixes "missing" files on some architectures/distros,
# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
#
# Use '-idirafter': Don't interfere with include mechanics except where the
@@ -373,12 +373,12 @@ $(OUTPUT)/cgroup_getset_retval_hooks.o: cgroup_getset_retval_hooks.h
# $3 - CFLAGS
define CLANG_BPF_BUILD_RULE
$(call msg,CLNG-BPF,$(TRUNNER_BINARY),$2)
- $(Q)$(CLANG) $3 -O2 -target bpf -c $1 -mcpu=v3 -o $2
+ $(Q)$(CLANG) $3 -O2 --target=bpf -c $1 -mcpu=v3 -o $2
endef
# Similar to CLANG_BPF_BUILD_RULE, but with disabled alu32
define CLANG_NOALU32_BPF_BUILD_RULE
$(call msg,CLNG-BPF,$(TRUNNER_BINARY),$2)
- $(Q)$(CLANG) $3 -O2 -target bpf -c $1 -mcpu=v2 -o $2
+ $(Q)$(CLANG) $3 -O2 --target=bpf -c $1 -mcpu=v2 -o $2
endef
# Build BPF object using GCC
define GCC_BPF_BUILD_RULE
@@ -1 +1,2 @@
-/* dummy .h to trick /usr/include/features.h to work with 'clang -target bpf' */
+/* SPDX-License-Identifier: GPL-2.0 */
+/* dummy .h to trick /usr/include/features.h to work with 'clang --target=bpf' */
@@ -167,7 +167,7 @@ $(RESOLVE_BTFIDS): $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/resolve_btfids \
OUTPUT=$(HOST_BUILD_DIR)/resolve_btfids/ BPFOBJ=$(HOST_BPFOBJ)
# Get Clang's default includes on this system, as opposed to those seen by
-# '-target bpf'. This fixes "missing" files on some architectures/distros,
+# '--target=bpf'. This fixes "missing" files on some architectures/distros,
# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
#
# Use '-idirafter': Don't interfere with include mechanics except where the
@@ -196,12 +196,12 @@ CLANG_CFLAGS = $(CLANG_SYS_INCLUDES) \
# $3 - CFLAGS
define CLANG_BPF_BUILD_RULE
$(call msg,CLNG-BPF,$(TRUNNER_BINARY),$2)
- $(Q)$(CLANG) $3 -O2 -target bpf -c $1 -mcpu=v3 -o $2
+ $(Q)$(CLANG) $3 -O2 --target=bpf -c $1 -mcpu=v3 -o $2
endef
# Similar to CLANG_BPF_BUILD_RULE, but with disabled alu32
define CLANG_NOALU32_BPF_BUILD_RULE
$(call msg,CLNG-BPF,$(TRUNNER_BINARY),$2)
- $(Q)$(CLANG) $3 -O2 -target bpf -c $1 -mcpu=v2 -o $2
+ $(Q)$(CLANG) $3 -O2 --target=bpf -c $1 -mcpu=v2 -o $2
endef
# Build BPF object using GCC
define GCC_BPF_BUILD_RULE
@@ -112,7 +112,7 @@ $(MAKE_DIRS):
mkdir -p $@
# Get Clang's default includes on this system, as opposed to those seen by
-# '-target bpf'. This fixes "missing" files on some architectures/distros,
+# '--target=bpf'. This fixes "missing" files on some architectures/distros,
# such as asm/byteorder.h, asm/socket.h, asm/sockios.h, sys/cdefs.h etc.
#
# Use '-idirafter': Don't interfere with include mechanics except where the
@@ -130,7 +130,7 @@ endif
CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
$(OUTPUT)/nat6to4.o: nat6to4.c $(BPFOBJ) | $(MAKE_DIRS)
- $(CLANG) -O2 -target bpf -c $< $(CCINCLUDE) $(CLANG_SYS_INCLUDES) -o $@
+ $(CLANG) -O2 --target=bpf -c $< $(CCINCLUDE) $(CLANG_SYS_INCLUDES) -o $@
$(BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile) \
$(APIDIR)/linux/bpf.h \
@@ -24,7 +24,7 @@ CLANG_FLAGS = -I. -I$(APIDIR) \
$(OUTPUT)/%.o: %.c
$(CLANG) $(CLANG_FLAGS) \
- -O2 -target bpf -emit-llvm -c $< -o - | \
+ -O2 --target=bpf -emit-llvm -c $< -o - | \
$(LLC) -march=bpf -mcpu=$(CPU) $(LLC_FLAGS) -filetype=obj -o $@
TEST_PROGS += ./tdc.sh