[PATCH RFC bpf-next 00/10] improve/fix cross-compilation for bpf samples

[PATCH RFC bpf-next 00/10] improve/fix cross-compilation for bpf samples

[Ivan Khoronzhuk]

This series contains mainly fixes/improvements for cross-compilation
(also verified on native platform build), tested on arm, but intended
for any arch.

The several patches are related to llvm clang and should be out of this
series or even fixed in another way, and here just to get comments:
  arm: include: asm: swab: mask rev16 instruction for clang
  arm: include: asm: unified: mask .syntax unified for clang

Also, only for armv7, there is one more problem related to long and
void type sizes for 32 bits, while the BPF LLVM back end still
operates in 64 bit, but that's another story.

Smth related not only for cross-compilation and can have impact on other
archs and build environments, so might be good idea to verify it in order
to add appropriate changes, some warn options can be tuned, so comment.

Ivan Khoronzhuk (10):
  samples: bpf: Makefile: use --target from cross-compile
  samples: bpf: Makefile: remove target for native build
  libbpf: Makefile: add C/CXX/LDFLAGS to libbpf.so and test_libpf
    targets
  samples: bpf: use own EXTRA_CFLAGS for clang commands
  samples: bpf: Makefile: use vars from KBUILD_CFLAGS to handle linux
    headers
  samples: bpf: makefile: fix HDR_PROBE
  samples: bpf: add makefile.prog for separate CC build
  samples: bpf: Makefile: base progs build on Makefile.progs
  arm: include: asm: swab: mask rev16 instruction for clang
  arm: include: asm: unified: mask .syntax unified for clang

 arch/arm/include/asm/swab.h    |   3 +
 arch/arm/include/asm/unified.h |   6 +-
 samples/bpf/Makefile           | 177 +++++++++++++++++++--------------
 samples/bpf/Makefile.prog      |  77 ++++++++++++++
 samples/bpf/README.rst         |   7 ++
 tools/lib/bpf/Makefile         |  11 +-
 6 files changed, 205 insertions(+), 76 deletions(-)
 create mode 100644 samples/bpf/Makefile.prog

-- 
2.17.1

[PATCH RFC bpf-next 01/10] samples: bpf: Makefile: use --target from cross-compile

[Ivan Khoronzhuk]

For cross compiling the target triple can be inherited from
cross-compile prefix as it's done in CLANG_FLAGS from kernel makefile.
So copy-paste this decision from kernel Makefile.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
 samples/bpf/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 1d9be26b4edd..61b7394b811e 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -196,6 +196,8 @@ BTF_PAHOLE ?= pahole
 # Detect that we're cross compiling and use the cross compiler
 ifdef CROSS_COMPILE
 HOSTCC = $(CROSS_COMPILE)gcc
+CLANG_ARCH_ARGS = --target=$(notdir $(CROSS_COMPILE:%-=%))
+else
 CLANG_ARCH_ARGS = -target $(ARCH)
 endif
 
-- 
2.17.1

[PATCH RFC bpf-next 02/10] samples: bpf: Makefile: remove target for native build

[Ivan Khoronzhuk]

No need to set --target for native build, at least for arm, the
default target will be used anyway. In case of arm, for at least
clang 5 - 10 it causes error like:

clang: warning: unknown platform, assuming -mfloat-abi=soft
LLVM ERROR: Unsupported calling convention
make[2]: *** [/home/root/snapshot/samples/bpf/Makefile:299:
/home/root/snapshot/samples/bpf/sockex1_kern.o] Error 1

To make the platform to be known, only set to real triple helps:
--target=arm-linux-gnueabihf
or just drop the target key to use default one. Decision to just drop
it and thus default target will be used, looks better.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
 samples/bpf/Makefile | 2 --
 1 file changed, 2 deletions(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 61b7394b811e..a2953357927e 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -197,8 +197,6 @@ BTF_PAHOLE ?= pahole
 ifdef CROSS_COMPILE
 HOSTCC = $(CROSS_COMPILE)gcc
 CLANG_ARCH_ARGS = --target=$(notdir $(CROSS_COMPILE:%-=%))
-else
-CLANG_ARCH_ARGS = -target $(ARCH)
 endif
 
 # Don't evaluate probes and warnings if we need to run make recursively
-- 
2.17.1

[PATCH RFC bpf-next 03/10] libbpf: Makefile: add C/CXX/LDFLAGS to libbpf.so and test_libpf targets

[Ivan Khoronzhuk]

In case of LDFLAGS and EXTRA_CC flags there is no way to pass them
correctly to build command, for instance when --sysroot is used or
external libraries are used, like -lelf. In follow patches this is
used for samples/bpf cross-compiling.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
 tools/lib/bpf/Makefile | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index 844f6cd79c03..d606d249e334 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -99,6 +99,10 @@ else
   CFLAGS := -g -Wall
 endif
 
+ifdef EXTRA_CXXFLAGS
+  CXXFLAGS := $(EXTRA_CXXFLAGS)
+endif
+
 ifeq ($(feature-libelf-mmap), 1)
   override CFLAGS += -DHAVE_LIBELF_MMAP_SUPPORT
 endif
@@ -179,8 +183,9 @@ $(BPF_IN): force elfdep bpfdep
 $(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION)
 
 $(OUTPUT)libbpf.so.$(LIBBPF_VERSION): $(BPF_IN)
-	$(QUIET_LINK)$(CC) --shared -Wl,-soname,libbpf.so.$(VERSION) \
-				    -Wl,--version-script=$(VERSION_SCRIPT) $^ -lelf -o $@
+	$(QUIET_LINK)$(CC) $(LDFLAGS) \
+		--shared -Wl,-soname,libbpf.so.$(VERSION) \
+		-Wl,--version-script=$(VERSION_SCRIPT) $^ -lelf -o $@
 	@ln -sf $(@F) $(OUTPUT)libbpf.so
 	@ln -sf $(@F) $(OUTPUT)libbpf.so.$(VERSION)
 
@@ -188,7 +193,7 @@ $(OUTPUT)libbpf.a: $(BPF_IN)
 	$(QUIET_LINK)$(RM) $@; $(AR) rcs $@ $^
 
 $(OUTPUT)test_libbpf: test_libbpf.cpp $(OUTPUT)libbpf.a
-	$(QUIET_LINK)$(CXX) $(INCLUDES) $^ -lelf -o $@
+	$(QUIET_LINK)$(CXX) $(CXXFLAGS) $(LDFLAGS) $(INCLUDES) $^ -lelf -o $@
 
 $(OUTPUT)libbpf.pc:
 	$(QUIET_GEN)sed -e "s|@PREFIX@|$(prefix)|" \
-- 
2.17.1

[PATCH RFC bpf-next 04/10] samples: bpf: use own EXTRA_CFLAGS for clang commands

[Ivan Khoronzhuk]

It can overlap with CFLAGS used for libraries built with gcc if
not now then in following patches. Correct it here for simplicity.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
 samples/bpf/Makefile | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index a2953357927e..cdd742c05200 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -219,10 +219,10 @@ BTF_LLVM_PROBE := $(shell echo "int main() { return 0; }" | \
 			  /bin/rm -f ./llvm_btf_verify.o)
 
 ifneq ($(BTF_LLVM_PROBE),)
-	EXTRA_CFLAGS += -g
+	CLANG_EXTRA_CFLAGS += -g
 else
 ifneq ($(and $(BTF_LLC_PROBE),$(BTF_PAHOLE_PROBE),$(BTF_OBJCOPY_PROBE)),)
-	EXTRA_CFLAGS += -g
+	CLANG_EXTRA_CFLAGS += -g
 	LLC_FLAGS += -mattr=dwarfris
 	DWARF2BTF = y
 endif
@@ -281,8 +281,8 @@ $(obj)/hbm_edt_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
 # useless for BPF samples.
 $(obj)/%.o: $(src)/%.c
 	@echo "  CLANG-bpf " $@
-	$(Q)$(CLANG) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(EXTRA_CFLAGS) -I$(obj) \
-		-I$(srctree)/tools/testing/selftests/bpf/ \
+	$(Q)$(CLANG) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) $(CLANG_EXTRA_CFLAGS) \
+		-I$(obj) -I$(srctree)/tools/testing/selftests/bpf/ \
 		-D__KERNEL__ -D__BPF_TRACING__ -Wno-unused-value -Wno-pointer-sign \
 		-D__TARGET_ARCH_$(SRCARCH) -Wno-compare-distinct-pointer-types \
 		-Wno-gnu-variable-sized-type-not-at-end \
-- 
2.17.1

[PATCH RFC bpf-next 05/10] samples: bpf: Makefile: use vars from KBUILD_CFLAGS to handle linux headers

[Ivan Khoronzhuk]

The kernel headers are reused from samples bpf, and autoconf.h is not
enough to reflect complete configuration for clang. One of such
configurations is __LINUX_ARM_ARCH__ min version used as instruction
set selector. In another case an error like "SMP is not
supported" for arm and others errors are issued and final object is
not correct.
---
 samples/bpf/Makefile | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index cdd742c05200..9232efa2b1b3 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -186,6 +186,13 @@ HOSTLDLIBS_map_perf_test	+= -lrt
 HOSTLDLIBS_test_overhead	+= -lrt
 HOSTLDLIBS_xdpsock		+= -pthread
 
+# Strip all expet -D options needed to handle linux headers
+# for arm it's __LINUX_ARM_ARCH__ and potentially others fork vars
+D_OPTIONS = $(shell echo "$(KBUILD_CFLAGS) " | sed 's/[[:blank:]]/\n/g' | \
+	sed '/^-D/!d' | tr '\n' ' ')
+
+CLANG_EXTRA_CFLAGS += $(D_OPTIONS)
+
 # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
 #  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
 LLC ?= llc
-- 
2.17.1

[PATCH RFC bpf-next 06/10] samples: bpf: makefile: fix HDR_PROBE

[Ivan Khoronzhuk]

echo should be replace on echo -e to handle \n correctly, but instead,
replace it on printf as some systems can't handle echo -e.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
 samples/bpf/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 9232efa2b1b3..043f9cc14cdd 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -208,7 +208,7 @@ endif
 
 # Don't evaluate probes and warnings if we need to run make recursively
 ifneq ($(src),)
-HDR_PROBE := $(shell echo "\#include <linux/types.h>\n struct list_head { int a; }; int main() { return 0; }" | \
+HDR_PROBE := $(shell printf "\#include <linux/types.h>\n struct list_head { int a; }; int main() { return 0; }" | \
 	$(HOSTCC) $(KBUILD_HOSTCFLAGS) -x c - -o /dev/null 2>/dev/null && \
 	echo okay)
 
-- 
2.17.1

[PATCH RFC bpf-next 07/10] samples: bpf: add makefile.prog for separate CC build

[Ivan Khoronzhuk]

The HOSTCC is supposed to build binaries and tools running on the host
afterwards, in order to simplify build or so, like "fixdep" or else.
In case of cross compiling "fixdep" is executed on host when the rest
samples should run on target arch. In order to build binaries for
target arch with CC and tools running on host with HOSTCC, lets add
Makefile.prog for simplicity, having definition and routines similar
to ones, used in script/Makefile.host. That allows later add
cross-compilation to samples/bpf with minimum changes.

Makefile.prog contains only stuff needed for samples/bpf, potentially
can be reused and sophisticated for other prog sets later and now
needed only for unblocking tricky samples/bpf cross compilation.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
 samples/bpf/Makefile.prog | 77 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)
 create mode 100644 samples/bpf/Makefile.prog

diff --git a/samples/bpf/Makefile.prog b/samples/bpf/Makefile.prog
new file mode 100644
index 000000000000..d5d02fbb5e6e
--- /dev/null
+++ b/samples/bpf/Makefile.prog
@@ -0,0 +1,77 @@
+# SPDX-License-Identifier: GPL-2.0
+# ==========================================================================
+# Building binaries on the host system
+# Binaries are not used during the compilation of the kernel, and intendent to
+# be build for target board, target board can be host ofc. Added to build
+# binaries to run not on host system.
+#
+# Both C and C++ are supported, but preferred language is C for such utilities.
+#
+# Sample syntax (see Documentation/kbuild/makefiles.rst for reference)
+# progs-y := xdpsock_example
+# Will compile xdpsock_example.c and create an executable named xdpsock_example
+#
+# progs-y    := xdpsock
+# xdpsock-objs := xdpsock_user.o xdpsock_user2.o
+# Will compile xdpsock.c and xdpsock.c, and then link the executable
+# xdpsock, based on xdpsock_user.o and xdpsock_user2.o
+#
+# Inherited from scripts/Makefile.host
+#
+__progs := $(sort $(progs-y))
+
+# C code
+# Executables compiled from a single .c file
+prog-csingle	:= $(foreach m,$(__progs), \
+			$(if $($(m)-objs)$($(m)-cxxobjs),,$(m)))
+
+# C executables linked based on several .o files
+prog-cmulti	:= $(foreach m,$(__progs),\
+		   $(if $($(m)-cxxobjs),,$(if $($(m)-objs),$(m))))
+
+# Object (.o) files compiled from .c files
+prog-cobjs	:= $(sort $(foreach m,$(__progs),$($(m)-objs)))
+
+prog-csingle	:= $(addprefix $(obj)/,$(prog-csingle))
+prog-cmulti	:= $(addprefix $(obj)/,$(prog-cmulti))
+prog-cobjs	:= $(addprefix $(obj)/,$(prog-cobjs))
+
+#####
+# Handle options to gcc. Support building with separate output directory
+
+_progc_flags   = $(PROGS_CFLAGS) \
+                 $(PROGCFLAGS_$(basetarget).o)
+
+# $(objtree)/$(obj) for including generated headers from checkin source files
+ifeq ($(KBUILD_EXTMOD),)
+ifdef building_out_of_srctree
+_progc_flags   += -I $(objtree)/$(obj)
+endif
+endif
+
+progc_flags    = -Wp,-MD,$(depfile) $(_progc_flags)
+
+# Create executable from a single .c file
+# prog-csingle -> Executable
+quiet_cmd_prog-csingle 	= CC  $@
+      cmd_prog-csingle	= $(CC) $(progc_flags) $(PROGS_LDFLAGS) -o $@ $< \
+		$(PROGS_LDLIBS) $(PROGLDLIBS_$(@F))
+$(prog-csingle): $(obj)/%: $(src)/%.c FORCE
+	$(call if_changed_dep,prog-csingle)
+
+# Link an executable based on list of .o files, all plain c
+# prog-cmulti -> executable
+quiet_cmd_prog-cmulti	= LD  $@
+      cmd_prog-cmulti	= $(CC) $(progc_flags) $(PROGS_LDFLAGS) -o $@ \
+			  $(addprefix $(obj)/,$($(@F)-objs)) \
+			  $(PROGS_LDLIBS) $(PROGLDLIBS_$(@F))
+$(prog-cmulti): $(prog-cobjs) FORCE
+	$(call if_changed,prog-cmulti)
+$(call multi_depend, $(prog-cmulti), , -objs)
+
+# Create .o file from a single .c file
+# prog-cobjs -> .o
+quiet_cmd_prog-cobjs	= CC  $@
+      cmd_prog-cobjs	= $(CC) $(progc_flags) -c -o $@ $<
+$(prog-cobjs): $(obj)/%.o: $(src)/%.c FORCE
+	$(call if_changed_dep,prog-cobjs)
-- 
2.17.1

[PATCH RFC bpf-next 08/10] samples: bpf: Makefile: base progs build on Makefile.progs

[Ivan Khoronzhuk]

The main reason for that - HOSTCC and CC have different aims.
It was tested for arm cross compilation, based on linaro toolchain,
but should work for others.

In order to split cross compilation with host build, base bpf samples
on Makefile.progs. I've verified it on arm with adding SYSROOT.
It's also convenient when debug is with NFC.
To cross-compile I've used:

export ARCH=arm
export CROSS_COMPILE=arm-linux-gnueabihf-
make -j4 samples/bpf/ SYSROOT="path/to/sysroot"

Sysroot contains correct headers installed ofc.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
 samples/bpf/Makefile   | 164 ++++++++++++++++++++++++-----------------
 samples/bpf/README.rst |   7 ++
 2 files changed, 102 insertions(+), 69 deletions(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 043f9cc14cdd..ed7131851172 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -4,55 +4,53 @@ BPF_SAMPLES_PATH ?= $(abspath $(srctree)/$(src))
 TOOLS_PATH := $(BPF_SAMPLES_PATH)/../../tools
 
 # List of programs to build
-hostprogs-y := test_lru_dist
-hostprogs-y += sock_example
-hostprogs-y += fds_example
-hostprogs-y += sockex1
-hostprogs-y += sockex2
-hostprogs-y += sockex3
-hostprogs-y += tracex1
-hostprogs-y += tracex2
-hostprogs-y += tracex3
-hostprogs-y += tracex4
-hostprogs-y += tracex5
-hostprogs-y += tracex6
-hostprogs-y += tracex7
-hostprogs-y += test_probe_write_user
-hostprogs-y += trace_output
-hostprogs-y += lathist
-hostprogs-y += offwaketime
-hostprogs-y += spintest
-hostprogs-y += map_perf_test
-hostprogs-y += test_overhead
-hostprogs-y += test_cgrp2_array_pin
-hostprogs-y += test_cgrp2_attach
-hostprogs-y += test_cgrp2_sock
-hostprogs-y += test_cgrp2_sock2
-hostprogs-y += xdp1
-hostprogs-y += xdp2
-hostprogs-y += xdp_router_ipv4
-hostprogs-y += test_current_task_under_cgroup
-hostprogs-y += trace_event
-hostprogs-y += sampleip
-hostprogs-y += tc_l2_redirect
-hostprogs-y += lwt_len_hist
-hostprogs-y += xdp_tx_iptunnel
-hostprogs-y += test_map_in_map
-hostprogs-y += per_socket_stats_example
-hostprogs-y += xdp_redirect
-hostprogs-y += xdp_redirect_map
-hostprogs-y += xdp_redirect_cpu
-hostprogs-y += xdp_monitor
-hostprogs-y += xdp_rxq_info
-hostprogs-y += syscall_tp
-hostprogs-y += cpustat
-hostprogs-y += xdp_adjust_tail
-hostprogs-y += xdpsock
-hostprogs-y += xdp_fwd
-hostprogs-y += task_fd_query
-hostprogs-y += xdp_sample_pkts
-hostprogs-y += ibumad
-hostprogs-y += hbm
+progs-y := test_lru_dist
+progs-y += sock_example
+progs-y += fds_example
+progs-y += sockex1
+progs-y += sockex2
+progs-y += sockex3
+progs-y += tracex1
+progs-y += tracex2
+progs-y += tracex3
+progs-y += tracex4
+progs-y += tracex5
+progs-y += tracex6
+progs-y += tracex7
+progs-y += test_probe_write_user
+progs-y += trace_output
+progs-y += lathist
+progs-y += offwaketime
+progs-y += spintest
+progs-y += map_perf_test
+progs-y += test_overhead
+progs-y += test_cgrp2_array_pin
+progs-y += test_cgrp2_attach
+progs-y += test_cgrp2_sock
+progs-y += test_cgrp2_sock2
+progs-y += xdp1
+progs-y += xdp2
+progs-y += xdp_router_ipv4
+progs-y += test_current_task_under_cgroup
+progs-y += trace_event
+progs-y += sampleip
+progs-y += tc_l2_redirect
+progs-y += lwt_len_hist
+progs-y += xdp_tx_iptunnel
+progs-y += test_map_in_map
+progs-y += xdp_redirect_map
+progs-y += xdp_redirect_cpu
+progs-y += xdp_monitor
+progs-y += xdp_rxq_info
+progs-y += syscall_tp
+progs-y += cpustat
+progs-y += xdp_adjust_tail
+progs-y += xdpsock
+progs-y += xdp_fwd
+progs-y += task_fd_query
+progs-y += xdp_sample_pkts
+progs-y += ibumad
+progs-y += hbm
 
 # Libbpf dependencies
 LIBBPF = $(TOOLS_PATH)/lib/bpf/libbpf.a
@@ -111,7 +109,7 @@ ibumad-objs := bpf_load.o ibumad_user.o $(TRACE_HELPERS)
 hbm-objs := bpf_load.o hbm.o $(CGROUP_HELPERS)
 
 # Tell kbuild to always build the programs
-always := $(hostprogs-y)
+always := $(progs-y)
 always += sockex1_kern.o
 always += sockex2_kern.o
 always += sockex3_kern.o
@@ -171,26 +169,51 @@ always += ibumad_kern.o
 always += hbm_out_kern.o
 always += hbm_edt_kern.o
 
-KBUILD_HOSTCFLAGS += -I$(objtree)/usr/include
-KBUILD_HOSTCFLAGS += -I$(srctree)/tools/lib/bpf/
-KBUILD_HOSTCFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
-KBUILD_HOSTCFLAGS += -I$(srctree)/tools/lib/ -I$(srctree)/tools/include
-KBUILD_HOSTCFLAGS += -I$(srctree)/tools/perf
-
-HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
-
-KBUILD_HOSTLDLIBS		+= $(LIBBPF) -lelf
-HOSTLDLIBS_tracex4		+= -lrt
-HOSTLDLIBS_trace_output	+= -lrt
-HOSTLDLIBS_map_perf_test	+= -lrt
-HOSTLDLIBS_test_overhead	+= -lrt
-HOSTLDLIBS_xdpsock		+= -pthread
-
 # Strip all expet -D options needed to handle linux headers
 # for arm it's __LINUX_ARM_ARCH__ and potentially others fork vars
 D_OPTIONS = $(shell echo "$(KBUILD_CFLAGS) " | sed 's/[[:blank:]]/\n/g' | \
 	sed '/^-D/!d' | tr '\n' ' ')
 
+ifdef SYSROOT
+ccflags-y += --sysroot=${SYSROOT}
+ccflags-y += -I${SYSROOT}/usr/include
+CLANG_EXTRA_CFLAGS := $(ccflags-y)
+PROGS_LDFLAGS := -L${SYSROOT}/usr/lib
+endif
+
+ccflags-y += -I$(srctree)/tools/lib/bpf/
+ccflags-y += -I$(srctree)/tools/testing/selftests/bpf/
+ccflags-y += -I$(srctree)/tools/lib/
+ccflags-y += -I$(srctree)/tools/perf
+
+ccflags-y += $(D_OPTIONS)
+ccflags-y += -Wall
+ccflags-y += -Wmissing-prototypes
+ccflags-y += -Wstrict-prototypes
+ccflags-y += -fomit-frame-pointer
+
+PROGS_CFLAGS := $(ccflags-y)
+
+ccflags-y += -I$(objtree)/usr/include
+ccflags-y += -I$(srctree)/tools/include
+
+PROGCFLAGS_bpf_load.o += -I$(objtree)/usr/include -I$(srctree)/tools/include \
+			 -Wno-unused-variable
+PROGCFLAGS_sampleip_user.o += -I$(srctree)/tools/include
+PROGCFLAGS_task_fd_query_user.o += -I$(srctree)/tools/include
+PROGCFLAGS_trace_event_user.o += -I$(srctree)/tools/include
+PROGCFLAGS_trace_output_user.o += -I$(srctree)/tools/include
+PROGCFLAGS_tracex6_user.o += -I$(srctree)/tools/include
+PROGCFLAGS_xdp_sample_pkts_user.o += -I$(srctree)/tools/include
+PROGCFLAGS_xdpsock_user.o += -I$(srctree)/tools/include
+
+PROGS_LDLIBS			:= $(LIBBPF) -lelf
+PROGLDLIBS_tracex4		+= -lrt
+PROGLDLIBS_trace_output		+= -lrt
+PROGLDLIBS_map_perf_test	+= -lrt
+PROGLDLIBS_test_overhead	+= -lrt
+PROGLDLIBS_xdpsock		+= -pthread
+
 CLANG_EXTRA_CFLAGS += $(D_OPTIONS)
 
 # Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
@@ -202,15 +225,14 @@ BTF_PAHOLE ?= pahole
 
 # Detect that we're cross compiling and use the cross compiler
 ifdef CROSS_COMPILE
-HOSTCC = $(CROSS_COMPILE)gcc
 CLANG_ARCH_ARGS = --target=$(notdir $(CROSS_COMPILE:%-=%))
 endif
 
 # Don't evaluate probes and warnings if we need to run make recursively
 ifneq ($(src),)
 HDR_PROBE := $(shell printf "\#include <linux/types.h>\n struct list_head { int a; }; int main() { return 0; }" | \
-	$(HOSTCC) $(KBUILD_HOSTCFLAGS) -x c - -o /dev/null 2>/dev/null && \
-	echo okay)
+	$(CC) $(PROGS_CFLAGS) $(PROGS_LDFLAGS) -x c - -o /dev/null \
+	2>/dev/null && echo okay)
 
 ifeq ($(HDR_PROBE),)
 $(warning WARNING: Detected possible issues with include path.)
@@ -246,7 +268,9 @@ clean:
 
 $(LIBBPF): FORCE
 # Fix up variables inherited from Kbuild that tools/ build system won't like
-	$(MAKE) -C $(dir $@) RM='rm -rf' LDFLAGS= srctree=$(BPF_SAMPLES_PATH)/../../ O=
+	$(MAKE) -C $(dir $@) RM='rm -rf' EXTRA_CFLAGS="$(ccflags-y)" \
+		EXTRA_CXXFLAGS="$(ccflags-y)" LDFLAGS=$(PROGS_LDFLAGS) \
+		srctree=$(BPF_SAMPLES_PATH)/../../ O=
 
 $(obj)/syscall_nrs.h:	$(obj)/syscall_nrs.s FORCE
 	$(call filechk,offsets,__SYSCALL_NRS_H__)
@@ -283,6 +307,8 @@ $(obj)/hbm_out_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
 $(obj)/hbm.o: $(src)/hbm.h
 $(obj)/hbm_edt_kern.o: $(src)/hbm.h $(src)/hbm_kern.h
 
+-include $(BPF_SAMPLES_PATH)/Makefile.prog
+
 # asm/sysreg.h - inline assembly used by it is incompatible with llvm.
 # But, there is no easy way to fix it, so just exclude it since it is
 # useless for BPF samples.
diff --git a/samples/bpf/README.rst b/samples/bpf/README.rst
index 5f27e4faca50..6b5e4eace977 100644
--- a/samples/bpf/README.rst
+++ b/samples/bpf/README.rst
@@ -74,3 +74,10 @@ samples for the cross target.
 export ARCH=arm64
 export CROSS_COMPILE="aarch64-linux-gnu-"
 make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
+
+If need to use environment of target board, the SYSROOT also can be set,
+pointing on FS of target board:
+
+make samples/bpf/ LLC=~/git/llvm/build/bin/llc \
+     CLANG=~/git/llvm/build/bin/clang \
+     SYSROOT=~/some_sdk/linux-devkit/sysroots/aarch64-linux-gnu
-- 
2.17.1

[PATCH RFC bpf-next 09/10] arm: include: asm: swab: mask rev16 instruction for clang

[Ivan Khoronzhuk]

The samples/bpf with clang -emit-llvm reuses linux headers to build
bpf samples, and this w/a only for samples (samples/bpf/Makefile
CLANG-bpf).

It allows to build samples/bpf for arm bpf using clang.
In another way clang -emit-llvm generates errors like:

CLANG-bpf  samples/bpf/tc_l2_redirect_kern.o
<inline asm>:1:2: error: invalid register/token name
rev16 r3, r0

This decision is arguable, probably there is another way, but
it doesn't have impact on samples/bpf, so it's easier just ignore
it for clang, at least for now.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
 arch/arm/include/asm/swab.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm/include/asm/swab.h b/arch/arm/include/asm/swab.h
index c6051823048b..a9fd9cd33d5e 100644
--- a/arch/arm/include/asm/swab.h
+++ b/arch/arm/include/asm/swab.h
@@ -25,8 +25,11 @@ static inline __attribute_const__ __u32 __arch_swahb32(__u32 x)
 	__asm__ ("rev16 %0, %1" : "=r" (x) : "r" (x));
 	return x;
 }
+
+#ifndef __clang__
 #define __arch_swahb32 __arch_swahb32
 #define __arch_swab16(x) ((__u16)__arch_swahb32(x))
+#endif
 
 static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
 {
-- 
2.17.1

[PATCH RFC bpf-next 10/10] arm: include: asm: unified: mask .syntax unified for clang

[Ivan Khoronzhuk]

The samples/bpf reuses linux headers, with clang -emit-llvm,
so this w/a is only for samples/bpf (samples/bpf/Makefile CLANG-bpf).

It allows to build samples/bpf for arm on target board.
In another way clang -emit-llvm generates errors like:

<inline asm>:1:1: error: unknown directive
.syntax unified

I have verified it on clang 5, 6 ,7, 8, 9, 10
as on native platform as for cross-compiling. This decision is
arguable, but it doesn't have impact on samples/bpf so it's easier
just ignore it for clang, at least for now...

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
 arch/arm/include/asm/unified.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/unified.h b/arch/arm/include/asm/unified.h
index 1e2c3eb04353..3cf8757b9a14 100644
--- a/arch/arm/include/asm/unified.h
+++ b/arch/arm/include/asm/unified.h
@@ -11,7 +11,11 @@
 #if defined(__ASSEMBLY__)
 	.syntax unified
 #else
-__asm__(".syntax unified");
+
+#ifndef __clang__
+	__asm__(".syntax unified");
+#endif
+
 #endif
 
 #ifdef CONFIG_CPU_V7M
-- 
2.17.1