linux-kernel - Re: [PATCH bpf-next v1 2/2] selftests/bpf: Fix cross-compile issue for some files and a static compile issue for "-lzstd"

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Message-ID: <72d7f850-2143-4287-b2cf-96da367b8941@vivo.com>
Date: Wed, 28 Aug 2024 17:54:51 +0800
From: Yikai Lin <yikai.lin@...o.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
 <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>,
 Shuah Khan <shuah@...nel.org>, Nick Terrell <terrelln@...com>,
 bpf@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, opensource.kernel@...o.com,
 Yikai Lin <yikai.lin@...o.com>
Subject: Re: [PATCH bpf-next v1 2/2] selftests/bpf: Fix cross-compile issue
 for some files and a static compile issue for "-lzstd"

On 2024/8/28 06:49:18, Lin Yikai reply:

> [Some people who received this message don't often get email from andrii.nakryiko@...il.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> On Tue, Aug 27, 2024 at 6:40 AM Lin Yikai <yikai.lin@...o.com> wrote:
>>
>> 1. Fix cross-compile issue for some files:
>> [Issue]
>> When cross-compiling bpf selftests for arm64 on x86_64 host, the following error occurs:
>> progs/loop2.c:20:7: error: incomplete definition of type 'struct user_pt_regs'
>>     20 |                 if (PT_REGS_RC(ctx) & 1)
>>        |                     ^~~~~~~~~~~~~~~
>>
>> There are same error in files: loop1.c, loop2.c, loop3.c, loop6.c ???
>>
>> [Reason]
>> On arm64, in file bpf_tracing.h, we use userspace's user_pt_regs,
>> which is defined in "linux/ptrace.h".
>> We include the header file by adding "-idirafter /usr/include" for "CLANG_CFLAGS".
>>
>> However, during cross-compiling, "linux/ptrace.h" is based on x86_64
>> and has no definition of "struct user_pt_regs".
>>
>> [Fix]
>> Thus, to fix this issue, we include the Linux source tree's header file directory.
>>
> 
> Hm.. Not sure that's the right fix. Note -D__TARGET_ARCH_$(SRCARCH) in
> BPF_CFLAGS, that __TARGET_ARCH has to match actual target
> architecture, so please check that first.
> 

Hi, Andrii, thanks for your advice.

After searching, I find needed "user_pt_regs" is defined as below:
   bpf-next$ find ./ -name "ptrace.h" | xargs grep -rni "user_pt_regs"
   ./arch/arm64/include/uapi/asm/ptrace.h:88:struct user_pt_regs {

So we can directly add it into include directory
by below approach without "make header_install".

   +ifneq ($(CROSS_COMPILE),)
   +src_uapi_dir := $(srctree)/arch/$(SRCARCH)/include/uapi
   +BPF_CFLAGS += -I$(src_uapi_dir)
   +endif

I'll test it and send a v2 patch.

> pw-bot: cr
> 
>> 2. Fix static compile issue for "-lzstd":
>> [Issue]
>> By running the command "LDLIBS=-static LDFLAGS=--sysroot=/aarch64-linux-gnu/libc ./vmtest.sh -s -- ./test_progs",
>> during static cross-compiling, an error occurs:
>> /aarch64-linux-gnu/bin/ld: aarch64-linux-gnu/libc/usr/lib/libelf.a(elf_compress.o): in function `__libelf_compress':
>> (.text+0xec): undefined reference to `ZSTD_createCCtx'
>> /aarch64-linux-gnu/bin/ld: (.text+0xf0): undefined reference to `ZSTD_createCCtx'
>> ...
>>
>> [Fix]
>> For static compile, add "LDLIBS += -lzstd".
> 
> we can probably just add it unconditionally, no? But please send it as
> a separate change in its own patch
> 
Thanks, I'll try it for v2 patch.

>>
>> Signed-off-by: Lin Yikai <yikai.lin@...o.com>
>> ---
>>   tools/testing/selftests/bpf/Makefile | 12 +++++++++++-
>>   1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
>> index ec7d425c4022..5b725bc890d2 100644
>> --- a/tools/testing/selftests/bpf/Makefile
>> +++ b/tools/testing/selftests/bpf/Makefile
>> @@ -48,6 +48,10 @@ CFLAGS += -g $(OPT_FLAGS) -rdynamic                                  \
>>   LDFLAGS += $(SAN_LDFLAGS)
>>   LDLIBS += $(LIBELF_LIBS) -lz -lrt -lpthread
>>
>> +ifneq (,$(findstring -static,$(LDLIBS)))
>> +LDLIBS += -lzstd
>> +endif
>> +
>>   LDLIBS += $(shell $(PKG_CONFIG) --libs libpcap 2>/dev/null)
>>   CFLAGS += $(shell $(PKG_CONFIG) --cflags libpcap 2>/dev/null)
>>   CFLAGS += $(shell $(PKG_CONFIG) --exists libpcap 2>/dev/null && echo "-DTRAFFIC_MONITOR=1")
>> @@ -443,13 +447,19 @@ CLANG_TARGET_ARCH = --target=$(notdir $(CROSS_COMPILE:%-=%))
>>   endif
>>
>>   CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
>> +CLANG_CFLAGS = $(CLANG_SYS_INCLUDES)
>> +
>>   BPF_CFLAGS = -g -Wall -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN)    \
>>               -I$(INCLUDE_DIR) -I$(CURDIR) -I$(APIDIR)                   \
>>               -I$(abspath $(OUTPUT)/../usr/include)                      \
>>               -Wno-compare-distinct-pointer-types
>>   # TODO: enable me -Wsign-compare
>>
>> -CLANG_CFLAGS = $(CLANG_SYS_INCLUDES)
>> +#"make headers_install" at first
>> +ifneq ($(CROSS_COMPILE),)
>> +src_uapi_dir := $(srctree)/usr/include
>> +BPF_CFLAGS += -I$(src_uapi_dir)
>> +endif
>>
>>   $(OUTPUT)/test_l4lb_noinline.o: BPF_CFLAGS += -fno-inline
>>   $(OUTPUT)/test_xdp_noinline.o: BPF_CFLAGS += -fno-inline
>> --
>> 2.34.1
>>