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: <CAEf4BzZXL9=pOkt=GbrYG2DpDGtXNLS7AHH5rL3adHd50zMKmQ@mail.gmail.com>
Date: Tue, 27 Aug 2024 15:49:18 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Lin Yikai <yikai.lin@...o.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
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 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.

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

>
> 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
>