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From: Seth Forshee <seth.forshee@canonical.com>
To: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	netdev@vger.kernel.org, bpf@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: resolve_btfids breaks kernel cross-compilation
Date: Wed, 16 Sep 2020 14:47:33 -0500	[thread overview]
Message-ID: <20200916194733.GA4820@ubuntu-x1> (raw)

The requirement to build resolve_btfids whenever CONFIG_DEBUG_INFO_BTF
is enabled breaks some cross builds. For example, when building a 64-bit
powerpc kernel on amd64 I get:

 Auto-detecting system features:
 ...                        libelf: [ [32mon[m  ]
 ...                          zlib: [ [32mon[m  ]
 ...                           bpf: [ [31mOFF[m ]
 
 BPF API too old
 make[6]: *** [Makefile:295: bpfdep] Error 1

The contents of tools/bpf/resolve_btfids/feature/test-bpf.make.output:

 In file included from /home/sforshee/src/u-k/unstable/tools/arch/powerpc/include/uapi/asm/bitsperlong.h:11,
                  from /usr/include/asm-generic/int-ll64.h:12,
                  from /usr/include/asm-generic/types.h:7,
                  from /usr/include/x86_64-linux-gnu/asm/types.h:1,
                  from /home/sforshee/src/u-k/unstable/tools/include/linux/types.h:10,
                  from /home/sforshee/src/u-k/unstable/tools/include/uapi/linux/bpf.h:11,
                  from test-bpf.c:3:
 /home/sforshee/src/u-k/unstable/tools/include/asm-generic/bitsperlong.h:14:2: error: #error Inconsistent word size. Check asm/bitsperlong.h
    14 | #error Inconsistent word size. Check asm/bitsperlong.h
       |  ^~~~~

This is because tools/arch/powerpc/include/uapi/asm/bitsperlong.h sets
__BITS_PER_LONG based on the predefinied compiler macro __powerpc64__,
which is not defined by the host compiler. What can we do to get cross
builds working again?

Thanks,
Seth

             reply	other threads:[~2020-09-16 19:51 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-16 19:47 Seth Forshee [this message]
2020-09-17  8:04 ` resolve_btfids breaks kernel cross-compilation Jiri Olsa
2020-09-17  8:38   ` Jiri Olsa
2020-09-17  9:14     ` Jiri Olsa
2020-09-17  9:54       ` Jiri Olsa
2020-09-17 12:54       ` Seth Forshee
2020-09-18 10:05         ` Jiri Olsa
2020-09-18 18:50           ` Andrii Nakryiko

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