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SubjectRe: [PATCH v2 4/4] perf augmented_raw_syscalls: Document clang configuration
Hi Arnaldo,

On Thu, Jun 06, 2019 at 03:29:41PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Jun 06, 2019 at 10:35:32PM +0800, Leo Yan escreveu:
> > On Thu, Jun 06, 2019 at 11:08:00AM -0300, Arnaldo Carvalho de Melo wrote:
> > > Em Thu, Jun 06, 2019 at 05:48:45PM +0800, Leo Yan escreveu:
> > > > To build this program successfully with clang, there have three
> > > > compiler options need to be specified:
> > > >
> > > > - Header file path: tools/perf/include/bpf;
> > > > - Specify architecture;
> > > > - Define macro __NR_CPUS__.
> > >
> > > So, this shouldn't be needed, all of this is supposed to be done
> > > automagically, have you done a 'make -C tools/perf install'?
> >
> > I missed the up operation. But after git pulled the lastest code base
> > from perf/core branch and used the command 'make -C tools/perf
> > install', I still saw the eBPF build failure.
> >
> > Just now this issue is fixed after I removed the config
> > 'clang-bpf-cmd-template' from ~/.perfconfig; the reason is I followed
> > up the Documentation/perf-config.txt to set the config as below:
> >
> > clang-bpf-cmd-template = "$CLANG_EXEC -D__KERNEL__ $CLANG_OPTIONS \
> > $KERNEL_INC_OPTIONS -Wno-unused-value \
> > -Wno-pointer-sign -working-directory \
> > $WORKING_DIR -c $CLANG_SOURCE -target bpf \
> > -O2 -o -"
> >
> > In fact, util/llvm-utils.c has updated the default configuration as
> > below:
> >
> > #define CLANG_BPF_CMD_DEFAULT_TEMPLATE \
> > "$CLANG_EXEC -D__KERNEL__ -D__NR_CPUS__=$NR_CPUS "\
> > "-DLINUX_VERSION_CODE=$LINUX_VERSION_CODE " \
> > "$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"
> >
> > Maybe should update Documentation/perf-config.txt to tell users the
> > real default value of clang-bpf-cmd-template?
>
> Sure, if you fell like doing this, please update and also please figure
> out when the this changed and add a Fixes: that cset,

Thanks for guidance. Have sent patch for this [1].

> Its great that you're going thru the docs and making sure the
> differences are noted so that we update the docs, thanks a lot!

You are welcome!

Thanks,
Leo Yan

[1] https://lkml.org/lkml/2019/6/7/477

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