linux-kernel - Re: [RFC PATCH v2 05/26] tools include: Sync math64.h and div64.h

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Date:	Mon, 27 Jun 2016 15:13:10 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Hekuang <hekuang@...wei.com>
Cc:	Nilay Vaish <nilayvaish@...il.com>, peterz@...radead.org,
	mingo@...hat.com, jolsa@...hat.com, brendan.d.gregg@...il.com,
	ast@...nel.org, alexander.shishkin@...ux.intel.com,
	wangnan0@...wei.com,
	Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v2 05/26] tools include: Sync math64.h and div64.h

Em Mon, Jun 27, 2016 at 10:21:10AM +0800, Hekuang escreveu:
> 在 2016/6/27 5:08, Nilay Vaish 写道:
> > On 26 June 2016 at 06:20, He Kuang <hekuang@...wei.com> wrote:
> > > From: Wang Nan <wangnan0@...wei.com>
> > > This patch copies "include/linux/math64.h" into
> > > "tools/include/linux/math64.h" and copies
> > > "include/asm-generic/div64.h" into
> > > "tools/include/asm-generic/div64.h", to enable other libraries use
> > > arithmetic operation defined in them.
> > This probably is a newbie question.  What prevents us from using the
> > header files directly?
 
> For not being influenced by kernel headers update too much, perf adopts
> the header files in its own folder.

yeah, we used to include them directly, but then, changes in the kernel
sometimes broke the tools/ build, so we instead copy it and check for
changes using diff as part of the build process, flagging changes, like
the one I'm investigating now:

[acme@...et linux]$ diff -u tools/perf/arch/x86/entry/syscalls/syscall_64.tbl arch/x86/entry/syscalls/syscall_64.tbl 
--- tools/perf/arch/x86/entry/syscalls/syscall_64.tbl	2016-06-06 11:06:31.423335774 -0300
+++ arch/x86/entry/syscalls/syscall_64.tbl	2016-06-06 11:06:30.511345336 -0300
@@ -374,3 +374,5 @@
 543	x32	io_setup		compat_sys_io_setup
 544	x32	io_submit		compat_sys_io_submit
 545	x32	execveat		compat_sys_execveat/ptregs
+534	x32	preadv2			compat_sys_preadv2
+535	x32	pwritev2		compat_sys_pwritev2
[acme@...et linux]$

Flagged in the build process:

<SNIP>
...                     get_cpuid: [ on  ]
...                           bpf: [ on  ]

  GEN      /tmp/build/perf/common-cmds.h
Warning: x86_64's syscall_64.tbl differs from kernel
  CC       /tmp/build/perf/fixdep.o
  LD       /tmp/build/perf/fixdep-in
<SNIP>

- Arnaldo