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From: Steven Rostedt <rostedt@goodmis.org>
To: changbin.du@intel.com
Cc: yamada.masahiro@socionext.com, michal.lkml@markovi.net,
	tglx@linutronix.de, mingo@redhat.com, akpm@linux-foundation.org,
	rdunlap@infradead.org, x86@kernel.org, lgirdwood@gmail.com,
	broonie@kernel.org, arnd@arndb.de, linux-kbuild@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH v2 5/5] asm-generic: fix build error in fix_to_virt with CONFIG_DEBUG_EXPERIENCE
Date: Wed, 2 May 2018 10:19:30 -0400	[thread overview]
Message-ID: <20180502101930.25a5437d@gandalf.local.home> (raw)
In-Reply-To: <1525268700-10631-6-git-send-email-changbin.du@intel.com>

On Wed,  2 May 2018 21:45:00 +0800
changbin.du@intel.com wrote:

> From: Changbin Du <changbin.du@intel.com>
> 
> With '-Og' optimization level, GCC would not optimize a count for a loop
> as a constant value. But BUILD_BUG_ON() only accept compile-time constant
> values.
> 
> arch/arm/mm/mmu.o: In function `fix_to_virt':
> /home/changbin/work/linux/./include/asm-generic/fixmap.h:31: undefined reference to `__compiletime_assert_31'
> Makefile:1051: recipe for target 'vmlinux' failed
> make: *** [vmlinux] Error 1
> 
> Signed-off-by: Changbin Du <changbin.du@intel.com>
> ---
>  include/asm-generic/fixmap.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h
> index 827e4d3..a6576d4 100644
> --- a/include/asm-generic/fixmap.h
> +++ b/include/asm-generic/fixmap.h
> @@ -28,7 +28,8 @@
>   */
>  static __always_inline unsigned long fix_to_virt(const unsigned int idx)
>  {
> -	BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
> +	BUILD_BUG_ON(__builtin_constant_p(idx) &&
> +		     idx >= __end_of_fixed_addresses);

Hmm, this changes the check slightly. Perhaps we should only do this
when your config is active:

{
	BUILD_BUG_ON(
/* CONFIG_DEBUG_OPTIMIZE may cause idx not to be constant */
#ifdef CONFIG_DEBUG_OPTIMIZE
		__builtin_constant_p(idx) &&
#endif
		idx >= __end_of_fixed_addresses);

}

-- Steve

>  	return __fix_to_virt(idx);
>  }
>  

  reply	other threads:[~2018-05-02 14:19 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-02 13:44 [PATCH v2 0/5] kernel hacking: GCC optimization for debug experience (-Og) changbin.du
2018-05-02 13:44 ` [PATCH v2 1/5] x86/mm: surround level4_kernel_pgt with #ifdef CONFIG_X86_5LEVEL...#endif changbin.du
2018-05-02 13:44 ` [PATCH v2 2/5] regulator: add dummy function of_find_regulator_by_node changbin.du
2018-05-02 13:44 ` [PATCH v2 3/5] kernel hacking: new config NO_AUTO_INLINE to disable compiler auto-inline optimizations changbin.du
2018-05-02 14:07   ` Steven Rostedt
2018-05-02 20:27   ` Arnd Bergmann
2018-05-03 13:00     ` Du, Changbin
2018-05-03 14:16       ` Steven Rostedt
2018-05-02 13:44 ` [PATCH v2 4/5] kernel hacking: new config DEBUG_EXPERIENCE to apply GCC -Og optimization changbin.du
2018-05-02 14:17   ` Steven Rostedt
2018-05-02 20:45     ` Andrew Morton
2018-05-03  1:19       ` Steven Rostedt
2018-05-03 13:45         ` Du, Changbin
2018-05-03 14:28           ` Steven Rostedt
2018-05-05 23:57             ` Du, Changbin
2018-05-06  0:27               ` Randy Dunlap
2018-05-02 19:26   ` Randy Dunlap
2018-05-02 13:45 ` [PATCH v2 5/5] asm-generic: fix build error in fix_to_virt with CONFIG_DEBUG_EXPERIENCE changbin.du
2018-05-02 14:19   ` Steven Rostedt [this message]
2018-05-03 13:25     ` Du, Changbin
2018-05-03 14:19       ` Steven Rostedt
2018-05-03 16:39         ` weylin
2018-05-02 14:56 ` [PATCH v2 0/5] kernel hacking: GCC optimization for debug experience (-Og) Daniel Thompson
2018-05-03 13:49   ` Du, Changbin

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