From: gang.chen@asianux•com (Chen Gang)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] arch: configuration, deleting 'CONFIG_BUG' since always need it.
Date: Fri, 24 May 2013 10:13:35 +0800 [thread overview]
Message-ID: <519ECCCF.8090909@asianux.com> (raw)
In-Reply-To: <CAMuHMdUzcBuDupe4Fa6XieziGPMpPKC_k8X8gUUmDvLJ+Fe=Hg@mail.gmail.com>
On 05/23/2013 10:10 PM, Geert Uytterhoeven wrote:
> On Thu, May 23, 2013 at 2:50 PM, Russell King - ARM Linux
> <linux@arm•linux.org.uk> wrote:
>> > On Thu, May 23, 2013 at 02:09:02PM +0200, Arnd Bergmann wrote:
>>> >> On Thursday 23 May 2013, Russell King - ARM Linux wrote:
>>>> >> > This is the problem you guys are missing - unreachable() means "we lose
>>>> >> > control of the CPU at this point".
>>> >>
>>> >> I'm absolutely aware of this. Again, the current behaviour of doing nothing
>>> >> at all isn't very different from undefined behavior when you get when you
>>> >> get to the end of a function returning a pointer without a "return" statement,
>>> >> or when you return from a function that has determined that it is not safe
>>> >> to continue.
>> >
>> > Running off the end of a function like that is a different kettle of fish.
>> > The execution path is still as the compiler intends - what isn't is that
>> > the data returned is likely to be random trash.
>> >
>> > That's _quite_ different from the CPU starting to execute the contents
>> > of a literal data pool.
> I agree it's best to e.g. trap and reboot.
After read the arch/*/include/asm/bug.h,
It seems panic() is not suitable for NOMMU platforms (only m68k use it,
also need CONFIG_BUG and CONFIG_SUN3 enabled).
And unreachable() is need followed with an asm inline instruction (arm,
x86, powerpc mips...).
And __builtin_trap() is "the mechanism used may vary from release to
release so should not rely on any particular implementation" (ref to
"http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html", used by m68k,
sparc, ia64).
I can not find any *trap*() and *unreachable*() in "include/asm-generic/"
I can not find any suitable implementation which 'generic' enough to add
in "include/asm-generic/" (and in fact, CONFIG_BUG itself is not
'generic' enough to be in "include/asm-generic/").
At last, I still suggest to delete CONFIG_BUG, so most of architectures
can skip this issue firstly.
Then for specific architectures, also can get 3 benefits:
a. the related maintainers can implement it as their own willing (not
need discus it with another platform maintainers again);
b. the related maintainers can free use the platform specific features
(which can not be used in "include/asm-generic/");
c. the related maintainers are more familiar their own architectures
demands and requirements.
----------- arch/m68k/include/asm/bug.h --------------------------------
1 #ifndef _M68K_BUG_H
2 #define _M68K_BUG_H
3
4 #ifdef CONFIG_MMU
5 #ifdef CONFIG_BUG
6 #ifdef CONFIG_DEBUG_BUGVERBOSE
7 #ifndef CONFIG_SUN3
8 #define BUG() do { \
9 printk("kernel BUG at %s:%d!\n", __FILE__, __LINE__); \
10 __builtin_trap(); \
11 } while (0)
12 #else
13 #define BUG() do { \
14 printk("kernel BUG at %s:%d!\n", __FILE__, __LINE__); \
15 panic("BUG!"); \
16 } while (0)
17 #endif
18 #else
19 #define BUG() do { \
20 __builtin_trap(); \
21 } while (0)
22 #endif
23
24 #define HAVE_ARCH_BUG
25 #endif
26 #endif /* CONFIG_MMU */
27
28 #include <asm-generic/bug.h>
29
30 #endif
Thanks.
--
Chen Gang
Asianux Corporation
next prev parent reply other threads:[~2013-05-24 2:13 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-23 7:57 [PATCH] arch: configuration, deleting 'CONFIG_BUG' since always need it Chen Gang
2013-05-23 8:40 ` Geert Uytterhoeven
2013-05-23 8:54 ` Arnd Bergmann
2013-05-23 9:05 ` Russell King - ARM Linux
2013-05-23 9:12 ` Geert Uytterhoeven
2013-05-23 9:39 ` Arnd Bergmann
2013-05-23 10:04 ` Russell King - ARM Linux
2013-05-23 10:41 ` Chen Gang
2013-05-23 10:59 ` Arnd Bergmann
2013-05-23 11:19 ` Chen Gang
2013-05-23 11:24 ` Russell King - ARM Linux
2013-05-23 12:09 ` Arnd Bergmann
2013-05-23 12:50 ` Russell King - ARM Linux
2013-05-23 14:10 ` Geert Uytterhoeven
2013-05-24 2:13 ` Chen Gang [this message]
2013-05-24 4:17 ` Chen Gang
2013-05-26 4:43 ` [PATCH v2] arch: configuration issue, random return value when disable 'CONFIG_BUG' Chen Gang
2013-05-28 8:19 ` [PATCH] arch: configuration, deleting 'CONFIG_BUG' since always need it Ingo Molnar
2013-05-28 10:25 ` Chen Gang
2013-05-28 14:49 ` Arnd Bergmann
2013-05-28 14:55 ` H. Peter Anvin
2013-05-28 15:43 ` Arnd Bergmann
2013-05-28 16:06 ` H. Peter Anvin
2013-05-28 17:20 ` Arnd Bergmann
2013-05-23 10:09 ` Eric W. Biederman
2013-05-23 10:29 ` Russell King - ARM Linux
2013-05-23 10:05 ` Chen Gang
2013-05-24 5:59 ` Eric W. Biederman
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