Re: [uml-devel] [PATCH 2/2] um: disable compile-time buffer checks

[Richard Weinberger <richard@nod.at>]

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Am Sonntag 12 Juni 2011, 23:52:35 schrieb Florian Fainelli:
> Le dimanche 12 juin 2011 13:56:14, Richard Weinberger a écrit :
> > Am Sonntag 12 Juni 2011, 13:14:41 schrieb Florian Fainelli:
> > > From: Nicolas Thill <nico@openwrt.org>
> > > 
> > > Ubuntu 8.10 and newer enable compile-time buffer checks by default,
> > > 
> > > which can sometime cause build failures like this:
> > >   LD      vmlinux
> > >   SYSMAP  System.map
> > >   SYSMAP  .tmp_System.map
> > >   LINK linux
> > >   Building modules, stage 2.
> > >   MODPOST 51 modules
> > > 
> > > ERROR: "__sprintf_chk" [arch/um/drivers/harddog.ko] undefined!
> > 
> > Hmm, now I'm wondering why no other Ubuntu users have noticed this.
> > Are also current versions of Ubuntu affected?
> 
> Without this patch, I get the exact same modpost error on Ubuntu 11.04:

Okay, found the real problem.
We have to export the *_chk functions.
Nobody noticed it because most UML kernels are CONFIG_MODULES=n
and harddog.ko is not part of the defaultconfig.

Can you please test the attached patch?

Thanks,
//richard

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diff --git a/arch/um/os-Linux/user_syms.c b/arch/um/os-Linux/user_syms.c
index 05f5ea8..9e71e7e 100644
--- a/arch/um/os-Linux/user_syms.c
+++ b/arch/um/os-Linux/user_syms.c
@@ -18,6 +18,9 @@ extern void *memmove(void *, const void *, size_t);
 extern void *memset(void *, int, size_t);
 extern int printf(const char *, ...);
 
+extern int __sprintf_chk(char *str, int flag, size_t strlen, const char *format);
+EXPORT_SYMBOL(__sprintf_chk);
+
 /* If it's not defined, the export is included in lib/string.c.*/
 #ifdef __HAVE_ARCH_STRSTR
 EXPORT_SYMBOL(strstr);

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