linux-kernel - Re: [PATCH] uprobes/core: handle breakpoint and signal step exception.

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Date:	Thu, 8 Mar 2012 18:48:24 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Anton Arapov <anton@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Jiri Olsa <jolsa@...hat.com>, Josh Stone <jistone@...hat.com>
Subject: Re: [PATCH] uprobes/core: handle breakpoint and signal step
 exception.

> >  
> >  #include <linux/kdebug.h>
> >  #include <asm/insn.h>
> >  
> > +#ifdef CONFIG_X86_32
> > +#define is_32bit_app(tsk) 1
> > +#else
> > +#define is_32bit_app(tsk) (test_tsk_thread_flag(tsk, TIF_IA32))
> > +#endif
> 
> Small detail, we prefer to use this variant:
> 
> #ifdef X
> # define foo()
> #else
> # define bar()
> #endif
> 
> to give the construct more visual structure.
> 
> Also, please put it into asm/compat.h and use it at other places 
> within arch/x86/ as well, there's half a dozen similar patterns 
> of TIP_IA32 tests in arch/x86/. Please make this a separate 
> patch, preceding this patch.

I am facing a problem doing the above.
I did some changes in arch/x86/kernel/signal.c and included compat.h 
and compilation fails on tip tree that the commit 
d1a797f388

In file included from ../arch/x86/kernel/signal.c:42:
../arch/x86/include/asm/compat.h: In function âarch_compat_alloc_user_spaceâ:
../arch/x86/include/asm/compat.h:238: error: âold_rspâ undeclared (first use in this function)
../arch/x86/include/asm/compat.h:238: error: (Each undeclared identifier is reported only once
../arch/x86/include/asm/compat.h:238: error: for each function it appears in.)
../arch/x86/include/asm/compat.h:238: warning: type defaults to âintâ in declaration of âpfo_ret__â            


I see old_rsp declared only under CONFIG_X86_64 in asm/processor.h 

The below helps resolve the problem.
---------
diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index 9c9b6dc..147e790 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -233,9 +233,11 @@ static inline void __user *arch_compat_alloc_user_space(long len)
 
 	if (test_thread_flag(TIF_IA32)) {
 		sp = task_pt_regs(current)->sp;
+#ifdef CONFIG_X86_64
 	} else {
 		/* -128 for the x32 ABI redzone */
 		sp = __this_cpu_read(old_rsp) - 128;
+#endif
 	}
 
 	return (void __user *)round_down(sp - len, 16);


-----------

But I wanted to check if there is any reason why we cant include asm/compat.h in arch/x86/kernel/signal.c.

-- 
Thanks and Regards
Srikar

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