linux-kernel - Re: [PATCH 15/20] objtool: Add --backtrace support

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Date:   Fri, 8 Mar 2019 13:33:05 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     torvalds@...ux-foundation.org, tglx@...utronix.de, hpa@...or.com,
        julien.thierry@....com, will.deacon@....com, luto@...capital.net,
        mingo@...nel.org, catalin.marinas@....com, james.morse@....com,
        valentin.schneider@....com, brgerst@...il.com, luto@...nel.org,
        bp@...en8.de, dvlasenk@...hat.com, linux-kernel@...r.kernel.org,
        dvyukov@...gle.com, rostedt@...dmis.org
Subject: Re: [PATCH 15/20] objtool: Add --backtrace support

On Thu, Mar 07, 2019 at 12:45:26PM +0100, Peter Zijlstra wrote:
> For when you want to know the path that reached your fail state.
> 
> $ ./objtool check --no-fp --backtrace arch/x86/lib/usercopy_64.o
> arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0x3: UACCESS disable without MEMOPs: __clear_user()
> arch/x86/lib/usercopy_64.o: warning: objtool:   __clear_user()+0x3a: (alt)
> arch/x86/lib/usercopy_64.o: warning: objtool:   __clear_user()+0x2e: (branch)
> arch/x86/lib/usercopy_64.o: warning: objtool:   __clear_user()+0x18: (branch)
> arch/x86/lib/usercopy_64.o: warning: objtool:   .altinstr_replacement+0xffffffffffffffff: (branch)
> arch/x86/lib/usercopy_64.o: warning: objtool:   __clear_user()+0x5: (alt)
> arch/x86/lib/usercopy_64.o: warning: objtool:   __clear_user()+0x0: <=== (func)

We should have done this a long time ago.  Thank you for this!

-- 
Josh