linux-kernel - Re: [RESEND][patch V3 06/23] bug: Annotate WARN/BUG/stackfail as noinstr safe

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Date:   Thu, 02 Apr 2020 23:49:08 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Paul McKenney <paulmck@...nel.org>,
        "Joel Fernandes \(Google\)" <joel@...lfernandes.org>,
        "Steven Rostedt \(VMware\)" <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Brian Gerst <brgerst@...il.com>,
        Juergen Gross <jgross@...e.com>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Subject: Re: [RESEND][patch V3 06/23] bug: Annotate WARN/BUG/stackfail as noinstr safe

Josh Poimboeuf <jpoimboe@...hat.com> writes:
> On Fri, Mar 20, 2020 at 07:00:02PM +0100, Thomas Gleixner wrote:
>> --- a/arch/x86/include/asm/bug.h
>> +++ b/arch/x86/include/asm/bug.h
>> @@ -70,13 +70,16 @@ do {									\
>>  #define HAVE_ARCH_BUG
>>  #define BUG()							\
>>  do {								\
>> +	instr_begin();						\
>>  	_BUG_FLAGS(ASM_UD2, 0);					\
>>  	unreachable();						\
>>  } while (0)
>
> For visual symmetry at least, it seems like this wants an instr_end()
> before the unreachable().  Does objtool not like that?

There was some hickup, but can't remember. Will try to reproduce with
the latest version of Peter's objtool changes.

>> --- a/include/asm-generic/bug.h
>> +++ b/include/asm-generic/bug.h
>> @@ -83,14 +83,19 @@ extern __printf(4, 5)
>>  void warn_slowpath_fmt(const char *file, const int line, unsigned taint,
>>  		       const char *fmt, ...);
>>  #define __WARN()		__WARN_printf(TAINT_WARN, NULL)
>> -#define __WARN_printf(taint, arg...)					\
>> -	warn_slowpath_fmt(__FILE__, __LINE__, taint, arg)
>> +#define __WARN_printf(taint, arg...) do {				\
>> +	instr_begin();							\
>> +	warn_slowpath_fmt(__FILE__, __LINE__, taint, arg);		\
>> +	instr_end();							\
>> +	while (0)
>
> Missing a '}' before the 'while'?

Yep, fixed that locally already.

Thanks,

        tglx