linux-kernel - Re: [PATCH -next] x86/mm: fix an unused variable "tsk" warning

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Message-ID: <20190612175543.GO32652@zn.tnic>
Date:   Wed, 12 Jun 2019 19:55:43 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Qian Cai <cai@....pw>, "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     mingo@...hat.com, tglx@...utronix.de, dave.hansen@...ux.intel.com,
        luto@...nel.org, peterz@...radead.org, hpa@...or.com,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] x86/mm: fix an unused variable "tsk" warning

On Fri, May 31, 2019 at 05:37:21PM -0400, Qian Cai wrote:
> Since the commit "signal: Remove the task parameter from
> force_sig_fault", "tsk" is only used when MEMORY_FAILURE=y and generates
> a compilation warning without it.
> 
> arch/x86/mm/fault.c: In function 'do_sigbus':
> arch/x86/mm/fault.c:1017:22: warning: unused variable 'tsk'
> [-Wunused-variable]
> 
> Also, change to use IS_ENABLED() instead.
> 
> Signed-off-by: Qian Cai <cai@....pw>
> ---
>  arch/x86/mm/fault.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 46ac96aa7c81..40d70bd3fa84 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -1014,8 +1014,6 @@ static inline bool bad_area_access_from_pkeys(unsigned long error_code,
>  do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
>  	  vm_fault_t fault)
>  {
> -	struct task_struct *tsk = current;
> -
>  	/* Kernel mode? Handle exceptions or die: */
>  	if (!(error_code & X86_PF_USER)) {
>  		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
> @@ -1028,9 +1026,10 @@ static inline bool bad_area_access_from_pkeys(unsigned long error_code,
>  
>  	set_signal_archinfo(address, error_code);
>  
> -#ifdef CONFIG_MEMORY_FAILURE
> -	if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
> +	if (IS_ENABLED(CONFIG_MEMORY_FAILURE) &&
> +	    (fault & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))) {
>  		unsigned lsb = 0;
> +		struct task_struct *tsk = current;
>  
>  		pr_err(
>  	"MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
> @@ -1042,7 +1041,6 @@ static inline bool bad_area_access_from_pkeys(unsigned long error_code,
>  		force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
>  		return;
>  	}
> -#endif
>  	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
>  }
>  
> -- 

I was puzzled just like Dave because this code is not in tip.

Turns out there's this in linux-next:

commit 318759b4737c3b3789e2fd64d539f437d52386f5
Author: Eric W. Biederman <ebiederm@...ssion.com>
Date:   Mon Jun 3 10:23:58 2019 -0500

    signal/x86: Move tsk inside of CONFIG_MEMORY_FAILURE in do_sigbus


-- 
Regards/Gruss,
    Boris.

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