linux-kernel - Re: [PATCH v1.1] x86/mm/ASLR: Propagate ASLR status to kernel proper

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Date:	Thu, 2 Apr 2015 13:07:13 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>, x86-ml <x86@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v1.1] x86/mm/ASLR: Propagate ASLR status to kernel proper


* Borislav Petkov <bp@...en8.de> wrote:

> --- a/arch/x86/kernel/module.c
> +++ b/arch/x86/kernel/module.c
> @@ -33,6 +33,7 @@
>  
>  #include <asm/page.h>
>  #include <asm/pgtable.h>
> +#include <asm/setup.h>
>  
>  #if 0
>  #define DEBUGP(fmt, ...)				\
> @@ -47,21 +48,13 @@ do {							\
>  
>  #ifdef CONFIG_RANDOMIZE_BASE
>  static unsigned long module_load_offset;
> -static int randomize_modules = 1;
>  
>  /* Mutex protects the module_load_offset. */
>  static DEFINE_MUTEX(module_kaslr_mutex);
>  
> -static int __init parse_nokaslr(char *p)
> -{
> -	randomize_modules = 0;
> -	return 0;
> -}
> -early_param("nokaslr", parse_nokaslr);

So doesn't a 'nokaslr' boot option still make sense, to be able to 
debug KASLR failures and such?

> +	if (kaslr_enabled())
> +		pr_emerg("Kernel Offset: 0x%lx from 0x%lx (relocation range: 0x%lx-0x%lx)\n",
> +			 (unsigned long)&_text - __START_KERNEL,
> +			 __START_KERNEL,
> +			 __START_KERNEL_map,
> +			 MODULES_VADDR-1);
> +	else
> +		pr_emerg("Kernel Offset: disabled\n");

Nit: curly braces for multi-line statements and so.

Thanks,

	Ingo
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