linux-kernel - Re: [GIT PULL] x86/kaslr for v3.14

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Date:	Wed, 29 Jan 2014 07:36:01 +0100
From:	Mike Galbraith <bitbucket@...ine.de>
To:	Dave Jones <davej@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Richard Weinberger <richard@....at>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Kees Cook <keescook@...omium.org>,
	Cong Ding <dinggnu@...il.com>, Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Mathias Krause <minipli@...glemail.com>,
	Michael Davidson <md@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Wei Yongjun <yongjun_wei@...ndmicro.com.cn>
Subject: Re: [GIT PULL] x86/kaslr for v3.14

On Tue, 2014-01-28 at 16:08 -0500, Dave Jones wrote: 
> On Tue, Jan 28, 2014 at 12:25:15PM -0800, Linus Torvalds wrote:
>  > On Tue, Jan 28, 2014 at 12:15 PM, Borislav Petkov <bp@...en8.de> wrote:
>  > >
>  > > Shouldn't we hold that down in the Kconfig help text of DEBUG_INFO?
>  > > Something like:
>  > >
>  > > "You don't need to enable this if you want symbolic names for kernel
>  > > objects. Enable CONFIG_KALLSYMS instead."
>  > 
>  > Probably. And then we should make sure that allyesconfig/allmodconfig
>  > don't pick it.
>  > 
>  > There *are* reasonable uses for DEBUG_INFO:
>  > 
>  >  - if you very actively and extensively use kgdb, DEBUG_INFO is very useful.
>  > 
>  >  - distros might want to build distro kernels with DEBUG_INFO for the
>  > kernel debug package
> 
> - objdump -S is kind of useful. I find myself using that quite often.
>   (like at least a dozen times each merge window)

For those with wimpy asm muscles (/me), it's very useful indeed, as are
gdb list *foo()+0x10 or *0xfeedbabedeadbeef.  I always build with full
DEBUG_INFO, just keep configs lean enough that lots of kernels fit in a
2G /boot, and _never ever_ set a box up with a microscopic root.

> pretty sure it works with DEBUG_INFO_REDUCED though, which is somewhat
> faster than full DEBUG_INFO

Yeah, it does.

-Mike

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