linux-hardening - Re: [PATCH v2 2/2] lib/string: shrink lib/string.i via IWYU

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Date: Wed, 10 Jan 2024 16:07:41 -0800
From: Kees Cook <keescook@...omium.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Tanzir Hasan <tanzhasanwork@...il.com>,
	Andy Shevchenko <andy@...nel.org>, linux-hardening@...r.kernel.org,
	linux-kernel@...r.kernel.org, Nick DeSaulniers <nnn@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>, llvm@...ts.linux.dev
Subject: Re: [PATCH v2 2/2] lib/string: shrink lib/string.i via IWYU

On Tue, Jan 09, 2024 at 09:49:10PM +0000, Justin Stitt wrote:
> On Thu, Dec 14, 2023 at 09:06:13PM +0000, tanzirh@...gle.com wrote:
> > This diff uses an open source tool include-what-you-use (IWYU) to modify
> > the include list changing indirect includes to direct includes.
> > IWYU is implemented using the IWYUScripts github repository which is a tool that is
> > currently undergoing development. These changes seek to improve build times.
> >
> > This change to lib/string.c resulted in a preprocessed size of
> > lib/string.i from 26371 lines to 5259 lines (-80%) for the x86
> > defconfig.
> >
> 
> Tanzir, I wonder if you could include some of the symbol names used for
> some of these more esoteric headers. Let me describe what I mean:
> 
> Andy talks about "why <vdso/...>" and perhaps some comments (in your
> patch message, not in the source itself) about which symbols are being
> used from these headers would serve useful. I believe IWYU can generate
> this information and should clear up some confusion or lead to better
> suggestions from reviewers if we understand why a header is being
> included.

If there aren't any other objections, I'd like to pick this up in my
tree after the merge window closes.

> 
> At any rate, this builds for me doing randconfigs on x86_64 with these
> KCONFIG_SEEDs
> 1: 0x3DD9D136
> 2: 0xB4440EE4
> 3: 0x98778270
> 4: 0x8C237F26
> 5: 0x244F8A64
> 6: 0x5A5C5E5C
> 7: 0xA77896BC
> 8: 0x9B5FF0D5
> 9: 0x24F23F6A
> 10: 0x35C0A107
> 
> I applied your patch on top of 5db8752c3b81bd33.
> 
> Tested-by: Justin Stitt <justinstitt@...gle.com>

Thanks for the testing!

-Kees

> > Link: https://github.com/ClangBuiltLinux/IWYUScripts
> >
> > Signed-off-by: Tanzir Hasan <tanzirh@...gle.com>
> > ---
> >  lib/string.c | 14 +++++++-------
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> >
> > diff --git a/lib/string.c b/lib/string.c
> > index be26623953d2..7fe1acefb1a1 100644
> > --- a/lib/string.c
> > +++ b/lib/string.c
> > @@ -16,16 +16,16 @@
> >
> >  #define __NO_FORTIFY
> >  #include <linux/types.h>
> > -#include <linux/string.h>
> > -#include <linux/ctype.h>
> > -#include <linux/kernel.h>
> > -#include <linux/export.h>
> > +#include <linux/bits.h>
> >  #include <linux/bug.h>
> >  #include <linux/errno.h>
> > -#include <linux/slab.h>
> > -
> > +#include <asm/rwonce.h>
> > +#include <linux/linkage.h>
> > +#include <linux/stddef.h>
> > +#include <vdso/limits.h>
> > +#include <linux/string.h>
> > +#include <linux/ctype.h>
> >  #include <asm/unaligned.h>
> > -#include <asm/byteorder.h>
> >  #include <asm/word-at-a-time.h>
> >  #include <asm/page.h>
> >
> >
> > --
> > 2.43.0.472.g3155946c3a-goog
> >
> Thanks
> Justin

-- 
Kees Cook