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

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Date: Tue, 9 Jan 2024 21:49:10 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Tanzir Hasan <tanzhasanwork@...il.com>
Cc: Kees Cook <keescook@...omium.org>, 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

Hi,

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.

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>
> 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