linux-kernel - Re: [RFC PATCH liburing v1 3/3] src/Makefile: Allow using stack protector with libc

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Date:   Thu, 22 Jun 2023 19:57:38 +0200
From:   Thomas Weißschuh <thomas@...ch.de>
To:     Ammar Faizi <ammarfaizi2@...weeb.org>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Alviro Iskandar Setiawan <alviro.iskandar@...weeb.org>,
        Guillem Jover <guillem@...rons.org>,
        Jeff Moyer <jmoyer@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Michael William Jonathan <moe@...weeb.org>,
        Matthew Patrick <ThePhoenix576@...weeb.org>,
        io-uring Mailing List <io-uring@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>
Subject: Re: [RFC PATCH liburing v1 3/3] src/Makefile: Allow using stack
 protector with libc

On 2023-06-23 00:20:29+0700, Ammar Faizi wrote:
> Currently, the stack protector is forcefully disabled. Let's allow using
> the stack protector feature only if libc is used.
> 
> The stack protector will remain disabled by default if no custom CFLAGS
> are provided. This ensures the default behavior doesn't change while
> still offering the option to enable the stack protector.

FYI

There are patches in the pipeline that enable stackprotector support for
nolibc [0]. They should land in 6.5.

It only supports "global" mode and not per-thread-data.
But as nolibc does not support threads anyways that should not matter.
A compiler flag has to be passed though, but that can be automated [1].

So the -fno-stack-protector can probably be removed completely.

[0] https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/tree/tools/include/nolibc/stackprotector.h?h=dev.2023.06.16a
[1] https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/tree/tools/testing/selftests/nolibc/Makefile?h=dev.2023.06.16a#n81

> Cc: Stefan Hajnoczi <stefanha@...hat.com>
> Cc: Guillem Jover <guillem@...rons.org>
> Co-authored-by: Alviro Iskandar Setiawan <alviro.iskandar@...weeb.org>
> Signed-off-by: Alviro Iskandar Setiawan <alviro.iskandar@...weeb.org>
> Signed-off-by: Ammar Faizi <ammarfaizi2@...weeb.org>
> ---
>  src/Makefile | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/src/Makefile b/src/Makefile
> index 951c48fc6797be75..c4c28cbe87c7a8de 100644
> --- a/src/Makefile
> +++ b/src/Makefile
> @@ -10,9 +10,8 @@ CPPFLAGS ?=
>  override CPPFLAGS += -D_GNU_SOURCE \
>  	-Iinclude/ -include ../config-host.h \
>  	-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64
> -CFLAGS ?= -g -O3 -Wall -Wextra
> +CFLAGS ?= -g -O3 -Wall -Wextra -fno-stack-protector
>  override CFLAGS += -Wno-unused-parameter \
> -	-fno-stack-protector \
>  	-DLIBURING_INTERNAL \
>  	$(LIBURING_CFLAGS)
>  SO_CFLAGS=-fPIC $(CFLAGS)
> @@ -46,8 +45,8 @@ liburing_srcs := setup.c queue.c register.c syscall.c version.c
>  
>  ifeq ($(CONFIG_NOLIBC),y)
>  	liburing_srcs += nolibc.c
> -	override CFLAGS += -nostdlib -nodefaultlibs -ffreestanding -fno-builtin
> -	override CPPFLAGS += -nostdlib -nodefaultlibs -ffreestanding -fno-builtin
> +	override CFLAGS += -nostdlib -nodefaultlibs -ffreestanding -fno-builtin -fno-stack-protector
> +	override CPPFLAGS += -nostdlib -nodefaultlibs -ffreestanding -fno-builtin -fno-stack-protector
>  	override LINK_FLAGS += -nostdlib -nodefaultlibs
>  endif
>  
> -- 
> Ammar Faizi
>