linux-kernel - Re: [PATCH 6/8] tools/nolibc: tests: add test for -fstack-protector

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Date:   Sun, 26 Mar 2023 20:45:04 +0200
From:   Willy Tarreau <w@....eu>
To:     Thomas Weißschuh <thomas@...ch.de>
Cc:     Alexey Dobriyan <adobriyan@...il.com>,
        Thomas Weißschuh <linux@...ssschuh.net>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/8] tools/nolibc: tests: add test for -fstack-protector

On Sun, Mar 26, 2023 at 01:42:35PM -0500, Thomas Weißschuh  wrote:
> 
> Mar 26, 2023 13:30:21 Alexey Dobriyan <adobriyan@...il.com>:
> 
> > Willy Tarreau wrote:
> >> #if defined(__clang__)
> >> __attribute__((optnone))
> >> #elif defined(__GNUC__)
> >> __attribute__((optimize("O0")))
> >> #endif
> >> static int smash_stack(void)
> >> {
> >>     char buf[100];
> >>
> >>     for (size_t i = 0; i < 200; i++)
> >>         buf[i] = 'P';
> >>
> >>     return 1;
> >> }
> >
> > If you want to corrupt the stack, corrupt the stack!
> 
> I do!
> 
> > asm(
> > ".globl f\n"
> > "f:\n"
> > "movq $0, (%rsp)\n"
> > "ret\n"
> > ".type f,@function\n"
> > ".size f,.-f"
> > );
> > > No problems with optimisation levels.
> 
> Wouldn't this be architecture-specific?

Yes it would. I'm not seeing any issue with your approach instead, let's
keep it as-is for now (also it does what the stack protector is supposed
to catch anyway).

Willy