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

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Message-ID: <89a960c7-0c9b-43ab-9fc8-a68405f7ed6a@p183>
Date:   Sun, 26 Mar 2023 21:30:18 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Willy Tarreau <w@....eu>
Cc:     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

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!

asm(
".globl f\n"
"f:\n"
"movq $0, (%rsp)\n"
"ret\n"
".type f,@function\n"
".size f,.-f"
);

No problems with optimisation levels.