linux-kernel - Re: [PATCH 1/2] powerpc: initial stack protector (-fstack-protector) support

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Message-ID: <20180917164613.GJ23155@gate.crashing.org>
Date:   Mon, 17 Sep 2018 11:46:13 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] powerpc: initial stack protector (-fstack-protector) support

Hi!

On Mon, Sep 17, 2018 at 12:15:05PM +0000, Christophe Leroy wrote:
> Now, GCC offers the possibility to manually set the
> stack-protector mode (global or tls) regardless of libc support.

Yup :-)

> This time, the patch selects HAVE_STACKPROTECTOR only if
> -mstack-protector-guard=global is supported by GCC.

"global" is weaker than "tls" (it is easier to read the cookie in an
exploit).  It is better to use tls if you can.


Segher