linux-kernel - Re: [PATCH] idle/x86: remove the call to boot_init_stack_canary() from cpu_startup

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Message-ID: <b9727c41-8278-7b83-e5e1-61268dc768d5@suse.com>
Date:   Fri, 19 Oct 2018 12:01:58 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, xen-devel@...ts.xenproject.org,
        linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] idle/x86: remove the call to boot_init_stack_canary()
 from cpu_startup_entry()

On 19/10/2018 11:29, Christophe Leroy wrote:
> commit d7880812b359 ("idle: Add the stack canary init to
> cpu_startup_entry()") added the call to boot_init_stack_canary()
> in cpu_startup_entry() in an #ifdef CONFIG_X86 statement, with
> the intention to remove that #ifdef later.
> 
> While implementing stack protector for powerpc, it has been
> observed that calling boot_init_stack_canary() is also needed
> for powerpc which uses per task (TLS) stack canary like the X86.
> 
> However, calling boot_init_stack_canary() would break arches
> using global stack canary (ARM, SH, MIPS and XTENSA).
> 
> Instead of adding modifying the #ifdef in a
> implemented the call to boot_init_stack_canary() in the function
> calling cpu_startup_entry()

I can't parse this sentence.

> 
> On x86, we have two functions calling cpu_startup_entry():
> - start_secondary()
> - cpu_bringup_and_idle()
> 
> start_secondary() already calls boot_init_stack_canary().
> 
> This patch adds the call to boot_init_stack_canary() in
> cpu_bringup_and_idle() and removes it from cpu_startup_entry()
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

With the commit message made understandable you can add my

Reviewed-by: Juergen Gross <jgross@...e.com>


Juergen