linux-kernel - Re: [PATCH] powerpc/booke: Avoid link stack corruption in several places

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Message-ID: <20210823155837.GX1583@gate.crashing.org>
Date:   Mon, 23 Aug 2021 10:58:37 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
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] powerpc/booke: Avoid link stack corruption in several places

On Mon, Aug 23, 2021 at 07:53:01AM +0000, Christophe Leroy wrote:
>  /* Be careful, this will clobber the lr register. */
>  #define LOAD_REG_ADDR_PIC(reg, name)		\
> -	bl	0f;				\
> +	bcl	20,31,0f			\
>  0:	mflr	reg;				\
>  	addis	reg,reg,(name - 0b)@ha;		\
>  	addi	reg,reg,(name - 0b)@l;

The code ended each line with a semicolon before, for absolutely no
reason that I can see, but still.  Fixing that would be nice, but only
doing it on one line isn't good.

Btw.  Both the 7450 and the modern cores implementing this really need
this to be $+4, so it is a lot clearer to write that instead of 1f or
a named label.


Segher