From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Jeremy Kerr <jk@ozlabs.org>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 3/4] powerpc/boot: Fix stack corruption in epapr entry point
Date: Wed, 11 Feb 2015 13:11:57 +1100 [thread overview]
Message-ID: <1423620717.5891.31.camel@kernel.crashing.org> (raw)
In-Reply-To: <1423570510.219047.52227904007.3.gpush@pablo>
On Tue, 2015-02-10 at 20:15 +0800, Jeremy Kerr wrote:
> Currently, a 64-bit little-endian zImage.epapr won't boot in epapr mode,
> as as we never return from platform_init.
>
> Before entering C, we initialise our stack by setting r1 16 bytes below
> the end of the _bss_stack:
>
> stwu r0,-16(r1) /* establish a stack frame */
>
> However, the called function will save the caller's lr in the caller's
> frame's lr save area, at -16(r1) to -32(r1).
>
> This means that writes to the fdt variable corrupt the saved link
> register:
>
> 0000000020c06018 l O .bss 0000000000001000 _bss_stack
> 0000000020c07018 l O .bss 0000000000000008 fdt
>
> This change allocates the minimum of 32 bytes for the base of the stack
> instead.
Is that sufficient for ABI v1 ? It feels like it's broken for BE as
well...
Ben.
> Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
>
> ---
> arch/powerpc/boot/crt0.S | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/boot/crt0.S b/arch/powerpc/boot/crt0.S
> index 14de4f8..bf8eeee 100644
> --- a/arch/powerpc/boot/crt0.S
> +++ b/arch/powerpc/boot/crt0.S
> @@ -218,7 +218,7 @@ p_base: mflr r10 /* r10 now points to runtime addr of p_base */
> beq 6f
> ld r1,0(r8)
> li r0,0
> - stdu r0,-16(r1) /* establish a stack frame */
> + stdu r0,-32(r1) /* establish a stack frame */
> 6:
> #endif /* __powerpc64__ */
> /* Call platform_init() */
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
next prev parent reply other threads:[~2015-02-11 2:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-10 12:15 [PATCH 1/4] powerpc/boot/fdt: Add little-endian support to libfdt wrappers Jeremy Kerr
2015-02-10 12:15 ` [PATCH 2/4] powerpc/boot/wrapper: use the pseries wrapper for zImage.epapr Jeremy Kerr
2015-02-11 2:12 ` Benjamin Herrenschmidt
2015-02-11 2:16 ` Jeremy Kerr
2015-02-11 2:20 ` Benjamin Herrenschmidt
2015-02-10 12:15 ` [PATCH 3/4] powerpc/boot: Fix stack corruption in epapr entry point Jeremy Kerr
2015-02-11 2:11 ` Benjamin Herrenschmidt [this message]
2015-02-10 12:15 ` [PATCH 4/4] powerpc/boot: don't clobber r6 and r7 in epapr boot Jeremy Kerr
2015-02-11 2:09 ` Benjamin Herrenschmidt
2015-02-11 4:27 ` Jeremy Kerr
2015-02-11 4:50 ` Benjamin Herrenschmidt
2015-02-11 2:11 ` [PATCH 1/4] powerpc/boot/fdt: Add little-endian support to libfdt wrappers Benjamin Herrenschmidt
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