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Re: [PATCH] tests/boot-sector: Fix the bad s390x assembler code

From: Cornelia Huck
Subject: Re: [PATCH] tests/boot-sector: Fix the bad s390x assembler code
Date: Wed, 18 Dec 2019 17:53:03 +0100

On Tue, 17 Dec 2019 16:06:42 +0100
Thomas Huth <address@hidden> wrote:

> There are currently two bugs in s390x_code[]: First, the initial jump
> uses the wrong offset, so it was jumping to 0x1014 instead of 0x1010.
> Second, LHI only loads the lower 32-bit of the register.
> Everything worked fine as long as the s390-ccw bios code was jumping
> here with r3 containing zeroes in the uppermost 48 bit - which just
> happened to be the case so far by accident. But we can not rely on this
> fact, and indeed one of the recent suggested patches to jump2ipl.c cause
> the newer GCCs to put different values into r3. In that case the code
> from s390x_code[] crashes very ungracefully.
> Thus let's make sure to jump to the right instruction, and use LGHI
> instead of LHI to make sure that we always zero out the upper bits
> of the register.
> Signed-off-by: Thomas Huth <address@hidden>
> ---
>  tests/boot-sector.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Thanks, applied.

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