On Tue, 17 Dec 2019 16:06:42 +0100 Thomas Huth <[email protected]> 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 <[email protected]> > --- > tests/boot-sector.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tests/boot-sector.c b/tests/boot-sector.c > index 7824286b9a..9e66c6d013 100644 > --- a/tests/boot-sector.c > +++ b/tests/boot-sector.c > @@ -75,11 +75,11 @@ static const uint8_t s390x_psw_and_magic[] = { > 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40 /* in the s390-ccw bios > */ > }; > static const uint8_t s390x_code[] = { > - 0xa7, 0xf4, 0x00, 0x0a, /* j 0x10010 */ > + 0xa7, 0xf4, 0x00, 0x08, /* j 0x10010 */ > 0x00, 0x00, 0x00, 0x00, > 'S', '3', '9', '0', > 'E', 'P', 0x00, 0x01, > - 0xa7, 0x38, HIGH(SIGNATURE_ADDR), LOW(SIGNATURE_ADDR), /* lhi r3,0x7c10 > */ > + 0xa7, 0x39, HIGH(SIGNATURE_ADDR), LOW(SIGNATURE_ADDR), /* lghi r3,0x7c10 > */ > 0xa7, 0x48, LOW(SIGNATURE), HIGH(SIGNATURE), /* lhi r4,0xadde > */ > 0x40, 0x40, 0x30, 0x00, /* sth r4,0(r3) */ > 0xa7, 0xf4, 0xff, 0xfa /* j 0x10010 */ Looks good to me. I plan to queue this (and re-queue the other patches I had dropped), but would not mind another review.
