For the stage2 of zipl's boot loaders only 3 heap pages are available
[0x6000, 0x6000 + 0x3000]. Therefore, stage2 code needs to be very careful
when and for how long it allocates a heap page.
The heap OOM problem in stage2 was hidden until the commit 252be376
("zipl/boot: fix potential heap overflow in stage2"). Before this commit,
stage2 assumed that heap is 4 pages large which is apparently very wrong
but get_zeroed_page() still allowed allocating an extra 4th page by
overriding the memory segment following the heap area of stage2 (stage3
parameter area).
Try to avoid allocating a heap page and keeping it allocated over a long
period of time in the DASD dumpers. Free a heap page as soon as possible
if not required anymore.
And be extra careful with printf() because it always tries to allocate
a free heap page.
Fixes: 252be376 ("zipl/boot: fix potential heap overflow in stage2")
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Update zipl DASD standalone dumpers for single-volume, multi-volume and FBA
to drop the sets of zero pages when dumping memory to disk. Thus, all
continuous sets of zero-megabytes in the memory are dropped during the dump
stage.
Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
This commit is based on the s390-tools-1.39.0 version.
Changes on top of s390-tools-1.39.0:
- Add MIT license to all source files
- Add LICENSE file
- Transform REAMDE to README.md (markdown)
- Add AUTHORS.md file
- Add CONTRIBUTING.md file
- Move changelog from README to CHANGELOG.md file
Reviewed-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
