[Qemu-devel] [PATCH v2 0/4] hw/arm/boot: handle large Images more gracefully

[Peter Maydell]

This patchset attempts to fix https://bugs.launchpad.net/qemu/+bug/1823998
which reports that we don't handle kernels larger than 128MB
correctly, because we allow the initrd to be placed over the
tail end of the kernel. AArch64 kernel Image files (since v3.17)
report the total size they require (including any BSS area that
isn't in the Image itself), so we can use that to be sure we
place the initrd sufficiently far into the RAM.

Patches 1 and 2 are new since v1; patches 3 and 4 are the old
patches 1 and 2 (and are basically unchanged since v1).

Patches 1 and 2 in this series are new. Patch 1 fixes bugs
in the existing code where we were assuming that we could
treat info->ram_size as the address of the end of RAM, which
isn't true if the RAM doesn't start at address 0. (This
generally went unnoticed thanks to the magic of unsigned integer
underflow turning end-start calculations into very large max_size
values for load_ramdisk_as() and friends.)
Patch 2 adds some explicit checks that we don't try to put things
entirely off the end of RAM (which avoids those accidental
underflows).
Patch 3 in this series adjusts our "where do we put the initrd"
heuristic so that it always places it at least after whatever
our best guess at the kernel size is. (This might still not
be right for images like self-decompressing 32-bit kernels, where
there's no way to know how big the kernel will be after
decompression.)
Patch 4 makes load_aarch64_image() return the
kernel size as indicated in the Image file header, so that for
the specific case of AArch64 Image files we will definitely not
put the initrd on top of them.

thanks
-- PMM

Peter Maydell (4):
  hw/arm/boot: Don't assume RAM starts at address zero
  hw/arm/boot: Diagnose layouts that put initrd or DTB off the end of
    RAM
  hw/arm/boot: Avoid placing the initrd on top of the kernel
  hw/arm/boot: Honour image size field in AArch64 Image format kernels

 hw/arm/boot.c | 83 ++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 62 insertions(+), 21 deletions(-)

-- 
2.20.1