motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-12-18 05:28:36 -07:00
Code Issues Projects Releases Packages Wiki Activity Actions

memory: use signed arithmetic

Browse source 
When trying to map an alias of a ram region, where the alias starts at
address A and we map it into address B, and A > B, we had an arithmetic
underflow.  Because we use unsigned arithmetic, the underflow converted
into a large number which failed addrrange_intersects() tests.

The concrete example which triggered this was cirrus vga mapping
the framebuffer at offsets 0xc0000-0xc7fff (relative to the start of
the framebuffer) into offsets 0xa0000 (relative to system addres space
start).

With our favorite analogy of a windowing system, this is equivalent to
dragging a subwindow off the left edge of the screen, and failing to clip
it into its parent window which is on screen.

Fix by switching to signed arithmetic.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Avi Kivity 2011-08-03 11:56:14 +03:00 • committed by Anthony Liguori
parent 39b796f28c
commit 8417cebfda
2 changed files with 15 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

2
exec.c
View file

@ -3818,7 +3818,7 @@ static void io_mem_init(void)
static void memory_map_init(void)
{
system_memory = qemu_malloc(sizeof(*system_memory));
memory_region_init(system_memory, "system", UINT64_MAX);
memory_region_init(system_memory, "system", INT64_MAX);
set_system_memory_map(system_memory);
}