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[Qemu-devel] [PATCH 4/4] exec: fix incorrect assumptions in memory_acces
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 4/4] exec: fix incorrect assumptions in memory_access_size |
Date: |
Fri, 19 Jul 2013 22:07:58 +0200 |
access_size_min can be 1 because erroneous accesses must not crash
QEMU, they should trigger exceptions in the guest or just return
garbage (depending on the CPU). I am not sure I understand the
comment: placing a 4-byte field at the last byte of a region
makes no sense (unless impl.unaligned is true), and that is
why memory.c:access_with_adjusted_size does not bother with
minimums larger than the remaining length.
access_size_max can be mr->ops->valid.max_access_size because memory.c
can and will still break accesses bigger than
mr->ops->impl.max_access_size.
Reported-by: Markus Armbruster <address@hidden>
Tested-by: Markus Armbruster <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
exec.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/exec.c b/exec.c
index d312bb4..c8658c6 100644
--- a/exec.c
+++ b/exec.c
@@ -1898,14 +1898,10 @@ static inline bool memory_access_is_direct(MemoryRegion
*mr, bool is_write)
static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
{
- unsigned access_size_min = mr->ops->impl.min_access_size;
- unsigned access_size_max = mr->ops->impl.max_access_size;
+ unsigned access_size_max = mr->ops->valid.max_access_size;
/* Regions are assumed to support 1-4 byte accesses unless
otherwise specified. */
- if (access_size_min == 0) {
- access_size_min = 1;
- }
if (access_size_max == 0) {
access_size_max = 4;
}
@@ -1922,9 +1918,6 @@ static int memory_access_size(MemoryRegion *mr, unsigned
l, hwaddr addr)
if (l > access_size_max) {
l = access_size_max;
}
- /* ??? The users of this function are wrong, not supporting minimums larger
- than the remaining length. C.f. memory.c:access_with_adjusted_size. */
- assert(l >= access_size_min);
return l;
}
--
1.8.1.4