memory: Fix access_with_adjusted_size(small size) on big-endian memory regions
Memory regions configured as DEVICE_BIG_ENDIAN (or DEVICE_NATIVE_ENDIAN on
big-endian guest) behave incorrectly when the memory access 'size' is smaller
than the implementation 'access_size'.
In the following code segment from access_with_adjusted_size():
if (memory_region_big_endian(mr)) {
for (i = 0; i < size; i += access_size) {
r |= access_fn(mr, addr + i, value, access_size,
(size - access_size - i) * 8, access_mask, attrs);
}
(size - access_size - i) * 8 is the number of bits that will arithmetic
shift the current value.
Currently we can only 'left' shift a read() access, and 'right' shift a write().
When the access 'size' is smaller than the implementation, we get a negative
number of bits to shift.
For the read() case, a negative 'left' shift is a 'right' shift :)
However since the 'shift' type is unsigned, there is currently no way to
right shift.
Fix this by changing the access_fn() prototype to handle signed shift values,
and modify the memory_region_shift_read|write_access() helpers to correctly
arithmetic shift the opposite direction when the 'shift' value is negative.
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20180927002416.1781-4-f4bug@amsat.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/memory.c b/memory.c
index a4d3fa7..b96aec7 100644
--- a/memory.c
+++ b/memory.c
@@ -375,18 +375,30 @@
}
static inline void memory_region_shift_read_access(uint64_t *value,
- unsigned shift,
+ signed shift,
uint64_t mask,
uint64_t tmp)
{
- *value |= (tmp & mask) << shift;
+ if (shift >= 0) {
+ *value |= (tmp & mask) << shift;
+ } else {
+ *value |= (tmp & mask) >> -shift;
+ }
}
static inline uint64_t memory_region_shift_write_access(uint64_t *value,
- unsigned shift,
+ signed shift,
uint64_t mask)
{
- return (*value >> shift) & mask;
+ uint64_t tmp;
+
+ if (shift >= 0) {
+ tmp = (*value >> shift) & mask;
+ } else {
+ tmp = (*value << -shift) & mask;
+ }
+
+ return tmp;
}
static hwaddr memory_region_to_absolute_addr(MemoryRegion *mr, hwaddr offset)
@@ -415,7 +427,7 @@
hwaddr addr,
uint64_t *value,
unsigned size,
- unsigned shift,
+ signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@@ -441,7 +453,7 @@
hwaddr addr,
uint64_t *value,
unsigned size,
- unsigned shift,
+ signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@@ -467,7 +479,7 @@
hwaddr addr,
uint64_t *value,
unsigned size,
- unsigned shift,
+ signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@@ -494,7 +506,7 @@
hwaddr addr,
uint64_t *value,
unsigned size,
- unsigned shift,
+ signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@@ -519,7 +531,7 @@
hwaddr addr,
uint64_t *value,
unsigned size,
- unsigned shift,
+ signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@@ -544,7 +556,7 @@
hwaddr addr,
uint64_t *value,
unsigned size,
- unsigned shift,
+ signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@@ -574,7 +586,7 @@
hwaddr addr,
uint64_t *value,
unsigned size,
- unsigned shift,
+ signed shift,
uint64_t mask,
MemTxAttrs attrs),
MemoryRegion *mr,
