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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>
This commit is contained in:
Philippe Mathieu-Daudé 2018-09-27 02:24:16 +02:00 committed by Paolo Bonzini
parent 3c754a9383
commit 98f52cdbb5
1 changed files with 23 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
memory.c
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@ -375,18 +375,30 @@ static void adjust_endianness(MemoryRegion *mr, uint64_t *data, unsigned size)
}
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 @@ static MemTxResult memory_region_oldmmio_read_accessor(MemoryRegion *mr,
hwaddr addr,
uint64_t *value,
unsigned size,
unsigned shift,
signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@ -441,7 +453,7 @@ static MemTxResult memory_region_read_accessor(MemoryRegion *mr,
hwaddr addr,
uint64_t *value,
unsigned size,
unsigned shift,
signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@ -467,7 +479,7 @@ static MemTxResult memory_region_read_with_attrs_accessor(MemoryRegion *mr,
hwaddr addr,
uint64_t *value,
unsigned size,
unsigned shift,
signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@ -494,7 +506,7 @@ static MemTxResult memory_region_oldmmio_write_accessor(MemoryRegion *mr,
hwaddr addr,
uint64_t *value,
unsigned size,
unsigned shift,
signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@ -519,7 +531,7 @@ static MemTxResult memory_region_write_accessor(MemoryRegion *mr,
hwaddr addr,
uint64_t *value,
unsigned size,
unsigned shift,
signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@ -544,7 +556,7 @@ static MemTxResult memory_region_write_with_attrs_accessor(MemoryRegion *mr,
hwaddr addr,
uint64_t *value,
unsigned size,
unsigned shift,
signed shift,
uint64_t mask,
MemTxAttrs attrs)
{
@ -574,7 +586,7 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
hwaddr addr,
uint64_t *value,
unsigned size,
unsigned shift,
signed shift,
uint64_t mask,
MemTxAttrs attrs),
MemoryRegion *mr,