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memory: Fix access_with_adjusted_size(small size) on big-endian memory regions

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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.
This commit is contained in:
Philippe Mathieu-Daudé 2018-10-04 04:40:37 -04:00 committed by Lioncash
parent de28c93299
commit a3938167d4
No known key found for this signature in database
GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 23 additions and 11 deletions
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32
qemu/memory.c
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@ -444,24 +444,36 @@ static void adjust_endianness(MemoryRegion *mr, uint64_t *data, unsigned size)
} }
static inline void memory_region_shift_read_access(uint64_t *value, static inline void memory_region_shift_read_access(uint64_t *value,
unsigned shift, signed shift,
uint64_t mask, uint64_t mask,
uint64_t tmp) uint64_t tmp)
{ {
if (shift >= 0) {
*value |= (tmp & mask) << shift; *value |= (tmp & mask) << shift;
} else {
*value |= (tmp & mask) >> -shift;
}
} }
static inline uint64_t memory_region_shift_write_access(uint64_t *value, static inline uint64_t memory_region_shift_write_access(uint64_t *value,
unsigned shift, signed shift,
uint64_t mask) 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 MemTxResult memory_region_oldmmio_read_accessor(MemoryRegion *mr, static MemTxResult memory_region_oldmmio_read_accessor(MemoryRegion *mr,
hwaddr addr, hwaddr addr,
uint64_t *value, uint64_t *value,
unsigned size, unsigned size,
unsigned shift, signed shift,
uint64_t mask, uint64_t mask,
MemTxAttrs attrs) MemTxAttrs attrs)
{ {
@ -478,7 +490,7 @@ static MemTxResult memory_region_read_accessor(MemoryRegion *mr,
hwaddr addr, hwaddr addr,
uint64_t *value, uint64_t *value,
unsigned size, unsigned size,
unsigned shift, signed shift,
uint64_t mask, uint64_t mask,
MemTxAttrs attrs) MemTxAttrs attrs)
{ {
@ -497,7 +509,7 @@ static MemTxResult memory_region_read_with_attrs_accessor(MemoryRegion *mr,
hwaddr addr, hwaddr addr,
uint64_t *value, uint64_t *value,
unsigned size, unsigned size,
unsigned shift, signed shift,
uint64_t mask, uint64_t mask,
MemTxAttrs attrs) MemTxAttrs attrs)
{ {
@ -519,7 +531,7 @@ static MemTxResult memory_region_oldmmio_write_accessor(MemoryRegion *mr,
hwaddr addr, hwaddr addr,
uint64_t *value, uint64_t *value,
unsigned size, unsigned size,
unsigned shift, signed shift,
uint64_t mask, uint64_t mask,
MemTxAttrs attrs) MemTxAttrs attrs)
{ {
@ -533,7 +545,7 @@ static MemTxResult memory_region_write_accessor(MemoryRegion *mr,
hwaddr addr, hwaddr addr,
uint64_t *value, uint64_t *value,
unsigned size, unsigned size,
unsigned shift, signed shift,
uint64_t mask, uint64_t mask,
MemTxAttrs attrs) MemTxAttrs attrs)
{ {
@ -547,7 +559,7 @@ static MemTxResult memory_region_write_with_attrs_accessor(MemoryRegion *mr,
hwaddr addr, hwaddr addr,
uint64_t *value, uint64_t *value,
unsigned size, unsigned size,
unsigned shift, signed shift,
uint64_t mask, uint64_t mask,
MemTxAttrs attrs) MemTxAttrs attrs)
{ {
@ -571,7 +583,7 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
hwaddr addr, hwaddr addr,
uint64_t *value, uint64_t *value,
unsigned size, unsigned size,
unsigned shift, signed shift,
uint64_t mask, uint64_t mask,
MemTxAttrs attrs), MemTxAttrs attrs),
MemoryRegion *mr, MemoryRegion *mr,