[Qemu-devel] [PATCH] memory: don't sign-extend 32-bit writes

[Ladi Prosek <lprosek@redhat.com>]

ldl_p has a signed return type so assigning it to uint64_t implicitly
sign-extends the value. This results in devices with min_access_size = 8
seeing unexpected values passed to their write handlers.

Example: guest performs a 32-bit write of 0x80000000 to an mmio region
and the handler receives 0xFFFFFFFF80000000 in its value argument.

Signed-off-by: Ladi Prosek <lprosek@redhat.com>
---
 exec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/exec.c b/exec.c
index f2bed92..b05c5d2 100644
--- a/exec.c
+++ b/exec.c
@@ -2630,7 +2630,7 @@ static MemTxResult address_space_write_continue(AddressSpace *as, hwaddr addr,
                 break;
             case 4:
                 /* 32 bit write access */
-                val = ldl_p(buf);
+                val = (uint32_t)ldl_p(buf);
                 result |= memory_region_dispatch_write(mr, addr1, val, 4,
                                                        attrs);
                 break;
-- 
2.7.4