other: 0.171 semantic: 0.139 performance: 0.096 device: 0.094 vnc: 0.063 network: 0.057 graphic: 0.054 PID: 0.053 debug: 0.051 permissions: 0.050 socket: 0.050 files: 0.049 boot: 0.038 KVM: 0.034 semantic: 0.159 debug: 0.101 other: 0.099 network: 0.098 performance: 0.087 files: 0.086 PID: 0.077 vnc: 0.060 socket: 0.057 device: 0.050 boot: 0.046 permissions: 0.039 graphic: 0.022 KVM: 0.019 No check for unaligned data access in ARM32 instructions hi According to the ARM documentation, there are alignment requirements of load/store instructions. Alignment fault should be raised if the alignment check is failed. However, it seems that QEMU doesn't implement this, which is against the documentation of ARM. For example, the instruction LDRD/STRD/LDREX/STREX must check the address is word alignment no matter what value the SCTLR.A is. I attached a testcase, which contains a instruction at VA 0x10240: ldrd r0,[pc.#1] in the main function. QEMU can successfully load the data in the unaligned address. The test is done in QEMU 5.1.0. I can provide more testcases for the other instructions if you need. Many thanks. To patch this, we need a check while we translate the instruction to tcg. If the address is unaligned, a signal number (i.e., SIGBUS) should be raised. Regards Muhui We don't implement SCTLR.A, but you're right that we should be checking the mandatory alignments. Note! Any fix will only apply to system mode (qemu-system-arm) and not user-only mode (qemu-arm). Thanks for confirmation. Btw: I was wondering why the fix will only apply to system mode rather than user-only mode. Unaligned data access is not permitted in user level programs, either. Because for user-only, we cheat and use host load/store operations directly. This makes for much faster emulation but imposes a number of limitations -- including ignoring of the alignment bits on hosts that have native unaligned accesses. As a corollary, when running user-only on a host that enforces alignment, you cannot emulate a guest that *allows* unaligned accesses. Proposed patches: https://