WAMR triggers UBSAN alignment issues on x86-64/x86 when built with Fast JIT

[arvid-norlander]

Building iwasm (or embedding into the program) with GCC undefined sanitizer when Fast JIT is enabled causes the following:

$ ./iwasm simple_wasm.wasm
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:9317:32: runtime error: store to misaligned address 0x5631a8a597d5 for type 'int32', which requires 4 byte alignment
0x5631a8a597d5: note: pointer points here
 3c 00 0f 85 00 00 00  00 4c 89 e7 48 c7 c6 11  00 00 00 48 b8 00 2e d0  a6 31 56 00 00 ff d0 b8  01
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:6202:34: runtime error: store to misaligned address 0x7f66044003a6 for type 'uintptr_t', which requires 8 byte alignment
0x7f66044003a6: note: pointer points here
 00 00 48 be ff ff  ff ff ff ff ff 7f 48 89  75 18 41 ff e2 4d 8b 47  10 4c 89 c7 48 c7 c6 00  00 00
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:5510:32: runtime error: store to misaligned address 0x7f63f000999f for type 'int32', which requires 4 byte alignment
0x7f63f000999f: note: pointer points here
 00 00 0f 84 00  00 00 00 48 89 75 18 41  ff e0 89 d0 4c 8b 85 d8  00 00 00 83 f8 00 89 45  58 0f 84
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:6188:30: runtime error: store to misaligned address 0x7f660440042d for type 'int32', which requires 4 byte alignment
0x7f660440042d: note: pointer points here
 39 d1 0f 87 00 00 00  00 49 81 e9 f8 00 00 00  4d 89 8f a0 0c 00 00 4d  89 c1 49 83 c1 50 4d 89  48
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:5772:33: runtime error: store to misaligned address 0x7f63f8010172 for type 'uint32', which requires 4 byte alignment
0x7f63f8010172: note: pointer points here
 fe 12  0f 82 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:6197:34: runtime error: store to misaligned address 0x7f6604405821 for type 'uintptr_t', which requires 8 byte alignment
0x7f6604405821: note: pointer points here
 ff ff ff  ff ff ff ff ff ff ff ff  ff 8b 4d 58 41 89 c8 4d  8b 4f 10 4d 8b 89 58 01  00 00 43 8b 1c
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:6206:34: runtime error: store to misaligned address 0x7f660440578e for type 'uintptr_t', which requires 8 byte alignment
0x7f660440578e: note: pointer points here
 00 00 48 b8 ff ff  ff ff ff ff ff 7f ff 24  f0 8a 5d 40 04 66 7f 00  00 29 58 40 04 66 7f 00  00 79
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:7987:25: runtime error: store to misaligned address 0x7f63f004966b for type 'int32', which requires 4 byte alignment
0x7f63f004966b: note: pointer points here
 04  11 40 e9 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00
              ^ 
52

The interpreter also triggers such issues

$ ./iwasm --interp simple_wasm.wasm
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:9317:32: runtime error: store to misaligned address 0x556e0421f7d5 for type 'int32', which requires 4 byte alignment
0x556e0421f7d5: note: pointer points here
 3c 00 0f 85 00 00 00  00 4c 89 e7 48 c7 c6 11  00 00 00 48 b8 00 ee eb  03 6e 55 00 00 ff d0 b8  01
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:6188:30: runtime error: store to misaligned address 0x7fe2ed20024d for type 'int32', which requires 4 byte alignment
0x7fe2ed20024d: note: pointer points here
 39 d1 0f 87 00 00 00  00 49 81 e9 f8 00 00 00  4d 89 8f a0 0c 00 00 4d  89 c1 49 83 c1 50 4d 89  48
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:5510:32: runtime error: store to misaligned address 0x7fe0e000999f for type 'int32', which requires 4 byte alignment
0x7fe0e000999f: note: pointer points here
 00 00 0f 84 00  00 00 00 48 89 75 18 41  ff e0 89 d0 4c 8b 85 d8  00 00 00 83 f8 00 89 45  58 0f 84
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:6202:34: runtime error: store to misaligned address 0x7fe2ed200706 for type 'uintptr_t', which requires 8 byte alignment
0x7fe2ed200706: note: pointer points here
 00 00 48 be ff ff  ff ff ff ff ff 7f 48 89  75 18 41 ff e2 4d 8b 47  10 4c 89 c7 48 c7 c6 00  00 00
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3932:13: runtime error: member access within misaligned address 0x556e04224f5c for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04224f5c: note: pointer points here
  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3932:13: runtime error: member access within misaligned address 0x556e04224f5c for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04224f5c: note: pointer points here
  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3932:13: runtime error: member access within misaligned address 0x556e04224f5c for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04224f5c: note: pointer points here
  00 00 00 00 66 b9 21 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3932:13: runtime error: member access within misaligned address 0x556e04224f5c for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04224f5c: note: pointer points here
  00 00 00 00 66 b9 21 04  6e 55 00 00 a6 b9 21 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:5772:33: runtime error: store to misaligned address 0x7fe0e80102a2 for type 'uint32', which requires 4 byte alignment
0x7fe0e80102a2: note: pointer points here
 fe 12  0f 82 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1244:17: runtime error: member access within misaligned address 0x556e04224f7c for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04224f7c: note: pointer points here
  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:6197:34: runtime error: store to misaligned address 0x7fe2ed205821 for type 'uintptr_t', which requires 8 byte alignment
0x7fe2ed205821: note: pointer points here
 ff ff ff  ff ff ff ff ff ff ff ff  ff 8b 4d 58 41 89 c8 4d  8b 4f 10 4d 8b 89 58 01  00 00 43 8b 1c
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1244:17: runtime error: member access within misaligned address 0x556e04224f7c for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04224f7c: note: pointer points here
  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:6206:34: runtime error: store to misaligned address 0x7fe2ed20578e for type 'uintptr_t', which requires 8 byte alignment
0x7fe2ed20578e: note: pointer points here
 00 00 48 b8 ff ff  ff ff ff ff ff 7f ff 24  f0 8a 5d 20 ed e2 7f 00  00 29 58 20 ed e2 7f 00  00 79
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1244:17: runtime error: member access within misaligned address 0x556e04224f7c for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04224f7c: note: pointer points here
  00 00 00 00 68 b9 21 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:7987:25: runtime error: store to misaligned address 0x7fe0e004966b for type 'int32', which requires 4 byte alignment
0x7fe0e004966b: note: pointer points here
 04  11 40 e9 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1244:17: runtime error: member access within misaligned address 0x556e04224f7c for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04224f7c: note: pointer points here
  00 00 00 00 68 b9 21 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:849:27: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3911:29: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3914:22: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3916:41: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3916:22: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3919:22: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3918:32: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3922:41: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3921:43: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3921:23: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3924:22: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3923:33: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1328:38: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 b0 38 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3852:9: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 a0 39 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3852:9: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 a0 39 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3852:9: runtime error: member access within misaligned address 0x556e04224fbc for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04224fbc: note: pointer points here
  00 00 00 00 00 4f 22 04  6e 55 00 00 a0 39 22 04  6e 55 00 00 eb b9 21 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:2144:13: runtime error: store to misaligned address 0x556e0422512c for type 'int64', which requires 8 byte alignment
0x556e0422512c: note: pointer points here
  60 12 01 00 20 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 c4 21 04 6e 55 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:2038:17: runtime error: load of misaligned address 0x556e0422512c for type 'int64', which requires 8 byte alignment
0x556e0422512c: note: pointer points here
  60 12 01 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 c4 21 04 6e 55 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1262:17: runtime error: member access within misaligned address 0x556e042253b4 for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e042253b4: note: pointer points here
  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1262:17: runtime error: member access within misaligned address 0x556e042253b4 for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e042253b4: note: pointer points here
  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1262:17: runtime error: member access within misaligned address 0x556e042253b4 for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e042253b4: note: pointer points here
  00 00 00 00 2a c6 21 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1262:17: runtime error: member access within misaligned address 0x556e042253b4 for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e042253b4: note: pointer points here
  00 00 00 00 2a c6 21 04  6e 55 00 00 2a c6 21 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1348:17: runtime error: member access within misaligned address 0x556e04225534 for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04225534: note: pointer points here
  00 00 00 00 69 c6 21 04  6e 55 00 00 00 00 00 00  00 00 00 00 10 53 22 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1348:17: runtime error: member access within misaligned address 0x556e04225534 for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04225534: note: pointer points here
  00 00 00 00 69 c6 21 04  6e 55 00 00 00 00 00 00  00 00 00 00 10 53 22 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1348:17: runtime error: member access within misaligned address 0x556e04225534 for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04225534: note: pointer points here
  00 00 00 00 69 c6 21 04  6e 55 00 00 00 00 00 00  00 00 00 00 10 53 22 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1352:44: runtime error: member access within misaligned address 0x556e04225534 for type 'struct WASMBranchBlock', which requires 8 byte alignment
0x556e04225534: note: pointer points here
  00 00 00 00 69 c6 21 04  6e 55 00 00 00 00 00 00  00 00 00 00 10 53 22 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:2038:17: runtime error: store to misaligned address 0x7fe0ed000d54 for type 'int64', which requires 8 byte alignment
0x7fe0ed000d54: note: pointer points here
  05 00 00 00 00 00 00 00  00 00 00 00 02 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3854:32: runtime error: member access within misaligned address 0x556e04225774 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225774: note: pointer points here
  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1334:36: runtime error: member access within misaligned address 0x556e04225774 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225774: note: pointer points here
  00 00 00 00 00 52 22 04  6e 55 00 00 60 3d 22 04  6e 55 00 00 57 c0 21 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1334:40: runtime error: member access within misaligned address 0x556e04225774 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225774: note: pointer points here
  00 00 00 00 00 52 22 04  6e 55 00 00 60 3d 22 04  6e 55 00 00 57 c0 21 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3947:24: runtime error: member access within misaligned address 0x556e04225774 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225774: note: pointer points here
  00 00 00 00 00 52 22 04  6e 55 00 00 60 3d 22 04  6e 55 00 00 57 c0 21 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3951:9: runtime error: member access within misaligned address 0x556e04225774 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225774: note: pointer points here
  00 00 00 00 00 52 22 04  6e 55 00 00 60 3d 22 04  6e 55 00 00 57 c0 21 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3951:9: runtime error: member access within misaligned address 0x556e04225774 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225774: note: pointer points here
  00 00 00 00 00 52 22 04  6e 55 00 00 60 3d 22 04  6e 55 00 00 57 c0 21 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3951:9: runtime error: member access within misaligned address 0x556e04225774 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225774: note: pointer points here
  00 00 00 00 00 52 22 04  6e 55 00 00 60 3d 22 04  6e 55 00 00 57 c0 21 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3951:9: runtime error: member access within misaligned address 0x556e04225774 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225774: note: pointer points here
  00 00 00 00 00 52 22 04  6e 55 00 00 60 3d 22 04  6e 55 00 00 57 c0 21 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3951:9: runtime error: member access within misaligned address 0x556e04225774 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225774: note: pointer points here
  00 00 00 00 00 52 22 04  6e 55 00 00 60 3d 22 04  6e 55 00 00 57 c0 21 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3951:9: runtime error: member access within misaligned address 0x556e04225774 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225774: note: pointer points here
  00 00 00 00 00 52 22 04  6e 55 00 00 60 3d 22 04  6e 55 00 00 57 c0 21 04  6e 55 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:1991:17: runtime error: store to misaligned address 0x556e042257d4 for type 'int64', which requires 8 byte alignment
0x556e042257d4: note: pointer points here
  68 0e 01 00 80 12 01 00  04 00 00 00 fa e8 21 04  6e 55 00 00 2b eb 21 04  6e 55 00 00 d0 57 22 04
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:849:27: runtime error: member access within misaligned address 0x556e04225a64 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225a64: note: pointer points here
  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:895:21: runtime error: member access within misaligned address 0x556e04225a64 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225a64: note: pointer points here
  00 00 00 00 e4 59 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:896:15: runtime error: member access within misaligned address 0x556e04225a64 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225a64: note: pointer points here
  00 00 00 00 e4 59 22 04  6e 55 00 00 f0 37 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:897:17: runtime error: member access within misaligned address 0x556e04225a64 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225a64: note: pointer points here
  00 00 00 00 e4 59 22 04  6e 55 00 00 f0 37 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:897:15: runtime error: member access within misaligned address 0x556e04225a64 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225a64: note: pointer points here
  00 00 00 00 e4 59 22 04  6e 55 00 00 f0 37 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:932:67: runtime error: member access within misaligned address 0x556e04225a64 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e04225a64: note: pointer points here
  00 00 00 00 e4 59 22 04  6e 55 00 00 f0 37 22 04  6e 55 00 00 00 00 00 00  00 00 00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:946:19: runtime error: member access within misaligned address 0x556e042259e4 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e042259e4: note: pointer points here
  6e 55 00 00 1c 59 22 04  6e 55 00 00 00 3a 22 04  6e 55 00 00 16 ba 21 04  6e 55 00 00 1c e9 21 04
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:947:19: runtime error: member access within misaligned address 0x556e042259e4 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e042259e4: note: pointer points here
  6e 55 00 00 1c 59 22 04  6e 55 00 00 00 3a 22 04  6e 55 00 00 16 ba 21 04  6e 55 00 00 1c e9 21 04
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:947:23: runtime error: member access within misaligned address 0x556e042259e4 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e042259e4: note: pointer points here
  6e 55 00 00 1c 59 22 04  6e 55 00 00 00 3a 22 04  6e 55 00 00 16 ba 21 04  6e 55 00 00 1c e9 21 04
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3874:24: runtime error: member access within misaligned address 0x556e042259e4 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e042259e4: note: pointer points here
  6e 55 00 00 1c 59 22 04  6e 55 00 00 00 3a 22 04  6e 55 00 00 16 ba 21 04  6e 55 00 00 1c e9 21 04
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3875:22: runtime error: member access within misaligned address 0x556e042259e4 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e042259e4: note: pointer points here
  6e 55 00 00 1c 59 22 04  6e 55 00 00 00 3a 22 04  6e 55 00 00 16 ba 21 04  6e 55 00 00 1c e9 21 04
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3876:13: runtime error: member access within misaligned address 0x556e042259e4 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e042259e4: note: pointer points here
  6e 55 00 00 1c 59 22 04  6e 55 00 00 00 3a 22 04  6e 55 00 00 16 ba 21 04  6e 55 00 00 1c e9 21 04
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3876:13: runtime error: member access within misaligned address 0x556e042259e4 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e042259e4: note: pointer points here
  6e 55 00 00 1c 59 22 04  6e 55 00 00 00 3a 22 04  6e 55 00 00 16 ba 21 04  6e 55 00 00 1c e9 21 04
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/interpreter/wasm_interp_classic.c:3876:13: runtime error: member access within misaligned address 0x556e042259e4 for type 'struct WASMInterpFrame', which requires 8 byte alignment
0x556e042259e4: note: pointer points here
  6e 55 00 00 1c 59 22 04  6e 55 00 00 00 3a 22 04  6e 55 00 00 16 ba 21 04  6e 55 00 00 1c e9 21 04
              ^ 
52

I'm using WAMR-1.2.2. I notice that with the embedded build I can trigger this even without the Fast JIT, as long as the fast interpreter is enabled. With iwasm I need the Fast JIT to be enabled, though then I can trigger it for the interpreter as well.

The build command I used to reproduce this with iwasm on Linux was:

CFLAGS='-fsanitize=undefined' CXXFLAGS='-fsanitize=undefined' cmake -DWAMR_BUILD_FAST_JIT=1 -GNinja ..

I'm using Ubuntu 22.04, GCC 11.3.0-1ubuntu1~22.04.1

Here is the wasm file I used: simple_wasm.wasm.tar.gz

I do believe that this isn't generally a problem on x86/x86-64 (it is on ARM though), but our company has a 0-ubsan (as well as asan/tsan) issues policy in the CI. And even on x86/x86-64 my understanding is that unaligned access is slower than aligned access (plus, in case of SSE/AVX by the compiler, outright unsupported, and it can potentially auto-vectorize based on assumed alignment from the type).

[wenyongh]

@arvid-norlander For interpreter, could you try changing WASM_CPU_SUPPORTS_UNALIGNED_ADDR_ACCESS to 0 in core/config.h? Or add add_definitions(-DWASM_CPU_SUPPORTS_UNALIGNED_ADDR_ACCESS=0) in CMakeLists.txt.
For fast-jit, it really needs effort to modify the code, since we assume x86 supports unaligned memory access and there are many such cases, e.g., *(uintptr_t *)stream = (uintptr_t)stream + 11

[arvid-norlander]

Sure, I could try that. I'll get back to you on that shortly.

While x86 does support unaligned access, I'm not sure about what the compiler guarantees with respect to the standard. I believe it is allowed to optimize based on assuming that you are not performing unaligned access for example. At least I have seen this happen, where GCC incorrectly vectorised a loop to a sometimes unaligned array of uint32_t, which would result in crashes in release builds.

[arvid-norlander]

With -DWASM_CPU_SUPPORTS_UNALIGNED_ADDR_ACCESS=0) I get largely the same amount of errors for JIT and interpreter respectively. I also notice I get errors in the AOT case (which I didn't test before):

$ ./iwasm simple_wasm_x86-64.aot 
/home/user/wasm-micro-runtime/core/iwasm/fast-jit/cg/x86-64/jit_codegen_x86_64.cpp:9317:32: runtime error: store to misaligned address 0x55edcf2e07d5 for type 'int32', which requires 4 byte alignment
0x55edcf2e07d5: note: pointer points here
 3c 00 0f 85 00 00 00  00 4c 89 e7 48 c7 c6 11  00 00 00 48 b8 80 2f e4  ce ed 55 00 00 ff d0 b8  01
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/aot/arch/aot_reloc_x86_64.c:87:22: runtime error: store to misaligned address 0x0000406b14ba for type 'uint64', which requires 8 byte alignment
0x0000406b14ba: note: pointer points here
 00 00  48 b8 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00
              ^ 
/home/user/wasm-micro-runtime/core/iwasm/aot/arch/aot_reloc_x86_64.c:182:60: runtime error: store to misaligned address 0x0000406ac107 for type 'int32', which requires 4 byte alignment
0x0000406ac107: note: pointer points here
 f2 0f 59 05 00  00 00 00 f2 0f 58 c1 c3  0f 1f 40 00 41 57 41 56  41 54 53 50 4c 8b 7f 10  49 8b 87
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/aot/arch/aot_reloc_x86_64.c:252:60: runtime error: store to misaligned address 0x0000406ac1ae for type 'int32', which requires 4 byte alignment
0x0000406ac1ae: note: pointer points here
 00 00 00 e8 00 00  00 00 31 c0 5b c3 0f b7  c0 5b c3 66 0f 1f 84 00  00 00 00 00 55 41 57 41  56 41
             ^ 
/home/user/wasm-micro-runtime/core/iwasm/aot/arch/aot_reloc_x86_64.c:208:60: runtime error: store to misaligned address 0x0000406ae367 for type 'int32', which requires 4 byte alignment
0x0000406ae367: note: pointer points here
 3c ff 24 c5 00  00 00 00 45 85 e4 74 0b  83 7c 24 10 00 0f 88 11  25 00 00 48 8b 5c 24 30  f3 41 0f
             ^ 
52

I have not looked into performance differences (it would likely not show on this simple test program). The main reason I worry is if this might invoke undefined behavior in the optimiser. Even if x86 supports this fine, what is UB or not depends on the so called "abstract machine" that the C/C++ standards define. And it is this that determines what the compiler is allowed to make assumptions for optimization based on.

[arvid-norlander]

Based on some search, it seems my worries might be well founded:

• C++: https://stackoverflow.com/questions/51126257/what-does-the-standard-say-about-unaligned-memory-access
• C/C++: https://stackoverflow.com/a/44746472
• Possibly the best way to do this is via packed structs according to this post: https://www.alfonsobeato.net/arm/how-to-access-safely-unaligned-data/
• llvm 14 warns with unaligned access for the packed struct. llvm/llvm-project#55520 says "misaligned access is equally undefined on all targets"

And of course, I have my own experience of this being taken advantage of (with G++) where it auto-vectorized code which resulted in failures at runtime due to using aligned SSE instructions.

[wenyongh]

Hi, since x86-64/x86-32 supports memory access on unaligned address, currently we just do in that way in many places of the runtime implementation, it should be a normal behavior, there is no issue found and it may help reduce the footprint. For the machine code generated in JIT/AOT, if it is an SSE instruction, we will choose the instruction that supports memory access on unaligned address.

But if changing to memory access on aligned address may improve the performance, we are also grad to support, for example, add controls in interpreter/fast-jit/aot according to the value of WASM_CPU_SUPPORTS_UNALIGNED_ADDR_ACCESS. I am not sure why you got the same amount of errors in interpreter when the macro is 0/1, could you upload the wasm file?

[arvid-norlander]

Hi, since x86-64/x86-32 supports memory access on unaligned address, currently we just do in that way in many places of the runtime implementation, it should be a normal behavior, there is no issue found and it may help reduce the footprint.

I believe you are missing my point here. It may work in practice now. And if you wrote everything in assembly there would be no issues (since the behaviour you are then developing against is that of the actual x86/x86-64 architecture).

However, C/C++ doesn't actually specify behaviour in terms of how the target platform works (this is a common misconception). Instead the standard specifies what compilers can and cannot do in terms of an "abstract machine" defined in the standard. This is what we as C/C++ developers have to conform to when it comes to undefined behaviour.

And the standard says that unaligned access is undefined in terms of this abstract machine. This means that the compiler may do whatever it wants. It might work as you expect, it might not. It might suddenly stop working with a new compiler version, or with different compiler flags. Or even just due to something else changing elsewhere in the program.

Thus, relying on unaligned access working is brittle at best, and I have seen it fail in practice. There is absolutely no guarantees it won't stop working with the next GCC or clang versions due to some new optimization. As far as I know, there are only two safe ways to do unaligned reads in C/C++:

1. Read a byte at a time, and do bitshifting
2. (Ab)use packed structs (note that the struct itself will still be assumed to be aligned, so this is probably tricky in the case of this program).

[wenyongh]

The C/C++ compiler also finally compiles the source code into assembly, AFAIK, most of the x86 instructions support unaligned memory access except few vectorize related instructions, so there seems only when the compiler optimizes the related vectorize operations into aligned memory access instructions can there be a failure occurring. But I believe our code for unaligned memory access is simple enough and there is no vectorize operations, and the compile cannot optimize them into instructions which require aligned memory access, and there are lots of cases tested. We had better keep the current implementation and if there is issue found in new C/C++ compiler, we can track and fix it.

[bnason-nf]

I agree with @arvid-norlander that relying on undefined behavior is risky, and ideally these issues should be addressed by avoiding that behavior. However, since @wenyongh has stated a differing opinion, I've submitted PR #3436 to suppress these issues for the benefit of embedding applications that build with the undefined behavior sanitizer enabled.

[yamt]

except performance critical places, it's simpler to fix them, IMO.

[wenyongh]

Yes, maybe we can define some common functions in core/shared/utils/bh_common.h by using memcpy:

static inline uint16
bh_get_uint16(const uint8 *buf)
{
    uint16 ret;
    bh_memcpy_s(&ret, sizeof(uint16), buf, sizeof(uint16));
    return ret;
}

static inline uint32
bh_get_uint32(const uint8 *buf)
{
    uint32 ret;
    bh_memcpy_s(&ret, sizeof(uint32), buf, sizeof(uint32));
    return ret;
}

static inline uint64
bh_get_uint64(const uint8 *buf)
{
    uint64 ret;
    bh_memcpy_s(&ret, sizeof(uint64), buf, sizeof(uint64));
    return ret;
}

static inline void
bh_set_int16(uint8 *buf, int16 v)
{
    bh_memcpy_s(buf, sizeof(int16), &v, sizeof(int16));
}

static inline void
bh_set_uint32(uint8 *buf, uint32 v)
{
    bh_memcpy_s(buf, sizeof(uint32), &v, sizeof(uint32));
}

static inline void
bh_set_uint64(uint8 *buf, uint64 v)
{
    bh_memcpy_s(buf, sizeof(uint64), &v, sizeof(uint64));
}

And then call them in code like *(uint64 *)p = (uint64)(uintptr_t)target_sym_map[i].symbol_addr;, value = *(intptr_t *)(target_section_addr + (uint32)reloc_offset);

[yamt]

bh_set_int16

why is only bh_set_int16 signed?
otherwise sounds reasonable to me.

iirc, clang is smart enough to turn this kind of functions into simple unaligned load/store in x86. (at least if you use an ordinary memcpy, not bh_ wrapper.)

[wenyongh]

bh_set_int16

why is only bh_set_int16 signed? otherwise sounds reasonable to me.

Sorry for typo, it should be bh_set_uint16.

iirc, clang is smart enough to turn this kind of functions into simple unaligned load/store in x86. (at least if you use an ordinary memcpy, not bh_ wrapper.)

Do you mean we should memcpy instead of bh_memcpy in these functions?

[yamt]

Do you mean we should memcpy instead of bh_memcpy in these functions?

if we end up with using these in performance critical path, maybe. otherwise, i guess it doesn't matter.