CRASH: code_api|api.drdecode SEGFAULT/SIGILLs intermittently on aarch64 armv8.0

Created by: joshua-warburton

When run on certain v8.0 hardware, the api.decode test will segfault or SIGILL intermittently. The test harness eats the error message but when the binary is run independently, the fault will appear. Digging into this it appears that the following line in the test triggers the crash

uint written = ((uint(*)(void))generated_code)();

This is running assembly created by the lines above:

instrlist_t *ilist = instrlist_create(GD);
    instr_t *callee = INSTR_CREATE_label(GD);
    instrlist_append(
        ilist,
        XINST_CREATE_move(GD, opnd_create_reg(DR_REG_X1), opnd_create_reg(DR_REG_LR)));
    instrlist_insert_mov_instr_addr(GD, callee, (byte *)ilist, opnd_create_reg(DR_REG_X0),
                                    ilist, NULL, NULL, NULL);
    instrlist_append(ilist, INSTR_CREATE_blr(GD, opnd_create_reg(DR_REG_X0)));
    instrlist_append(ilist, INSTR_CREATE_ret(GD, opnd_create_reg(DR_REG_X1)));
    instrlist_append(ilist, callee);
    instrlist_insert_mov_immed_ptrsz(GD, 0xdeadbeef, opnd_create_reg(DR_REG_X0), ilist,
                                     NULL, NULL, NULL);
    instrlist_append(ilist, XINST_CREATE_return(GD));

I modified the test to print out the instructions that are being generated, which seem to be fine

orr    %xzr %x30 lsl $0x0000000000000000 -> %x1
movz   @0x0000aaab256572c0[2byte] lsl $0x00 -> %x0
movk   %x0 @0x0000aaab256572c0[2byte] lsl $0x10 -> %x0
movk   %x0 @0x0000aaab256572c0[2byte] lsl $0x20 -> %x0
blr    %x0 -> %x30
ret    %x1
<label>
movz   $0xbeef lsl $0x00 -> %x0
movk   %x0 $0xdead lsl $0x10 -> %x0
ret    %x30

Oddly enough, if the binary is moved to an arm v8.2 machine, it runs just fine.

Looking at the dump, it appears the SIGILL comes from

Program terminated with signal SIGILL, Illegal instruction.
#0  0x0000ffff885d3000 in ?? ()

0xffff885d3000      mov x1, x30

To Reproduce

Build the unit tests in debug mode
Run ./suite/tests/bin/api.drdecode until you hit a segfault/sigill on an arm v8.0 machine

Expected behaviour Unit test passes

Versions

most recent version of upstream/master
Ubuntu 18.04.5 LTS
64-bit