I wrote a QEMU plugin for aarch64 where the insn and mem callbacks print out
the specifics of the guest instructions as they are "executed". I expect this
trace stream to be well behaved but it is not. By well-behaved, I expect memory
insns print out some memory details, non-memory insns don't print anything, and
the pc only changes after a control flow instruction. I don't see that gross
correctness about 2% of the time.
1. I'm using qemu at tag v4.2.0 (or master head; it doesn't matter), running
on a x86_64 host.
2. I build qemu using ./configure --disable-sdl --enable-gtk
--enable-plugins --enable-debug --target-list=aarch64-softmmu aarch64-linux-user
3. I execute qemu from its build area build/aarch64-linux-user/qemu-aarch64,
with flags --cpu cortex-a72 and the appropriate args to --plugin ... -d plugin
-D .....
4. I'm emulating a simple C program in linux emulation mode.
5. The resulting qemu execution is valgrind clean (eg, I run qemu under
valgrind) for my little program save for memory leaks I reported a few days ago.
Below is an example of my trace output (the first int printed is the cpu_index,
checked to be always 0). Note that the ldr instruction at 0x41a608 sometimes
reports a memop, but most of the time it doesn't. Note that 0x41a608 is seen,
by trace, running back to back. Note that (bottom of trace) that the movz
instruction reports a memop. (The executed code comes from glibc _dl_aux_init,
executed before main() is called.)
How should this problem be tackled? I can't figure out how to make each tcg
block be exactly 1 guest (aarch64) insn, which is where I'd first start out.
0 0x000000000041a784 0x000000000041a784 0xf1000c3f cmp x1, #3
0 0x000000000041a788 0x000000000041a788 0x54fff401 b.ne #0xfffffffffffffe80
0 0x000000000041a78c 0x000000000041a78c 0x52800033 movz w19, #0x1
0 0x000000000041a790 0x000000000041a790 0xf9400416 ldr x22, [x0, #8] 0 mem {3
0 0 0} 0x0000004000800618
0 0x000000000041a794 0x000000000041a794 0x17ffff9d b #0xfffffffffffffe74
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]! 0 mem
{3 0 0 0} 0x0000004000800620
0 0x000000000041a60c 0x000000000041a60c 0xb4000221 cbz x1, #0x44
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a60c 0x000000000041a60c 0xb4000221 cbz x1, #0x44
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a60c 0x000000000041a60c 0xb4000221 cbz x1, #0x44
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a60c 0x000000000041a60c 0xb4000221 cbz x1, #0x44
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a60c 0x000000000041a60c 0xb4000221 cbz x1, #0x44
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a60c 0x000000000041a60c 0xb4000221 cbz x1, #0x44
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]! 0 mem
{3 0 0 0} 0x0000004000800630
0 0x000000000041a60c 0x000000000041a60c 0xb4000221 cbz x1, #0x44
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a60c 0x000000000041a60c 0xb4000221 cbz x1, #0x44
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a60c 0x000000000041a60c 0xb4000221 cbz x1, #0x44
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a608 0x000000000041a608 0xf8410c01 ldr x1, [x0, #0x10]!
0 0x000000000041a60c 0x000000000041a60c 0xb4000221 cbz x1, #0x44
0 0x000000000041a7d8 0x000000000041a7d8 0x52800035 movz w21, #0x1
0 0x000000000041a7dc 0x000000000041a7dc 0xf9400418 ldr x24, [x0, #8] 0 mem {3
0 0 0} 0x0000004000800638
0 0x000000000041a7e0 0x000000000041a7e0 0x17ffff8a b #0xfffffffffffffe28
0 0x000000000041a7d8 0x000000000041a7d8 0x52800035 movz w21, #0x1 0 mem {3 0 0
0} 0x0000004000800640
