[PTLsim-devel] Self-modifying code detection issues?

Tue Mar 13 14:54:30 EDT 2007

I have a small test case that is triggering SMC checks -> flushing the
pipeline. I compile this on a 32bit machine and use PTLsim classic on
a 64bit machine.

int num;
int main() {
  ptlcall_switch_to_sim();
  num++;
  ptlcall_switch_to_native();
  return num;
}

The num++ is triggering the "store" side of SMC, and the instructions
following it is the "load" that triggers the SMC detect.

Here's some lines from ptlsim.log..

num++

  0x80483fa: ldd          tr0 = [zero,0x8049f44]
  0x80483fa: addd         tr0 = tr0,1 [zco]
  0x80483fa: std.         mem = [zero,0x8049f44],tr0

the instruction (*) immediately following num++

  0x8048401: ldd          tr0 = [zero,0x8049f3c]

(*) being fetched

3 fetch  rip 0x8048401: ldd          tr0 = [zero,0x8049f3c] (BB
0xf76c1000 uopid 3; SOM)

(*) detecting SMC

3 smcdet rob 3  : self-modifying code at rip 0x8048401 detected (mfn
was dirty); invalidate and retry [EOM #1]

The address that num++ modifies is 0x8049f44 and the rip of (*) is
0x8048401, so they're 6,979 bytes apart which is more than a PAGE_SIZE
(4096).

If I stick ".zero 4096" at the end of main in the asm file, it stops
detecting SMC.

-- 
Ed