Josh Triplett wrote: > I'm attempting to run cross-compiled programs with qemu-ppc. Basic > statically-linked programs work perfectly. However, if I attempt to run > non-static programs or threaded programs, or if I attempt to call > clone() with the CLONE_VM flag set, I get an invalid data memory access. > > Threaded programs get an error when calling pthread_create, with an > invalid data memory access at 0x00000018. A simple test program using > clone with CLONE_VM gets an invalid data memory access at 0x00000008. > Non-static programs get an invalid data memory access at various > addresses around 0x0de00000, before ever reaching main().
I worked with pbrook on #qemu to debug this issue. The problem turns out to be that qemu's do_fork function on PowerPC zeroes out r7-r31 in the new CPU state structure after a clone, which it should not do, as the child's registers should match the parent; it also does not zero register r3, which holds the return value and should be zero in the child. I've prepared and attached a patch which should solve this problem. - Josh Triplett
diff -Naur qemu-0.7.0.orig/linux-user/syscall.c qemu-0.7.0/linux-user/syscall.c
--- qemu-0.7.0.orig/linux-user/syscall.c 2005-10-21 19:56:04.000000000 -0700
+++ qemu-0.7.0/linux-user/syscall.c 2005-10-21 20:02:20.000000000 -0700
@@ -1560,11 +1560,7 @@
if (!newsp)
newsp = env->gpr[1];
new_env->gpr[1] = newsp;
- {
- int i;
- for (i = 7; i < 32; i++)
- new_env->gpr[i] = 0;
- }
+ new_env->gpr[3] = 0;
#else
#error unsupported target CPU
#endif
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