RE: [Qemu-devel] Re: strange crash on FreeBSD-current/amd64 (pointertruncation?)

[Gwenole Beauchesne]

On Fri, 2 Feb 2007, Paul Robinson wrote:

> But the T0, T1, and T2 registers are being saved for the benefit of the
> host not the target.

FWIW, I use the following patch for Virtual Box on x86_64. The proper fix
would be to not globally allocate registers for the whole program but only
for the micro-ops. Then, make the necessary save/restore around the
gen_func call.

--- vbox-1.3.3/src/recompiler/new/cpu-exec.c.64bit-fixes        2007-01-23 
10:30:18.000000000 +0100
+++ vbox-1.3.3/src/recompiler/new/cpu-exec.c    2007-02-02 18:16:19.000000000 
+0100
@@ -228,7 +228,23 @@ static inline TranslationBlock *tb_find_
 
 int cpu_exec(CPUState *env1)
 {
-    int saved_T0, saved_T1, saved_T2;
+    /* Preserve callee-saved registers */
+#ifdef AREG0
+    register unsigned long reg_AREG0 asm(AREG0);
+    volatile unsigned long saved_AREG0;
+#endif
+#ifdef AREG1
+    register unsigned long reg_AREG1 asm(AREG1);
+    volatile unsigned long saved_AREG1;
+#endif
+#ifdef AREG2
+    register unsigned long reg_AREG2 asm(AREG2);
+    volatile unsigned long saved_AREG2;
+#endif
+#ifdef AREG3
+    register unsigned long reg_AREG3 asm(AREG3);
+    volatile unsigned long saved_AREG3;
+#endif
     CPUState *saved_env;
 #ifdef reg_EAX
     int saved_EAX;
@@ -319,10 +335,17 @@ int cpu_exec(CPUState *env1)
     /* first we save global registers */
     saved_env = env;
     env = env1;
-    saved_T0 = T0;
-    saved_T1 = T1;
-#if defined(reg_T2)
-    saved_T2 = T2;
+#ifdef AREG0
+    saved_AREG0 = reg_AREG0;
+#endif
+#ifdef AREG1
+    saved_AREG1 = reg_AREG1;
+#endif
+#ifdef AREG2
+    saved_AREG2 = reg_AREG2;
+#endif
+#ifdef AREG3
+    saved_AREG3 = reg_AREG3;
 #endif
 #if defined(__sparc__) && !defined(HOST_SOLARIS)
     /* we also save i7 because longjmp may not restore it */
@@ -656,9 +679,18 @@ int cpu_exec(CPUState *env1)
 #else
 #error unsupported target CPU
 #endif
-    T0 = saved_T0;
-    T1 = saved_T1;
-    T2 = saved_T2;
+#ifdef AREG0
+    reg_AREG0 = saved_AREG0;
+#endif
+#ifdef AREG1
+    reg_AREG1 = saved_AREG1;
+#endif
+#ifdef AREG2
+    reg_AREG2 = saved_AREG2;
+#endif
+#ifdef AREG3
+    reg_AREG3 = saved_AREG3;
+#endif
     env = saved_env;
     return ret;
 }