Re: [Qemu-devel] and now bus error for i386 guest

["Blue Swirl" <blauwirbel@gmail.com>]

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The first problem was gcc flag -mflat, removing that made the code better.

Then there were these global register mangles. I made a wrapper around
setjmp and longjmp and now the emulators can execute several blocks
until crashing. Some helper calls don't work.

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Index: qemu/cpu-exec.c
===================================================================
--- qemu.orig/cpu-exec.c	2007-12-06 10:21:29.000000000 +0000
+++ qemu/cpu-exec.c	2007-12-06 14:21:18.000000000 +0000
@@ -40,6 +40,56 @@
 //#define DEBUG_EXEC
 //#define DEBUG_SIGNAL
 
+#define SAVE_GLOBALS()
+#define RESTORE_GLOBALS()
+
+#if defined(__sparc__) && !defined(HOST_SOLARIS)
+#include <features.h>
+#if defined(__GLIBC__) && ((__GLIBC__ < 2) || \
+                           ((__GLIBC__ == 2) && (__GLIBC_MINOR__ <= 90)))
+// Work around ugly bugs in glibc that mangle global register contents
+
+static volatile void *saved_env;
+static volatile long saved_t0, saved_t1, saved_t2, saved_i7;
+#undef SAVE_GLOBALS
+#define SAVE_GLOBALS() do {                                     \
+        saved_env = env;                                        \
+        saved_t0 = T0;                                          \
+        saved_t1 = T1;                                          \
+        saved_t2 = T2;                                          \
+        asm volatile ("mov %%i7, %0" : "=r" (saved_i7));        \
+    } while(0)
+
+#undef RESTORE_GLOBALS
+#define RESTORE_GLOBALS() do {                                  \
+        env = (void *)saved_env;                                \
+        T0 = saved_t0;                                          \
+        T1 = saved_t1;                                          \
+        T2 = saved_t2;                                          \
+        asm volatile ("mov %0, %%i7" : : "r" (saved_i7));       \
+    } while(0)
+
+static int sparc_setjmp(jmp_buf buf)
+{
+    int ret;
+
+    SAVE_GLOBALS();
+    ret = setjmp(buf);
+    RESTORE_GLOBALS();
+    return ret;
+}
+#undef setjmp
+#define setjmp(jmp_buf) sparc_setjmp(jmp_buf)
+
+static void sparc_longjmp(jmp_buf buf, int val)
+{
+    SAVE_GLOBALS();
+    longjmp(buf, val);
+}
+#define longjmp(jmp_buf, val) sparc_longjmp(jmp_buf, val)
+#endif
+#endif
+
 void cpu_loop_exit(void)
 {
     /* NOTE: the register at this point must be saved by hand because
@@ -133,7 +183,9 @@
     tb->tc_ptr = tc_ptr;
     tb->cs_base = cs_base;
     tb->flags = flags;
+    SAVE_GLOBALS();
     cpu_gen_code(env, tb, CODE_GEN_MAX_SIZE, &code_gen_size);
+    RESTORE_GLOBALS();
     code_gen_ptr = (void *)(((unsigned long)code_gen_ptr + code_gen_size + CODE_GEN_ALIGN - 1) & ~(CODE_GEN_ALIGN - 1));
 
     /* check next page if needed */
@@ -232,11 +284,7 @@
     return tb;
 }
 
-#if defined(__sparc__) && !defined(HOST_SOLARIS)
-#define BREAK_CHAIN tmp_T0 = 0
-#else
 #define BREAK_CHAIN T0 = 0
-#endif
 
 /* main execution loop */
 
@@ -249,10 +297,6 @@
     uint32_t *saved_regwptr;
 #endif
 #endif
-#if defined(__sparc__) && !defined(HOST_SOLARIS)
-    int saved_i7;
-    target_ulong tmp_T0;
-#endif
     int ret, interrupt_request;
     void (*gen_func)(void);
     TranslationBlock *tb;
@@ -267,11 +311,6 @@
 #define SAVE_HOST_REGS 1
 #include "hostregs_helper.h"
     env = env1;
-#if defined(__sparc__) && !defined(HOST_SOLARIS)
-    /* we also save i7 because longjmp may not restore it */
-    asm volatile ("mov %%i7, %0" : "=r" (saved_i7));
-#endif
-
     env_to_regs();
 #if defined(TARGET_I386)
     /* put eflags in CPU temporary format */
@@ -380,10 +419,7 @@
 
             T0 = 0; /* force lookup of first TB */
             for(;;) {
-#if defined(__sparc__) && !defined(HOST_SOLARIS)
-                /* g1 can be modified by some libc? functions */
-                tmp_T0 = T0;
-#endif
+                SAVE_GLOBALS();
                 interrupt_request = env->interrupt_request;
                 if (__builtin_expect(interrupt_request, 0)
 #if defined(TARGET_I386)
@@ -597,9 +633,7 @@
                             lookup_symbol(tb->pc));
                 }
 #endif
-#if defined(__sparc__) && !defined(HOST_SOLARIS)
-                T0 = tmp_T0;
-#endif
+                RESTORE_GLOBALS();
                 /* see if we can patch the calling TB. When the TB
                    spans two pages, we cannot safely do a direct
                    jump. */
@@ -646,6 +680,7 @@
 #else
                 gen_func();
 #endif
+                SAVE_GLOBALS();
                 env->current_tb = NULL;
                 /* reset soft MMU for next block (it can currently
                    only be set by a memory fault) */
@@ -695,9 +730,6 @@
 #endif
 
     /* restore global registers */
-#if defined(__sparc__) && !defined(HOST_SOLARIS)
-    asm volatile ("mov %0, %%i7" : : "r" (saved_i7));
-#endif
 #include "hostregs_helper.h"
 
     /* fail safe : never use cpu_single_env outside cpu_exec() */
Index: qemu/Makefile.target
===================================================================
--- qemu.orig/Makefile.target	2007-12-06 10:22:55.000000000 +0000
+++ qemu/Makefile.target	2007-12-06 12:26:28.000000000 +0000
@@ -161,7 +161,7 @@
     OP_CFLAGS+=-fno-omit-frame-pointer
   else
     BASE_CFLAGS+=-ffixed-g1 -ffixed-g6
-    HELPER_CFLAGS=$(CFLAGS) -ffixed-i0 -mflat
+    HELPER_CFLAGS=$(CFLAGS) -ffixed-i0
     # -static is used to avoid g1/g3 usage by the dynamic linker
     BASE_LDFLAGS+=-Wl,-T,$(SRC_PATH)/$(ARCH).ld -static
   endif