Re: GNU Mach cpu detection fix

[Alfred M. Szmidt]

Roland, OK to commit?

Guillem added EFL_VI and EFL_VIP for the sake of completion.

EFL_AC and EFL_ID were supposedly added by Thomas in 1997; but that
never got commited for some reason, so the only thing that should be
changed is the ChangeLog entry to note this, something like:

(EFL_AC, EFL_ID): Bits finally added.

would do it.  The rest looks OK to me.

2004-11-22  Guillem Jover  <guillem@hadrons.org>

        * i386/i386/locore.S (discover_x86_cpu_type): Enable function.
        Enable ID flag for Cyrix CPU. Use %ebp to save the stack pointer.
        Restore EFLAGS just after its last usage.
        * i386/i386at/model_dep.c (c_boot_entry): Enable use of
        discover_x86_cpu_type. Remove hardcoded cpu_type assignment.
        * i386/include/mach/i386/eflags.h
        (EFL_AC, EFL_VI, EFL_VIP, EFL_ID): New bits.


diff -Naur i386/i386/locore.S i386/i386/locore.S
--- i386/i386/locore.S  2001-10-07 21:47:15.000000000 +0200
+++ i386/i386/locore.S  2004-11-21 21:40:21.000000000 +0100
@@ -1144,13 +1144,16 @@
        jmp     _take_trap              /* treat as a trap */
 
 
-#if 0
 /* Discover what kind of cpu we have; return the family number
    (3, 4, 5, 6, for 386, 486, 586, 686 respectively).  */
 ENTRY(discover_x86_cpu_type)
-       movl    %esp,%edx               /* Save stack pointer */
+       pushl   %ebp                    /* Save frame pointer */
+       movl    %esp,%ebp               /* Save stack pointer */
        and     $~0x3,%esp              /* Align stack pointer */
 
+       inb     $0xe8,%al               /* Enable ID flag for Cyrix CPU ... */
+       andb    $0x80,%al               /* ... in CCR4 reg bit7 */
+       outb    %al,$0xe8
        pushfl                          /* Fetch flags ... */
        popl    %eax                    /*  ... into eax */
        movl    %eax,%ecx               /* Save original flags for return */
@@ -1159,6 +1162,8 @@
        popfl                           /*  ... In EFLAGS */
        pushfl                          /* Fetch flags back ... */
        popl    %eax                    /*  ... into eax */
+       pushl   %ecx                    /* From ecx... */
+       popfl                           /* ... restore original flags */
 
        xorl    %ecx,%eax               /* See if any bits didn't change */
        testl   $EFL_AC,%eax            /* Test AC bit */
@@ -1178,11 +1183,9 @@
        shrl    $8,%eax                 /* Slide family bits down */
        andl    $15,%eax                /* And select them */
 
-9:     pushl   %ecx                    /* From ecx... */
-       popfl                           /* ... restore original flags */
-       movl    %edx,%esp               /* Restore stack pointer */
+9:     movl    %ebp,%esp               /* Restore stack pointer */
+       popl    %ebp                    /* Restore frame pointer */
        ret                             /* And return */
-#endif
 
 
 /**/
diff -Naur i386/i386at/model_dep.c i386/i386at/model_dep.c
--- i386/i386at/model_dep.c     2002-05-23 03:54:57.000000000 +0200
+++ i386/i386at/model_dep.c     2004-11-21 21:41:09.000000000 +0100
@@ -372,7 +372,6 @@
        machine_slot[0].running = TRUE;
        machine_slot[0].cpu_subtype = CPU_SUBTYPE_AT386;
 
-#if 0
        switch (discover_x86_cpu_type ())
          {
          case 3:
@@ -389,10 +388,6 @@
            machine_slot[0].cpu_type = CPU_TYPE_PENTIUMPRO;
            break;
          }
-#else
-       machine_slot[0].cpu_type = CPU_TYPE_I386;
-#endif
-
 
        /*
         * Start the system.
diff -Naur i386/include/mach/i386/eflags.h i386/include/mach/i386/eflags.h
--- i386/include/mach/i386/eflags.h     2001-04-05 08:39:21.000000000 +0200
+++ i386/include/mach/i386/eflags.h     2004-11-21 21:39:13.000000000 +0100
@@ -45,5 +45,9 @@
 #define        EFL_NT          0x00004000              /* nested task */
 #define        EFL_RF          0x00010000              /* resume without 
tracing */
 #define        EFL_VM          0x00020000              /* virtual 8086 mode */
+#define        EFL_AC          0x00040000              /* alignment check */
+#define        EFL_VI          0x00080000              /* virtual interrupt */
+#define        EFL_VIP         0x00100000              /* virtual interrupt 
pending */
+#define        EFL_ID          0x00200000              /* cpuid available */
 
 #endif /* _MACH_I386_EFLAGS_H_ */