X86EMU: handle CPUID instruction

After trying to switch from X to VT (or just quit) the video-amd driver
attempts to issue INT 10/0 to go to mode 3 (VGA).  The emulator, running
the BIOS code, would then spit out:

        c000:0282: A2 ILLEGAL EXTENDED X86 OPCODE!

The opcode was 0F A2, or CPUID; it was not implemented in the emulator.
This simple patch, against 1.3.0.0, handles the CPUID instruction in one of
two ways:
 1) if ran on __i386__ or __x86_64__ then it calls the CPUID instruction
     directly.
 2) if ran elsewhere it returns a canned 486dx4 set of values for
     function 1.

This fix allows the video-amd driver to switch back to console mode,
with the GSW BIOS.

Thanks to Symbio Technologies for funding my work, and ThinCan for
providing hardware :)

Signed-off-by: Bart Trojanowski <bart@jukie.net>
Acked-by: Eric Anholt <eric@anholt.net>

4 files changed, 161 insertions, 1 deletions

diff --git a/hw/xfree86/x86emu/ops2.c b/hw/xfree86/x86emu/ops2.c
index 8c6c53539..324de8ad8 100644
--- a/hw/xfree86/x86emu/ops2.c
+++ b/hw/xfree86/x86emu/ops2.c
@@ -328,6 +328,20 @@ static void x86emuOp2_pop_FS(u8 X86EMU_UNUSED(op2))
 }
 
 /****************************************************************************
+REMARKS: CPUID takes EAX/ECX as inputs, writes EAX/EBX/ECX/EDX as output
+Handles opcode 0x0f,0xa2
+****************************************************************************/
+static void x86emuOp2_cpuid(u8 X86EMU_UNUSED(op2))
+{
+    START_OF_INSTR();
+    DECODE_PRINTF("CPUID\n");
+    TRACE_AND_STEP();
+    cpuid();
+    DECODE_CLEAR_SEGOVR();
+    END_OF_INSTR();
+}
+
+/****************************************************************************
 REMARKS:
 Handles opcode 0x0f,0xa3
 ****************************************************************************/
@@ -2734,7 +2748,7 @@ void (*x86emu_optab2[256])(u8) =
 
 /*  0xa0 */ x86emuOp2_push_FS,
 /*  0xa1 */ x86emuOp2_pop_FS,
-/*  0xa2 */ x86emuOp2_illegal_op,
+/*  0xa2 */ x86emuOp2_cpuid,
 /*  0xa3 */ x86emuOp2_bt_R,
 /*  0xa4 */ x86emuOp2_shld_IMM,
 /*  0xa5 */ x86emuOp2_shld_CL,
diff --git a/hw/xfree86/x86emu/prim_ops.c b/hw/xfree86/x86emu/prim_ops.c
index b9e7257ca..b42cdc0a5 100644
--- a/hw/xfree86/x86emu/prim_ops.c
+++ b/hw/xfree86/x86emu/prim_ops.c
@@ -102,6 +102,12 @@
 #define	PRIM_OPS_NO_REDEFINE_ASM
 #include "x86emu/x86emui.h"
 
+#if defined(__GNUC__)
+# if defined (__i386__) || defined(__i386) || defined(__AMD64__) || defined(__x86_64__) || defined(__amd64__)
+#  include "x86emu/prim_x86_gcc.h"
+# endif
+#endif
+
 /*------------------------- Global Variables ------------------------------*/
 
 static u32 x86emu_parity_tab[8] =
@@ -2654,3 +2660,63 @@ DB(	if (CHECK_SP_ACCESS())
     return res;
 }
 
+/****************************************************************************
+REMARKS:
+CPUID takes EAX/ECX as inputs, writes EAX/EBX/ECX/EDX as output
+****************************************************************************/
+void cpuid (void)
+{
+    u32 feature = M.x86.R_EAX;
+
+#ifdef X86EMU_HAS_HW_CPUID
+    /* If the platform allows it, we will base our values on the real
+     * results from the CPUID instruction.  We limit support to the
+     * first two features, and the results of those are sanitized.
+     */
+    if (feature <= 1)
+	hw_cpuid(&M.x86.R_EAX, &M.x86.R_EBX, &M.x86.R_ECX, &M.x86.R_EDX);
+#endif
+
+    switch (feature) {
+    case 0:
+        /* Regardless if we have real data from the hardware, the emulator
+	 * will only support upto feature 1, which we set in register EAX.
+	 * Registers EBX:EDX:ECX contain a string identifying the CPU.
+	 */
+        M.x86.R_EAX = 1;
+#ifndef X86EMU_HAS_HW_CPUID
+        /* EBX:EDX:ECX = "GenuineIntel" */
+        M.x86.R_EBX = 0x756e6547;
+        M.x86.R_EDX = 0x49656e69;
+        M.x86.R_ECX = 0x6c65746e;
+#endif
+        break;
+    case 1:
+#ifndef X86EMU_HAS_HW_CPUID
+        /* If we don't have x86 compatible hardware, we return values from an
+	 * Intel 486dx4; which was one of the first processors to have CPUID.
+	 */
+        M.x86.R_EAX = 0x00000480;
+        M.x86.R_EBX = 0x00000000;
+        M.x86.R_ECX = 0x00000000;
+        M.x86.R_EDX = 0x00000002;	/* VME */
+#else
+        /* In the case that we have hardware CPUID instruction, we make sure
+	 * that the features reported are limited to TSC and VME.
+	 */
+        M.x86.R_EDX &= 0x00000012;
+#endif
+        break;
+    default:
+        /* Finally, we don't support any additional features.  Most CPUs
+	 * return all zeros when queried for invalid or unsupported feature
+	 * numbers.
+	 */
+        M.x86.R_EAX = 0;
+        M.x86.R_EBX = 0;
+        M.x86.R_ECX = 0;
+        M.x86.R_EDX = 0;
+        break;
+    }
+}
+
diff --git a/hw/xfree86/x86emu/x86emu/prim_ops.h b/hw/xfree86/x86emu/x86emu/prim_ops.h
index bea8357e4..6ac2a29f6 100644
--- a/hw/xfree86/x86emu/x86emu/prim_ops.h
+++ b/hw/xfree86/x86emu/x86emu/prim_ops.h
@@ -133,6 +133,7 @@ void    push_word (u16 w);
 void    push_long (u32 w);
 u16     pop_word (void);
 u32		pop_long (void);
+void    cpuid (void);
 
 #ifdef  __cplusplus
 }                       			/* End of "C" linkage for C++   	*/
diff --git a/hw/xfree86/x86emu/x86emu/prim_x86_gcc.h b/hw/xfree86/x86emu/x86emu/prim_x86_gcc.h
new file mode 100644
index 000000000..af61e2023
--- /dev/null
+++ b/hw/xfree86/x86emu/x86emu/prim_x86_gcc.h
@@ -0,0 +1,79 @@
+/****************************************************************************
+*
+* Inline helpers for x86emu
+*
+* Copyright (C) 2008 Bart Trojanowski, Symbio Technologies, LLC
+*
+*  ========================================================================
+*
+*  Permission to use, copy, modify, distribute, and sell this software and
+*  its documentation for any purpose is hereby granted without fee,
+*  provided that the above copyright notice appear in all copies and that
+*  both that copyright notice and this permission notice appear in
+*  supporting documentation, and that the name of the authors not be used
+*  in advertising or publicity pertaining to distribution of the software
+*  without specific, written prior permission.  The authors makes no
+*  representations about the suitability of this software for any purpose.
+*  It is provided "as is" without express or implied warranty.
+*
+*  THE AUTHORS DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+*  INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+*  EVENT SHALL THE AUTHORS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+*  CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
+*  USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+*  OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+*  PERFORMANCE OF THIS SOFTWARE.
+*
+*  ========================================================================
+*
+* Language:     GNU C
+* Environment:  GCC on i386 or x86-64
+* Developer:    Bart Trojanowski
+*
+* Description:  This file defines a few x86 macros that can be used by the
+*               emulator to execute native instructions.
+*
+*               For PIC vs non-PIC code refer to:
+*               http://sam.zoy.org/blog/2007-04-13-shlib-with-non-pic-code-have-inline-assembly-and-pic-mix-well
+*
+****************************************************************************/
+#ifndef __X86EMU_PRIM_X86_GCC_H
+#define __X86EMU_PRIM_X86_GCC_H
+
+#include "x86emu/types.h"
+
+#if !defined(__GNUC__) || !(defined (__i386__) || defined(__i386) || defined(__AMD64__) || defined(__x86_64__) || defined(__amd64__))
+#error This file is intended to be used by gcc on i386 or x86-64 system
+#endif
+
+#if defined(__PIC__) && defined(__i386__)
+
+#define X86EMU_HAS_HW_CPUID 1
+static inline void hw_cpuid (u32 *a, u32 *b, u32 *c, u32 *d)
+{
+    __asm__ __volatile__ ("pushl %%ebx      \n\t"
+                          "cpuid            \n\t"
+                          "movl %%ebx, %1   \n\t"
+                          "popl %%ebx       \n\t"
+                          : "=a" (*a), "=r" (*b),
+                            "=c" (*c), "=d" (*d)
+                          : "a" (*a), "c" (*c)
+                          : "cc");
+}
+
+#else // ! (__PIC__ && __i386__)
+
+#define x86EMU_HAS_HW_CPUID 1
+static inline void hw_cpuid (u32 *a, u32 *b, u32 *c, u32 *d)
+{
+    __asm__ __volatile__ ("cpuid"
+                          : "=a" (*a), "=b" (*b),
+                            "=c" (*c), "=d" (*d)
+                          : "a" (*a), "c" (*c)
+                          : "cc");
+}
+
+#endif // __PIC__ && __i386__
+
+
+#endif // __X86EMU_PRIM_X86_GCC_H