[acpi] Correct the decoding of video mode numbers in wakeup.S

wakeup.S looks at the video mode number from the setup header and
looks to see if it is a VESA mode.  Unfortunately, the decoding is
done incorrectly and it will attempt to frob the VESA BIOS for any
mode number 0x0200 or larger.  Correct this, and remove a bunch of #if
0'd code.

Massive thanks to Jeff Chua for reporting the bug, and suffering
though a large number of experiments in order to track this problem
down.

Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 13 insertions, 34 deletions

diff --git a/arch/x86_64/kernel/acpi/wakeup.S b/arch/x86_64/kernel/acpi/wakeup.S
index 13f1480cbec9..a06f2bcabef9 100644
--- a/arch/x86_64/kernel/acpi/wakeup.S
+++ b/arch/x86_64/kernel/acpi/wakeup.S
@@ -81,7 +81,7 @@ wakeup_code:
         testl   $2, realmode_flags - wakeup_code
         jz      1f
         mov     video_mode - wakeup_code, %ax
-        call    mode_seta
+        call    mode_set
 1:
 
         movw    $0xb800, %ax
@@ -291,52 +291,31 @@ no_longmode:
 #define VIDEO_FIRST_V7 0x0900
 
 # Setting of user mode (AX=mode ID) => CF=success
+
+# For now, we only handle VESA modes (0x0200..0x03ff).  To handle other
+# modes, we should probably compile in the video code from the boot
+# directory.
 .code16
-mode_seta:
+mode_set:
         movw    %ax, %bx
-#if 0
-        cmpb    $0xff, %ah
-        jz      setalias
-
-        testb   $VIDEO_RECALC>>8, %ah
-        jnz     _setrec
-
-        cmpb    $VIDEO_FIRST_RESOLUTION>>8, %ah
-        jnc     setres
-        
-        cmpb    $VIDEO_FIRST_SPECIAL>>8, %ah
-        jz      setspc
-
-        cmpb    $VIDEO_FIRST_V7>>8, %ah
-        jz      setv7
-#endif
-        
-        cmpb    $VIDEO_FIRST_VESA>>8, %ah
-        jnc     check_vesaa
-#if 0   
-        orb     %ah, %ah
-        jz      setmenu
-#endif
-        
-        decb    %ah
-#       jz      setbios                           Add bios modes later
+        subb    $VIDEO_FIRST_VESA>>8, %bh
+        cmpb    $2, %bh
+        jb      check_vesa
 
-setbada:        clc
+setbad:
+        clc
         ret
 
-check_vesaa:
-        subb    $VIDEO_FIRST_VESA>>8, %bh
+check_vesa:
         orw     $0x4000, %bx                    # Use linear frame buffer
         movw    $0x4f02, %ax                    # VESA BIOS mode set call
         int     $0x10
         cmpw    $0x004f, %ax                    # AL=4f if implemented
-        jnz     _setbada                                # AH=0 if OK
+        jnz     setbad                          # AH=0 if OK
 
         stc
         ret
 
-_setbada: jmp setbada
-
 wakeup_stack_begin:     # Stack grows down
 
 .org    0xff0