From f84926efca2f871fa557cccee36f0f773ec7190b Mon Sep 17 00:00:00 2001
From: Li-Ta Lo <ollie@lanl.gov>
Date: Thu, 4 Nov 2004 18:36:06 +0000
Subject: [PATCH] tell people that the segment descriptors are different for
 ROMCC and GCC code.

git-svn-id: svn://svn.coreboot.org/coreboot/trunk@1740 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1
---
 src/arch/i386/lib/c_start.S   | 43 ++++++++++++++++++-----------------
 src/cpu/x86/16bit/entry16.inc |  8 +++----
 src/cpu/x86/32bit/entry32.inc |  9 +++++---
 src/cpu/x86/lapic/secondary.S |  2 +-
 4 files changed, 33 insertions(+), 29 deletions(-)

diff --git a/src/arch/i386/lib/c_start.S b/src/arch/i386/lib/c_start.S
index 2e397f8847..ccd0127dae 100644
--- a/src/arch/i386/lib/c_start.S
+++ b/src/arch/i386/lib/c_start.S
@@ -216,7 +216,7 @@ int_hand:
 	popl	%ecx
 	popl	%edx
 	popl	%ebx
-	popl	%ebp /* Ignore saved %esp value */
+	popl	%ebp	/* Ignore saved %esp value */
 	popl	%ebp
 	popl	%esi
 	popl	%edi
@@ -241,49 +241,50 @@ gdb_stub_breakpoint:
 
 	.globl gdt, gdt_end, gdt_limit, idtarg
 
-gdt_limit = gdt_end - gdt - 1 /* compute the table limit */
+gdt_limit = gdt_end - gdt - 1	/* compute the table limit */
 gdtaddr:
 	.word	gdt_limit
-	.long	gdt                /* we know the offset */
+	.long	gdt		/* we know the offset */
 
 	 .data
+
+	/* This is the gdt for GCC part of LinuxBIOS.
+	 * It is different from the gdt in ROMCC/ASM part of LinuxBIOS
+	 * which is defined in entry32.inc */
 gdt:
-// selgdt 0
+	/* selgdt 0, unused */
 	.word	0x0000, 0x0000		/* dummy */
 	.byte	0x00, 0x00, 0x00, 0x00
 
-// selgdt 8
+	/* selgdt 8, unused */
 	.word	0x0000, 0x0000		/* dummy */
 	.byte	0x00, 0x00, 0x00, 0x00
 
-// selgdt 0x10 
-/* flat code segment */
+	/* selgdt 0x10, flat code segment */
 	.word	0xffff, 0x0000		
 	.byte	0x00, 0x9b, 0xcf, 0x00	
-	
-//selgdt 0x18
-/* flat data segment */
+
+	/* selgdt 0x18, flat data segment */
 	.word	0xffff, 0x0000		
 	.byte	0x00, 0x93, 0xcf, 0x00	
 
-//selgdt 0x20
+	/* selgdt 0x20, unused */
 	.word	0x0000, 0x0000		/* dummy */
 	.byte	0x00, 0x00, 0x00, 0x00
 
 #if defined(CONFIG_LEGACY_VGABIOS) && (CONFIG_LEGACY_VGABIOS == 1)
-	// from monty:
-	/* 0x00009a00,0000ffffULL,   20h: 16-bit 64k code at 0x00000000 */
-        /* 0x00009200,0000ffffULL    28h: 16-bit 64k data at 0x00000000 */
-// selgdt 0x28
-/*16-bit 64k code at 0x00000000 */
-	.word 0xffff, 0x0000
-	.byte 0, 0x9a, 0, 0
+	/* from monty:
+	 * 0x00009a00,0000ffffULL,   20h: 16-bit 64k code at 0x00000000
+         * 0x00009200,0000ffffULL    28h: 16-bit 64k data at 0x00000000 */
 
-// selgdt 0x30
-/*16-bit 64k data at 0x00000000 */
+	/* selgdt 0x28, 16-bit 64k code at 0x00000000 */
+	.word 0xffff, 0x0000
+	.byte 0x00, 0x9a, 0x00, 0x00
+
+	/* selgdt 0x30, 16-bit 64k data at 0x00000000 */
 	.word 0xffff, 0x0000
 	.byte 0, 0x92, 0, 0
-#endif // defined(CONFIG_VGABIOS) && (CONFIG_VGABIOS == 1)
+#endif /* defined(CONFIG_VGABIOS) && (CONFIG_VGABIOS == 1) */
 gdt_end:
 
 idtarg:
diff --git a/src/cpu/x86/16bit/entry16.inc b/src/cpu/x86/16bit/entry16.inc
index 61726d8ad9..674315fbd2 100644
--- a/src/cpu/x86/16bit/entry16.inc
+++ b/src/cpu/x86/16bit/entry16.inc
@@ -108,10 +108,10 @@ _start:
 	/* Now that we are in protected mode jump to a 32 bit code segment. */
 	data32	ljmp	$ROM_CODE_SEG, $__protected_start
 
-/** The gdt has a 4 Gb code segment at 0x10, and a 4 GB data segment
- * at 0x18; these are Linux-compatible. 
- */
-
+	/**
+	 * The gdt is defined in entry32.inc, it has a 4 Gb code segment
+	 * at 0x08, and a 4 GB data segment at 0x10;
+	 */
 .align	4
 .globl gdtptr16
 gdtptr16:
diff --git a/src/cpu/x86/32bit/entry32.inc b/src/cpu/x86/32bit/entry32.inc
index 3d30a3f85f..724aed32eb 100644
--- a/src/cpu/x86/32bit/entry32.inc
+++ b/src/cpu/x86/32bit/entry32.inc
@@ -8,17 +8,20 @@
 	.align	4
 .globl gdtptr
 
+	/* This is the gdt for ROMCC/ASM part of LinuxBIOS.
+	 * It is different from the gdt in GCC part of LinuxBIOS
+	 * which is defined in c_start.S */
 gdt:
 gdtptr:
 	.word	gdt_end - gdt -1 /* compute the table limit */
 	.long	gdt		 /* we know the offset */
 	.word	0
 
-/* flat code segment */
+	/* selgdt 0x08, flat code segment */
 	.word	0xffff, 0x0000		
 	.byte	0x00, 0x9b, 0xcf, 0x00	
-	
-/* flat data segment */
+
+	/* selgdt 0x10,flat data segment */
 	.word	0xffff, 0x0000		
 	.byte	0x00, 0x93, 0xcf, 0x00	
 
diff --git a/src/cpu/x86/lapic/secondary.S b/src/cpu/x86/lapic/secondary.S
index 5185021c3c..b212f43b38 100644
--- a/src/cpu/x86/lapic/secondary.S
+++ b/src/cpu/x86/lapic/secondary.S
@@ -26,7 +26,7 @@ _secondary_start:
 	orl	$0x60000001, %eax /* CD, NW, PE = 1 */
 	movl	%eax, %cr0
 
-	ljmpl $0x10, $1f
+	ljmpl	$0x10, $1f
 1:	
 	.code32
 	movw	$0x18, %ax