x86/asm: Replace magic numbers in GDT descriptors, preparations

We'd like to replace all the magic numbers in various GDT descriptors
with new, semantically meaningful, symbolic values.

In order to be able to verify that the change doesn't cause any actual
changes to the compiled binary code, I've split the change into two
patches:

 - Part 1 (this commit): everything _but_ actually replacing the numbers
 - Part 2 (the following commit): _only_ replacing the numbers

The reason we need this split for verification is that including new
headers causes some spurious changes to the object files, mostly line
number changes in the debug info but occasionally other subtle codegen
changes.

Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20231219151200.2878271-3-vegard.nossum@oracle.com

Author: vegard

arch/x86/boot/pm.c

@@ -11,6 +11,7 @@
  */
 
 #include "boot.h"
+#include <asm/desc_defs.h>
 #include <asm/segment.h>
 
 /*

arch/x86/include/asm/desc_defs.h

@@ -144,6 +144,7 @@ struct gate_struct {
 
 typedef struct gate_struct gate_desc;
 
+#ifndef _SETUP
 static inline unsigned long gate_offset(const gate_desc *g)
 {
 #ifdef CONFIG_X86_64
@@ -158,6 +159,7 @@ static inline unsigned long gate_segment(const gate_desc *g)
 {
 	return g->segment;
 }
+#endif
 
 struct desc_ptr {
 	unsigned short size;

arch/x86/kernel/cpu/common.c

@@ -204,25 +204,17 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {
 	 * They code segments and data segments have fixed 64k limits,
 	 * the transfer segment sizes are set at run time.
 	 */
-	/* 32-bit code */
 	[GDT_ENTRY_PNPBIOS_CS32]	= GDT_ENTRY_INIT(0x409a, 0, 0xffff),
-	/* 16-bit code */
 	[GDT_ENTRY_PNPBIOS_CS16]	= GDT_ENTRY_INIT(0x009a, 0, 0xffff),
-	/* 16-bit data */
 	[GDT_ENTRY_PNPBIOS_DS]		= GDT_ENTRY_INIT(0x0092, 0, 0xffff),
-	/* 16-bit data */
 	[GDT_ENTRY_PNPBIOS_TS1]		= GDT_ENTRY_INIT(0x0092, 0, 0),
-	/* 16-bit data */
 	[GDT_ENTRY_PNPBIOS_TS2]		= GDT_ENTRY_INIT(0x0092, 0, 0),
 	/*
 	 * The APM segments have byte granularity and their bases
 	 * are set at run time.  All have 64k limits.
 	 */
-	/* 32-bit code */
 	[GDT_ENTRY_APMBIOS_BASE]	= GDT_ENTRY_INIT(0x409a, 0, 0xffff),
-	/* 16-bit code */
 	[GDT_ENTRY_APMBIOS_BASE+1]	= GDT_ENTRY_INIT(0x009a, 0, 0xffff),
-	/* data */
 	[GDT_ENTRY_APMBIOS_BASE+2]	= GDT_ENTRY_INIT(0x4092, 0, 0xffff),
 
 	[GDT_ENTRY_ESPFIX_SS]		= GDT_ENTRY_INIT(0xc092, 0, 0xfffff),

arch/x86/platform/pvh/head.S

@@ -11,6 +11,7 @@
 #include <linux/elfnote.h>
 #include <linux/init.h>
 #include <linux/linkage.h>
+#include <asm/desc_defs.h>
 #include <asm/segment.h>
 #include <asm/asm.h>
 #include <asm/boot.h>

arch/x86/realmode/rm/reboot.S

@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 #include <linux/linkage.h>
+#include <asm/desc_defs.h>
 #include <asm/segment.h>
 #include <asm/page_types.h>
 #include <asm/processor-flags.h>