x86: initial fixmap support

Needed to get fixed virtual address for USB debug and earlycon with mmio.
Signed-off-by: Eric W. Biderman <ebiderman@xmisson.com>
Signed-off-by: Yinghai Lu <yinghai.lu@sun.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/i386/kernel/head.S

@@ -168,6 +168,12 @@ page_pde_offset = (__PAGE_OFFSET >> 20);
 .section .init.text,"ax",@progbits
 #endif
 
+	/* Do an early initialization of the fixmap area */
+	movl $(swapper_pg_dir - __PAGE_OFFSET), %edx
+	movl $(swapper_pg_pmd - __PAGE_OFFSET), %eax
+	addl $0x007, %eax			/* 0x007 = PRESENT+RW+USER */
+	movl %eax, 4092(%edx)
+
 #ifdef CONFIG_SMP
 ENTRY(startup_32_smp)
 	cld
@@ -507,6 +513,8 @@ ENTRY(_stext)
 .section ".bss.page_aligned","w"
 ENTRY(swapper_pg_dir)
 	.fill 1024,4,0
+ENTRY(swapper_pg_pmd)
+	.fill 1024,4,0
 ENTRY(empty_zero_page)
 	.fill 4096,1,0
 

arch/x86_64/kernel/head.S

@@ -73,7 +73,11 @@ startup_64:
 	addq	%rbp, init_level4_pgt + (511*8)(%rip)
 
 	addq	%rbp, level3_ident_pgt + 0(%rip)
+
 	addq	%rbp, level3_kernel_pgt + (510*8)(%rip)
+	addq	%rbp, level3_kernel_pgt + (511*8)(%rip)
+
+	addq	%rbp, level2_fixmap_pgt + (506*8)(%rip)
 
 	/* Add an Identity mapping if I am above 1G */
 	leaq	_text(%rip), %rdi
@@ -314,7 +318,16 @@ NEXT_PAGE(level3_kernel_pgt)
 	.fill	510,8,0
 	/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
 	.quad	level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE
-	.fill	1,8,0
+	.quad	level2_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
+
+NEXT_PAGE(level2_fixmap_pgt)
+	.fill	506,8,0
+	.quad	level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
+	/* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
+	.fill	5,8,0
+
+NEXT_PAGE(level1_fixmap_pgt)
+	.fill	512,8,0
 
 NEXT_PAGE(level2_ident_pgt)
 	/* Since I easily can, map the first 1G.