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1a51e3a0ae
linux/arch/x86/kernel/head_64.S
Tejun Heo 1a51e3a0ae x86: fold pda into percpu area on SMP 
[ Based on original patch from Christoph Lameter and Mike Travis. ]

Currently pdas and percpu areas are allocated separately.  %gs points
to local pda and percpu area can be reached using pda->data_offset.
This patch folds pda into percpu area.

Due to strange gcc requirement, pda needs to be at the beginning of
the percpu area so that pda->stack_canary is at %gs:40.  To achieve
this, a new percpu output section macro - PERCPU_VADDR_PREALLOC() - is
added and used to reserve pda sized chunk at the start of the percpu
area.

After this change, for boot cpu, %gs first points to pda in the
data.init area and later during setup_per_cpu_areas() gets updated to
point to the actual pda.  This means that setup_per_cpu_areas() need
to reload %gs for CPU0 while clearing pda area for other cpus as cpu0
already has modified it when control reaches setup_per_cpu_areas().

This patch also removes now unnecessary get_local_pda() and its call
sites.

A lot of this patch is taken from Mike Travis' "x86_64: Fold pda into
per cpu area" patch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-16 14:19:46 +01:00

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/*
* linux/arch/x86_64/kernel/head.S -- start in 32bit and switch to 64bit
*
* Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
* Copyright (C) 2000 Pavel Machek <pavel@suse.cz>
* Copyright (C) 2000 Karsten Keil <kkeil@suse.de>
* Copyright (C) 2001,2002 Andi Kleen <ak@suse.de>
* Copyright (C) 2005 Eric Biederman <ebiederm@xmission.com>
*/
#include <linux/linkage.h>
#include <linux/threads.h>
#include <linux/init.h>
#include <asm/desc.h>
#include <asm/segment.h>
#include <asm/pgtable.h>
#include <asm/page.h>
#include <asm/msr.h>
#include <asm/cache.h>
#include <asm/processor-flags.h>
#ifdef CONFIG_PARAVIRT
#include <asm/asm-offsets.h>
#include <asm/paravirt.h>
#else
#define GET_CR2_INTO_RCX movq %cr2, %rcx
#endif
/* we are not able to switch in one step to the final KERNEL ADRESS SPACE
* because we need identity-mapped pages.
*
*/
#define pud_index(x) (((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
L4_PAGE_OFFSET = pgd_index(__PAGE_OFFSET)
L3_PAGE_OFFSET = pud_index(__PAGE_OFFSET)
L4_START_KERNEL = pgd_index(__START_KERNEL_map)
L3_START_KERNEL = pud_index(__START_KERNEL_map)
.text
.section .text.head
.code64
.globl startup_64
startup_64:
/*
* At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1,
* and someone has loaded an identity mapped page table
* for us. These identity mapped page tables map all of the
* kernel pages and possibly all of memory.
*
* %esi holds a physical pointer to real_mode_data.
*
* We come here either directly from a 64bit bootloader, or from
* arch/x86_64/boot/compressed/head.S.
*
* We only come here initially at boot nothing else comes here.
*
* Since we may be loaded at an address different from what we were
* compiled to run at we first fixup the physical addresses in our page
* tables and then reload them.
*/
/* Compute the delta between the address I am compiled to run at and the
* address I am actually running at.
*/
leaq _text(%rip), %rbp
subq $_text - __START_KERNEL_map, %rbp
/* Is the address not 2M aligned? */
movq %rbp, %rax
andl $~PMD_PAGE_MASK, %eax
testl %eax, %eax
jnz bad_address
/* Is the address too large? */
leaq _text(%rip), %rdx
movq $PGDIR_SIZE, %rax
cmpq %rax, %rdx
jae bad_address
/* Fixup the physical addresses in the page table
*/
addq %rbp, init_level4_pgt + 0(%rip)
addq %rbp, init_level4_pgt + (L4_PAGE_OFFSET*8)(%rip)
addq %rbp, init_level4_pgt + (L4_START_KERNEL*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
andq $PMD_PAGE_MASK, %rdi
movq %rdi, %rax
shrq $PUD_SHIFT, %rax
andq $(PTRS_PER_PUD - 1), %rax
jz ident_complete
leaq (level2_spare_pgt - __START_KERNEL_map + _KERNPG_TABLE)(%rbp), %rdx
leaq level3_ident_pgt(%rip), %rbx
movq %rdx, 0(%rbx, %rax, 8)
movq %rdi, %rax
shrq $PMD_SHIFT, %rax
andq $(PTRS_PER_PMD - 1), %rax
leaq __PAGE_KERNEL_IDENT_LARGE_EXEC(%rdi), %rdx
leaq level2_spare_pgt(%rip), %rbx
movq %rdx, 0(%rbx, %rax, 8)
ident_complete:
/*
* Fixup the kernel text+data virtual addresses. Note that
* we might write invalid pmds, when the kernel is relocated
* cleanup_highmap() fixes this up along with the mappings
* beyond _end.
*/
leaq level2_kernel_pgt(%rip), %rdi
leaq 4096(%rdi), %r8
/* See if it is a valid page table entry */
1: testq $1, 0(%rdi)
jz 2f
addq %rbp, 0(%rdi)
/* Go to the next page */
2: addq $8, %rdi
cmp %r8, %rdi
jne 1b
/* Fixup phys_base */
addq %rbp, phys_base(%rip)
#ifdef CONFIG_X86_TRAMPOLINE
addq %rbp, trampoline_level4_pgt + 0(%rip)
addq %rbp, trampoline_level4_pgt + (511*8)(%rip)
#endif
/* Due to ENTRY(), sometimes the empty space gets filled with
* zeros. Better take a jmp than relying on empty space being
* filled with 0x90 (nop)
*/
jmp secondary_startup_64
ENTRY(secondary_startup_64)
/*
* At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1,
* and someone has loaded a mapped page table.
*
* %esi holds a physical pointer to real_mode_data.
*
* We come here either from startup_64 (using physical addresses)
* or from trampoline.S (using virtual addresses).
*
* Using virtual addresses from trampoline.S removes the need
* to have any identity mapped pages in the kernel page table
* after the boot processor executes this code.
*/
/* Enable PAE mode and PGE */
movl $(X86_CR4_PAE | X86_CR4_PGE), %eax
movq %rax, %cr4
/* Setup early boot stage 4 level pagetables. */
movq $(init_level4_pgt - __START_KERNEL_map), %rax
addq phys_base(%rip), %rax
movq %rax, %cr3
/* Ensure I am executing from virtual addresses */
movq $1f, %rax
jmp *%rax
1:
/* Check if nx is implemented */
movl $0x80000001, %eax
cpuid
movl %edx,%edi
/* Setup EFER (Extended Feature Enable Register) */
movl $MSR_EFER, %ecx
rdmsr
btsl $_EFER_SCE, %eax /* Enable System Call */
btl $20,%edi /* No Execute supported? */
jnc 1f
btsl $_EFER_NX, %eax
1: wrmsr /* Make changes effective */
/* Setup cr0 */
#define CR0_STATE (X86_CR0_PE | X86_CR0_MP | X86_CR0_ET | \
X86_CR0_NE | X86_CR0_WP | X86_CR0_AM | \
X86_CR0_PG)
movl $CR0_STATE, %eax
/* Make changes effective */
movq %rax, %cr0
/* Setup a boot time stack */
movq stack_start(%rip),%rsp
/* zero EFLAGS after setting rsp */
pushq $0
popfq
#ifdef CONFIG_SMP
/*
* early_gdt_base should point to the gdt_page in static percpu init
* data area. Computing this requires two symbols - __per_cpu_load
* and per_cpu__gdt_page. As linker can't do no such relocation, do
* it by hand. As early_gdt_descr is manipulated by C code for
* secondary CPUs, this should be done only once for the boot CPU
* when early_gdt_descr_base contains zero.
*/
movq early_gdt_descr_base(%rip), %rax
testq %rax, %rax
jnz 1f
movq $__per_cpu_load, %rax
addq $per_cpu__gdt_page, %rax
movq %rax, early_gdt_descr_base(%rip)
1:
#endif
/*
* We must switch to a new descriptor in kernel space for the GDT
* because soon the kernel won't have access anymore to the userspace
* addresses where we're currently running on. We have to do that here
* because in 32bit we couldn't load a 64bit linear address.
*/
lgdt early_gdt_descr(%rip)
/* set up data segments. actually 0 would do too */
movl $__KERNEL_DS,%eax
movl %eax,%ds
movl %eax,%ss
movl %eax,%es
/*
* We don't really need to load %fs or %gs, but load them anyway
* to kill any stale realmode selectors. This allows execution
* under VT hardware.
*/
movl %eax,%fs
movl %eax,%gs
/* Set up %gs.
*
* On SMP, %gs should point to the per-cpu area. For initial
* boot, make %gs point to the init data section. For a
* secondary CPU,initial_gs should be set to its pda address
* before the CPU runs this code.
*
* On UP, initial_gs points to _boot_cpu_pda and doesn't
* change.
*/
movl $MSR_GS_BASE,%ecx
movq initial_gs(%rip),%rax
movq %rax,%rdx
shrq $32,%rdx
wrmsr
/* esi is pointer to real mode structure with interesting info.
pass it to C */
movl %esi, %edi
/* Finally jump to run C code and to be on real kernel address
* Since we are running on identity-mapped space we have to jump
* to the full 64bit address, this is only possible as indirect
* jump. In addition we need to ensure %cs is set so we make this
* a far return.
*/
movq initial_code(%rip),%rax
pushq $0 # fake return address to stop unwinder
pushq $__KERNEL_CS # set correct cs
pushq %rax # target address in negative space
lretq
/* SMP bootup changes these two */
__REFDATA
.align 8
ENTRY(initial_code)
.quad x86_64_start_kernel
ENTRY(initial_gs)
#ifdef CONFIG_SMP
.quad __per_cpu_load
#else
.quad _boot_cpu_pda
#endif
__FINITDATA
ENTRY(stack_start)
.quad init_thread_union+THREAD_SIZE-8
.word 0
bad_address:
jmp bad_address
.section ".init.text","ax"
#ifdef CONFIG_EARLY_PRINTK
.globl early_idt_handlers
early_idt_handlers:
i = 0
.rept NUM_EXCEPTION_VECTORS
movl $i, %esi
jmp early_idt_handler
i = i + 1
.endr
#endif
ENTRY(early_idt_handler)
#ifdef CONFIG_EARLY_PRINTK
cmpl $2,early_recursion_flag(%rip)
jz 1f
incl early_recursion_flag(%rip)
GET_CR2_INTO_RCX
movq %rcx,%r9
xorl %r8d,%r8d # zero for error code
movl %esi,%ecx # get vector number
# Test %ecx against mask of vectors that push error code.
cmpl $31,%ecx
ja 0f
movl $1,%eax
salq %cl,%rax
testl $0x27d00,%eax
je 0f
popq %r8 # get error code
0: movq 0(%rsp),%rcx # get ip
movq 8(%rsp),%rdx # get cs
xorl %eax,%eax
leaq early_idt_msg(%rip),%rdi
call early_printk
cmpl $2,early_recursion_flag(%rip)
jz 1f
call dump_stack
#ifdef CONFIG_KALLSYMS
leaq early_idt_ripmsg(%rip),%rdi
movq 0(%rsp),%rsi # get rip again
call __print_symbol
#endif
#endif /* EARLY_PRINTK */
1: hlt
jmp 1b
#ifdef CONFIG_EARLY_PRINTK
early_recursion_flag:
.long 0
early_idt_msg:
.asciz "PANIC: early exception %02lx rip %lx:%lx error %lx cr2 %lx\n"
early_idt_ripmsg:
.asciz "RIP %s\n"
#endif /* CONFIG_EARLY_PRINTK */
.previous
.balign PAGE_SIZE
#define NEXT_PAGE(name) \
.balign PAGE_SIZE; \
ENTRY(name)
/* Automate the creation of 1 to 1 mapping pmd entries */
#define PMDS(START, PERM, COUNT) \
i = 0 ; \
.rept (COUNT) ; \
.quad (START) + (i << PMD_SHIFT) + (PERM) ; \
i = i + 1 ; \
.endr
/*
* This default setting generates an ident mapping at address 0x100000
* and a mapping for the kernel that precisely maps virtual address
* 0xffffffff80000000 to physical address 0x000000. (always using
* 2Mbyte large pages provided by PAE mode)
*/
NEXT_PAGE(init_level4_pgt)
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
.org init_level4_pgt + L4_PAGE_OFFSET*8, 0
.quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
.org init_level4_pgt + L4_START_KERNEL*8, 0
/* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
.quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE
NEXT_PAGE(level3_ident_pgt)
.quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE
.fill 511,8,0
NEXT_PAGE(level3_kernel_pgt)
.fill L3_START_KERNEL,8,0
/* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */
.quad level2_kernel_pgt - __START_KERNEL_map + _KERNPG_TABLE
.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.
* Don't set NX because code runs from these pages.
*/
PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD)
NEXT_PAGE(level2_kernel_pgt)
/*
* 512 MB kernel mapping. We spend a full page on this pagetable
* anyway.
*
* The kernel code+data+bss must not be bigger than that.
*
* (NOTE: at +512MB starts the module area, see MODULES_VADDR.
* If you want to increase this then increase MODULES_VADDR
* too.)
*/
PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
KERNEL_IMAGE_SIZE/PMD_SIZE)
NEXT_PAGE(level2_spare_pgt)
.fill 512, 8, 0
#undef PMDS
#undef NEXT_PAGE
.data
.align 16
.globl early_gdt_descr
early_gdt_descr:
.word GDT_ENTRIES*8-1
#ifdef CONFIG_SMP
early_gdt_descr_base:
.quad 0x0000000000000000
#else
.quad per_cpu__gdt_page
#endif
ENTRY(phys_base)
/* This must match the first entry in level2_kernel_pgt */
.quad 0x0000000000000000
#include "../../x86/xen/xen-head.S"
.section .bss, "aw", @nobits
.align L1_CACHE_BYTES
ENTRY(idt_table)
.skip 256 * 16
.section .bss.page_aligned, "aw", @nobits
.align PAGE_SIZE
ENTRY(empty_zero_page)
.skip PAGE_SIZE
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