aboutsummaryrefslogtreecommitdiff
path: root/arch/i386/kernel/head.S
diff options
context:
space:
mode:
Diffstat (limited to 'arch/i386/kernel/head.S')
-rw-r--r--arch/i386/kernel/head.S521
1 files changed, 521 insertions, 0 deletions
diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
new file mode 100644
index 000000000000..d273fd746192
--- /dev/null
+++ b/arch/i386/kernel/head.S
@@ -0,0 +1,521 @@
+/*
+ * linux/arch/i386/kernel/head.S -- the 32-bit startup code.
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ *
+ * Enhanced CPU detection and feature setting code by Mike Jagdis
+ * and Martin Mares, November 1997.
+ */
+
+.text
+#include <linux/config.h>
+#include <linux/threads.h>
+#include <linux/linkage.h>
+#include <asm/segment.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/desc.h>
+#include <asm/cache.h>
+#include <asm/thread_info.h>
+#include <asm/asm_offsets.h>
+#include <asm/setup.h>
+
+/*
+ * References to members of the new_cpu_data structure.
+ */
+
+#define X86 new_cpu_data+CPUINFO_x86
+#define X86_VENDOR new_cpu_data+CPUINFO_x86_vendor
+#define X86_MODEL new_cpu_data+CPUINFO_x86_model
+#define X86_MASK new_cpu_data+CPUINFO_x86_mask
+#define X86_HARD_MATH new_cpu_data+CPUINFO_hard_math
+#define X86_CPUID new_cpu_data+CPUINFO_cpuid_level
+#define X86_CAPABILITY new_cpu_data+CPUINFO_x86_capability
+#define X86_VENDOR_ID new_cpu_data+CPUINFO_x86_vendor_id
+
+/*
+ * This is how much memory *in addition to the memory covered up to
+ * and including _end* we need mapped initially. We need one bit for
+ * each possible page, but only in low memory, which means
+ * 2^32/4096/8 = 128K worst case (4G/4G split.)
+ *
+ * Modulo rounding, each megabyte assigned here requires a kilobyte of
+ * memory, which is currently unreclaimed.
+ *
+ * This should be a multiple of a page.
+ */
+#define INIT_MAP_BEYOND_END (128*1024)
+
+
+/*
+ * 32-bit kernel entrypoint; only used by the boot CPU. On entry,
+ * %esi points to the real-mode code as a 32-bit pointer.
+ * CS and DS must be 4 GB flat segments, but we don't depend on
+ * any particular GDT layout, because we load our own as soon as we
+ * can.
+ */
+ENTRY(startup_32)
+
+/*
+ * Set segments to known values.
+ */
+ cld
+ lgdt boot_gdt_descr - __PAGE_OFFSET
+ movl $(__BOOT_DS),%eax
+ movl %eax,%ds
+ movl %eax,%es
+ movl %eax,%fs
+ movl %eax,%gs
+
+/*
+ * Clear BSS first so that there are no surprises...
+ * No need to cld as DF is already clear from cld above...
+ */
+ xorl %eax,%eax
+ movl $__bss_start - __PAGE_OFFSET,%edi
+ movl $__bss_stop - __PAGE_OFFSET,%ecx
+ subl %edi,%ecx
+ shrl $2,%ecx
+ rep ; stosl
+
+/*
+ * Initialize page tables. This creates a PDE and a set of page
+ * tables, which are located immediately beyond _end. The variable
+ * init_pg_tables_end is set up to point to the first "safe" location.
+ * Mappings are created both at virtual address 0 (identity mapping)
+ * and PAGE_OFFSET for up to _end+sizeof(page tables)+INIT_MAP_BEYOND_END.
+ *
+ * Warning: don't use %esi or the stack in this code. However, %esp
+ * can be used as a GPR if you really need it...
+ */
+page_pde_offset = (__PAGE_OFFSET >> 20);
+
+ movl $(pg0 - __PAGE_OFFSET), %edi
+ movl $(swapper_pg_dir - __PAGE_OFFSET), %edx
+ movl $0x007, %eax /* 0x007 = PRESENT+RW+USER */
+10:
+ leal 0x007(%edi),%ecx /* Create PDE entry */
+ movl %ecx,(%edx) /* Store identity PDE entry */
+ movl %ecx,page_pde_offset(%edx) /* Store kernel PDE entry */
+ addl $4,%edx
+ movl $1024, %ecx
+11:
+ stosl
+ addl $0x1000,%eax
+ loop 11b
+ /* End condition: we must map up to and including INIT_MAP_BEYOND_END */
+ /* bytes beyond the end of our own page tables; the +0x007 is the attribute bits */
+ leal (INIT_MAP_BEYOND_END+0x007)(%edi),%ebp
+ cmpl %ebp,%eax
+ jb 10b
+ movl %edi,(init_pg_tables_end - __PAGE_OFFSET)
+
+#ifdef CONFIG_SMP
+ xorl %ebx,%ebx /* This is the boot CPU (BSP) */
+ jmp 3f
+
+/*
+ * Non-boot CPU entry point; entered from trampoline.S
+ * We can't lgdt here, because lgdt itself uses a data segment, but
+ * we know the trampoline has already loaded the boot_gdt_table GDT
+ * for us.
+ */
+ENTRY(startup_32_smp)
+ cld
+ movl $(__BOOT_DS),%eax
+ movl %eax,%ds
+ movl %eax,%es
+ movl %eax,%fs
+ movl %eax,%gs
+
+/*
+ * New page tables may be in 4Mbyte page mode and may
+ * be using the global pages.
+ *
+ * NOTE! If we are on a 486 we may have no cr4 at all!
+ * So we do not try to touch it unless we really have
+ * some bits in it to set. This won't work if the BSP
+ * implements cr4 but this AP does not -- very unlikely
+ * but be warned! The same applies to the pse feature
+ * if not equally supported. --macro
+ *
+ * NOTE! We have to correct for the fact that we're
+ * not yet offset PAGE_OFFSET..
+ */
+#define cr4_bits mmu_cr4_features-__PAGE_OFFSET
+ movl cr4_bits,%edx
+ andl %edx,%edx
+ jz 6f
+ movl %cr4,%eax # Turn on paging options (PSE,PAE,..)
+ orl %edx,%eax
+ movl %eax,%cr4
+
+ btl $5, %eax # check if PAE is enabled
+ jnc 6f
+
+ /* Check if extended functions are implemented */
+ movl $0x80000000, %eax
+ cpuid
+ cmpl $0x80000000, %eax
+ jbe 6f
+ mov $0x80000001, %eax
+ cpuid
+ /* Execute Disable bit supported? */
+ btl $20, %edx
+ jnc 6f
+
+ /* Setup EFER (Extended Feature Enable Register) */
+ movl $0xc0000080, %ecx
+ rdmsr
+
+ btsl $11, %eax
+ /* Make changes effective */
+ wrmsr
+
+6:
+ /* This is a secondary processor (AP) */
+ xorl %ebx,%ebx
+ incl %ebx
+
+3:
+#endif /* CONFIG_SMP */
+
+/*
+ * Enable paging
+ */
+ movl $swapper_pg_dir-__PAGE_OFFSET,%eax
+ movl %eax,%cr3 /* set the page table pointer.. */
+ movl %cr0,%eax
+ orl $0x80000000,%eax
+ movl %eax,%cr0 /* ..and set paging (PG) bit */
+ ljmp $__BOOT_CS,$1f /* Clear prefetch and normalize %eip */
+1:
+ /* Set up the stack pointer */
+ lss stack_start,%esp
+
+/*
+ * Initialize eflags. Some BIOS's leave bits like NT set. This would
+ * confuse the debugger if this code is traced.
+ * XXX - best to initialize before switching to protected mode.
+ */
+ pushl $0
+ popfl
+
+#ifdef CONFIG_SMP
+ andl %ebx,%ebx
+ jz 1f /* Initial CPU cleans BSS */
+ jmp checkCPUtype
+1:
+#endif /* CONFIG_SMP */
+
+/*
+ * start system 32-bit setup. We need to re-do some of the things done
+ * in 16-bit mode for the "real" operations.
+ */
+ call setup_idt
+
+/*
+ * Copy bootup parameters out of the way.
+ * Note: %esi still has the pointer to the real-mode data.
+ */
+ movl $boot_params,%edi
+ movl $(PARAM_SIZE/4),%ecx
+ cld
+ rep
+ movsl
+ movl boot_params+NEW_CL_POINTER,%esi
+ andl %esi,%esi
+ jnz 2f # New command line protocol
+ cmpw $(OLD_CL_MAGIC),OLD_CL_MAGIC_ADDR
+ jne 1f
+ movzwl OLD_CL_OFFSET,%esi
+ addl $(OLD_CL_BASE_ADDR),%esi
+2:
+ movl $saved_command_line,%edi
+ movl $(COMMAND_LINE_SIZE/4),%ecx
+ rep
+ movsl
+1:
+checkCPUtype:
+
+ movl $-1,X86_CPUID # -1 for no CPUID initially
+
+/* check if it is 486 or 386. */
+/*
+ * XXX - this does a lot of unnecessary setup. Alignment checks don't
+ * apply at our cpl of 0 and the stack ought to be aligned already, and
+ * we don't need to preserve eflags.
+ */
+
+ movb $3,X86 # at least 386
+ pushfl # push EFLAGS
+ popl %eax # get EFLAGS
+ movl %eax,%ecx # save original EFLAGS
+ xorl $0x240000,%eax # flip AC and ID bits in EFLAGS
+ pushl %eax # copy to EFLAGS
+ popfl # set EFLAGS
+ pushfl # get new EFLAGS
+ popl %eax # put it in eax
+ xorl %ecx,%eax # change in flags
+ pushl %ecx # restore original EFLAGS
+ popfl
+ testl $0x40000,%eax # check if AC bit changed
+ je is386
+
+ movb $4,X86 # at least 486
+ testl $0x200000,%eax # check if ID bit changed
+ je is486
+
+ /* get vendor info */
+ xorl %eax,%eax # call CPUID with 0 -> return vendor ID
+ cpuid
+ movl %eax,X86_CPUID # save CPUID level
+ movl %ebx,X86_VENDOR_ID # lo 4 chars
+ movl %edx,X86_VENDOR_ID+4 # next 4 chars
+ movl %ecx,X86_VENDOR_ID+8 # last 4 chars
+
+ orl %eax,%eax # do we have processor info as well?
+ je is486
+
+ movl $1,%eax # Use the CPUID instruction to get CPU type
+ cpuid
+ movb %al,%cl # save reg for future use
+ andb $0x0f,%ah # mask processor family
+ movb %ah,X86
+ andb $0xf0,%al # mask model
+ shrb $4,%al
+ movb %al,X86_MODEL
+ andb $0x0f,%cl # mask mask revision
+ movb %cl,X86_MASK
+ movl %edx,X86_CAPABILITY
+
+is486: movl $0x50022,%ecx # set AM, WP, NE and MP
+ jmp 2f
+
+is386: movl $2,%ecx # set MP
+2: movl %cr0,%eax
+ andl $0x80000011,%eax # Save PG,PE,ET
+ orl %ecx,%eax
+ movl %eax,%cr0
+
+ call check_x87
+ incb ready
+ lgdt cpu_gdt_descr
+ lidt idt_descr
+ ljmp $(__KERNEL_CS),$1f
+1: movl $(__KERNEL_DS),%eax # reload all the segment registers
+ movl %eax,%ss # after changing gdt.
+
+ movl $(__USER_DS),%eax # DS/ES contains default USER segment
+ movl %eax,%ds
+ movl %eax,%es
+
+ xorl %eax,%eax # Clear FS/GS and LDT
+ movl %eax,%fs
+ movl %eax,%gs
+ lldt %ax
+ cld # gcc2 wants the direction flag cleared at all times
+#ifdef CONFIG_SMP
+ movb ready, %cl
+ cmpb $1,%cl
+ je 1f # the first CPU calls start_kernel
+ # all other CPUs call initialize_secondary
+ call initialize_secondary
+ jmp L6
+1:
+#endif /* CONFIG_SMP */
+ call start_kernel
+L6:
+ jmp L6 # main should never return here, but
+ # just in case, we know what happens.
+
+/*
+ * We depend on ET to be correct. This checks for 287/387.
+ */
+check_x87:
+ movb $0,X86_HARD_MATH
+ clts
+ fninit
+ fstsw %ax
+ cmpb $0,%al
+ je 1f
+ movl %cr0,%eax /* no coprocessor: have to set bits */
+ xorl $4,%eax /* set EM */
+ movl %eax,%cr0
+ ret
+ ALIGN
+1: movb $1,X86_HARD_MATH
+ .byte 0xDB,0xE4 /* fsetpm for 287, ignored by 387 */
+ ret
+
+/*
+ * setup_idt
+ *
+ * sets up a idt with 256 entries pointing to
+ * ignore_int, interrupt gates. It doesn't actually load
+ * idt - that can be done only after paging has been enabled
+ * and the kernel moved to PAGE_OFFSET. Interrupts
+ * are enabled elsewhere, when we can be relatively
+ * sure everything is ok.
+ *
+ * Warning: %esi is live across this function.
+ */
+setup_idt:
+ lea ignore_int,%edx
+ movl $(__KERNEL_CS << 16),%eax
+ movw %dx,%ax /* selector = 0x0010 = cs */
+ movw $0x8E00,%dx /* interrupt gate - dpl=0, present */
+
+ lea idt_table,%edi
+ mov $256,%ecx
+rp_sidt:
+ movl %eax,(%edi)
+ movl %edx,4(%edi)
+ addl $8,%edi
+ dec %ecx
+ jne rp_sidt
+ ret
+
+/* This is the default interrupt "handler" :-) */
+ ALIGN
+ignore_int:
+ cld
+ pushl %eax
+ pushl %ecx
+ pushl %edx
+ pushl %es
+ pushl %ds
+ movl $(__KERNEL_DS),%eax
+ movl %eax,%ds
+ movl %eax,%es
+ pushl 16(%esp)
+ pushl 24(%esp)
+ pushl 32(%esp)
+ pushl 40(%esp)
+ pushl $int_msg
+ call printk
+ addl $(5*4),%esp
+ popl %ds
+ popl %es
+ popl %edx
+ popl %ecx
+ popl %eax
+ iret
+
+/*
+ * Real beginning of normal "text" segment
+ */
+ENTRY(stext)
+ENTRY(_stext)
+
+/*
+ * BSS section
+ */
+.section ".bss.page_aligned","w"
+ENTRY(swapper_pg_dir)
+ .fill 1024,4,0
+ENTRY(empty_zero_page)
+ .fill 4096,1,0
+
+/*
+ * This starts the data section.
+ */
+.data
+
+ENTRY(stack_start)
+ .long init_thread_union+THREAD_SIZE
+ .long __BOOT_DS
+
+ready: .byte 0
+
+int_msg:
+ .asciz "Unknown interrupt or fault at EIP %p %p %p\n"
+
+/*
+ * The IDT and GDT 'descriptors' are a strange 48-bit object
+ * only used by the lidt and lgdt instructions. They are not
+ * like usual segment descriptors - they consist of a 16-bit
+ * segment size, and 32-bit linear address value:
+ */
+
+.globl boot_gdt_descr
+.globl idt_descr
+.globl cpu_gdt_descr
+
+ ALIGN
+# early boot GDT descriptor (must use 1:1 address mapping)
+ .word 0 # 32 bit align gdt_desc.address
+boot_gdt_descr:
+ .word __BOOT_DS+7
+ .long boot_gdt_table - __PAGE_OFFSET
+
+ .word 0 # 32-bit align idt_desc.address
+idt_descr:
+ .word IDT_ENTRIES*8-1 # idt contains 256 entries
+ .long idt_table
+
+# boot GDT descriptor (later on used by CPU#0):
+ .word 0 # 32 bit align gdt_desc.address
+cpu_gdt_descr:
+ .word GDT_ENTRIES*8-1
+ .long cpu_gdt_table
+
+ .fill NR_CPUS-1,8,0 # space for the other GDT descriptors
+
+/*
+ * The boot_gdt_table must mirror the equivalent in setup.S and is
+ * used only for booting.
+ */
+ .align L1_CACHE_BYTES
+ENTRY(boot_gdt_table)
+ .fill GDT_ENTRY_BOOT_CS,8,0
+ .quad 0x00cf9a000000ffff /* kernel 4GB code at 0x00000000 */
+ .quad 0x00cf92000000ffff /* kernel 4GB data at 0x00000000 */
+
+/*
+ * The Global Descriptor Table contains 28 quadwords, per-CPU.
+ */
+ .align PAGE_SIZE_asm
+ENTRY(cpu_gdt_table)
+ .quad 0x0000000000000000 /* NULL descriptor */
+ .quad 0x0000000000000000 /* 0x0b reserved */
+ .quad 0x0000000000000000 /* 0x13 reserved */
+ .quad 0x0000000000000000 /* 0x1b reserved */
+ .quad 0x0000000000000000 /* 0x20 unused */
+ .quad 0x0000000000000000 /* 0x28 unused */
+ .quad 0x0000000000000000 /* 0x33 TLS entry 1 */
+ .quad 0x0000000000000000 /* 0x3b TLS entry 2 */
+ .quad 0x0000000000000000 /* 0x43 TLS entry 3 */
+ .quad 0x0000000000000000 /* 0x4b reserved */
+ .quad 0x0000000000000000 /* 0x53 reserved */
+ .quad 0x0000000000000000 /* 0x5b reserved */
+
+ .quad 0x00cf9a000000ffff /* 0x60 kernel 4GB code at 0x00000000 */
+ .quad 0x00cf92000000ffff /* 0x68 kernel 4GB data at 0x00000000 */
+ .quad 0x00cffa000000ffff /* 0x73 user 4GB code at 0x00000000 */
+ .quad 0x00cff2000000ffff /* 0x7b user 4GB data at 0x00000000 */
+
+ .quad 0x0000000000000000 /* 0x80 TSS descriptor */
+ .quad 0x0000000000000000 /* 0x88 LDT descriptor */
+
+ /* Segments used for calling PnP BIOS */
+ .quad 0x00c09a0000000000 /* 0x90 32-bit code */
+ .quad 0x00809a0000000000 /* 0x98 16-bit code */
+ .quad 0x0080920000000000 /* 0xa0 16-bit data */
+ .quad 0x0080920000000000 /* 0xa8 16-bit data */
+ .quad 0x0080920000000000 /* 0xb0 16-bit data */
+ /*
+ * The APM segments have byte granularity and their bases
+ * and limits are set at run time.
+ */
+ .quad 0x00409a0000000000 /* 0xb8 APM CS code */
+ .quad 0x00009a0000000000 /* 0xc0 APM CS 16 code (16 bit) */
+ .quad 0x0040920000000000 /* 0xc8 APM DS data */
+
+ .quad 0x0000920000000000 /* 0xd0 - ESPFIX 16-bit SS */
+ .quad 0x0000000000000000 /* 0xd8 - unused */
+ .quad 0x0000000000000000 /* 0xe0 - unused */
+ .quad 0x0000000000000000 /* 0xe8 - unused */
+ .quad 0x0000000000000000 /* 0xf0 - unused */
+ .quad 0x0000000000000000 /* 0xf8 - GDT entry 31: double-fault TSS */
+