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Diffstat (limited to 'arch/i386/kernel/head.S')
| -rw-r--r-- | arch/i386/kernel/head.S | 521 |
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 */ + |
