/* * 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 #include #include #include #include #include #include #include #include #include #include #include /* Physical address */ #define pa(X) ((X) - __PAGE_OFFSET) /* * 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.) * - enough space to map all low memory, which means * (2^32/4096) / 1024 pages (worst case, non PAE) * (2^32/4096) / 512 + 4 pages (worst case for PAE) * - a few pages for allocator use before the kernel pagetable has * been set up * * Modulo rounding, each megabyte assigned here requires a kilobyte of * memory, which is currently unreclaimed. * * This should be a multiple of a page. */ LOW_PAGES = 1<<(32-PAGE_SHIFT_asm) /* * To preserve the DMA pool in PAGEALLOC kernels, we'll allocate * pagetables from above the 16MB DMA limit, so we'll have to set * up pagetables 16MB more (worst-case): */ #ifdef CONFIG_DEBUG_PAGEALLOC LOW_PAGES = LOW_PAGES + 0x1000000 #endif #if PTRS_PER_PMD > 1 PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PMD) + PTRS_PER_PGD #else PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PGD) #endif BOOTBITMAP_SIZE = LOW_PAGES / 8 ALLOCATOR_SLOP = 4 INIT_MAP_BEYOND_END = BOOTBITMAP_SIZE + (PAGE_TABLE_SIZE + ALLOCATOR_SLOP)*PAGE_SIZE_asm /* * 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. */ .section .text.head,"ax",@progbits ENTRY(startup_32) /* test KEEP_SEGMENTS flag to see if the bootloader is asking us to not reload segments */ testb $(1<<6), BP_loadflags(%esi) jnz 2f /* * Set segments to known values. */ lgdt pa(boot_gdt_descr) movl $(__BOOT_DS),%eax movl %eax,%ds movl %eax,%es movl %eax,%fs movl %eax,%gs 2: /* * Clear BSS first so that there are no surprises... */ cld xorl %eax,%eax movl $pa(__bss_start),%edi movl $pa(__bss_stop),%ecx subl %edi,%ecx shrl $2,%ecx rep ; stosl /* * Copy bootup parameters out of the way. * Note: %esi still has the pointer to the real-mode data. * With the kexec as boot loader, parameter segment might be loaded beyond * kernel image and might not even be addressable by early boot page tables. * (kexec on panic case). Hence copy out the parameters before initializing * page tables. */ movl $pa(boot_params),%edi movl $(PARAM_SIZE/4),%ecx cld rep movsl movl pa(boot_params) + NEW_CL_POINTER,%esi andl %esi,%esi jz 1f # No comand line movl $pa(boot_command_line),%edi movl $(COMMAND_LINE_SIZE/4),%ecx rep movsl 1: #ifdef CONFIG_PARAVIRT /* This is can only trip for a broken bootloader... */ cmpw $0x207, pa(boot_params + BP_version) jb default_entry /* Paravirt-compatible boot parameters. Look to see what architecture we're booting under. */ movl pa(boot_params + BP_hardware_subarch), %eax cmpl $num_subarch_entries, %eax jae bad_subarch movl pa(subarch_entries)(,%eax,4), %eax subl $__PAGE_OFFSET, %eax jmp *%eax bad_subarch: WEAK(lguest_entry) WEAK(xen_entry) /* Unknown implementation; there's really nothing we can do at this point. */ ud2a __INITDATA subarch_entries: .long default_entry /* normal x86/PC */ .long lguest_entry /* lguest hypervisor */ .long xen_entry /* Xen hypervisor */ num_subarch_entries = (. - subarch_entries) / 4 .previous #endif /* CONFIG_PARAVIRT */ /* * 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. * * Note that the stack is not yet set up! */ #define PTE_ATTR 0x007 /* PRESENT+RW+USER */ #define PDE_ATTR 0x067 /* PRESENT+RW+USER+DIRTY+ACCESSED */ #define PGD_ATTR 0x001 /* PRESENT (no other attributes) */ default_entry: #ifdef CONFIG_X86_PAE /* * In PAE mode swapper_pg_dir is statically defined to contain enough * entries to cover the VMSPLIT option (that is the top 1, 2 or 3 * entries). The identity mapping is handled by pointing two PGD * entries to the first kernel PMD. * * Note the upper half of each PMD or PTE are always zero at * this stage. */ #define KPMDS ((0x100000000-__PAGE_OFFSET) >> 30) /* Number of kernel PMDs */ xorl %ebx,%ebx /* %ebx is kept at zero */ movl $pa(pg0), %edi movl $pa(swapper_pg_pmd), %edx movl $PTE_ATTR, %eax 10: leal PDE_ATTR(%edi),%ecx /* Create PMD entry */ movl %ecx,(%edx) /* Store PMD entry */ /* Upper half already zero */ addl $8,%edx movl $512,%ecx 11: stosl xchgl %eax,%ebx stosl xchgl %eax,%ebx 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. */ leal (INIT_MAP_BEYOND_END+PTE_ATTR)(%edi),%ebp cmpl %ebp,%eax jb 10b 1: movl %edi,pa(init_pg_tables_end) /* Do early initialization of the fixmap area */ movl $pa(swapper_pg_fixmap)+PDE_ATTR,%eax movl %eax,pa(swapper_pg_pmd+0x1000*KPMDS-8) #else /* Not PAE */ page_pde_offset = (__PAGE_OFFSET >> 20); movl $pa(pg0), %edi movl $pa(swapper_pg_dir), %edx movl $PTE_ATTR, %eax 10: leal PDE_ATTR(%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+PTE_ATTR)(%edi),%ebp cmpl %ebp,%eax jb 10b movl %edi,pa(init_pg_tables_end) /* Do early initialization of the fixmap area */ movl $pa(swapper_pg_fixmap)+PDE_ATTR,%eax movl %eax,pa(swapper_pg_dir+0xffc) #endif 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 for us. * * If cpu hotplug is not supported then this code can go in init section * which will be freed later */ #ifndef CONFIG_HOTPLUG_CPU .section .init.text,"ax",@progbits #endif #ifdef CONFIG_SMP ENTRY(startup_32_smp) cld movl $(__BOOT_DS),%eax movl %eax,%ds movl %eax,%es movl %eax,%fs movl %eax,%gs #endif /* CONFIG_SMP */ 3: /* * 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 pa(mmu_cr4_features) 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: /* * Enable paging */ movl $pa(swapper_pg_dir),%eax movl %eax,%cr3 /* set the page table pointer.. */ movl %cr0,%eax orl $X86_CR0_PG,%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 cmpb $0, ready 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 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 lgdt early_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 %eax,%fs # gets reset once there's real percpu movl $(__USER_DS),%eax # DS/ES contains default USER segment movl %eax,%ds movl %eax,%es xorl %eax,%eax # Clear GS and LDT movl %eax,%gs lldt %ax cld # gcc2 wants the direction flag cleared at all times pushl $0 # fake return address for unwinder #ifdef CONFIG_SMP movb ready, %cl movb $1, ready cmpb $0,%cl # the first CPU calls start_kernel je 1f movl $(__KERNEL_PERCPU), %eax movl %eax,%fs # set this cpu's percpu jmp initialize_secondary # all other CPUs call initialize_secondary 1: #endif /* CONFIG_SMP */ jmp start_kernel /* * 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 .macro set_early_handler handler,trapno lea \handler,%edx movl $(__KERNEL_CS << 16),%eax movw %dx,%ax movw $0x8E00,%dx /* interrupt gate - dpl=0, present */ lea idt_table,%edi movl %eax,8*\trapno(%edi) movl %edx,8*\trapno+4(%edi) .endm set_early_handler handler=early_divide_err,trapno=0 set_early_handler handler=early_illegal_opcode,trapno=6 set_early_handler handler=early_protection_fault,trapno=13 set_early_handler handler=early_page_fault,trapno=14 ret early_divide_err: xor %edx,%edx pushl $0 /* fake errcode */ jmp early_fault early_illegal_opcode: movl $6,%edx pushl $0 /* fake errcode */ jmp early_fault early_protection_fault: movl $13,%edx jmp early_fault early_page_fault: movl $14,%edx jmp early_fault early_fault: cld #ifdef CONFIG_PRINTK pusha movl $(__KERNEL_DS),%eax movl %eax,%ds movl %eax,%es cmpl $2,early_recursion_flag je hlt_loop incl early_recursion_flag movl %cr2,%eax pushl %eax pushl %edx /* trapno */ pushl $fault_msg #ifdef CONFIG_EARLY_PRINTK call early_printk #else call printk #endif #endif call dump_stack hlt_loop: hlt jmp hlt_loop /* This is the default interrupt "handler" :-) */ ALIGN ignore_int: cld #ifdef CONFIG_PRINTK pushl %eax pushl %ecx pushl %edx pushl %es pushl %ds movl $(__KERNEL_DS),%eax movl %eax,%ds movl %eax,%es cmpl $2,early_recursion_flag je hlt_loop incl early_recursion_flag pushl 16(%esp) pushl 24(%esp) pushl 32(%esp) pushl 40(%esp) pushl $int_msg #ifdef CONFIG_EARLY_PRINTK call early_printk #else call printk #endif addl $(5*4),%esp popl %ds popl %es popl %edx popl %ecx popl %eax #endif iret .section .text /* * Real beginning of normal "text" segment */ ENTRY(stext) ENTRY(_stext) /* * BSS section */ .section ".bss.page_aligned","wa" .align PAGE_SIZE_asm #ifdef CONFIG_X86_PAE swapper_pg_pmd: .fill 1024*KPMDS,4,0 #else ENTRY(swapper_pg_dir) .fill 1024,4,0 #endif swapper_pg_fixmap: .fill 1024,4,0 ENTRY(empty_zero_page) .fill 4096,1,0 /* * This starts the data section. */ #ifdef CONFIG_X86_PAE .section ".data.page_aligned","wa" /* Page-aligned for the benefit of paravirt? */ .align PAGE_SIZE_asm ENTRY(swapper_pg_dir) .long pa(swapper_pg_pmd+PGD_ATTR),0 /* low identity map */ # if KPMDS == 3 .long pa(swapper_pg_pmd+PGD_ATTR),0 .long pa(swapper_pg_pmd+PGD_ATTR+0x1000),0 .long pa(swapper_pg_pmd+PGD_ATTR+0x2000),0 # elif KPMDS == 2 .long 0,0 .long pa(swapper_pg_pmd+PGD_ATTR),0 .long pa(swapper_pg_pmd+PGD_ATTR+0x1000),0 # elif KPMDS == 1 .long 0,0 .long 0,0 .long pa(swapper_pg_pmd+PGD_ATTR),0 # else # error "Kernel PMDs should be 1, 2 or 3" # endif .align PAGE_SIZE_asm /* needs to be page-sized too */ #endif .data ENTRY(stack_start) .long init_thread_union+THREAD_SIZE .long __BOOT_DS ready: .byte 0 early_recursion_flag: .long 0 int_msg: .asciz "Unknown interrupt or fault at EIP %p %p %p\n" fault_msg: .ascii \ /* fault info: */ "BUG: Int %d: CR2 %p\n" \ /* pusha regs: */ " EDI %p ESI %p EBP %p ESP %p\n" \ " EBX %p EDX %p ECX %p EAX %p\n" \ /* fault frame: */ " err %p EIP %p CS %p flg %p\n" \ \ "Stack: %p %p %p %p %p %p %p %p\n" \ " %p %p %p %p %p %p %p %p\n" \ " %p %p %p %p %p %p %p %p\n" #include "../../x86/xen/xen-head.S" /* * 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 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 - __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 ENTRY(early_gdt_descr) .word GDT_ENTRIES*8-1 .long per_cpu__gdt_page /* Overwritten for secondary CPUs */ /* * The boot_gdt must mirror the equivalent in setup.S and is * used only for booting. */ .align L1_CACHE_BYTES ENTRY(boot_gdt) .fill GDT_ENTRY_BOOT_CS,8,0 .quad 0x00cf9a000000ffff /* kernel 4GB code at 0x00000000 */ .quad 0x00cf92000000ffff /* kernel 4GB data at 0x00000000 */