/* * Kernel execution entry point code. * * Copyright (c) 1995-1996 Gary Thomas <gdt@linuxppc.org> * Initial PowerPC version. * Copyright (c) 1996 Cort Dougan <cort@cs.nmt.edu> * Rewritten for PReP * Copyright (c) 1996 Paul Mackerras <paulus@cs.anu.edu.au> * Low-level exception handers, MMU support, and rewrite. * Copyright (c) 1997 Dan Malek <dmalek@jlc.net> * PowerPC 8xx modifications. * Copyright (c) 1998-1999 TiVo, Inc. * PowerPC 403GCX modifications. * Copyright (c) 1999 Grant Erickson <grant@lcse.umn.edu> * PowerPC 403GCX/405GP modifications. * Copyright 2000 MontaVista Software Inc. * PPC405 modifications * PowerPC 403GCX/405GP modifications. * Author: MontaVista Software, Inc. * frank_rowand@mvista.com or source@mvista.com * debbie_chu@mvista.com * Copyright 2002-2005 MontaVista Software, Inc. * PowerPC 44x support, Matt Porter <mporter@kernel.crashing.org> * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License as published by the * Free Software Foundation; either version 2 of the License, or (at your * option) any later version. */ #include <asm/processor.h> #include <asm/page.h> #include <asm/mmu.h> #include <asm/pgtable.h> #include <asm/ibm4xx.h> #include <asm/ibm44x.h> #include <asm/cputable.h> #include <asm/thread_info.h> #include <asm/ppc_asm.h> #include <asm/asm-offsets.h> #include "head_booke.h" /* As with the other PowerPC ports, it is expected that when code * execution begins here, the following registers contain valid, yet * optional, information: * * r3 - Board info structure pointer (DRAM, frequency, MAC address, etc.) * r4 - Starting address of the init RAM disk * r5 - Ending address of the init RAM disk * r6 - Start of kernel command line string (e.g. "mem=128") * r7 - End of kernel command line string * */ .text _GLOBAL(_stext) _GLOBAL(_start) /* * Reserve a word at a fixed location to store the address * of abatron_pteptrs */ nop /* * Save parameters we are passed */ mr r31,r3 mr r30,r4 mr r29,r5 mr r28,r6 mr r27,r7 li r24,0 /* CPU number */ /* * Set up the initial MMU state * * We are still executing code at the virtual address * mappings set by the firmware for the base of RAM. * * We first invalidate all TLB entries but the one * we are running from. We then load the KERNELBASE * mappings so we can begin to use kernel addresses * natively and so the interrupt vector locations are * permanently pinned (necessary since Book E * implementations always have translation enabled). * * TODO: Use the known TLB entry we are running from to * determine which physical region we are located * in. This can be used to determine where in RAM * (on a shared CPU system) or PCI memory space * (on a DRAMless system) we are located. * For now, we assume a perfect world which means * we are located at the base of DRAM (physical 0). */ /* * Search TLB for entry that we are currently using. * Invalidate all entries but the one we are using. */ /* Load our current PID->MMUCR TID and MSR IS->MMUCR STS */ mfspr r3,SPRN_PID /* Get PID */ mfmsr r4 /* Get MSR */ andi. r4,r4,MSR_IS@l /* TS=1? */ beq wmmucr /* If not, leave STS=0 */ oris r3,r3,PPC44x_MMUCR_STS@h /* Set STS=1 */ wmmucr: mtspr SPRN_MMUCR,r3 /* Put MMUCR */ sync bl invstr /* Find our address */ invstr: mflr r5 /* Make it accessible */ tlbsx r23,0,r5 /* Find entry we are in */ li r4,0 /* Start at TLB entry 0 */ li r3,0 /* Set PAGEID inval value */ 1: cmpw r23,r4 /* Is this our entry? */ beq skpinv /* If so, skip the inval */ tlbwe r3,r4,PPC44x_TLB_PAGEID /* If not, inval the entry */ skpinv: addi r4,r4,1 /* Increment */ cmpwi r4,64 /* Are we done? */ bne 1b /* If not, repeat */ isync /* If so, context change */ /* * Configure and load pinned entry into TLB slot 63. */ lis r3,KERNELBASE@h /* Load the kernel virtual address */ ori r3,r3,KERNELBASE@l /* Kernel is at the base of RAM */ li r4, 0 /* Load the kernel physical address */ /* Load the kernel PID = 0 */ li r0,0 mtspr SPRN_PID,r0 sync /* Initialize MMUCR */ li r5,0 mtspr SPRN_MMUCR,r5 sync /* pageid fields */ clrrwi r3,r3,10 /* Mask off the effective page number */ ori r3,r3,PPC44x_TLB_VALID | PPC44x_TLB_256M /* xlat fields */ clrrwi r4,r4,10 /* Mask off the real page number */ /* ERPN is 0 for first 4GB page */ /* attrib fields */ /* Added guarded bit to protect against speculative loads/stores */ li r5,0 ori r5,r5,(PPC44x_TLB_SW | PPC44x_TLB_SR | PPC44x_TLB_SX | PPC44x_TLB_G) li r0,63 /* TLB slot 63 */ tlbwe r3,r0,PPC44x_TLB_PAGEID /* Load the pageid fields */ tlbwe r4,r0,PPC44x_TLB_XLAT /* Load the translation fields */ tlbwe r5,r0,PPC44x_TLB_ATTRIB /* Load the attrib/access fields */ /* Force context change */ mfmsr r0 mtspr SPRN_SRR1, r0 lis r0,3f@h ori r0,r0,3f@l mtspr SPRN_SRR0,r0 sync rfi /* If necessary, invalidate original entry we used */ 3: cmpwi r23,63 beq 4f li r6,0 tlbwe r6,r23,PPC44x_TLB_PAGEID isync 4: #ifdef CONFIG_SERIAL_TEXT_DEBUG /* * Add temporary UART mapping for early debug. * We can map UART registers wherever we want as long as they don't * interfere with other system mappings (e.g. with pinned entries). * For an example of how we handle this - see ocotea.h. --ebs */ /* pageid fields */ lis r3,UART0_IO_BASE@h ori r3,r3,PPC44x_TLB_VALID | PPC44x_TLB_4K /* xlat fields */ lis r4,UART0_PHYS_IO_BASE@h /* RPN depends on SoC */ #ifndef CONFIG_440EP ori r4,r4,0x0001 /* ERPN is 1 for second 4GB page */ #endif /* attrib fields */ li r5,0 ori r5,r5,(PPC44x_TLB_SW | PPC44x_TLB_SR | PPC44x_TLB_I | PPC44x_TLB_G) li r0,0 /* TLB slot 0 */ tlbwe r3,r0,PPC44x_TLB_PAGEID /* Load the pageid fields */ tlbwe r4,r0,PPC44x_TLB_XLAT /* Load the translation fields */ tlbwe r5,r0,PPC44x_TLB_ATTRIB /* Load the attrib/access fields */ /* Force context change */ isync #endif /* CONFIG_SERIAL_TEXT_DEBUG */ /* Establish the interrupt vector offsets */ SET_IVOR(0, CriticalInput); SET_IVOR(1, MachineCheck); SET_IVOR(2, DataStorage); SET_IVOR(3, InstructionStorage); SET_IVOR(4, ExternalInput); SET_IVOR(5, Alignment); SET_IVOR(6, Program); SET_IVOR(7, FloatingPointUnavailable); SET_IVOR(8, SystemCall); SET_IVOR(9, AuxillaryProcessorUnavailable); SET_IVOR(10, Decrementer); SET_IVOR(11, FixedIntervalTimer); SET_IVOR(12, WatchdogTimer); SET_IVOR(13, DataTLBError); SET_IVOR(14, InstructionTLBError); SET_IVOR(15, Debug); /* Establish the interrupt vector base */ lis r4,interrupt_base@h /* IVPR only uses the high 16-bits */ mtspr SPRN_IVPR,r4 #ifdef CONFIG_440EP /* Clear DAPUIB flag in CCR0 (enable APU between CPU and FPU) */ mfspr r2,SPRN_CCR0 lis r3,0xffef ori r3,r3,0xffff and r2,r2,r3 mtspr SPRN_CCR0,r2 isync #endif /* * This is where the main kernel code starts. */ /* ptr to current */ lis r2,init_task@h ori r2,r2,init_task@l /* ptr to current thread */ addi r4,r2,THREAD /* init task's THREAD */ mtspr SPRN_SPRG3,r4 /* stack */ lis r1,init_thread_union@h ori r1,r1,init_thread_union@l li r0,0 stwu r0,THREAD_SIZE-STACK_FRAME_OVERHEAD(r1) bl early_init /* * Decide what sort of machine this is and initialize the MMU. */ mr r3,r31 mr r4,r30 mr r5,r29 mr r6,r28 mr r7,r27 bl machine_init bl MMU_init /* Setup PTE pointers for the Abatron bdiGDB */ lis r6, swapper_pg_dir@h ori r6, r6, swapper_pg_dir@l lis r5, abatron_pteptrs@h ori r5, r5, abatron_pteptrs@l lis r4, KERNELBASE@h ori r4, r4, KERNELBASE@l stw r5, 0(r4) /* Save abatron_pteptrs at a fixed location */ stw r6, 0(r5) /* Let's move on */ lis r4,start_kernel@h ori r4,r4,start_kernel@l lis r3,MSR_KERNEL@h ori r3,r3,MSR_KERNEL@l mtspr SPRN_SRR0,r4 mtspr SPRN_SRR1,r3 rfi /* change context and jump to start_kernel */ /* * Interrupt vector entry code * * The Book E MMUs are always on so we don't need to handle * interrupts in real mode as with previous PPC processors. In * this case we handle interrupts in the kernel virtual address * space. * * Interrupt vectors are dynamically placed relative to the * interrupt prefix as determined by the address of interrupt_base. * The interrupt vectors offsets are programmed using the labels * for each interrupt vector entry. * * Interrupt vectors must be aligned on a 16 byte boundary. * We align on a 32 byte cache line boundary for good measure. */ interrupt_base: /* Critical Input Interrupt */ CRITICAL_EXCEPTION(0x0100, CriticalInput, unknown_exception) /* Machine Check Interrupt */ #ifdef CONFIG_440A MCHECK_EXCEPTION(0x0200, MachineCheck, machine_check_exception) #else CRITICAL_EXCEPTION(0x0200, MachineCheck, machine_check_exception) #endif /* Data Storage Interrupt */ START_EXCEPTION(DataStorage) mtspr SPRN_SPRG0, r10 /* Save some working registers */ mtspr SPRN_SPRG1, r11 mtspr SPRN_SPRG4W, r12 mtspr SPRN_SPRG5W, r13 mfcr r11 mtspr SPRN_SPRG7W, r11 /* * Check if it was a store fault, if not then bail * because a user tried to access a kernel or * read-protected page. Otherwise, get the * offending address and handle it. */ mfspr r10, SPRN_ESR andis. r10, r10, ESR_ST@h beq 2f mfspr r10, SPRN_DEAR /* Get faulting address */ /* If we are faulting a kernel address, we have to use the * kernel page tables. */ lis r11, TASK_SIZE@h cmplw r10, r11 blt+ 3f lis r11, swapper_pg_dir@h ori r11, r11, swapper_pg_dir@l mfspr r12,SPRN_MMUCR rlwinm r12,r12,0,0,23 /* Clear TID */ b 4f /* Get the PGD for the current thread */ 3: mfspr r11,SPRN_SPRG3 lwz r11,PGDIR(r11) /* Load PID into MMUCR TID */ mfspr r12,SPRN_MMUCR /* Get MMUCR */ mfspr r13,SPRN_PID /* Get PID */ rlwimi r12,r13,0,24,31 /* Set TID */ 4: mtspr SPRN_MMUCR,r12 rlwinm r12, r10, 13, 19, 29 /* Compute pgdir/pmd offset */ lwzx r11, r12, r11 /* Get pgd/pmd entry */ rlwinm. r12, r11, 0, 0, 20 /* Extract pt base address */ beq 2f /* Bail if no table */ rlwimi r12, r10, 23, 20, 28 /* Compute pte address */ lwz r11, 4(r12) /* Get pte entry */ andi. r13, r11, _PAGE_RW /* Is it writeable? */ beq 2f /* Bail if not */ /* Update 'changed'. */ ori r11, r11, _PAGE_DIRTY|_PAGE_ACCESSED|_PAGE_HWWRITE stw r11, 4(r12) /* Update Linux page table */ li r13, PPC44x_TLB_SR@l /* Set SR */ rlwimi r13, r11, 29, 29, 29 /* SX = _PAGE_HWEXEC */ rlwimi r13, r11, 0, 30, 30 /* SW = _PAGE_RW */ rlwimi r13, r11, 29, 28, 28 /* UR = _PAGE_USER */ rlwimi r12, r11, 31, 26, 26 /* (_PAGE_USER>>1)->r12 */ rlwimi r12, r11, 29, 30, 30 /* (_PAGE_USER>>3)->r12 */ and r12, r12, r11 /* HWEXEC/RW & USER */ rlwimi r13, r12, 0, 26, 26 /* UX = HWEXEC & USER */ rlwimi r13, r12, 3, 27, 27 /* UW = RW & USER */ rlwimi r11,r13,0,26,31 /* Insert static perms */ rlwinm r11,r11,0,20,15 /* Clear U0-U3 */ /* find the TLB index that caused the fault. It has to be here. */ tlbsx r10, 0, r10 tlbwe r11, r10, PPC44x_TLB_ATTRIB /* Write ATTRIB */ /* Done...restore registers and get out of here. */ mfspr r11, SPRN_SPRG7R mtcr r11 mfspr r13, SPRN_SPRG5R mfspr r12, SPRN_SPRG4R mfspr r11, SPRN_SPRG1 mfspr r10, SPRN_SPRG0 rfi /* Force context change */ 2: /* * The bailout. Restore registers to pre-exception conditions * and call the heavyweights to help us out. */ mfspr r11, SPRN_SPRG7R mtcr r11 mfspr r13, SPRN_SPRG5R mfspr r12, SPRN_SPRG4R mfspr r11, SPRN_SPRG1 mfspr r10, SPRN_SPRG0 b data_access /* Instruction Storage Interrupt */ INSTRUCTION_STORAGE_EXCEPTION /* External Input Interrupt */ EXCEPTION(0x0500, ExternalInput, do_IRQ, EXC_XFER_LITE) /* Alignment Interrupt */ ALIGNMENT_EXCEPTION /* Program Interrupt */ PROGRAM_EXCEPTION /* Floating Point Unavailable Interrupt */ #ifdef CONFIG_PPC_FPU FP_UNAVAILABLE_EXCEPTION #else EXCEPTION(0x2010, FloatingPointUnavailable, unknown_exception, EXC_XFER_EE) #endif /* System Call Interrupt */ START_EXCEPTION(SystemCall) NORMAL_EXCEPTION_PROLOG EXC_XFER_EE_LITE(0x0c00, DoSyscall) /* Auxillary Processor Unavailable Interrupt */ EXCEPTION(0x2020, AuxillaryProcessorUnavailable, unknown_exception, EXC_XFER_EE) /* Decrementer Interrupt */ DECREMENTER_EXCEPTION /* Fixed Internal Timer Interrupt */ /* TODO: Add FIT support */ EXCEPTION(0x1010, FixedIntervalTimer, unknown_exception, EXC_XFER_EE) /* Watchdog Timer Interrupt */ /* TODO: Add watchdog support */ #ifdef CONFIG_BOOKE_WDT CRITICAL_EXCEPTION(0x1020, WatchdogTimer, WatchdogException) #else CRITICAL_EXCEPTION(0x1020, WatchdogTimer, unknown_exception) #endif /* Data TLB Error Interrupt */ START_EXCEPTION(DataTLBError) mtspr SPRN_SPRG0, r10 /* Save some working registers */ mtspr SPRN_SPRG1, r11 mtspr SPRN_SPRG4W, r12 mtspr SPRN_SPRG5W, r13 mfcr r11 mtspr SPRN_SPRG7W, r11 mfspr r10, SPRN_DEAR /* Get faulting address */ /* If we are faulting a kernel address, we have to use the * kernel page tables. */ lis r11, TASK_SIZE@h cmplw r10, r11 blt+ 3f lis r11, swapper_pg_dir@h ori r11, r11, swapper_pg_dir@l mfspr r12,SPRN_MMUCR rlwinm r12,r12,0,0,23 /* Clear TID */ b 4f /* Get the PGD for the current thread */ 3: mfspr r11,SPRN_SPRG3 lwz r11,PGDIR(r11) /* Load PID into MMUCR TID */ mfspr r12,SPRN_MMUCR mfspr r13,SPRN_PID /* Get PID */ rlwimi r12,r13,0,24,31 /* Set TID */ 4: mtspr SPRN_MMUCR,r12 rlwinm r12, r10, 13, 19, 29 /* Compute pgdir/pmd offset */ lwzx r11, r12, r11 /* Get pgd/pmd entry */ rlwinm. r12, r11, 0, 0, 20 /* Extract pt base address */ beq 2f /* Bail if no table */ rlwimi r12, r10, 23, 20, 28 /* Compute pte address */ lwz r11, 4(r12) /* Get pte entry */ andi. r13, r11, _PAGE_PRESENT /* Is the page present? */ beq 2f /* Bail if not present */ ori r11, r11, _PAGE_ACCESSED stw r11, 4(r12) /* Jump to common tlb load */ b finish_tlb_load 2: /* The bailout. Restore registers to pre-exception conditions * and call the heavyweights to help us out. */ mfspr r11, SPRN_SPRG7R mtcr r11 mfspr r13, SPRN_SPRG5R mfspr r12, SPRN_SPRG4R mfspr r11, SPRN_SPRG1 mfspr r10, SPRN_SPRG0 b data_access /* Instruction TLB Error Interrupt */ /* * Nearly the same as above, except we get our * information from different registers and bailout * to a different point. */ START_EXCEPTION(InstructionTLBError) mtspr SPRN_SPRG0, r10 /* Save some working registers */ mtspr SPRN_SPRG1, r11 mtspr SPRN_SPRG4W, r12 mtspr SPRN_SPRG5W, r13 mfcr r11 mtspr SPRN_SPRG7W, r11 mfspr r10, SPRN_SRR0 /* Get faulting address */ /* If we are faulting a kernel address, we have to use the * kernel page tables. */ lis r11, TASK_SIZE@h cmplw r10, r11 blt+ 3f lis r11, swapper_pg_dir@h ori r11, r11, swapper_pg_dir@l mfspr r12,SPRN_MMUCR rlwinm r12,r12,0,0,23 /* Clear TID */ b 4f /* Get the PGD for the current thread */ 3: mfspr r11,SPRN_SPRG3 lwz r11,PGDIR(r11) /* Load PID into MMUCR TID */ mfspr r12,SPRN_MMUCR mfspr r13,SPRN_PID /* Get PID */ rlwimi r12,r13,0,24,31 /* Set TID */ 4: mtspr SPRN_MMUCR,r12 rlwinm r12, r10, 13, 19, 29 /* Compute pgdir/pmd offset */ lwzx r11, r12, r11 /* Get pgd/pmd entry */ rlwinm. r12, r11, 0, 0, 20 /* Extract pt base address */ beq 2f /* Bail if no table */ rlwimi r12, r10, 23, 20, 28 /* Compute pte address */ lwz r11, 4(r12) /* Get pte entry */ andi. r13, r11, _PAGE_PRESENT /* Is the page present? */ beq 2f /* Bail if not present */ ori r11, r11, _PAGE_ACCESSED stw r11, 4(r12) /* Jump to common TLB load point */ b finish_tlb_load 2: /* The bailout. Restore registers to pre-exception conditions * and call the heavyweights to help us out. */ mfspr r11, SPRN_SPRG7R mtcr r11 mfspr r13, SPRN_SPRG5R mfspr r12, SPRN_SPRG4R mfspr r11, SPRN_SPRG1 mfspr r10, SPRN_SPRG0 b InstructionStorage /* Debug Interrupt */ DEBUG_EXCEPTION /* * Local functions */ /* * Data TLB exceptions will bail out to this point * if they can't resolve the lightweight TLB fault. */ data_access: NORMAL_EXCEPTION_PROLOG mfspr r5,SPRN_ESR /* Grab the ESR, save it, pass arg3 */ stw r5,_ESR(r11) mfspr r4,SPRN_DEAR /* Grab the DEAR, save it, pass arg2 */ EXC_XFER_EE_LITE(0x0300, handle_page_fault) /* * Both the instruction and data TLB miss get to this * point to load the TLB. * r10 - EA of fault * r11 - available to use * r12 - Pointer to the 64-bit PTE * r13 - available to use * MMUCR - loaded with proper value when we get here * Upon exit, we reload everything and RFI. */ finish_tlb_load: /* * We set execute, because we don't have the granularity to * properly set this at the page level (Linux problem). * If shared is set, we cause a zero PID->TID load. * Many of these bits are software only. Bits we don't set * here we (properly should) assume have the appropriate value. */ /* Load the next available TLB index */ lis r13, tlb_44x_index@ha lwz r13, tlb_44x_index@l(r13) /* Load the TLB high watermark */ lis r11, tlb_44x_hwater@ha lwz r11, tlb_44x_hwater@l(r11) /* Increment, rollover, and store TLB index */ addi r13, r13, 1 cmpw 0, r13, r11 /* reserve entries */ ble 7f li r13, 0 7: /* Store the next available TLB index */ lis r11, tlb_44x_index@ha stw r13, tlb_44x_index@l(r11) lwz r11, 0(r12) /* Get MS word of PTE */ lwz r12, 4(r12) /* Get LS word of PTE */ rlwimi r11, r12, 0, 0 , 19 /* Insert RPN */ tlbwe r11, r13, PPC44x_TLB_XLAT /* Write XLAT */ /* * Create PAGEID. This is the faulting address, * page size, and valid flag. */ li r11, PPC44x_TLB_VALID | PPC44x_TLB_4K rlwimi r10, r11, 0, 20, 31 /* Insert valid and page size */ tlbwe r10, r13, PPC44x_TLB_PAGEID /* Write PAGEID */ li r10, PPC44x_TLB_SR@l /* Set SR */ rlwimi r10, r12, 0, 30, 30 /* Set SW = _PAGE_RW */ rlwimi r10, r12, 29, 29, 29 /* SX = _PAGE_HWEXEC */ rlwimi r10, r12, 29, 28, 28 /* UR = _PAGE_USER */ rlwimi r11, r12, 31, 26, 26 /* (_PAGE_USER>>1)->r12 */ and r11, r12, r11 /* HWEXEC & USER */ rlwimi r10, r11, 0, 26, 26 /* UX = HWEXEC & USER */ rlwimi r12, r10, 0, 26, 31 /* Insert static perms */ rlwinm r12, r12, 0, 20, 15 /* Clear U0-U3 */ tlbwe r12, r13, PPC44x_TLB_ATTRIB /* Write ATTRIB */ /* Done...restore registers and get out of here. */ mfspr r11, SPRN_SPRG7R mtcr r11 mfspr r13, SPRN_SPRG5R mfspr r12, SPRN_SPRG4R mfspr r11, SPRN_SPRG1 mfspr r10, SPRN_SPRG0 rfi /* Force context change */ /* * Global functions */ /* * extern void giveup_altivec(struct task_struct *prev) * * The 44x core does not have an AltiVec unit. */ _GLOBAL(giveup_altivec) blr /* * extern void giveup_fpu(struct task_struct *prev) * * The 44x core does not have an FPU. */ #ifndef CONFIG_PPC_FPU _GLOBAL(giveup_fpu) blr #endif /* * extern void abort(void) * * At present, this routine just applies a system reset. */ _GLOBAL(abort) mfspr r13,SPRN_DBCR0 oris r13,r13,DBCR0_RST_SYSTEM@h mtspr SPRN_DBCR0,r13 _GLOBAL(set_context) #ifdef CONFIG_BDI_SWITCH /* Context switch the PTE pointer for the Abatron BDI2000. * The PGDIR is the second parameter. */ lis r5, abatron_pteptrs@h ori r5, r5, abatron_pteptrs@l stw r4, 0x4(r5) #endif mtspr SPRN_PID,r3 isync /* Force context change */ blr /* * We put a few things here that have to be page-aligned. This stuff * goes at the beginning of the data segment, which is page-aligned. */ .data .align 12 .globl sdata sdata: .globl empty_zero_page empty_zero_page: .space 4096 /* * To support >32-bit physical addresses, we use an 8KB pgdir. */ .globl swapper_pg_dir swapper_pg_dir: .space 8192 /* Reserved 4k for the critical exception stack & 4k for the machine * check stack per CPU for kernel mode exceptions */ .section .bss .align 12 exception_stack_bottom: .space BOOKE_EXCEPTION_STACK_SIZE .globl exception_stack_top exception_stack_top: /* * This space gets a copy of optional info passed to us by the bootstrap * which is used to pass parameters into the kernel like root=/dev/sda1, etc. */ .globl cmd_line cmd_line: .space 512 /* * Room for two PTE pointers, usually the kernel and current user pointers * to their respective root page table. */ abatron_pteptrs: .space 8