/* * Copyright (c) 2010-2015 Wind River Systems, Inc. * * SPDX-License-Identifier: Apache-2.0 */ /** * @file * @brief Crt0 module for the IA-32 boards * * This module contains the initial code executed by the Zephyr Kernel ELF image * after having been loaded into RAM. */ #include /* exports (private APIs) */ GTEXT(__start) /* externs */ GTEXT(_Cstart) GDATA(_idt_base_address) GDATA(_interrupt_stack) GDATA(_Idt) #ifndef CONFIG_GDT_DYNAMIC GDATA(_gdt) #endif #if defined(CONFIG_SSE) GDATA(_sse_mxcsr_default_value) #endif #if defined(CONFIG_BOOT_TIME_MEASUREMENT) GDATA(__start_tsc) #endif #ifdef CONFIG_SYS_POWER_DEEP_SLEEP GTEXT(_sys_soc_resume_from_deep_sleep) #endif /* processor is executing in 32-bit protected mode */ .balign 16,0x90 SECTION_FUNC(TEXT_START, __start) #ifdef CONFIG_BOOT_TIME_MEASUREMENT /* * Record BootTime from start of Kernel. * Store value temporarily in Register edi & esi and * write to memory once memory access is allowed. * That is, once the data segment register has been setup to access * the .data/.rodata/.bss section of the linked image. */ rdtsc mov %eax, %esi /* low value */ mov %edx, %edi /* high value */ #endif /* Enable write-back caching by clearing the NW and CD bits */ movl %cr0, %eax andl $0x9fffffff, %eax movl %eax, %cr0 /* * Ensure interrupts are disabled. Interrupts are enabled when * the first context switch occurs. */ cli /* * Although the bootloader sets up an Interrupt Descriptor Table (IDT) * and a Global Descriptor Table (GDT), the specification encourages * booted operating systems to setup their own IDT and GDT. */ #if CONFIG_SET_GDT lgdt _gdt_rom /* load 32-bit operand size GDT */ #endif lidt _Idt /* load 32-bit operand size IDT */ #ifdef CONFIG_SET_GDT /* If we set our own GDT, update the segment registers as well. */ movw $0x10, %ax /* data segment selector (entry = 3) */ movw %ax, %ds /* set DS */ movw %ax, %es /* set ES */ movw %ax, %fs /* set FS */ movw %ax, %gs /* set GS */ movw %ax, %ss /* set SS */ ljmp $0x08, $__csSet /* set CS = 0x08 */ __csSet: #endif /* CONFIG_SET_GDT */ #ifdef CONFIG_BOOT_TIME_MEASUREMENT /* * Store rdtsc result from temporary regiter ESI & EDI into memory. */ mov %esi, __start_tsc /* low value */ mov %edi, __start_tsc+4 /* high value */ #endif #if !defined(CONFIG_FLOAT) /* * Force an #NM exception for floating point instructions * since FP support hasn't been configured */ movl %cr0, %eax /* move CR0 to EAX */ orl $0x2e, %eax /* CR0[NE+TS+EM+MP]=1 */ movl %eax, %cr0 /* move EAX to CR0 */ #else /* * Permit use of x87 FPU instructions * * Note that all floating point exceptions are masked by default, * and that _no_ handler for x87 FPU exceptions (#MF) is provided. */ movl %cr0, %eax /* move CR0 to EAX */ orl $0x22, %eax /* CR0[NE+MP]=1 */ andl $~0xc, %eax /* CR0[TS+EM]=0 */ movl %eax, %cr0 /* move EAX to CR0 */ fninit /* set x87 FPU to its default state */ #if defined(CONFIG_SSE) /* * Permit use of SSE instructions * * Note that all SSE exceptions are masked by default, * and that _no_ handler for SSE exceptions (#XM) is provided. */ movl %cr4, %eax /* move CR4 to EAX */ orl $0x200, %eax /* CR4[OSFXSR] = 1 */ andl $~0x400, %eax /* CR4[OSXMMEXCPT] = 0 */ movl %eax, %cr4 /* move EAX to CR4 */ ldmxcsr _sse_mxcsr_default_value /* initialize SSE control/status reg */ #endif /* CONFIG_SSE */ #endif /* !CONFIG_FLOAT */ /* * Set the stack pointer to the area used for the interrupt stack. * Note this stack is used during the execution of __start() and * _Cstart() until the multi-tasking kernel is initialized. The * dual-purposing of this area of memory is safe since * interrupts are disabled until the first context switch. * * nano_init.c enforces that the _interrupt_stack pointer and * the ISR stack size are some multiple of STACK_ALIGN, which * is at least 4. * * This is also used to call the _sys_soc_resume_from_deep_sleep() * routine to avoid memory corruption if the system is resuming from * deep sleep. It is important that _sys_soc_resume_from_deep_sleep() * restores the stack pointer to what it was at deep sleep before * enabling interrupts. This is necessary to avoid * interfering with interrupt handler use of this stack. * If it is a cold boot then _sys_soc_resume_from_deep_sleep() should * not do anything and must return immediately. */ #ifdef CONFIG_INIT_STACKS movl $0xAAAAAAAA, %eax leal _interrupt_stack, %edi stack_size_dwords = (CONFIG_ISR_STACK_SIZE / 4) movl $stack_size_dwords, %ecx rep stosl #endif movl $_interrupt_stack, %esp addl $CONFIG_ISR_STACK_SIZE, %esp #if defined(CONFIG_SYS_POWER_DEEP_SLEEP) && \ !defined(CONFIG_BOOTLOADER_CONTEXT_RESTORE) /* * Invoke _sys_soc_resume_from_deep_sleep() hook to handle resume from * deep sleep. It should first check whether system is recovering from * deep sleep state. If it is, then this function should restore * states and resume at the point system went to deep sleep. * In this case this function will never return. * * If system is not recovering from deep sleep then it is a * cold boot. In this case, this function would immediately * return and execution falls through to cold boot path. */ call _sys_soc_resume_from_deep_sleep #endif #ifdef CONFIG_XIP /* * copy DATA section from ROM to RAM region * DATA is followed by BSS section. */ movl $__data_ram_start, %edi /* DATA in RAM (dest) */ movl $__data_rom_start, %esi /* DATA in ROM (src) */ movl $__data_num_words, %ecx /* Size of DATA in quad bytes */ #ifdef CONFIG_SSE /* copy 16 bytes at a time using XMM until < 16 bytes remain */ movl %ecx ,%edx /* save number of quad bytes */ shrl $2, %ecx /* How many 16 bytes? */ je dataWords dataDQ: movdqu (%esi), %xmm0 movdqu %xmm0, (%edi) addl $16, %esi addl $16, %edi loop dataDQ dataWords: movl %edx, %ecx /* restore # quad bytes */ andl $0x3, %ecx /* only need to copy at most 3 quad bytes */ #endif /* CONFIG_SSE */ rep movsl /* copy data 4 bytes at a time */ #endif /* CONFIG_XIP */ /* * Clear BSS: bzero (__bss_start, __bss_num_words*4) * * It's assumed that BSS size will be a multiple of a long (4 bytes), * and aligned on a double word (32-bit) boundary */ #ifdef CONFIG_SSE /* use XMM register to clear 16 bytes at a time */ pxor %xmm0, %xmm0 /* zero out xmm0 register */ movl $__bss_start, %edi /* load BSS start address */ movl $__bss_num_words, %ecx /* number of quad bytes in .bss */ movl %ecx, %edx /* make a copy of # quad bytes */ shrl $2, %ecx /* How many multiples of 16 byte ? */ je bssWords bssDQ: movdqu %xmm0, (%edi) /* zero 16 bytes... */ addl $16, %edi loop bssDQ /* fall through to handle the remaining double words (32-bit chunks) */ bssWords: xorl %eax, %eax /* fill memory with 0 */ movl %edx, %ecx /* move # quad bytes into ECX (for rep) */ andl $0x3, %ecx /* only need to zero at most 3 quad bytes */ cld rep stosl /* zero memory per 4 bytes */ #else /* !CONFIG_SSE */ /* clear out BSS double words (32-bits at a time) */ xorl %eax, %eax /* fill memory with 0 */ movl $__bss_start, %edi /* load BSS start address */ movl $__bss_num_words, %ecx /* number of quad bytes */ cld rep stosl /* zero memory per 4 bytes */ #endif /* CONFIG_SSE */ #ifdef CONFIG_GDT_DYNAMIC /* activate RAM-based Global Descriptor Table (GDT) */ lgdt %ds:_gdt #endif /* Jump to C portion of kernel initialization and never return */ jmp _Cstart #if defined(CONFIG_SSE) /* SSE control & status register initial value */ _sse_mxcsr_default_value: .long 0x1f80 /* all SSE exceptions clear & masked */ #endif /* CONFIG_SSE */ /* Interrupt Descriptor Table (IDT) definition */ _Idt: .word (CONFIG_IDT_NUM_VECTORS * 8) - 1 /* limit: size of IDT-1 */ /* * Physical start address = 0. When executing natively, this * will be placed at the same location as the interrupt vector table * setup by the BIOS (or GRUB?). */ .long _idt_base_address /* physical start address */ #ifdef CONFIG_BOOTLOADER_UNKNOWN /* Multiboot header definition is needed for some bootloaders */ /* * The multiboot header must be in the first 8 Kb of the kernel image * (not including the ELF section header(s)) and be aligned on a * 4 byte boundary. */ .balign 4,0x90 .long 0x1BADB002 /* multiboot magic number */ /* * Flags = no bits are being set, specifically bit 16 is not being * set since the supplied kernel image is an ELF file, and the * multiboot loader shall use the information from the program and * section header to load and boot the kernel image. */ .long 0x00000000 /* * checksum = 32-bit unsigned value which, when added to the other * magic fields (i.e. "magic" and "flags"), must have a 32-bit * unsigned sum of zero. */ .long -(0x1BADB002 + 0) #endif /* CONFIG_BOOTLOADER_UNKNOWN */ #ifdef CONFIG_SET_GDT /* GDT should be aligned on 8-byte boundary for best processor * performance, see Section 3.5.1 of IA architecture SW developer * manual, Vol 3. */ .balign 8 /* * The following 3 GDT entries implement the so-called "basic * flat model", i.e. a single code segment descriptor and a single * data segment descriptor, giving the kernel access to a continuous, * unsegmented address space. Both segment descriptors map the entire * linear address space (i.e. 0 to 4 GB-1), thus the segmentation * mechanism will never generate "out of limit memory reference" * exceptions even if physical memory does not reside at the referenced * address. * * The 'A' (accessed) bit in the type field is set for all the * data/code segment descriptors to accommodate placing these entries * in ROM, to prevent the processor from freaking out when it tries * and fails to set it. */ #ifndef CONFIG_GDT_DYNAMIC _gdt: #endif _gdt_rom: /* Entry 0 (selector=0x0000): The "NULL descriptor". The CPU never * actually looks at this entry, so we stuff 6-byte the pseudo * descriptor here */ .word _gdt_rom_end - _gdt_rom - 1 /* Limit on GDT */ .long _gdt_rom /* table address: _gdt_rom */ .word 0x0000 /* Entry 1 (selector=0x0008): Code descriptor: DPL0 */ .word 0xffff /* limit: xffff */ .word 0x0000 /* base : xxxx0000 */ .byte 0x00 /* base : xx00xxxx */ .byte 0x9b /* Accessed, Code e/r, Present, DPL0 */ .byte 0xcf /* limit: fxxxx, Page Gra, 32bit */ .byte 0x00 /* base : 00xxxxxx */ /* Entry 2 (selector=0x0010): Data descriptor: DPL0 */ .word 0xffff /* limit: xffff */ .word 0x0000 /* base : xxxx0000 */ .byte 0x00 /* base : xx00xxxx */ .byte 0x93 /* Accessed, Data r/w, Present, DPL0 */ .byte 0xcf /* limit: fxxxx, Page Gra, 32bit */ .byte 0x00 /* base : 00xxxxxx */ _gdt_rom_end: #endif