Linux ARMv7中断向量表搬移(2)【转】

经历过kernel的汇编阶段，进入C语言start_kernel后对中断向量表的位置进行搬移，搬移函数是early_trap_init。

early_trap_init函数的调用流程为：
start_kernel(init/main.c)—>setup_arch(arch/arm/kernel/setup.c)—>paging_init(arch/arm/mm/mmu.c)—>devicemaps_init(arch/arm/mm/mmu.c)—>early_trap_init(arch/arm/kernel/traps.c）

/** Set up the device mappings. Since we clear out the page tables for all* mappings above VMALLOC_START, except early fixmap, we might remove debug* device mappings. This means earlycon can be used to debug this function* Any other function or debugging method which may touch any device _will_* crash the kernel.*/static void __init devicemaps_init(const struct machine_desc *mdesc){        struct map_desc map;        unsigned long addr;        void *vectors;        /*         * Allocate the vector page early.         *分配两个页的内存空间，arm中每个页的大小为4K，这两个页的内存空间，一个是为保存中断向量         *表，一个是为了保存中断的处理部分代码，这两部分代码的排布可以在         *(arch/arm/kernel/vmlinux.lds和arch/arm/kernel/entry-armv.S）中可以具体分析出来         */        vectors = early_alloc(PAGE_SIZE * 2);        early_trap_init(vectors);         /*          * Clear page table except top pmd used by early fixmaps          */         for (addr = VMALLOC_START; addr < (FIXADDR_TOP & PMD_MASK); addr += PMD_SIZE)                pmd_clear(pmd_off_k(addr));         /*          * Map the kernel if it is XIP.          * It is always first in the modulearea.          */#ifdef CONFIG_XIP_KERNEL  //此宏未定义        map.pfn = __phys_to_pfn(CONFIG_XIP_PHYS_ADDR & SECTION_MASK);        map.virtual = MODULES_VADDR;        map.length = ((unsigned long)_etext - map.virtual + ~SECTION_MASK) & SECTION_MASK;        map.type = MT_ROM;        create_mapping(&map);#endif        /*         * Map the cache flushing regions.         */#ifdef FLUSH_BASE  //此宏未定义        map.pfn = __phys_to_pfn(FLUSH_BASE_PHYS);        map.virtual = FLUSH_BASE;        map.length = SZ_1M;        map.type = MT_CACHECLEAN;        create_mapping(&map);#endif#ifdef FLUSH_BASE_MINICACHE  //此宏未定义        map.pfn = __phys_to_pfn(FLUSH_BASE_PHYS + SZ_1M);        map.virtual = FLUSH_BASE_MINICACHE;        map.length = SZ_1M;        map.type = MT_MINICLEAN;        create_mapping(&map);#endif        /*         * Create a mapping for the machine vectors at the high-vectors         * location (0xffff0000). If we aren't using high-vectors, also         * create a mapping at the low-vectors virtual address.         */        /*         *创建一个页的内存地址映射，虚拟地址为0xffff0000，此地址为中断向量表的高端地址         *设置中断向量表的高端地址在汇编的v7_setup中，使用的v7_crval设置了cp15的c1寄存器         *v7_crval定义在arch/arm/mm/proc-v7-2level.S。         */        map.pfn = __phys_to_pfn(virt_to_phys(vectors));        map.virtual = 0xffff0000;        map.length = PAGE_SIZE;#ifdef CONFIG_KUSER_HELPERS  //此宏有定义        map.type = MT_HIGH_VECTORS;#else        map.type = MT_LOW_VECTORS;#endif        create_mapping(&map);        /*         *判断中断向量表的位置是否设置在高端地址，如果中断向量表没有设置在高端地址，         *在映射低端中断向量表地址。         */        if (!vectors_high()) {                map.virtual = 0;                map.length = PAGE_SIZE * 2;                map.type = MT_LOW_VECTORS;            create_mapping(&map);        }        /* Now create a kernel read-only mapping */        map.pfn += 1;        map.virtual = 0xffff0000 + PAGE_SIZE;        map.length = PAGE_SIZE;        map.type = MT_LOW_VECTORS;        create_mapping(&map);        /*         * Ask the machine support to map in the statically mapped devices.         */        if (mdesc->map_io)                mdesc->map_io();        else                debug_ll_io_init();                fill_pmd_gaps();        /* Reserve fixed i/o space in VMALLOC region */        pci_reserve_io();         /*          * Finally flush the caches and tlb to ensure that we're in a          * consistent state wrt the writebuffer. This also ensures that          * any write-allocated cache lines in the vector page are written          * back. After this point, we can start to touch devices again.          */        local_flush_tlb_all();        flush_cache_all();        /* Enable asynchronous aborts */        early_abt_enable();}

        /*   AT         *  TFR   EV X F   I D LR    S         * .EEE ..EE PUI. .T.T 4RVI ZWRS BLDP WCAM         * rxxx rrxx xxx0 0101 xxxx xxxx x111 xxxx < forced         *   01    0 110       0011 1100 .111 1101 < we want         */        .align  2        .type   v7_crval, #objectv7_crval:        crval   clear=0x2120c302, mmuset=0x10c03c7d, ucset=0x00c01c7c

early_trap_init函数的分析

void __init early_trap_init(void *vectors_base){#ifndef CONFIG_CPU_V7M        unsigned long vectors = (unsigned long)vectors_base;        extern char __stubs_start[], __stubs_end[];        extern char __vectors_start[], __vectors_end[];        unsigned i;        vectors_page = vectors_base;        /*         * Poison the vectors page with an undefined instruction.  This         * rly_trap_init instruction is chosen to be undefined for both ARM and Thumb         * ISAs.  The Thumb version is an undefined instruction with a         * branch back to the undefined instruction.         * 将申请的4K先设置为未定义指令，防止在发生其他中断时，没有处理导致cpu错误         */        for (i = 0; i < PAGE_SIZE / sizeof(u32); i++)                ((u32 *)vectors_base)[i] = 0xe7fddef1;/*         * Copy the vectors, stubs and kuser helpers (in entry-armv.S)         * into the vector page, mapped at 0xffff0000, and ensure these         * are visible to the instruction stream.         */        /*         *将中断向量表和中断处理的代码搬移到申请的两页地址空间内         */        memcpy((void *)vectors, __vectors_start, __vectors_end - __vectors_start);        memcpy((void *)vectors + 0x1000, __stubs_start, __stubs_end - __stubs_start);        kuser_init(vectors_base);        flush_icache_range(vectors, vectors + PAGE_SIZE * 2);#else /* ifndef CONFIG_CPU_V7M */        /*         * on V7-M there is no need to copy the vector table to a dedicated         * memory area. The address is configurable and so a table in the kernel         * image can be used.         */#endif}

Original: https://www.cnblogs.com/yifeichongtian2021/p/15512262.html
Author: 壹飞冲天
Title: Linux ARMv7中断向量表搬移(2)【转】