浅析armlinux-setup_arch()->convert_to_tag_list()函数3
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建议首先参考《浅析armlinux2_4_19启动程序[head-armv.s文件]》[http://gliethttp.cublog.cn]
//1.旧格式param_struct结构体 #define COMMAND_LINE_SIZE 1024 /* This is the old deprecated way to pass parameters to the kernel */ struct param_struct { union { struct { unsigned long page_size; /* 0 */ unsigned long nr_pages; /* 4 */ unsigned long ramdisk_size; /* 8 */ unsigned long flags; /* 12 */ #define FLAG_READONLY 1 #define FLAG_RDLOAD 4 #define FLAG_RDPROMPT 8 unsigned long rootdev; /* 16 */ unsigned long video_num_cols; /* 20 */ unsigned long video_num_rows; /* 24 */ unsigned long video_x; /* 28 */ unsigned long video_y; /* 32 */ unsigned long memc_control_reg; /* 36 */ unsigned char sounddefault; /* 40 */ unsigned char adfsdrives; /* 41 */ unsigned char bytes_per_char_h; /* 42 */ unsigned char bytes_per_char_v; /* 43 */ unsigned long pages_in_bank[4]; /* 44 */ unsigned long pages_in_vram; /* 60 */ unsigned long initrd_start; /* 64 */ unsigned long initrd_size; /* 68 */ unsigned long rd_start; /* 72 */ unsigned long system_rev; /* 76 */ unsigned long system_serial_low; /* 80 */ unsigned long system_serial_high; /* 84 */ unsigned long mem_fclk_21285; /* 88 */ } s; char unused[256]; } u1; union { char paths[8][128]; struct { unsigned long magic; char n[1024 - sizeof(unsigned long)]; } s; } u2; char commandline[COMMAND_LINE_SIZE]; }; //2.arch/arm/kernel/Compat.c->convert_to_tag_list() //if (tags->hdr.tag != ATAG_CORE)//如果传递参数非tag list格式,那么就是param_struct格式 //convert_to_tag_list(tags); //使用convert_to_tag_list将param_struct格式参数转化为tag list格式参数 void __init convert_to_tag_list(struct tag *tags) {//tags地址为物理地址0x20000100[gliethttp] struct param_struct *params = (struct param_struct *)tags; build_tag_list(params, ¶ms->u2);//将转换结果临时存储在¶ms->u2,之后拷贝到params } //3.arch/arm/kernel/Compat.c->build_tag_list() static void __init build_tag_list(struct param_struct *params, void *taglist) {struct tag *tag = taglist; if (params->u1.s.page_size != PAGE_SIZE) { printk(KERN_WARNING "Warning: bad configuration page, " "trying to continue\n"); return; } printk(KERN_DEBUG "Converting old-style param struct to taglist\n"); //ATAG_CORE 将params下core相关设置,转换成tag,形成list[gliethttp] tag->hdr.tag = ATAG_CORE; tag->hdr.size = tag_size(tag_core); tag->u.core.flags = params->u1.s.flags & FLAG_READONLY; tag->u.core.pagesize = params->u1.s.page_size; tag->u.core.rootdev = params->u1.s.rootdev; //ATAG_RAMDISK 紧跟着ATAG_CORE继续存储 tag = tag_next(tag); tag->hdr.tag = ATAG_RAMDISK; tag->hdr.size = tag_size(tag_ramdisk); tag->u.ramdisk.flags = (params->u1.s.flags & FLAG_RDLOAD ? 1 : 0) | (params->u1.s.flags & FLAG_RDPROMPT ? 2 : 0); tag->u.ramdisk.size = params->u1.s.ramdisk_size; tag->u.ramdisk.start = params->u1.s.rd_start; //ATAG_INITRD 紧跟存储 tag = tag_next(tag); tag->hdr.tag = ATAG_INITRD; tag->hdr.size = tag_size(tag_initrd); tag->u.initrd.start = params->u1.s.initrd_start; tag->u.initrd.size = params->u1.s.initrd_size; //ATAG_SERIAL tag = tag_next(tag); tag->hdr.tag = ATAG_SERIAL; tag->hdr.size = tag_size(tag_serialnr); tag->u.serialnr.low = params->u1.s.system_serial_low; tag->u.serialnr.high = params->u1.s.system_serial_high; //ATAG_REVISION tag = tag_next(tag); tag->hdr.tag = ATAG_REVISION; tag->hdr.size = tag_size(tag_revision); tag->u.revision.rev = params->u1.s.system_rev;
#ifdef CONFIG_ARCH_ACORN//false if (machine_is_riscpc()) { int i; //4个memory块 for (i = 0; i < 4; i++) tag = memtag(tag, PHYS_OFFSET + (i << 26), params->u1.s.pages_in_bank[i] * PAGE_SIZE); } else #endif //ok,只有一个32M[0x2000000]内存块,见后 tag = memtag(tag, PHYS_OFFSET, params->u1.s.nr_pages * PAGE_SIZE);
#ifdef CONFIG_FOOTBRIDGE//未用 if (params->u1.s.mem_fclk_21285) { tag = tag_next(tag); tag->hdr.tag = ATAG_MEMCLK; tag->hdr.size = tag_size(tag_memclk); tag->u.memclk.fmemclk = params->u1.s.mem_fclk_21285; } #endif
#ifdef CONFIG_ARCH_EBSA285//未用 if (machine_is_ebsa285()) { tag = tag_next(tag); tag->hdr.tag = ATAG_VIDEOTEXT; tag->hdr.size = tag_size(tag_videotext); tag->u.videotext.x = params->u1.s.video_x; tag->u.videotext.y = params->u1.s.video_y; tag->u.videotext.video_page = 0; tag->u.videotext.video_mode = 0; tag->u.videotext.video_cols = params->u1.s.video_num_cols; tag->u.videotext.video_ega_bx = 0; tag->u.videotext.video_lines = params->u1.s.video_num_rows; tag->u.videotext.video_isvga = 1; tag->u.videotext.video_points = 8; } #endif
#ifdef CONFIG_ARCH_ACORN//未用 tag = tag_next(tag); tag->hdr.tag = ATAG_ACORN; tag->hdr.size = tag_size(tag_acorn); tag->u.acorn.memc_control_reg = params->u1.s.memc_control_reg; tag->u.acorn.vram_pages = params->u1.s.pages_in_vram; tag->u.acorn.sounddefault = params->u1.s.sounddefault; tag->u.acorn.adfsdrives = params->u1.s.adfsdrives; #endif //ATAG_CMDLINE tag = tag_next(tag); tag->hdr.tag = ATAG_CMDLINE; tag->hdr.size = (strlen(params->commandline) + 3 + sizeof(struct tag_header)) >> 2; strcpy(tag->u.cmdline.cmdline, params->commandline); //ATAG_NONE 明确的结尾标识 tag = tag_next(tag); tag->hdr.tag = ATAG_NONE; tag->hdr.size = 0; //间缓存到taglist中的tag list数据转储到params memmove(params, taglist, ((int)tag) - ((int)taglist) + sizeof(struct tag_header)/*ATAG_NONE的长度*/); } //4.arch/arm/kernel/Compat.c->memtag() static struct tag * __init memtag(struct tag *tag, unsigned long start, unsigned long size) { //ATAG_MEM 紧跟前一个tag,start=0x20000000 tag = tag_next(tag); tag->hdr.tag = ATAG_MEM; tag->hdr.size = tag_size(tag_mem32); tag->u.mem.size = size; tag->u.mem.start = start; return tag; } //5.lib/String.c->memmove void * memmove(void * dest,const void *src,size_t count) {char *tmp, *s; if (dest <= src) {//如果dest在src的前面,那么顺序++拷贝绝对不会出现覆盖 tmp = (char *) dest; s = (char *) src; while (count--) *tmp++ = *s++; } else {//如果dest在src的后面,那么从+count处,倒着拷贝不会出现覆盖[gliethttp] tmp = (char *) dest + count; s = (char *) src + count; while (count--) *--tmp = *--s; } return dest; }
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