mkyaffs2image.c源码分析：main.c

/*
 * makeyaffs2image.c
 *
 * Makes a YAFFS2 file system image that can be used to load up a file system.
 * Uses default Linux MTD layout - search for "NAND LAYOUT" to change.
 */
 
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include "yaffs_ecc.h"
#include "yaffs_guts.h"

#include "yaffs_packedtags2.h"

unsigned yaffs_trace_mask=0;

#define MAX_OBJECTS 10000

// Adjust these to match your NAND LAYOUT:
#define chunkSize 2048//chunk erea sie per page(pageSize=chunk+spare)
#define spareSize 64//spare erea size per page
#define pagesPerBlock 64//how many pages per block

 

typedef struct
{
 dev_t dev;
 ino_t ino;
 int   obj;
} objItem;

static objItem obj_list[MAX_OBJECTS];
static int obj_id = YAFFS_NOBJECT_BUCKETS + 1;

static int n_obj, nDirectories, nPages;

static int outFile;

static int error;
static int savedErrno;

static int convert_endian = 0;

static void fatal(const char *fn)
{
 perror(fn);
 error |= 1;
 exit(error);
}

static int warn(const char *fn)
{
 savedErrno = errno;
 perror(fn);
 error |= 2;
 return error;
}

static int obj_compare(const void *a, const void * b)
{
  objItem *oa, *ob;
 
  oa = (objItem *)a;
  ob = (objItem *)b;
 
  if(oa->dev < ob->dev) return -1;
  if(oa->dev > ob->dev) return 1;
  if(oa->ino < ob->ino) return -1;
  if(oa->ino > ob->ino) return 1;
 
  return 0;
}

static void add_obj_to_list(dev_t dev, ino_t ino, int obj)
{
 if(n_obj < MAX_OBJECTS)
 {
  obj_list[n_obj].dev = dev;
  obj_list[n_obj].ino = ino;
  obj_list[n_obj].obj = obj;
  n_obj++;
  qsort(obj_list,n_obj,sizeof(objItem),obj_compare);
  
 }
 else
 {
  // oops! not enough space in the object array
  fprintf(stderr,"Not enough space in object array\n");
  exit(1);
 }
}

static int find_obj_in_list(dev_t dev, ino_t ino)
{
 objItem *i = NULL;
 objItem test;

 test.dev = dev;
 test.ino = ino;
 
 if(n_obj > 0)
 {
  i = bsearch(&test,obj_list,n_obj,sizeof(objItem),obj_compare);
 }

 if(i)
 {
  return i->obj;
 }
 return -1;
}

/* This little function converts a little endian tag to a big endian tag.
 * NOTE: The tag is not usable after this other than calculating the CRC
 * with.
 */
static void little_to_big_endian(struct yaffs_ext_tags *tagsPtr)
{
#if 0 // FIXME NCB
    union yaffs_tags_union * tags = (union yaffs_tags_union* )tagsPtr; // Work in bytes.
    union yaffs_tags_union   temp;

    memset(&temp, 0, sizeof(temp));
    // Ick, I hate magic numbers.
    temp.as_bytes[0] = ((tags->as_bytes[2] & 0x0F) << 4) | ((tags->as_bytes[1] & 0xF0) >> 4);
    temp.as_bytes[1] = ((tags->as_bytes[1] & 0x0F) << 4) | ((tags->as_bytes[0] & 0xF0) >> 4);
    temp.as_bytes[2] = ((tags->as_bytes[0] & 0x0F) << 4) | ((tags->as_bytes[2] & 0x30) >> 2) | ((tags->as_bytes[3] & 0xC0) >> 6);
    temp.as_bytes[3] = ((tags->as_bytes[3] & 0x3F) << 2) | ((tags->as_bytes[2] & 0xC0) >> 6);
    temp.as_bytes[4] = ((tags->as_bytes[6] & 0x03) << 6) | ((tags->as_bytes[5] & 0xFC) >> 2);
    temp.as_bytes[5] = ((tags->as_bytes[5] & 0x03) << 6) | ((tags->as_bytes[4] & 0xFC) >> 2);
    temp.as_bytes[6] = ((tags->as_bytes[4] & 0x03) << 6) | (tags->as_bytes[7] & 0x3F);
    temp.as_bytes[7] = (tags->as_bytes[6] & 0xFC) | ((tags->as_bytes[7] & 0xC0) >> 6);

    // Now copy it back.
    tags->as_bytes[0] = temp.as_bytes[0];
    tags->as_bytes[1] = temp.as_bytes[1];
    tags->as_bytes[2] = temp.as_bytes[2];
    tags->as_bytes[3] = temp.as_bytes[3];
    tags->as_bytes[4] = temp.as_bytes[4];
    tags->as_bytes[5] = temp.as_bytes[5];
    tags->as_bytes[6] = temp.as_bytes[6];
    tags->as_bytes[7] = temp.as_bytes[7];
#endif
}

static void shuffle_oob(char *spareData, struct yaffs_packed_tags2 *pt)
{
 assert(sizeof(*pt) <= spareSize);
 // NAND LAYOUT: For non-trivial OOB orderings, here would be a good place to shuffle.
 memcpy(spareData, pt, sizeof(*pt));
}

/*
struct yaffs_packed_tags2 {
    struct yaffs_packed_tags2_tags_only t;     //数据
    struct yaffs_ecc_other ecc;                       //校验信息
};
yaffs_packed_tags2是由数据和校难信息两部分组成的,但是这儿只用了数据不进行校验,所以内核里面也只是读出数据不校验
*/

static int write_chunk(u8 *data, u32 id, u32 chunk_id, u32 n_bytes)
{
 struct yaffs_ext_tags t;
 struct yaffs_packed_tags2 pt;
 char spareData[spareSize];

 if (write(outFile,data,chunkSize) != chunkSize)//一次将Page页中chunk区域全部写满。
  fatal("write");

 memset(&t, 0, sizeof(t));
 
 t.chunk_id = chunk_id;
// t.serial_number = 0;
 t.serial_number = 1; // **CHECK**
 t.n_bytes = n_bytes;
 t.obj_id = id;
 
 t.seq_number = YAFFS_LOWEST_SEQUENCE_NUMBER;

// added NCB **CHECK**
 t.chunk_used = 1;

 if (convert_endian)
 {
         little_to_big_endian(&t);
 }

 nPages++;

 memset(&pt, 0, sizeof(pt));
 yaffs_pack_tags2(&pt,&t,1);
 //函数将 yaffs_ext_tags转为yaffs_packed_tags2,并生成校验信息,但最最后一个参数为0(tag_ecc标志位),所以只保存转换的tag信息并不进行ecc校验更不会保存校验信息。
 memset(spareData, 0xff, sizeof(spareData));
 shuffle_oob(spareData, &pt);

 if (write(outFile,spareData,sizeof(spareData)) != sizeof(spareData))
  fatal("write");//将flash上oob区域的数据写到映像中(oob即spare区域).
 return 0;
}

#define SWAP32(x)   ((((x) & 0x000000FF) << 24) | \
                     (((x) & 0x0000FF00) << 8 ) | \
                     (((x) & 0x00FF0000) >> 8 ) | \
                     (((x) & 0xFF000000) >> 24))

#define SWAP16(x)   ((((x) & 0x00FF) << 8) | \
                     (((x) & 0xFF00) >> 8))
       
// This one is easier, since the types are more standard. No funky shifts here.
static void object_header_little_to_big_endian(struct yaffs_obj_hdr* oh)
{
    oh->type = SWAP32(oh->type); // GCC makes enums 32 bits.
    oh->parent_obj_id = SWAP32(oh->parent_obj_id); // int
    oh->sum_no_longer_used = SWAP16(oh->sum_no_longer_used); // u16 - Not used, but done for completeness.
    // name = skip. Char array. Not swapped.
    oh->yst_mode = SWAP32(oh->yst_mode);

    // Regular POSIX.
    oh->yst_uid = SWAP32(oh->yst_uid);
    oh->yst_gid = SWAP32(oh->yst_gid);
    oh->yst_atime = SWAP32(oh->yst_atime);
    oh->yst_mtime = SWAP32(oh->yst_mtime);
    oh->yst_ctime = SWAP32(oh->yst_ctime);

    oh->file_size_low = SWAP32(oh->file_size_low); // Aiee. An int... signed, at that!
    oh->file_size_high = SWAP32(oh->file_size_high); // Aiee. An int... signed, at that!
    oh->equiv_id = SWAP32(oh->equiv_id);
    // alias  - char array.
    oh->yst_rdev = SWAP32(oh->yst_rdev);

    oh->win_ctime[0] = SWAP32(oh->win_ctime[0]);
    oh->win_ctime[1] = SWAP32(oh->win_ctime[1]);
    oh->win_atime[0] = SWAP32(oh->win_atime[0]);
    oh->win_atime[1] = SWAP32(oh->win_atime[1]);
    oh->win_mtime[0] = SWAP32(oh->win_mtime[0]);
    oh->win_mtime[1] = SWAP32(oh->win_mtime[1]);

    oh->reserved[0] = SWAP32(oh->reserved[0]);
    oh->reserved[1] = SWAP32(oh->reserved[1]);

    oh->inband_shadowed_obj_id = SWAP32(oh->inband_shadowed_obj_id);
    oh->inband_is_shrink = SWAP32(oh->inband_is_shrink);
    oh->shadows_obj = SWAP32(oh->shadows_obj);
    oh->is_shrink = SWAP32(oh->is_shrink);
}

static int write_object_header(int id, enum yaffs_obj_type t, struct stat *s, int parent, const char *name, int equivalentObj, const char * alias)
{
 u8 bytes[chunkSize];
 
 struct yaffs_obj_hdr *oh = (struct yaffs_obj_hdr *)bytes;
 
 memset(bytes,0xff,sizeof(bytes));
 
 oh->type = t;

 oh->parent_obj_id = parent;
 
 if (strlen(name)+1 > sizeof(oh->name))
 {
  errno = ENAMETOOLONG;
  return warn("object name");
 }
 memset(oh->name,0,sizeof(oh->name));
 strcpy(oh->name,name);
 
 
 if(t != YAFFS_OBJECT_TYPE_HARDLINK)
 {
  oh->yst_mode = s->st_mode;
  oh->yst_uid = s->st_uid;
// NCB 12/9/02  oh->yst_gid = s->yst_uid;
  oh->yst_gid = s->st_gid;
  oh->yst_atime = s->st_atime;
  oh->yst_mtime = s->st_mtime;
  oh->yst_ctime = s->st_ctime;
  oh->yst_rdev  = s->st_rdev;
 }
 
 if(t == YAFFS_OBJECT_TYPE_FILE)
 {
  oh->file_size_low = s->st_size;
  oh->file_size_high = (s->st_size >> 32);
 }
 
 if(t == YAFFS_OBJECT_TYPE_HARDLINK)
 {
  oh->equiv_id = equivalentObj;
 }
 
 if(t == YAFFS_OBJECT_TYPE_SYMLINK)
 {
  if (strlen(alias)+1 > sizeof(oh->alias))
  {
   errno = ENAMETOOLONG;
   return warn("object alias");
  }
  memset(oh->alias,0,sizeof(oh->alias));
  strcpy(oh->alias,alias);
 }

 if (convert_endian)
 {
      object_header_little_to_big_endian(oh);
 }
 
 return write_chunk(bytes,id,0,0xffff);
 
}

static void pad_image(void)
{
 u8 data[chunkSize + spareSize];
 int padPages = (nPages % pagesPerBlock);

 if (padPages)
 {
  memset(data, 0xff, sizeof(data));
  for (padPages = pagesPerBlock-padPages; padPages; padPages--)
  {
   if (write(outFile, data, sizeof(data)) != sizeof(data))
    fatal("write");
  }
 }
}

static int process_directory(int parent, const char *path)
{

 DIR *dir;
 struct dirent *entry;

 nDirectories++;
 
 dir = opendir(path);//根据传入的路径，打开目录
 if(!dir)
 {
  warn("opendir");
 }
 else
 {
  while((entry = readdir(dir)) != NULL)//依次遍历打开目录中的所有子目录
  {
  
   /* Ignore . and .. */
   if(strcmp(entry->d_name,".") &&
      strcmp(entry->d_name,".."))
    {
     char full_name[500];
    struct stat stats;
    int equivalentObj;
    int newObj;
    
    if (snprintf(full_name,sizeof(full_name),"%s/%s",path,entry->d_name) >= (int)sizeof(full_name))
    {//构造文件的路径(目录文件、FIFO管道文件、字符文件、套接字等)
     error = -1;
     continue;
    }
    
    if (lstat(full_name,&stats) < 0)
    {//获取该文件的stat信息。
     warn("lstat");
     continue;
    }
    
    if(S_ISLNK(stats.st_mode) ||
        S_ISREG(stats.st_mode) ||
        S_ISDIR(stats.st_mode) ||
        S_ISFIFO(stats.st_mode) ||
        S_ISBLK(stats.st_mode) ||
        S_ISCHR(stats.st_mode) ||
        S_ISSOCK(stats.st_mode))
    {//若该文件是链接文件、目录文件、字符文件...会处理，其他类型则不处理
    
     newObj = obj_id++;
     n_obj++;
     
     printf("Object %d, %s is a ",newObj,full_name);
     
     /* We're going to create an object for it */
     if((equivalentObj = find_obj_in_list(stats.st_dev, stats.st_ino)) > 0)
     {
       /* we need to make a hard link */
       printf("hard link to object %d\n",equivalentObj);
      write_object_header(newObj, YAFFS_OBJECT_TYPE_HARDLINK, &stats, parent, entry->d_name, equivalentObj, NULL);
     }
     else
     {
      
      add_obj_to_list(stats.st_dev,stats.st_ino,newObj);
      
      if(S_ISLNK(stats.st_mode))
      {
     
       char symname[500];
      
       memset(symname,0, sizeof(symname));
     
       if (readlink(full_name,symname,sizeof(symname) -1) < 0)
       {
        warn("readlink");
       }
       else
       {
        printf("symlink to \"%s\"\n",symname);
        write_object_header(newObj, YAFFS_OBJECT_TYPE_SYMLINK, &stats, parent, entry->d_name, -1, symname);
       }
      }
      else if(S_ISREG(stats.st_mode))//如果该文件是普通文件
      {
       printf("file, ");
       if(write_object_header(newObj, YAFFS_OBJECT_TYPE_FILE, &stats, parent, entry->d_name, -1, NULL) == 0)
       {//先写入文件头。
        int h;
        u8 bytes[chunkSize];
        int n_bytes;
        int chunk = 0;
        
        h = open(full_name,O_RDONLY);
        if(h >= 0)
        {
         memset(bytes,0xff,sizeof(bytes));
         while((n_bytes = read(h,bytes,sizeof(bytes))) > 0)
         {
          chunk++;
          write_chunk(bytes,newObj,chunk,n_bytes);//再写入文件内容
          memset(bytes,0xff,sizeof(bytes));
         }
         if(n_bytes < 0)
            warn("read");
           
         printf("%d data chunks written\n",chunk);
         close(h);
        }
        else
        {
         warn("open");
        }
        
       }       
              
      }
      else if(S_ISSOCK(stats.st_mode))
      {//如果是套接字文件、fifo管道文件、字符文件、块设备文件或目录文件，则只写入文件头即可。
       printf("socket\n");
       write_object_header(newObj, YAFFS_OBJECT_TYPE_SPECIAL, &stats, parent, entry->d_name, -1, NULL);
      }
      else if(S_ISFIFO(stats.st_mode))
      {
       printf("fifo\n");
       write_object_header(newObj, YAFFS_OBJECT_TYPE_SPECIAL, &stats, parent, entry->d_name, -1, NULL);
      }
      else if(S_ISCHR(stats.st_mode))
      {
       printf("character device\n");
       write_object_header(newObj, YAFFS_OBJECT_TYPE_SPECIAL, &stats, parent, entry->d_name, -1, NULL);
      }
      else if(S_ISBLK(stats.st_mode))
      {
       printf("block device\n");
       write_object_header(newObj, YAFFS_OBJECT_TYPE_SPECIAL, &stats, parent, entry->d_name, -1, NULL);
      }
      else if(S_ISDIR(stats.st_mode))
      {
       printf("directory\n");
       if (write_object_header(newObj, YAFFS_OBJECT_TYPE_DIRECTORY, &stats, parent, entry->d_name, -1, NULL) == 0)
        process_directory(newObj,full_name);
      }//若是目录文件则只写入文件头，并把这次的newObj作为parent继续处理其子目录下的内容
     }
    }
    else
    {
     fprintf(stderr, "%s: unhandled type\n", full_name);
     error |= 2;
     savedErrno = EINVAL;
    }//目前只处理链接文件、FIFO管道文件、目录文件、字符文件等7中文件类型。
   }//如果目录下内容为.或..  则不做任何处理直接进行while的下次循环(即打开下一个子目录)。
  }//传入路径中的所有子目录都已经遍历完毕。
  closedir(dir);
 }
 
 return 0;

}

int main(int argc, char *argv[])
{
 struct stat stats;
 
 printf("mkyaffs2image: image building tool for YAFFS2 built "__DATE__"\n");
 
 if(argc < 3)
 {
  printf("usage: mkyaffs2image dir image_file [convert]\n");
  printf("           dir        the directory tree to be converted\n");
  printf("           image_file the output file to hold the image\n");
        printf("           'convert'  produce a big-endian image from a little-endian machine\n");
  exit(1);
 }

    if ((argc == 4) && (!strncmp(argv[3], "convert", strlen("convert"))))
    {
        convert_endian = 1;
    }
   
 if(stat(argv[1],&stats) < 0)
 {
  printf("Could not stat %s\n",argv[1]);
  exit(1);
 }
 
 if(!S_ISDIR(stats.st_mode))//保证argv[1]必须是一个目录
 {
  printf(" %s is not a directory\n",argv[1]);
  exit(1);
 }
 
 outFile = open(argv[2],O_CREAT | O_TRUNC | O_WRONLY, S_IREAD | S_IWRITE);
 //创建并打开一个文件，该文件的fd句柄赋值给全局变量outFile
 
 if(outFile < 0)
 {
  printf("Could not open output file %s\n",argv[2]);
  exit(1);
 }
 
 printf("Processing directory %s into image file %s\n",argv[1],argv[2]);
 process_directory(YAFFS_OBJECTID_ROOT,argv[1]);//将rootfs目录中的所有内容写到outFile中
 
 pad_image();//将映像文件扩充到block对齐。

 close(outFile);
 
 if(error)
 {
  errno = savedErrno;
  perror("operation incomplete");
 }
 else
 {
  printf("Operation complete.\n"
         "%d objects in %d directories\n"
         "%d NAND pages\n",n_obj, nDirectories, nPages);
 }
 
 exit(error);
}