armlinux内核启动－－内存初始化管理

一时失言乱红尘 2022-03-26 15:48 411阅读 0赞

linux版本:2.6.36  
相关数据结构  
arch/arm/include/asm/setup.h  
\#ifdef CONFIG\_ARCH\_LH7A40X  
\# define NR\_BANKS 16  
\#else  
\# define NR\_BANKS 8  
\#endif  
  
struct membank \{  
    unsigned long start;  
    unsigned long size;  
    unsigned int highmem;  
\};  
  
struct meminfo \{  
    int nr\_banks;  
    struct membank bank\[NR\_BANKS\];  
\};  
linux内核的内存管理分三个阶段。  
1. 启动---->bootmem初始化完成为第一阶段。此阶段只能使用memblock\_reserve函数分配内存。  
   此阶段结束标志为：init\_bootmem\_done = 1.  
2. bootmem初始化完--->buddy完成前。结束标志为mem\_init\_done = 1.  
3. 全部内存初始化完毕，可以用cache和buddy分配内存。  
  
内存初始化步骤：  
1. start\_kernel---->setup\_arch->pageing\_init  
                |-->setup\_per\_cpu\_areas  
                |-->build\_all\_zonelists  
                |-->mem\_init  
                 -->setup\_per\_cpu\_pageset  
setup\_arch-->arm\_memblock\_init-->memblock\_init  
  
内存原始数据由u-boot传入,对照本开发板uboot部分内存初始化函数，我们知道uboot传递过来的tag->u.mem.start, tag->u.mem.size分别为0x30000000,0x4000000，即内存起始地址是0x30000000，大小为64M，start\_arch获取u-boot传递的参数地址后，调用了parse\_tag\_mem32函数对传递的内存参数处理：  
556 static int \_\_init parse\_tag\_mem32(const struct tag \*tag)  
557 \{  
558         return arm\_add\_memory(tag->u.mem.start, tag->u.mem.size);  
559 \}  
560  
561 \_\_tagtable(ATAG\_MEM, parse\_tag\_mem32);  
如上可见，parse\_tag\_mem32函数调用arm\_add\_memory函数把RAM的start和size等参数保存到了meminfo结构的 meminfo结构体中。现在再来分析arm\_add\_memory  
arm\_add\_memory定义如下（arch/arm/kernel/setup.c)  
static int \_\_init arm\_add\_memory(unsigned long start, unsigned long size)  
\{  
    struct membank \*bank = &meminfo.bank\[meminfo.nr\_banks\];  
  
    if (meminfo.nr\_banks >= NR\_BANKS) \{  
        printk(KERN\_CRIT "NR\_BANKS too low, "  
            "ignoring memory at %\#lx\\n", start);  
        return -EINVAL;  
    \}  
  
    /\*  
     \* Ensure that start/size are aligned to a page boundary.  
     \* Size is appropriately rounded down, start is rounded up.  
     \*/  
    size -= start & ~PAGE\_MASK;  
    bank->start = PAGE\_ALIGN(start);  
    bank->size  = size & PAGE\_MASK;  
  
    /\*  
     \* Check whether this memory region has non-zero size or  
     \* invalid node number.  
     \*/  
    if (bank->size == 0)  
        return -EINVAL;  
  
    meminfo.nr\_banks++;  
    return 0;  
\}  
经过这样的处理，setup.c文件中的meminfo可就不再是  
struct meminfo meminfo  = \{ 0, \};  
而是  
struct meminfo meminfo  = \{ 1,\{0x30000000,0x4000000,0\},\{\}, \};  
表示当前有一个内存区域，物理地址是从0x30000000开始，大小是64M,节点是0  
处理完这些数据后，start\_arch会调用第822行调用arm\_memblock\_init(&meminfo, mdesc);  
先分析第1阶段。  
1. 初始化：setup\_arch-->arm\_memblock\_init-->memblock\_init  
arch/arm/mm/init.c  
270 void \_\_init arm\_memblock\_init(struct meminfo \*mi, struct machine\_desc \*mdesc)  
271 \{  
272         int i;  
273  
274         memblock\_init();  
275         for (i = 0; i < mi->nr\_banks; i++)  
276                 memblock\_add(mi->bank\[i\].start, mi->bank\[i\].size);  
277  
278         /\* Register the kernel text, kernel data and initrd with memblock. \*/  
279 \#ifdef CONFIG\_XIP\_KERNEL //配置内核XIP方式运行，避免把内核从Nor  Flash 拷贝到主存 SDRAM 空间，让内核运行在低功耗的NOR flash 上，节省系统启动时间，降低系统对SDRAM 的需要，减少电能消耗，使产品能够持续使用更长时间  
280         memblock\_reserve(\_\_pa(\_data), \_end - \_data);  
281 \#else  
282         memblock\_reserve(\_\_pa(\_stext), \_end - \_stext);  
/\*第282行，在０节点中保留内核镜像部分的内存，大概是0x30108000到以后的5M左右(解压后的内核)。  
参看arch/arm/kernel/vmlinux.lds文件，  
375 SECTIONS  
376 \{  
377  . = 0xC0000000 + 0x00108000;  
378  .init : \{ /\* Init code and data                \*/  
379   \_stext = .;  
所以stext等于c0108000,对应物理地址30108000,  
对\_end再参看arch/arm/kernel/vmlinux.lds.S文件,它也在SECTIONS区，在233行定义  
232         BSS\_SECTION(0, 0, 0)  
233         \_end = .;  
对于我移植的2.3.36内核，\_end等于c0555b60,对应物理地址30555b60，在此语句后添加打印信息得到  
\_end - \_stext=44db60，4.512608M大小,所以这一句功能就是把0x30108000　～　0x30555b60这段(4.512608M)空间保留下来。               
\*/  
283 \#endif  
284 \#ifdef CONFIG\_BLK\_DEV\_INITRD //本开发板没配置  
285         if (phys\_initrd\_size) \{  
286                 memblock\_reserve(phys\_initrd\_start, phys\_initrd\_size);  
287  
288                 /\* Now convert initrd to virtual addresses \*/  
289                 initrd\_start = \_\_phys\_to\_virt(phys\_initrd\_start);  
290                 initrd\_end = initrd\_start + phys\_initrd\_size;  
291         \}  
292 \#endif  
293  
294         arm\_mm\_memblock\_reserve();//就是把0x30104000　～　0x30108000这段(16K)用于页目录的内容保留下来。  
295  
296         /\* reserve any platform specific memblock areas \*/  
297         if (mdesc->reserve)//对st2410中没有定义  
298                 mdesc->reserve();  
299  
300         memblock\_analyze();//计算内存块大小  
301         memblock\_dump\_all();//显示  
302 \}  
 内存原始数据由u-boot传入，在初始化完memblock\_init后，arm\_memblock\_init函数中memblock\_add调用 memblock\_add\_region加入原始内存数据，我的板子上配了64M内存，即：0x0000 0000->0x40000000,加完后的配置如下：  
MEMBLOCK configuration:                                                          
 rmo\_size    = 0x0                                                               
 memory.size = 0x4000000                                                         
 memory.cnt  = 0x1                                                               
 memory\[0x0\]    0x0000000030000000 - 0x0000000033ffffff, 0x4000000 bytes         
 reserved.cnt  = 0x1                                                             
 reserved\[0x0\]  0x0000000030104000 - 0x0000000030555b5f, 0x451b60 bytes   
  
memblock\_init()在mm/memblock.c里面被定义。  
void \_\_init memblock\_init(void)  
\{  
    /\* Create a dummy zero size MEMBLOCK which will get coalesced away later.  
     \* This simplifies the memblock\_add() code below...  
     \*/  
    memblock.memory.region\[0\].base = 0;  
    memblock.memory.region\[0\].size = 0;  
    memblock.memory.cnt = 1;  
  
    /\* Ditto. \*/  
    memblock.reserved.region\[0\].base = 0;  
    memblock.reserved.region\[0\].size = 0;  
    memblock.reserved.cnt = 1;  
\}  
其作用就是初始化memblock这个结构。将他们清空。memblock包含两个重要的成员，分别是memblock.memory和memblock.reserved.其分别代表系统中可用的内存和已经被保留的内存。  
memblock.memory和memblock.reserved被定义为以下结构：include/linux/memblock.h  
\#define MAX\_MEMBLOCK\_REGIONS 128  
  
struct memblock\_property \{  
    u64 base;  
    u64 size;  
\};  
  
struct memblock\_region \{  
    unsigned long cnt;  
    u64 size;  
    struct memblock\_property region\[MAX\_MEMBLOCK\_REGIONS+1\];  
\};  
  
struct memblock \{  
    unsigned long debug;  
    u64 rmo\_size;  
    struct memblock\_region memory;  
    struct memblock\_region reserved;  
\};  
  
  
mm/memblock.c  
long memblock\_add(u64 base, u64 size)  
\{  
    struct memblock\_region \*\_rgn = &memblock.memory;  
  
    /\* On pSeries LPAR systems, the first MEMBLOCK is our RMO region. \*/  
    if (base == 0)  
        memblock.rmo\_size = size;  
  
    return memblock\_add\_region(\_rgn, base, size);  
  
\}  
  
static long memblock\_add\_region(struct memblock\_region \*rgn, u64 base, u64 size)  
\{  
    unsigned long coalesced = 0;  
    long adjacent, i;  
  
    if ((rgn->cnt == 1) && (rgn->region\[0\].size == 0)) \{  
        rgn->region\[0\].base = base;  
        rgn->region\[0\].size = size;  
        return 0;  
    \}  
  
    /\* First try and coalesce this MEMBLOCK with another. \*/  
    for (i = 0; i < rgn->cnt; i++) \{  
        u64 rgnbase = rgn->region\[i\].base;  
        u64 rgnsize = rgn->region\[i\].size;  
  
        if ((rgnbase == base) && (rgnsize == size))  
            /\* Already have this region, so we're done \*/  
            return 0;  
  
        adjacent = memblock\_addrs\_adjacent(base, size, rgnbase, rgnsize);  
        if (adjacent > 0) \{  
            rgn->region\[i\].base -= size;  
            rgn->region\[i\].size += size;  
            coalesced++;  
            break;  
        \} else if (adjacent < 0) \{  
            rgn->region\[i\].size += size;  
            coalesced++;  
            break;  
        \}  
    \}  
  
    if ((i < rgn->cnt - 1) && memblock\_regions\_adjacent(rgn, i, i+1)) \{  
        memblock\_coalesce\_regions(rgn, i, i+1);  
        coalesced++;  
    \}  
  
    if (coalesced)  
        return coalesced;  
    if (rgn->cnt >= MAX\_MEMBLOCK\_REGIONS)  
        return -1;  
  
    /\* Couldn't coalesce the MEMBLOCK, so add it to the sorted table. \*/  
    for (i = rgn->cnt - 1; i >= 0; i--) \{  
        if (base < rgn->region\[i\].base) \{  
            rgn->region\[i+1\].base = rgn->region\[i\].base;  
            rgn->region\[i+1\].size = rgn->region\[i\].size;  
        \} else \{  
            rgn->region\[i+1\].base = base;  
            rgn->region\[i+1\].size = size;  
            break;  
        \}  
    \}  
  
    if (base < rgn->region\[0\].base) \{  
        rgn->region\[0\].base = base;  
        rgn->region\[0\].size = size;  
    \}  
    rgn->cnt++;  
  
    return 0;  
\}  
memblock\_add\_region函数作用是将给定的物理地址所指定的memory region加入到指定的memblock（memblock.reserved或者是memblock.memory）中。新加入的memory region需要经过检查，如果与原先的memory region有重叠，则需要合并在原先的memory region中，否则的话就新建一个memory region.  
3. memblock\_reserve用来分配内存页。  
以分配内核本身占用的内存为例：  
/\* Register the kernel text, kernel data and initrd with memblock. \*/  
memblock\_reserve(\_\_pa(\_stext), \_end - \_stext);  
\_stext,\_end参见arch/arm/kernel/vmlinux.lds.S 链接脚本  
long \_\_init memblock\_reserve(u64 base, u64 size)  
\{  
    struct memblock\_region \*\_rgn = &memblock.reserved;  
  
    BUG\_ON(0 == size);  
  
    return memblock\_add\_region(\_rgn, base, size);  
\}  
分配完之后的内存配置为：  
MEMBLOCK configuration:  
 rmo\_size    = 0x40000000  
 memory.size = 0x0  
 memory.cnt  = 0x1  
 memory\[0x0\]    0x0000000000000000 - 0x000000003fffffff, 0x40000000 bytes  
 reserved.cnt  = 0x1  
 reserved\[0x0\]  0x0000000000000000 - 0x0000000000xxxxx,  \_end - \_stext bytes  
如果分配有连续则进行合并。  
几次分配后的配置如下：  
MEMBLOCK configuration:  
 rmo\_size    = 0x80000000  
 memory.size = 0x80000000  
 memory.cnt  = 0x1  
 memory\[0x0\]    0x0000000000000000 - 0x000000007fffffff, 0x80000000 bytes  
 reserved.cnt  = 0x6  
 reserved\[0x0\]  0x0000000000000000 - 0x00000000006b0fff, 0x6b1000 bytes  
 reserved\[0x1\]  0x0000000000ffa000 - 0x0000000000ffcfff, 0x3000 bytes  
 reserved\[0x2\]  0x000000002fbc4000 - 0x000000002fbdefff, 0x1b000 bytes  
 reserved\[0x3\]  0x000000002fbdfa88 - 0x000000002ffff4cc, 0x41fa45 bytes  
 reserved\[0x4\]  0x000000002fbe4000 - 0x000000002ffff4cd, 0x41b4ce bytes  
 reserved\[0x5\]  0x000000007ffff000 - 0x000000007fffffff, 0x1000 bytes  
init  
  
arch/arm/mm/mmu.c  
/\*  
 \* Reserve the special regions of memory  
 \*/  
void \_\_init arm\_mm\_memblock\_reserve(void)  
\{  
    /\*  
     \* Reserve the page tables.  These are already in use,  
     \* and can only be in node 0.  
     \*/  
    memblock\_reserve(\_\_pa(swapper\_pg\_dir), PTRS\_PER\_PGD \* sizeof(pgd\_t));  
/\*  
相关的信息  
swapper\_pg\_dir是初始化页表虚拟地址，它在  
./arch/arm/kernel/head.S定义  
44:    .globl  swapper\_pg\_dir  
45:    .equ    swapper\_pg\_dir, KERNEL\_RAM\_VADDR - 0x4000  
./arch/arm/kernel/head.S:55:\#define KERNEL\_START        KERNEL\_RAM\_VADDR  
所以swapper\_pg\_dir等于0xc0104000，对应物理地址0x30104000  
PTRS\_PER\_PGD在arch/arm/include/asm/pgtable.h第103行定义  
\#define PTRS\_PER\_PGD        2048  
而pgd\_t定义为  
typedef unsigned long pgd\_t\[2\];  
PTRS\_PER\_PGD \* sizeof(pgd\_t)＝2048\*8=16384的大小为0x00004000 (16K)  
就是把0x30104000　～　0x30108000这段(16K)用于页目录的内容保留下来。  
\*/  
\#ifdef CONFIG\_SA1111 //2410没定义  
    /\*  
     \* Because of the SA1111 DMA bug, we want to preserve our  
     \* precious DMA-able memory...  
     \*/  
    memblock\_reserve(PHYS\_OFFSET, \_\_pa(swapper\_pg\_dir) - PHYS\_OFFSET);  
\#endif  
\}  
  
arch/arm/mm/init.c  
\#define MLK(b, t) b, t, ((t) - (b)) >> 10 //右移10位为K  
\#define MLM(b, t) b, t, ((t) - (b)) >> 20  //右移20位为M  
\#define MLK\_ROUNDUP(b, t) b, t, DIV\_ROUND\_UP(((t) - (b)), SZ\_1K)  
        printk(KERN\_NOTICE "Virtual kernel memory layout:\\n"  
                        "    vector  : 0x%08lx - 0x%08lx   (%4ld kB)\\n"  
                        "    fixmap  : 0x%08lx - 0x%08lx   (%4ld kB)\\n"  
\#ifdef CONFIG\_MMU  
                        "    DMA     : 0x%08lx - 0x%08lx   (%4ld MB)\\n"  
\#endif  
                        "    vmalloc : 0x%08lx - 0x%08lx   (%4ld MB)\\n"  
                        "    lowmem  : 0x%08lx - 0x%08lx   (%4ld MB)\\n"  
\#ifdef CONFIG\_HIGHMEM  
                        "    pkmap   : 0x%08lx - 0x%08lx   (%4ld MB)\\n"  
\#endif  
                        "    modules : 0x%08lx - 0x%08lx   (%4ld MB)\\n"  
                        "      .init : 0x%p" " - 0x%p" "   (%4d kB)\\n"  
                        "      .text : 0x%p" " - 0x%p" "   (%4d kB)\\n"  
                        "      .data : 0x%p" " - 0x%p" "   (%4d kB)\\n",  
  
                        MLK(UL(CONFIG\_VECTORS\_BASE), UL(CONFIG\_VECTORS\_BASE) +  
                                (PAGE\_SIZE)),  
                        MLK(FIXADDR\_START, FIXADDR\_TOP),  
\#ifdef CONFIG\_MMU  
                        MLM(CONSISTENT\_BASE, CONSISTENT\_END),  
\#endif  
                        MLM(VMALLOC\_START, VMALLOC\_END),  
                        MLM(PAGE\_OFFSET, (unsigned long)high\_memory),  
\#ifdef CONFIG\_HIGHMEM  
                        MLM(PKMAP\_BASE, (PKMAP\_BASE) + (LAST\_PKMAP) \*  
                                (PAGE\_SIZE)),  
\#endif  
                        MLM(MODULES\_VADDR, MODULES\_END),  
  
                        MLK\_ROUNDUP(\_\_init\_begin, \_\_init\_end),  
                        MLK\_ROUNDUP(\_text, \_etext),  
                        MLK\_ROUNDUP(\_data, \_edata));  
  
 系统启动的时候打印出：  
stext:c0108000,\_\_pa\_stext:30108000, \_end - \_stext=44db60                
\_end:c0555b60,\_\_pa(\_end)=30555b60      
Memory: 64MB = 64MB total                                               
Memory: 60536k/60536k available, 5000k reserved, 0K highmem             
Virtual kernel memory layout:                                           
    vector  : 0xffff0000 - 0xffff1000   (   4 kB)                       
    fixmap  : 0xfff00000 - 0xfffe0000   ( 896 kB)                       
    DMA     : 0xffc00000 - 0xffe00000   (   2 MB)                       
    vmalloc : 0xc4800000 - 0xe0000000   ( 440 MB)                       
    lowmem  : 0xc0000000 - 0xc4000000   (  64 MB)                       
    modules : 0xbf000000 - 0xc0000000   (  16 MB)                       
      .init : 0xc0108000 - 0xc012e000   ( 152 kB)---->(系统启动过程中 以\_\_init宏标识的函数占用的空间 被vmlinux.lds标识为 \_\_init\_begin \_\_init\_end 启动init进程前被释放掉 :Freeing init memory: 152K)                       
      .text : 0xc012e000 - 0xc04dd000   (3772 kB)                       
      .data : 0xc04fe000 - 0xc0527500   ( 166 kB)                       
Hierarchical RCU implementation.  
启动后查看内存命令显示如下：  
\[root@localhost /\]\# free                                                
              total         used         free       shared      buffers  
  Mem:        60688         6644        54044            0            0  
 Swap:            0            0            0                           
Total:        60688         6644        54044                           
\[root@localhost /\]\#     
  
保留内存5000K中 linux内核占用了152+3772+166=4090K  
加上boot的时候参数等平台空间占用32K = 3149K  
其它还差3464-3149=315K 没有着落  
其它还包括影射的向量表4K  
还有可能是系统管理内存的页表占用空间等其它的占用  
  
系统启动成功后 Freeing init memory: 100K  
所以用free命令看会多了100K  
  
而free命令中看到的used基本是缓存 buffer占用的,为了提高i/o速度的缓存,很多都并非真正应用  
在我应用中去试图malloc更多的内存的时候 used中很多都能被malloc出来的.  
  
mm/memblock.c  
void \_\_init memblock\_analyze(void)  
\{  
    int i;  
  
    memblock.memory.size = 0;  
  
    for (i = 0; i < memblock.memory.cnt; i++)  
        memblock.memory.size += memblock.memory.region\[i\].size;  
\}  
mm/memblock.c  
static void memblock\_dump(struct memblock\_region \*region, char \*name)  
\{  
    unsigned long long base, size;  
    int i;  
  
    pr\_info(" %s.cnt  = 0x%lx\\n", name, region->cnt);  
  
    for (i = 0; i < region->cnt; i++) \{  
        base = region->region\[i\].base;  
        size = region->region\[i\].size;  
  
        pr\_info(" %s\[0x%x\]\\t0x%016llx - 0x%016llx, 0x%llx bytes\\n",  
            name, i, base, base + size - 1, size);  
    \}  
\}  
mm/memblock.c  
void memblock\_dump\_all(void)  
\{  
    if (!memblock\_debug)  
        return;  
  
    pr\_info("MEMBLOCK configuration:\\n");  
    pr\_info(" rmo\_size    = 0x%llx\\n", (unsigned long long)memblock.rmo\_size);  
    pr\_info(" memory.size = 0x%llx\\n", (unsigned long long)memblock.memory.size);  
  
    memblock\_dump(&memblock.memory, "memory");  
    memblock\_dump(&memblock.reserved, "reserved");  
\}  
  
 22 static int memblock\_debug;  
 23  
 24 static int \_\_init early\_memblock(char \*p)  
 25 \{  
 26         if (p && strstr(p, "debug"))  
 27                 memblock\_debug = 1;  
 28         return 0;  
 29 \}  
 30 early\_param("memblock", early\_memblock);