运行动态link的程序会被kill 的 bug 基本解决

2006/4/26 19:58:30

bug 暂时解决了，不过没有得到高手的认可：）， 既然高手认为我的想法有问题，我还得花时间去仔细看看

why does the code like this? 
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发件人：  konggangg...@163.com - 查看个人资料 
日期：  2006年4月24日(星期一) 下午9时40分  
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  hi, guys, when I run initramfs with klibc on mips platform, my 
program always be killed , I found that  it is because of the code 
below: 
unsigned long do_mmap_pgoff(struct file * file, unsigned long addr, 
                        unsigned long len, unsigned long prot, 
                        unsigned long flags, unsigned long pgoff) 
{ 
  .... 
        if (!len) 
                return -EINVAL;

        /* Careful about overflows.. */ 
        len = PAGE_ALIGN(len); 
        if (!len || len > TASK_SIZE) 
                return -ENOMEM; 
     .......

}

I'm wondering why return error when len == 0?

I think the correct code should be:

unsigned long do_mmap_pgoff(struct file * file, unsigned long addr, 
                        unsigned long len, unsigned long prot, 
                        unsigned long flags, unsigned long pgoff) 
{ 
  .... 
        if (!len) 
                return addr;

        /* Careful about overflows.. */ 
        len = PAGE_ALIGN(len); 
         if(!len) 
                  return addr;

        if (len > TASK_SIZE) 
                return -ENOMEM; 
     .......

}

have any idea?

thanks in advance! 
kong gang

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发件人：  Pete Zaitcev - 查看个人资料 
日期：  2006年4月25日(星期二) 上午3时07分  
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On Mon, 24 Apr 2006 06:40:53 -0700, kongganggang wrote: 
>    /* Careful about overflows.. */ 
>    len = PAGE_ALIGN(len); 
>    if (!len || len > TASK_SIZE) 
>            return -ENOMEM; 
>      ....... 
> }

> I'm wondering why return error when len == 0?

Because it's not. You passed -1 to len, most likely.

> I think the correct code should be:

No, it's not correct.

You better find out what's wrong with len. Consult with Peter if you 
think it's klibc's problem.

-- Pete

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发件人：  konggangg...@163.com - 查看个人资料 
日期：  2006年4月25日(星期二) 上午8时23分  
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>Because it's not. You passed -1 to len, most likely.

 do_mmap_pgoff return error because  the length of the data section of 
my program is 0.

 mips-linux-readelf -S mkdir 
There are 11 section headers, starting at offset 0x10dc:

Section Headers: 
  [Nr] Name              Type            Addr     Off    Size   ES Flg 
Lk Inf Al 
  [ 0]                   NULL            00000000 000000 000000 00 
0   0  0 
  [ 1] .interp           PROGBITS        004000d4 0000d4 00002a 00   A 
0   0  1 
  [ 2] .reginfo          MIPS_REGINFO    00400100 000100 000018 18   A 
0   0  4 
  [ 3] .text             PROGBITS        00400120 000120 000660 00  AX 
0   0 16 
  [ 4] .rodata           PROGBITS        00400780 000780 0000f0 00   A 
0   0 16 
  [ 5] .data             PROGBITS        10000000 001000 000000 00  WA 
0   0 16 
  [ 6] .sbss             NOBITS          10000000 001000 000004 00 WAp 
0   0  4 
  [ 7] .bss              NOBITS          10000010 00100c 000010 00  WA 
0   0 16 
  [ 8] .pdr              PROGBITS        00000000 00100c 000080 00 
0   0  4 
  [ 9] .mdebug.abi32     PROGBITS        00000000 00108c 000000 00 
0   0  1 
  [10] .shstrtab         STRTAB          00000000 00108c 00004e 00 
0   0  1 
Key to Flags: 
  W (write), A (alloc), X (execute), M (merge), S (strings) 
  I (info), L (link order), G (group), x (unknown) 
  O (extra OS processing required) o (OS specific), p (processor 
specific)

after I modified the code , it runs normally.

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发件人：  konggangg...@163.com - 查看个人资料 
日期：  2006年4月25日(星期二) 上午8时56分  
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i modified my kernel like this, it runs normally:

unsigned long do_mmap_pgoff(struct file * file, unsigned long addr, 
                        unsigned long len, unsigned long prot, 
                        unsigned long flags, unsigned long pgoff) 
{ 
  .... 
       if (!len) 
                return addr;

            /* Careful about overflows.. */ 
        len = PAGE_ALIGN(len); 
        if (!len || len > TASK_SIZE) 
                return -ENOMEM;

     .......

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