內核模塊沒有在llseek中分配變量

我正在寫一個字符設備內核模塊，並且遇到了一個非常奇怪的問題。我將變量設置爲某些值，但當我使用printk（）打印它們時，我沒有收到這些值。這裏是我的代碼（過度的printk）：內核模塊沒有在llseek中分配變量

loff_t llseek(struct file *filp, loff_t off, int whence) 
{ 
    printk(KERN_NOTICE "In llseek\n"); 
printk(KERN_NOTICE "filp->f_pos = 0x%llX\n",filp->f_pos); 
printk(KERN_NOTICE "off = 0x%llX\n", off); 

loff_t newpos; 

switch(whence) { 
    case 0: /* SEEK_SET */ 
     printk(KERN_NOTICE "SEEK_SET\n"); 
     newpos = off; 
     printk(KERN_NOTICE "1] newpos = 0x%X\n",newpos); 
     printk(KERN_NOTICE "2] newpos = 0x%X\n",newpos); 
     break; 

    case 1: /* SEEK_CUR */ 
    newpos = filp->f_pos + off; 
    printk(KERN_NOTICE "SEEK_CUR\n"); 
    break; 

    case 2: /* SEEK_END */ 
     newpos = 0x1000 + off; 
     printk(KERN_NOTICE "SEEK_END\n"); 
     break; 

    default: /* can't happen */ 
     return -EINVAL; 
} 
printk(KERN_NOTICE "3] newpos = 0x%X\n",newpos); 
if (newpos < 0) return -EINVAL; 
printk(KERN_NOTICE "4] newpos = 0x%X\n",newpos); 
filp->f_pos = newpos; 
printk(KERN_NOTICE "5] newpos = 0x%lX\n", newpos); 
return newpos; 
}

這是從用戶空間調用此：

lseek(dev_fd, 0x90, 0);

這裏是控制檯輸出：

[ 53.764351] In llseek 
[ 53.766208] filp->f_pos = 0x0 
[ 53.768629] off = 0x90 
[ 53.770560] SEEK_SET 
[ 53.772341] 1] newpos = 0xC139D40C 
[ 53.775117] 2] newpos = 0x0 
[ 53.777395] 3] newpos = 0x0 
[ 53.779680] 4] newpos = 0x0 
[ 53.781959] 5] newpos = 0xC139D40C

我會預計產量爲：

[ 53.764351] In llseek 
[ 53.766208] filp->f_pos = 0x0 
[ 53.768629] off = 0x90 
[ 53.770560] SEEK_SET 
[ 53.772341] 1] newpos = 0x90 
[ 53.775117] 2] newpos = 0x90 
[ 53.777395] 3] newpos = 0x90 
[ 53.779680] 4] newpos = 0x90 
[ 53.781959] 5] newpos = 0x90

爲什麼會newpos變化與printk的

來源

2014-06-18 whh4000

的兩個連續呼叫的價值有時你用「％X」有時「％LX」有時「％LLX」。這些都希望不同的類型在變量參數中傳遞。

隨着loff_t，他們應該可能都是「％llX」

來源

2014-06-19 15:56:03

內核模塊沒有在llseek中分配變量

回答

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