Linux参数传递

最近内核态和用户态传递参数出现了一些问题

1.假设传递16K的数据打印信息，发现只打印了4k数据

typedef struct {
  unsigned int type;
  unsigned int addr;
  unsigned int len;
  unsigned int cmd;
  unsigned int *prv;
}fpga_opt_t;

static int wmsc_ioctl(struct inode *inode,struct file *file,unsigned int cmd,unsigned long arg)
{
fpga_opt_t tmp;
fpga_opt_t *ptmp = &tmp;

switch(cmd)
{
case 3094:
printk("\nwmsc_write is write ram is:\n");
copy_from_user((unsigned char *)ptmp,(unsigned char *)arg,sizeof(fpga_opt_t));

start =4093;
for( i=start; i<(start +16); i++){
if( i%8 ==0)
printk("\n");
printk("0x%04x ",*( (unsigned char *)( ( (fpga_opt_t *)ptmp)->prv +i)) );
}
break;
}

解决方法：因为结构体中是数组指针，所以需要copy两次

2.在ioctl中copy_from_user出现死机

typedef struct {
  unsigned int type;
  unsigned int addr;
  unsigned int len;
  unsigned int cmd;
  unsigned int prv[8192];
}fpga_opt_t;

static int wmsc_ioctl(struct inode *inode,struct file *file,unsigned int cmd,unsigned long arg)
{
fpga_opt_t tmp;
fpga_opt_t *ptmp = &tmp;

switch(cmd)
{
case 3094:
printk("\nwmsc_write is write ram is:\n");
copy_from_user((unsigned char *)ptmp,(unsigned char *)arg,sizeof(fpga_opt_t));

start =4093;
for( i=start; i<(start +16); i++){
if( i%8 ==0)
printk("\n");
printk("0x%04x ",*( (unsigned char *)( ( (fpga_opt_t *)ptmp)->prv +i)) );
}
break;
}

原因是数据量太大，超出栈大小。

解决方法：fpga_opt_t tmp;定义为全局变量