Linux kernel error return __linux

The definition and actions associated with err, such as error return, should include the header file:

#include <linux/err.h>

Common Err Description Include/asm-generic/errno-base.h

#define  eperm        1  /* operation not  permitted */   #define  enoent       2  / * no such file or directory */   #define  ESRCH         3  /* No such process */   #define   Eintr        4  /* interrupted system call  */   #define  eio      5  /* i/o error  */   #define  enxio        6  /* no  such device or address */   #define  E2BIG         7  /* Argument list too long */   #define  enoexec          8  /* exec format error */    #define  EBADF        9  /* Bad  file number */   #define  echild      10  /*  No child processes */   #define  EAGAIN       11  /* try again */   #define  ENOMEM       12  /* Out of memory */   #define  EACCES       13  /* Permission denied */   #define  EFAULT       14  /* Bad address */   #define &NBSP;ENOTBLK          15  /* block device required  */   #define EBUSY       16  /* Device or resource  busy */   #define  eexist      17  /* file  exists */   #define  exdev       18  /*  Cross-device link */   #define  enodev      19   /* No such device */   #define  ENOTDIR          20  /* Not a directory */   #define   eisdir      21  /* is a directory */   # define einval      22  /* invalid argument */    #define  ENFILE      23  /* File table  Overflow */ &nBsp #define  EMFILE      24  /* Too many open  files */   #define  enotty      25  /* not  a typewriter */   #define  ETXTBSY          26  /* Text file busy */   #define  EFBIG        27  /* File too large */   #define   Enospc      28  /* no space left on device  */   #define  ESPIPE      29  /* Illegal  seek */   #define  EROFS       30  /*  read-only file system */   #define  emlink      31   /* too many links */   #define  EPIPE       32   /* Broken pipe */   #define  EDOM         33  /* Math argument out of domain of func */    #define  erange      34  /* math result not  representable */
The kernel's error code is stored in the area of the last 4K of memory, the 0XFFFFF000~0XFFFFFFFF area. If the pointer points to this area of memory, an error is indicated. If you return a-EINTR error and the error code is -4 (0XFFFFFFFC), then 0XFFFFFFFC is the error code pointer.

Here are several macros related to the error:
Err_ptr () Converts the error code to a pointer.
Include/linux/err.h

static inline void * __must_check err_ptr (long error) {return (void *) error; }
Ptr_err () Converts the pointer to an error code.
Include/linux/err.h

Static inline long __must_check ptr_err (const void *ptr) {return (long) PTR; }

Is_err () Determines whether the pointer falls in the error code area.
Include/linux/err.h

Static inline long __must_check is_err (const void *ptr) {return Is_err_value ((unsigned long) PTR); } #define Max_errno 4095 #define IS_ERR_VALUE (x) unlikely ((x) >= (unsigned long)-max_errno)

Is_err_or_null () Determines whether the pointer falls in the error code area or is empty.
Include/linux/err.h

Static inline long __must_check is_err_or_null (const void *ptr) {return!ptr | |   Is_err_value ((unsigned long) PTR); }

Is_err () Determines whether the pointer points to the error code area, Ptr==null or!ptr determines whether the pointer is empty, and these judgements are generally used when the return value of the function being invoked is a pointer type. The difference between the use of Is_err () and ptr==null depends on what function is called, and if the function returns a null pointer if the call fails, then the Ptr==null or!ptr should be used. If the function returns a point pointing to the error code area when the call fails, use either Is_err () or Is_err_value (). Of course, you can also use Is_err_or_null to determine all calls that return as pointers.