I am new to kernel driver development and I am trying update kernel version of a legacy project.
Example code is below
#include <linux/uaccess.h>
struct file *file_open(const char *path, int flags, int rights)
{
struct file *filptr = NULL;
int err = 0;
oldfs = get_fs();
set_fs(get_ds());
filptr = filp_open(path, flags, rights);
if (IS_ERR(filptr)) {
err = PTR_ERR(filptr);
return NULL;
}
return filptr;
}
void file_close(struct file *file)
{
int retval = filp_close(file, NULL);
printk("file_close retval: %d\n",retval);
set_fs(oldfs);
}
I am having below implicit declaration of get_fs() and set_fs() macros.
/driver.c: In function 'file_open':
/driver.c:593:27: error: implicit declaration of function 'get_fs'; did you mean 'get_bh'? [-Werror=implicit-function-declaration]
593 | oldfs = (mm_segment_t)get_fs();
| ^~~~~~
| get_bh
/driver.c:593:5: error: conversion to non-scalar type requested
593 | oldfs = (mm_segment_t)get_fs();
| ^~~~~
/driver.c:594:5: error: implicit declaration of function 'set_fs'; did you mean 'sget_fc'? [-Werror=implicit-function-declaration]
594 | set_fs(get_ds());
| ^~~~~~
| sget_fc
/driver.c:594:12: error: implicit declaration of function 'get_ds'; did you mean 'get_bh'? [-Werror=implicit-function-declaration]
594 | set_fs(get_ds());
| ^~~~~~
get_fs() and set_fs() macros have been removed from arm architecture <asm/uaccess.h> user access header file. But they are still defined in <asm-generic/uaccess.h> header. I couldn't find if it is proper to use generic user access apis in <asm-generic/uaccess.h> header file. If include both headers, I get redefinition warnings and errors.
./include/asm-generic/uaccess.h:129: warning: "access_ok" redefined
129 | #define access_ok(addr, size) __access_ok((unsigned long)(addr),(size))
|
In file included from ./include/linux/uaccess.h:11,
from ./include/linux/sched/task.h:11,
from ./include/linux/sched/signal.h:9,
from ./include/linux/rcuwait.h:6,
from ./include/linux/percpu-rwsem.h:7,
from ./include/linux/fs.h:33,
from ./include/linux/highmem.h:5,
from ./include/linux/bvec.h:10,
from ./include/linux/blk_types.h:10,
from ./include/linux/genhd.h:19,
from ./include/linux/blkdev.h:8,
from driver.c:6:
./arch/arm/include/asm/uaccess.h:251: note: this is the location of the previous definition
251 | #define access_ok(addr, size) (__range_ok(addr, size) == 0)
|
./include/asm-generic/uaccess.h:148: warning: "__put_user" redefined
148 | #define __put_user(x, ptr) \
|
./arch/arm/include/asm/uaccess.h:378: note: this is the location of the previous definition
378 | #define __put_user(x, ptr) put_user(x, ptr)
|
./include/asm-generic/uaccess.h:168: warning: "put_user" redefined
168 | #define put_user(x, ptr) \
|
./arch/arm/include/asm/uaccess.h:366: note: this is the location of the previous definition
366 | #define put_user(x, ptr) \
|
./include/asm-generic/uaccess.h:190: warning: "__get_user" redefined
190 | #define __get_user(x, ptr) \
|
./arch/arm/include/asm/uaccess.h:260: note: this is the location of the previous definition
260 | #define __get_user(x, ptr) get_user(x, ptr)
|
./include/asm-generic/uaccess.h:230: warning: "get_user" redefined
230 | #define get_user(x, ptr) \
|
./arch/arm/include/asm/uaccess.h:213: note: this is the location of the previous definition
213 | #define get_user(x, p) \
|
./include/asm-generic/uaccess.h:256:1: error: redefinition of '__clear_user'
256 | __clear_user(void __user *to, unsigned long n)
| ^~~~~~~~~~~~
./arch/arm/include/asm/uaccess.h:562:1: note: previous definition of '__clear_user' with type 'long unsigned int(void *, long unsigned int)'
562 | __clear_user(void __user *addr, unsigned long n)
| ^~~~~~~~~~~~
./include/asm-generic/uaccess.h:264:1: error: redefinition of 'clear_user'
264 | clear_user(void __user *to, unsigned long n)
| ^~~~~~~~~~
./arch/arm/include/asm/uaccess.h:588:42: note: previous definition of 'clear_user' with type 'long unsigned int(void *, long unsigned int)'
588 | static inline unsigned long __must_check clear_user(void __user *to, unsigned long n)
| ^~~~~~~~~~
So as I understood, for arm architecture only one header must be included. After kernel version 4.11 recommended way to include architecture specific headers is with <linux/uaccess.h> header. And this header includes <asm/uaccess.h>. So I infer <asm-generic/uaccess.h> should not included directly.
But other architectures still have get_fs() and set_fs() macros available in their headers.
As I understand these macros are setter/getter for thread address space defined in thread_info structure. But arm architecture's struct thread_info definition does not define this field.
I would like to ask if these macros usage is deprecated for arm arch. Is there any way to access thread adress space for arm architecture. Where should I look, any hint is appreciated.
