get rid of legacy 'get_ds()' function

Every in-kernel use of this function defined it to KERNEL_DS (either as
an actual define, or as an inline function).  It's an entirely
historical artifact, and long long long ago used to actually read the
segment selector valueof '%ds' on x86.

Which in the kernel is always KERNEL_DS.

Inspired by a patch from Jann Horn that just did this for a very small
subset of users (the ones in fs/), along with Al who suggested a script.
I then just took it to the logical extreme and removed all the remaining
gunk.

Roughly scripted with

   git grep -l '(get_ds())' -- :^tools/ | xargs sed -i 's/(get_ds())/(KERNEL_DS)/'
   git grep -lw 'get_ds' -- :^tools/ | xargs sed -i '/^#define get_ds()/d'

plus manual fixups to remove a few unusual usage patterns, the couple of
inline function cases and to fix up a comment that had become stale.

The 'get_ds()' function remains in an x86 kvm selftest, since in user
space it actually does something relevant.

Inspired-by: Jann Horn <jannh@google.com>
Inspired-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/alpha/include/asm/uaccess.h

@@ -18,7 +18,6 @@
 #define USER_DS		((mm_segment_t) { -0x40000000000UL })
 
 #define get_fs()  (current_thread_info()->addr_limit)
-#define get_ds()  (KERNEL_DS)
 #define set_fs(x) (current_thread_info()->addr_limit = (x))
 
 #define segment_eq(a, b)	((a).seg == (b).seg)

arch/arm/include/asm/uaccess.h

@@ -59,7 +59,6 @@ extern int __put_user_bad(void);
  * Note that this is actually 0x1,0000,0000
  */
 #define KERNEL_DS	0x00000000
-#define get_ds()	(KERNEL_DS)
 
 #ifdef CONFIG_MMU
 

arch/arm/kernel/process.c

@@ -150,7 +150,7 @@ void __show_regs(struct pt_regs *regs)
 		if ((domain & domain_mask(DOMAIN_USER)) ==
 		    domain_val(DOMAIN_USER, DOMAIN_NOACCESS))
 			segment = "none";
-		else if (fs == get_ds())
+		else if (fs == KERNEL_DS)
 			segment = "kernel";
 		else
 			segment = "user";

arch/arm/xen/hypercall.S

@@ -113,8 +113,7 @@ ENTRY(privcmd_call)
 
 	/*
 	 * Disable userspace access from kernel. This is fine to do it
-	 * unconditionally as no set_fs(KERNEL_DS)/set_fs(get_ds()) is
+	 * unconditionally as no set_fs(KERNEL_DS) is called before.
-	 * called before.
 	 */
 	uaccess_disable r4
 

arch/arm64/include/asm/uaccess.h

@@ -34,7 +34,6 @@
 #include <asm/memory.h>
 #include <asm/extable.h>
 
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current_thread_info()->addr_limit)
 
 static inline void set_fs(mm_segment_t fs)

arch/csky/include/asm/segment.h

@@ -9,7 +9,6 @@ typedef struct {
 } mm_segment_t;
 
 #define KERNEL_DS		((mm_segment_t) { 0xFFFFFFFF })
-#define get_ds()		KERNEL_DS
 
 #define USER_DS			((mm_segment_t) { 0x80000000UL })
 #define get_fs()		(current_thread_info()->addr_limit)

arch/h8300/include/asm/segment.h

@@ -33,12 +33,6 @@ static inline mm_segment_t get_fs(void)
 	return USER_DS;
 }
 
-static inline mm_segment_t get_ds(void)
-{
-	/* return the supervisor data space code */
-	return KERNEL_DS;
-}
-
 #define segment_eq(a, b)	((a).seg == (b).seg)
 
 #endif /* __ASSEMBLY__ */

arch/ia64/include/asm/uaccess.h

@@ -48,7 +48,6 @@
 #define KERNEL_DS	((mm_segment_t) { ~0UL })		/* cf. access_ok() */
 #define USER_DS		((mm_segment_t) { TASK_SIZE-1 })	/* cf. access_ok() */
 
-#define get_ds()  (KERNEL_DS)
 #define get_fs()  (current_thread_info()->addr_limit)
 #define set_fs(x) (current_thread_info()->addr_limit = (x))
 

arch/m68k/include/asm/segment.h

@@ -45,16 +45,9 @@ static inline void set_fs(mm_segment_t val)
 			      : /* no outputs */ : "r" (val.seg) : "memory");
 }
 
-static inline mm_segment_t get_ds(void)
-{
-    /* return the supervisor data space code */
-    return KERNEL_DS;
-}
-
 #else
 #define USER_DS		MAKE_MM_SEG(TASK_SIZE)
 #define KERNEL_DS	MAKE_MM_SEG(0xFFFFFFFF)
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current_thread_info()->addr_limit)
 #define set_fs(x)	(current_thread_info()->addr_limit = (x))
 #endif

arch/microblaze/include/asm/uaccess.h

@@ -42,7 +42,6 @@
 #  define USER_DS	MAKE_MM_SEG(TASK_SIZE - 1)
 #  endif
 
-# define get_ds()	(KERNEL_DS)
 # define get_fs()	(current_thread_info()->addr_limit)
 # define set_fs(val)	(current_thread_info()->addr_limit = (val))
 

arch/mips/include/asm/uaccess.h

@@ -69,7 +69,6 @@ extern u64 __ua_limit;
 #define USER_DS		((mm_segment_t) { __UA_LIMIT })
 #endif
 
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current_thread_info()->addr_limit)
 #define set_fs(x)	(current_thread_info()->addr_limit = (x))
 

arch/mips/kernel/ftrace.c

@@ -86,7 +86,7 @@ static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
 		return -EFAULT;
 
 	old_fs = get_fs();
-	set_fs(get_ds());
+	set_fs(KERNEL_DS);
 	flush_icache_range(ip, ip + 8);
 	set_fs(old_fs);
 
@@ -111,7 +111,7 @@ static int ftrace_modify_code_2(unsigned long ip, unsigned int new_code1,
 
 	ip -= 4;
 	old_fs = get_fs();
-	set_fs(get_ds());
+	set_fs(KERNEL_DS);
 	flush_icache_range(ip, ip + 8);
 	set_fs(old_fs);
 
@@ -135,7 +135,7 @@ static int ftrace_modify_code_2r(unsigned long ip, unsigned int new_code1,
 		return -EFAULT;
 
 	old_fs = get_fs();
-	set_fs(get_ds());
+	set_fs(KERNEL_DS);
 	flush_icache_range(ip, ip + 8);
 	set_fs(old_fs);
 

arch/mips/kernel/kgdb.c

@@ -212,7 +212,7 @@ void kgdb_call_nmi_hook(void *ignored)
 	mm_segment_t old_fs;
 
 	old_fs = get_fs();
-	set_fs(get_ds());
+	set_fs(KERNEL_DS);
 
 	kgdb_nmicallback(raw_smp_processor_id(), NULL);
 
@@ -318,7 +318,7 @@ static int kgdb_mips_notify(struct notifier_block *self, unsigned long cmd,
 
 	/* Kernel mode. Set correct address limit */
 	old_fs = get_fs();
-	set_fs(get_ds());
+	set_fs(KERNEL_DS);
 
 	if (atomic_read(&kgdb_active) != -1)
 		kgdb_nmicallback(smp_processor_id(), regs);

arch/mips/kernel/traps.c

@@ -1077,7 +1077,7 @@ asmlinkage void do_tr(struct pt_regs *regs)
 
 	seg = get_fs();
 	if (!user_mode(regs))
-		set_fs(get_ds());
+		set_fs(KERNEL_DS);
 
 	prev_state = exception_enter();
 	current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;

arch/nds32/include/asm/uaccess.h

@@ -37,7 +37,6 @@ extern int fixup_exception(struct pt_regs *regs);
 #define KERNEL_DS 	((mm_segment_t) { ~0UL })
 #define USER_DS		((mm_segment_t) {TASK_SIZE - 1})
 
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current_thread_info()->addr_limit)
 #define user_addr_max	get_fs
 

arch/nds32/kernel/process.c

@@ -121,7 +121,7 @@ void show_regs(struct pt_regs *regs)
 		regs->uregs[3], regs->uregs[2], regs->uregs[1], regs->uregs[0]);
 	pr_info("  IRQs o%s  Segment %s\n",
 		interrupts_enabled(regs) ? "n" : "ff",
-		segment_eq(get_fs(), get_ds())? "kernel" : "user");
+		segment_eq(get_fs(), KERNEL_DS)? "kernel" : "user");
 }
 
 EXPORT_SYMBOL(show_regs);

arch/nios2/include/asm/uaccess.h

@@ -26,7 +26,6 @@
 #define USER_DS			MAKE_MM_SEG(0x80000000UL)
 #define KERNEL_DS		MAKE_MM_SEG(0)
 
-#define get_ds()		(KERNEL_DS)
 
 #define get_fs()		(current_thread_info()->addr_limit)
 #define set_fs(seg)		(current_thread_info()->addr_limit = (seg))

arch/openrisc/include/asm/uaccess.h

@@ -42,7 +42,6 @@
  */
 
 #define KERNEL_DS	(~0UL)
-#define get_ds()	(KERNEL_DS)
 
 #define USER_DS		(TASK_SIZE)
 #define get_fs()	(current_thread_info()->addr_limit)

arch/parisc/include/asm/uaccess.h

@@ -16,7 +16,6 @@
 
 #define segment_eq(a, b) ((a).seg == (b).seg)
 
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current_thread_info()->addr_limit)
 #define set_fs(x)	(current_thread_info()->addr_limit = (x))
 

arch/powerpc/include/asm/uaccess.h

@@ -28,7 +28,6 @@
 #define USER_DS		MAKE_MM_SEG(TASK_SIZE - 1)
 #endif
 
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current->thread.addr_limit)
 
 static inline void set_fs(mm_segment_t fs)

arch/riscv/include/asm/uaccess.h

@@ -41,7 +41,6 @@
 #define KERNEL_DS	(~0UL)
 #define USER_DS		(TASK_SIZE)
 
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current_thread_info()->addr_limit)
 
 static inline void set_fs(mm_segment_t fs)

arch/s390/include/asm/uaccess.h

@@ -31,7 +31,6 @@
 #define USER_DS		(2)
 #define USER_DS_SACF	(3)
 
-#define get_ds()        (KERNEL_DS)
 #define get_fs()        (current->thread.mm_segment)
 #define segment_eq(a,b) (((a) & 2) == ((b) & 2))
 

arch/sh/include/asm/segment.h

@@ -26,7 +26,6 @@ typedef struct {
 
 #define segment_eq(a, b) ((a).seg == (b).seg)
 
-#define get_ds()	(KERNEL_DS)
 
 #define get_fs()	(current_thread_info()->addr_limit)
 #define set_fs(x)	(current_thread_info()->addr_limit = (x))

arch/sparc/include/asm/uaccess_32.h

@@ -25,7 +25,6 @@
 #define KERNEL_DS   ((mm_segment_t) { 0 })
 #define USER_DS     ((mm_segment_t) { -1 })
 
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current->thread.current_ds)
 #define set_fs(val)	((current->thread.current_ds) = (val))
 

arch/sparc/include/asm/uaccess_64.h

@@ -31,7 +31,6 @@
 #define USER_DS     ((mm_segment_t) { ASI_AIUS })	/* har har har */
 
 #define get_fs() ((mm_segment_t){(current_thread_info()->current_ds)})
-#define get_ds() (KERNEL_DS)
 
 #define segment_eq(a, b)  ((a).seg == (b).seg)
 

arch/x86/include/asm/uaccess.h

@@ -25,7 +25,6 @@
 #define KERNEL_DS	MAKE_MM_SEG(-1UL)
 #define USER_DS 	MAKE_MM_SEG(TASK_SIZE_MAX)
 
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current->thread.addr_limit)
 static inline void set_fs(mm_segment_t fs)
 {

arch/xtensa/include/asm/asm-uaccess.h

@@ -32,8 +32,6 @@
 #define KERNEL_DS	0
 #define USER_DS		1
 
-#define get_ds		(KERNEL_DS)
-
 /*
  * get_fs reads current->thread.current_ds into a register.
  * On Entry:

arch/xtensa/include/asm/uaccess.h

@@ -32,7 +32,6 @@
 #define KERNEL_DS	((mm_segment_t) { 0 })
 #define USER_DS		((mm_segment_t) { 1 })
 
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current->thread.current_ds)
 #define set_fs(val)	(current->thread.current_ds = (val))
 

drivers/staging/rtl8723bs/os_dep/osdep_service.c

@@ -137,7 +137,7 @@ static int isFileReadable(char *path)
 		ret = PTR_ERR(fp);
 	}
 	else {
-		oldfs = get_fs(); set_fs(get_ds());
+		oldfs = get_fs(); set_fs(KERNEL_DS);
 
 		if (1!=readFile(fp, &buf, 1))
 			ret = -EINVAL;
@@ -165,7 +165,7 @@ static int retriveFromFile(char *path, u8 *buf, u32 sz)
 		if (0 == (ret =openFile(&fp, path, O_RDONLY, 0))) {
 			DBG_871X("%s openFile path:%s fp =%p\n", __func__, path , fp);
 
-			oldfs = get_fs(); set_fs(get_ds());
+			oldfs = get_fs(); set_fs(KERNEL_DS);
 			ret =readFile(fp, buf, sz);
 			set_fs(oldfs);
 			closeFile(fp);

fs/read_write.c

@@ -426,7 +426,7 @@ ssize_t kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
 	ssize_t result;
 
 	old_fs = get_fs();
-	set_fs(get_ds());
+	set_fs(KERNEL_DS);
 	/* The cast to a user pointer is valid due to the set_fs() */
 	result = vfs_read(file, (void __user *)buf, count, pos);
 	set_fs(old_fs);
@@ -499,7 +499,7 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
 		return -EINVAL;
 
 	old_fs = get_fs();
-	set_fs(get_ds());
+	set_fs(KERNEL_DS);
 	p = (__force const char __user *)buf;
 	if (count > MAX_RW_COUNT)
 		count =  MAX_RW_COUNT;
@@ -521,7 +521,7 @@ ssize_t kernel_write(struct file *file, const void *buf, size_t count,
 	ssize_t res;
 
 	old_fs = get_fs();
-	set_fs(get_ds());
+	set_fs(KERNEL_DS);
 	/* The cast to a user pointer is valid due to the set_fs() */
 	res = vfs_write(file, (__force const char __user *)buf, count, pos);
 	set_fs(old_fs);

fs/splice.c

@@ -357,7 +357,7 @@ static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
 	ssize_t res;
 
 	old_fs = get_fs();
-	set_fs(get_ds());
+	set_fs(KERNEL_DS);
 	/* The cast to a user pointer is valid due to the set_fs() */
 	res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos, 0);
 	set_fs(old_fs);

include/asm-generic/uaccess.h

@@ -22,7 +22,6 @@
 #endif
 
 #ifndef get_fs
-#define get_ds()	(KERNEL_DS)
 #define get_fs()	(current_thread_info()->addr_limit)
 
 static inline void set_fs(mm_segment_t fs)

security/integrity/iint.c

@@ -200,7 +200,7 @@ int integrity_kernel_read(struct file *file, loff_t offset,
 		return -EBADF;
 
 	old_fs = get_fs();
-	set_fs(get_ds());
+	set_fs(KERNEL_DS);
 	ret = __vfs_read(file, buf, count, &offset);
 	set_fs(old_fs);