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>

4 files changed, 6 insertions, 7 deletions

diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
index d43c1dc6ef15..62b298c50905 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/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))
 
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 2ea0ec95efe9..4b5e1f2bfbce 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/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);
 
diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c
index 149100e1bc7c..6e574c02e4c3 100644
--- a/arch/mips/kernel/kgdb.c
+++ b/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);
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index c91097f7b32f..cbab46004e99 100644
--- a/arch/mips/kernel/traps.c
+++ b/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;