m68k: Remove set_fs()

Add a m68k-only set_fc helper to set the SFC and DFC registers for the
few places that need to override it for special MM operations, but
disconnect that from the deprecated kernel-wide set_fs() API.

Note that the SFC/DFC registers are context switched, so there is no need
to disable preemption.

Partially based on an earlier patch from
Linus Torvalds <torvalds@linux-foundation.org>.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Link: https://lore.kernel.org/r/20210916070405.52750-7-hch@lst.de
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

5 files changed, 31 insertions, 77 deletions

diff --git a/arch/m68k/include/asm/processor.h b/arch/m68k/include/asm/processor.h
index 3750819ac5a1..f4d82c619a5c 100644
--- a/arch/m68k/include/asm/processor.h
+++ b/arch/m68k/include/asm/processor.h
@@ -9,7 +9,6 @@
 #define __ASM_M68K_PROCESSOR_H
 
 #include <linux/thread_info.h>
-#include <asm/segment.h>
 #include <asm/fpu.h>
 #include <asm/ptrace.h>
 
@@ -75,11 +74,37 @@ static inline void wrusp(unsigned long usp)
 #define TASK_UNMAPPED_BASE	0
 #endif
 
+/* Address spaces (or Function Codes in Motorola lingo) */
+#define USER_DATA     1
+#define USER_PROGRAM  2
+#define SUPER_DATA    5
+#define SUPER_PROGRAM 6
+#define CPU_SPACE     7
+
+#ifdef CONFIG_CPU_HAS_ADDRESS_SPACES
+/*
+ * Set the SFC/DFC registers for special MM operations.  For most normal
+ * operation these remain set to USER_DATA for the uaccess routines.
+ */
+static inline void set_fc(unsigned long val)
+{
+	WARN_ON_ONCE(in_interrupt());
+
+	__asm__ __volatile__ ("movec %0,%/sfc\n\t"
+			      "movec %0,%/dfc\n\t"
+			      : /* no outputs */ : "r" (val) : "memory");
+}
+#else
+static inline void set_fc(unsigned long val)
+{
+}
+#endif /* CONFIG_CPU_HAS_ADDRESS_SPACES */
+
 struct thread_struct {
 	unsigned long  ksp;		/* kernel stack pointer */
 	unsigned long  usp;		/* user stack pointer */
 	unsigned short sr;		/* saved status register */
-	unsigned short fs;		/* saved fs (sfc, dfc) */
+	unsigned short fc;		/* saved fc (sfc, dfc) */
 	unsigned long  crp[2];		/* cpu root pointer */
 	unsigned long  esp0;		/* points to SR of stack frame */
 	unsigned long  faddr;		/* info about last fault */
@@ -92,7 +117,7 @@ struct thread_struct {
 #define INIT_THREAD  {							\
 	.ksp	= sizeof(init_stack) + (unsigned long) init_stack,	\
 	.sr	= PS_S,							\
-	.fs	= __KERNEL_DS,						\
+	.fc	= USER_DATA,						\
 }
 
 /*
diff --git a/arch/m68k/include/asm/segment.h b/arch/m68k/include/asm/segment.h
deleted file mode 100644
index 2b5e68a71ef7..000000000000
--- a/arch/m68k/include/asm/segment.h
+++ /dev/null
@@ -1,59 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _M68K_SEGMENT_H
-#define _M68K_SEGMENT_H
-
-/* define constants */
-/* Address spaces (FC0-FC2) */
-#define USER_DATA     (1)
-#ifndef __USER_DS
-#define __USER_DS     (USER_DATA)
-#endif
-#define USER_PROGRAM  (2)
-#define SUPER_DATA    (5)
-#ifndef __KERNEL_DS
-#define __KERNEL_DS   (SUPER_DATA)
-#endif
-#define SUPER_PROGRAM (6)
-#define CPU_SPACE     (7)
-
-#ifndef __ASSEMBLY__
-
-typedef struct {
-	unsigned long seg;
-} mm_segment_t;
-
-#define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
-
-#ifdef CONFIG_CPU_HAS_ADDRESS_SPACES
-/*
- * Get/set the SFC/DFC registers for MOVES instructions
- */
-#define USER_DS		MAKE_MM_SEG(__USER_DS)
-#define KERNEL_DS	MAKE_MM_SEG(__KERNEL_DS)
-
-static inline mm_segment_t get_fs(void)
-{
-	mm_segment_t _v;
-	__asm__ ("movec %/dfc,%0":"=r" (_v.seg):);
-	return _v;
-}
-
-static inline void set_fs(mm_segment_t val)
-{
-	__asm__ __volatile__ ("movec %0,%/sfc\n\t"
-			      "movec %0,%/dfc\n\t"
-			      : /* no outputs */ : "r" (val.seg) : "memory");
-}
-
-#else
-#define USER_DS		MAKE_MM_SEG(TASK_SIZE)
-#define KERNEL_DS	MAKE_MM_SEG(0xFFFFFFFF)
-#define get_fs()	(current_thread_info()->addr_limit)
-#define set_fs(x)	(current_thread_info()->addr_limit = (x))
-#endif
-
-#define uaccess_kernel()	(get_fs().seg == KERNEL_DS.seg)
-
-#endif /* __ASSEMBLY__ */
-
-#endif /* _M68K_SEGMENT_H */
diff --git a/arch/m68k/include/asm/thread_info.h b/arch/m68k/include/asm/thread_info.h
index 15a757073fa5..c952658ba792 100644
--- a/arch/m68k/include/asm/thread_info.h
+++ b/arch/m68k/include/asm/thread_info.h
@@ -4,7 +4,6 @@
 
 #include <asm/types.h>
 #include <asm/page.h>
-#include <asm/segment.h>
 
 /*
  * On machines with 4k pages we default to an 8k thread size, though we
@@ -27,7 +26,6 @@
 struct thread_info {
 	struct task_struct	*task;		/* main task structure */
 	unsigned long		flags;
-	mm_segment_t		addr_limit;	/* thread address space */
 	int			preempt_count;	/* 0 => preemptable, <0 => BUG */
 	__u32			cpu;		/* should always be 0 on m68k */
 	unsigned long		tp_value;	/* thread pointer */
@@ -37,7 +35,6 @@ struct thread_info {
 #define INIT_THREAD_INFO(tsk)			\
 {						\
 	.task		= &tsk,			\
-	.addr_limit	= KERNEL_DS,		\
 	.preempt_count	= INIT_PREEMPT_COUNT,	\
 }
 
diff --git a/arch/m68k/include/asm/tlbflush.h b/arch/m68k/include/asm/tlbflush.h
index a6318ccd308f..b882e2f4f551 100644
--- a/arch/m68k/include/asm/tlbflush.h
+++ b/arch/m68k/include/asm/tlbflush.h
@@ -13,13 +13,12 @@ static inline void flush_tlb_kernel_page(void *addr)
 	if (CPU_IS_COLDFIRE) {
 		mmu_write(MMUOR, MMUOR_CNL);
 	} else if (CPU_IS_040_OR_060) {
-		mm_segment_t old_fs = get_fs();
-		set_fs(KERNEL_DS);
+		set_fc(SUPER_DATA);
 		__asm__ __volatile__(".chip 68040\n\t"
 				     "pflush (%0)\n\t"
 				     ".chip 68k"
 				     : : "a" (addr));
-		set_fs(old_fs);
+		set_fc(USER_DATA);
 	} else if (CPU_IS_020_OR_030)
 		__asm__ __volatile__("pflush #4,#4,(%0)" : : "a" (addr));
 }
@@ -84,12 +83,8 @@ static inline void flush_tlb_mm(struct mm_struct *mm)
 
 static inline void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
 {
-	if (vma->vm_mm == current->active_mm) {
-		mm_segment_t old_fs = force_uaccess_begin();
-
+	if (vma->vm_mm == current->active_mm)
 		__flush_tlb_one(addr);
-		force_uaccess_end(old_fs);
-	}
 }
 
 static inline void flush_tlb_range(struct vm_area_struct *vma,
diff --git a/arch/m68k/include/asm/uaccess.h b/arch/m68k/include/asm/uaccess.h
index 65581a7874d4..ba670523885c 100644
--- a/arch/m68k/include/asm/uaccess.h
+++ b/arch/m68k/include/asm/uaccess.h
@@ -9,7 +9,6 @@
  */
 #include <linux/compiler.h>
 #include <linux/types.h>
-#include <asm/segment.h>
 #include <asm/extable.h>
 
 /* We let the MMU do all checking */
@@ -451,9 +450,6 @@ do {									\
 		goto err_label;						\
 } while (0)
 
-#define user_addr_max() \
-	(uaccess_kernel() ? ~0UL : TASK_SIZE)
-
 extern long strncpy_from_user(char *dst, const char __user *src, long count);
 extern __must_check long strnlen_user(const char __user *str, long n);