MIPS: Unify memcpy.S and memcpy-inatomic.S

We can save the 451 lines of code that comprise memcpy-inatomic.S at the
expense of a single instruction in the memcpy prolog.  We also use an
additional register (t6), so this may cause increased register pressure in
some places as well.  But I think the reduced maintenance burden, of not
having two nearly identical implementations, makes it worth it.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/uaccess.h

@@ -687,7 +687,7 @@ extern size_t __copy_user(void *__to, const void *__from, size_t __n);
 	__MODULE_JAL(__copy_user)					\
 	: "+r" (__cu_to_r), "+r" (__cu_from_r), "+r" (__cu_len_r)	\
 	:								\
-	: "$8", "$9", "$10", "$11", "$12", "$15", "$24", "$31",		\
+	: "$8", "$9", "$10", "$11", "$12", "$14", "$15", "$24", "$31",	\
 	  DADDI_SCRATCH, "memory");					\
 	__cu_len_r;							\
 })
@@ -797,7 +797,7 @@ extern size_t __copy_user_inatomic(void *__to, const void *__from, size_t __n);
 	".set\treorder"							\
 	: "+r" (__cu_to_r), "+r" (__cu_from_r), "+r" (__cu_len_r)	\
 	:								\
-	: "$8", "$9", "$10", "$11", "$12", "$15", "$24", "$31",		\
+	: "$8", "$9", "$10", "$11", "$12", "$14", "$15", "$24", "$31",	\
 	  DADDI_SCRATCH, "memory");					\
 	__cu_len_r;							\
 })
@@ -820,7 +820,7 @@ extern size_t __copy_user_inatomic(void *__to, const void *__from, size_t __n);
 	".set\treorder"							\
 	: "+r" (__cu_to_r), "+r" (__cu_from_r), "+r" (__cu_len_r)	\
 	:								\
-	: "$8", "$9", "$10", "$11", "$12", "$15", "$24", "$31",		\
+	: "$8", "$9", "$10", "$11", "$12", "$14", "$15", "$24", "$31",	\
 	  DADDI_SCRATCH, "memory");					\
 	__cu_len_r;							\
 })

arch/mips/lib/Makefile

@@ -2,7 +2,7 @@
 # Makefile for MIPS-specific library files..
 #
 
-lib-y	+= csum_partial.o delay.o memcpy.o memcpy-inatomic.o memset.o \
+lib-y	+= csum_partial.o delay.o memcpy.o memset.o \
 	   strlen_user.o strncpy_user.o strnlen_user.o uncached.o
 
 obj-y			+= iomap.o

arch/mips/lib/memcpy-inatomic.S

@@ -1,451 +0,0 @@
-/*
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Unified implementation of memcpy, memmove and the __copy_user backend.
- *
- * Copyright (C) 1998, 99, 2000, 01, 2002 Ralf Baechle (ralf@gnu.org)
- * Copyright (C) 1999, 2000, 01, 2002 Silicon Graphics, Inc.
- * Copyright (C) 2002 Broadcom, Inc.
- *   memcpy/copy_user author: Mark Vandevoorde
- * Copyright (C) 2007  Maciej W. Rozycki
- *
- * Mnemonic names for arguments to memcpy/__copy_user
- */
-
-/*
- * Hack to resolve longstanding prefetch issue
- *
- * Prefetching may be fatal on some systems if we're prefetching beyond the
- * end of memory on some systems.  It's also a seriously bad idea on non
- * dma-coherent systems.
- */
-#ifdef CONFIG_DMA_NONCOHERENT
-#undef CONFIG_CPU_HAS_PREFETCH
-#endif
-#ifdef CONFIG_MIPS_MALTA
-#undef CONFIG_CPU_HAS_PREFETCH
-#endif
-
-#include <asm/asm.h>
-#include <asm/asm-offsets.h>
-#include <asm/regdef.h>
-
-#define dst a0
-#define src a1
-#define len a2
-
-/*
- * Spec
- *
- * memcpy copies len bytes from src to dst and sets v0 to dst.
- * It assumes that
- *   - src and dst don't overlap
- *   - src is readable
- *   - dst is writable
- * memcpy uses the standard calling convention
- *
- * __copy_user copies up to len bytes from src to dst and sets a2 (len) to
- * the number of uncopied bytes due to an exception caused by a read or write.
- * __copy_user assumes that src and dst don't overlap, and that the call is
- * implementing one of the following:
- *   copy_to_user
- *     - src is readable  (no exceptions when reading src)
- *   copy_from_user
- *     - dst is writable  (no exceptions when writing dst)
- * __copy_user uses a non-standard calling convention; see
- * include/asm-mips/uaccess.h
- *
- * When an exception happens on a load, the handler must
- # ensure that all of the destination buffer is overwritten to prevent
- * leaking information to user mode programs.
- */
-
-/*
- * Implementation
- */
-
-/*
- * The exception handler for loads requires that:
- *  1- AT contain the address of the byte just past the end of the source
- *     of the copy,
- *  2- src_entry <= src < AT, and
- *  3- (dst - src) == (dst_entry - src_entry),
- * The _entry suffix denotes values when __copy_user was called.
- *
- * (1) is set up up by uaccess.h and maintained by not writing AT in copy_user
- * (2) is met by incrementing src by the number of bytes copied
- * (3) is met by not doing loads between a pair of increments of dst and src
- *
- * The exception handlers for stores adjust len (if necessary) and return.
- * These handlers do not need to overwrite any data.
- *
- * For __rmemcpy and memmove an exception is always a kernel bug, therefore
- * they're not protected.
- */
-
-#define EXC(inst_reg,addr,handler)		\
-9:	inst_reg, addr;				\
-	.section __ex_table,"a";		\
-	PTR	9b, handler;			\
-	.previous
-
-/*
- * Only on the 64-bit kernel we can made use of 64-bit registers.
- */
-#ifdef CONFIG_64BIT
-#define USE_DOUBLE
-#endif
-
-#ifdef USE_DOUBLE
-
-#define LOAD   ld
-#define LOADL  ldl
-#define LOADR  ldr
-#define STOREL sdl
-#define STORER sdr
-#define STORE  sd
-#define ADD    daddu
-#define SUB    dsubu
-#define SRL    dsrl
-#define SRA    dsra
-#define SLL    dsll
-#define SLLV   dsllv
-#define SRLV   dsrlv
-#define NBYTES 8
-#define LOG_NBYTES 3
-
-/*
- * As we are sharing code base with the mips32 tree (which use the o32 ABI
- * register definitions). We need to redefine the register definitions from
- * the n64 ABI register naming to the o32 ABI register naming.
- */
-#undef t0
-#undef t1
-#undef t2
-#undef t3
-#define t0	$8
-#define t1	$9
-#define t2	$10
-#define t3	$11
-#define t4	$12
-#define t5	$13
-#define t6	$14
-#define t7	$15
-
-#else
-
-#define LOAD   lw
-#define LOADL  lwl
-#define LOADR  lwr
-#define STOREL swl
-#define STORER swr
-#define STORE  sw
-#define ADD    addu
-#define SUB    subu
-#define SRL    srl
-#define SLL    sll
-#define SRA    sra
-#define SLLV   sllv
-#define SRLV   srlv
-#define NBYTES 4
-#define LOG_NBYTES 2
-
-#endif /* USE_DOUBLE */
-
-#ifdef CONFIG_CPU_LITTLE_ENDIAN
-#define LDFIRST LOADR
-#define LDREST  LOADL
-#define STFIRST STORER
-#define STREST  STOREL
-#define SHIFT_DISCARD SLLV
-#else
-#define LDFIRST LOADL
-#define LDREST  LOADR
-#define STFIRST STOREL
-#define STREST  STORER
-#define SHIFT_DISCARD SRLV
-#endif
-
-#define FIRST(unit) ((unit)*NBYTES)
-#define REST(unit)  (FIRST(unit)+NBYTES-1)
-#define UNIT(unit)  FIRST(unit)
-
-#define ADDRMASK (NBYTES-1)
-
-	.text
-	.set	noreorder
-#ifndef CONFIG_CPU_DADDI_WORKAROUNDS
-	.set	noat
-#else
-	.set	at=v1
-#endif
-
-/*
- * A combined memcpy/__copy_user
- * __copy_user sets len to 0 for success; else to an upper bound of
- * the number of uncopied bytes.
- * memcpy sets v0 to dst.
- */
-	.align	5
-LEAF(__copy_user_inatomic)
-	/*
-	 * Note: dst & src may be unaligned, len may be 0
-	 * Temps
-	 */
-#define rem t8
-
-	/*
-	 * The "issue break"s below are very approximate.
-	 * Issue delays for dcache fills will perturb the schedule, as will
-	 * load queue full replay traps, etc.
-	 *
-	 * If len < NBYTES use byte operations.
-	 */
-	PREF(	0, 0(src) )
-	PREF(	1, 0(dst) )
-	sltu	t2, len, NBYTES
-	and	t1, dst, ADDRMASK
-	PREF(	0, 1*32(src) )
-	PREF(	1, 1*32(dst) )
-	bnez	t2, .Lcopy_bytes_checklen
-	 and	t0, src, ADDRMASK
-	PREF(	0, 2*32(src) )
-	PREF(	1, 2*32(dst) )
-	bnez	t1, .Ldst_unaligned
-	 nop
-	bnez	t0, .Lsrc_unaligned_dst_aligned
-	/*
-	 * use delay slot for fall-through
-	 * src and dst are aligned; need to compute rem
-	 */
-.Lboth_aligned:
-	 SRL	t0, len, LOG_NBYTES+3    	# +3 for 8 units/iter
-	beqz	t0, .Lcleanup_both_aligned	# len < 8*NBYTES
-	 and	rem, len, (8*NBYTES-1)	 	# rem = len % (8*NBYTES)
-	PREF(	0, 3*32(src) )
-	PREF(	1, 3*32(dst) )
-	.align	4
-1:
-EXC(	LOAD	t0, UNIT(0)(src),	.Ll_exc)
-EXC(	LOAD	t1, UNIT(1)(src),	.Ll_exc_copy)
-EXC(	LOAD	t2, UNIT(2)(src),	.Ll_exc_copy)
-EXC(	LOAD	t3, UNIT(3)(src),	.Ll_exc_copy)
-	SUB	len, len, 8*NBYTES
-EXC(	LOAD	t4, UNIT(4)(src),	.Ll_exc_copy)
-EXC(	LOAD	t7, UNIT(5)(src),	.Ll_exc_copy)
-	STORE	t0, UNIT(0)(dst)
-	STORE	t1, UNIT(1)(dst)
-EXC(	LOAD	t0, UNIT(6)(src),	.Ll_exc_copy)
-EXC(	LOAD	t1, UNIT(7)(src),	.Ll_exc_copy)
-	ADD	src, src, 8*NBYTES
-	ADD	dst, dst, 8*NBYTES
-	STORE	t2, UNIT(-6)(dst)
-	STORE	t3, UNIT(-5)(dst)
-	STORE	t4, UNIT(-4)(dst)
-	STORE	t7, UNIT(-3)(dst)
-	STORE	t0, UNIT(-2)(dst)
-	STORE	t1, UNIT(-1)(dst)
-	PREF(	0, 8*32(src) )
-	PREF(	1, 8*32(dst) )
-	bne	len, rem, 1b
-	 nop
-
-	/*
-	 * len == rem == the number of bytes left to copy < 8*NBYTES
-	 */
-.Lcleanup_both_aligned:
-	beqz	len, .Ldone
-	 sltu	t0, len, 4*NBYTES
-	bnez	t0, .Lless_than_4units
-	 and	rem, len, (NBYTES-1)	# rem = len % NBYTES
-	/*
-	 * len >= 4*NBYTES
-	 */
-EXC(	LOAD	t0, UNIT(0)(src),	.Ll_exc)
-EXC(	LOAD	t1, UNIT(1)(src),	.Ll_exc_copy)
-EXC(	LOAD	t2, UNIT(2)(src),	.Ll_exc_copy)
-EXC(	LOAD	t3, UNIT(3)(src),	.Ll_exc_copy)
-	SUB	len, len, 4*NBYTES
-	ADD	src, src, 4*NBYTES
-	STORE	t0, UNIT(0)(dst)
-	STORE	t1, UNIT(1)(dst)
-	STORE	t2, UNIT(2)(dst)
-	STORE	t3, UNIT(3)(dst)
-	.set	reorder				/* DADDI_WAR */
-	ADD	dst, dst, 4*NBYTES
-	beqz	len, .Ldone
-	.set	noreorder
-.Lless_than_4units:
-	/*
-	 * rem = len % NBYTES
-	 */
-	beq	rem, len, .Lcopy_bytes
-	 nop
-1:
-EXC(	LOAD	t0, 0(src),		.Ll_exc)
-	ADD	src, src, NBYTES
-	SUB	len, len, NBYTES
-	STORE	t0, 0(dst)
-	.set	reorder				/* DADDI_WAR */
-	ADD	dst, dst, NBYTES
-	bne	rem, len, 1b
-	.set	noreorder
-
-	/*
-	 * src and dst are aligned, need to copy rem bytes (rem < NBYTES)
-	 * A loop would do only a byte at a time with possible branch
-	 * mispredicts.  Can't do an explicit LOAD dst,mask,or,STORE
-	 * because can't assume read-access to dst.  Instead, use
-	 * STREST dst, which doesn't require read access to dst.
-	 *
-	 * This code should perform better than a simple loop on modern,
-	 * wide-issue mips processors because the code has fewer branches and
-	 * more instruction-level parallelism.
-	 */
-#define bits t2
-	beqz	len, .Ldone
-	 ADD	t1, dst, len	# t1 is just past last byte of dst
-	li	bits, 8*NBYTES
-	SLL	rem, len, 3	# rem = number of bits to keep
-EXC(	LOAD	t0, 0(src),		.Ll_exc)
-	SUB	bits, bits, rem	# bits = number of bits to discard
-	SHIFT_DISCARD t0, t0, bits
-	STREST	t0, -1(t1)
-	jr	ra
-	 move	len, zero
-.Ldst_unaligned:
-	/*
-	 * dst is unaligned
-	 * t0 = src & ADDRMASK
-	 * t1 = dst & ADDRMASK; T1 > 0
-	 * len >= NBYTES
-	 *
-	 * Copy enough bytes to align dst
-	 * Set match = (src and dst have same alignment)
-	 */
-#define match rem
-EXC(	LDFIRST	t3, FIRST(0)(src),	.Ll_exc)
-	ADD	t2, zero, NBYTES
-EXC(	LDREST	t3, REST(0)(src),	.Ll_exc_copy)
-	SUB	t2, t2, t1	# t2 = number of bytes copied
-	xor	match, t0, t1
-	STFIRST t3, FIRST(0)(dst)
-	beq	len, t2, .Ldone
-	 SUB	len, len, t2
-	ADD	dst, dst, t2
-	beqz	match, .Lboth_aligned
-	 ADD	src, src, t2
-
-.Lsrc_unaligned_dst_aligned:
-	SRL	t0, len, LOG_NBYTES+2    # +2 for 4 units/iter
-	PREF(	0, 3*32(src) )
-	beqz	t0, .Lcleanup_src_unaligned
-	 and	rem, len, (4*NBYTES-1)   # rem = len % 4*NBYTES
-	PREF(	1, 3*32(dst) )
-1:
-/*
- * Avoid consecutive LD*'s to the same register since some mips
- * implementations can't issue them in the same cycle.
- * It's OK to load FIRST(N+1) before REST(N) because the two addresses
- * are to the same unit (unless src is aligned, but it's not).
- */
-EXC(	LDFIRST	t0, FIRST(0)(src),	.Ll_exc)
-EXC(	LDFIRST	t1, FIRST(1)(src),	.Ll_exc_copy)
-	SUB     len, len, 4*NBYTES
-EXC(	LDREST	t0, REST(0)(src),	.Ll_exc_copy)
-EXC(	LDREST	t1, REST(1)(src),	.Ll_exc_copy)
-EXC(	LDFIRST	t2, FIRST(2)(src),	.Ll_exc_copy)
-EXC(	LDFIRST	t3, FIRST(3)(src),	.Ll_exc_copy)
-EXC(	LDREST	t2, REST(2)(src),	.Ll_exc_copy)
-EXC(	LDREST	t3, REST(3)(src),	.Ll_exc_copy)
-	PREF(	0, 9*32(src) )		# 0 is PREF_LOAD  (not streamed)
-	ADD	src, src, 4*NBYTES
-#ifdef CONFIG_CPU_SB1
-	nop				# improves slotting
-#endif
-	STORE	t0, UNIT(0)(dst)
-	STORE	t1, UNIT(1)(dst)
-	STORE	t2, UNIT(2)(dst)
-	STORE	t3, UNIT(3)(dst)
-	PREF(	1, 9*32(dst) )     	# 1 is PREF_STORE (not streamed)
-	.set	reorder				/* DADDI_WAR */
-	ADD	dst, dst, 4*NBYTES
-	bne	len, rem, 1b
-	.set	noreorder
-
-.Lcleanup_src_unaligned:
-	beqz	len, .Ldone
-	 and	rem, len, NBYTES-1  # rem = len % NBYTES
-	beq	rem, len, .Lcopy_bytes
-	 nop
-1:
-EXC(	LDFIRST t0, FIRST(0)(src),	.Ll_exc)
-EXC(	LDREST	t0, REST(0)(src),	.Ll_exc_copy)
-	ADD	src, src, NBYTES
-	SUB	len, len, NBYTES
-	STORE	t0, 0(dst)
-	.set	reorder				/* DADDI_WAR */
-	ADD	dst, dst, NBYTES
-	bne	len, rem, 1b
-	.set	noreorder
-
-.Lcopy_bytes_checklen:
-	beqz	len, .Ldone
-	 nop
-.Lcopy_bytes:
-	/* 0 < len < NBYTES  */
-#define COPY_BYTE(N)			\
-EXC(	lb	t0, N(src), .Ll_exc);	\
-	SUB	len, len, 1;		\
-	beqz	len, .Ldone;		\
-	 sb	t0, N(dst)
-
-	COPY_BYTE(0)
-	COPY_BYTE(1)
-#ifdef USE_DOUBLE
-	COPY_BYTE(2)
-	COPY_BYTE(3)
-	COPY_BYTE(4)
-	COPY_BYTE(5)
-#endif
-EXC(	lb	t0, NBYTES-2(src), .Ll_exc)
-	SUB	len, len, 1
-	jr	ra
-	 sb	t0, NBYTES-2(dst)
-.Ldone:
-	jr	ra
-	 nop
-	END(__copy_user_inatomic)
-
-.Ll_exc_copy:
-	/*
-	 * Copy bytes from src until faulting load address (or until a
-	 * lb faults)
-	 *
-	 * When reached by a faulting LDFIRST/LDREST, THREAD_BUADDR($28)
-	 * may be more than a byte beyond the last address.
-	 * Hence, the lb below may get an exception.
-	 *
-	 * Assumes src < THREAD_BUADDR($28)
-	 */
-	LOAD	t0, TI_TASK($28)
-	 nop
-	LOAD	t0, THREAD_BUADDR(t0)
-1:
-EXC(	lb	t1, 0(src),	.Ll_exc)
-	ADD	src, src, 1
-	sb	t1, 0(dst)	# can't fault -- we're copy_from_user
-	.set	reorder				/* DADDI_WAR */
-	ADD	dst, dst, 1
-	bne	src, t0, 1b
-	.set	noreorder
-.Ll_exc:
-	LOAD	t0, TI_TASK($28)
-	 nop
-	LOAD	t0, THREAD_BUADDR(t0)	# t0 is just past last good address
-	 nop
-	SUB	len, AT, t0		# len number of uncopied bytes
-	jr	ra
-	 nop

arch/mips/lib/memcpy.S

@@ -182,6 +182,14 @@
 	.set	at=v1
 #endif
 
+/*
+ * t6 is used as a flag to note inatomic mode.
+ */
+LEAF(__copy_user_inatomic)
+	b	__copy_user_common
+	 li	t6, 1
+	END(__copy_user_inatomic)
+
 /*
  * A combined memcpy/__copy_user
  * __copy_user sets len to 0 for success; else to an upper bound of
@@ -193,6 +201,8 @@ LEAF(memcpy)					/* a0=dst a1=src a2=len */
 	move	v0, dst				/* return value */
 .L__memcpy:
 FEXPORT(__copy_user)
+	li	t6, 0	/* not inatomic */
+__copy_user_common:
 	/*
 	 * Note: dst & src may be unaligned, len may be 0
 	 * Temps
@@ -458,6 +468,7 @@ EXC(	lb	t1, 0(src),	.Ll_exc)
 	LOAD	t0, THREAD_BUADDR(t0)	# t0 is just past last good address
 	 nop
 	SUB	len, AT, t0		# len number of uncopied bytes
+	bnez	t6, .Ldone	/* Skip the zeroing part if inatomic */
 	/*
 	 * Here's where we rely on src and dst being incremented in tandem,
 	 *   See (3) above.