[PATCH] xtensa: Architecture support for Tensilica Xtensa Part 4

The attached patches provides part 4 of an architecture implementation for the
Tensilica Xtensa CPU series.

Signed-off-by: Chris Zankel <chris@zankel.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 321 insertions, 0 deletions

diff --git a/arch/xtensa/lib/usercopy.S b/arch/xtensa/lib/usercopy.S
new file mode 100644
index 0000000..265db26
--- /dev/null
+++ b/arch/xtensa/lib/usercopy.S
@@ -0,0 +1,321 @@
+/*
+ *  arch/xtensa/lib/usercopy.S
+ *
+ *  Copy to/from user space (derived from arch/xtensa/lib/hal/memcopy.S)
+ *
+ *  DO NOT COMBINE this function with <arch/xtensa/lib/hal/memcopy.S>.
+ *  It needs to remain separate and distinct.  The hal files are part
+ *  of the the Xtensa link-time HAL, and those files may differ per
+ *  processor configuration.  Patching the kernel for another
+ *  processor configuration includes replacing the hal files, and we
+ *  could loose the special functionality for accessing user-space
+ *  memory during such a patch.  We sacrifice a little code space here
+ *  in favor to simplify code maintenance.
+ *
+ *  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.
+ *
+ *  Copyright (C) 2002 Tensilica Inc.
+ */
+
+
+/*
+ * size_t __xtensa_copy_user (void *dst, const void *src, size_t len);
+ *
+ * The returned value is the number of bytes not copied.  Implies zero
+ * is success.
+ *
+ * The general case algorithm is as follows:
+ *   If the destination and source are both aligned,
+ *     do 16B chunks with a loop, and then finish up with
+ *     8B, 4B, 2B, and 1B copies conditional on the length.
+ *   If destination is aligned and source unaligned,
+ *     do the same, but use SRC to align the source data.
+ *   If destination is unaligned, align it by conditionally
+ *     copying 1B and 2B and then retest.
+ *   This code tries to use fall-through braches for the common
+ *     case of aligned destinations (except for the branches to
+ *     the alignment label).
+ *
+ * Register use:
+ *	a0/ return address
+ *	a1/ stack pointer
+ *	a2/ return value
+ *	a3/ src
+ *	a4/ length
+ *	a5/ dst
+ *	a6/ tmp
+ *	a7/ tmp
+ *	a8/ tmp
+ *	a9/ tmp
+ *	a10/ tmp
+ *	a11/ original length
+ */
+
+#include <xtensa/coreasm.h>
+
+#ifdef __XTENSA_EB__
+#define ALIGN(R, W0, W1) src	R, W0, W1
+#define SSA8(R)	ssa8b R
+#else
+#define ALIGN(R, W0, W1) src	R, W1, W0
+#define SSA8(R)	ssa8l R
+#endif
+
+/* Load or store instructions that may cause exceptions use the EX macro. */
+
+#define EX(insn,reg1,reg2,offset,handler)	\
+9:	insn	reg1, reg2, offset;		\
+	.section __ex_table, "a";		\
+	.word	9b, handler;			\
+	.previous
+
+
+	.text
+	.align	4
+	.global	__xtensa_copy_user
+	.type	__xtensa_copy_user,@function
+__xtensa_copy_user:
+	entry	sp, 16		# minimal stack frame
+	# a2/ dst, a3/ src, a4/ len
+	mov	a5, a2		# copy dst so that a2 is return value
+	mov	a11, a4		# preserve original len for error case
+.Lcommon:
+	bbsi.l	a2, 0, .Ldst1mod2 # if dst is 1 mod 2
+	bbsi.l	a2, 1, .Ldst2mod4 # if dst is 2 mod 4
+.Ldstaligned:	# return here from .Ldstunaligned when dst is aligned
+	srli	a7, a4, 4	# number of loop iterations with 16B
+				# per iteration
+	movi	a8, 3		  # if source is also aligned,
+	bnone	a3, a8, .Laligned # then use word copy
+	SSA8(	a3)		# set shift amount from byte offset
+	bnez	a4, .Lsrcunaligned
+	movi	a2, 0		# return success for len==0
+	retw
+
+/*
+ * Destination is unaligned
+ */
+
+.Ldst1mod2:	# dst is only byte aligned
+	bltui	a4, 7, .Lbytecopy	# do short copies byte by byte
+
+	# copy 1 byte
+	EX(l8ui, a6, a3, 0, l_fixup)
+	addi	a3, a3,  1
+	EX(s8i, a6, a5,  0, s_fixup)
+	addi	a5, a5,  1
+	addi	a4, a4, -1
+	bbci.l	a5, 1, .Ldstaligned	# if dst is now aligned, then
+					# return to main algorithm
+.Ldst2mod4:	# dst 16-bit aligned
+	# copy 2 bytes
+	bltui	a4, 6, .Lbytecopy	# do short copies byte by byte
+	EX(l8ui, a6, a3, 0, l_fixup)
+	EX(l8ui, a7, a3, 1, l_fixup)
+	addi	a3, a3,  2
+	EX(s8i, a6, a5,  0, s_fixup)
+	EX(s8i, a7, a5,  1, s_fixup)
+	addi	a5, a5,  2
+	addi	a4, a4, -2
+	j	.Ldstaligned	# dst is now aligned, return to main algorithm
+
+/*
+ * Byte by byte copy
+ */
+	.align	4
+	.byte	0		# 1 mod 4 alignment for LOOPNEZ
+				# (0 mod 4 alignment for LBEG)
+.Lbytecopy:
+#if XCHAL_HAVE_LOOPS
+	loopnez	a4, .Lbytecopydone
+#else /* !XCHAL_HAVE_LOOPS */
+	beqz	a4, .Lbytecopydone
+	add	a7, a3, a4	# a7 = end address for source
+#endif /* !XCHAL_HAVE_LOOPS */
+.Lnextbyte:
+	EX(l8ui, a6, a3, 0, l_fixup)
+	addi	a3, a3, 1
+	EX(s8i, a6, a5, 0, s_fixup)
+	addi	a5, a5, 1
+#if !XCHAL_HAVE_LOOPS
+	blt	a3, a7, .Lnextbyte
+#endif /* !XCHAL_HAVE_LOOPS */
+.Lbytecopydone:
+	movi	a2, 0		# return success for len bytes copied
+	retw
+
+/*
+ * Destination and source are word-aligned.
+ */
+	# copy 16 bytes per iteration for word-aligned dst and word-aligned src
+	.align	4		# 1 mod 4 alignment for LOOPNEZ
+	.byte	0		# (0 mod 4 alignment for LBEG)
+.Laligned:
+#if XCHAL_HAVE_LOOPS
+	loopnez	a7, .Loop1done
+#else /* !XCHAL_HAVE_LOOPS */
+	beqz	a7, .Loop1done
+	slli	a8, a7, 4
+	add	a8, a8, a3	# a8 = end of last 16B source chunk
+#endif /* !XCHAL_HAVE_LOOPS */
+.Loop1:
+	EX(l32i, a6, a3,  0, l_fixup)
+	EX(l32i, a7, a3,  4, l_fixup)
+	EX(s32i, a6, a5,  0, s_fixup)
+	EX(l32i, a6, a3,  8, l_fixup)
+	EX(s32i, a7, a5,  4, s_fixup)
+	EX(l32i, a7, a3, 12, l_fixup)
+	EX(s32i, a6, a5,  8, s_fixup)
+	addi	a3, a3, 16
+	EX(s32i, a7, a5, 12, s_fixup)
+	addi	a5, a5, 16
+#if !XCHAL_HAVE_LOOPS
+	blt	a3, a8, .Loop1
+#endif /* !XCHAL_HAVE_LOOPS */
+.Loop1done:
+	bbci.l	a4, 3, .L2
+	# copy 8 bytes
+	EX(l32i, a6, a3,  0, l_fixup)
+	EX(l32i, a7, a3,  4, l_fixup)
+	addi	a3, a3,  8
+	EX(s32i, a6, a5,  0, s_fixup)
+	EX(s32i, a7, a5,  4, s_fixup)
+	addi	a5, a5,  8
+.L2:
+	bbci.l	a4, 2, .L3
+	# copy 4 bytes
+	EX(l32i, a6, a3,  0, l_fixup)
+	addi	a3, a3,  4
+	EX(s32i, a6, a5,  0, s_fixup)
+	addi	a5, a5,  4
+.L3:
+	bbci.l	a4, 1, .L4
+	# copy 2 bytes
+	EX(l16ui, a6, a3,  0, l_fixup)
+	addi	a3, a3,  2
+	EX(s16i,  a6, a5,  0, s_fixup)
+	addi	a5, a5,  2
+.L4:
+	bbci.l	a4, 0, .L5
+	# copy 1 byte
+	EX(l8ui, a6, a3,  0, l_fixup)
+	EX(s8i,  a6, a5,  0, s_fixup)
+.L5:
+	movi	a2, 0		# return success for len bytes copied
+	retw
+
+/*
+ * Destination is aligned, Source is unaligned
+ */
+
+	.align	4
+	.byte	0		# 1 mod 4 alignement for LOOPNEZ
+				# (0 mod 4 alignment for LBEG)
+.Lsrcunaligned:
+	# copy 16 bytes per iteration for word-aligned dst and unaligned src
+	and	a10, a3, a8	# save unalignment offset for below
+	sub	a3, a3, a10	# align a3 (to avoid sim warnings only; not needed for hardware)
+	EX(l32i, a6, a3, 0, l_fixup)	# load first word
+#if XCHAL_HAVE_LOOPS
+	loopnez	a7, .Loop2done
+#else /* !XCHAL_HAVE_LOOPS */
+	beqz	a7, .Loop2done
+	slli	a10, a7, 4
+	add	a10, a10, a3	# a10 = end of last 16B source chunk
+#endif /* !XCHAL_HAVE_LOOPS */
+.Loop2:
+	EX(l32i, a7, a3,  4, l_fixup)
+	EX(l32i, a8, a3,  8, l_fixup)
+	ALIGN(	a6, a6, a7)
+	EX(s32i, a6, a5,  0, s_fixup)
+	EX(l32i, a9, a3, 12, l_fixup)
+	ALIGN(	a7, a7, a8)
+	EX(s32i, a7, a5,  4, s_fixup)
+	EX(l32i, a6, a3, 16, l_fixup)
+	ALIGN(	a8, a8, a9)
+	EX(s32i, a8, a5,  8, s_fixup)
+	addi	a3, a3, 16
+	ALIGN(	a9, a9, a6)
+	EX(s32i, a9, a5, 12, s_fixup)
+	addi	a5, a5, 16
+#if !XCHAL_HAVE_LOOPS
+	blt	a3, a10, .Loop2
+#endif /* !XCHAL_HAVE_LOOPS */
+.Loop2done:
+	bbci.l	a4, 3, .L12
+	# copy 8 bytes
+	EX(l32i, a7, a3,  4, l_fixup)
+	EX(l32i, a8, a3,  8, l_fixup)
+	ALIGN(	a6, a6, a7)
+	EX(s32i, a6, a5,  0, s_fixup)
+	addi	a3, a3,  8
+	ALIGN(	a7, a7, a8)
+	EX(s32i, a7, a5,  4, s_fixup)
+	addi	a5, a5,  8
+	mov	a6, a8
+.L12:
+	bbci.l	a4, 2, .L13
+	# copy 4 bytes
+	EX(l32i, a7, a3,  4, l_fixup)
+	addi	a3, a3,  4
+	ALIGN(	a6, a6, a7)
+	EX(s32i, a6, a5,  0, s_fixup)
+	addi	a5, a5,  4
+	mov	a6, a7
+.L13:
+	add	a3, a3, a10	# readjust a3 with correct misalignment
+	bbci.l	a4, 1, .L14
+	# copy 2 bytes
+	EX(l8ui, a6, a3,  0, l_fixup)
+	EX(l8ui, a7, a3,  1, l_fixup)
+	addi	a3, a3,  2
+	EX(s8i, a6, a5,  0, s_fixup)
+	EX(s8i, a7, a5,  1, s_fixup)
+	addi	a5, a5,  2
+.L14:
+	bbci.l	a4, 0, .L15
+	# copy 1 byte
+	EX(l8ui, a6, a3,  0, l_fixup)
+	EX(s8i,  a6, a5,  0, s_fixup)
+.L15:
+	movi	a2, 0		# return success for len bytes copied
+	retw
+
+
+	.section .fixup, "ax"
+	.align	4
+
+/* a2 = original dst; a5 = current dst; a11= original len
+ * bytes_copied = a5 - a2
+ * retval = bytes_not_copied = original len - bytes_copied
+ * retval = a11 - (a5 - a2)
+ *
+ * Clearing the remaining pieces of kernel memory plugs security
+ * holes.  This functionality is the equivalent of the *_zeroing
+ * functions that some architectures provide.
+ */
+
+.Lmemset:
+	.word	memset
+
+s_fixup:
+	sub	a2, a5, a2	/* a2 <-- bytes copied */
+	sub	a2, a11, a2	/* a2 <-- bytes not copied */
+	retw
+
+l_fixup:
+	sub	a2, a5, a2	/* a2 <-- bytes copied */
+	sub	a2, a11, a2	/* a2 <-- bytes not copied == return value */
+
+	/* void *memset(void *s, int c, size_t n); */
+	mov	a6, a5		/* s */
+	movi	a7, 0		/* c */
+	mov	a8, a2		/* n */
+	l32r	a4, .Lmemset
+	callx4	a4
+	/* Ignore memset return value in a6. */
+	/* a2 still contains bytes not copied. */
+	retw
+