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+/*
+ * Copyright 2010 Tilera Corporation. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, version 2.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
+ * NON INFRINGEMENT. See the GNU General Public License for
+ * more details.
+ *
+ * This file shares the implementation of the userspace memcpy and
+ * the kernel's memcpy, copy_to_user and copy_from_user.
+ */
+
+#include <arch/chip.h>
+
+
+#include <linux/linkage.h>
+
+/* On TILE64, we wrap these functions via arch/tile/lib/memcpy_tile64.c */
+#if !CHIP_HAS_COHERENT_LOCAL_CACHE()
+#define memcpy __memcpy_asm
+#define __copy_to_user_inatomic __copy_to_user_inatomic_asm
+#define __copy_from_user_inatomic __copy_from_user_inatomic_asm
+#define __copy_from_user_zeroing __copy_from_user_zeroing_asm
+#endif
+
+#define IS_MEMCPY 0
+#define IS_COPY_FROM_USER 1
+#define IS_COPY_FROM_USER_ZEROING 2
+#define IS_COPY_TO_USER -1
+
+ .section .text.memcpy_common, "ax"
+ .align 64
+
+/* Use this to preface each bundle that can cause an exception so
+ * the kernel can clean up properly. The special cleanup code should
+ * not use these, since it knows what it is doing.
+ */
+#define EX \
+ .pushsection __ex_table, "a"; \
+ .word 9f, memcpy_common_fixup; \
+ .popsection; \
+ 9
+
+
+/* __copy_from_user_inatomic takes the kernel target address in r0,
+ * the user source in r1, and the bytes to copy in r2.
+ * It returns the number of uncopiable bytes (hopefully zero) in r0.
+ */
+ENTRY(__copy_from_user_inatomic)
+.type __copy_from_user_inatomic, @function
+ FEEDBACK_ENTER_EXPLICIT(__copy_from_user_inatomic, \
+ .text.memcpy_common, \
+ .Lend_memcpy_common - __copy_from_user_inatomic)
+ { movei r29, IS_COPY_FROM_USER; j memcpy_common }
+ .size __copy_from_user_inatomic, . - __copy_from_user_inatomic
+
+/* __copy_from_user_zeroing is like __copy_from_user_inatomic, but
+ * any uncopiable bytes are zeroed in the target.
+ */
+ENTRY(__copy_from_user_zeroing)
+.type __copy_from_user_zeroing, @function
+ FEEDBACK_REENTER(__copy_from_user_inatomic)
+ { movei r29, IS_COPY_FROM_USER_ZEROING; j memcpy_common }
+ .size __copy_from_user_zeroing, . - __copy_from_user_zeroing
+
+/* __copy_to_user_inatomic takes the user target address in r0,
+ * the kernel source in r1, and the bytes to copy in r2.
+ * It returns the number of uncopiable bytes (hopefully zero) in r0.
+ */
+ENTRY(__copy_to_user_inatomic)
+.type __copy_to_user_inatomic, @function
+ FEEDBACK_REENTER(__copy_from_user_inatomic)
+ { movei r29, IS_COPY_TO_USER; j memcpy_common }
+ .size __copy_to_user_inatomic, . - __copy_to_user_inatomic
+
+ENTRY(memcpy)
+.type memcpy, @function
+ FEEDBACK_REENTER(__copy_from_user_inatomic)
+ { movei r29, IS_MEMCPY }
+ .size memcpy, . - memcpy
+ /* Fall through */
+
+ .type memcpy_common, @function
+memcpy_common:
+ /* On entry, r29 holds one of the IS_* macro values from above. */
+
+
+ /* r0 is the dest, r1 is the source, r2 is the size. */
+
+ /* Save aside original dest so we can return it at the end. */
+ { sw sp, lr; move r23, r0; or r4, r0, r1 }
+
+ /* Check for an empty size. */
+ { bz r2, .Ldone; andi r4, r4, 3 }
+
+ /* Save aside original values in case of a fault. */
+ { move r24, r1; move r25, r2 }
+ move r27, lr
+
+ /* Check for an unaligned source or dest. */
+ { bnz r4, .Lcopy_unaligned_maybe_many; addli r4, r2, -256 }
+
+.Lcheck_aligned_copy_size:
+ /* If we are copying < 256 bytes, branch to simple case. */
+ { blzt r4, .Lcopy_8_check; slti_u r8, r2, 8 }
+
+ /* Copying >= 256 bytes, so jump to complex prefetching loop. */
+ { andi r6, r1, 63; j .Lcopy_many }
+
+/*
+ *
+ * Aligned 4 byte at a time copy loop
+ *
+ */
+
+.Lcopy_8_loop:
+ /* Copy two words at a time to hide load latency. */
+EX: { lw r3, r1; addi r1, r1, 4; slti_u r8, r2, 16 }
+EX: { lw r4, r1; addi r1, r1, 4 }
+EX: { sw r0, r3; addi r0, r0, 4; addi r2, r2, -4 }
+EX: { sw r0, r4; addi r0, r0, 4; addi r2, r2, -4 }
+.Lcopy_8_check:
+ { bzt r8, .Lcopy_8_loop; slti_u r4, r2, 4 }
+
+ /* Copy odd leftover word, if any. */
+ { bnzt r4, .Lcheck_odd_stragglers }
+EX: { lw r3, r1; addi r1, r1, 4 }
+EX: { sw r0, r3; addi r0, r0, 4; addi r2, r2, -4 }
+
+.Lcheck_odd_stragglers:
+ { bnz r2, .Lcopy_unaligned_few }
+
+.Ldone:
+ /* For memcpy return original dest address, else zero. */
+ { mz r0, r29, r23; jrp lr }
+
+
+/*
+ *
+ * Prefetching multiple cache line copy handler (for large transfers).
+ *
+ */
+
+ /* Copy words until r1 is cache-line-aligned. */
+.Lalign_loop:
+EX: { lw r3, r1; addi r1, r1, 4 }
+ { andi r6, r1, 63 }
+EX: { sw r0, r3; addi r0, r0, 4; addi r2, r2, -4 }
+.Lcopy_many:
+ { bnzt r6, .Lalign_loop; addi r9, r0, 63 }
+
+ { addi r3, r1, 60; andi r9, r9, -64 }
+
+#if CHIP_HAS_WH64()
+ /* No need to prefetch dst, we'll just do the wh64
+ * right before we copy a line.
+ */
+#endif
+
+EX: { lw r5, r3; addi r3, r3, 64; movei r4, 1 }
+ /* Intentionally stall for a few cycles to leave L2 cache alone. */
+ { bnzt zero, .; move r27, lr }
+EX: { lw r6, r3; addi r3, r3, 64 }
+ /* Intentionally stall for a few cycles to leave L2 cache alone. */
+ { bnzt zero, . }
+EX: { lw r7, r3; addi r3, r3, 64 }
+#if !CHIP_HAS_WH64()
+ /* Prefetch the dest */
+ /* Intentionally stall for a few cycles to leave L2 cache alone. */
+ { bnzt zero, . }
+ /* Use a real load to cause a TLB miss if necessary. We aren't using
+ * r28, so this should be fine.
+ */
+EX: { lw r28, r9; addi r9, r9, 64 }
+ /* Intentionally stall for a few cycles to leave L2 cache alone. */
+ { bnzt zero, . }
+ { prefetch r9; addi r9, r9, 64 }
+ /* Intentionally stall for a few cycles to leave L2 cache alone. */
+ { bnzt zero, . }
+ { prefetch r9; addi r9, r9, 64 }
+#endif
+ /* Intentionally stall for a few cycles to leave L2 cache alone. */
+ { bz zero, .Lbig_loop2 }
+
+ /* On entry to this loop:
+ * - r0 points to the start of dst line 0
+ * - r1 points to start of src line 0
+ * - r2 >= (256 - 60), only the first time the loop trips.
+ * - r3 contains r1 + 128 + 60 [pointer to end of source line 2]
+ * This is our prefetch address. When we get near the end
+ * rather than prefetching off the end this is changed to point
+ * to some "safe" recently loaded address.
+ * - r5 contains *(r1 + 60) [i.e. last word of source line 0]
+ * - r6 contains *(r1 + 64 + 60) [i.e. last word of source line 1]
+ * - r9 contains ((r0 + 63) & -64)
+ * [start of next dst cache line.]
+ */
+
+.Lbig_loop:
+ { jal .Lcopy_line2; add r15, r1, r2 }
+
+.Lbig_loop2:
+ /* Copy line 0, first stalling until r5 is ready. */
+EX: { move r12, r5; lw r16, r1 }
+ { bz r4, .Lcopy_8_check; slti_u r8, r2, 8 }
+ /* Prefetch several lines ahead. */
+EX: { lw r5, r3; addi r3, r3, 64 }
+ { jal .Lcopy_line }
+
+ /* Copy line 1, first stalling until r6 is ready. */
+EX: { move r12, r6; lw r16, r1 }
+ { bz r4, .Lcopy_8_check; slti_u r8, r2, 8 }
+ /* Prefetch several lines ahead. */
+EX: { lw r6, r3; addi r3, r3, 64 }
+ { jal .Lcopy_line }
+
+ /* Copy line 2, first stalling until r7 is ready. */
+EX: { move r12, r7; lw r16, r1 }
+ { bz r4, .Lcopy_8_check; slti_u r8, r2, 8 }
+ /* Prefetch several lines ahead. */
+EX: { lw r7, r3; addi r3, r3, 64 }
+ /* Use up a caches-busy cycle by jumping back to the top of the
+ * loop. Might as well get it out of the way now.
+ */
+ { j .Lbig_loop }
+
+
+ /* On entry:
+ * - r0 points to the destination line.
+ * - r1 points to the source line.
+ * - r3 is the next prefetch address.
+ * - r9 holds the last address used for wh64.
+ * - r12 = WORD_15
+ * - r16 = WORD_0.
+ * - r17 == r1 + 16.
+ * - r27 holds saved lr to restore.
+ *
+ * On exit:
+ * - r0 is incremented by 64.
+ * - r1 is incremented by 64, unless that would point to a word
+ * beyond the end of the source array, in which case it is redirected
+ * to point to an arbitrary word already in the cache.
+ * - r2 is decremented by 64.
+ * - r3 is unchanged, unless it points to a word beyond the
+ * end of the source array, in which case it is redirected
+ * to point to an arbitrary word already in the cache.
+ * Redirecting is OK since if we are that close to the end
+ * of the array we will not come back to this subroutine
+ * and use the contents of the prefetched address.
+ * - r4 is nonzero iff r2 >= 64.
+ * - r9 is incremented by 64, unless it points beyond the
+ * end of the last full destination cache line, in which
+ * case it is redirected to a "safe address" that can be
+ * clobbered (sp - 64)
+ * - lr contains the value in r27.
+ */
+
+/* r26 unused */
+
+.Lcopy_line:
+ /* TODO: when r3 goes past the end, we would like to redirect it
+ * to prefetch the last partial cache line (if any) just once, for the
+ * benefit of the final cleanup loop. But we don't want to
+ * prefetch that line more than once, or subsequent prefetches
+ * will go into the RTF. But then .Lbig_loop should unconditionally
+ * branch to top of loop to execute final prefetch, and its
+ * nop should become a conditional branch.
+ */
+
+ /* We need two non-memory cycles here to cover the resources
+ * used by the loads initiated by the caller.
+ */
+ { add r15, r1, r2 }
+.Lcopy_line2:
+ { slt_u r13, r3, r15; addi r17, r1, 16 }
+
+ /* NOTE: this will stall for one cycle as L1 is busy. */
+
+ /* Fill second L1D line. */
+EX: { lw r17, r17; addi r1, r1, 48; mvz r3, r13, r1 } /* r17 = WORD_4 */
+
+#if CHIP_HAS_WH64()
+ /* Prepare destination line for writing. */
+EX: { wh64 r9; addi r9, r9, 64 }
+#else
+ /* Prefetch dest line */
+ { prefetch r9; addi r9, r9, 64 }
+#endif
+ /* Load seven words that are L1D hits to cover wh64 L2 usage. */
+
+ /* Load the three remaining words from the last L1D line, which
+ * we know has already filled the L1D.
+ */
+EX: { lw r4, r1; addi r1, r1, 4; addi r20, r1, 16 } /* r4 = WORD_12 */
+EX: { lw r8, r1; addi r1, r1, 4; slt_u r13, r20, r15 }/* r8 = WORD_13 */
+EX: { lw r11, r1; addi r1, r1, -52; mvz r20, r13, r1 } /* r11 = WORD_14 */
+
+ /* Load the three remaining words from the first L1D line, first
+ * stalling until it has filled by "looking at" r16.
+ */
+EX: { lw r13, r1; addi r1, r1, 4; move zero, r16 } /* r13 = WORD_1 */
+EX: { lw r14, r1; addi r1, r1, 4 } /* r14 = WORD_2 */
+EX: { lw r15, r1; addi r1, r1, 8; addi r10, r0, 60 } /* r15 = WORD_3 */
+
+ /* Load second word from the second L1D line, first
+ * stalling until it has filled by "looking at" r17.
+ */
+EX: { lw r19, r1; addi r1, r1, 4; move zero, r17 } /* r19 = WORD_5 */
+
+ /* Store last word to the destination line, potentially dirtying it
+ * for the first time, which keeps the L2 busy for two cycles.
+ */
+EX: { sw r10, r12 } /* store(WORD_15) */
+
+ /* Use two L1D hits to cover the sw L2 access above. */
+EX: { lw r10, r1; addi r1, r1, 4 } /* r10 = WORD_6 */
+EX: { lw r12, r1; addi r1, r1, 4 } /* r12 = WORD_7 */
+
+ /* Fill third L1D line. */
+EX: { lw r18, r1; addi r1, r1, 4 } /* r18 = WORD_8 */
+
+ /* Store first L1D line. */
+EX: { sw r0, r16; addi r0, r0, 4; add r16, r0, r2 } /* store(WORD_0) */
+EX: { sw r0, r13; addi r0, r0, 4; andi r16, r16, -64 } /* store(WORD_1) */
+EX: { sw r0, r14; addi r0, r0, 4; slt_u r16, r9, r16 } /* store(WORD_2) */
+#if CHIP_HAS_WH64()
+EX: { sw r0, r15; addi r0, r0, 4; addi r13, sp, -64 } /* store(WORD_3) */
+#else
+ /* Back up the r9 to a cache line we are already storing to
+ * if it gets past the end of the dest vector. Strictly speaking,
+ * we don't need to back up to the start of a cache line, but it's free
+ * and tidy, so why not?
+ */
+EX: { sw r0, r15; addi r0, r0, 4; andi r13, r0, -64 } /* store(WORD_3) */
+#endif
+ /* Store second L1D line. */
+EX: { sw r0, r17; addi r0, r0, 4; mvz r9, r16, r13 }/* store(WORD_4) */
+EX: { sw r0, r19; addi r0, r0, 4 } /* store(WORD_5) */
+EX: { sw r0, r10; addi r0, r0, 4 } /* store(WORD_6) */
+EX: { sw r0, r12; addi r0, r0, 4 } /* store(WORD_7) */
+
+EX: { lw r13, r1; addi r1, r1, 4; move zero, r18 } /* r13 = WORD_9 */
+EX: { lw r14, r1; addi r1, r1, 4 } /* r14 = WORD_10 */
+EX: { lw r15, r1; move r1, r20 } /* r15 = WORD_11 */
+
+ /* Store third L1D line. */
+EX: { sw r0, r18; addi r0, r0, 4 } /* store(WORD_8) */
+EX: { sw r0, r13; addi r0, r0, 4 } /* store(WORD_9) */
+EX: { sw r0, r14; addi r0, r0, 4 } /* store(WORD_10) */
+EX: { sw r0, r15; addi r0, r0, 4 } /* store(WORD_11) */
+
+ /* Store rest of fourth L1D line. */
+EX: { sw r0, r4; addi r0, r0, 4 } /* store(WORD_12) */
+ {
+EX: sw r0, r8 /* store(WORD_13) */
+ addi r0, r0, 4
+ /* Will r2 be > 64 after we subtract 64 below? */
+ shri r4, r2, 7
+ }
+ {
+EX: sw r0, r11 /* store(WORD_14) */
+ addi r0, r0, 8
+ /* Record 64 bytes successfully copied. */
+ addi r2, r2, -64
+ }
+
+ { jrp lr; move lr, r27 }
+
+ /* Convey to the backtrace library that the stack frame is size
+ * zero, and the real return address is on the stack rather than
+ * in 'lr'.
+ */
+ { info 8 }
+
+ .align 64
+.Lcopy_unaligned_maybe_many:
+ /* Skip the setup overhead if we aren't copying many bytes. */
+ { slti_u r8, r2, 20; sub r4, zero, r0 }
+ { bnzt r8, .Lcopy_unaligned_few; andi r4, r4, 3 }
+ { bz r4, .Ldest_is_word_aligned; add r18, r1, r2 }
+
+/*
+ *
+ * unaligned 4 byte at a time copy handler.
+ *
+ */
+
+ /* Copy single bytes until r0 == 0 mod 4, so we can store words. */
+.Lalign_dest_loop:
+EX: { lb_u r3, r1; addi r1, r1, 1; addi r4, r4, -1 }
+EX: { sb r0, r3; addi r0, r0, 1; addi r2, r2, -1 }
+ { bnzt r4, .Lalign_dest_loop; andi r3, r1, 3 }
+
+ /* If source and dest are now *both* aligned, do an aligned copy. */
+ { bz r3, .Lcheck_aligned_copy_size; addli r4, r2, -256 }
+
+.Ldest_is_word_aligned:
+
+#if CHIP_HAS_DWORD_ALIGN()
+EX: { andi r8, r0, 63; lwadd_na r6, r1, 4}
+ { slti_u r9, r2, 64; bz r8, .Ldest_is_L2_line_aligned }
+
+ /* This copies unaligned words until either there are fewer
+ * than 4 bytes left to copy, or until the destination pointer
+ * is cache-aligned, whichever comes first.
+ *
+ * On entry:
+ * - r0 is the next store address.
+ * - r1 points 4 bytes past the load address corresponding to r0.
+ * - r2 >= 4
+ * - r6 is the next aligned word loaded.
+ */
+.Lcopy_unaligned_src_words:
+EX: { lwadd_na r7, r1, 4; slti_u r8, r2, 4 + 4 }
+ /* stall */
+ { dword_align r6, r7, r1; slti_u r9, r2, 64 + 4 }
+EX: { swadd r0, r6, 4; addi r2, r2, -4 }
+ { bnz r8, .Lcleanup_unaligned_words; andi r8, r0, 63 }
+ { bnzt r8, .Lcopy_unaligned_src_words; move r6, r7 }
+
+ /* On entry:
+ * - r0 is the next store address.
+ * - r1 points 4 bytes past the load address corresponding to r0.
+ * - r2 >= 4 (# of bytes left to store).
+ * - r6 is the next aligned src word value.
+ * - r9 = (r2 < 64U).
+ * - r18 points one byte past the end of source memory.
+ */
+.Ldest_is_L2_line_aligned:
+
+ {
+ /* Not a full cache line remains. */
+ bnz r9, .Lcleanup_unaligned_words
+ move r7, r6
+ }
+
+ /* r2 >= 64 */
+
+ /* Kick off two prefetches, but don't go past the end. */
+ { addi r3, r1, 63 - 4; addi r8, r1, 64 + 63 - 4 }
+ { prefetch r3; move r3, r8; slt_u r8, r8, r18 }
+ { mvz r3, r8, r1; addi r8, r3, 64 }
+ { prefetch r3; move r3, r8; slt_u r8, r8, r18 }
+ { mvz r3, r8, r1; movei r17, 0 }
+
+.Lcopy_unaligned_line:
+ /* Prefetch another line. */
+ { prefetch r3; addi r15, r1, 60; addi r3, r3, 64 }
+ /* Fire off a load of the last word we are about to copy. */
+EX: { lw_na r15, r15; slt_u r8, r3, r18 }
+
+EX: { mvz r3, r8, r1; wh64 r0 }
+
+ /* This loop runs twice.
+ *
+ * On entry:
+ * - r17 is even before the first iteration, and odd before
+ * the second. It is incremented inside the loop. Encountering
+ * an even value at the end of the loop makes it stop.
+ */
+.Lcopy_half_an_unaligned_line:
+EX: {
+ /* Stall until the last byte is ready. In the steady state this
+ * guarantees all words to load below will be in the L2 cache, which
+ * avoids shunting the loads to the RTF.
+ */
+ move zero, r15
+ lwadd_na r7, r1, 16
+ }
+EX: { lwadd_na r11, r1, 12 }
+EX: { lwadd_na r14, r1, -24 }
+EX: { lwadd_na r8, r1, 4 }
+EX: { lwadd_na r9, r1, 4 }
+EX: {
+ lwadd_na r10, r1, 8
+ /* r16 = (r2 < 64), after we subtract 32 from r2 below. */
+ slti_u r16, r2, 64 + 32
+ }
+EX: { lwadd_na r12, r1, 4; addi r17, r17, 1 }
+EX: { lwadd_na r13, r1, 8; dword_align r6, r7, r1 }
+EX: { swadd r0, r6, 4; dword_align r7, r8, r1 }
+EX: { swadd r0, r7, 4; dword_align r8, r9, r1 }
+EX: { swadd r0, r8, 4; dword_align r9, r10, r1 }
+EX: { swadd r0, r9, 4; dword_align r10, r11, r1 }
+EX: { swadd r0, r10, 4; dword_align r11, r12, r1 }
+EX: { swadd r0, r11, 4; dword_align r12, r13, r1 }
+EX: { swadd r0, r12, 4; dword_align r13, r14, r1 }
+EX: { swadd r0, r13, 4; addi r2, r2, -32 }
+ { move r6, r14; bbst r17, .Lcopy_half_an_unaligned_line }
+
+ { bzt r16, .Lcopy_unaligned_line; move r7, r6 }
+
+ /* On entry:
+ * - r0 is the next store address.
+ * - r1 points 4 bytes past the load address corresponding to r0.
+ * - r2 >= 0 (# of bytes left to store).
+ * - r7 is the next aligned src word value.
+ */
+.Lcleanup_unaligned_words:
+ /* Handle any trailing bytes. */
+ { bz r2, .Lcopy_unaligned_done; slti_u r8, r2, 4 }
+ { bzt r8, .Lcopy_unaligned_src_words; move r6, r7 }
+
+ /* Move r1 back to the point where it corresponds to r0. */
+ { addi r1, r1, -4 }
+
+#else /* !CHIP_HAS_DWORD_ALIGN() */
+
+ /* Compute right/left shift counts and load initial source words. */
+ { andi r5, r1, -4; andi r3, r1, 3 }
+EX: { lw r6, r5; addi r5, r5, 4; shli r3, r3, 3 }
+EX: { lw r7, r5; addi r5, r5, 4; sub r4, zero, r3 }
+
+ /* Load and store one word at a time, using shifts and ORs
+ * to correct for the misaligned src.
+ */
+.Lcopy_unaligned_src_loop:
+ { shr r6, r6, r3; shl r8, r7, r4 }
+EX: { lw r7, r5; or r8, r8, r6; move r6, r7 }
+EX: { sw r0, r8; addi r0, r0, 4; addi r2, r2, -4 }
+ { addi r5, r5, 4; slti_u r8, r2, 8 }
+ { bzt r8, .Lcopy_unaligned_src_loop; addi r1, r1, 4 }
+
+ { bz r2, .Lcopy_unaligned_done }
+#endif /* !CHIP_HAS_DWORD_ALIGN() */
+
+ /* Fall through */
+
+/*
+ *
+ * 1 byte at a time copy handler.
+ *
+ */
+
+.Lcopy_unaligned_few:
+EX: { lb_u r3, r1; addi r1, r1, 1 }
+EX: { sb r0, r3; addi r0, r0, 1; addi r2, r2, -1 }
+ { bnzt r2, .Lcopy_unaligned_few }
+
+.Lcopy_unaligned_done:
+
+ /* For memcpy return original dest address, else zero. */
+ { mz r0, r29, r23; jrp lr }
+
+.Lend_memcpy_common:
+ .size memcpy_common, .Lend_memcpy_common - memcpy_common
+
+ .section .fixup,"ax"
+memcpy_common_fixup:
+ .type memcpy_common_fixup, @function
+
+ /* Skip any bytes we already successfully copied.
+ * r2 (num remaining) is correct, but r0 (dst) and r1 (src)
+ * may not be quite right because of unrolling and prefetching.
+ * So we need to recompute their values as the address just
+ * after the last byte we are sure was successfully loaded and
+ * then stored.
+ */
+
+ /* Determine how many bytes we successfully copied. */
+ { sub r3, r25, r2 }
+
+ /* Add this to the original r0 and r1 to get their new values. */
+ { add r0, r23, r3; add r1, r24, r3 }
+
+ { bzt r29, memcpy_fixup_loop }
+ { blzt r29, copy_to_user_fixup_loop }
+
+copy_from_user_fixup_loop:
+ /* Try copying the rest one byte at a time, expecting a load fault. */
+.Lcfu: { lb_u r3, r1; addi r1, r1, 1 }
+ { sb r0, r3; addi r0, r0, 1; addi r2, r2, -1 }
+ { bnzt r2, copy_from_user_fixup_loop }
+
+.Lcopy_from_user_fixup_zero_remainder:
+ { bbs r29, 2f } /* low bit set means IS_COPY_FROM_USER */
+ /* byte-at-a-time loop faulted, so zero the rest. */
+ { move r3, r2; bz r2, 2f /* should be impossible, but handle it. */ }
+1: { sb r0, zero; addi r0, r0, 1; addi r3, r3, -1 }
+ { bnzt r3, 1b }
+2: move lr, r27
+ { move r0, r2; jrp lr }
+
+copy_to_user_fixup_loop:
+ /* Try copying the rest one byte at a time, expecting a store fault. */
+ { lb_u r3, r1; addi r1, r1, 1 }
+.Lctu: { sb r0, r3; addi r0, r0, 1; addi r2, r2, -1 }
+ { bnzt r2, copy_to_user_fixup_loop }
+.Lcopy_to_user_fixup_done:
+ move lr, r27
+ { move r0, r2; jrp lr }
+
+memcpy_fixup_loop:
+ /* Try copying the rest one byte at a time. We expect a disastrous
+ * fault to happen since we are in fixup code, but let it happen.
+ */
+ { lb_u r3, r1; addi r1, r1, 1 }
+ { sb r0, r3; addi r0, r0, 1; addi r2, r2, -1 }
+ { bnzt r2, memcpy_fixup_loop }
+ /* This should be unreachable, we should have faulted again.
+ * But be paranoid and handle it in case some interrupt changed
+ * the TLB or something.
+ */
+ move lr, r27
+ { move r0, r23; jrp lr }
+
+ .size memcpy_common_fixup, . - memcpy_common_fixup
+
+ .section __ex_table,"a"
+ .word .Lcfu, .Lcopy_from_user_fixup_zero_remainder
+ .word .Lctu, .Lcopy_to_user_fixup_done