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Diffstat (limited to 'arch/tile/lib/memcpy_32.S')
| -rw-r--r-- | arch/tile/lib/memcpy_32.S | 628 |
1 files changed, 628 insertions, 0 deletions
diff --git a/arch/tile/lib/memcpy_32.S b/arch/tile/lib/memcpy_32.S new file mode 100644 index 000000000000..f92984bf60ec --- /dev/null +++ b/arch/tile/lib/memcpy_32.S @@ -0,0 +1,628 @@ +/* + * 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> + +#if CHIP_HAS_WH64() || defined(MEMCPY_TEST_WH64) +#define MEMCPY_USE_WH64 +#endif + + +#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 } + +#ifdef MEMCPY_USE_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 } +#ifndef MEMCPY_USE_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 */ + +#ifdef MEMCPY_TEST_WH64 + /* Issue a fake wh64 that clobbers the destination words + * with random garbage, for testing. + */ + { movei r19, 64; crc32_32 r10, r2, r9 } +.Lwh64_test_loop: +EX: { sw r9, r10; addi r9, r9, 4; addi r19, r19, -4 } + { bnzt r19, .Lwh64_test_loop; crc32_32 r10, r10, r19 } +#elif 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) */ +#ifdef MEMCPY_USE_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 |