diff options
Diffstat (limited to 'arch/mips/lib/memcpy.S')
| -rw-r--r-- | arch/mips/lib/memcpy.S | 508 |
1 files changed, 508 insertions, 0 deletions
diff --git a/arch/mips/lib/memcpy.S b/arch/mips/lib/memcpy.S new file mode 100644 index 000000000000..afa8eae18ff6 --- /dev/null +++ b/arch/mips/lib/memcpy.S @@ -0,0 +1,508 @@ +/* + * 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 + * + * Mnemonic names for arguments to memcpy/__copy_user + */ +#include <linux/config.h> +#include <asm/asm.h> +#include <asm/offset.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_MIPS64 +#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 + .set noat + +/* + * 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(memcpy) /* a0=dst a1=src a2=len */ + move v0, dst /* return value */ +__memcpy: +FEXPORT(__copy_user) + /* + * 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, copy_bytes_checklen + and t0, src, ADDRMASK + PREF( 0, 2*32(src) ) + PREF( 1, 2*32(dst) ) + bnez t1, dst_unaligned + nop + bnez t0, src_unaligned_dst_aligned + /* + * use delay slot for fall-through + * src and dst are aligned; need to compute rem + */ +both_aligned: + SRL t0, len, LOG_NBYTES+3 # +3 for 8 units/iter + beqz t0, cleanup_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), l_exc) +EXC( LOAD t1, UNIT(1)(src), l_exc_copy) +EXC( LOAD t2, UNIT(2)(src), l_exc_copy) +EXC( LOAD t3, UNIT(3)(src), l_exc_copy) + SUB len, len, 8*NBYTES +EXC( LOAD t4, UNIT(4)(src), l_exc_copy) +EXC( LOAD t7, UNIT(5)(src), l_exc_copy) +EXC( STORE t0, UNIT(0)(dst), s_exc_p8u) +EXC( STORE t1, UNIT(1)(dst), s_exc_p7u) +EXC( LOAD t0, UNIT(6)(src), l_exc_copy) +EXC( LOAD t1, UNIT(7)(src), l_exc_copy) + ADD src, src, 8*NBYTES + ADD dst, dst, 8*NBYTES +EXC( STORE t2, UNIT(-6)(dst), s_exc_p6u) +EXC( STORE t3, UNIT(-5)(dst), s_exc_p5u) +EXC( STORE t4, UNIT(-4)(dst), s_exc_p4u) +EXC( STORE t7, UNIT(-3)(dst), s_exc_p3u) +EXC( STORE t0, UNIT(-2)(dst), s_exc_p2u) +EXC( STORE t1, UNIT(-1)(dst), s_exc_p1u) + 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 + */ +cleanup_both_aligned: + beqz len, done + sltu t0, len, 4*NBYTES + bnez t0, less_than_4units + and rem, len, (NBYTES-1) # rem = len % NBYTES + /* + * len >= 4*NBYTES + */ +EXC( LOAD t0, UNIT(0)(src), l_exc) +EXC( LOAD t1, UNIT(1)(src), l_exc_copy) +EXC( LOAD t2, UNIT(2)(src), l_exc_copy) +EXC( LOAD t3, UNIT(3)(src), l_exc_copy) + SUB len, len, 4*NBYTES + ADD src, src, 4*NBYTES +EXC( STORE t0, UNIT(0)(dst), s_exc_p4u) +EXC( STORE t1, UNIT(1)(dst), s_exc_p3u) +EXC( STORE t2, UNIT(2)(dst), s_exc_p2u) +EXC( STORE t3, UNIT(3)(dst), s_exc_p1u) + beqz len, done + ADD dst, dst, 4*NBYTES +less_than_4units: + /* + * rem = len % NBYTES + */ + beq rem, len, copy_bytes + nop +1: +EXC( LOAD t0, 0(src), l_exc) + ADD src, src, NBYTES + SUB len, len, NBYTES +EXC( STORE t0, 0(dst), s_exc_p1u) + bne rem, len, 1b + ADD dst, dst, NBYTES + + /* + * 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, done + 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), l_exc) + SUB bits, bits, rem # bits = number of bits to discard + SHIFT_DISCARD t0, t0, bits +EXC( STREST t0, -1(t1), s_exc) + jr ra + move len, zero +dst_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), l_exc) + ADD t2, zero, NBYTES +EXC( LDREST t3, REST(0)(src), l_exc_copy) + SUB t2, t2, t1 # t2 = number of bytes copied + xor match, t0, t1 +EXC( STFIRST t3, FIRST(0)(dst), s_exc) + beq len, t2, done + SUB len, len, t2 + ADD dst, dst, t2 + beqz match, both_aligned + ADD src, src, t2 + +src_unaligned_dst_aligned: + SRL t0, len, LOG_NBYTES+2 # +2 for 4 units/iter + PREF( 0, 3*32(src) ) + beqz t0, cleanup_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), l_exc) +EXC( LDFIRST t1, FIRST(1)(src), l_exc_copy) + SUB len, len, 4*NBYTES +EXC( LDREST t0, REST(0)(src), l_exc_copy) +EXC( LDREST t1, REST(1)(src), l_exc_copy) +EXC( LDFIRST t2, FIRST(2)(src), l_exc_copy) +EXC( LDFIRST t3, FIRST(3)(src), l_exc_copy) +EXC( LDREST t2, REST(2)(src), l_exc_copy) +EXC( LDREST t3, REST(3)(src), l_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 +EXC( STORE t0, UNIT(0)(dst), s_exc_p4u) +EXC( STORE t1, UNIT(1)(dst), s_exc_p3u) +EXC( STORE t2, UNIT(2)(dst), s_exc_p2u) +EXC( STORE t3, UNIT(3)(dst), s_exc_p1u) + PREF( 1, 9*32(dst) ) # 1 is PREF_STORE (not streamed) + bne len, rem, 1b + ADD dst, dst, 4*NBYTES + +cleanup_src_unaligned: + beqz len, done + and rem, len, NBYTES-1 # rem = len % NBYTES + beq rem, len, copy_bytes + nop +1: +EXC( LDFIRST t0, FIRST(0)(src), l_exc) +EXC( LDREST t0, REST(0)(src), l_exc_copy) + ADD src, src, NBYTES + SUB len, len, NBYTES +EXC( STORE t0, 0(dst), s_exc_p1u) + bne len, rem, 1b + ADD dst, dst, NBYTES + +copy_bytes_checklen: + beqz len, done + nop +copy_bytes: + /* 0 < len < NBYTES */ +#define COPY_BYTE(N) \ +EXC( lb t0, N(src), l_exc); \ + SUB len, len, 1; \ + beqz len, done; \ +EXC( sb t0, N(dst), s_exc_p1) + + 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), l_exc) + SUB len, len, 1 + jr ra +EXC( sb t0, NBYTES-2(dst), s_exc_p1) +done: + jr ra + nop + END(memcpy) + +l_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), l_exc) + ADD src, src, 1 + sb t1, 0(dst) # can't fault -- we're copy_from_user + bne src, t0, 1b + ADD dst, dst, 1 +l_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 + /* + * Here's where we rely on src and dst being incremented in tandem, + * See (3) above. + * dst += (fault addr - src) to put dst at first byte to clear + */ + ADD dst, t0 # compute start address in a1 + SUB dst, src + /* + * Clear len bytes starting at dst. Can't call __bzero because it + * might modify len. An inefficient loop for these rare times... + */ + beqz len, done + SUB src, len, 1 +1: sb zero, 0(dst) + ADD dst, dst, 1 + bnez src, 1b + SUB src, src, 1 + jr ra + nop + + +#define SEXC(n) \ +s_exc_p ## n ## u: \ + jr ra; \ + ADD len, len, n*NBYTES + +SEXC(8) +SEXC(7) +SEXC(6) +SEXC(5) +SEXC(4) +SEXC(3) +SEXC(2) +SEXC(1) + +s_exc_p1: + jr ra + ADD len, len, 1 +s_exc: + jr ra + nop + + .align 5 +LEAF(memmove) + ADD t0, a0, a2 + ADD t1, a1, a2 + sltu t0, a1, t0 # dst + len <= src -> memcpy + sltu t1, a0, t1 # dst >= src + len -> memcpy + and t0, t1 + beqz t0, __memcpy + move v0, a0 /* return value */ + beqz a2, r_out + END(memmove) + + /* fall through to __rmemcpy */ +LEAF(__rmemcpy) /* a0=dst a1=src a2=len */ + sltu t0, a1, a0 + beqz t0, r_end_bytes_up # src >= dst + nop + ADD a0, a2 # dst = dst + len + ADD a1, a2 # src = src + len + +r_end_bytes: + lb t0, -1(a1) + SUB a2, a2, 0x1 + sb t0, -1(a0) + SUB a1, a1, 0x1 + bnez a2, r_end_bytes + SUB a0, a0, 0x1 + +r_out: + jr ra + move a2, zero + +r_end_bytes_up: + lb t0, (a1) + SUB a2, a2, 0x1 + sb t0, (a0) + ADD a1, a1, 0x1 + bnez a2, r_end_bytes_up + ADD a0, a0, 0x1 + + jr ra + move a2, zero + END(__rmemcpy) |