/* * 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 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 lose 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 <variant/core.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