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Diffstat (limited to 'arch/alpha/lib/strncpy_from_user.S')
| -rw-r--r-- | arch/alpha/lib/strncpy_from_user.S | 339 |
1 files changed, 339 insertions, 0 deletions
diff --git a/arch/alpha/lib/strncpy_from_user.S b/arch/alpha/lib/strncpy_from_user.S new file mode 100644 index 000000000000..73ee21160ff7 --- /dev/null +++ b/arch/alpha/lib/strncpy_from_user.S @@ -0,0 +1,339 @@ +/* + * arch/alpha/lib/strncpy_from_user.S + * Contributed by Richard Henderson (rth@tamu.edu) + * + * Just like strncpy except in the return value: + * + * -EFAULT if an exception occurs before the terminator is copied. + * N if the buffer filled. + * + * Otherwise the length of the string is returned. + */ + + +#include <asm/errno.h> +#include <asm/regdef.h> + + +/* Allow an exception for an insn; exit if we get one. */ +#define EX(x,y...) \ + 99: x,##y; \ + .section __ex_table,"a"; \ + .long 99b - .; \ + lda $31, $exception-99b($0); \ + .previous + + + .set noat + .set noreorder + .text + + .globl __strncpy_from_user + .ent __strncpy_from_user + .frame $30, 0, $26 + .prologue 0 + + .align 3 +$aligned: + /* On entry to this basic block: + t0 == the first destination word for masking back in + t1 == the first source word. */ + + /* Create the 1st output word and detect 0's in the 1st input word. */ + lda t2, -1 # e1 : build a mask against false zero + mskqh t2, a1, t2 # e0 : detection in the src word + mskqh t1, a1, t3 # e0 : + ornot t1, t2, t2 # .. e1 : + mskql t0, a1, t0 # e0 : assemble the first output word + cmpbge zero, t2, t8 # .. e1 : bits set iff null found + or t0, t3, t0 # e0 : + beq a2, $a_eoc # .. e1 : + bne t8, $a_eos # .. e1 : + + /* On entry to this basic block: + t0 == a source word not containing a null. */ + +$a_loop: + stq_u t0, 0(a0) # e0 : + addq a0, 8, a0 # .. e1 : + EX( ldq_u t0, 0(a1) ) # e0 : + addq a1, 8, a1 # .. e1 : + subq a2, 1, a2 # e0 : + cmpbge zero, t0, t8 # .. e1 (stall) + beq a2, $a_eoc # e1 : + beq t8, $a_loop # e1 : + + /* Take care of the final (partial) word store. At this point + the end-of-count bit is set in t8 iff it applies. + + On entry to this basic block we have: + t0 == the source word containing the null + t8 == the cmpbge mask that found it. */ + +$a_eos: + negq t8, t12 # e0 : find low bit set + and t8, t12, t12 # e1 (stall) + + /* For the sake of the cache, don't read a destination word + if we're not going to need it. */ + and t12, 0x80, t6 # e0 : + bne t6, 1f # .. e1 (zdb) + + /* We're doing a partial word store and so need to combine + our source and original destination words. */ + ldq_u t1, 0(a0) # e0 : + subq t12, 1, t6 # .. e1 : + or t12, t6, t8 # e0 : + unop # + zapnot t0, t8, t0 # e0 : clear src bytes > null + zap t1, t8, t1 # .. e1 : clear dst bytes <= null + or t0, t1, t0 # e1 : + +1: stq_u t0, 0(a0) + br $finish_up + + /* Add the end-of-count bit to the eos detection bitmask. */ +$a_eoc: + or t10, t8, t8 + br $a_eos + + /*** The Function Entry Point ***/ + .align 3 +__strncpy_from_user: + mov a0, v0 # save the string start + beq a2, $zerolength + + /* Are source and destination co-aligned? */ + xor a0, a1, t1 # e0 : + and a0, 7, t0 # .. e1 : find dest misalignment + and t1, 7, t1 # e0 : + addq a2, t0, a2 # .. e1 : bias count by dest misalignment + subq a2, 1, a2 # e0 : + and a2, 7, t2 # e1 : + srl a2, 3, a2 # e0 : a2 = loop counter = (count - 1)/8 + addq zero, 1, t10 # .. e1 : + sll t10, t2, t10 # e0 : t10 = bitmask of last count byte + bne t1, $unaligned # .. e1 : + + /* We are co-aligned; take care of a partial first word. */ + + EX( ldq_u t1, 0(a1) ) # e0 : load first src word + addq a1, 8, a1 # .. e1 : + + beq t0, $aligned # avoid loading dest word if not needed + ldq_u t0, 0(a0) # e0 : + br $aligned # .. e1 : + + +/* The source and destination are not co-aligned. Align the destination + and cope. We have to be very careful about not reading too much and + causing a SEGV. */ + + .align 3 +$u_head: + /* We know just enough now to be able to assemble the first + full source word. We can still find a zero at the end of it + that prevents us from outputting the whole thing. + + On entry to this basic block: + t0 == the first dest word, unmasked + t1 == the shifted low bits of the first source word + t6 == bytemask that is -1 in dest word bytes */ + + EX( ldq_u t2, 8(a1) ) # e0 : load second src word + addq a1, 8, a1 # .. e1 : + mskql t0, a0, t0 # e0 : mask trailing garbage in dst + extqh t2, a1, t4 # e0 : + or t1, t4, t1 # e1 : first aligned src word complete + mskqh t1, a0, t1 # e0 : mask leading garbage in src + or t0, t1, t0 # e0 : first output word complete + or t0, t6, t6 # e1 : mask original data for zero test + cmpbge zero, t6, t8 # e0 : + beq a2, $u_eocfin # .. e1 : + bne t8, $u_final # e1 : + + lda t6, -1 # e1 : mask out the bits we have + mskql t6, a1, t6 # e0 : already seen + stq_u t0, 0(a0) # e0 : store first output word + or t6, t2, t2 # .. e1 : + cmpbge zero, t2, t8 # e0 : find nulls in second partial + addq a0, 8, a0 # .. e1 : + subq a2, 1, a2 # e0 : + bne t8, $u_late_head_exit # .. e1 : + + /* Finally, we've got all the stupid leading edge cases taken care + of and we can set up to enter the main loop. */ + + extql t2, a1, t1 # e0 : position hi-bits of lo word + EX( ldq_u t2, 8(a1) ) # .. e1 : read next high-order source word + addq a1, 8, a1 # e0 : + cmpbge zero, t2, t8 # e1 (stall) + beq a2, $u_eoc # e1 : + bne t8, $u_eos # e1 : + + /* Unaligned copy main loop. In order to avoid reading too much, + the loop is structured to detect zeros in aligned source words. + This has, unfortunately, effectively pulled half of a loop + iteration out into the head and half into the tail, but it does + prevent nastiness from accumulating in the very thing we want + to run as fast as possible. + + On entry to this basic block: + t1 == the shifted high-order bits from the previous source word + t2 == the unshifted current source word + + We further know that t2 does not contain a null terminator. */ + + .align 3 +$u_loop: + extqh t2, a1, t0 # e0 : extract high bits for current word + addq a1, 8, a1 # .. e1 : + extql t2, a1, t3 # e0 : extract low bits for next time + addq a0, 8, a0 # .. e1 : + or t0, t1, t0 # e0 : current dst word now complete + EX( ldq_u t2, 0(a1) ) # .. e1 : load high word for next time + stq_u t0, -8(a0) # e0 : save the current word + mov t3, t1 # .. e1 : + subq a2, 1, a2 # e0 : + cmpbge zero, t2, t8 # .. e1 : test new word for eos + beq a2, $u_eoc # e1 : + beq t8, $u_loop # e1 : + + /* We've found a zero somewhere in the source word we just read. + If it resides in the lower half, we have one (probably partial) + word to write out, and if it resides in the upper half, we + have one full and one partial word left to write out. + + On entry to this basic block: + t1 == the shifted high-order bits from the previous source word + t2 == the unshifted current source word. */ +$u_eos: + extqh t2, a1, t0 # e0 : + or t0, t1, t0 # e1 : first (partial) source word complete + + cmpbge zero, t0, t8 # e0 : is the null in this first bit? + bne t8, $u_final # .. e1 (zdb) + + stq_u t0, 0(a0) # e0 : the null was in the high-order bits + addq a0, 8, a0 # .. e1 : + subq a2, 1, a2 # e1 : + +$u_late_head_exit: + extql t2, a1, t0 # .. e0 : + cmpbge zero, t0, t8 # e0 : + or t8, t10, t6 # e1 : + cmoveq a2, t6, t8 # e0 : + nop # .. e1 : + + /* Take care of a final (probably partial) result word. + On entry to this basic block: + t0 == assembled source word + t8 == cmpbge mask that found the null. */ +$u_final: + negq t8, t6 # e0 : isolate low bit set + and t6, t8, t12 # e1 : + + and t12, 0x80, t6 # e0 : avoid dest word load if we can + bne t6, 1f # .. e1 (zdb) + + ldq_u t1, 0(a0) # e0 : + subq t12, 1, t6 # .. e1 : + or t6, t12, t8 # e0 : + zapnot t0, t8, t0 # .. e1 : kill source bytes > null + zap t1, t8, t1 # e0 : kill dest bytes <= null + or t0, t1, t0 # e1 : + +1: stq_u t0, 0(a0) # e0 : + br $finish_up + +$u_eoc: # end-of-count + extqh t2, a1, t0 + or t0, t1, t0 + cmpbge zero, t0, t8 + +$u_eocfin: # end-of-count, final word + or t10, t8, t8 + br $u_final + + /* Unaligned copy entry point. */ + .align 3 +$unaligned: + + EX( ldq_u t1, 0(a1) ) # e0 : load first source word + + and a0, 7, t4 # .. e1 : find dest misalignment + and a1, 7, t5 # e0 : find src misalignment + + /* Conditionally load the first destination word and a bytemask + with 0xff indicating that the destination byte is sacrosanct. */ + + mov zero, t0 # .. e1 : + mov zero, t6 # e0 : + beq t4, 1f # .. e1 : + ldq_u t0, 0(a0) # e0 : + lda t6, -1 # .. e1 : + mskql t6, a0, t6 # e0 : +1: + subq a1, t4, a1 # .. e1 : sub dest misalignment from src addr + + /* If source misalignment is larger than dest misalignment, we need + extra startup checks to avoid SEGV. */ + + cmplt t4, t5, t12 # e1 : + extql t1, a1, t1 # .. e0 : shift src into place + lda t2, -1 # e0 : for creating masks later + beq t12, $u_head # e1 : + + mskqh t2, t5, t2 # e0 : begin src byte validity mask + cmpbge zero, t1, t8 # .. e1 : is there a zero? + extql t2, a1, t2 # e0 : + or t8, t10, t5 # .. e1 : test for end-of-count too + cmpbge zero, t2, t3 # e0 : + cmoveq a2, t5, t8 # .. e1 : + andnot t8, t3, t8 # e0 : + beq t8, $u_head # .. e1 (zdb) + + /* At this point we've found a zero in the first partial word of + the source. We need to isolate the valid source data and mask + it into the original destination data. (Incidentally, we know + that we'll need at least one byte of that original dest word.) */ + + ldq_u t0, 0(a0) # e0 : + negq t8, t6 # .. e1 : build bitmask of bytes <= zero + mskqh t1, t4, t1 # e0 : + and t6, t8, t12 # .. e1 : + subq t12, 1, t6 # e0 : + or t6, t12, t8 # e1 : + + zapnot t2, t8, t2 # e0 : prepare source word; mirror changes + zapnot t1, t8, t1 # .. e1 : to source validity mask + + andnot t0, t2, t0 # e0 : zero place for source to reside + or t0, t1, t0 # e1 : and put it there + stq_u t0, 0(a0) # e0 : + +$finish_up: + zapnot t0, t12, t4 # was last byte written null? + cmovne t4, 1, t4 + + and t12, 0xf0, t3 # binary search for the address of the + and t12, 0xcc, t2 # last byte written + and t12, 0xaa, t1 + bic a0, 7, t0 + cmovne t3, 4, t3 + cmovne t2, 2, t2 + cmovne t1, 1, t1 + addq t0, t3, t0 + addq t1, t2, t1 + addq t0, t1, t0 + addq t0, t4, t0 # add one if we filled the buffer + + subq t0, v0, v0 # find string length + ret + +$zerolength: + clr v0 +$exception: + ret + + .end __strncpy_from_user |