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-/*
- * 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