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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/alpha/lib/strncpy_from_user.S
downloadconfigs-2.6.12-rc2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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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