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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/clear_user.S
downloadconfigs-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.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/clear_user.S
+ * Contributed by Richard Henderson <rth@tamu.edu>
+ *
+ * Zero user space, handling exceptions as we go.
+ *
+ * We have to make sure that $0 is always up-to-date and contains the
+ * right "bytes left to zero" value (and that it is updated only _after_
+ * a successful copy). There is also some rather minor exception setup
+ * stuff.
+ *
+ * NOTE! This is not directly C-callable, because the calling semantics
+ * are different:
+ *
+ * Inputs:
+ * length in $0
+ * destination address in $6
+ * exception pointer in $7
+ * return address in $28 (exceptions expect it there)
+ *
+ * Outputs:
+ * bytes left to copy in $0
+ *
+ * Clobbers:
+ * $1,$2,$3,$4,$5,$6
+ */
+
+/* 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($31); \
+ .previous
+
+ .set noat
+ .set noreorder
+ .align 4
+
+ .globl __do_clear_user
+ .ent __do_clear_user
+ .frame $30, 0, $28
+ .prologue 0
+
+$loop:
+ and $1, 3, $4 # e0 :
+ beq $4, 1f # .. e1 :
+
+0: EX( stq_u $31, 0($6) ) # e0 : zero one word
+ subq $0, 8, $0 # .. e1 :
+ subq $4, 1, $4 # e0 :
+ addq $6, 8, $6 # .. e1 :
+ bne $4, 0b # e1 :
+ unop # :
+
+1: bic $1, 3, $1 # e0 :
+ beq $1, $tail # .. e1 :
+
+2: EX( stq_u $31, 0($6) ) # e0 : zero four words
+ subq $0, 8, $0 # .. e1 :
+ EX( stq_u $31, 8($6) ) # e0 :
+ subq $0, 8, $0 # .. e1 :
+ EX( stq_u $31, 16($6) ) # e0 :
+ subq $0, 8, $0 # .. e1 :
+ EX( stq_u $31, 24($6) ) # e0 :
+ subq $0, 8, $0 # .. e1 :
+ subq $1, 4, $1 # e0 :
+ addq $6, 32, $6 # .. e1 :
+ bne $1, 2b # e1 :
+
+$tail:
+ bne $2, 1f # e1 : is there a tail to do?
+ ret $31, ($28), 1 # .. e1 :
+
+1: EX( ldq_u $5, 0($6) ) # e0 :
+ clr $0 # .. e1 :
+ nop # e1 :
+ mskqh $5, $0, $5 # e0 :
+ EX( stq_u $5, 0($6) ) # e0 :
+ ret $31, ($28), 1 # .. e1 :
+
+__do_clear_user:
+ and $6, 7, $4 # e0 : find dest misalignment
+ beq $0, $zerolength # .. e1 :
+ addq $0, $4, $1 # e0 : bias counter
+ and $1, 7, $2 # e1 : number of bytes in tail
+ srl $1, 3, $1 # e0 :
+ beq $4, $loop # .. e1 :
+
+ EX( ldq_u $5, 0($6) ) # e0 : load dst word to mask back in
+ beq $1, $oneword # .. e1 : sub-word store?
+
+ mskql $5, $6, $5 # e0 : take care of misaligned head
+ addq $6, 8, $6 # .. e1 :
+ EX( stq_u $5, -8($6) ) # e0 :
+ addq $0, $4, $0 # .. e1 : bytes left -= 8 - misalignment
+ subq $1, 1, $1 # e0 :
+ subq $0, 8, $0 # .. e1 :
+ br $loop # e1 :
+ unop # :
+
+$oneword:
+ mskql $5, $6, $4 # e0 :
+ mskqh $5, $2, $5 # e0 :
+ or $5, $4, $5 # e1 :
+ EX( stq_u $5, 0($6) ) # e0 :
+ clr $0 # .. e1 :
+
+$zerolength:
+$exception:
+ ret $31, ($28), 1 # .. e1 :
+
+ .end __do_clear_user