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!

1 files changed, 209 insertions, 0 deletions

diff --git a/arch/ia64/lib/clear_user.S b/arch/ia64/lib/clear_user.S
new file mode 100644
index 000000000000..eecd8577b209
--- /dev/null
+++ b/arch/ia64/lib/clear_user.S
@@ -0,0 +1,209 @@
+/*
+ * This routine clears to zero a linear memory buffer in user space.
+ *
+ * Inputs:
+ *      in0:    address of buffer
+ *      in1:    length of buffer in bytes
+ * Outputs:
+ *      r8:     number of bytes that didn't get cleared due to a fault
+ *
+ * Copyright (C) 1998, 1999, 2001 Hewlett-Packard Co
+ *      Stephane Eranian <eranian@hpl.hp.com>
+ */
+
+#include <asm/asmmacro.h>
+
+//
+// arguments
+//
+#define buf             r32
+#define len             r33
+
+//
+// local registers
+//
+#define cnt             r16
+#define buf2            r17
+#define saved_lc        r18
+#define saved_pfs       r19
+#define tmp             r20
+#define len2            r21
+#define len3            r22
+
+//
+// Theory of operations:
+//      - we check whether or not the buffer is small, i.e., less than 17
+//        in which case we do the byte by byte loop.
+//
+//      - Otherwise we go progressively from 1 byte store to 8byte store in
+//        the head part, the body is a 16byte store loop and we finish we the
+//        tail for the last 15 bytes.
+//        The good point about this breakdown is that the long buffer handling
+//        contains only 2 branches.
+//
+//      The reason for not using shifting & masking for both the head and the
+//      tail is to stay semantically correct. This routine is not supposed
+//      to write bytes outside of the buffer. While most of the time this would
+//      be ok, we can't tolerate a mistake. A classical example is the case
+//      of multithreaded code were to the extra bytes touched is actually owned
+//      by another thread which runs concurrently to ours. Another, less likely,
+//      example is with device drivers where reading an I/O mapped location may
+//      have side effects (same thing for writing).
+//
+
+GLOBAL_ENTRY(__do_clear_user)
+        .prologue
+        .save ar.pfs, saved_pfs
+        alloc   saved_pfs=ar.pfs,2,0,0,0
+        cmp.eq p6,p0=r0,len             // check for zero length
+        .save ar.lc, saved_lc
+        mov saved_lc=ar.lc              // preserve ar.lc (slow)
+        .body
+        ;;                              // avoid WAW on CFM
+        adds tmp=-1,len                 // br.ctop is repeat/until
+        mov ret0=len                    // return value is length at this point
+(p6)    br.ret.spnt.many rp
+        ;;
+        cmp.lt p6,p0=16,len             // if len > 16 then long memset
+        mov ar.lc=tmp                   // initialize lc for small count
+(p6)    br.cond.dptk .long_do_clear
+        ;;                              // WAR on ar.lc
+        //
+        // worst case 16 iterations, avg 8 iterations
+        //
+        // We could have played with the predicates to use the extra
+        // M slot for 2 stores/iteration but the cost the initialization
+        // the various counters compared to how long the loop is supposed
+        // to last on average does not make this solution viable.
+        //
+1:
+        EX( .Lexit1, st1 [buf]=r0,1 )
+        adds len=-1,len                 // countdown length using len
+        br.cloop.dptk 1b
+        ;;                              // avoid RAW on ar.lc
+        //
+        // .Lexit4: comes from byte by byte loop
+        //          len contains bytes left
+.Lexit1:
+        mov ret0=len                    // faster than using ar.lc
+        mov ar.lc=saved_lc
+        br.ret.sptk.many rp             // end of short clear_user
+
+
+        //
+        // At this point we know we have more than 16 bytes to copy
+        // so we focus on alignment (no branches required)
+        //
+        // The use of len/len2 for countdown of the number of bytes left
+        // instead of ret0 is due to the fact that the exception code
+        // changes the values of r8.
+        //
+.long_do_clear:
+        tbit.nz p6,p0=buf,0             // odd alignment (for long_do_clear)
+        ;;
+        EX( .Lexit3, (p6) st1 [buf]=r0,1 )      // 1-byte aligned
+(p6)    adds len=-1,len;;               // sync because buf is modified
+        tbit.nz p6,p0=buf,1
+        ;;
+        EX( .Lexit3, (p6) st2 [buf]=r0,2 )      // 2-byte aligned
+(p6)    adds len=-2,len;;
+        tbit.nz p6,p0=buf,2
+        ;;
+        EX( .Lexit3, (p6) st4 [buf]=r0,4 )      // 4-byte aligned
+(p6)    adds len=-4,len;;
+        tbit.nz p6,p0=buf,3
+        ;;
+        EX( .Lexit3, (p6) st8 [buf]=r0,8 )      // 8-byte aligned
+(p6)    adds len=-8,len;;
+        shr.u cnt=len,4         // number of 128-bit (2x64bit) words
+        ;;
+        cmp.eq p6,p0=r0,cnt
+        adds tmp=-1,cnt
+(p6)    br.cond.dpnt .dotail            // we have less than 16 bytes left
+        ;;
+        adds buf2=8,buf                 // setup second base pointer
+        mov ar.lc=tmp
+        ;;
+
+        //
+        // 16bytes/iteration core loop
+        //
+        // The second store can never generate a fault because
+        // we come into the loop only when we are 16-byte aligned.
+        // This means that if we cross a page then it will always be
+        // in the first store and never in the second.
+        //
+        //
+        // We need to keep track of the remaining length. A possible (optimistic)
+        // way would be to use ar.lc and derive how many byte were left by
+        // doing : left= 16*ar.lc + 16.  this would avoid the addition at
+        // every iteration.
+        // However we need to keep the synchronization point. A template
+        // M;;MB does not exist and thus we can keep the addition at no
+        // extra cycle cost (use a nop slot anyway). It also simplifies the
+        // (unlikely)  error recovery code
+        //
+
+2:      EX(.Lexit3, st8 [buf]=r0,16 )
+        ;;                              // needed to get len correct when error
+        st8 [buf2]=r0,16
+        adds len=-16,len
+        br.cloop.dptk 2b
+        ;;
+        mov ar.lc=saved_lc
+        //
+        // tail correction based on len only
+        //
+        // We alternate the use of len3,len2 to allow parallelism and correct
+        // error handling. We also reuse p6/p7 to return correct value.
+        // The addition of len2/len3 does not cost anything more compared to
+        // the regular memset as we had empty slots.
+        //
+.dotail:
+        mov len2=len                    // for parallelization of error handling
+        mov len3=len
+        tbit.nz p6,p0=len,3
+        ;;
+        EX( .Lexit2, (p6) st8 [buf]=r0,8 )      // at least 8 bytes
+(p6)    adds len3=-8,len2
+        tbit.nz p7,p6=len,2
+        ;;
+        EX( .Lexit2, (p7) st4 [buf]=r0,4 )      // at least 4 bytes
+(p7)    adds len2=-4,len3
+        tbit.nz p6,p7=len,1
+        ;;
+        EX( .Lexit2, (p6) st2 [buf]=r0,2 )      // at least 2 bytes
+(p6)    adds len3=-2,len2
+        tbit.nz p7,p6=len,0
+        ;;
+        EX( .Lexit2, (p7) st1 [buf]=r0 )        // only 1 byte left
+        mov ret0=r0                             // success
+        br.ret.sptk.many rp                     // end of most likely path
+
+        //
+        // Outlined error handling code
+        //
+
+        //
+        // .Lexit3: comes from core loop, need restore pr/lc
+        //          len contains bytes left
+        //
+        //
+        // .Lexit2:
+        //      if p6 -> coming from st8 or st2 : len2 contains what's left
+        //      if p7 -> coming from st4 or st1 : len3 contains what's left
+        // We must restore lc/pr even though might not have been used.
+.Lexit2:
+        .pred.rel "mutex", p6, p7
+(p6)    mov len=len2
+(p7)    mov len=len3
+        ;;
+        //
+        // .Lexit4: comes from head, need not restore pr/lc
+        //          len contains bytes left
+        //
+.Lexit3:
+        mov ret0=len
+        mov ar.lc=saved_lc
+        br.ret.sptk.many rp
+END(__do_clear_user)