shuffler: correctly handle one-to-many relationships

One-to-many relationships, in which one chunk of a file is used in
more than one place, tends to naturally show up in decoding certain
fileformats, including (but not limited to) Microsoft SDI.  Make the
shuffler library handle those cases correctly, and remove a
special-purpose hack in sdi.c.

This is based on the observation that all one-to-many relationships
can be treated as a one-to-one shuffle followed by
destination-to-destination copies; i.e. one copy is (arbitrarily)
assigned the "master copy" status, and all aliases are then copied
from the master copy when the master copy is already in its final
place.  All other copies can then be simply ignored for the duration
of the shuffle, just as zero-memory is.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/com32/lib/syslinux/movebits.c b/com32/lib/syslinux/movebits.c
index 5e4a0c3..1114bfb 100644 (file)
--- a/com32/lib/syslinux/movebits.c
+++ b/com32/lib/syslinux/movebits.c
@@ -1,6 +1,7 @@
 /* ----------------------------------------------------------------------- *
  *
  *   Copyright 2007-2008 H. Peter Anvin - All Rights Reserved
+ *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
  *
  *   Permission is hereby granted, free of charge, to any person
  *   obtaining a copy of this software and associated documentation
@@ -43,6 +44,8 @@
 #include <stdlib.h>
 #include <inttypes.h>
 #include <setjmp.h>
+#include <minmax.h>
+#include <stdbool.h>
 
 #include <syslinux/movebits.h>
 
@@ -61,9 +64,6 @@
 # define dprintf(...) ((void)0)
 #endif
 
-#define min(x,y) ((x) < (y) ? (x) : (y))
-#define max(x,y) ((x) > (y) ? (x) : (y))
-
 static jmp_buf new_movelist_bail;
 
 static struct syslinux_movelist *
@@ -230,6 +230,97 @@ allocate_from(struct syslinux_memmap **mmap, addr_t start, addr_t len)
 }
 
 /*
+ * Find chunks of a movelist which are one-to-many (one source, multiple
+ * destinations.)  Those chunks can get turned into post-shuffle copies,
+ * to avoid confusing the shuffler.
+ */
+static void shuffle_dealias(struct syslinux_movelist **fraglist,
+                           struct syslinux_movelist **postcopy)
+{
+  struct syslinux_movelist *mp, **mpp, *mx, *np;
+  addr_t ps, pe, xs, xe, delta;
+  bool advance;
+
+#if DEBUG
+  dprintf("Before alias resolution:\n");
+  syslinux_dump_movelist(stdout, *fraglist);
+#endif
+
+  *postcopy = NULL;
+
+  /*
+   * Note: as written, this is an O(n^2) algorithm; by producing a list
+   * sorted by destination address we could reduce it to O(n log n).
+   */
+  mpp = fraglist;
+  while ((mp = *mpp)) {
+    dprintf("mp -> (%#x,%#x,%#x)\n", mp->dst, mp->src, mp->len);
+    ps = mp->src;
+    pe = mp->src + mp->len - 1;
+    for (mx = *fraglist; mx != mp; mx = mx->next) {
+      dprintf("mx -> (%#x,%#x,%#x)\n", mx->dst, mx->src, mx->len);
+      /*
+       * If there is any overlap between mx and mp, mp should be
+       * modified and possibly split.
+       */
+      xs = mx->src;
+      xe = mx->src + mx->len - 1;
+
+      dprintf("?: %#x..%#x (inside %#x..%#x)\n", ps, pe, xs, xe);
+
+      if (pe <= xs || ps >= xe)
+       continue;               /* No overlap */
+
+      advance = false;
+      *mpp = mp->next;         /* Remove from list */
+
+      if (pe > xe) {
+       delta = pe-xe;
+       np = new_movelist(mp->dst+mp->len-delta, mp->src+mp->len-delta, delta);
+       mp->len -= delta; pe = xe;
+       np->next = *mpp;
+       *mpp = np;
+       advance = true;
+      }
+      if (ps < xs) {
+       delta = xs-ps;
+       np = new_movelist(mp->dst, ps, delta);
+       mp->src += delta; ps = mp->src;
+       mp->dst += delta;
+       mp->len -= delta;
+       np->next = *mpp;
+       *mpp = np;
+       advance = true;
+      }
+
+      assert(ps >= xs && pe <= xe);
+
+      dprintf("Overlap: %#x..%#x (inside %#x..%#x)\n", ps, pe, xs, xe);
+
+      mp->src = mx->dst + (ps-xs);
+      mp->next = *postcopy;
+      *postcopy = mp;
+
+      mp = *mpp;
+      
+      if (!advance)
+       goto restart;
+    }
+  
+    mpp = &mp->next;
+  restart:
+    ;
+  }
+
+#if DEBUG
+  dprintf("After alias resolution:\n");
+  syslinux_dump_movelist(stdout, *fraglist);
+  dprintf("Post-shuffle copies:\n");
+  syslinux_dump_movelist(stdout, *postcopy);
+#endif
+}
+
+/*
  * The code to actually emit moving of a chunk into its final place.
  */
 static void
@@ -304,7 +395,6 @@ move_chunk(struct syslinux_movelist ***moves,
  * moves is computed from "frags" and "freemem".  "space" lists
  * free memory areas at our disposal, and is (src, cnt) only.
  */
-
 int
 syslinux_compute_movelist(struct syslinux_movelist **moves,
                          struct syslinux_movelist *ifrags,
@@ -313,6 +403,7 @@ syslinux_compute_movelist(struct syslinux_movelist **moves,
   struct syslinux_memmap *mmap = NULL;
   const struct syslinux_memmap *mm, *ep;
   struct syslinux_movelist *frags = NULL;
+  struct syslinux_movelist *postcopy = NULL;
   struct syslinux_movelist *mv;
   struct syslinux_movelist *f, **fp;
   struct syslinux_movelist *o, **op;
@@ -342,6 +433,9 @@ syslinux_compute_movelist(struct syslinux_movelist **moves,
 
   frags = dup_movelist(ifrags);
 
+  /* Process one-to-many conditions */
+  shuffle_dealias(&frags, &postcopy);
+
   for (mm = memmap; mm->type != SMT_END; mm = mm->next)
     add_freelist(&mmap, mm->start, mm->next->start - mm->start,
                 mm->type == SMT_ZERO ? SMT_FREE : mm->type);
@@ -540,12 +634,20 @@ syslinux_compute_movelist(struct syslinux_movelist **moves,
     move_chunk(&moves, &mmap, fp, copylen);
   }
 
+  /* Finally, append the postcopy chain to the end of the moves list */
+  for (op = moves; (o = *op); op = &o->next)
+    ;                          /* Locate the end of the list */
+  *op = postcopy;
+  postcopy = NULL;
+
   rv = 0;
  bail:
   if (mmap)
     syslinux_free_memmap(mmap);
   if (frags)
     free_movelist(&frags);
+  if (postcopy)
+    free_movelist(&postcopy);
   return rv;
 }
 
@@ -559,32 +661,42 @@ int main(int argc, char *argv[])
   unsigned long d, s, l;
   struct syslinux_movelist *frags;
   struct syslinux_movelist **fep = &frags;
-  struct syslinux_movelist *space;
-  struct syslinux_movelist **sep = &space;
   struct syslinux_movelist *mv, *moves;
+  struct syslinux_memmap *memmap;
+
+  (void)argc;
+
+  memmap = syslinux_init_memmap();
 
   f = fopen(argv[1], "r");
-  while ( fscanf(f, "%lx %lx %lx", &d, &s, &l) == 3 ) {
+  while ( fscanf(f, "%lx %lx %lx", &s, &d, &l) == 3 ) {
     if ( d ) {
-      mv = new_movelist(d, s, l);
-      *fep = mv;
-      fep = &mv->next;
+      if (s == -1UL) {
+       syslinux_add_memmap(&memmap, d, l, SMT_ZERO);
+      } else {
+       mv = new_movelist(d, s, l);
+       *fep = mv;
+       fep = &mv->next;
+      }
     } else {
-      mv = new_movelist(0, s, l);
-      *sep = mv;
-      sep = &mv->next;
+      syslinux_add_memmap(&memmap, s, l, SMT_FREE);
     }
   }
   fclose(f);
 
-  if ( syslinux_compute_movelist(&moves, frags, space) ) {
+  *fep = NULL;
+
+  printf("Input move list:\n");
+  syslinux_dump_movelist(stdout, frags);
+  printf("Input free list:\n");
+  syslinux_dump_memmap(stdout, memmap);
+
+  if ( syslinux_compute_movelist(&moves, frags, memmap) ) {
     printf("Failed to compute a move sequence\n");
     return 1;
   } else {
-    for ( mv = moves ; mv ; mv = mv->next ) {
-      printf("0x%08x bytes at 0x%08x -> 0x%08x\n",
-            mv->len, mv->src, mv->dst);
-    }
+    printf("Final move list:\n");
+    syslinux_dump_movelist(stdout, moves);
     return 0;
   }
  }

diff --git a/com32/modules/sdi.c b/com32/modules/sdi.c
index 7c89859..a5df4da 100644 (file)
--- a/com32/modules/sdi.c
+++ b/com32/modules/sdi.c
@@ -1,6 +1,7 @@
 /* ----------------------------------------------------------------------- *
  *
  *   Copyright 2008 H. Peter Anvin - All Rights Reserved
+ *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -116,14 +117,8 @@ static int boot_sdi(void *ptr, size_t len)
   }
   if (syslinux_add_memmap(&amap, 0x7c00, hdr->BootCodeSize, SMT_ALLOC))
     goto bail;
-
-  /* The shuffle library doesn't handle duplication well... */
-  boot_blob = malloc(hdr->BootCodeSize);
-  if (!boot_blob)
-    goto bail;
-  memcpy(boot_blob, (char *)ptr + hdr->BootCodeOffset, hdr->BootCodeSize);
-
-  if (syslinux_add_movelist(&ml, 0x7c00, (addr_t)boot_blob, hdr->BootCodeSize))
+  if (syslinux_add_movelist(&ml, 0x7c00, (addr_t)ptr + hdr->BootCodeOffset,
+                           hdr->BootCodeSize))
     goto bail;
 
   /* **** Map the entire image to SDI_LOAD_ADDR **** */