Fix memory handling in strxfrm_l [BZ #16009]

[Modified from the original email by Siddhesh Poyarekar]

This patch solves bug #16009 by implementing an additional path in
strxfrm that does not depend on caching the weight and rule indices.

In detail the following changed:

* The old main loop was factored out of strxfrm_l into the function
do_xfrm_cached to be able to alternativly use the non-caching version
do_xfrm.

* strxfrm_l allocates a a fixed size array on the stack. If this is not
sufficiant to store the weight and rule indices, the non-caching path is
taken. As the cache size is not dependent on the input there can be no
problems with integer overflows or stack allocations greater than
__MAX_ALLOCA_CUTOFF. Note that malloc-ing is not possible because the
definition of strxfrm does not allow an oom errorhandling.

* The uncached path determines the weight and rule index for every char
and for every pass again.

* Passing all the locale data array by array resulted in very long
parameter lists, so I introduced a structure that holds them.

* Checking for zero src string has been moved a bit upwards, it is
before the locale data initialization now.

* To verify that the non-caching path works correct I added a test run
to localedata/sort-test.sh & localedata/xfrm-test.c where all strings
are patched up with spaces so that they are too large for the caching path.

1 files changed, 394 insertions, 94 deletions

diff --git a/string/strxfrm_l.c b/string/strxfrm_l.c
index 98494470b6..921d1f76c4 100644
--- a/string/strxfrm_l.c
+++ b/string/strxfrm_l.c
@@ -40,9 +40,24 @@
 #define CONCAT(a,b) CONCAT1(a,b)
 #define CONCAT1(a,b) a##b
 
+/* Maximum string size that is calculated with cached indices.  Right now this
+   is an arbitrary value open to optimizations.  SMALL_STR_SIZE * 4 has to be
+   lower than __MAX_ALLOCA_CUTOFF.  Keep localedata/xfrm-test.c in sync.  */
+#define SMALL_STR_SIZE 4095
+
 #include "../locale/localeinfo.h"
 #include WEIGHT_H
 
+/* Group locale data for shorter parameter lists.  */
+typedef struct
+{
+  uint_fast32_t nrules;
+  unsigned char *rulesets;
+  USTRING_TYPE *weights;
+  int32_t *table;
+  USTRING_TYPE *extra;
+  int32_t *indirect;
+} locale_data_t;
 
 #ifndef WIDE_CHAR_VERSION
 
@@ -81,113 +96,325 @@ utf8_encode (char *buf, int val)
 }
 #endif
 
+/* Find next weight and rule index.  Inlined since called for every char.  */
+static __always_inline size_t
+find_idx (const USTRING_TYPE **us, int32_t *weight_idx,
+	  unsigned char *rule_idx, const locale_data_t *l_data, const int pass)
+{
+  int32_t tmp = findidx (l_data->table, l_data->indirect, l_data->extra, us,
+			 -1);
+  *rule_idx = tmp >> 24;
+  int32_t idx = tmp & 0xffffff;
+  size_t len = l_data->weights[idx++];
+
+  /* Skip over indices of previous levels.  */
+  for (int i = 0; i < pass; i++)
+    {
+      idx += len;
+      len = l_data->weights[idx++];
+    }
 
-size_t
-STRXFRM (STRING_TYPE *dest, const STRING_TYPE *src, size_t n, __locale_t l)
+  *weight_idx = idx;
+  return len;
+}
+
+static int
+find_position (const USTRING_TYPE *us, const locale_data_t *l_data,
+	       const int pass)
 {
-  struct __locale_data *current = l->__locales[LC_COLLATE];
-  uint_fast32_t nrules = current->values[_NL_ITEM_INDEX (_NL_COLLATE_NRULES)].word;
-  /* We don't assign the following values right away since it might be
-     unnecessary in case there are no rules.  */
-  const unsigned char *rulesets;
-  const int32_t *table;
-  const USTRING_TYPE *weights;
-  const USTRING_TYPE *extra;
-  const int32_t *indirect;
+  int32_t weight_idx;
+  unsigned char rule_idx;
+  const USTRING_TYPE *usrc = us;
+
+  find_idx (&usrc, &weight_idx, &rule_idx, l_data, pass);
+  return l_data->rulesets[rule_idx * l_data->nrules + pass] & sort_position;
+}
+
+/* Do the transformation.  */
+static size_t
+do_xfrm (const USTRING_TYPE *usrc, STRING_TYPE *dest, size_t n,
+	 const locale_data_t *l_data)
+{
+  int32_t weight_idx;
+  unsigned char rule_idx;
   uint_fast32_t pass;
-  size_t needed;
+  size_t needed = 0;
   size_t last_needed;
-  const USTRING_TYPE *usrc;
-  size_t srclen = STRLEN (src);
-  int32_t *idxarr;
-  unsigned char *rulearr;
-  size_t idxmax;
-  size_t idxcnt;
-  int use_malloc;
 
-  if (nrules == 0)
+  /* Now the passes over the weights.  */
+  for (pass = 0; pass < l_data->nrules; ++pass)
     {
-      if (n != 0)
-	STPNCPY (dest, src, MIN (srclen + 1, n));
+      size_t backw_len = 0;
+      last_needed = needed;
+      const USTRING_TYPE *cur = usrc;
+      const USTRING_TYPE *backw_start = NULL;
 
-      return srclen;
-    }
+       /* We assume that if a rule has defined `position' in one section
+         this is true for all of them.  */
+      int position = find_position (cur, l_data, pass);
 
-  rulesets = (const unsigned char *)
-    current->values[_NL_ITEM_INDEX (_NL_COLLATE_RULESETS)].string;
-  table = (const int32_t *)
-    current->values[_NL_ITEM_INDEX (CONCAT(_NL_COLLATE_TABLE,SUFFIX))].string;
-  weights = (const USTRING_TYPE *)
-    current->values[_NL_ITEM_INDEX (CONCAT(_NL_COLLATE_WEIGHT,SUFFIX))].string;
-  extra = (const USTRING_TYPE *)
-    current->values[_NL_ITEM_INDEX (CONCAT(_NL_COLLATE_EXTRA,SUFFIX))].string;
-  indirect = (const int32_t *)
-    current->values[_NL_ITEM_INDEX (CONCAT(_NL_COLLATE_INDIRECT,SUFFIX))].string;
-  use_malloc = 0;
+      if (position == 0)
+	{
+	  while (*cur != L('\0'))
+	    {
+	      const USTRING_TYPE *pos = cur;
+	      size_t len = find_idx (&cur, &weight_idx, &rule_idx, l_data,
+				     pass);
+	      int rule = l_data->rulesets[rule_idx * l_data->nrules + pass];
 
-  assert (((uintptr_t) table) % __alignof__ (table[0]) == 0);
-  assert (((uintptr_t) weights) % __alignof__ (weights[0]) == 0);
-  assert (((uintptr_t) extra) % __alignof__ (extra[0]) == 0);
-  assert (((uintptr_t) indirect) % __alignof__ (indirect[0]) == 0);
+	      if ((rule & sort_forward) != 0)
+		{
+		  /* Handle the pushed backward sequence.  */
+		  if (backw_start != NULL)
+		    {
+		      for (size_t i = backw_len; i > 0; )
+			{
+			  int32_t weight_idx;
+			  unsigned char rule_idx;
+			  size_t len = find_idx (&backw_start, &weight_idx,
+						 &rule_idx, l_data, pass);
+			  if (needed + i < n)
+			    for (size_t j = len; j > 0; j--)
+			      dest[needed + i - j] =
+				l_data->weights[weight_idx++];
+
+			  i -= len;
+			}
 
-  /* Handle an empty string as a special case.  */
-  if (srclen == 0)
-    {
-      if (n != 0)
-	*dest = L('\0');
-      return 0;
-    }
+		      needed += backw_len;
+		      backw_start = NULL;
+		      backw_len = 0;
+		    }
 
-  /* We need the elements of the string as unsigned values since they
-     are used as indeces.  */
-  usrc = (const USTRING_TYPE *) src;
-
-  /* Perform the first pass over the string and while doing this find
-     and store the weights for each character.  Since we want this to
-     be as fast as possible we are using `alloca' to store the temporary
-     values.  But since there is no limit on the length of the string
-     we have to use `malloc' if the string is too long.  We should be
-     very conservative here.  */
-  if (! __libc_use_alloca ((srclen + 1) * (sizeof (int32_t) + 1)))
-    {
-      idxarr = (int32_t *) malloc ((srclen + 1) * (sizeof (int32_t) + 1));
-      rulearr = (unsigned char *) &idxarr[srclen];
-
-      if (idxarr == NULL)
-	/* No memory.  Well, go with the stack then.
-
-	   XXX Once this implementation is stable we will handle this
-	   differently.  Instead of precomputing the indeces we will
-	   do this in time.  This means, though, that this happens for
-	   every pass again.  */
-	goto try_stack;
-      use_malloc = 1;
-    }
-  else
-    {
-    try_stack:
-      idxarr = (int32_t *) alloca (srclen * sizeof (int32_t));
-      rulearr = (unsigned char *) alloca (srclen + 1);
+		  /* Now handle the forward element.  */
+		  if (needed + len < n)
+		    while (len-- > 0)
+		      dest[needed++] = l_data->weights[weight_idx++];
+		  else
+		    /* No more characters fit into the buffer.  */
+		    needed += len;
+		}
+	      else
+		{
+		  /* Remember start of the backward sequence & track length.  */
+		  if (backw_start == NULL)
+		    backw_start = pos;
+		  backw_len += len;
+		}
+	    }
+
+
+	  /* Handle the pushed backward sequence.  */
+	  if (backw_start != NULL)
+	    {
+	      for (size_t i = backw_len; i > 0; )
+		{
+		  size_t len = find_idx (&backw_start, &weight_idx, &rule_idx,
+					 l_data, pass);
+		  if (needed + i < n)
+		    for (size_t j = len; j > 0; j--)
+		      dest[needed + i - j] =
+			l_data->weights[weight_idx++];
+
+		  i -= len;
+		}
+
+	      needed += backw_len;
+	    }
+	}
+      else
+	{
+	  int val = 1;
+#ifndef WIDE_CHAR_VERSION
+	  char buf[7];
+	  size_t buflen;
+#endif
+	  size_t i;
+
+	  while (*cur != L('\0'))
+	    {
+	      const USTRING_TYPE *pos = cur;
+	      size_t len = find_idx (&cur, &weight_idx, &rule_idx, l_data,
+				     pass);
+	      int rule = l_data->rulesets[rule_idx * l_data->nrules + pass];
+
+	      if ((rule & sort_forward) != 0)
+		{
+		  /* Handle the pushed backward sequence.  */
+		  if (backw_start != NULL)
+		    {
+		      for (size_t p = backw_len; p > 0; p--)
+			{
+			  size_t len;
+			  int32_t weight_idx;
+			  unsigned char rule_idx;
+			  const USTRING_TYPE *backw_cur = backw_start;
+
+			  /* To prevent a warning init the used vars.  */
+			  len = find_idx (&backw_cur, &weight_idx,
+					  &rule_idx, l_data, pass);
+
+			  for (i = 1; i < p; i++)
+			    len = find_idx (&backw_cur, &weight_idx,
+					    &rule_idx, l_data, pass);
+
+			  if (len != 0)
+			    {
+#ifdef WIDE_CHAR_VERSION
+			      if (needed + 1 + len < n)
+				{
+				  dest[needed] = val;
+				  for (i = 0; i < len; ++i)
+				    dest[needed + 1 + i] =
+				      l_data->weights[weight_idx + i];
+				}
+			      needed += 1 + len;
+#else
+			      buflen = utf8_encode (buf, val);
+			      if (needed + buflen + len < n)
+				{
+				  for (i = 0; i < buflen; ++i)
+				    dest[needed + i] = buf[i];
+				  for (i = 0; i < len; ++i)
+				    dest[needed + buflen + i] =
+				      l_data->weights[weight_idx + i];
+				}
+			      needed += buflen + len;
+#endif
+			      val = 1;
+			    }
+			  else
+			    ++val;
+			}
+
+		      backw_start = NULL;
+		      backw_len = 0;
+		    }
+
+		  /* Now handle the forward element.  */
+		  if (len != 0)
+		    {
+#ifdef WIDE_CHAR_VERSION
+		      if (needed + 1 + len < n)
+			{
+			  dest[needed] = val;
+			  for (i = 0; i < len; ++i)
+			    dest[needed + 1 + i] =
+			      l_data->weights[weight_idx + i];
+			}
+		      needed += 1 + len;
+#else
+		      buflen = utf8_encode (buf, val);
+		      if (needed + buflen + len < n)
+			{
+			  for (i = 0; i < buflen; ++i)
+			    dest[needed + i] = buf[i];
+			  for (i = 0; i < len; ++i)
+			    dest[needed + buflen + i] =
+			      l_data->weights[weight_idx + i];
+			}
+		      needed += buflen + len;
+#endif
+		      val = 1;
+		    }
+		  else
+		    ++val;
+		}
+	      else
+		{
+		  /* Remember start of the backward sequence & track length.  */
+		  if (backw_start == NULL)
+		    backw_start = pos;
+		  backw_len++;
+		}
+	    }
+
+	  /* Handle the pushed backward sequence.  */
+	  if (backw_start != NULL)
+	    {
+	      for (size_t p = backw_len; p > 0; p--)
+		{
+		  size_t len;
+		  int32_t weight_idx;
+		  unsigned char rule_idx;
+		  const USTRING_TYPE *backw_cur = backw_start;
+
+		  /* To prevent a warning init the used vars.  */
+		  len = find_idx (&backw_cur, &weight_idx,
+				  &rule_idx, l_data, pass);
+
+		  for (i = 1; i < p; i++)
+		    len = find_idx (&backw_cur, &weight_idx,
+				    &rule_idx, l_data, pass);
+
+		  if (len != 0)
+		    {
+#ifdef WIDE_CHAR_VERSION
+		      if (needed + 1 + len < n)
+			{
+			  dest[needed] = val;
+			  for (i = 0; i < len; ++i)
+			    dest[needed + 1 + i] =
+			      l_data->weights[weight_idx + i];
+			}
+		      needed += 1 + len;
+#else
+		      buflen = utf8_encode (buf, val);
+		      if (needed + buflen + len < n)
+			{
+			  for (i = 0; i < buflen; ++i)
+			    dest[needed + i] = buf[i];
+			  for (i = 0; i < len; ++i)
+			    dest[needed + buflen + i] =
+			      l_data->weights[weight_idx + i];
+			}
+		      needed += buflen + len;
+#endif
+		      val = 1;
+		    }
+		  else
+		    ++val;
+		}
+	    }
+	}
+
+      /* Finally store the byte to separate the passes or terminate
+	 the string.  */
+      if (needed < n)
+	dest[needed] = pass + 1 < l_data->nrules ? L('\1') : L('\0');
+      ++needed;
     }
 
-  idxmax = 0;
-  do
+  /* This is a little optimization: many collation specifications have
+     a `position' rule at the end and if no non-ignored character
+     is found the last \1 byte is immediately followed by a \0 byte
+     signalling this.  We can avoid the \1 byte(s).  */
+  if (needed > 2 && needed == last_needed + 1)
     {
-      int32_t tmp = findidx (table, indirect, extra, &usrc, -1);
-      rulearr[idxmax] = tmp >> 24;
-      idxarr[idxmax] = tmp & 0xffffff;
-
-      ++idxmax;
+      /* Remove the \1 byte.  */
+      if (--needed <= n)
+	dest[needed - 1] = L('\0');
     }
-  while (*usrc != L('\0'));
 
-  /* This element is only read, the value never used but to determine
-     another value which then is ignored.  */
-  rulearr[idxmax] = '\0';
+  /* Return the number of bytes/words we need, but don't count the NUL
+     byte/word at the end.  */
+  return needed - 1;
+}
+
+/* Do the transformation using weight-index and rule cache.  */
+static size_t
+do_xfrm_cached (STRING_TYPE *dest, size_t n, const locale_data_t *l_data,
+		size_t idxmax, int32_t *idxarr, const unsigned char *rulearr)
+{
+  uint_fast32_t nrules = l_data->nrules;
+  unsigned char *rulesets = l_data->rulesets;
+  USTRING_TYPE *weights = l_data->weights;
+  uint_fast32_t pass;
+  size_t needed = 0;
+  size_t last_needed;
+  size_t idxcnt;
 
-  /* Now the passes over the weights.  We now use the indeces we found
-     before.  */
-  needed = 0;
+  /* Now the passes over the weights.  */
   for (pass = 0; pass < nrules; ++pass)
     {
       size_t backw_stop = ~0ul;
@@ -433,14 +660,87 @@ STRXFRM (STRING_TYPE *dest, const STRING_TYPE *src, size_t n, __locale_t l)
 	dest[needed - 1] = L('\0');
     }
 
-  /* Free the memory if needed.  */
-  if (use_malloc)
-    free (idxarr);
-
   /* Return the number of bytes/words we need, but don't count the NUL
      byte/word at the end.  */
   return needed - 1;
 }
+
+size_t
+STRXFRM (STRING_TYPE *dest, const STRING_TYPE *src, size_t n, __locale_t l)
+{
+  locale_data_t l_data;
+  struct __locale_data *current = l->__locales[LC_COLLATE];
+  l_data.nrules = current->values[_NL_ITEM_INDEX (_NL_COLLATE_NRULES)].word;
+
+  /* Handle byte comparison case.  */
+  if (l_data.nrules == 0)
+    {
+      size_t srclen = STRLEN (src);
+
+      if (n != 0)
+	STPNCPY (dest, src, MIN (srclen + 1, n));
+
+      return srclen;
+    }
+
+  /* Handle an empty string, code hereafter relies on strlen (src) > 0.  */
+  if (*src == L('\0'))
+    {
+      if (n != 0)
+	*dest = L('\0');
+      return 0;
+    }
+
+  /* Get the locale data.  */
+  l_data.rulesets = (unsigned char *)
+    current->values[_NL_ITEM_INDEX (_NL_COLLATE_RULESETS)].string;
+  l_data.table = (int32_t *)
+    current->values[_NL_ITEM_INDEX (CONCAT(_NL_COLLATE_TABLE,SUFFIX))].string;
+  l_data.weights = (USTRING_TYPE *)
+    current->values[_NL_ITEM_INDEX (CONCAT(_NL_COLLATE_WEIGHT,SUFFIX))].string;
+  l_data.extra = (USTRING_TYPE *)
+    current->values[_NL_ITEM_INDEX (CONCAT(_NL_COLLATE_EXTRA,SUFFIX))].string;
+  l_data.indirect = (int32_t *)
+    current->values[_NL_ITEM_INDEX (CONCAT(_NL_COLLATE_INDIRECT,SUFFIX))].string;
+
+  assert (((uintptr_t) l_data.table) % __alignof__ (l_data.table[0]) == 0);
+  assert (((uintptr_t) l_data.weights) % __alignof__ (l_data.weights[0]) == 0);
+  assert (((uintptr_t) l_data.extra) % __alignof__ (l_data.extra[0]) == 0);
+  assert (((uintptr_t) l_data.indirect) % __alignof__ (l_data.indirect[0]) == 0);
+
+  /* We need the elements of the string as unsigned values since they
+     are used as indeces.  */
+  const USTRING_TYPE *usrc = (const USTRING_TYPE *) src;
+
+  /* Allocate cache for small strings on the stack and fill it with weight and
+     rule indices.  If the cache size is not sufficient, continue with the
+     uncached xfrm version.  */
+  size_t idxmax = 0;
+  const USTRING_TYPE *cur = usrc;
+  int32_t *idxarr = alloca (SMALL_STR_SIZE * sizeof (int32_t));
+  unsigned char *rulearr = alloca (SMALL_STR_SIZE + 1);
+
+  do
+    {
+      int32_t tmp = findidx (l_data.table, l_data.indirect, l_data.extra, &cur,
+			     -1);
+      rulearr[idxmax] = tmp >> 24;
+      idxarr[idxmax] = tmp & 0xffffff;
+
+      ++idxmax;
+    }
+  while (*cur != L('\0') && idxmax < SMALL_STR_SIZE);
+
+  /* This element is only read, the value never used but to determine
+     another value which then is ignored.  */
+  rulearr[idxmax] = '\0';
+
+  /* Do the transformation.  */
+  if (*cur == L('\0'))
+    return do_xfrm_cached (dest, n, &l_data, idxmax, idxarr, rulearr);
+  else
+    return do_xfrm (usrc, dest, n, &l_data);
+}
 libc_hidden_def (STRXFRM)
 
 #ifndef WIDE_CHAR_VERSION