1 files changed, 129 insertions, 36 deletions

diff --git a/libctf/ctf-string.c b/libctf/ctf-string.c
index 27bd7c2..44cd447 100644
--- a/libctf/ctf-string.c
+++ b/libctf/ctf-string.c
@@ -20,13 +20,24 @@
 #include <ctf-impl.h>
 #include <string.h>
 
-/* Convert an encoded CTF string name into a pointer to a C string by looking
-  up the appropriate string table buffer and then adding the offset.  */
+/* Convert an encoded CTF string name into a pointer to a C string, using an
+  explicit internal strtab rather than the fp-based one.  */
 const char *
-ctf_strraw (ctf_file_t *fp, uint32_t name)
+ctf_strraw_explicit (ctf_file_t *fp, uint32_t name, ctf_strs_t *strtab)
 {
   ctf_strs_t *ctsp = &fp->ctf_str[CTF_NAME_STID (name)];
 
+  if ((CTF_NAME_STID (name) == CTF_STRTAB_0) && (strtab != NULL))
+    ctsp = strtab;
+
+  /* If this name is in the external strtab, and there is a synthetic strtab,
+     use it in preference.  */
+
+  if (CTF_NAME_STID (name) == CTF_STRTAB_1
+      && fp->ctf_syn_ext_strtab != NULL)
+    return ctf_dynhash_lookup (fp->ctf_syn_ext_strtab,
+			       (void *) (uintptr_t) name);
+
   if (ctsp->cts_strs != NULL && CTF_NAME_OFFSET (name) < ctsp->cts_len)
     return (ctsp->cts_strs + CTF_NAME_OFFSET (name));
 
@@ -34,6 +45,14 @@ ctf_strraw (ctf_file_t *fp, uint32_t name)
   return NULL;
 }
 
+/* Convert an encoded CTF string name into a pointer to a C string by looking
+  up the appropriate string table buffer and then adding the offset.  */
+const char *
+ctf_strraw (ctf_file_t *fp, uint32_t name)
+{
+  return ctf_strraw_explicit (fp, name, NULL);
+}
+
 /* Return a guaranteed-non-NULL pointer to the string with the given CTF
    name.  */
 const char *
@@ -88,11 +107,11 @@ ctf_str_free_atoms (ctf_file_t *fp)
   ctf_dynhash_destroy (fp->ctf_str_atoms);
 }
 
-/* Add a string to the atoms table and return it, or return an existing string
-   if present, copying the passed-in string.  Returns NULL only when out of
-   memory (and do not touch the passed-in string in that case).  Possibly
-   augment the ref list with the passed-in ref.  */
-static const char *
+/* Add a string to the atoms table, copying the passed-in string.  Return the
+   atom added. Return NULL only when out of memory (and do not touch the
+   passed-in string in that case).  Possibly augment the ref list with the
+   passed-in ref.  */
+static ctf_str_atom_t *
 ctf_str_add_ref_internal (ctf_file_t *fp, const char *str,
 			  int add_ref, uint32_t *ref)
 {
@@ -116,7 +135,7 @@ ctf_str_add_ref_internal (ctf_file_t *fp, const char *str,
 	  ctf_list_append (&atom->csa_refs, aref);
 	  fp->ctf_str_num_refs++;
 	}
-      return atom->csa_str;
+      return atom;
     }
 
   if ((atom = ctf_alloc (sizeof (struct ctf_str_atom))) == NULL)
@@ -136,7 +155,7 @@ ctf_str_add_ref_internal (ctf_file_t *fp, const char *str,
       ctf_list_append (&atom->csa_refs, aref);
       fp->ctf_str_num_refs++;
     }
-  return newstr;
+  return atom;
 
  oom:
   ctf_free (atom);
@@ -150,9 +169,48 @@ ctf_str_add_ref_internal (ctf_file_t *fp, const char *str,
 const char *
 ctf_str_add (ctf_file_t *fp, const char *str)
 {
-  if (str)
-    return ctf_str_add_ref_internal (fp, str, FALSE, 0);
-  return NULL;
+  ctf_str_atom_t *atom;
+  if (!str)
+    return NULL;
+
+  atom = ctf_str_add_ref_internal (fp, str, FALSE, 0);
+  if (!atom)
+    return NULL;
+
+  return atom->csa_str;
+}
+
+/* Like ctf_str_add(), but additionally augment the atom's refs list with the
+   passed-in ref, whether or not the string is already present.  There is no
+   attempt to deduplicate the refs list (but duplicates are harmless).  */
+const char *
+ctf_str_add_ref (ctf_file_t *fp, const char *str, uint32_t *ref)
+{
+  ctf_str_atom_t *atom;
+  if (!str)
+    return NULL;
+
+  atom = ctf_str_add_ref_internal (fp, str, TRUE, ref);
+  if (!atom)
+    return NULL;
+
+  return atom->csa_str;
+}
+
+/* Add an external strtab reference at OFFSET.  */
+const char *
+ctf_str_add_external (ctf_file_t *fp, const char *str, uint32_t offset)
+{
+  ctf_str_atom_t *atom;
+  if (!str)
+    return NULL;
+
+  atom = ctf_str_add_ref_internal (fp, str, FALSE, 0);
+  if (!atom)
+    return NULL;
+
+  atom->csa_offset = CTF_SET_STID (offset, CTF_STRTAB_1);
+  return atom->csa_str;
 }
 
 /* A ctf_dynhash_iter_remove() callback that removes atoms later than a given
@@ -173,17 +231,6 @@ ctf_str_rollback (ctf_file_t *fp, ctf_snapshot_id_t id)
   ctf_dynhash_iter_remove (fp->ctf_str_atoms, ctf_str_rollback_atom, &id);
 }
 
-/* Like ctf_str_add(), but additionally augment the atom's refs list with the
-   passed-in ref, whether or not the string is already present.  There is no
-   attempt to deduplicate the refs list (but duplicates are harmless).  */
-const char *
-ctf_str_add_ref (ctf_file_t *fp, const char *str, uint32_t *ref)
-{
-  if (str)
-    return ctf_str_add_ref_internal (fp, str, TRUE, ref);
-  return NULL;
-}
-
 /* An adaptor around ctf_purge_atom_refs.  */
 static void
 ctf_str_purge_one_atom_refs (void *key _libctf_unused_, void *value,
@@ -238,7 +285,11 @@ ctf_str_count_strtab (void *key _libctf_unused_, void *value,
   ctf_str_atom_t *atom = (ctf_str_atom_t *) value;
   ctf_strtab_write_state_t *s = (ctf_strtab_write_state_t *) arg;
 
-  s->strtab->cts_len += strlen (atom->csa_str) + 1;
+  /* We only factor in the length of items that have no offset:
+     other items are in the external strtab.  They still contribute to the
+     total count, though, because we still have to sort them.  */
+  if (!atom->csa_offset)
+    s->strtab->cts_len += strlen (atom->csa_str) + 1;
   s->strtab_count++;
 }
 
@@ -268,8 +319,10 @@ ctf_str_sort_strtab (const void *a, const void *b)
 }
 
 /* Write out and return a strtab containing all strings with recorded refs,
-   adjusting the refs to refer to the corresponding string.  The returned
-   strtab may be NULL on error.  */
+   adjusting the refs to refer to the corresponding string.  The returned strtab
+   may be NULL on error.  Also populate the synthetic strtab with mappings from
+   external strtab offsets to names, so we can look them up with ctf_strptr().
+   Only external strtab offsets with references are added.  */
 ctf_strs_writable_t
 ctf_str_write_strtab (ctf_file_t *fp)
 {
@@ -279,6 +332,7 @@ ctf_str_write_strtab (ctf_file_t *fp)
   ctf_strtab_write_state_t s;
   ctf_str_atom_t **sorttab;
   size_t i;
+  int any_external = 0;
 
   memset (&strtab, 0, sizeof (struct ctf_strs_writable));
   memset (&s, 0, sizeof (struct ctf_strtab_write_state));
@@ -300,7 +354,7 @@ ctf_str_write_strtab (ctf_file_t *fp)
   /* Sort the strtab.  Force the null string to be first.  */
   sorttab = calloc (s.strtab_count, sizeof (ctf_str_atom_t *));
   if (!sorttab)
-      return strtab;
+    goto oom;
 
   sorttab[0] = nullstr;
   s.i = 1;
@@ -312,19 +366,58 @@ ctf_str_write_strtab (ctf_file_t *fp)
 	 ctf_str_sort_strtab);
 
   if ((strtab.cts_strs = ctf_alloc (strtab.cts_len)) == NULL)
-    {
-      free (sorttab);
-      return strtab;
-    }
+    goto oom_sorttab;
+
+  if (!fp->ctf_syn_ext_strtab)
+    fp->ctf_syn_ext_strtab = ctf_dynhash_create (ctf_hash_integer,
+						 ctf_hash_eq_integer,
+						 NULL, NULL);
+  if (!fp->ctf_syn_ext_strtab)
+    goto oom_strtab;
 
-  /* Update the strtab, and all refs.  */
+  /* Update all refs: also update the strtab appropriately.  */
   for (i = 0; i < s.strtab_count; i++)
     {
-      strcpy (&strtab.cts_strs[cur_stroff], sorttab[i]->csa_str);
-      ctf_str_update_refs (sorttab[i], cur_stroff);
-      cur_stroff += strlen (sorttab[i]->csa_str) + 1;
+      if (sorttab[i]->csa_offset)
+	{
+	  /* External strtab entry: populate the synthetic external strtab.
+
+	     This is safe because you cannot ctf_rollback to before the point
+	     when a ctf_update is done, and the strtab is written at ctf_update
+	     time.  So any atoms we reference here are sure to stick around
+	     until ctf_file_close.  */
+
+	  any_external = 1;
+	  ctf_str_update_refs (sorttab[i], sorttab[i]->csa_offset);
+	  if (ctf_dynhash_insert (fp->ctf_syn_ext_strtab,
+				  (void *) (uintptr_t) sorttab[i]->csa_offset,
+				  (void *) sorttab[i]->csa_str) < 0)
+	    goto oom_strtab;
+	}
+      else
+	{
+	  /* Internal strtab entry: actually add to the string table.  */
+
+	  ctf_str_update_refs (sorttab[i], cur_stroff);
+	  strcpy (&strtab.cts_strs[cur_stroff], sorttab[i]->csa_str);
+	  cur_stroff += strlen (sorttab[i]->csa_str) + 1;
+	}
     }
   free (sorttab);
 
+  if (!any_external)
+    {
+      ctf_dynhash_destroy (fp->ctf_syn_ext_strtab);
+      fp->ctf_syn_ext_strtab = NULL;
+    }
+
+  return strtab;
+
+ oom_strtab:
+  free (strtab.cts_strs);
+  strtab.cts_strs = NULL;
+ oom_sorttab:
+  free (sorttab);
+ oom:
   return strtab;
 }