[PATCH] solib-aix5.c: Revise mapping search/allocation strategy

[Kevin Buettner <kevinb at cygnus dot com>]

I've just committed the patch below.

AIX5 has a /proc/PID/map file which may be used to obtain the
locations that the OS has mapped sections of executables and shared
objects which make up a process.  I had previously arranged to
determine which section belongs to which map entry based upon whether
the mapping was writable or not.  This seemed to work well until
recently.  It turns out that the mapping corresponding to .text and
the other executable sections will be marked writable if any of
these sections are marked writable.  As a consequence, we can end up
with two read/write mappings and no read-only mapping which caused the
old machinery to fail miserably.  (E.g, it wasn't possible to set a
breakpoint on main().)

The new approach dynamically allocates the ``mapping'' data structure
thus making it possible keep track of more than two map entries per
file.  The correct mapping to use when doing relocations (and other
operations) is determined by looking at the file offset instead of the
read/write or read-only attributes.

	* solib-aix5.c (enum maptype): Delete.
	(struct lm_info): Add new member ``nmappings''.  Make ``mapping''
	member a pointer instead of a statically sized array.
	(build_so_list_from_mapfile): Dynamically allocate ``mapping''
	array.
	(aix5_relocate_main_executable, aix5_relocate_section_addresses,
	aix5_find_global_pointer): Search for correct mapping to use
	based on file offset instead of knowledge of whether the section
	is read-only or read/write.
	(aix5_find_gate_addresses): Use the first mapping instead of
	the (now defunct) MT_READONLY mapping.

Index: solib-aix5.c
===================================================================
RCS file: /cvs/src/src/gdb/solib-aix5.c,v
retrieving revision 1.9
diff -u -p -r1.9 solib-aix5.c
--- solib-aix5.c	2001/03/27 10:03:41	1.9
+++ solib-aix5.c	2001/04/12 22:10:40
@@ -49,22 +49,17 @@
 
 /* Link map info to include in an allocated so_list entry */
 
-enum maptype {
-  MT_READONLY = 0,
-  MT_READWRITE = 1,
-  MT_LAST = 2
-};
-
 struct lm_info
   {
-    struct
+    int nmappings;		/* number of mappings */
+    struct lm_mapping
       {
 	CORE_ADDR addr;		/* base address */
 	CORE_ADDR size;		/* size of mapped object */
 	CORE_ADDR offset;	/* offset into mapped object */
 	long flags;		/* MA_ protection and attribute flags */
 	CORE_ADDR gp;		/* global pointer value */
-      } mapping[MT_LAST];
+      } *mapping;
       char *mapname;		/* name in /proc/pid/object */
       char *pathname;		/* full pathname to object */
       char *membername;		/* member name in archive file */
@@ -232,7 +227,7 @@ build_so_list_from_mapfile (int pid, lon
     {
       char *mapname, *pathname, *membername;
       struct so_list *sop;
-      enum maptype maptype;
+      int mapidx;
 
       if (prmap->pr_size == 0)
 	break;
@@ -288,12 +283,16 @@ build_so_list_from_mapfile (int pid, lon
 	  sos = sop;
 	}
 
-      maptype = (prmap->pr_mflags & MA_WRITE) ? MT_READWRITE : MT_READONLY;
-      sop->lm_info->mapping[maptype].addr = (CORE_ADDR) prmap->pr_vaddr;
-      sop->lm_info->mapping[maptype].size = prmap->pr_size;
-      sop->lm_info->mapping[maptype].offset = prmap->pr_off;
-      sop->lm_info->mapping[maptype].flags = prmap->pr_mflags;
-      sop->lm_info->mapping[maptype].gp = (CORE_ADDR) prmap->pr_gp;
+      mapidx = sop->lm_info->nmappings;
+      sop->lm_info->nmappings += 1;
+      sop->lm_info->mapping 
+	= xrealloc (sop->lm_info->mapping,
+	            sop->lm_info->nmappings * sizeof (struct lm_mapping));
+      sop->lm_info->mapping[mapidx].addr = (CORE_ADDR) prmap->pr_vaddr;
+      sop->lm_info->mapping[mapidx].size = prmap->pr_size;
+      sop->lm_info->mapping[mapidx].offset = prmap->pr_off;
+      sop->lm_info->mapping[mapidx].flags = prmap->pr_mflags;
+      sop->lm_info->mapping[mapidx].gp = (CORE_ADDR) prmap->pr_gp;
     }
 
   xfree (mapbuf);
@@ -596,24 +595,26 @@ aix5_relocate_main_executable (void)
 
   /* Iterate over the mappings in the main executable and compute
      the new offset value as appropriate.  */
-  for (i = 0; i < MT_LAST; i++)
+  for (i = 0; i < so->lm_info->nmappings; i++)
     {
       CORE_ADDR increment = 0;
       struct obj_section *sect;
       bfd *obfd = symfile_objfile->obfd;
+      struct lm_mapping *mapping = &so->lm_info->mapping[i];
 
       ALL_OBJFILE_OSECTIONS (symfile_objfile, sect)
 	{
 	  int flags = bfd_get_section_flags (obfd, sect->the_bfd_section);
 	  if (flags & SEC_ALLOC)
 	    {
-	      if (((so->lm_info->mapping[i].flags & MA_WRITE) == 0)
-		    == ((flags & SEC_READONLY) != 0))
+	      file_ptr filepos = sect->the_bfd_section->filepos;
+	      if (mapping->offset <= filepos
+	          && filepos <= mapping->offset + mapping->size)
 		{
 		  int idx = sect->the_bfd_section->index;
 
 		  if (increment == 0)
-		    increment = so->lm_info->mapping[i].addr
+		    increment = mapping->addr
 		      - (bfd_section_vma (obfd, sect->the_bfd_section) 
 		         & SECTMAPMASK);
 
@@ -694,12 +695,28 @@ aix5_relocate_section_addresses (struct 
                                  struct section_table *sec)
 {
   int flags = bfd_get_section_flags (sec->bfd, sec->the_bfd_section);
+  file_ptr filepos = sec->the_bfd_section->filepos;
 
   if (flags & SEC_ALLOC)
     {
-      int idx = (flags & SEC_READONLY) ? MT_READONLY : MT_READWRITE;
-      CORE_ADDR addr = so->lm_info->mapping[idx].addr;
+      int idx;
+      CORE_ADDR addr;
+
+      for (idx = 0; idx < so->lm_info->nmappings; idx++)
+	{
+	  struct lm_mapping *mapping = &so->lm_info->mapping[idx];
+	  if (mapping->offset <= filepos
+	      && filepos <= mapping->offset + mapping->size)
+	    break;
+	}
 
+      if (idx >= so->lm_info->nmappings)
+	internal_error (__FILE__, __LINE__,
+	  "aix_relocate_section_addresses: Can't find mapping for section %s",
+	  bfd_get_section_name (sec->bfd, sec->the_bfd_section));
+      
+      addr = so->lm_info->mapping[idx].addr;
+
       sec->addr += addr;
       sec->endaddr += addr;
     }
@@ -718,11 +735,27 @@ aix5_find_global_pointer (CORE_ADDR addr
 
   for (so = sos; so != NULL; so = so->next)
     {
-      if (so->lm_info->mapping[MT_READONLY].addr <= addr
-          && addr <= so->lm_info->mapping[MT_READONLY].addr
-	               + so->lm_info->mapping[MT_READONLY].size)
+      int idx;
+      for (idx = 0; idx < so->lm_info->nmappings; idx++)
+	if (so->lm_info->mapping[idx].addr <= addr
+	    && addr <= so->lm_info->mapping[idx].addr
+			 + so->lm_info->mapping[idx].size)
+	  {
+	    break;
+	  }
+
+      if (idx < so->lm_info->nmappings)
 	{
-	  global_pointer = so->lm_info->mapping[MT_READWRITE].gp;
+	  /* Look for a non-zero global pointer in the current set of
+	     mappings.  */
+	  for (idx = 0; idx < so->lm_info->nmappings; idx++)
+	    if (so->lm_info->mapping[idx].gp != 0)
+	      {
+		global_pointer = so->lm_info->mapping[idx].gp;
+		break;
+	      }
+	  /* Get out regardless of whether we found one or not.  Mappings
+	     don't overlap, so it would be pointless to continue.  */
 	  break;
 	}
     }
@@ -759,8 +792,8 @@ aix5_find_gate_addresses (CORE_ADDR *sta
      it'll be in the read-only (even though it's execute-only)
      mapping in the lm_info struct.  */
 
-  *start = so->lm_info->mapping[MT_READONLY].addr;
-  *end = *start + so->lm_info->mapping[MT_READONLY].size;
+  *start = so->lm_info->mapping[0].addr;
+  *end = *start + so->lm_info->mapping[0].size;
 
   /* Free up all the space we've allocated.  */
   do_cleanups (old_chain);