Use index of first global symbol to speed up dwfl_module_addrsym search.

Cache the index of the first global symbol in the module's symbol table,
or -1 when unknown.  All symbols with local binding come first in the
symbol table before the global symbols.  Use this information to speed
up dwfl_module_addrsym search.

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 97caf0bc592a7af31ee405ef19ad23b6df9bf46f..0cfa462db1677ed47453ab5eec3aca7286fd595f 100644 (file)
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,13 @@
+2011-11-31  Mark Wielaard  <mjw@redhat.com>
+
+       * dwfl_module_addrsym.c (dwfl_module_addrsym): First search all
+       global symbols. Then only when that doesn't provide a match search
+       all local symbols too.
+       * dwfl_module_getdwarf.c (load_symtab): Take first_global int arg
+       and fill it in.
+       (find_symtab): Initialize mod->first_global and pass it to load_symtab.
+       * libdwfl/libdwflP.h (Dwfl_Module): Add first_global field.
+
 2011-11-31  Mark Wielaard  <mjw@redhat.com>
 
        * dwfl_module_addrsym.c (dwfl_module_addrsym): Only update

diff --git a/libdwfl/dwfl_module_addrsym.c b/libdwfl/dwfl_module_addrsym.c
index 41ff46541ecab6d2da741185371ed219fa8a139f..9ced0cfb9ee53fae6de8f96f2305a94603868879 100644 (file)
--- a/libdwfl/dwfl_module_addrsym.c
+++ b/libdwfl/dwfl_module_addrsym.c
@@ -1,5 +1,5 @@
 /* Find debugging and symbol information for a module in libdwfl.
-   Copyright (C) 2005-2010 Red Hat, Inc.
+   Copyright (C) 2005-2011 Red Hat, Inc.
    This file is part of Red Hat elfutils.
 
    Red Hat elfutils is free software; you can redistribute it and/or modify
@@ -105,69 +105,84 @@ dwfl_module_addrsym (Dwfl_Module *mod, GElf_Addr addr,
   GElf_Addr min_label = 0;
 
   /* Look through the symbol table for a matching symbol.  */
-  for (int i = 1; i < syments; ++i)
+  inline void search_table (int start, int end)
     {
-      GElf_Sym sym;
-      GElf_Word shndx;
-      const char *name = INTUSE(dwfl_module_getsym) (mod, i, &sym, &shndx);
-      if (name != NULL && name[0] != '\0'
-         && sym.st_shndx != SHN_UNDEF
-         && sym.st_value <= addr
-         && GELF_ST_TYPE (sym.st_info) != STT_SECTION
-         && GELF_ST_TYPE (sym.st_info) != STT_FILE
-         && GELF_ST_TYPE (sym.st_info) != STT_TLS)
+      for (int i = start; i < end; ++i)
        {
-         /* Even if we don't choose this symbol, its existence excludes
-            any sizeless symbol (assembly label) that is below its upper
-            bound.  */
-         if (sym.st_value + sym.st_size > min_label)
-           min_label = sym.st_value + sym.st_size;
-
-         if (sym.st_size == 0 || addr - sym.st_value < sym.st_size)
+         GElf_Sym sym;
+         GElf_Word shndx;
+         const char *name = INTUSE(dwfl_module_getsym) (mod, i, &sym, &shndx);
+         if (name != NULL && name[0] != '\0'
+             && sym.st_shndx != SHN_UNDEF
+             && sym.st_value <= addr
+             && GELF_ST_TYPE (sym.st_info) != STT_SECTION
+             && GELF_ST_TYPE (sym.st_info) != STT_FILE
+             && GELF_ST_TYPE (sym.st_info) != STT_TLS)
            {
-             /* This symbol is a better candidate than the current one
-                if it's closer to ADDR or is global when it was local.  */
-             if (closest_name == NULL
-                 || closest_sym->st_value < sym.st_value
-                 || (GELF_ST_BIND (closest_sym->st_info)
-                     < GELF_ST_BIND (sym.st_info)))
+             /* Even if we don't choose this symbol, its existence excludes
+                any sizeless symbol (assembly label) that is below its upper
+                bound.  */
+             if (sym.st_value + sym.st_size > min_label)
+               min_label = sym.st_value + sym.st_size;
+
+             if (sym.st_size == 0 || addr - sym.st_value < sym.st_size)
                {
-                 if (sym.st_size != 0)
+                 /* This symbol is a better candidate than the current one
+                    if it's closer to ADDR or is global when it was local.  */
+                 if (closest_name == NULL
+                     || closest_sym->st_value < sym.st_value
+                     || (GELF_ST_BIND (closest_sym->st_info)
+                         < GELF_ST_BIND (sym.st_info)))
+                   {
+                     if (sym.st_size != 0)
+                       {
+                         *closest_sym = sym;
+                         closest_shndx = shndx;
+                         closest_name = name;
+                       }
+                     else if (closest_name == NULL
+                              && sym.st_value >= min_label
+                              && same_section (&sym, shndx))
+                       {
+                         /* Handwritten assembly symbols sometimes have no
+                            st_size.  If no symbol with proper size includes
+                            the address, we'll use the closest one that is in
+                            the same section as ADDR.  */
+                         sizeless_sym = sym;
+                         sizeless_shndx = shndx;
+                         sizeless_name = name;
+                       }
+                   }
+                 /* When the beginning of its range is no closer,
+                    the end of its range might be.  But do not
+                    replace a global symbol with a local!  */
+                 else if (sym.st_size != 0
+                          && closest_sym->st_value == sym.st_value
+                          && closest_sym->st_size > sym.st_size
+                          && (GELF_ST_BIND (closest_sym->st_info)
+                              <= GELF_ST_BIND (sym.st_info)))
                    {
                      *closest_sym = sym;
                      closest_shndx = shndx;
                      closest_name = name;
                    }
-                 else if (closest_name == NULL
-                          && sym.st_value >= min_label
-                          && same_section (&sym, shndx))
-                   {
-                     /* Handwritten assembly symbols sometimes have no
-                        st_size.  If no symbol with proper size includes
-                        the address, we'll use the closest one that is in
-                        the same section as ADDR.  */
-                     sizeless_sym = sym;
-                     sizeless_shndx = shndx;
-                     sizeless_name = name;
-                   }
-               }
-             /* When the beginning of its range is no closer,
-                the end of its range might be.  But do not
-                replace a global symbol with a local!  */
-             else if (sym.st_size != 0
-                      && closest_sym->st_value == sym.st_value
-                      && closest_sym->st_size > sym.st_size
-                      && (GELF_ST_BIND (closest_sym->st_info)
-                          <= GELF_ST_BIND (sym.st_info)))
-               {
-                 *closest_sym = sym;
-                 closest_shndx = shndx;
-                 closest_name = name;
                }
            }
        }
     }
 
+  /* First go through global symbols.  mod->first_global is setup by
+     dwfl_module_getsymtab to the index of the first global symbol in
+     the module's symbol table, or -1 when unknown.  All symbols with
+     local binding come first in the symbol table, then all globals.  */
+  search_table (mod->first_global < 0 ? 1 : mod->first_global, syments);
+
+  /* If we found nothing searching the global symbols, then try the locals.
+     Unless we have a global sizeless symbol that matches exactly.  */
+  if (closest_name == NULL && mod->first_global > 1
+      && (sizeless_name == NULL || sizeless_sym.st_value != addr))
+    search_table (1, mod->first_global);
+
   /* If we found no proper sized symbol to use, fall back to the best
      candidate sizeless symbol we found, if any.  */
   if (closest_name == NULL

diff --git a/libdwfl/dwfl_module_getdwarf.c b/libdwfl/dwfl_module_getdwarf.c
index 9c6771311a7086b6decf07cefceaf7b611fb6994..14fcd550a39da899d9007d2fe8c943cc3364a31e 100644 (file)
--- a/libdwfl/dwfl_module_getdwarf.c
+++ b/libdwfl/dwfl_module_getdwarf.c
@@ -568,7 +568,7 @@ find_debuginfo (Dwfl_Module *mod)
 static Dwfl_Error
 load_symtab (struct dwfl_file *file, struct dwfl_file **symfile,
             Elf_Scn **symscn, Elf_Scn **xndxscn,
-            size_t *syments, GElf_Word *strshndx)
+            size_t *syments, int *first_global, GElf_Word *strshndx)
 {
   bool symtab = false;
   Elf_Scn *scn = NULL;
@@ -584,6 +584,7 @@ load_symtab (struct dwfl_file *file, struct dwfl_file **symfile,
            *symfile = file;
            *strshndx = shdr->sh_link;
            *syments = shdr->sh_size / shdr->sh_entsize;
+           *first_global = shdr->sh_info;
            if (*xndxscn != NULL)
              return DWFL_E_NOERROR;
            break;
@@ -844,11 +845,14 @@ find_symtab (Dwfl_Module *mod)
   if (mod->symerr != DWFL_E_NOERROR)
     return;
 
+  mod->first_global = -1; /* Unknown, unless explicitly set by load_symtab.  */
+
   /* First see if the main ELF file has the debugging information.  */
   Elf_Scn *symscn = NULL, *xndxscn = NULL;
   GElf_Word strshndx;
   mod->symerr = load_symtab (&mod->main, &mod->symfile, &symscn,
-                            &xndxscn, &mod->syments, &strshndx);
+                            &xndxscn, &mod->syments, &mod->first_global,
+                            &strshndx);
   switch (mod->symerr)
     {
     default:
@@ -867,7 +871,8 @@ find_symtab (Dwfl_Module *mod)
 
        case DWFL_E_NOERROR:
          mod->symerr = load_symtab (&mod->debug, &mod->symfile, &symscn,
-                                    &xndxscn, &mod->syments, &strshndx);
+                                    &xndxscn, &mod->syments,
+                                    &mod->first_global, &strshndx);
          break;
 
        case DWFL_E_CB:         /* The find_debuginfo hook failed.  */
@@ -906,7 +911,7 @@ find_symtab (Dwfl_Module *mod)
       return;
     }
 
-  /* Cache the data; MOD->syments was set above.  */
+  /* Cache the data; MOD->syments and MOD->first_global were set above.  */
 
   mod->symstrdata = elf_getdata (elf_getscn (mod->symfile->elf, strshndx),
                                 NULL);

diff --git a/libdwfl/libdwflP.h b/libdwfl/libdwflP.h
index 1f7532bf5695b8b0072eff5165b077c868c6bc63..bca82d2e4e4b90d387419e807f5f1ab4a1080cda 100644 (file)
--- a/libdwfl/libdwflP.h
+++ b/libdwfl/libdwflP.h
@@ -172,6 +172,7 @@ struct Dwfl_Module
   struct dwfl_file *symfile;   /* Either main or debug.  */
   Elf_Data *symdata;           /* Data in the ELF symbol table section.  */
   size_t syments;              /* sh_size / sh_entsize of that section.  */
+  int first_global;            /* Index of first global symbol of table.  */
   Elf_Data *symstrdata;                /* Data for its string table.  */
   Elf_Data *symxndxdata;       /* Data in the extended section index table. */