libdwfl: Add minisymtab support.

Add an auxiliary symbol table dwfl_file aux_sym to Dwfl_Module if all we
have is the dynsym table.  The main file might contain a .gnu_debugdata
section. The .gnu_debugdata section is a compressed embedded ELF file
that contains the text (code) section symbols from the symtab table
that are not in the main file dynsym table. dwfl_module_getsymtab (),
dwfl_module_addrsym () and dwfl_module_getsym () will use the auxiliary
symbol table when available (and no full symtab is available from the
debug file).

    * libdwflP.h (struct Dwfl_Module): Add aux_sym, aux_symdata,
    aux_syments, aux_symstrdata, aux_symxndxdata and aux_first_global.
    (dwfl_adjusted_aux_sym_addr): New function.
    (dwfl_deadjust_aux_sym_addr): Likewise.
    (dwfl_adjusted_st_value): Take and check symfile argument.
    (dwfl_deadjust_st_value): Likewise.
    * dwfl_module_getdwarf.c (find_prelink_address_sync): Take and
    use dwfl_file as argument to set address_sync.
    (find_debuginfo): Call find_prelink_address_sync with debug file.
    (find_aux_sym): New function.
    (find_symtab): Use find_aux_sym if all we have is the dynsym table
    and fill in aux DwflModule fields.
    (dwfl_module_getsymtab): Return syments plus aux_syments.
    (load_symtab): Always set first_global.
    * dwfl_module_addrsym.c (dwfl_module_addrsym): Check symfile
    when using same_section. Calculate first_global based on both
    mod->first_global and mod->aux_first_global.
    * dwfl_module.c (__libdwfl_module_free): Free aux_sym.
    * dwfl_module_getsym.c (dwfl_module_getsym): Use auxsym table
    to retrieve symbol and name if necessary, making sure all locals
    from any table come before any globals.
    * dwfl_module_info.c (dwfl_module_info): Call dwfl_adjusted_st_value
    with symfile.
    * relocate.c (resolve_symbol): Likewise.

https://fedoraproject.org/wiki/Features/MiniDebugInfo

Signed-off-by: Mark Wielaard <mjw@redhat.com>

1 files changed, 19 insertions, 12 deletions

diff --git a/libdwfl/dwfl_module_addrsym.c b/libdwfl/dwfl_module_addrsym.c
index fdc95fc0..d2059ea4 100644
--- 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) 2005-2011 Red Hat, Inc.
+   Copyright (C) 2005-2012 Red Hat, Inc.
    This file is part of elfutils.
 
    This file is free software; you can redistribute it and/or modify
@@ -41,7 +41,8 @@ dwfl_module_addrsym (Dwfl_Module *mod, GElf_Addr addr,
 
   /* Return true iff we consider ADDR to lie in the same section as SYM.  */
   GElf_Word addr_shndx = SHN_UNDEF;
-  inline bool same_section (const GElf_Sym *sym, GElf_Word shndx)
+  inline bool same_section (const GElf_Sym *sym, struct dwfl_file *symfile,
+			    GElf_Word shndx)
     {
       /* For absolute symbols and the like, only match exactly.  */
       if (shndx >= SHN_LORESERVE)
@@ -50,10 +51,10 @@ dwfl_module_addrsym (Dwfl_Module *mod, GElf_Addr addr,
       /* Figure out what section ADDR lies in.  */
       if (addr_shndx == SHN_UNDEF)
 	{
-	  GElf_Addr mod_addr = dwfl_deadjust_st_value (mod, addr);
+	  GElf_Addr mod_addr = dwfl_deadjust_st_value (mod, symfile, addr);
 	  Elf_Scn *scn = NULL;
 	  addr_shndx = SHN_ABS;
-	  while ((scn = elf_nextscn (mod->symfile->elf, scn)) != NULL)
+	  while ((scn = elf_nextscn (symfile->elf, scn)) != NULL)
 	    {
 	      GElf_Shdr shdr_mem;
 	      GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
@@ -135,7 +136,11 @@ dwfl_module_addrsym (Dwfl_Module *mod, GElf_Addr addr,
 			}
 		      else if (closest_name == NULL
 			       && sym.st_value >= min_label
-			       && same_section (&sym, shndx))
+			       && same_section (&sym,
+						((size_t) i < mod->syments
+						 ? mod->symfile
+						 : &mod->aux_sym),
+						shndx))
 			{
 			  /* Handwritten assembly symbols sometimes have no
 			     st_size.  If no symbol with proper size includes
@@ -168,17 +173,19 @@ dwfl_module_addrsym (Dwfl_Module *mod, GElf_Addr addr,
 	}
     }
 
-  /* 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);
+  /* First go through global symbols.  mod->first_global and
+     mod->aux_first_global are setup by dwfl_module_getsymtab to the
+     index of the first global symbol in the module's symbol table.  Both
+     are zero when unknown.  All symbols with local binding come first in
+     the symbol table, then all globals.  */
+  int first_global = mod->first_global + mod->aux_first_global - 1;
+  search_table (first_global < 0 ? 1 : 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
+  if (closest_name == NULL && first_global > 1
       && (sizeless_name == NULL || sizeless_sym.st_value != addr))
-    search_table (1, mod->first_global);
+    search_table (1, first_global);
 
   /* If we found no proper sized symbol to use, fall back to the best
      candidate sizeless symbol we found, if any.  */