PR23652, Use symbols from debug bfd for _bfd_elf_find_function

Sometimes DWARF info for a function is incomplete, and the function
can be retrieved by examining symbols.  However, when separate debug
files are used it may be that the original file is completely
stripped of symbols.  This patch teaches BFD to look at symbols from
the debug file in that case.

The patch also removes arm_elf_find_function, instead implementing
elf_backend_maybe_function_sym.  arm_elf_find_function was written
before the generic _bfd_elf_find_function called maybe_function_sym.
aarch64 copied arm, so that file gets the same treatment.  There is
some chance this will speed up arm and aarch64 lookup of function/line.

	PR 23652
	* dwarf2.c (_bfd_dwarf2_stash_syms): New function.
	(_bfd_dwarf2_find_nearest_line): Use it here, passing syms to
	_bfd_elf_find_function.  Call _bfd_elf_find_function in cases
	where _bfd_elf_find_nearest_line would do so.
	* elf.c (_bfd_elf_find_nearest_line): Omit _bfd_elf_find_function
	for dwarf2.
	* elfxx-mips.c (_bfd_mips_elf_find_nearest_line): Similarly.  Tidy.
	* elf32-arm.c (elf32_arm_maybe_function_sym): New function.
	(elf_backend_maybe_function_sym): Define.
	(arm_elf_find_function, elf32_arm_find_nearest_line): Delete.
	(bfd_elf32_find_nearest_line): Don't define.
	* elfnn-aarch64.c (elfNN_aarch64_maybe_function_sym): New function.
	(elf_backend_maybe_function_sym): Define.
	(aarch64_elf_find_function, elfNN_aarch64_find_nearest_line): Delete.
	(bfd_elfNN_find_nearest_line): Don't define.

6 files changed, 147 insertions, 253 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 3ef8515..4a0852e 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,5 +1,24 @@
 2019-11-27  Alan Modra  <amodra@gmail.com>
 
+	PR 23652
+	* dwarf2.c (_bfd_dwarf2_stash_syms): New function.
+	(_bfd_dwarf2_find_nearest_line): Use it here, passing syms to
+	_bfd_elf_find_function.  Call _bfd_elf_find_function in cases
+	where _bfd_elf_find_nearest_line would do so.
+	* elf.c (_bfd_elf_find_nearest_line): Omit _bfd_elf_find_function
+	for dwarf2.
+	* elfxx-mips.c (_bfd_mips_elf_find_nearest_line): Similarly.  Tidy.
+	* elf32-arm.c (elf32_arm_maybe_function_sym): New function.
+	(elf_backend_maybe_function_sym): Define.
+	(arm_elf_find_function, elf32_arm_find_nearest_line): Delete.
+	(bfd_elf32_find_nearest_line): Don't define.
+	* elfnn-aarch64.c (elfNN_aarch64_maybe_function_sym): New function.
+	(elf_backend_maybe_function_sym): Define.
+	(aarch64_elf_find_function, elfNN_aarch64_find_nearest_line): Delete.
+	(bfd_elfNN_find_nearest_line): Don't define.
+
+2019-11-27  Alan Modra  <amodra@gmail.com>
+
 	* elf32-sh.c (sh_reloc): Use a bfd_vma insn.
 	(sh_reloc <R_SH_IND12W>): Divide calculated relocation value
 	by two before applying to insn.  Correct overflow test.
diff --git a/bfd/dwarf2.c b/bfd/dwarf2.c
index c3d9ffc..e42483a 100644
--- a/bfd/dwarf2.c
+++ b/bfd/dwarf2.c
@@ -3894,6 +3894,40 @@ set_debug_vma (bfd *orig_bfd, bfd *debug_bfd)
     }
 }
 
+/* If the dwarf2 info was found in a separate debug file, return the
+   debug file section corresponding to the section in the original file
+   and the debug file symbols.  */
+
+static void
+_bfd_dwarf2_stash_syms (struct dwarf2_debug *stash, bfd *abfd,
+			asection **sec, asymbol ***syms)
+{
+  if (stash->bfd_ptr != abfd)
+    {
+      asection *s, *d;
+
+      if (*sec == NULL)
+	{
+	  *syms = stash->syms;
+	  return;
+	}
+
+      for (s = abfd->sections, d = stash->bfd_ptr->sections;
+	   s != NULL && d != NULL;
+	   s = s->next, d = d->next)
+	{
+	  if ((d->flags & SEC_DEBUGGING) != 0)
+	    break;
+	  if (s == *sec
+	      && strcmp (s->name, d->name) == 0)
+	    {
+	      *sec = d;
+	      *syms = stash->syms;
+	    }
+	}
+    }
+}
+
 /* Unset vmas for adjusted sections in STASH.  */
 
 static void
@@ -4888,16 +4922,26 @@ _bfd_dwarf2_find_nearest_line (bfd *abfd,
     }
 
  done:
-  if (function)
+  if (functionname_ptr && function && function->is_linkage)
+    *functionname_ptr = function->name;
+  else if (functionname_ptr
+	   && ((found && !*functionname_ptr)
+	       || (function && !function->is_linkage)))
     {
-      if (!function->is_linkage)
+      asymbol *fun;
+      asymbol **syms = symbols;
+      asection *sec = section;
+
+      if (symbols == NULL || *symbols == NULL)
+	_bfd_dwarf2_stash_syms (stash, abfd, &sec, &syms);
+      fun = _bfd_elf_find_function (abfd, syms, sec, offset,
+				    *filename_ptr ? NULL : filename_ptr,
+				    functionname_ptr);
+
+      if (function && !function->is_linkage)
 	{
-	  asymbol *fun;
 	  bfd_vma sec_vma;
 
-	  fun = _bfd_elf_find_function (abfd, symbols, section, offset,
-					*filename_ptr ? NULL : filename_ptr,
-					functionname_ptr);
 	  sec_vma = section->vma;
 	  if (section->output_section != NULL)
 	    sec_vma = section->output_section->vma + section->output_offset;
@@ -4908,8 +4952,8 @@ _bfd_dwarf2_find_nearest_line (bfd *abfd,
 	     to stop a repeated search of symbols.  */
 	  function->is_linkage = TRUE;
 	}
-      *functionname_ptr = function->name;
     }
+
   if ((abfd->flags & (EXEC_P | DYNAMIC)) == 0)
     unset_sections (stash);
 
diff --git a/bfd/elf.c b/bfd/elf.c
index a4f26da..1aa2603 100644
--- a/bfd/elf.c
+++ b/bfd/elf.c
@@ -9030,10 +9030,11 @@ _bfd_elf_find_nearest_line (bfd *abfd,
 				     filename_ptr, functionname_ptr,
 				     line_ptr, discriminator_ptr,
 				     dwarf_debug_sections,
-				     &elf_tdata (abfd)->dwarf2_find_line_info)
-      || _bfd_dwarf1_find_nearest_line (abfd, symbols, section, offset,
-					filename_ptr, functionname_ptr,
-					line_ptr))
+				     &elf_tdata (abfd)->dwarf2_find_line_info))
+    return TRUE;
+
+  if (_bfd_dwarf1_find_nearest_line (abfd, symbols, section, offset,
+				     filename_ptr, functionname_ptr, line_ptr))
     {
       if (!*functionname_ptr)
 	_bfd_elf_find_function (abfd, symbols, section, offset,
diff --git a/bfd/elf32-arm.c b/bfd/elf32-arm.c
index dca208f..37b5b64 100644
--- a/bfd/elf32-arm.c
+++ b/bfd/elf32-arm.c
@@ -16040,125 +16040,44 @@ elf32_arm_is_target_special_symbol (bfd * abfd ATTRIBUTE_UNUSED, asymbol * sym)
 					 BFD_ARM_SPECIAL_SYM_TYPE_ANY);
 }
 
-/* This is a version of _bfd_elf_find_function() from dwarf2.c except that
-   ARM mapping symbols are ignored when looking for function names
-   and STT_ARM_TFUNC is considered to a function type.  */
+/* If the ELF symbol SYM might be a function in SEC, return the
+   function size and set *CODE_OFF to the function's entry point,
+   otherwise return zero.  */
 
-static bfd_boolean
-arm_elf_find_function (bfd *	     abfd,
-		       asymbol **    symbols,
-		       asection *    section,
-		       bfd_vma	     offset,
-		       const char ** filename_ptr,
-		       const char ** functionname_ptr)
-{
-  const char * filename = NULL;
-  asymbol * func = NULL;
-  bfd_vma low_func = 0;
-  asymbol ** p;
-
-  if (symbols == NULL)
-    return FALSE;
-
-  if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
-    return FALSE;
-
-  for (p = symbols; *p != NULL; p++)
-    {
-      elf_symbol_type *q;
+static bfd_size_type
+elf32_arm_maybe_function_sym (const asymbol *sym, asection *sec,
+			      bfd_vma *code_off)
+{
+  bfd_size_type size;
 
-      q = (elf_symbol_type *) *p;
+  if ((sym->flags & (BSF_SECTION_SYM | BSF_FILE | BSF_OBJECT
+		     | BSF_THREAD_LOCAL | BSF_RELC | BSF_SRELC)) != 0
+      || sym->section != sec)
+    return 0;
 
-      switch (ELF_ST_TYPE (q->internal_elf_sym.st_info))
-	{
-	default:
-	  break;
-	case STT_FILE:
-	  filename = bfd_asymbol_name (&q->symbol);
-	  break;
+  if (!(sym->flags & BSF_SYNTHETIC))
+    switch (ELF_ST_TYPE (((elf_symbol_type *) sym)->internal_elf_sym.st_info))
+      {
 	case STT_FUNC:
 	case STT_ARM_TFUNC:
 	case STT_NOTYPE:
-	  /* Skip mapping symbols.  */
-	  if ((q->symbol.flags & BSF_LOCAL)
-	      && bfd_is_arm_special_symbol_name (q->symbol.name,
-		    BFD_ARM_SPECIAL_SYM_TYPE_ANY))
-	    continue;
-	  /* Fall through.  */
-	  if (bfd_asymbol_section (&q->symbol) == section
-	      && q->symbol.value >= low_func
-	      && q->symbol.value <= offset)
-	    {
-	      func = (asymbol *) q;
-	      low_func = q->symbol.value;
-	    }
 	  break;
-	}
-    }
-
-  if (func == NULL)
-    return FALSE;
-
-  if (filename_ptr)
-    *filename_ptr = filename;
-  if (functionname_ptr)
-    *functionname_ptr = bfd_asymbol_name (func);
-
-  return TRUE;
-}
-
-
-/* Find the nearest line to a particular section and offset, for error
-   reporting.   This code is a duplicate of the code in elf.c, except
-   that it uses arm_elf_find_function.  */
-
-static bfd_boolean
-elf32_arm_find_nearest_line (bfd *	    abfd,
-			     asymbol **	    symbols,
-			     asection *	    section,
-			     bfd_vma	    offset,
-			     const char **  filename_ptr,
-			     const char **  functionname_ptr,
-			     unsigned int * line_ptr,
-			     unsigned int * discriminator_ptr)
-{
-  bfd_boolean found = FALSE;
-
-  if (_bfd_dwarf2_find_nearest_line (abfd, symbols, NULL, section, offset,
-				     filename_ptr, functionname_ptr,
-				     line_ptr, discriminator_ptr,
-				     dwarf_debug_sections,
-				     & elf_tdata (abfd)->dwarf2_find_line_info))
-    {
-      if (!*functionname_ptr)
-	arm_elf_find_function (abfd, symbols, section, offset,
-			       *filename_ptr ? NULL : filename_ptr,
-			       functionname_ptr);
-
-      return TRUE;
-    }
-
-  /* Skip _bfd_dwarf1_find_nearest_line since no known ARM toolchain
-     uses DWARF1.  */
-
-  if (! _bfd_stab_section_find_nearest_line (abfd, symbols, section, offset,
-					     & found, filename_ptr,
-					     functionname_ptr, line_ptr,
-					     & elf_tdata (abfd)->line_info))
-    return FALSE;
-
-  if (found && (*functionname_ptr || *line_ptr))
-    return TRUE;
-
-  if (symbols == NULL)
-    return FALSE;
+	default:
+	  return 0;
+      }
 
-  if (! arm_elf_find_function (abfd, symbols, section, offset,
-			       filename_ptr, functionname_ptr))
-    return FALSE;
+  if ((sym->flags & BSF_LOCAL)
+      && bfd_is_arm_special_symbol_name (sym->name,
+					 BFD_ARM_SPECIAL_SYM_TYPE_ANY))
+    return 0;
 
-  *line_ptr = 0;
-  return TRUE;
+  *code_off = sym->value;
+  size = 0;
+  if (!(sym->flags & BSF_SYNTHETIC))
+    size = ((elf_symbol_type *) sym)->internal_elf_sym.st_size;
+  if (size == 0)
+    size = 1;
+  return size;
 }
 
 static bfd_boolean
@@ -20488,7 +20407,6 @@ elf32_arm_backend_symbol_processing (bfd *abfd, asymbol *sym)
 #define bfd_elf32_bfd_link_hash_table_create	elf32_arm_link_hash_table_create
 #define bfd_elf32_bfd_reloc_type_lookup		elf32_arm_reloc_type_lookup
 #define bfd_elf32_bfd_reloc_name_lookup		elf32_arm_reloc_name_lookup
-#define bfd_elf32_find_nearest_line		elf32_arm_find_nearest_line
 #define bfd_elf32_find_inliner_info		elf32_arm_find_inliner_info
 #define bfd_elf32_new_section_hook		elf32_arm_new_section_hook
 #define bfd_elf32_bfd_is_target_special_symbol	elf32_arm_is_target_special_symbol
@@ -20496,6 +20414,7 @@ elf32_arm_backend_symbol_processing (bfd *abfd, asymbol *sym)
 #define bfd_elf32_get_synthetic_symtab	elf32_arm_get_synthetic_symtab
 
 #define elf_backend_get_symbol_type		elf32_arm_get_symbol_type
+#define elf_backend_maybe_function_sym		elf32_arm_maybe_function_sym
 #define elf_backend_gc_mark_hook		elf32_arm_gc_mark_hook
 #define elf_backend_gc_mark_extra_sections	elf32_arm_gc_mark_extra_sections
 #define elf_backend_check_relocs		elf32_arm_check_relocs
diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index a710711..51d7526 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -7999,122 +7999,43 @@ elfNN_aarch64_is_target_special_symbol (bfd *abfd ATTRIBUTE_UNUSED,
 					     BFD_AARCH64_SPECIAL_SYM_TYPE_ANY);
 }
 
-/* This is a version of _bfd_elf_find_function() from dwarf2.c except that
-   AArch64 mapping symbols are ignored when looking for function names.  */
+/* If the ELF symbol SYM might be a function in SEC, return the
+   function size and set *CODE_OFF to the function's entry point,
+   otherwise return zero.  */
 
-static bfd_boolean
-aarch64_elf_find_function (bfd *          abfd,
-			   asymbol **     symbols,
-			   asection *     section,
-			   bfd_vma        offset,
-			   const char **  filename_ptr,
-			   const char **  functionname_ptr)
-{
-  const char *filename = NULL;
-  asymbol *func = NULL;
-  bfd_vma low_func = 0;
-  asymbol **p;
-
-  if (symbols == NULL)
-    return FALSE;
-
-  if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
-    return FALSE;
-
-  for (p = symbols; *p != NULL; p++)
-    {
-      elf_symbol_type *q;
+static bfd_size_type
+elfNN_aarch64_maybe_function_sym (const asymbol *sym, asection *sec,
+				  bfd_vma *code_off)
+{
+  bfd_size_type size;
 
-      q = (elf_symbol_type *) * p;
+  if ((sym->flags & (BSF_SECTION_SYM | BSF_FILE | BSF_OBJECT
+		     | BSF_THREAD_LOCAL | BSF_RELC | BSF_SRELC)) != 0
+      || sym->section != sec)
+    return 0;
 
-      switch (ELF_ST_TYPE (q->internal_elf_sym.st_info))
-	{
-	default:
-	  break;
-	case STT_FILE:
-	  filename = bfd_asymbol_name (&q->symbol);
-	  break;
+  if (!(sym->flags & BSF_SYNTHETIC))
+    switch (ELF_ST_TYPE (((elf_symbol_type *) sym)->internal_elf_sym.st_info))
+      {
 	case STT_FUNC:
 	case STT_NOTYPE:
-	  /* Skip mapping symbols.  */
-	  if ((q->symbol.flags & BSF_LOCAL)
-	      && (bfd_is_aarch64_special_symbol_name
-		  (q->symbol.name, BFD_AARCH64_SPECIAL_SYM_TYPE_ANY)))
-	    continue;
-	  /* Fall through.  */
-	  if (bfd_asymbol_section (&q->symbol) == section
-	      && q->symbol.value >= low_func && q->symbol.value <= offset)
-	    {
-	      func = (asymbol *) q;
-	      low_func = q->symbol.value;
-	    }
 	  break;
-	}
-    }
-
-  if (func == NULL)
-    return FALSE;
-
-  if (filename_ptr)
-    *filename_ptr = filename;
-  if (functionname_ptr)
-    *functionname_ptr = bfd_asymbol_name (func);
-
-  return TRUE;
-}
-
-
-/* Find the nearest line to a particular section and offset, for error
-   reporting.   This code is a duplicate of the code in elf.c, except
-   that it uses aarch64_elf_find_function.  */
-
-static bfd_boolean
-elfNN_aarch64_find_nearest_line (bfd *abfd,
-				 asymbol **symbols,
-				 asection *section,
-				 bfd_vma offset,
-				 const char **filename_ptr,
-				 const char **functionname_ptr,
-				 unsigned int *line_ptr,
-				 unsigned int *discriminator_ptr)
-{
-  bfd_boolean found = FALSE;
-
-  if (_bfd_dwarf2_find_nearest_line (abfd, symbols, NULL, section, offset,
-				     filename_ptr, functionname_ptr,
-				     line_ptr, discriminator_ptr,
-				     dwarf_debug_sections,
-				     &elf_tdata (abfd)->dwarf2_find_line_info))
-    {
-      if (!*functionname_ptr)
-	aarch64_elf_find_function (abfd, symbols, section, offset,
-				   *filename_ptr ? NULL : filename_ptr,
-				   functionname_ptr);
-
-      return TRUE;
-    }
-
-  /* Skip _bfd_dwarf1_find_nearest_line since no known AArch64
-     toolchain uses DWARF1.  */
-
-  if (!_bfd_stab_section_find_nearest_line (abfd, symbols, section, offset,
-					    &found, filename_ptr,
-					    functionname_ptr, line_ptr,
-					    &elf_tdata (abfd)->line_info))
-    return FALSE;
-
-  if (found && (*functionname_ptr || *line_ptr))
-    return TRUE;
-
-  if (symbols == NULL)
-    return FALSE;
+	default:
+	  return 0;
+      }
 
-  if (!aarch64_elf_find_function (abfd, symbols, section, offset,
-				  filename_ptr, functionname_ptr))
-    return FALSE;
+  if ((sym->flags & BSF_LOCAL)
+      && bfd_is_aarch64_special_symbol_name (sym->name,
+					     BFD_AARCH64_SPECIAL_SYM_TYPE_ANY))
+    return 0;
 
-  *line_ptr = 0;
-  return TRUE;
+  *code_off = sym->value;
+  size = 0;
+  if (!(sym->flags & BSF_SYNTHETIC))
+    size = ((elf_symbol_type *) sym)->internal_elf_sym.st_size;
+  if (size == 0)
+    size = 1;
+  return size;
 }
 
 static bfd_boolean
@@ -10123,9 +10044,6 @@ const struct elf_size_info elfNN_aarch64_size_info =
 #define bfd_elfNN_find_inliner_info		\
   elfNN_aarch64_find_inliner_info
 
-#define bfd_elfNN_find_nearest_line		\
-  elfNN_aarch64_find_nearest_line
-
 #define bfd_elfNN_get_synthetic_symtab		\
   elfNN_aarch64_get_synthetic_symtab
 
@@ -10170,6 +10088,9 @@ const struct elf_size_info elfNN_aarch64_size_info =
 #define elf_backend_output_arch_local_syms	\
   elfNN_aarch64_output_arch_local_syms
 
+#define elf_backend_maybe_function_sym		\
+  elfNN_aarch64_maybe_function_sym
+
 #define elf_backend_plt_sym_val			\
   elfNN_aarch64_plt_sym_val
 
diff --git a/bfd/elfxx-mips.c b/bfd/elfxx-mips.c
index 3982ed2..e9af7ab 100644
--- a/bfd/elfxx-mips.c
+++ b/bfd/elfxx-mips.c
@@ -13078,27 +13078,17 @@ _bfd_mips_elf_find_nearest_line (bfd *abfd, asymbol **symbols,
 				     filename_ptr, functionname_ptr,
 				     line_ptr, discriminator_ptr,
 				     dwarf_debug_sections,
-				     &elf_tdata (abfd)->dwarf2_find_line_info)
-      || _bfd_dwarf1_find_nearest_line (abfd, symbols, section, offset,
-					filename_ptr, functionname_ptr,
-					line_ptr))
-    {
-      /* PR 22789: If the function name or filename was not found through
-	 the debug information, then try an ordinary lookup instead.  */
-      if ((functionname_ptr != NULL && *functionname_ptr == NULL)
-	  || (filename_ptr != NULL && *filename_ptr == NULL))
-	{
-	  /* Do not override already discovered names.  */
-	  if (functionname_ptr != NULL && *functionname_ptr != NULL)
-	    functionname_ptr = NULL;
-
-	  if (filename_ptr != NULL && *filename_ptr != NULL)
-	    filename_ptr = NULL;
-
-	  _bfd_elf_find_function (abfd, symbols, section, offset,
-				  filename_ptr, functionname_ptr);
-	}
+				     &elf_tdata (abfd)->dwarf2_find_line_info))
+    return TRUE;
 
+  if (_bfd_dwarf1_find_nearest_line (abfd, symbols, section, offset,
+				     filename_ptr, functionname_ptr,
+				     line_ptr))
+    {
+      if (!*functionname_ptr)
+	_bfd_elf_find_function (abfd, symbols, section, offset,
+				*filename_ptr ? NULL : filename_ptr,
+				functionname_ptr);
       return TRUE;
     }