Try to load PDB path from CodeView record

gdb/pdb.c

@@ -32,6 +32,15 @@ HACK: Honestly, this whole thing is a hack:
 #include <regex>
 #include <fstream>
 #include <cassert>
+
+extern "C" {
+#include <coff/internal.h>
+#include <coff/x86_64.h> //this is really dumb but oh well
+#include <coff/pe.h>
+#include <libcoff.h>
+#include <libpei.h>
+}
+
 #include "psympriv.h"
 
 //BEGIN radare2 imports
@@ -60,6 +69,10 @@ get_r_pdb (const std::string & path)
   else if (path.rfind ("target:", 0) == 0)
     {
       auto target = find_target_at (process_stratum);
+      if (!target)
+        {
+          return nullptr;
+        }
 
       void *buffer;
       size_t length;
@@ -70,8 +83,8 @@ get_r_pdb (const std::string & path)
         auto fd = target->fileio_open (nullptr,
                                        path.c_str () + sizeof ("target:") - 1,
                                        FILEIO_O_RDONLY,
-                                       /* mode */ 0,
-                                       /* warn_if_slow */ true,
+                                       0 /* mode */,
+                                       true /* warn_if_slow */,
                                        &errno);
 
         if (fd == -1)
@@ -127,19 +140,109 @@ get_r_pdb (const std::string & path)
   return nullptr;
 }
 
-static std::string
-get_pdb_path (struct objfile *objfile)
+static gdb::optional<std::string>
+get_codeview_pdb_path (objfile *objfile)
 {
-  /* HACK: Use _bfd_XXi_slurp_codeview_record to find the 'correct' PDB path.
+  gdb::optional<std::string> nullopt;
 
-     We should use this as fallback, but we shouldn't try to find a PDB if
-     there is no codeview record at all.  */
+  bfd *abfd = objfile->obfd;
+
+  pe_data_type *pe = pe_data (abfd);
+  struct internal_extra_pe_aouthdr *extra = &pe->pe_opthdr;
+
+  bfd_size_type size = extra->DataDirectory[PE_DEBUG_DATA].Size;
+  if (size == 0)
+    return nullopt;
+  bfd_vma addr = extra->DataDirectory[PE_DEBUG_DATA].VirtualAddress + extra->ImageBase;
+
+  asection *section;
+  for (section = abfd->sections; section != nullptr; section = section->next)
+    {
+      if ((addr >= section->vma) && (addr < (section->vma + section->size)))
+        break;
+    }
+  if (section == nullptr || !(section->flags & SEC_HAS_CONTENTS) || section->size < size)
+    return nullopt;
+
+  bfd_size_type data_offset;
+  data_offset = addr - section->vma;
+  if (size > (section->size - data_offset))
+    return nullopt;
+
+  bfd_byte *data = nullptr;
+  //TODO: Check if this leaks memory (data isn't freed)
+  if (!bfd_malloc_and_get_section (abfd, section, &data))
+    {
+      if (data != nullptr)
+        free (data);
+      return nullopt;
+    }
+
+  for (auto i = 0; i < size / sizeof (struct external_IMAGE_DEBUG_DIRECTORY); i++)
+    {
+      struct external_IMAGE_DEBUG_DIRECTORY *ext
+        = &((struct external_IMAGE_DEBUG_DIRECTORY *) (data + data_offset))[i];
+      struct internal_IMAGE_DEBUG_DIRECTORY idd{};
+
+      _bfd_pei_swap_debugdir_in (abfd, ext, &idd);
+
+      if (idd.Type == PE_IMAGE_DEBUG_TYPE_CODEVIEW)
+        {
+          char buffer[256 + 1] ATTRIBUTE_ALIGNED_ALIGNOF (CODEVIEW_INFO);
+          auto *cvinfo = (CODEVIEW_INFO *) buffer;
+
+          if (!_bfd_pei_slurp_codeview_record (abfd, (file_ptr) idd.PointerToRawData,
+                                               idd.SizeOfData, cvinfo))
+            continue;
+
+          return std::string (cvinfo->PdbFileName);
+        }
+    }
+
+  return nullopt;
+}
+
+static std::vector<std::string>
+get_pdb_paths (struct objfile *objfile)
+{
+  std::vector<std::string> paths;
+
+  auto codeview_pdb_path = get_codeview_pdb_path (objfile);
+  if (!codeview_pdb_path)
+    return paths;
+
+  paths.push_back (*codeview_pdb_path);
+  paths.push_back ("target:" + *codeview_pdb_path);
 
   auto real_path = gdb_realpath (objfile->original_name);
-  auto pdb_path = std::regex_replace (std::string (real_path.get ()),
+  auto naive_pdb_path = std::regex_replace (std::string (real_path.get ()),
                                             std::regex ("\\.[^.]*$"),
                                             ".pdb");
-  return pdb_path;
+  naive_pdb_path = std::regex_replace (naive_pdb_path,
+                                       std::regex ("target:"),
+                                       "");
+
+  paths.push_back (naive_pdb_path);
+  paths.push_back ("target:" + naive_pdb_path);
+
+  return paths;
+}
+
+static std::tuple<std::unique_ptr<R_PDB>, std::string>
+load_pdb (objfile *objfile)
+{
+  auto paths = get_pdb_paths (objfile);
+
+  if (paths.empty ()) return {nullptr, std::string ()};
+
+  for (auto & path : paths)
+    {
+      auto p = get_r_pdb (path);
+      if (p)
+        return {std::move (p), path};
+    }
+
+  return {nullptr, std::string ()};
 }
 
 struct find_section_by_name_args {
@@ -172,11 +275,13 @@ section_by_name (const char *name, struct objfile *objfile)
 void
 read_pdb (struct objfile *objfile, minimal_symbol_reader & reader)
 {
-  auto pdb_path = get_pdb_path (objfile);
+  std::unique_ptr<R_PDB> pdb;
+  std::string pdb_path;
+  std::tie (pdb, pdb_path) = load_pdb (objfile);
+
+  if (!pdb)
+    return;
 
-  auto pdb = get_r_pdb (pdb_path);
-  if (pdb)
-    {
   if (pdb->pdb_parse (pdb.get ()))
     {
       SStreamParseFunc *omap = nullptr, *sctns = nullptr, *sctns_orig = nullptr, *gsym = nullptr, *tmp;
@@ -239,7 +344,8 @@ read_pdb (struct objfile *objfile, minimal_symbol_reader & reader)
       while (r_list_iter_next (it))
         {
           gdata = (SGlobal *) r_list_iter_get (it);
-              sctn_header = (SIMAGE_SECTION_HEADER*) r_list_get_n (pe_stream->sections_hdrs, (gdata->segment - 1));
+          sctn_header = (SIMAGE_SECTION_HEADER *) r_list_get_n (pe_stream->sections_hdrs,
+                                                                gdata->segment - 1);
           if (sctn_header)
             {
               asection *sect = section_by_name (sctn_header->name, objfile);
@@ -257,4 +363,3 @@ read_pdb (struct objfile *objfile, minimal_symbol_reader & reader)
 
   pdb->finish_pdb_parse (pdb.get ());
 }
-}