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Re: LLVM collaboration?


Rafael,

As I mentioned earlier on IRC, the current trunk LLVM plugin requires get_view and get/release_input_file (which had not previously been the case). I've attached a version of the patch that also provides an implementation of those functions.

 -Hal

----- Original Message -----
> From: "Hal Finkel" <hfinkel@anl.gov>
> To: "Rafael EspÃndola" <rafael.espindola@gmail.com>
> Cc: "Renato Golin" <renato.golin@linaro.org>, "gcc" <gcc@gcc.gnu.org>, "Jan Hubicka" <hubicka@ucw.cz>
> Sent: Tuesday, February 11, 2014 4:35:59 PM
> Subject: Re: LLVM collaboration?
> 
> ----- Original Message -----
> > From: "Rafael EspÃndola" <rafael.espindola@gmail.com>
> > To: "Jan Hubicka" <hubicka@ucw.cz>
> > Cc: "Renato Golin" <renato.golin@linaro.org>, "gcc"
> > <gcc@gcc.gnu.org>, "Hal Finkel" <hfinkel@anl.gov>
> > Sent: Tuesday, February 11, 2014 3:38:40 PM
> > Subject: Re: Fwd: LLVM collaboration?
> > 
> > > My reading of bfd/plugin.c is that it basically walks the
> > > directory
> > > and looks
> > > for first plugin that returns OK for onload. (that is always the
> > > case for
> > > GCC/LLVM plugins).  So if I instlal GCC and llvm plugin there it
> > > will
> > > depend who will end up being first and only that plugin will be
> > > used.
> > >
> > > We need multiple plugin support as suggested by the directory
> > > name
> > > ;)
> > >
> > > Also it sems that currently plugin is not used if file is ELF for
> > > ar/nm/ranlib
> > > (as mentioned by Markus) and also GNU-ld seems to choke on LLVM
> > > object files
> > > even if it has plugin.
> > >
> > > This probably needs ot be sanitized.
> > 
> > CCing Hal Finkel. He got this to work some time ago. Not sure if he
> > ever ported the patches to bfd trunk.
> 
> I have a patch for binutils 2.24 (attached -- I think this works, I
> hand isolated it from my BG/Q patchset). I would not consider it to
> be of upstream quality, but I'd obviously appreciate any assistance
> on making everything clean and proper ;)
> 
>  -Hal
> 
> > 
> > >> For OS X the situation is a bit different. There instead of a
> > >> plugin
> > >> the linker loads a library: libLTO.dylib. When doing LTO with a
> > >> newer
> > >> llvm, one needs to set DYLD_LIBRARY_PATH. I think I proposed
> > >> setting
> > >> that from clang some time ago, but I don't remember the outcome.
> > >>
> > >> In theory GCC could implement a libLTO.dylib and set
> > >> DYLD_LIBRARY_PATH. The gold/bfd plugin that LLVM uses is
> > >> basically
> > >> a
> > >> API mapping the other way, so the job would be inverting it. The
> > >> LTO
> > >> model ld64 is a bit more strict about knowing all symbol
> > >> definitions
> > >> and uses (including inline asm), so there would be work to be
> > >> done
> > >> to
> > >> cover that, but the simple cases shouldn't be too hard.
> > >
> > > I would not care that much about symbols in asm definitions to
> > > start with.
> > > Even if we will force users to non-LTO those object files, it
> > > would
> > > be an
> > > improvement over what we have now.
> > >
> > > One problem is that we need a volunteer to implement the reverse
> > > glue
> > > (libLTO->plugin API), since I do not have an OS X box (well, have
> > > an old G5,
> > > but even that is quite far from me right now)
> > >
> > > Why complete symbol tables are required? Can't ld64 be changed to
> > > ignore
> > > unresolved symbols in the first stage just like gold/gnu-ld does?
> > 
> > I am not sure about this. My *guess* is that it does dead stripping
> > computation before asking libLTO for the object file. I noticed the
> > issue while trying to LTO firefox some time ago.
> > 
> > Cheers,
> > Rafael
> > 
> 
> --
> Hal Finkel
> Assistant Computational Scientist
> Leadership Computing Facility
> Argonne National Laboratory
> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 99b7ca1..c2bf9c3 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -5054,7 +5054,9 @@ elf_link_add_archive_symbols (bfd *abfd, struct bfd_link_info *info)
 	    goto error_return;
 
 	  if (! bfd_check_format (element, bfd_object))
-	    goto error_return;
+	    /* goto error_return; */
+            /* this might be an object understood only by an LTO plugin */
+            bfd_elf_make_object (element);
 
 	  /* Doublecheck that we have not included this object
 	     already--it should be impossible, but there may be
diff --git a/ld/ldfile.c b/ld/ldfile.c
index 16baef8..159a60c 100644
--- a/ld/ldfile.c
+++ b/ld/ldfile.c
@@ -38,6 +38,7 @@
 #ifdef ENABLE_PLUGINS
 #include "plugin-api.h"
 #include "plugin.h"
+#include "elf-bfd.h"
 #endif /* ENABLE_PLUGINS */
 
 bfd_boolean  ldfile_assumed_script = FALSE;
@@ -124,6 +125,7 @@ bfd_boolean
 ldfile_try_open_bfd (const char *attempt,
 		     lang_input_statement_type *entry)
 {
+  int is_obj = 0;
   entry->the_bfd = bfd_openr (attempt, entry->target);
 
   if (verbose)
@@ -168,6 +170,34 @@ ldfile_try_open_bfd (const char *attempt,
 	{
 	  if (! bfd_check_format (check, bfd_object))
 	    {
+#ifdef ENABLE_PLUGINS
+	      if (check == entry->the_bfd
+		  && bfd_get_error () == bfd_error_file_not_recognized
+		  && ! ldemul_unrecognized_file (entry))
+		{
+                  if (plugin_active_plugins_p ()
+                      && !no_more_claiming)
+                    {
+                      int fd = open (attempt, O_RDONLY | O_BINARY);
+                      if (fd >= 0)
+                        {
+                          struct ld_plugin_input_file file;
+
+                          bfd_elf_make_object (entry->the_bfd);
+ 
+                          file.name = attempt;
+                          file.offset = 0;
+                          file.filesize = lseek (fd, 0, SEEK_END);
+                          file.fd = fd;
+                          plugin_maybe_claim (&file, entry);
+
+                          if (entry->flags.claimed)
+                            return TRUE;
+                        }
+                    }
+                }
+#endif /* ENABLE_PLUGINS */
+
 	      if (check == entry->the_bfd
 		  && entry->flags.search_dirs
 		  && bfd_get_error () == bfd_error_file_not_recognized
@@ -303,7 +333,9 @@ success:
      bfd_object that it sets the bfd's arch and mach, which
      will be needed when and if we want to bfd_create a new
      one using this one as a template.  */
-  if (bfd_check_format (entry->the_bfd, bfd_object)
+  if (((is_obj = bfd_check_format (entry->the_bfd, bfd_object))
+       || (bfd_get_format(entry->the_bfd) == bfd_unknown
+           && bfd_get_error () == bfd_error_file_not_recognized))
       && plugin_active_plugins_p ()
       && !no_more_claiming)
     {
@@ -312,6 +344,9 @@ success:
 	{
 	  struct ld_plugin_input_file file;
 
+          if (!is_obj)
+            bfd_elf_make_object (entry->the_bfd);
+
 	  file.name = attempt;
 	  file.offset = 0;
 	  file.filesize = lseek (fd, 0, SEEK_END);
diff --git a/ld/ldlang.h b/ld/ldlang.h
index 2dbec5a..8f05f75 100644
--- a/ld/ldlang.h
+++ b/ld/ldlang.h
@@ -305,6 +305,8 @@ typedef struct lang_input_statement_struct
   const char *target;
 
   struct lang_input_statement_flags flags;
+
+  struct ld_plugin_input_file *plugin_input_file;
 } lang_input_statement_type;
 
 typedef struct
diff --git a/ld/plugin.c b/ld/plugin.c
index 0d5339f..024e109 100644
--- a/ld/plugin.c
+++ b/ld/plugin.c
@@ -36,6 +36,8 @@
 #include <windows.h>
 #endif
 
+#include <sys/mman.h>
+
 /* Report plugin symbols.  */
 bfd_boolean report_plugin_symbols;
 
@@ -114,6 +116,7 @@ static const enum ld_plugin_tag tv_header_tags[] =
   LDPT_REGISTER_CLEANUP_HOOK,
   LDPT_ADD_SYMBOLS,
   LDPT_GET_INPUT_FILE,
+  LDPT_GET_VIEW,
   LDPT_RELEASE_INPUT_FILE,
   LDPT_GET_SYMBOLS,
   LDPT_GET_SYMBOLS_V2,
@@ -429,19 +432,75 @@ add_symbols (void *handle, int nsyms, const struct ld_plugin_symbol *syms)
 /* Get the input file information with an open (possibly re-opened)
    file descriptor.  */
 static enum ld_plugin_status
-get_input_file (const void *handle ATTRIBUTE_UNUSED,
-                struct ld_plugin_input_file *file ATTRIBUTE_UNUSED)
+get_input_file (const void *handle,
+                struct ld_plugin_input_file *file)
 {
+  bfd *abfd = (bfd*) handle;
+  struct ld_plugin_input_file *f;
+
   ASSERT (called_plugin);
-  return LDPS_ERR;
+
+  if (!abfd->usrdata)
+    return LDPS_BAD_HANDLE;
+  f = ((lang_input_statement_type *)(abfd->usrdata))->plugin_input_file;
+  if (!f)
+    return LDPS_BAD_HANDLE;
+
+  if (f->fd < 0)
+    f->fd = open (f->name, O_RDONLY | O_BINARY);
+  memcpy(file, f, sizeof(struct ld_plugin_input_file));
+
+  return LDPS_OK;
 }
 
-/* Release the input file.  */
 static enum ld_plugin_status
-release_input_file (const void *handle ATTRIBUTE_UNUSED)
+get_view (const void *handle, const void **viewp)
 {
+  bfd *abfd = (bfd*) handle;
+  struct ld_plugin_input_file *f;
+  off_t map_offset, offset_diff;
+
   ASSERT (called_plugin);
-  return LDPS_ERR;
+
+  if (!abfd->usrdata)
+    return LDPS_BAD_HANDLE;
+  f = ((lang_input_statement_type *)(abfd->usrdata))->plugin_input_file;
+  if (!f || f->fd <= 0)
+    return LDPS_BAD_HANDLE;
+
+  map_offset = f->offset & ~(sysconf(_SC_PAGE_SIZE) - 1);
+  offset_diff = f->offset - map_offset;
+  /* FIXME: We leak this? */
+  *viewp = (const void*)
+    (((char *) mmap(NULL, f->filesize + offset_diff, PROT_READ, MAP_PRIVATE,
+                    f->fd, map_offset)) + offset_diff);
+  if (!*viewp)
+    return LDPS_ERR;
+
+  return LDPS_OK;
+}
+
+/* Release the input file. */
+static enum ld_plugin_status
+release_input_file (const void *handle)
+{
+  bfd *abfd = (bfd*) handle;
+  struct ld_plugin_input_file *f;
+
+  ASSERT (called_plugin);
+
+  if (!abfd->usrdata)
+    return LDPS_BAD_HANDLE;
+  f = ((lang_input_statement_type *)(abfd->usrdata))->plugin_input_file;
+  if (!f)
+    return LDPS_BAD_HANDLE;
+
+  if (f->fd >= 0) {
+    close(f->fd);
+    f->fd = -1;
+  }
+
+  return LDPS_OK;
 }
 
 /* Return TRUE if a defined symbol might be reachable from outside the
@@ -724,6 +783,9 @@ set_tv_header (struct ld_plugin_tv *tv)
 	case LDPT_GET_INPUT_FILE:
 	  TVU(get_input_file) = get_input_file;
 	  break;
+	case LDPT_GET_VIEW:
+	  TVU(get_view) = get_view;
+	  break;
 	case LDPT_RELEASE_INPUT_FILE:
 	  TVU(release_input_file) = release_input_file;
 	  break;
@@ -867,9 +929,21 @@ plugin_maybe_claim (struct ld_plugin_input_file *file,
      the plugin may want to add.  */
   file->handle = plugin_get_ir_dummy_bfd (entry->the_bfd->filename,
 					  entry->the_bfd);
+
+  /* The plugin might call get_view on the provided handle,
+     prepare for that. */
+  lang_input_statement_type dummy_entry;
+  memset(&dummy_entry, 0, sizeof (lang_input_statement_type));
+  dummy_entry.plugin_input_file = file;
+  ((bfd *) file->handle)->usrdata = &dummy_entry;
+
   if (plugin_call_claim_file (file, &claimed))
     einfo (_("%P%F: %s: plugin reported error claiming file\n"),
 	   plugin_error_plugin ());
+
+  /* Make sure the dummy_entry is not used outside of this scope. */
+  ((bfd *) file->handle)->usrdata = NULL;
+
   /* fd belongs to us, not the plugin; but we don't need it.  */
   close (file->fd);
   if (claimed)
@@ -883,6 +957,17 @@ plugin_maybe_claim (struct ld_plugin_input_file *file,
       entry->the_bfd = file->handle;
       entry->flags.claimed = TRUE;
       bfd_make_readable (entry->the_bfd);
+
+      /* Save a copy of the input file information for use by get_input_file
+       * later. */
+      /* FIXME: We leak this? */
+      entry->plugin_input_file = (struct ld_plugin_input_file *)
+        xcalloc (1, sizeof (struct ld_plugin_input_file));
+      memcpy(entry->plugin_input_file, file,
+             sizeof (struct ld_plugin_input_file));
+      entry->plugin_input_file->fd = -1;
+      entry->plugin_input_file->name = xstrdup(file->name);
+      entry->plugin_input_file->handle = entry->the_bfd;
     }
   else
     {


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