Add plugin_input_file_t

This patchs adds plugin_input_file_t to implement get_input_file, get_view
and release_input_file.  The maximum memeory overhead per IR input file
are about 40 bytes for plugin_input_file_t plus the memory to store input
IR filename.  According to

http://gcc.gnu.org/wiki/whopr/driver

RELEASE_INPUT_FILE: Function pointer to the linker interface that
releases a file descriptor for a claimed input file. The plug-in library
must call this interface for each file descriptor obtained by the "get
input file" interface. It must release all such file descriptors before
returning from the WPA phase.

However, GCC plug-in library doesn't use the "get input file" interface.
It processed the IR input in the claim file handler.  Since the the file
descriptor opened for the IR input was unused after the claim file
handler returns and GCC plug-in library before GCC 5 doesn't call the
RELEASE_INPUT_FILE function pointer, ld closed the file descriptor to
avoid leaking file descriptor.  But this approach doesn't work with
other plug-in libraries which uses the "get input file", "get view" and
"release input file" interfaces.  To avoid file descriptor leak with
GCC prior to GCC 5 and support other plug-in libraries at the same time,
we close the file descriptor only if the input IR file is a bfd_object
file.  This scheme doesn't work when a plug-in library needs the file
descriptor and its IR is stored in bfd_object file.

	PR ld/17878
	* plugin.c: Include <errno.h>.
	(errno): New.  Declare if needed.
	(plugin_input_file_t): New.
	(get_input_file): Implemented.
	(get_view): Likewise.
	(release_input_file): Likewise.
	(add_symbols): Updated.
	(get_symbols): Likewise.
	(plugin_maybe_claim): Allocate a plugin_input_file_t.  Close fd
	only for a bfd_object input.

2 files changed, 119 insertions, 16 deletions

diff --git a/ld/ChangeLog b/ld/ChangeLog
index 472cf36..0d767ba 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,17 @@
+2015-02-05  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/17878
+	* plugin.c: Include <errno.h>.
+	(errno): New.  Declare if needed.
+	(plugin_input_file_t): New.
+	(get_input_file): Implemented.
+	(get_view): Likewise.
+	(release_input_file): Likewise.
+	(add_symbols): Updated.
+	(get_symbols): Likewise.
+	(plugin_maybe_claim): Allocate a plugin_input_file_t.  Close fd
+	only for a bfd_object input.
+
 2015-02-02  Alan Modra  <amodra@gmail.com>
 
 	* emultempl/ppc64elf.em (toc_section_name): New var.
diff --git a/ld/plugin.c b/ld/plugin.c
index cfbca0b..28236f2 100644
--- a/ld/plugin.c
+++ b/ld/plugin.c
@@ -32,6 +32,10 @@
 #include "plugin.h"
 #include "plugin-api.h"
 #include "elf-bfd.h"
+#include <errno.h>
+#if !(defined(errno) || defined(_MSC_VER) && defined(_INC_ERRNO))
+extern int errno;
+#endif
 #if !defined (HAVE_DLFCN_H) && defined (HAVE_WINDOWS_H)
 #include <windows.h>
 #endif
@@ -72,6 +76,17 @@ typedef struct plugin
   bfd_boolean cleanup_done;
 } plugin_t;
 
+/* The internal version of struct ld_plugin_input_file with a BFD
+   pointer.  */
+typedef struct plugin_input_file
+{
+  bfd *abfd;
+  char *name;
+  int fd;
+  off_t offset;
+  off_t filesize;
+} plugin_input_file_t;
+
 /* The master list of all plugins.  */
 static plugin_t *plugins_list = NULL;
 
@@ -418,7 +433,8 @@ static enum ld_plugin_status
 add_symbols (void *handle, int nsyms, const struct ld_plugin_symbol *syms)
 {
   asymbol **symptrs;
-  bfd *abfd = handle;
+  plugin_input_file_t *input = handle;
+  bfd *abfd = input->abfd;
   int n;
 
   ASSERT (called_plugin);
@@ -441,28 +457,66 @@ 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)
 {
+  const plugin_input_file_t *input = handle;
+
   ASSERT (called_plugin);
-  return LDPS_ERR;
+
+  file->name = input->name;
+  file->offset = input->offset;
+  file->filesize = input->filesize;
+  file->handle = (void *) handle;
+
+  return LDPS_OK;
 }
 
 /* Get view of the input file.  */
 static enum ld_plugin_status
-get_view (const void *handle ATTRIBUTE_UNUSED,
-	  const void **viewp ATTRIBUTE_UNUSED)
+get_view (const void *handle, const void **viewp)
 {
+  const plugin_input_file_t *input = handle;
+  char *buffer;
+  size_t size;
+
   ASSERT (called_plugin);
-  return LDPS_ERR;
+
+  if (lseek (input->fd, input->offset, SEEK_SET) < 0)
+    return LDPS_ERR;
+
+  size = input->filesize;
+  buffer = bfd_alloc (input->abfd, size);
+  if (buffer == NULL)
+    return LDPS_ERR;
+  *viewp = buffer;
+
+  do
+    {
+      ssize_t got = read (input->fd, buffer, size);
+      if (got == 0)
+	break;
+      else if (got > 0)
+	{
+	  buffer += got;
+	  size -= got;
+	}
+      else if (errno != EINTR)
+	return LDPS_ERR;
+    }
+  while (size > 0);
+
+  return LDPS_OK;
 }
 
 /* Release the input file.  */
 static enum ld_plugin_status
-release_input_file (const void *handle ATTRIBUTE_UNUSED)
+release_input_file (const void *handle)
 {
+  const plugin_input_file_t *input = handle;
   ASSERT (called_plugin);
-  return LDPS_ERR;
+  if (input->fd != -1)
+    close (input->fd);
+  return LDPS_OK;
 }
 
 /* Return TRUE if a defined symbol might be reachable from outside the
@@ -515,7 +569,8 @@ static enum ld_plugin_status
 get_symbols (const void *handle, int nsyms, struct ld_plugin_symbol *syms,
 	     int def_ironly_exp)
 {
-  const bfd *abfd = handle;
+  const plugin_input_file_t *input = handle;
+  const bfd *abfd = (const bfd *) input->abfd;
   int n;
 
   ASSERT (called_plugin);
@@ -879,16 +934,50 @@ plugin_maybe_claim (struct ld_plugin_input_file *file,
 		    lang_input_statement_type *entry)
 {
   int claimed = 0;
+  plugin_input_file_t *input;
+  size_t namelength;
 
   /* We create a dummy BFD, initially empty, to house whatever symbols
      the plugin may want to add.  */
-  file->handle = plugin_get_ir_dummy_bfd (entry->the_bfd->filename,
-					  entry->the_bfd);
+  bfd *abfd = plugin_get_ir_dummy_bfd (entry->the_bfd->filename,
+				       entry->the_bfd);
+
+  input = bfd_alloc (abfd, sizeof (*input));
+  if (input == NULL)
+    einfo (_("%P%F: plugin failed to allocate memory for input: %s\n"),
+	   bfd_get_error ());
+
+  input->abfd = abfd;
+  input->fd = file->fd;
+  input->offset  = file->offset;
+  input->filesize = file->filesize;
+  namelength = strlen (entry->the_bfd->filename) + 1;
+  input->name = bfd_alloc (abfd, namelength);
+  if (input->name == NULL)
+    einfo (_("%P%F: plugin failed to allocate memory for input filename: %s\n"),
+	   bfd_get_error ());
+  memcpy (input->name, entry->the_bfd->filename, namelength);
+
+  file->handle = input;
+
   if (plugin_call_claim_file (file, &claimed))
     einfo (_("%P%F: %s: plugin reported error claiming file\n"),
 	   plugin_error_plugin ());
-  /* fd belongs to us, not the plugin; but we don't need it.  */
-  close (file->fd);
+
+  if (bfd_check_format (entry->the_bfd, bfd_object))
+    {
+      /* FIXME: fd belongs to us, not the plugin.  IR for GCC plugin,
+	 which doesn't need fd after plugin_call_claim_file, is
+	 stored in bfd_object file.  Since GCC plugin before GCC 5
+	 doesn't call release_input_file, we close it here.  IR for
+	 LLVM plugin, which needs fd after plugin_call_claim_file and
+	 calls release_input_file after it is done, is stored in
+	 non-bfd_object file.  This scheme doesn't work when a plugin
+	 needs fd and its IR is stored in bfd_object file.  */
+      close (file->fd);
+      input->fd = -1;
+    }
+
   if (claimed)
     {
       /* Discard the real file's BFD and substitute the dummy one.  */
@@ -897,7 +986,7 @@ plugin_maybe_claim (struct ld_plugin_input_file *file,
 	 bfd_close for archives.  */
       if (entry->the_bfd->my_archive == NULL)
 	bfd_close (entry->the_bfd);
-      entry->the_bfd = file->handle;
+      entry->the_bfd = abfd;
       entry->flags.claimed = TRUE;
       bfd_make_readable (entry->the_bfd);
     }
@@ -905,7 +994,7 @@ plugin_maybe_claim (struct ld_plugin_input_file *file,
     {
       /* If plugin didn't claim the file, we don't need the dummy bfd.
 	 Can't avoid speculatively creating it, alas.  */
-      bfd_close_all_done (file->handle);
+      bfd_close_all_done (abfd);
       entry->flags.claimed = FALSE;
     }
 }