Add plugin API for processing plugin-added input files

Gold plugins may wish to further process an input file added by a plugin. For
example, the plugin may need to assign a unique segment for sections in a
plugin-generated input file. This patch adds a plugin callback that the linker
will call when reading symbols from a new input file added after the
all_symbols_read event (i.e. an input file added by a plugin).

2017-12-11  Stephen Crane  <sjc@immunant.com>

	* plugin-api.h: Add new plugin hook to allow processing of input
	files added by a plugin.
	(ld_plugin_new_input_handler): New function hook type.
	(ld_plugin_register_new_input): New interface.
	(LDPT_REGISTER_NEW_INPUT_HOOK): New enum val.
	(tv_register_new_input): New member.

	* plugin.cc (Plugin::load): Include hooks for register_new_input
	in transfer vector.
	(Plugin::new_input): New function.
	(register_new_input): New function.
	(Plugin_manager::claim_file): Call Plugin::new_input if in
	replacement phase.
	* plugin.h (Plugin::set_new_input_handler): New function.
	* testsuite/plugin_new_section_layout.c: New plugin to test
	new_input plugin API.
	* testsuite/plugin_final_layout.sh: Add new input test.
	* testsuite/Makefile.am (plugin_layout_new_file): New test case.
	* testsuite/Makefile.in: Regenerate.

4 files changed, 227 insertions, 6 deletions

diff --git a/gold/testsuite/Makefile.am b/gold/testsuite/Makefile.am
index aad244c..16cae80 100644
--- a/gold/testsuite/Makefile.am
+++ b/gold/testsuite/Makefile.am
@@ -2401,6 +2401,23 @@ plugin_section_order.so: plugin_section_order.o gcctestdir/ld
 plugin_section_order.o: plugin_section_order.c
 	$(COMPILE) -O0 -c -fpic -o $@ $<
 
+# Uses the plugin_final_layout.sh script above to avoid duplication
+check_DATA += plugin_layout_new_file.stdout plugin_layout_new_file_readelf.stdout
+MOSTLYCLEANFILES += plugin_layout_new_file
+plugin_final_layout.o.syms: plugin_final_layout.o
+	$(TEST_READELF) -sW $< >$@ 2>/dev/null
+plugin_layout_new_file: plugin_final_layout.o.syms plugin_test.so plugin_new_section_layout.so gcctestdir/ld
+	$(CXXLINK) -Bgcctestdir/ -Wl,--plugin,"./plugin_test.so"  -Wl,--plugin,"./plugin_new_section_layout.so" plugin_final_layout.o.syms
+plugin_layout_new_file.stdout: plugin_layout_new_file
+	$(TEST_NM) -n --synthetic plugin_layout_new_file > plugin_layout_new_file.stdout
+plugin_layout_new_file_readelf.stdout: plugin_layout_new_file
+	$(TEST_READELF) -Wl plugin_layout_new_file > plugin_layout_new_file_readelf.stdout
+
+plugin_new_section_layout.so: plugin_new_section_layout.o gcctestdir/ld
+	$(LINK) -Bgcctestdir/ -shared plugin_new_section_layout.o
+plugin_new_section_layout.o: plugin_new_section_layout.c
+	$(COMPILE) -O0 -c -fpic -o $@ $<
+
 check_SCRIPTS += plugin_layout_with_alignment.sh
 check_DATA += plugin_layout_with_alignment.stdout
 MOSTLYCLEANFILES += plugin_layout_with_alignment
diff --git a/gold/testsuite/Makefile.in b/gold/testsuite/Makefile.in
index d625909..bbf8dc1 100644
--- a/gold/testsuite/Makefile.in
+++ b/gold/testsuite/Makefile.in
@@ -590,11 +590,16 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@@TLS_TRUE@am__append_51 = plugin_test_tls.err
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@am__append_52 = unused.c \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	plugin_final_layout \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	plugin_layout_new_file \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	plugin_layout_with_alignment
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@am__append_53 = plugin_final_layout.sh \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	plugin_layout_with_alignment.sh
+
+# Uses the plugin_final_layout.sh script above to avoid duplication
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@am__append_54 = plugin_final_layout.stdout \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	plugin_final_layout_readelf.stdout \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	plugin_layout_new_file.stdout \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	plugin_layout_new_file_readelf.stdout \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	plugin_layout_with_alignment.stdout
 @GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_55 = exclude_libs_test \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	local_labels_test \
@@ -7057,6 +7062,19 @@ uninstall-am:
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(LINK) -Bgcctestdir/ -shared plugin_section_order.o
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_section_order.o: plugin_section_order.c
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(COMPILE) -O0 -c -fpic -o $@ $<
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_final_layout.o.syms: plugin_final_layout.o
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(TEST_READELF) -sW $< >$@ 2>/dev/null
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_layout_new_file: plugin_final_layout.o.syms plugin_test.so plugin_new_section_layout.so gcctestdir/ld
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(CXXLINK) -Bgcctestdir/ -Wl,--plugin,"./plugin_test.so"  -Wl,--plugin,"./plugin_new_section_layout.so" plugin_final_layout.o.syms
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_layout_new_file.stdout: plugin_layout_new_file
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(TEST_NM) -n --synthetic plugin_layout_new_file > plugin_layout_new_file.stdout
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_layout_new_file_readelf.stdout: plugin_layout_new_file
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(TEST_READELF) -Wl plugin_layout_new_file > plugin_layout_new_file_readelf.stdout
+
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_new_section_layout.so: plugin_new_section_layout.o gcctestdir/ld
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(LINK) -Bgcctestdir/ -shared plugin_new_section_layout.o
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_new_section_layout.o: plugin_new_section_layout.c
+@GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(COMPILE) -O0 -c -fpic -o $@ $<
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_layout_with_alignment.o: plugin_layout_with_alignment.c
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@	$(COMPILE) -O0 -c -ffunction-sections  -fdata-sections -g -o $@ $<
 @GCC_TRUE@@NATIVE_LINKER_TRUE@@PLUGINS_TRUE@plugin_layout_with_alignment: plugin_layout_with_alignment.o plugin_section_alignment.so gcctestdir/ld
diff --git a/gold/testsuite/plugin_final_layout.sh b/gold/testsuite/plugin_final_layout.sh
index 5498591..3157bea 100755
--- a/gold/testsuite/plugin_final_layout.sh
+++ b/gold/testsuite/plugin_final_layout.sh
@@ -23,7 +23,7 @@
 # MA 02110-1301, USA.
 
 # The goal of this program is to verify if --section-ordering-file works as
-# intended.  File final_layout.cc is in this test.
+# intended.  File plugin_final_layout.cc is in this test.
 
 
 set -e
@@ -37,7 +37,7 @@ BEGIN { saw1 = 0; saw2 = 0; err = 0; }
      saw2 = 1;
      if (!saw1)
        {
-	  printf \"layout of $2 and $3 is not right\\n\";
+	  printf \"layout of $2 and $3 is not right in file $1\\n\";
 	  err = 1;
 	  exit 1;
        }
@@ -45,12 +45,12 @@ BEGIN { saw1 = 0; saw2 = 0; err = 0; }
 END {
       if (!saw1 && !err)
         {
-	  printf \"did not see $2\\n\";
+	  printf \"did not see $2 in file $1\\n\";
 	  exit 1;
 	}
       if (!saw2 && !err)
 	{
-	  printf \"did not see $3\\n\";
+	  printf \"did not see $3 in file $1\\n\";
 	  exit 1;
 	}
     }" $1
@@ -74,12 +74,12 @@ BEGIN { saw_section = 0; saw_unique = 0; }
 END {
       if (!saw_section)
 	{
-	  printf \"Section $2 not seen in output\\n\";
+	  printf \"Section $2 not seen in output file $1\\n\";
 	  exit 1;
 	}
       else if (!saw_unique)
 	{
-	  printf \"Unique segment not seen for: $2\\n\";
+	  printf \"Unique segment not seen for: $2 in file $1\\n\";
 	  exit 1;
 	}
     }" $1
@@ -88,3 +88,7 @@ END {
 check plugin_final_layout.stdout "_Z3foov" "_Z3barv"
 check plugin_final_layout.stdout "_Z3barv" "_Z3bazv"
 check_unique_segment plugin_final_layout_readelf.stdout ".text.plugin_created_unique"
+
+check plugin_layout_new_file.stdout "_Z3foov" "_Z3barv"
+check plugin_layout_new_file.stdout "_Z3barv" "_Z3bazv"
+check_unique_segment plugin_layout_new_file_readelf.stdout ".text.plugin_created_unique"
diff --git a/gold/testsuite/plugin_new_section_layout.c b/gold/testsuite/plugin_new_section_layout.c
new file mode 100644
index 0000000..7bceae6
--- /dev/null
+++ b/gold/testsuite/plugin_new_section_layout.c
@@ -0,0 +1,182 @@
+/* plugin_new_section_layout.c -- Simple plugin to reorder function sections in
+   plugin-generated objects
+
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   Written by Stephen Crane <sjc@immunant.com>.
+
+   This file is part of gold.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+   MA 02110-1301, USA.  */
+
+/* This plugin tests the new_input API of the linker plugin interface that
+ * allows plugins to modify section layout and assign sections to segments for
+ * sections in plugin-generated object files. It assumes that another plugin is
+ * also in use which will add new files. In practice a plugin is likely to
+ * generate new input files itself in all_symbols_read and want to
+ * reorder/assign sections for these files in the new_input_hook callback. */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include "plugin-api.h"
+#include "elf/common.h"
+
+static ld_plugin_get_input_section_count get_input_section_count = NULL;
+static ld_plugin_get_input_section_type get_input_section_type = NULL;
+static ld_plugin_get_input_section_name get_input_section_name = NULL;
+static ld_plugin_update_section_order update_section_order = NULL;
+static ld_plugin_allow_section_ordering allow_section_ordering = NULL;
+static ld_plugin_allow_unique_segment_for_sections 
+    allow_unique_segment_for_sections = NULL;
+static ld_plugin_unique_segment_for_sections unique_segment_for_sections = NULL;
+
+enum ld_plugin_status onload(struct ld_plugin_tv *tv);
+enum ld_plugin_status new_input_hook(const struct ld_plugin_input_file *file);
+
+/* Plugin entry point.  */
+enum ld_plugin_status
+onload(struct ld_plugin_tv *tv)
+{
+  struct ld_plugin_tv *entry;
+  for (entry = tv; entry->tv_tag != LDPT_NULL; ++entry)
+    {
+      switch (entry->tv_tag)
+        {
+        case LDPT_GET_INPUT_SECTION_COUNT:
+          get_input_section_count = *entry->tv_u.tv_get_input_section_count;
+          break;
+        case LDPT_GET_INPUT_SECTION_TYPE:
+          get_input_section_type = *entry->tv_u.tv_get_input_section_type;
+          break;
+        case LDPT_GET_INPUT_SECTION_NAME:
+          get_input_section_name = *entry->tv_u.tv_get_input_section_name;
+          break;
+	case LDPT_UPDATE_SECTION_ORDER:
+	  update_section_order = *entry->tv_u.tv_update_section_order;
+	  break;
+	case LDPT_ALLOW_SECTION_ORDERING:
+	  allow_section_ordering = *entry->tv_u.tv_allow_section_ordering;
+	  break;
+	case LDPT_ALLOW_UNIQUE_SEGMENT_FOR_SECTIONS:
+	  allow_unique_segment_for_sections
+	      = *entry->tv_u.tv_allow_unique_segment_for_sections;
+	  break;
+	case LDPT_UNIQUE_SEGMENT_FOR_SECTIONS:
+	  unique_segment_for_sections
+	      = *entry->tv_u.tv_unique_segment_for_sections;
+	  break;
+        case LDPT_REGISTER_NEW_INPUT_HOOK:
+          assert((*entry->tv_u.tv_register_new_input) (new_input_hook)
+		 == LDPS_OK);
+          break;
+        default:
+          break;
+        }
+    }
+
+  if (get_input_section_count == NULL
+      || get_input_section_type == NULL
+      || get_input_section_name == NULL
+      || update_section_order == NULL
+      || allow_section_ordering == NULL
+      || allow_unique_segment_for_sections == NULL
+      || unique_segment_for_sections == NULL)
+    {
+      fprintf(stderr, "Some interfaces are missing\n");
+      return LDPS_ERR;
+    }
+
+  /* Inform the linker to prepare for section reordering.  */
+  (*allow_section_ordering)();
+  /* Inform the linker to prepare to map some sections to unique
+     segments.  */
+  (*allow_unique_segment_for_sections)(); 
+
+  return LDPS_OK;
+}
+
+inline static int is_prefix_of(const char *prefix, const char *str)
+{
+  return strncmp(prefix, str, strlen (prefix)) == 0;
+}
+
+/* This function is called by the linker when new files are added by a plugin.
+   We can now tell the linker the desired function order since we have a file
+   handle for the newly added file.  */
+
+enum ld_plugin_status
+new_input_hook(const struct ld_plugin_input_file *file)
+{
+  struct ld_plugin_section section_list[3];
+  int num_entries = 0;
+  unsigned int count;
+
+  if (get_input_section_count(file->handle, &count) != LDPS_OK)
+    return LDPS_ERR;
+
+  unsigned int i;
+  for (i = 0; i < count; ++i)
+  {
+    struct ld_plugin_section section;
+    unsigned int type = 0;
+    char *name = NULL;
+    int position = 3;
+
+    section.handle = file->handle;
+    section.shndx = i;
+
+    if (get_input_section_type(section, &type) != LDPS_OK)
+      return LDPL_FATAL;
+    if (type != SHT_PROGBITS)
+      continue;
+
+    if (get_input_section_name(section, &name))
+      return LDPL_FATAL;
+
+    /* As in plugin_section_order.c, order is foo() followed by bar()
+       followed by baz() */
+    if (is_prefix_of(".text.", name))
+    {
+      if (strstr(name, "_Z3foov") != NULL)
+        position = 0;
+      else if (strstr(name, "_Z3barv") != NULL)
+        position = 1;
+      else if (strstr(name, "_Z3bazv") != NULL)
+        position = 2;
+      else
+        position = 3;
+    }
+    if (position < 3)
+    {
+      section_list[position] = section;
+      num_entries++;
+    }
+  }
+
+  if (num_entries != 3)
+    return LDPL_FATAL;
+
+  update_section_order(section_list, num_entries);
+  unique_segment_for_sections (".text.plugin_created_unique", 0, 0x1000,
+                               section_list, num_entries);
+
+  return LDPS_OK;
+}