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List:       binutils
Subject:    Re: Autoloading lto-plugin path
From:       Alan Modra <amodra () gmail ! com>
Date:       2019-09-26 10:31:22
Message-ID: 20190926101921.GA15102 () bubble ! grove ! modra ! org
[Download RAW message or body]

On Tue, Jan 22, 2019 at 09:09:26PM +0300, Serg Iv via binutils wrote:
> While building cross binutils (for creating win executables on linux) i
> faced the issue that auto-loading LTO plugin won't work for me properly. The
> doc says that ar, nm and so on autoload plugins from ${libdir}/bfd-plugins,
> but the only place where "bfd-plugins" is mentioned is bfd/plugin.c, and
> here we have
> 
> plugin_dir = concat (BINDIR, "/../lib/bfd-plugins", NULL);
> 
> So, the plugins dir depends on BINDIR and doesn't depend on --libdir=...
> actually. Am i right?

Yes, it's a bug.  I had your email sitting in my inbox to remind me
this should be fixed but hadn't gotten around to doing anything until
now.  Also, after I'd fixed the problem I noticed ld.texi disagreed
with binutils.texi and went looking at why that was so, finding
PR24262.

This patch also fixes a possible assignment to has_plugin from an
uninitialised valid_plugin.

bfd/
	PR 24262
	* Makefile.am (AM_CPPFLAGS): Add -DLIBDIR.
	* plugin.c (load_plugin): Search both ${libdir}/bfd-plugins and
	${bindir}/../lib/bfd-plugins if different.
	* Makefile.in: Regenerate.
ld/
	PR 24262
	* ld.texi (-plugin): Revert 2019-03-15 change.

diff --git a/bfd/Makefile.am b/bfd/Makefile.am
index f31a734599..ca868e7c2e 100644
--- a/bfd/Makefile.am
+++ b/bfd/Makefile.am
@@ -53,7 +53,7 @@ ZLIBINC = @zlibinc@
 WARN_CFLAGS = @WARN_CFLAGS@
 NO_WERROR = @NO_WERROR@
 AM_CFLAGS = $(WARN_CFLAGS) $(ZLIBINC)
-AM_CPPFLAGS = -DBINDIR='"$(bindir)"'
+AM_CPPFLAGS = -DBINDIR='"$(bindir)"' -DLIBDIR='"$(libdir)"'
 if PLUGINS
 bfdinclude_HEADERS += $(INCDIR)/plugin-api.h
 LIBDL = @lt_cv_dlopen_libs@
diff --git a/bfd/plugin.c b/bfd/plugin.c
index ca26005055..5f059befb4 100644
--- a/bfd/plugin.c
+++ b/bfd/plugin.c
@@ -367,11 +367,15 @@ register_ld_plugin_object_p (const bfd_target *(*object_p) (bfd *))
 static int
 load_plugin (bfd *abfd)
 {
-  char *plugin_dir;
-  char *p;
-  DIR *d;
-  struct dirent *ent;
+  /* The intent was to search ${libdir}/bfd-plugins for plugins, but
+     unfortunately the original implementation wasn't precisely that
+     when configuring binutils using --libdir.  Search in the proper
+     path first, then the old one for backwards compatibility.  */
+  static const char *path[]
+    = { LIBDIR "/bfd-plugins", BINDIR "/../lib/bfd-plugins" };
+  struct stat last_st;
   int found = 0;
+  unsigned int i;
 
   if (!has_plugin)
     return found;
@@ -382,38 +386,58 @@ load_plugin (bfd *abfd)
   if (plugin_program_name == NULL)
     return found;
 
-  plugin_dir = concat (BINDIR, "/../lib/bfd-plugins", NULL);
-  p = make_relative_prefix (plugin_program_name,
-			    BINDIR,
-			    plugin_dir);
-  free (plugin_dir);
-  plugin_dir = NULL;
-
-  d = opendir (p);
-  if (!d)
-    goto out;
-
-  while ((ent = readdir (d)))
+  /* Try not to search the same dir twice, by looking at st_dev and
+     st_ino for the dir.  If we are on a file system that always sets
+     st_ino to zero or the actual st_ino is zero we might waste some
+     time, but that doesn't matter too much.  */
+  last_st.st_dev = 0;
+  last_st.st_ino = 0;
+  for (i = 0; i < sizeof (path) / sizeof (path[0]); i++)
     {
-      char *full_name;
-      struct stat s;
-      int valid_plugin;
-
-      full_name = concat (p, "/", ent->d_name, NULL);
-      if (stat (full_name, &s) == 0 && S_ISREG (s.st_mode))
-	found = try_load_plugin (full_name, abfd, &valid_plugin);
-      if (has_plugin <= 0)
-	has_plugin = valid_plugin;
-      free (full_name);
+      char *plugin_dir = make_relative_prefix (plugin_program_name,
+					       BINDIR,
+					       path[i]);
+      if (plugin_dir)
+	{
+	  struct stat st;
+	  DIR *d;
+
+	  if (stat (plugin_dir, &st) == 0
+	      && S_ISDIR (st.st_mode)
+	      && !(last_st.st_dev == st.st_dev
+		   && last_st.st_ino == st.st_ino
+		   && st.st_ino != 0)
+	      && (d = opendir (plugin_dir)) != NULL)
+	    {
+	      struct dirent *ent;
+
+	      last_st.st_dev = st.st_dev;
+	      last_st.st_ino = st.st_ino;
+	      while ((ent = readdir (d)) != NULL)
+		{
+		  char *full_name;
+
+		  full_name = concat (plugin_dir, "/", ent->d_name, NULL);
+		  if (stat (full_name, &st) == 0 && S_ISREG (st.st_mode))
+		    {
+		      int valid_plugin;
+
+		      found = try_load_plugin (full_name, abfd, &valid_plugin);
+		      if (has_plugin <= 0)
+			has_plugin = valid_plugin;
+		    }
+		  free (full_name);
+		  if (found)
+		    break;
+		}
+	      closedir (d);
+	    }
+	  free (plugin_dir);
+	}
       if (found)
 	break;
     }
 
- out:
-  free (p);
-  if (d)
-    closedir (d);
-
   return found;
 }
 
diff --git a/ld/ld.texi b/ld/ld.texi
index 2c8a714b19..3b2d05411f 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -855,7 +855,7 @@ Note that the location of the compiler originated plugins is different
 from the place where the @command{ar}, @command{nm} and
 @command{ranlib} programs search for their plugins.  In order for
 those commands to make use of a compiler based plugin it must first be
-copied into the @file{$@{bindir@}/../lib/bfd-plugins} directory.  All gcc
+copied into the @file{$@{libdir@}/bfd-plugins} directory.  All gcc
 based linker plugins are backward compatible, so it is sufficient to
 just copy in the newest one.
 


-- 
Alan Modra
Australia Development Lab, IBM
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