Gentoo: gold/ld: add support for poisoned system directories

This is based on the old CodeSourcery patch written by Joseph Myers to add
support to the link for detecting & rejecting bad -L paths when using a
cross-compiler.  The differences here:
* The command line flags are always available.
* We can turn on & off the warning via the command line.
* The configure option controls the default warning behavior.
* Add support for gold.

It is not currently upstream, nor has it been submitted at all.  There are
no plans to do so currently either.

BUG=chromium:488360
TEST=`cbuildbot chromiumos-sdk` passes  # tests arm/amd64/mipsel/x86
TEST=`cbuildbot panther_moblab-full whirlwind-release` pass
TEST=`cbuildbot {x32,arm64}-generic-full` has no new failures
TEST=x86_64-cros-linux-gnu-ld throws warnings when using -L/lib (gold & bfd)

Reviewed-on: https://chromium-review.googlesource.com/272083
(cherry picked from commit f92dbf35c00ab13cee36f6be8ae5ca46454d9000)
(cherry picked from commit bcf3dcf1c50ff2a9368cd74f377d4c0657324246)

11 files changed, 146 insertions, 0 deletions

diff --git a/gold/options.cc b/gold/options.cc
index d92394120a5..d221a012c49 100644
--- a/gold/options.cc
+++ b/gold/options.cc
@@ -1290,6 +1290,39 @@ General_options::finalize()
   // in the path, as appropriate.
   this->add_sysroot();
 
+  // Now check if library_path is poisoned.
+  if (this->warn_poison_system_directories())
+    {
+      std::vector<std::string> bad_paths;
+
+      bad_paths.push_back("/lib");
+      // TODO: This check is disabled for now due to a bunch of packages that
+      // use libtool and relink with -L/usr/lib paths (albeit after the right
+      // sysroot path).  Once those are fixed we can enable.
+      // We also need to adjust it so it only rejects one or two levels deep.
+      // Gcc's internal paths also live below /usr/lib.
+      // http://crbug.com/488360
+      // bad_paths.push_back("/usr/lib");
+      bad_paths.push_back("/usr/local/lib");
+      bad_paths.push_back("/usr/X11R6/lib");
+
+      for (std::vector<std::string>::const_iterator b = bad_paths.begin();
+	   b != bad_paths.end();
+	   ++b)
+	for (Dir_list::iterator p = this->library_path_.value.begin();
+	     p != this->library_path_.value.end();
+	     ++p)
+	  if (!p->name().compare(0, b->size(), *b))
+	    {
+	      if (this->error_poison_system_directories())
+		gold_fatal(_("library search path \"%s\" is unsafe for "
+			     "cross-compilation"), p->name().c_str());
+	      else
+		gold_warning(_("library search path \"%s\" is unsafe for "
+			       "cross-compilation"), p->name().c_str());
+	    }
+    }
+
   // Now that we've normalized the options, check for contradictory ones.
   if (this->shared() && this->is_static())
     gold_fatal(_("-shared and -static are incompatible"));
diff --git a/gold/options.h b/gold/options.h
index f7c127953c2..f0fdcb1fc11 100644
--- a/gold/options.h
+++ b/gold/options.h
@@ -1375,6 +1375,13 @@ class General_options
   DEFINE_bool(warn_multiple_gp, options::TWO_DASHES, '\0', false,
 	      N_("Ignored"), NULL);
 
+  DEFINE_bool(warn_poison_system_directories, options::TWO_DASHES, '\0', false,
+	      N_("Warn for -L options using system directories"),
+	      N_("Do not warn for -L options using system directories"));
+  DEFINE_bool(error_poison_system_directories, options::TWO_DASHES, '\0', false,
+	      N_("Give an error for -L options using system directories"),
+	      NULL);
+
   DEFINE_bool(warn_search_mismatch, options::TWO_DASHES, '\0', true,
 	      N_("Warn when skipping an incompatible library"),
 	      N_("Don't warn when skipping an incompatible library"));
diff --git a/ld/config.in b/ld/config.in
index d93c9b08300..5da2742beac 100644
--- a/ld/config.in
+++ b/ld/config.in
@@ -31,6 +31,9 @@
    language is requested. */
 #undef ENABLE_NLS
 
+/* Define to warn for use of native system library directories */
+#undef ENABLE_POISON_SYSTEM_DIRECTORIES
+
 /* Additional extension a shared object might have. */
 #undef EXTRA_SHLIB_EXTENSION
 
diff --git a/ld/configure b/ld/configure
index b532ef94fa2..65d12cbf883 100755
--- a/ld/configure
+++ b/ld/configure
@@ -823,6 +823,7 @@ with_lib_path
 enable_targets
 enable_64_bit_bfd
 with_sysroot
+enable_poison_system_directories
 enable_gold
 enable_got
 enable_compressed_debug_sections
@@ -1487,6 +1488,8 @@ Optional Features:
   --disable-largefile     omit support for large files
   --enable-targets        alternative target configurations
   --enable-64-bit-bfd     64-bit support (on hosts with narrower word sizes)
+  --enable-poison-system-directories
+                          warn for use of native system library directories
   --enable-gold[=ARG]     build gold [ARG={default,yes,no}]
   --enable-got=<type>     GOT handling scheme (target, single, negative,
                           multigot)
@@ -15804,7 +15807,18 @@ else
 fi
 
 
+# Check whether --enable-poison-system-directories was given.
+if test "${enable_poison_system_directories+set}" = set; then :
+  enableval=$enable_poison_system_directories;
+else
+  enable_poison_system_directories=no
+fi
+
+if test "x${enable_poison_system_directories}" = "xyes"; then
 
+$as_echo "#define ENABLE_POISON_SYSTEM_DIRECTORIES 1" >>confdefs.h
+
+fi
 
 # Check whether --enable-got was given.
 if test "${enable_got+set}" = set; then :
diff --git a/ld/configure.ac b/ld/configure.ac
index ee62d10ac58..bc3e14e729d 100644
--- a/ld/configure.ac
+++ b/ld/configure.ac
@@ -94,6 +94,16 @@ AC_SUBST(use_sysroot)
 AC_SUBST(TARGET_SYSTEM_ROOT)
 AC_SUBST(TARGET_SYSTEM_ROOT_DEFINE)
 
+AC_ARG_ENABLE([poison-system-directories],
+         AS_HELP_STRING([--enable-poison-system-directories],
+                [warn for use of native system library directories]),,
+         [enable_poison_system_directories=no])
+if test "x${enable_poison_system_directories}" = "xyes"; then
+  AC_DEFINE([ENABLE_POISON_SYSTEM_DIRECTORIES],
+       [1],
+       [Define to warn for use of native system library directories])
+fi
+
 dnl Use --enable-gold to decide if this linker should be the default.
 dnl "install_as_default" is set to false if gold is the default linker.
 dnl "installed_linker" is the installed BFD linker name.
diff --git a/ld/ld.h b/ld/ld.h
index 55078a9637b..bceda0e1e7b 100644
--- a/ld/ld.h
+++ b/ld/ld.h
@@ -180,6 +180,13 @@ typedef struct
      in the linker script.  */
   bfd_boolean force_group_allocation;
 
+  /* If TRUE warn for uses of system directories when cross linking.  */
+  bfd_boolean warn_poison_system_directories;
+
+  /* If TRUE (default FALSE) give an error for uses of system
+     directories when cross linking instead of a warning.  */
+  bfd_boolean error_poison_system_directories;
+
   /* Big or little endian as set on command line.  */
   enum endian_enum endian;
 
diff --git a/ld/ld.texi b/ld/ld.texi
index ad2537454c1..91886f0d68b 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -2561,6 +2561,24 @@ string identifying the original linked file does not change.
 
 Passing @code{none} for @var{style} disables the setting from any
 @code{--build-id} options earlier on the command line.
+
+@kindex --warn-poison-system-directories
+@item --warn-poison-system-directories
+Warn for @option{-L} options using system directories such as
+@file{/usr/lib} when cross linking.  This option is intended for use
+in environments that want to detect and reject incorrect link settings.
+
+@kindex --no-warn-poison-system-directories
+@item --no-warn-poison-system-directories
+Do not warn for @option{-L} options using system directories such as
+@file{/usr/lib} when cross linking.  This option is intended for use
+in chroot environments when such directories contain the correct
+libraries for the target system rather than the host.
+
+@kindex --error-poison-system-directories
+@item --error-poison-system-directories
+Give an error instead of a warning for @option{-L} options using
+system directories when cross linking.
 @end table
 
 @c man end
diff --git a/ld/ldfile.c b/ld/ldfile.c
index 7f60319390e..baf736f8223 100644
--- a/ld/ldfile.c
+++ b/ld/ldfile.c
@@ -116,6 +116,26 @@ ldfile_add_library_path (const char *name, bfd_boolean cmdline)
     new_dirs->name = concat (ld_sysroot, name + strlen ("$SYSROOT"), (const char *) NULL);
   else
     new_dirs->name = xstrdup (name);
+
+  if (command_line.warn_poison_system_directories
+      && (!strncmp (name, "/lib", 4)
+      /* TODO: This check is disabled for now due to a bunch of packages that
+       * use libtool and relink with -L/usr/lib paths (albeit after the right
+       * sysroot path).  Once those are fixed we can enable.
+       * We also need to adjust it so it only rejects one or two levels deep.
+       * Gcc's internal paths also live below /usr/lib.
+       * http://crbug.com/488360  */
+	  /* || !strncmp (name, "/usr/lib", 8) */
+	  || !strncmp (name, "/usr/local/lib", 14)
+	  || !strncmp (name, "/usr/X11R6/lib", 14)))
+    {
+      if (command_line.error_poison_system_directories)
+	einfo (_("%X%P: error: library search path \"%s\" is unsafe for "
+	         "cross-compilation\n"), name);
+      else
+	einfo (_("%P: warning: library search path \"%s\" is unsafe for "
+	         "cross-compilation\n"), name);
+    }
 }
 
 /* Try to open a BFD for a lang_input_statement.  */
diff --git a/ld/ldlex.h b/ld/ldlex.h
index 96f88bc3651..c15e8818127 100644
--- a/ld/ldlex.h
+++ b/ld/ldlex.h
@@ -142,6 +142,9 @@ enum option_values
   OPTION_PRINT_OUTPUT_FORMAT,
   OPTION_PRINT_SYSROOT,
   OPTION_IGNORE_UNRESOLVED_SYMBOL,
+  OPTION_WARN_POISON_SYSTEM_DIRECTORIES,
+  OPTION_NO_WARN_POISON_SYSTEM_DIRECTORIES,
+  OPTION_ERROR_POISON_SYSTEM_DIRECTORIES,
   OPTION_PUSH_STATE,
   OPTION_POP_STATE,
   OPTION_DISABLE_MULTIPLE_DEFS_ABS,
diff --git a/ld/ldmain.c b/ld/ldmain.c
index 335334444b0..6f3cbe293eb 100644
--- a/ld/ldmain.c
+++ b/ld/ldmain.c
@@ -270,6 +270,13 @@ main (int argc, char **argv)
   command_line.warn_mismatch = TRUE;
   command_line.warn_search_mismatch = TRUE;
   command_line.check_section_addresses = -1;
+  command_line.warn_poison_system_directories =
+#ifdef ENABLE_POISON_SYSTEM_DIRECTORIES
+    TRUE;
+#else
+    FALSE;
+#endif
+  command_line.error_poison_system_directories = FALSE;
 
   /* We initialize DEMANGLING based on the environment variable
      COLLECT_NO_DEMANGLE.  The gcc collect2 program will demangle the
diff --git a/ld/lexsup.c b/ld/lexsup.c
index a6c72b9e3be..68fff8e9343 100644
--- a/ld/lexsup.c
+++ b/ld/lexsup.c
@@ -535,6 +535,18 @@ static const struct ld_option ld_options[] =
     OPTION_IGNORE_UNRESOLVED_SYMBOL},
     '\0', N_("SYMBOL"),
     N_("Unresolved SYMBOL will not cause an error or warning"), TWO_DASHES },
+  { {"warn-poison-system-directories", no_argument, NULL,
+     OPTION_WARN_POISON_SYSTEM_DIRECTORIES},
+    '\0', NULL, N_("Warn for -L options using system directories"),
+    TWO_DASHES },
+  { {"no-warn-poison-system-directories", no_argument, NULL,
+     OPTION_NO_WARN_POISON_SYSTEM_DIRECTORIES},
+    '\0', NULL, N_("Do not warn for -L options using system directories"),
+    TWO_DASHES },
+  { {"error-poison-system-directories", no_argument, NULL,
+     OPTION_ERROR_POISON_SYSTEM_DIRECTORIES},
+    '\0', NULL, N_("Give an error for -L options using system directories"),
+    TWO_DASHES },
   { {"push-state", no_argument, NULL, OPTION_PUSH_STATE},
     '\0', NULL, N_("Push state of flags governing input file handling"),
     TWO_DASHES },
@@ -1555,6 +1567,18 @@ parse_args (unsigned argc, char **argv)
 	  }
 	  break;
 
+   case OPTION_WARN_POISON_SYSTEM_DIRECTORIES:
+     command_line.warn_poison_system_directories = TRUE;
+     break;
+
+   case OPTION_NO_WARN_POISON_SYSTEM_DIRECTORIES:
+     command_line.warn_poison_system_directories = FALSE;
+     break;
+
+   case OPTION_ERROR_POISON_SYSTEM_DIRECTORIES:
+     command_line.error_poison_system_directories = TRUE;
+     break;
+
 	case OPTION_PUSH_STATE:
 	  input_flags.pushed = xmemdup (&input_flags,
 					sizeof (input_flags),