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[PATCH] detect broken linker handling of __ehdr_start
- From: Mike Frysinger <vapier at gentoo dot org>
- To: libc-alpha at sourceware dot org
- Date: Wed, 6 Aug 2014 23:47:23 -0400
- Subject: [PATCH] detect broken linker handling of __ehdr_start
- Authentication-results: sourceware.org; auth=none
- References: <20140311222933 dot CC24274474 at topped-with-meat dot com>
Older versions of ld on ia64 support __ehdr_start, but generate relocs
when they shouldn't. This causes the ld.so to not run because it tries
to resolve the __ehdr_start symbol (but it's not exported).
2014-08-06 Mike Frysinger <vapier@gentoo.org>
* configure.ac: Change __ehdr_start code to dereference the struct.
Run readelf on the output to look for relocations.
* configure: Regenerated.
---
Tested ia64 binutils 2.23.2 & 2.24, and x86_64 binutils 2.23.2 & 2.24.
configure | 26 ++++++++++++++++++++------
configure.ac | 23 ++++++++++++++++++-----
2 files changed, 38 insertions(+), 11 deletions(-)
diff --git a/configure b/configure
index 646e0bc..86ba307 100755
--- a/configure
+++ b/configure
@@ -6965,8 +6965,11 @@ if test $libc_cv_predef_stack_protector = yes; then
fi
libc_extra_cppflags=
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the linker provides __ehdr_start" >&5
-$as_echo_n "checking whether the linker provides __ehdr_start... " >&6; }
+# Some linkers on some architectures support __ehdr_start but with
+# bugs. Make sure usage of it does not create relocations in the
+# output (as the linker should resolve them all for us).
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the linker provides working __ehdr_start" >&5
+$as_echo_n "checking whether the linker provides working __ehdr_start... " >&6; }
if ${libc_cv_ehdr_start+:} false; then :
$as_echo_n "(cached) " >&6
else
@@ -6980,12 +6983,20 @@ LIBS=
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
-extern const char __ehdr_start __attribute__ ((visibility ("hidden")));
-const char *ehdr (void) { return &__ehdr_start; }
+typedef struct {
+ char foo;
+ long val;
+} Ehdr;
+extern const Ehdr __ehdr_start __attribute__ ((visibility ("hidden")));
+long ehdr (void) { return __ehdr_start.val; }
_ACEOF
if ac_fn_c_try_link "$LINENO"; then :
- libc_cv_ehdr_start=yes
+ if $READELF -r conftest | fgrep __ehdr_start >/dev/null; then
+ libc_cv_ehdr_start=broken
+ else
+ libc_cv_ehdr_start=yes
+ fi
else
libc_cv_ehdr_start=no
fi
@@ -6998,9 +7009,12 @@ LIBS="$old_LIBS"
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_ehdr_start" >&5
$as_echo "$libc_cv_ehdr_start" >&6; }
-if test $libc_cv_ehdr_start = yes; then
+if test "$libc_cv_ehdr_start" = yes; then
$as_echo "#define HAVE_EHDR_START 1" >>confdefs.h
+elif test "$libc_cv_ehdr_start" = broken; then
+ { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: linker is broken -- you should upgrade" >&5
+$as_echo "$as_me: WARNING: linker is broken -- you should upgrade" >&2;}
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_trap with no external dependencies" >&5
diff --git a/configure.ac b/configure.ac
index e89faa0..2553399 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1880,7 +1880,10 @@ if test $libc_cv_predef_stack_protector = yes; then
fi
libc_extra_cppflags=
-AC_CACHE_CHECK([whether the linker provides __ehdr_start],
+# Some linkers on some architectures support __ehdr_start but with
+# bugs. Make sure usage of it does not create relocations in the
+# output (as the linker should resolve them all for us).
+AC_CACHE_CHECK([whether the linker provides working __ehdr_start],
libc_cv_ehdr_start, [
old_CFLAGS="$CFLAGS"
old_LDFLAGS="$LDFLAGS"
@@ -1889,16 +1892,26 @@ CFLAGS="$CFLAGS -fPIC"
LDFLAGS="$LDFLAGS -nostdlib -nostartfiles -shared"
LIBS=
AC_LINK_IFELSE([AC_LANG_SOURCE([
-extern const char __ehdr_start __attribute__ ((visibility ("hidden")));
-const char *ehdr (void) { return &__ehdr_start; }
+typedef struct {
+ char foo;
+ long val;
+} Ehdr;
+extern const Ehdr __ehdr_start __attribute__ ((visibility ("hidden")));
+long ehdr (void) { return __ehdr_start.val; }
])],
- [libc_cv_ehdr_start=yes], [libc_cv_ehdr_start=no])
+ [if $READELF -r conftest | fgrep __ehdr_start >/dev/null; then
+ libc_cv_ehdr_start=broken
+ else
+ libc_cv_ehdr_start=yes
+ fi], [libc_cv_ehdr_start=no])
CFLAGS="$old_CFLAGS"
LDFLAGS="$old_LDFLAGS"
LIBS="$old_LIBS"
])
-if test $libc_cv_ehdr_start = yes; then
+if test "$libc_cv_ehdr_start" = yes; then
AC_DEFINE([HAVE_EHDR_START])
+elif test "$libc_cv_ehdr_start" = broken; then
+ AC_MSG_WARN([linker is broken -- you should upgrade])
fi
AC_CACHE_CHECK(for __builtin_trap with no external dependencies,
--
2.0.0