aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--ChangeLog9
-rw-r--r--INSTALL9
-rw-r--r--NEWS9
-rw-r--r--config.h.in3
-rwxr-xr-xconfigure42
-rw-r--r--configure.ac33
-rw-r--r--manual/install.texi8
7 files changed, 113 insertions, 0 deletions
diff --git a/ChangeLog b/ChangeLog
index 4376673..bc0c75c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2016-10-07 Stefan Liebler <stli@linux.vnet.ibm.com>
+
+ * config.h.in (HAVE_GCC_IFUNC): New undef.
+ * configure.ac: Add check if gcc supports attribute ifunc feature.
+ * configure: Regenerated.
+ * manual/install.texi: Add recommendation for gcc with
+ indirect-function support.
+ * INSTALL: Regenerated.
+
2016-10-06 Joseph Myers <joseph@codesourcery.com>
* math/math.h [__GLIBC_USE (IEC_60559_BFP_EXT)] (iseqsig): New
diff --git a/INSTALL b/INSTALL
index 51f26bf..b5acedc 100644
--- a/INSTALL
+++ b/INSTALL
@@ -359,6 +359,15 @@ build the GNU C Library:
better code. As of release time, GCC 5.3 is the newest compiler
verified to work to build the GNU C Library.
+ For multi-arch support it is recommended to use a GCC which has
+ been built with support for GNU indirect functions. This ensures
+ that correct debugging information is generated for functions
+ selected by IFUNC resolvers. This support can either be enabled by
+ configuring GCC with '--enable-gnu-indirect-function', or by
+ enabling it by default by setting 'default_gnu_indirect_function'
+ variable for a particular architecture in the GCC source file
+ 'gcc/config.gcc'.
+
You can use whatever compiler you like to compile programs that use
the GNU C Library.
diff --git a/NEWS b/NEWS
index b5894af..b077d0a 100644
--- a/NEWS
+++ b/NEWS
@@ -76,6 +76,15 @@ Version 2.25
The glibc stub resolver did not support these hooks, but the header file
did not reflect that.
+* For multi-arch support it is recommended to use a GCC which has
+ been built with support for GNU indirect functions. This ensures
+ that correct debugging information is generated for functions
+ selected by IFUNC resolvers. This support can either be enabled by
+ configuring GCC with '--enable-gnu-indirect-function', or by
+ enabling it by default by setting 'default_gnu_indirect_function'
+ variable for a particular architecture in the GCC source file
+ 'gcc/config.gcc'.
+
Security related changes:
On ARM EABI (32-bit), generating a backtrace for execution contexts which
diff --git a/config.h.in b/config.h.in
index 8cd08b0..33757bd 100644
--- a/config.h.in
+++ b/config.h.in
@@ -174,6 +174,9 @@
/* Define to 1 if STT_GNU_IFUNC support actually works. */
#define HAVE_IFUNC 0
+/* Define if gcc supports attribute ifunc. */
+#undef HAVE_GCC_IFUNC
+
/* Define if the linker defines __ehdr_start. */
#undef HAVE_EHDR_START
diff --git a/configure b/configure
index 6ff2527..e80e0ad 100755
--- a/configure
+++ b/configure
@@ -3916,6 +3916,36 @@ fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_ld_gnu_indirect_function" >&5
$as_echo "$libc_cv_ld_gnu_indirect_function" >&6; }
+# Check if gcc supports attribute ifunc as it is used in libc_ifunc macro.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for gcc attribute ifunc support" >&5
+$as_echo_n "checking for gcc attribute ifunc support... " >&6; }
+if ${libc_cv_gcc_indirect_function+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ cat > conftest.c <<EOF
+extern int func (int);
+int used_func (int a)
+{
+ return a;
+}
+static void *resolver ()
+{
+ return &used_func;
+}
+extern __typeof (func) func __attribute__ ((ifunc ("resolver")));
+EOF
+libc_cv_gcc_indirect_function=no
+if ${CC-cc} -c conftest.c -o conftest.o 1>&5 \
+ 2>&5 ; then
+ if $READELF -s conftest.o | grep IFUNC >/dev/null 2>&5; then
+ libc_cv_gcc_indirect_function=yes
+ fi
+fi
+rm -f conftest*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gcc_indirect_function" >&5
+$as_echo "$libc_cv_gcc_indirect_function" >&6; }
+
if test x"$libc_cv_ld_gnu_indirect_function" != xyes; then
if test x"$multi_arch" = xyes; then
as_fn_error $? "--enable-multi-arch support requires assembler and linker support" "$LINENO" 5
@@ -3923,6 +3953,13 @@ if test x"$libc_cv_ld_gnu_indirect_function" != xyes; then
multi_arch=no
fi
fi
+if test x"$libc_cv_gcc_indirect_function" != xyes &&
+ test x"$multi_arch" = xyes; then
+ { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: --enable-multi-arch support recommends a gcc with gnu-indirect-function support.
+Please use a gcc which supports it by default or configure gcc with --enable-gnu-indirect-function" >&5
+$as_echo "$as_me: WARNING: --enable-multi-arch support recommends a gcc with gnu-indirect-function support.
+Please use a gcc which supports it by default or configure gcc with --enable-gnu-indirect-function" >&2;}
+fi
multi_arch_d=
if test x"$multi_arch" != xno; then
multi_arch_d=/multiarch
@@ -6518,6 +6555,11 @@ if test x"$libc_cv_ld_gnu_indirect_function" = xyes; then
fi
+if test x"$libc_cv_gcc_indirect_function" = xyes; then
+ $as_echo "#define HAVE_GCC_IFUNC 1" >>confdefs.h
+
+fi
+
# This is far from the AC_ARG_ENABLE that sets it so that a sysdeps
# configure fragment can override the value to prevent this AC_DEFINE.
diff --git a/configure.ac b/configure.ac
index 9938ab0..a64aeb9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -634,6 +634,30 @@ if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS \
fi
rm -f conftest*])
+# Check if gcc supports attribute ifunc as it is used in libc_ifunc macro.
+AC_CACHE_CHECK([for gcc attribute ifunc support],
+ libc_cv_gcc_indirect_function, [dnl
+cat > conftest.c <<EOF
+extern int func (int);
+int used_func (int a)
+{
+ return a;
+}
+static void *resolver ()
+{
+ return &used_func;
+}
+extern __typeof (func) func __attribute__ ((ifunc ("resolver")));
+EOF
+libc_cv_gcc_indirect_function=no
+if ${CC-cc} -c conftest.c -o conftest.o 1>&AS_MESSAGE_LOG_FD \
+ 2>&AS_MESSAGE_LOG_FD ; then
+ if $READELF -s conftest.o | grep IFUNC >/dev/null 2>&AS_MESSAGE_LOG_FD; then
+ libc_cv_gcc_indirect_function=yes
+ fi
+fi
+rm -f conftest*])
+
if test x"$libc_cv_ld_gnu_indirect_function" != xyes; then
if test x"$multi_arch" = xyes; then
AC_MSG_ERROR([--enable-multi-arch support requires assembler and linker support])
@@ -641,6 +665,11 @@ if test x"$libc_cv_ld_gnu_indirect_function" != xyes; then
multi_arch=no
fi
fi
+if test x"$libc_cv_gcc_indirect_function" != xyes &&
+ test x"$multi_arch" = xyes; then
+ AC_MSG_WARN([--enable-multi-arch support recommends a gcc with gnu-indirect-function support.
+Please use a gcc which supports it by default or configure gcc with --enable-gnu-indirect-function])
+fi
multi_arch_d=
if test x"$multi_arch" != xno; then
multi_arch_d=/multiarch
@@ -1782,6 +1811,10 @@ if test x"$libc_cv_ld_gnu_indirect_function" = xyes; then
AC_DEFINE(HAVE_IFUNC)
fi
+if test x"$libc_cv_gcc_indirect_function" = xyes; then
+ AC_DEFINE(HAVE_GCC_IFUNC)
+fi
+
# This is far from the AC_ARG_ENABLE that sets it so that a sysdeps
# configure fragment can override the value to prevent this AC_DEFINE.
AC_SUBST(use_nscd)
diff --git a/manual/install.texi b/manual/install.texi
index 663f8d5..de1c203 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -402,6 +402,14 @@ the newest version of the compiler that is known to work for building
release time, GCC 5.3 is the newest compiler verified to work to build
@theglibc{}.
+For multi-arch support it is recommended to use a GCC which has been built with
+support for GNU indirect functions. This ensures that correct debugging
+information is generated for functions selected by IFUNC resolvers. This
+support can either be enabled by configuring GCC with
+@samp{--enable-gnu-indirect-function}, or by enabling it by default by setting
+@samp{default_gnu_indirect_function} variable for a particular architecture in
+the GCC source file @file{gcc/config.gcc}.
+
You can use whatever compiler you like to compile programs that use
@theglibc{}.