building GLIBC with -fsanitize=address

[Konstantin Serebryany <konstantin dot s dot serebryany at gmail dot com>]

Hello,

I want to ask some assistance with building the GLIBC with AddressSanitizer
(aka asan, GCC's -fsanitize=address flag).
The end goal is to have libc-asan.so, a shared libc library with code
instrumented by asan.

Simply doing CFLAGS='-g -O1 -fsanitize=address' ../glibc/configure ..
does not work -- it fails at configure time with
configure: error: Need linker with .init_array/.fini_array support.
Even if we bypass this error there will be others and, finally, we
don't want to instrument
every file we build (e.g. there are object files that go into the
ld.so which we don't want to instrument).

One of the things we discussed at the Cauldron was to add a configure
option (e.g. --enable-asan)
similar to the existing --enable-profile which adds the -pg build flag.
This is indeed similar with one major difference: --enable-profile
builds a static libc and
for asan we need a DSO. I've managed to make a patch that builds
libc-asan.a (attached)
but I don't see how to get libc-asan.so from it.

Thoughts?

Thanks,

--kcc

diff --git a/Makeconfig b/Makeconfig
index cef0f06..d2f4506 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -846,7 +846,7 @@ endif
 # The compilation rules use $(CPPFLAGS-${SUFFIX}) and $(CFLAGS-${SUFFIX})
 # to pass different flags for each flavor.
 libtypes = $(foreach o,$(object-suffixes-for-libc),$(libtype$o))
-all-object-suffixes := .o .os .op .og .oS
+all-object-suffixes := .o .os .op .og .oS .oasan
 object-suffixes :=
 CPPFLAGS-.o = $(pic-default)
 CFLAGS-.o = $(filter %frame-pointer,$(+cflags))
@@ -877,6 +877,15 @@ CFLAGS-.op = -pg
 libtype.op = lib%_p.a
 endif
 
+ifeq (yes,$(build-asan))
+# Under --enable-asan, TODO.
+object-suffixes += .op
+CPPFLAGS-.op = $(pic-default)
+CFLAGS-.op = -fsanitize=address
+libtype.op = lib%_asan.a
+endif
+
+
 # Convenience variable for when we want to treat shared-library cases
 # differently from the rest.
 object-suffixes-noshared := $(filter-out .os,$(object-suffixes))
diff --git a/config.make.in b/config.make.in
index 6bcab8a..eef62a9 100644
--- a/config.make.in
+++ b/config.make.in
@@ -82,6 +82,7 @@ nss-crypt = @libc_cv_nss_crypt@
 build-shared = @shared@
 build-pic-default= @libc_cv_pic_default@
 build-profile = @profile@
+build-asan = @asan@
 build-static-nss = @static_nss@
 add-ons = @add_ons@
 add-on-subdirs = @add_on_subdirs@
diff --git a/configure b/configure
index c8d2967..c928def 100755
--- a/configure
+++ b/configure
@@ -576,6 +576,7 @@ mach_interface_list
 DEFINES
 static_nss
 profile
+asan
 libc_cv_pic_default
 shared
 static
@@ -737,6 +738,7 @@ with_default_link
 enable_sanity_checks
 enable_shared
 enable_profile
+enable_asan
 enable_oldest_abi
 enable_hardcoded_path_in_tests
 enable_stackguard_randomization
@@ -1390,6 +1392,8 @@ Optional Features:
                           in special situations) [default=yes]
   --enable-shared         build shared library [default=yes if GNU ld]
   --enable-profile        build profiled library [default=no]
+  --enable-asan           build library instrumented with AddressSanitizer
+                          (ASan) [default=no]
   --enable-oldest-abi=ABI configure the oldest ABI supported [e.g. 2.2]
                           [default=glibc default]
   --enable-hardcoded-path-in-tests
@@ -3431,6 +3435,13 @@ else
   profile=no
 fi
 
+# Check whether --enable-asan was given.
+if test "${enable_asan+set}" = set; then :
+  enableval=$enable_asan; asan=$enableval
+else
+  asan=no
+fi
+
 
 # Check whether --enable-oldest-abi was given.
 if test "${enable_oldest_abi+set}" = set; then :
diff --git a/configure.ac b/configure.ac
index 566ecb2..cb4bae4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -150,6 +150,11 @@ AC_ARG_ENABLE([profile],
 			     [build profiled library @<:@default=no@:>@]),
 	      [profile=$enableval],
 	      [profile=no])
+AC_ARG_ENABLE([asan],
+	      AC_HELP_STRING([--enable-asan],
+			     [build library instrumented with AddressSanitizer (ASan) @<:@default=no@:>@]),
+	      [asan=$enableval],
+	      [asan=no])
 
 AC_ARG_ENABLE([oldest-abi],
 	      AC_HELP_STRING([--enable-oldest-abi=ABI],
@@ -1996,6 +2001,7 @@ rm -f conftest.*])
 AC_SUBST(libc_cv_pic_default)
 
 AC_SUBST(profile)
+AC_SUBST(asan)
 AC_SUBST(static_nss)
 
 AC_SUBST(DEFINES)