use -fstack-protector-strong when available
Commit Message
With gcc-4.9, a new -fstack-protector-strong flag is available that is
between -fstack-protector (pretty weak) and -fstack-protector-all (pretty
strong) that provides good trade-offs between overhead but still providing
good coverage. Update the places in glibc that use ssp to use this flag
when it's available.
This also kills off the indirection of hardcoding the flag name in the
Makefiles and adding it based on a have-ssp boolean. Instead, the build
always expands the $(stack-protector) variable to the best ssp setting.
This makes the build logic a bit simpler and allows people to easily set
to a diff flag like:
make stack-protector=-fstack-protector-all
2015-10-19 Mike Frysinger <vapier@gentoo.org>
* config.make.in (have-ssp): Delete.
(stack-protector): New variable.
* configure.ac: Delete libc_cv_ssp export. Add libc_cv_ssp_strong
cache test for -fstack-protector-strong. Export stack_protector to
the best ssp flag.
* configure: Regenerated.
* login/Makefile (pt_chown-cflags): Always add $(stack-protector).
* nscd/Makefile (CFLAGS-nscd): Likewise.
* resolv/Makefile (CFLAGS-libresolv): Likewise.
---
config.make.in | 2 +-
configure | 29 ++++++++++++++++++++++++++++-
configure.ac | 15 ++++++++++++++-
login/Makefile | 4 +---
nscd/Makefile | 4 +---
resolv/Makefile | 4 +---
6 files changed, 46 insertions(+), 12 deletions(-)
Comments
Looks fine, assuming you tested it (which you didn't mention).
On 19 Oct 2015 11:35, Roland McGrath wrote:
> Looks fine, assuming you tested it (which you didn't mention).
i verified the build uses -fstack-protector-strong on these files,
and that resolv/ and inet/ and nscd/ pass their tests still.
-mike
@@ -56,7 +56,7 @@ old-glibc-headers = @old_glibc_headers@
unwind-find-fde = @libc_cv_gcc_unwind_find_fde@
have-forced-unwind = @libc_cv_forced_unwind@
have-fpie = @libc_cv_fpie@
-have-ssp = @libc_cv_ssp@
+stack-protector = @stack_protector@
have-selinux = @have_selinux@
have-libaudit = @have_libaudit@
have-libcap = @have_libcap@
@@ -621,7 +621,7 @@ LIBGD
libc_cv_cc_loop_to_function
libc_cv_cc_submachine
libc_cv_cc_nofma
-libc_cv_ssp
+stack_protector
fno_unit_at_a_time
libc_cv_output_format
libc_cv_hashstyle
@@ -6051,6 +6051,33 @@ fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_ssp" >&5
$as_echo "$libc_cv_ssp" >&6; }
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for -fstack-protector-strong" >&5
+$as_echo_n "checking for -fstack-protector-strong... " >&6; }
+if ${libc_cv_ssp_strong+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -Werror -fstack-protector-strong -xc /dev/null -S -o /dev/null'
+ { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+ (eval $ac_try) 2>&5
+ ac_status=$?
+ $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+ test $ac_status = 0; }; }; then :
+ libc_cv_ssp_strong=yes
+else
+ libc_cv_ssp_strong=no
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_ssp_strong" >&5
+$as_echo "$libc_cv_ssp_strong" >&6; }
+
+stack_protector=
+if test "$libc_cv_ssp_strong" = "yes"; then
+ stack_protector="-fstack-protector-strong"
+elif test "$libc_cv_ssp" = "yes"; then
+ stack_protector="-fstack-protector"
+fi
+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether cc puts quotes around section names" >&5
$as_echo_n "checking whether cc puts quotes around section names... " >&6; }
@@ -1503,7 +1503,20 @@ LIBC_TRY_CC_OPTION([$CFLAGS $CPPFLAGS -Werror -fstack-protector],
[libc_cv_ssp=yes],
[libc_cv_ssp=no])
])
-AC_SUBST(libc_cv_ssp)
+
+AC_CACHE_CHECK(for -fstack-protector-strong, libc_cv_ssp_strong, [dnl
+LIBC_TRY_CC_OPTION([$CFLAGS $CPPFLAGS -Werror -fstack-protector-strong],
+ [libc_cv_ssp_strong=yes],
+ [libc_cv_ssp_strong=no])
+])
+
+stack_protector=
+if test "$libc_cv_ssp_strong" = "yes"; then
+ stack_protector="-fstack-protector-strong"
+elif test "$libc_cv_ssp" = "yes"; then
+ stack_protector="-fstack-protector"
+fi
+AC_SUBST(stack_protector)
AC_CACHE_CHECK(whether cc puts quotes around section names,
libc_cv_have_section_quotes,
@@ -58,9 +58,7 @@ CFLAGS-getpt.c = -fexceptions
ifeq (yesyes,$(have-fpie)$(build-shared))
pt_chown-cflags += $(pie-ccflag)
endif
-ifeq (yes,$(have-ssp))
-pt_chown-cflags += -fstack-protector
-endif
+pt_chown-cflags += $(stack-protector)
ifeq (yes,$(have-libcap))
libcap = -lcap
endif
@@ -84,9 +84,7 @@ CPPFLAGS-nscd += -D_FORTIFY_SOURCE=2
ifeq (yesyes,$(have-fpie)$(build-shared))
CFLAGS-nscd += $(pie-ccflag)
endif
-ifeq (yes,$(have-ssp))
-CFLAGS-nscd += -fstack-protector
-endif
+CFLAGS-nscd += $(stack-protector)
ifeq (yesyes,$(have-fpie)$(build-shared))
LDFLAGS-nscd = -Wl,-z,now
@@ -90,9 +90,7 @@ CPPFLAGS += -Dgethostbyname=res_gethostbyname \
-Dgetnetbyname=res_getnetbyname \
-Dgetnetbyaddr=res_getnetbyaddr
-ifeq (yes,$(have-ssp))
-CFLAGS-libresolv += -fstack-protector
-endif
+CFLAGS-libresolv += $(stack-protector)
CFLAGS-res_hconf.c = -fexceptions
# The BIND code elicits some harmless warnings.