[04/15] Mark all machinery needed in early static-link init as -fno-stack-protector.
Commit Message
From: Nick Alcock <nick.alcock@oracle.com>
The startup code in csu/, brk() and sbrk(), and the
__pthread_initialize_tcb_internal() function we just introduced are
needed very early in initialization of a statically-linked program,
before the stack guard is initialized; TLS initialization also uses
memcpy(), which cannot overrun its own stack. Mark all of these as
-fno-stack-protector.
We also finally introduce @libc_cv_ssp@ and @no_stack_protector@, both
substituted by the configury changes made earlier, to detect the case
when -fno-stack-protector is supported by the compiler, and
unconditionally pass it in when this is the case, whether or not
--enable-stack-protector is passed to configure. (This means that
it'll even work when the compiler's been hacked to pass
-fstack-protector by default, unless the hackage is so broken that
it does so in a way that is impossible to override.)
(At one point we marked __libc_fatal() as non-stack-protected too,
but this was pointless: all it did was call other routines which *are*
stack-protected. The earliest __libc_fatal() call is in the
DL_SYSDEP_OSCHECK hook on some platforms, when statically linking:
this is fine, since it is after TLS and stack-canary initialization.
I have tested invocation of programs statically and dynamically
linked against this glibc on older kernels on x86 and ARM, and they
still "work", i.e. fail with the appropriate message.)
v2: No longer mark memcpy() as -fno-stack-protector.
v3: Use $(no-stack-protector).
v4: Use inhibit_stack_protector rather than de-protecting all of nptl-init.c.
v5: Don't stack-protect brk() and sbrk() in the shared library.
v7: Add comment in misc/Makefile. Commit message tweak.
v8: Mark memcpy() as -fstack-protector again, along with wordcpy.
* config.make.in (have-ssp): New.
(no-stack-protector): New.
* csu/Makefile (CFLAGS-.o): Use it.
(CFLAGS-.og): Likewise.
(CFLAGS-.op): Likewise.
(CFLAGS-.os): Likewise.
* misc/Makefile (CFLAGS-sbrk.o): Likewise.
(CFLAGS-sbrk.op): Likewise.
(CFLAGS-sbrk.og): Likewise.
(CFLAGS-brk.o): Likewise.
(CFLAGS-brk.op): Likewise.
(CFLAGS-brk.og): Likewise.
* string/Makefile (CFLAGS-memcpy.c): Likewise.
(CFLAGS-wordcopy.c): Likewise.
* nptl/nptl-init.c [!SHARED] (__pthread_initialize_tcb_internal):
Likewise.
---
config.make.in | 2 ++
csu/Makefile | 5 +++++
misc/Makefile | 9 +++++++++
nptl/nptl-init.c | 1 +
string/Makefile | 4 ++++
5 files changed, 21 insertions(+)
Comments
On 12/19/2016 12:15 PM, Nix wrote:
> +CFLAGS-.og += $(no-stack-protector)
The .og pattern is no more. I will drop those changes from the patch.
Florian
@@ -58,7 +58,9 @@ with-fp = @with_fp@
enable-timezone-tools = @enable_timezone_tools@
unwind-find-fde = @libc_cv_gcc_unwind_find_fde@
have-fpie = @libc_cv_fpie@
+have-ssp = @libc_cv_ssp@
stack-protector = @stack_protector@
+no-stack-protector = @no_stack_protector@
have-selinux = @have_selinux@
have-libaudit = @have_libaudit@
have-libcap = @have_libcap@
@@ -45,6 +45,11 @@ before-compile += $(objpfx)version-info.h
tests := tst-empty tst-atomic tst-atomic-long
tests-static := tst-empty
+CFLAGS-.o += $(no-stack-protector)
+CFLAGS-.og += $(no-stack-protector)
+CFLAGS-.op += $(no-stack-protector)
+CFLAGS-.os += $(no-stack-protector)
+
ifeq (yes,$(build-shared))
extra-objs += S$(start-installed-name) gmon-start.os
ifneq ($(start-installed-name),$(static-start-installed-name))
@@ -105,6 +105,15 @@ CFLAGS-getusershell.c = -fexceptions
CFLAGS-err.c = -fexceptions
CFLAGS-tst-tsearch.c = $(stack-align-test-flags)
+# Called during static library initialization, so turn stack-protection
+# off for non-shared builds.
+CFLAGS-sbrk.o = $(no-stack-protector)
+CFLAGS-sbrk.op = $(no-stack-protector)
+CFLAGS-sbrk.og = $(no-stack-protector)
+CFLAGS-brk.o = $(no-stack-protector)
+CFLAGS-brk.op = $(no-stack-protector)
+CFLAGS-brk.og = $(no-stack-protector)
+
include ../Rules
$(objpfx)libg.a: $(dep-dummy-lib); $(make-dummy-lib)
@@ -287,6 +287,7 @@ static bool __nptl_initial_report_events __attribute_used__;
#ifndef SHARED
void
+inhibit_stack_protector
__pthread_initialize_tcb_internal (void)
{
/* Unlike in the dynamically linked case the dynamic linker has not
@@ -71,6 +71,10 @@ CFLAGS-stratcliff.c = -fno-builtin
CFLAGS-test-ffs.c = -fno-builtin
CFLAGS-tst-inlcall.c = -fno-builtin
+# Called during TLS initialization.
+CFLAGS-memcpy.c = $(no-stack-protector)
+CFLAGS-wordcopy.c = $(no-stack-protector)
+
ifeq ($(run-built-tests),yes)
$(objpfx)tst-svc-cmp.out: tst-svc.expect $(objpfx)tst-svc.out
cmp $^ > $@; \