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authorRomain Naour <romain.naour@gmail.com>2018-09-08 14:41:39 (GMT)
committerThomas Petazzoni <thomas.petazzoni@bootlin.com>2018-11-04 11:49:25 (GMT)
commit435613ef298d49788d82f7bb2e06f944d69d890b (patch)
tree6110416978492439949c477f5ee53275a6a177af
parent03d52226e2f02d642bf3d44ca299cc190cb0b253 (diff)
downloadbuildroot-435613ef298d49788d82f7bb2e06f944d69d890b.tar.gz
buildroot-435613ef298d49788d82f7bb2e06f944d69d890b.tar.bz2
toolchain: disable SSP support if CFI support in binutils is missing
As reported by [1], SSP support is missing in the Buildroot toolchain for microblaze even if it's requested by selecting BR2_TOOLCHAIN_HAS_SSP config option. In Buildroot, we are using libssp provided by the C library (glibc, musl, uClibc-ng) when available. We are not using libssp from gcc. So for a microblaze glibc based toolchain, the SSP support is enabled unconditionally by a select BR2_TOOLCHAIN_HAS_SSP. BR2_microblazeel=y BR2_TOOLCHAIN_BUILDROOT_GLIBC=y BR2_KERNEL_HEADERS_4_14=y BR2_BINUTILS_VERSION_2_30_X=y BR2_GCC_VERSION_8_X=y BR2_TOOLCHAIN_BUILDROOT_CXX=y While building the toolchain, we are building host-binutils which provide "as" (assembler) and host-gcc-initial wich provide a minimal cross gcc (C only cross-compiler without any C library). When SSP support is requested, gcc_cv_libc_provides_ssp=yes is added to the make command line (see [2] for full details) With this setting, the SSP support is requested but it's not available in the end and the toochain build succeed. When the microblaze toolchain is imported to Biuldroot (2018.05) as external toolchain with BR2_TOOLCHAIN_EXTERNAL_HAS_SSP set, the build stop with : "SSP support not available in this toolchain, please disable BR2_TOOLCHAIN_EXTERNAL_HAS_SSP" The test is doing the following command line: echo 'void main(){}' | [...]/host/bin/microblazeel-linux-gcc.br_real -Werror -fstack-protector -x c - -o [...]/build/.br-toolchain-test.tmp cc1: error: -fstack-protector not supported for this target [-Werror] When we look at the gcc-final log file (config.log) we can see this error several time when using the minimal gcc (from host-gcc-initial). So Why the minimal gcc doesn't support SSP? When we look at the gcc-initial log file (config.log) we can see an error with 'as': configure:23194: checking assembler for cfi directives configure:23209: [...]microblazeel-buildroot-linux-gnu/bin/as -o conftest.o conftest.s >&5 conftest.s: Assembler messages: conftest.s:2: Error: CFI is not supported for this target conftest.s:3: Error: CFI is not supported for this target conftest.s:4: Error: CFI is not supported for this target conftest.s:5: Error: CFI is not supported for this target conftest.s:6: Error: CFI is not supported for this target conftest.s:7: Error: CFI is not supported for this target configure:23212: $? = 1 configure: failed program was .text .cfi_startproc .cfi_offset 0, 0 .cfi_same_value 1 .cfi_def_cfa 1, 2 .cfi_escape 1, 2, 3, 4, 5 .cfi_endproc This is the only relevant difference compared to a nios2 toolchain where libssp is enabled and available (nios2 is an example). "CFI" stand for "Control Flow Integrity" and it seems that SSP support requires CFI target support (see [3] for some explanation). The SSP support seems to depends on CFI support, but the toolchain infrastructure is not detailed enough to handle the CFI dependency. The NiosII toolchains built with binutils < 2.30 are also affected by this issue. This patch improve the toolchain infrastructure by adding a new BR2_PACKAGE_HOST_BINUTILS_SUPPORTS_CFI blind option Disable SSP support for microblaze entirely. Disable SSP support for nios2 only with Binutils < 2.30. Fixes: https://gitlab.com/free-electrons/toolchains-builder/-/jobs/72006389 [1] https://gitlab.com/free-electrons/toolchains-builder/issues/1 [2] https://git.buildroot.net/buildroot/tree/package/gcc/gcc.mk?h=2018.05#n275 [3] https://grsecurity.net/rap_faq.php Signed-off-by: Romain Naour <romain.naour@gmail.com> Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com> [Thomas: adjust how the BR2_PACKAGE_HOST_BINUTILS_SUPPORTS_CFI option is expressed.] Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
-rw-r--r--package/binutils/Config.in.host6
-rw-r--r--package/glibc/Config.in2
-rw-r--r--package/musl/Config.in3
-rw-r--r--package/uclibc/Config.in1
4 files changed, 10 insertions, 2 deletions
diff --git a/package/binutils/Config.in.host b/package/binutils/Config.in.host
index c8c02bc..59120f3 100644
--- a/package/binutils/Config.in.host
+++ b/package/binutils/Config.in.host
@@ -1,5 +1,11 @@
comment "Binutils Options"
+config BR2_PACKAGE_HOST_BINUTILS_SUPPORTS_CFI
+ bool
+ default y
+ depends on !BR2_microblaze
+ depends on !(BR2_nios2 && (BR2_BINUTILS_VERSION_2_28_X || BR2_BINUTILS_VERSION_2_29_X))
+
choice
prompt "Binutils Version"
default BR2_BINUTILS_VERSION_2_28_X if BR2_ARM_INSTRUCTIONS_THUMB
diff --git a/package/glibc/Config.in b/package/glibc/Config.in
index 63dd0f4..7821251 100644
--- a/package/glibc/Config.in
+++ b/package/glibc/Config.in
@@ -4,7 +4,7 @@ config BR2_PACKAGE_GLIBC
bool
default y
select BR2_PACKAGE_LINUX_HEADERS
- select BR2_TOOLCHAIN_HAS_SSP
+ select BR2_TOOLCHAIN_HAS_SSP if BR2_PACKAGE_HOST_BINUTILS_SUPPORTS_CFI
help
https://www.gnu.org/software/libc/
endif
diff --git a/package/musl/Config.in b/package/musl/Config.in
index bedc50c..67e9e78 100644
--- a/package/musl/Config.in
+++ b/package/musl/Config.in
@@ -4,6 +4,7 @@ config BR2_PACKAGE_MUSL
depends on BR2_TOOLCHAIN_USES_MUSL
select BR2_PACKAGE_LINUX_HEADERS
# SSP broken on i386/ppc: http://www.openwall.com/lists/musl/2016/12/04/2
- select BR2_TOOLCHAIN_HAS_SSP if !(BR2_i386 || BR2_powerpc)
+ select BR2_TOOLCHAIN_HAS_SSP if BR2_PACKAGE_HOST_BINUTILS_SUPPORTS_CFI \
+ && !(BR2_i386 || BR2_powerpc)
# Compatibility headers: cdefs.h, queue.h
select BR2_PACKAGE_MUSL_COMPAT_HEADERS
diff --git a/package/uclibc/Config.in b/package/uclibc/Config.in
index a566881..de2885b 100644
--- a/package/uclibc/Config.in
+++ b/package/uclibc/Config.in
@@ -70,6 +70,7 @@ config BR2_PTHREAD_DEBUG
config BR2_TOOLCHAIN_BUILDROOT_USE_SSP
bool "Enable stack protection support"
+ depends on BR2_PACKAGE_HOST_BINUTILS_SUPPORTS_CFI
select BR2_TOOLCHAIN_HAS_SSP
help
Enable stack smashing protection support using GCCs