Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932881AbcKVK4r (ORCPT ); Tue, 22 Nov 2016 05:56:47 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:7946 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932274AbcKVK4o (ORCPT ); Tue, 22 Nov 2016 05:56:44 -0500 X-Greylist: delayed 429 seconds by postgrey-1.27 at vger.kernel.org; Tue, 22 Nov 2016 05:56:44 EST Message-Id: In-Reply-To: References: From: Christophe Leroy Subject: [PATCH v2 1/2] powerpc: initial stack protector (-fstack-protector) support To: Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Scott Wood Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Nicolas Pitre Date: Tue, 22 Nov 2016 11:49:30 +0100 (CET) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3660 Lines: 109 Partialy copied from commit c743f38013aef ("ARM: initial stack protector (-fstack-protector) support") This is the very basic stuff without the changing canary upon task switch yet. Just the Kconfig option and a constant canary value initialized at boot time. Cc: Nicolas Pitre Signed-off-by: Christophe Leroy --- arch/powerpc/Kconfig | 1 + arch/powerpc/include/asm/stackprotector.h | 40 +++++++++++++++++++++++++++++++ arch/powerpc/kernel/Makefile | 4 ++++ arch/powerpc/kernel/process.c | 6 +++++ 4 files changed, 51 insertions(+) create mode 100644 arch/powerpc/include/asm/stackprotector.h diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index e119aca..6cb449c 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -164,6 +164,7 @@ config PPC select ARCH_HAS_SCALED_CPUTIME if VIRT_CPU_ACCOUNTING_NATIVE select HAVE_ARCH_HARDENED_USERCOPY select HAVE_KERNEL_GZIP + select HAVE_CC_STACKPROTECTOR config GENERIC_CSUM def_bool CPU_LITTLE_ENDIAN diff --git a/arch/powerpc/include/asm/stackprotector.h b/arch/powerpc/include/asm/stackprotector.h new file mode 100644 index 0000000..6720190 --- /dev/null +++ b/arch/powerpc/include/asm/stackprotector.h @@ -0,0 +1,40 @@ +/* + * GCC stack protector support. + * + * Stack protector works by putting predefined pattern at the start of + * the stack frame and verifying that it hasn't been overwritten when + * returning from the function. The pattern is called stack canary + * and gcc expects it to be defined by a global variable called + * "__stack_chk_guard" on PPC. This unfortunately means that on SMP + * we cannot have a different canary value per task. + */ + +#ifndef _ASM_STACKPROTECTOR_H +#define _ASM_STACKPROTECTOR_H + +#include +#include +#include + +extern unsigned long __stack_chk_guard; + +/* + * Initialize the stackprotector canary value. + * + * NOTE: this must only be called from functions that never return, + * and it must always be inlined. + */ +static __always_inline void boot_init_stack_canary(void) +{ + unsigned long canary; + + /* Try to get a semi random initial value. */ + get_random_bytes(&canary, sizeof(canary)); + canary ^= mftb(); + canary ^= LINUX_VERSION_CODE; + + current->stack_canary = canary; + __stack_chk_guard = current->stack_canary; +} + +#endif /* _ASM_STACKPROTECTOR_H */ diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index c3b3717..1d614bd 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -19,6 +19,10 @@ CFLAGS_init.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_btext.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN) +# -fstack-protector triggers protection checks in this code, +# but it is being used too early to link to meaningful stack_chk logic. +CFLAGS_prom_init.o += $(call cc-option, -fno-stack-protector) + ifdef CONFIG_FUNCTION_TRACER # Do not trace early boot code CFLAGS_REMOVE_cputable.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 5dd056d..04885ce 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -64,6 +64,12 @@ #include #include +#ifdef CONFIG_CC_STACKPROTECTOR +#include +unsigned long __stack_chk_guard __read_mostly; +EXPORT_SYMBOL(__stack_chk_guard); +#endif + /* Transactional Memory debug */ #ifdef TM_DEBUG_SW #define TM_DEBUG(x...) printk(KERN_INFO x) -- 2.10.1