From ed0f941022515ff40473ea5335769a5dc2524a3f Mon Sep 17 00:00:00 2001 From: Yuntao Liu Date: Mon, 3 Jun 2024 16:37:50 +0100 Subject: ARM: 9404/1: arm32: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION The current arm32 architecture does not yet support the HAVE_LD_DEAD_CODE_DATA_ELIMINATION feature. arm32 is widely used in embedded scenarios, and enabling this feature would be beneficial for reducing the size of the kernel image. In order to make this work, we keep the necessary tables by annotating them with KEEP, also it requires further changes to linker script to KEEP some tables and wildcard compiler generated sections into the right place. When using ld.lld for linking, KEEP is not recognized within the OVERLAY command, and Ard proposed a concise method to solve this problem. It boots normally with defconfig, vexpress_defconfig and tinyconfig. The size comparison of zImage is as follows: defconfig vexpress_defconfig tinyconfig 5137712 5138024 424192 no dce 5032560 4997824 298384 dce 2.0% 2.7% 29.7% shrink When using smaller config file, there is a significant reduction in the size of the zImage. We also tested this patch on a commercially available single-board computer, and the comparison is as follows: a15eb_config 2161384 no dce 2092240 dce 3.2% shrink The zImage size has been reduced by approximately 3.2%, which is 70KB on 2.1M. Signed-off-by: Yuntao Liu Tested-by: Arnd Bergmann Reviewed-by: Arnd Bergmann Reviewed-by: Linus Walleij Signed-off-by: Russell King (Oracle) --- drivers/firmware/efi/libstub/Makefile | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/firmware') diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index 06f0428a723c..5a8a9b3429b5 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -56,6 +56,10 @@ KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS)) # disable LTO KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS)) +# The .data section would be renamed to .data.efistub, therefore, remove +# `-fdata-sections` flag from KBUILD_CFLAGS_KERNEL +KBUILD_CFLAGS_KERNEL := $(filter-out -fdata-sections, $(KBUILD_CFLAGS_KERNEL)) + lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ file.o mem.o random.o randomalloc.o pci.o \ skip_spaces.o lib-cmdline.o lib-ctype.o \ -- cgit v1.2.3 From 2335c9cb831faba1a4efcc612886073b6f175fe4 Mon Sep 17 00:00:00 2001 From: Jinjie Ruan Date: Thu, 27 Jun 2024 08:38:44 +0100 Subject: ARM: 9407/1: Add support for STACKLEAK gcc plugin Add the STACKLEAK gcc plugin to arm32 by adding the helper used by stackleak common code: on_thread_stack(). It initialize the stack with the poison value before returning from system calls which improves the kernel security. Additionally, this disables the plugin in EFI stub code and decompress code, which are out of scope for the protection. Before the test on Qemu versatilepb board: # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT lkdtm: Performing direct entry STACKLEAK_ERASING lkdtm: XFAIL: stackleak is not supported on this arch (HAVE_ARCH_STACKLEAK=n) After: # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT lkdtm: Performing direct entry STACKLEAK_ERASING lkdtm: stackleak stack usage: high offset: 80 bytes current: 280 bytes lowest: 696 bytes tracked: 696 bytes untracked: 192 bytes poisoned: 7220 bytes low offset: 4 bytes lkdtm: OK: the rest of the thread stack is properly erased Signed-off-by: Jinjie Ruan Acked-by: Ard Biesheuvel Reviewed-by: Linus Walleij Signed-off-by: Russell King (Oracle) --- arch/arm/Kconfig | 1 + arch/arm/boot/compressed/Makefile | 1 + arch/arm/include/asm/stacktrace.h | 7 +++++++ arch/arm/kernel/entry-common.S | 3 +++ drivers/firmware/efi/libstub/Makefile | 3 ++- 5 files changed, 14 insertions(+), 1 deletion(-) (limited to 'drivers/firmware') diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 08572703d94d..26a01ad4087c 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -86,6 +86,7 @@ config ARM select HAVE_ARCH_PFN_VALID select HAVE_ARCH_SECCOMP select HAVE_ARCH_SECCOMP_FILTER if AEABI && !OABI_COMPAT + select HAVE_ARCH_STACKLEAK select HAVE_ARCH_THREAD_STRUCT_WHITELIST select HAVE_ARCH_TRACEHOOK select HAVE_ARCH_TRANSPARENT_HUGEPAGE if ARM_LPAE diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile index 6bca03c0c7f0..945b5975fce2 100644 --- a/arch/arm/boot/compressed/Makefile +++ b/arch/arm/boot/compressed/Makefile @@ -9,6 +9,7 @@ OBJS = HEAD = head.o OBJS += misc.o decompress.o +CFLAGS_decompress.o += $(DISABLE_STACKLEAK_PLUGIN) ifeq ($(CONFIG_DEBUG_UNCOMPRESS),y) OBJS += debug.o AFLAGS_head.o += -DDEBUG diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h index 360f0d2406bf..f80a85b091d6 100644 --- a/arch/arm/include/asm/stacktrace.h +++ b/arch/arm/include/asm/stacktrace.h @@ -26,6 +26,13 @@ struct stackframe { #endif }; +static inline bool on_thread_stack(void) +{ + unsigned long delta = current_stack_pointer ^ (unsigned long)current->stack; + + return delta < THREAD_SIZE; +} + static __always_inline void arm_get_current_stackframe(struct pt_regs *regs, struct stackframe *frame) { diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index 5c31e9de7a60..f379c852dcb7 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -119,6 +119,9 @@ no_work_pending: ct_user_enter save = 0 +#ifdef CONFIG_GCC_PLUGIN_STACKLEAK + bl stackleak_erase_on_task_stack +#endif restore_user_regs fast = 0, offset = 0 ENDPROC(ret_to_user_from_irq) ENDPROC(ret_to_user) diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile index 5a8a9b3429b5..59d3dccaa8e5 100644 --- a/drivers/firmware/efi/libstub/Makefile +++ b/drivers/firmware/efi/libstub/Makefile @@ -27,7 +27,8 @@ cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_STACKLEAK_PLUGIN) \ cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \ -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \ -DEFI_HAVE_STRCMP -fno-builtin -fpic \ - $(call cc-option,-mno-single-pic-base) + $(call cc-option,-mno-single-pic-base) \ + $(DISABLE_STACKLEAK_PLUGIN) cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax cflags-$(CONFIG_LOONGARCH) += -fpie -- cgit v1.2.3