* [PATCH v4 04/10] x86: Makefile: Add build and config option for CONFIG_FG_KASLR [not found] <20200717170008.5949-1-kristen@linux.intel.com> @ 2020-07-17 17:00 ` Kristen Carlson Accardi 2020-07-17 17:00 ` Kristen Carlson Accardi 2020-07-17 17:00 ` [PATCH v4 05/10] x86: Make sure _etext includes function sections Kristen Carlson Accardi 1 sibling, 1 reply; 4+ messages in thread From: Kristen Carlson Accardi @ 2020-07-17 17:00 UTC (permalink / raw) To: keescook, tglx, mingo, bp, Masahiro Yamada, Michal Marek, x86, H. Peter Anvin, Arnd Bergmann Cc: arjan, linux-kernel, kernel-hardening, rick.p.edgecombe, Kristen Carlson Accardi, Tony Luck, linux-kbuild, linux-arch Allow user to select CONFIG_FG_KASLR if dependencies are met. Change the make file to build with -ffunction-sections if CONFIG_FG_KASLR. While the only architecture that supports CONFIG_FG_KASLR does not currently enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION, make sure these 2 features play nicely together for the future by ensuring that if CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is selected when used with CONFIG_FG_KASLR the function sections will not be consolidated back into .text. Thanks to Kees Cook for the dead code elimination changes. Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Tony Luck <tony.luck@intel.com> --- Makefile | 6 +++++- arch/x86/Kconfig | 4 ++++ include/asm-generic/vmlinux.lds.h | 16 ++++++++++++++-- init/Kconfig | 14 ++++++++++++++ 4 files changed, 37 insertions(+), 3 deletions(-) diff --git a/Makefile b/Makefile index 0b5f8538bde5..66427b12de53 100644 --- a/Makefile +++ b/Makefile @@ -872,7 +872,7 @@ KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once) endif ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION -KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections +KBUILD_CFLAGS_KERNEL += -fdata-sections LDFLAGS_vmlinux += --gc-sections endif @@ -880,6 +880,10 @@ ifdef CONFIG_LIVEPATCH KBUILD_CFLAGS += $(call cc-option, -flive-patching=inline-clone) endif +ifneq ($(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION)$(CONFIG_FG_KASLR),) +KBUILD_CFLAGS += -ffunction-sections +endif + ifdef CONFIG_SHADOW_CALL_STACK CC_FLAGS_SCS := -fsanitize=shadow-call-stack KBUILD_CFLAGS += $(CC_FLAGS_SCS) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 883da0abf779..e7a2db3e270d 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -372,6 +372,10 @@ config CC_HAS_SANE_STACKPROTECTOR We have to make sure stack protector is unconditionally disabled if the compiler produces broken code. +config ARCH_HAS_FG_KASLR + def_bool y + depends on RANDOMIZE_BASE && X86_64 + menu "Processor type and features" config ZONE_DMA diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index db600ef218d7..a5552cf28d5d 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -93,14 +93,12 @@ * sections to be brought in with rodata. */ #ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION -#define TEXT_MAIN .text .text.[0-9a-zA-Z_]* #define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX* #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]* #define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* #define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* #define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]* #else -#define TEXT_MAIN .text #define DATA_MAIN .data #define SDATA_MAIN .sdata #define RODATA_MAIN .rodata @@ -108,6 +106,20 @@ #define SBSS_MAIN .sbss #endif +/* + * Both LD_DEAD_CODE_DATA_ELIMINATION and CONFIG_FG_KASLR options enable + * -ffunction-sections, which produces separately named .text sections. In + * the case of CONFIG_FG_KASLR, they need to stay distict so they can be + * separately randomized. Without CONFIG_FG_KASLR, the separate .text + * sections can be collected back into a common section, which makes the + * resulting image slightly smaller + */ +#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) && !defined(CONFIG_FG_KASLR) +#define TEXT_MAIN .text .text.[0-9a-zA-Z_]* +#else +#define TEXT_MAIN .text +#endif + /* * Align to a 32 byte boundary equal to the * alignment gcc 4.5 uses for a struct diff --git a/init/Kconfig b/init/Kconfig index 0498af567f70..82f042a1062f 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1990,6 +1990,20 @@ config PROFILING config TRACEPOINTS bool +config FG_KASLR + bool "Function Granular Kernel Address Space Layout Randomization" + depends on $(cc-option, -ffunction-sections) + depends on ARCH_HAS_FG_KASLR + default n + help + This option improves the randomness of the kernel text + over basic Kernel Address Space Layout Randomization (KASLR) + by reordering the kernel text at boot time. This feature + uses information generated at compile time to re-layout the + kernel text section at boot time at function level granularity. + + If unsure, say N. + endmenu # General setup source "arch/Kconfig" -- 2.20.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v4 04/10] x86: Makefile: Add build and config option for CONFIG_FG_KASLR 2020-07-17 17:00 ` [PATCH v4 04/10] x86: Makefile: Add build and config option for CONFIG_FG_KASLR Kristen Carlson Accardi @ 2020-07-17 17:00 ` Kristen Carlson Accardi 0 siblings, 0 replies; 4+ messages in thread From: Kristen Carlson Accardi @ 2020-07-17 17:00 UTC (permalink / raw) To: keescook, tglx, mingo, bp, Masahiro Yamada, Michal Marek, x86, H. Peter Anvin, Arnd Bergmann Cc: arjan, linux-kernel, kernel-hardening, rick.p.edgecombe, Kristen Carlson Accardi, Tony Luck, linux-kbuild, linux-arch Allow user to select CONFIG_FG_KASLR if dependencies are met. Change the make file to build with -ffunction-sections if CONFIG_FG_KASLR. While the only architecture that supports CONFIG_FG_KASLR does not currently enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION, make sure these 2 features play nicely together for the future by ensuring that if CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is selected when used with CONFIG_FG_KASLR the function sections will not be consolidated back into .text. Thanks to Kees Cook for the dead code elimination changes. Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> Reviewed-by: Kees Cook <keescook@chromium.org> Tested-by: Tony Luck <tony.luck@intel.com> --- Makefile | 6 +++++- arch/x86/Kconfig | 4 ++++ include/asm-generic/vmlinux.lds.h | 16 ++++++++++++++-- init/Kconfig | 14 ++++++++++++++ 4 files changed, 37 insertions(+), 3 deletions(-) diff --git a/Makefile b/Makefile index 0b5f8538bde5..66427b12de53 100644 --- a/Makefile +++ b/Makefile @@ -872,7 +872,7 @@ KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once) endif ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION -KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections +KBUILD_CFLAGS_KERNEL += -fdata-sections LDFLAGS_vmlinux += --gc-sections endif @@ -880,6 +880,10 @@ ifdef CONFIG_LIVEPATCH KBUILD_CFLAGS += $(call cc-option, -flive-patching=inline-clone) endif +ifneq ($(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION)$(CONFIG_FG_KASLR),) +KBUILD_CFLAGS += -ffunction-sections +endif + ifdef CONFIG_SHADOW_CALL_STACK CC_FLAGS_SCS := -fsanitize=shadow-call-stack KBUILD_CFLAGS += $(CC_FLAGS_SCS) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 883da0abf779..e7a2db3e270d 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -372,6 +372,10 @@ config CC_HAS_SANE_STACKPROTECTOR We have to make sure stack protector is unconditionally disabled if the compiler produces broken code. +config ARCH_HAS_FG_KASLR + def_bool y + depends on RANDOMIZE_BASE && X86_64 + menu "Processor type and features" config ZONE_DMA diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index db600ef218d7..a5552cf28d5d 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -93,14 +93,12 @@ * sections to be brought in with rodata. */ #ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION -#define TEXT_MAIN .text .text.[0-9a-zA-Z_]* #define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX* #define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]* #define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* #define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* #define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]* #else -#define TEXT_MAIN .text #define DATA_MAIN .data #define SDATA_MAIN .sdata #define RODATA_MAIN .rodata @@ -108,6 +106,20 @@ #define SBSS_MAIN .sbss #endif +/* + * Both LD_DEAD_CODE_DATA_ELIMINATION and CONFIG_FG_KASLR options enable + * -ffunction-sections, which produces separately named .text sections. In + * the case of CONFIG_FG_KASLR, they need to stay distict so they can be + * separately randomized. Without CONFIG_FG_KASLR, the separate .text + * sections can be collected back into a common section, which makes the + * resulting image slightly smaller + */ +#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) && !defined(CONFIG_FG_KASLR) +#define TEXT_MAIN .text .text.[0-9a-zA-Z_]* +#else +#define TEXT_MAIN .text +#endif + /* * Align to a 32 byte boundary equal to the * alignment gcc 4.5 uses for a struct diff --git a/init/Kconfig b/init/Kconfig index 0498af567f70..82f042a1062f 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1990,6 +1990,20 @@ config PROFILING config TRACEPOINTS bool +config FG_KASLR + bool "Function Granular Kernel Address Space Layout Randomization" + depends on $(cc-option, -ffunction-sections) + depends on ARCH_HAS_FG_KASLR + default n + help + This option improves the randomness of the kernel text + over basic Kernel Address Space Layout Randomization (KASLR) + by reordering the kernel text at boot time. This feature + uses information generated at compile time to re-layout the + kernel text section at boot time at function level granularity. + + If unsure, say N. + endmenu # General setup source "arch/Kconfig" -- 2.20.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v4 05/10] x86: Make sure _etext includes function sections [not found] <20200717170008.5949-1-kristen@linux.intel.com> 2020-07-17 17:00 ` [PATCH v4 04/10] x86: Makefile: Add build and config option for CONFIG_FG_KASLR Kristen Carlson Accardi @ 2020-07-17 17:00 ` Kristen Carlson Accardi 2020-07-17 17:00 ` Kristen Carlson Accardi 1 sibling, 1 reply; 4+ messages in thread From: Kristen Carlson Accardi @ 2020-07-17 17:00 UTC (permalink / raw) To: keescook, tglx, mingo, bp, x86, H. Peter Anvin, Arnd Bergmann Cc: arjan, linux-kernel, kernel-hardening, rick.p.edgecombe, Kristen Carlson Accardi, Tony Luck, linux-arch When using -ffunction-sections to place each function in it's own text section so it can be randomized at load time, the linker considers these .text.* sections "orphaned sections", and will place them after the first similar section (.text). In order to accurately represent the end of the text section and the orphaned sections, _etext must be moved so that it is after both .text and .text.* The text size must also be calculated to include .text AND .text.* Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> Tested-by: Tony Luck <tony.luck@intel.com> Reviewed-by: Kees Cook <keescook@chromium.org> --- arch/x86/kernel/vmlinux.lds.S | 17 +++++++++++++++-- include/asm-generic/vmlinux.lds.h | 2 +- 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 3bfc8dd8a43d..e8da7eeb4d8d 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -146,9 +146,22 @@ SECTIONS #endif } :text =0xcccc - /* End of text section, which should occupy whole number of pages */ - _etext = .; + /* + * -ffunction-sections creates .text.* sections, which are considered + * "orphan sections" and added after the first similar section (.text). + * Placing this ALIGN statement before _etext causes the address of + * _etext to be below that of all the .text.* orphaned sections + */ . = ALIGN(PAGE_SIZE); + _etext = .; + + /* + * the size of the .text section is used to calculate the address + * range for orc lookups. If we just use SIZEOF(.text), we will + * miss all the .text.* sections. Calculate the size using _etext + * and _stext and save the value for later. + */ + text_size = _etext - _stext; X86_ALIGN_RODATA_BEGIN RO_DATA(PAGE_SIZE) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index a5552cf28d5d..34eab6513fdc 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -835,7 +835,7 @@ . = ALIGN(4); \ .orc_lookup : AT(ADDR(.orc_lookup) - LOAD_OFFSET) { \ orc_lookup = .; \ - . += (((SIZEOF(.text) + LOOKUP_BLOCK_SIZE - 1) / \ + . += (((text_size + LOOKUP_BLOCK_SIZE - 1) / \ LOOKUP_BLOCK_SIZE) + 1) * 4; \ orc_lookup_end = .; \ } -- 2.20.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v4 05/10] x86: Make sure _etext includes function sections 2020-07-17 17:00 ` [PATCH v4 05/10] x86: Make sure _etext includes function sections Kristen Carlson Accardi @ 2020-07-17 17:00 ` Kristen Carlson Accardi 0 siblings, 0 replies; 4+ messages in thread From: Kristen Carlson Accardi @ 2020-07-17 17:00 UTC (permalink / raw) To: keescook, tglx, mingo, bp, x86, H. Peter Anvin, Arnd Bergmann Cc: arjan, linux-kernel, kernel-hardening, rick.p.edgecombe, Kristen Carlson Accardi, Tony Luck, linux-arch When using -ffunction-sections to place each function in it's own text section so it can be randomized at load time, the linker considers these .text.* sections "orphaned sections", and will place them after the first similar section (.text). In order to accurately represent the end of the text section and the orphaned sections, _etext must be moved so that it is after both .text and .text.* The text size must also be calculated to include .text AND .text.* Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> Tested-by: Tony Luck <tony.luck@intel.com> Reviewed-by: Kees Cook <keescook@chromium.org> --- arch/x86/kernel/vmlinux.lds.S | 17 +++++++++++++++-- include/asm-generic/vmlinux.lds.h | 2 +- 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 3bfc8dd8a43d..e8da7eeb4d8d 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -146,9 +146,22 @@ SECTIONS #endif } :text =0xcccc - /* End of text section, which should occupy whole number of pages */ - _etext = .; + /* + * -ffunction-sections creates .text.* sections, which are considered + * "orphan sections" and added after the first similar section (.text). + * Placing this ALIGN statement before _etext causes the address of + * _etext to be below that of all the .text.* orphaned sections + */ . = ALIGN(PAGE_SIZE); + _etext = .; + + /* + * the size of the .text section is used to calculate the address + * range for orc lookups. If we just use SIZEOF(.text), we will + * miss all the .text.* sections. Calculate the size using _etext + * and _stext and save the value for later. + */ + text_size = _etext - _stext; X86_ALIGN_RODATA_BEGIN RO_DATA(PAGE_SIZE) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index a5552cf28d5d..34eab6513fdc 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -835,7 +835,7 @@ . = ALIGN(4); \ .orc_lookup : AT(ADDR(.orc_lookup) - LOAD_OFFSET) { \ orc_lookup = .; \ - . += (((SIZEOF(.text) + LOOKUP_BLOCK_SIZE - 1) / \ + . += (((text_size + LOOKUP_BLOCK_SIZE - 1) / \ LOOKUP_BLOCK_SIZE) + 1) * 4; \ orc_lookup_end = .; \ } -- 2.20.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
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2020-07-17 17:00 ` [PATCH v4 04/10] x86: Makefile: Add build and config option for CONFIG_FG_KASLR Kristen Carlson Accardi
2020-07-17 17:00 ` Kristen Carlson Accardi
2020-07-17 17:00 ` [PATCH v4 05/10] x86: Make sure _etext includes function sections Kristen Carlson Accardi
2020-07-17 17:00 ` Kristen Carlson Accardi
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