From: Alexander Lobakin <alexandr.lobakin@intel.com>
To: linux-hardening@vger.kernel.org
Cc: "Kristen C Accardi" <kristen.c.accardi@intel.com>,
Kristen Carlson Accardi <kristen@linux.intel.com>,
Kees Cook <keescook@chromium.org>,
Masahiro Yamada <masahiroy@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>, Jessica Yu <jeyu@kernel.org>,
Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Marios Pomonis <pomonis@google.com>,
Sami Tolvanen <samitolvanen@google.com>,
Tony Luck <tony.luck@intel.com>, Ard Biesheuvel <ardb@kernel.org>,
Jesse Brandeburg <jesse.brandeburg@intel.com>,
Lukasz Czapnik <lukasz.czapnik@intel.com>,
"Marta A Plantykow" <marta.a.plantykow@intel.com>,
Michal Kubiak <michal.kubiak@intel.com>,
Michal Swiatkowski <michal.swiatkowski@intel.com>,
Alexander Lobakin <alexandr.lobakin@intel.com>,
linux-kbuild@vger.kernel.org, linux-arch@vger.kernel.org,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: [PATCH v6 kspp-next 07/22] x86: Makefile: Add build and config option for CONFIG_FG_KASLR
Date: Tue, 31 Aug 2021 16:40:59 +0200 [thread overview]
Message-ID: <20210831144114.154-8-alexandr.lobakin@intel.com> (raw)
In-Reply-To: <20210831144114.154-1-alexandr.lobakin@intel.com>
From: Kristen Carlson Accardi <kristen@linux.intel.com>
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>
[ alobakin:
- improve cflags management in the top Makefile
- move ARCH_HAS_FG_KASLR to the top arch/Kconfig
- add symtab_shndx to the list of known sections ]
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
---
Makefile | 13 ++++++++++++-
arch/Kconfig | 3 +++
include/asm-generic/vmlinux.lds.h | 20 ++++++++++++++++++--
init/Kconfig | 12 ++++++++++++
4 files changed, 45 insertions(+), 3 deletions(-)
diff --git a/Makefile b/Makefile
index 61741e9d9c6e..283876e170f7 100644
--- a/Makefile
+++ b/Makefile
@@ -918,8 +918,19 @@ ifdef CONFIG_DEBUG_SECTION_MISMATCH
KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once)
endif
+# ClangLTO implies -ffunction-sections -fdata-sections, no need
+# to specify them manually and trigger a pointless full rebuild
+ifndef CONFIG_LTO_CLANG
+ifneq ($(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION)$(CONFIG_FG_KASLR),)
+KBUILD_CFLAGS_KERNEL += -ffunction-sections
+endif
+
+ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
+KBUILD_CFLAGS_KERNEL += -fdata-sections
+endif
+endif # CONFIG_LTO_CLANG
+
ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
-KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
LDFLAGS_vmlinux += --gc-sections
endif
diff --git a/arch/Kconfig b/arch/Kconfig
index 129df498a8e1..e7a9a43eee90 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1282,6 +1282,9 @@ config ARCH_SPLIT_ARG64
config ARCH_HAS_ELFCORE_COMPAT
bool
+config ARCH_HAS_FG_KASLR
+ bool
+
source "kernel/gcov/Kconfig"
source "scripts/gcc-plugins/Kconfig"
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 62669b36a772..5d6da19b02bc 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -97,14 +97,12 @@
* sections to be brought in with rodata.
*/
#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG)
-#define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* .data.$__unnamed_* .data.$L*
#define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L*
#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..compoundliteral*
#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
@@ -112,6 +110,23 @@
#define SBSS_MAIN .sbss
#endif
+/*
+ * LTO_CLANG, LD_DEAD_CODE_DATA_ELIMINATION and 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_LTO_CLANG)) && !defined(CONFIG_FG_KASLR)
+#define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
+#elif defined(CONFIG_FG_KASLR)
+#define TEXT_MAIN .text.__unused__
+#else
+#define TEXT_MAIN .text
+#endif
+
/*
* GCC 4.5 and later have a 32 bytes section alignment for structures.
* Except GCC 4.9, that feels the need to align on 64 bytes.
@@ -842,6 +857,7 @@
#define ELF_DETAILS \
.comment 0 : { *(.comment) } \
.symtab 0 : { *(.symtab) } \
+ .symtab_shndx 0 : { *(.symtab_shndx) } \
.strtab 0 : { *(.strtab) } \
.shstrtab 0 : { *(.shstrtab) }
diff --git a/init/Kconfig b/init/Kconfig
index 55f9f7738ebb..cd1440b6a566 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -2021,6 +2021,18 @@ config PROFILING
config TRACEPOINTS
bool
+config FG_KASLR
+ bool "Function Granular Kernel Address Space Layout Randomization"
+ depends on ARCH_HAS_FG_KASLR
+ 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"
--
2.31.1
next prev parent reply other threads:[~2021-08-31 14:42 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-31 14:40 [PATCH v6 kspp-next 00/22] Function Granular KASLR Alexander Lobakin
2021-08-31 14:40 ` [PATCH v6 kspp-next 01/22] kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANG Alexander Lobakin
2021-08-31 14:40 ` [PATCH v6 kspp-next 02/22] kbuild: merge vmlinux_link() between the ordinary link and Clang LTO Alexander Lobakin
2021-08-31 14:40 ` [PATCH v6 kspp-next 03/22] kbuild: do not remove 'linux' link in scripts/link-vmlinux.sh Alexander Lobakin
2021-08-31 14:40 ` [PATCH v6 kspp-next 04/22] kbuild: merge vmlinux_link() between ARCH=um and other architectures Alexander Lobakin
2021-08-31 14:40 ` [PATCH v6 kspp-next 05/22] x86: tools/relocs: Support >64K section headers Alexander Lobakin
2021-08-31 14:40 ` [PATCH v6 kspp-next 06/22] x86/boot: Allow a "silent" kaslr random byte fetch Alexander Lobakin
2021-08-31 14:40 ` Alexander Lobakin [this message]
2021-08-31 14:41 ` [PATCH v6 kspp-next 08/22] Make sure ORC lookup covers the entire _etext - _stext Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 09/22] x86/tools: Add relative relocs for randomized functions Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 10/22] x86/boot/compressed: Avoid duplicate malloc() implementations Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 11/22] x86: Add support for function granular KASLR Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 12/22] linkage: add macros for putting ASM functions into own sections Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 13/22] x86: conditionally place regular ASM functions into separate sections Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 14/22] FG-KASLR: use a scripted approach to handle .text.* sections Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 15/22] kallsyms: Hide layout Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 16/22] livepatch: only match unique symbols when using fgkaslr Alexander Lobakin
2021-09-09 11:53 ` Miroslav Benes
2021-09-10 12:29 ` Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 17/22] x86/boot: allow FG-KASLR to be selected Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 18/22] arm64/crypto: conditionally place ASM functions into separate sections Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 19/22] module: Reorder functions Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 20/22] module: use a scripted approach for FG-KASLR Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 21/22] Documentation: add a documentation " Alexander Lobakin
2021-08-31 14:41 ` [PATCH v6 kspp-next 22/22] maintainers: add MAINTAINERS entry " Alexander Lobakin
2021-08-31 17:27 ` [PATCH v6 kspp-next 00/22] Function Granular KASLR Kees Cook
2021-09-01 10:36 ` Alexander Lobakin
2021-09-02 1:36 ` Kees Cook
2021-09-03 11:19 ` Alexander Lobakin
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