From: Alexander Lobakin <alexandr.lobakin@intel.com>
To: linux-hardening@vger.kernel.org, x86@kernel.org
Cc: Alexander Lobakin <alexandr.lobakin@intel.com>,
Borislav Petkov <bp@alien8.de>,
Jesse Brandeburg <jesse.brandeburg@intel.com>,
Kristen Carlson Accardi <kristen@linux.intel.com>,
Kees Cook <keescook@chromium.org>,
Miklos Szeredi <miklos@szeredi.hu>,
Ard Biesheuvel <ardb@kernel.org>, Tony Luck <tony.luck@intel.com>,
Bruce Schlobohm <bruce.schlobohm@intel.com>,
Jessica Yu <jeyu@kernel.org>, kernel test robot <lkp@intel.com>,
Miroslav Benes <mbenes@suse.cz>,
Evgenii Shatokhin <eshatokhin@virtuozzo.com>,
Jonathan Corbet <corbet@lwn.net>,
Masahiro Yamada <masahiroy@kernel.org>,
Michal Marek <michal.lkml@markovi.net>,
Nick Desaulniers <ndesaulniers@google.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Christoph Hellwig <hch@lst.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Arnd Bergmann <arnd@arndb.de>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Nathan Chancellor <nathan@kernel.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
Marios Pomonis <pomonis@google.com>,
Sami Tolvanen <samitolvanen@google.com>,
"H.J. Lu" <hjl.tools@gmail.com>, Nicolas Pitre <nico@fluxnic.net>,
linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org,
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llvm@lists.linux.dev
Subject: [PATCH v10 07/15] Makefile: add config options and build scripts for FG-KASLR
Date: Wed, 9 Feb 2022 19:57:44 +0100 [thread overview]
Message-ID: <20220209185752.1226407-8-alexandr.lobakin@intel.com> (raw)
In-Reply-To: <20220209185752.1226407-1-alexandr.lobakin@intel.com>
From: Kristen Carlson Accardi <kristen@linux.intel.com>
Add Kconfig symbols CONFIG_ARCH_SUPPORTS_FG_KASLR and
CONFIG_FG_KASLR. The first is hidden and used to indicate that
a particular architecture supports it, the second allows a user
to enable FG-KASLR when the former is set to 'y'.
Make Kbuild not consolidate function sections back into `.text`
on linking if CONFIG_FG_KASLR is enabled (even with
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y) as the feature itself
relies on functions still being separated in the final vmlinux.
Alexander Lobakin:
Improve KBUILD_CFLAGS{,_MODULE} management in the top Makefile:
don't turn on -f{data,function}-sections with ClangLTO as this is a
no-op provoking a full rebuild.
Add ".symtab_shndx" to the list of known sections since it is going
to be supported by the architecture-specific code. Otherwise LD
emits a warning when there are more than 64k sections and
CONFIG_LD_ORPHAN_WARN=y.
Turn ".text" LD script wildcard into ".text.__unused__" to make sure
all kernel code will land into our special sections.
Make FG-KASLR depend on `-z unique-symbol`. With every function being
in a separate section (randomly ordered each boot), position-based
search is impossible. This flag is likely to be widely available
(on non-LLD builds).
Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
Suggested-by: Kees Cook <keescook@chromium.org> # coexistence with DCE
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Co-developed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
---
Makefile | 17 ++++++++++++++---
arch/Kconfig | 6 +++++-
include/asm-generic/vmlinux.lds.h | 20 ++++++++++++++++++--
include/linux/linkage.h | 9 +++++----
init/Kconfig | 19 +++++++++++++++++--
5 files changed, 59 insertions(+), 12 deletions(-)
diff --git a/Makefile b/Makefile
index fbe2d13028f4..4328d53d8b25 100644
--- a/Makefile
+++ b/Makefile
@@ -872,7 +872,7 @@ KBUILD_CFLAGS += -fno-inline-functions-called-once
endif
# Prefer linking with the `-z unique-symbol` if available, this eliminates
-# position-based search
+# position-based search. Also is a requirement for FG-KASLR
ifeq ($(CONFIG_LD_HAS_Z_UNIQUE_SYMBOL)$(CONFIG_LIVEPATCH),yy)
KBUILD_LDFLAGS += -z unique-symbol
endif
@@ -881,7 +881,7 @@ endif
# `include/linux/linkage.h` for explanation. This flag is to enable GAS to
# insert the name of the previous section instead of `%S` inside .pushsection
ifdef CONFIG_HAVE_ASM_FUNCTION_SECTIONS
-ifneq ($(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION)$(CONFIG_LTO_CLANG),)
+ifneq ($(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION)$(CONFIG_LTO_CLANG)$(CONFIG_FG_KASLR),)
SECSUBST_AFLAGS := -Wa,--sectname-subst
KBUILD_AFLAGS_KERNEL += $(SECSUBST_AFLAGS)
KBUILD_CFLAGS_KERNEL += $(SECSUBST_AFLAGS)
@@ -895,8 +895,19 @@ KBUILD_CFLAGS_MODULE += -Wa,--sectname-subst
endif
endif # CONFIG_HAVE_ASM_FUNCTION_SECTIONS
+# ClangLTO implies `-ffunction-sections -fdata-sections`, no need
+# to specify them manually and trigger a pointless full rebuild
+ifndef CONFIG_LTO_CLANG
+ifneq ($(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION)$(CONFIG_FG_KASLR),)
+KBUILD_CFLAGS_KERNEL += -ffunction-sections
+endif
+
+ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
+KBUILD_CFLAGS_KERNEL += -fdata-sections
+endif
+endif # CONFIG_LTO_CLANG
+
ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
-KBUILD_CFLAGS_KERNEL += -ffunction-sections -fdata-sections
LDFLAGS_vmlinux += --gc-sections
endif
diff --git a/arch/Kconfig b/arch/Kconfig
index 550f0599e211..e06aeeea39f4 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1326,7 +1326,11 @@ config ARCH_SUPPORTS_ASM_FUNCTION_SECTIONS
bool
help
An arch should select this if it can be built and run with its
- asm functions placed into separate sections to improve DCE and LTO.
+ asm functions placed into separate sections to improve DCE, LTO
+ and FG-KASLR.
+
+config ARCH_SUPPORTS_FG_KASLR
+ bool
source "kernel/gcov/Kconfig"
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index e7b8a84e0e64..586465b2abb2 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -100,14 +100,12 @@
* sections to be brought in with rodata.
*/
#if defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) || defined(CONFIG_LTO_CLANG)
-#define TEXT_MAIN SECT_WILDCARD(.text)
#define DATA_MAIN SECT_WILDCARD(.data) .data..L* .data..compoundliteral* .data.$__unnamed_* .data.$L*
#define SDATA_MAIN SECT_WILDCARD(.sdata)
#define RODATA_MAIN SECT_WILDCARD(.rodata) .rodata..L*
#define BSS_MAIN SECT_WILDCARD(.bss) .bss..compoundliteral*
#define SBSS_MAIN SECT_WILDCARD(.sbss)
#else
-#define TEXT_MAIN .text
#define DATA_MAIN .data
#define SDATA_MAIN .sdata
#define RODATA_MAIN .rodata
@@ -115,6 +113,23 @@
#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 SECT_WILDCARD(.text)
+#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.
@@ -843,6 +858,7 @@
#define ELF_DETAILS \
.comment 0 : { *(.comment) } \
.symtab 0 : { *(.symtab) } \
+ .symtab_shndx 0 : { *(.symtab_shndx) } \
.strtab 0 : { *(.strtab) } \
.shstrtab 0 : { *(.shstrtab) }
diff --git a/include/linux/linkage.h b/include/linux/linkage.h
index f3b966a6427e..95ca162a868c 100644
--- a/include/linux/linkage.h
+++ b/include/linux/linkage.h
@@ -75,11 +75,12 @@
/*
* Allow ASM symbols to have their own unique sections if they are being
- * generated by the compiler for C functions (DCE, LTO). Correlates with
- * the presence of the `-ffunction-section` in KBUILD_CFLAGS.
+ * generated by the compiler for C functions (DCE, FG-KASLR, LTO). Correlates
+ * with the presence of the `-ffunction-section` in KBUILD_CFLAGS.
*/
#if defined(CONFIG_HAVE_ASM_FUNCTION_SECTIONS) && \
((defined(CONFIG_LD_DEAD_CODE_DATA_ELIMINATION) && !defined(MODULE)) || \
+ (defined(CONFIG_FG_KASLR) && !defined(MODULE)) || \
(defined(CONFIG_LTO_CLANG)))
#define SYM_PUSH_SECTION(name) \
@@ -91,13 +92,13 @@
#define __ASM_PUSH_SECTION(name) \
".pushsection %S." name ", \"ax\""
-#else /* !(CONFIG_HAVE_ASM_FUNCTION_SECTIONS && (DCE || LTO)) */
+#else /* !(CONFIG_HAVE_ASM_FUNCTION_SECTIONS && (DCE || FG_KASLR || LTO)) */
#define SYM_PUSH_SECTION(name)
#define SYM_POP_SECTION()
#define __ASM_PUSH_SECTION(name)
-#endif /* !(CONFIG_HAVE_ASM_FUNCTION_SECTIONS && (DCE || LTO)) */
+#endif /* !(CONFIG_HAVE_ASM_FUNCTION_SECTIONS && (DCE || FG_KASLR || LTO)) */
#define ASM_PUSH_SECTION(name) \
__ASM_PUSH_SECTION(__stringify(name))
diff --git a/init/Kconfig b/init/Kconfig
index 4acfc80f22df..26f9a6e52dbd 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1393,8 +1393,9 @@ config HAVE_ASM_FUNCTION_SECTIONS
help
This enables asm function sections if both architecture and
toolchain support it. It allows creating a separate section
- for each function written in assembly in order to improve DCE
- and LTO (works the same way as -ffunction-sections for C code).
+ for each function written in assembly in order to improve DCE,
+ LTO and FG-KASLR (works the same way as -ffunction-sections
+ for C code).
config HAVE_LD_DEAD_CODE_DATA_ELIMINATION
bool
@@ -2061,6 +2062,20 @@ config PROFILING
config TRACEPOINTS
bool
+config FG_KASLR
+ bool "Function Granular Kernel Address Space Layout Randomization"
+ depends on ARCH_SUPPORTS_FG_KASLR
+ depends on $(cc-option,-ffunction-sections)
+ depends on LD_HAS_Z_UNIQUE_SYMBOL || !LIVEPATCH
+ 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"
--
2.34.1
next prev parent reply other threads:[~2022-02-09 19:02 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-09 18:57 [PATCH v10 00/15] Function Granular KASLR Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 01/15] modpost: fix removing numeric suffixes Alexander Lobakin
2022-05-03 0:57 ` Masahiro Yamada
2022-05-03 7:31 ` Petr Mladek
2022-05-23 18:04 ` Masahiro Yamada
2022-05-24 11:33 ` Alexander Lobakin
2022-05-24 13:40 ` Masahiro Yamada
2022-02-09 18:57 ` [PATCH v10 02/15] livepatch: avoid position-based search if `-z unique-symbol` is available Alexander Lobakin
2022-02-11 17:41 ` Josh Poimboeuf
2022-02-11 18:05 ` Fāng-ruì Sòng
2022-02-11 18:35 ` Josh Poimboeuf
2022-02-14 12:24 ` Alexander Lobakin
2022-02-14 18:10 ` Josh Poimboeuf
2022-02-16 20:32 ` Joe Lawrence
2022-02-16 22:13 ` Josh Poimboeuf
2022-02-16 15:15 ` Miroslav Benes
2022-02-16 20:01 ` Josh Poimboeuf
2022-02-18 16:31 ` Alexander Lobakin
2022-02-18 20:08 ` Josh Poimboeuf
2022-02-14 12:14 ` Alexander Lobakin
2022-02-14 18:57 ` Josh Poimboeuf
2022-02-16 15:06 ` Miroslav Benes
2022-02-16 19:57 ` Josh Poimboeuf
2022-02-17 7:45 ` Miroslav Benes
2022-02-09 18:57 ` [PATCH v10 03/15] kallsyms: randomize /proc/kallsyms output order Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 04/15] arch: introduce asm function sections Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 05/15] x86: support " Alexander Lobakin
2022-02-11 15:45 ` Peter Zijlstra
2022-02-14 11:49 ` Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 06/15] x86: decouple ORC table sorting into a separate file Alexander Lobakin
2022-02-09 18:57 ` Alexander Lobakin [this message]
2022-02-09 18:57 ` [PATCH v10 08/15] x86/tools: Add relative relocs for randomized functions Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 09/15] x86: Add support for function granular KASLR Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 10/15] FG-KASLR: use a scripted approach to handle .text.* sections Alexander Lobakin
2022-02-11 15:37 ` Peter Zijlstra
2022-02-14 11:34 ` Alexander Lobakin
2022-02-14 11:59 ` Peter Zijlstra
2022-02-14 12:30 ` Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 11/15] x86/boot: allow FG-KASLR to be selected Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 12/15] module: add arch-indep FG-KASLR for randomizing function layout Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 13/15] module: use a scripted approach for FG-KASLR Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 14/15] Documentation: add documentation " Alexander Lobakin
2022-02-09 18:57 ` [PATCH v10 15/15] maintainers: add MAINTAINERS entry " Alexander Lobakin
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