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Message-ID: <22e56a56-978a-738f-52b9-2d0c17839c9e@amd.com>
Date: Wed, 11 Oct 2017 16:34:21 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Thomas Garnier <thgarnie@...gle.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
"David S . Miller" <davem@...emloft.net>,
Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
"H . Peter Anvin" <hpa@...or.com>, Peter Zijlstra <peterz@...radead.org>,
Josh Poimboeuf <jpoimboe@...hat.com>, Arnd Bergmann <arnd@...db.de>,
Kees Cook <keescook@...omium.org>, Andrey Ryabinin
<aryabinin@...tuozzo.com>, Matthias Kaehlcke <mka@...omium.org>,
Andy Lutomirski <luto@...nel.org>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
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<rkrcmar@...hat.com>, Joerg Roedel <joro@...tes.org>,
Rik van Riel <riel@...hat.com>, David Howells <dhowells@...hat.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>, Waiman Long
<longman@...hat.com>, Kyle Huey <me@...ehuey.com>,
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Jan H . Schönherr <jschoenh@...zon.de>,
Daniel Micay <danielmicay@...il.com>
Cc: x86@...nel.org, linux-crypto@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
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kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v1 00/27] x86: PIE support and option to extend KASLR
randomization
On 10/11/2017 3:30 PM, Thomas Garnier wrote:
> Changes:
> - patch v1:
> - Simplify ftrace implementation.
> - Use gcc mstack-protector-guard-reg=%gs with PIE when possible.
> - rfc v3:
> - Use --emit-relocs instead of -pie to reduce dynamic relocation space on
> mapped memory. It also simplifies the relocation process.
> - Move the start the module section next to the kernel. Remove the need for
> -mcmodel=large on modules. Extends module space from 1 to 2G maximum.
> - Support for XEN PVH as 32-bit relocations can be ignored with
> --emit-relocs.
> - Support for GOT relocations previously done automatically with -pie.
> - Remove need for dynamic PLT in modules.
> - Support dymamic GOT for modules.
> - rfc v2:
> - Add support for global stack cookie while compiler default to fs without
> mcmodel=kernel
> - Change patch 7 to correctly jump out of the identity mapping on kexec load
> preserve.
>
> These patches make the changes necessary to build the kernel as Position
> Independent Executable (PIE) on x86_64. A PIE kernel can be relocated below
> the top 2G of the virtual address space. It allows to optionally extend the
> KASLR randomization range from 1G to 3G.
Hi Thomas,
I've applied your patches so that I can verify that SME works with PIE.
Unfortunately, I'm running into build warnings and errors when I enable
PIE.
With CONFIG_STACK_VALIDATION=y I receive lots of messages like this:
drivers/scsi/libfc/fc_exch.o: warning: objtool: fc_destroy_exch_mgr()+0x0: call without frame pointer save/setup
Disabling CONFIG_STACK_VALIDATION suppresses those.
But near the end of the build, I receive errors like this:
arch/x86/kernel/setup.o: In function `dump_kernel_offset':
.../arch/x86/kernel/setup.c:801:(.text+0x32): relocation truncated to fit: R_X86_64_32S against symbol `_text' defined in .text section in .tmp_vmlinux1
.
. about 10 more of the above type messages
.
make: *** [vmlinux] Error 1
Error building kernel, exiting
Are there any config options that should or should not be enabled when
building with PIE enabled? Is there a compiler requirement for PIE (I'm
using gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.5))?
Thanks,
Tom
>
> Thanks a lot to Ard Biesheuvel & Kees Cook on their feedback on compiler
> changes, PIE support and KASLR in general. Thanks to Roland McGrath on his
> feedback for using -pie versus --emit-relocs and details on compiler code
> generation.
>
> The patches:
> - 1-3, 5-1#, 17-18: Change in assembly code to be PIE compliant.
> - 4: Add a new _ASM_GET_PTR macro to fetch a symbol address generically.
> - 14: Adapt percpu design to work correctly when PIE is enabled.
> - 15: Provide an option to default visibility to hidden except for key symbols.
> It removes errors between compilation units.
> - 16: Adapt relocation tool to handle PIE binary correctly.
> - 19: Add support for global cookie.
> - 20: Support ftrace with PIE (used on Ubuntu config).
> - 21: Fix incorrect address marker on dump_pagetables.
> - 22: Add option to move the module section just after the kernel.
> - 23: Adapt module loading to support PIE with dynamic GOT.
> - 24: Make the GOT read-only.
> - 25: Add the CONFIG_X86_PIE option (off by default).
> - 26: Adapt relocation tool to generate a 64-bit relocation table.
> - 27: Add the CONFIG_RANDOMIZE_BASE_LARGE option to increase relocation range
> from 1G to 3G (off by default).
>
> Performance/Size impact:
>
> Size of vmlinux (Default configuration):
> File size:
> - PIE disabled: +0.000031%
> - PIE enabled: -3.210% (less relocations)
> .text section:
> - PIE disabled: +0.000644%
> - PIE enabled: +0.837%
>
> Size of vmlinux (Ubuntu configuration):
> File size:
> - PIE disabled: -0.201%
> - PIE enabled: -0.082%
> .text section:
> - PIE disabled: same
> - PIE enabled: +1.319%
>
> Size of vmlinux (Default configuration + ORC):
> File size:
> - PIE enabled: -3.167%
> .text section:
> - PIE enabled: +0.814%
>
> Size of vmlinux (Ubuntu configuration + ORC):
> File size:
> - PIE enabled: -3.167%
> .text section:
> - PIE enabled: +1.26%
>
> The size increase is mainly due to not having access to the 32-bit signed
> relocation that can be used with mcmodel=kernel. A small part is due to reduced
> optimization for PIE code. This bug [1] was opened with gcc to provide a better
> code generation for kernel PIE.
>
> Hackbench (50% and 1600% on thread/process for pipe/sockets):
> - PIE disabled: no significant change (avg +0.1% on latest test).
> - PIE enabled: between -0.50% to +0.86% in average (default and Ubuntu config).
>
> slab_test (average of 10 runs):
> - PIE disabled: no significant change (-2% on latest run, likely noise).
> - PIE enabled: between -1% and +0.8% on latest runs.
>
> Kernbench (average of 10 Half and Optimal runs):
> Elapsed Time:
> - PIE disabled: no significant change (avg -0.239%)
> - PIE enabled: average +0.07%
> System Time:
> - PIE disabled: no significant change (avg -0.277%)
> - PIE enabled: average +0.7%
>
> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82303
>
> diffstat:
> Documentation/x86/x86_64/mm.txt | 3
> arch/x86/Kconfig | 43 ++++++
> arch/x86/Makefile | 40 +++++
> arch/x86/boot/boot.h | 2
> arch/x86/boot/compressed/Makefile | 5
> arch/x86/boot/compressed/misc.c | 10 +
> arch/x86/crypto/aes-x86_64-asm_64.S | 45 ++++--
> arch/x86/crypto/aesni-intel_asm.S | 14 +-
> arch/x86/crypto/aesni-intel_avx-x86_64.S | 6
> arch/x86/crypto/camellia-aesni-avx-asm_64.S | 42 +++---
> arch/x86/crypto/camellia-aesni-avx2-asm_64.S | 44 +++---
> arch/x86/crypto/camellia-x86_64-asm_64.S | 8 -
> arch/x86/crypto/cast5-avx-x86_64-asm_64.S | 50 ++++---
> arch/x86/crypto/cast6-avx-x86_64-asm_64.S | 44 +++---
> arch/x86/crypto/des3_ede-asm_64.S | 96 +++++++++-----
> arch/x86/crypto/ghash-clmulni-intel_asm.S | 4
> arch/x86/crypto/glue_helper-asm-avx.S | 4
> arch/x86/crypto/glue_helper-asm-avx2.S | 6
> arch/x86/entry/entry_32.S | 3
> arch/x86/entry/entry_64.S | 29 ++--
> arch/x86/include/asm/asm.h | 13 +
> arch/x86/include/asm/bug.h | 2
> arch/x86/include/asm/ftrace.h | 6
> arch/x86/include/asm/jump_label.h | 8 -
> arch/x86/include/asm/kvm_host.h | 6
> arch/x86/include/asm/module.h | 11 +
> arch/x86/include/asm/page_64_types.h | 9 +
> arch/x86/include/asm/paravirt_types.h | 12 +
> arch/x86/include/asm/percpu.h | 25 ++-
> arch/x86/include/asm/pgtable_64_types.h | 6
> arch/x86/include/asm/pm-trace.h | 2
> arch/x86/include/asm/processor.h | 12 +
> arch/x86/include/asm/sections.h | 8 +
> arch/x86/include/asm/setup.h | 2
> arch/x86/include/asm/stackprotector.h | 19 ++
> arch/x86/kernel/acpi/wakeup_64.S | 31 ++--
> arch/x86/kernel/asm-offsets.c | 3
> arch/x86/kernel/asm-offsets_32.c | 3
> arch/x86/kernel/asm-offsets_64.c | 3
> arch/x86/kernel/cpu/common.c | 7 -
> arch/x86/kernel/cpu/microcode/core.c | 4
> arch/x86/kernel/ftrace.c | 42 +++++-
> arch/x86/kernel/head64.c | 32 +++-
> arch/x86/kernel/head_32.S | 3
> arch/x86/kernel/head_64.S | 41 +++++-
> arch/x86/kernel/kvm.c | 6
> arch/x86/kernel/module.c | 182 ++++++++++++++++++++++++++-
> arch/x86/kernel/module.lds | 3
> arch/x86/kernel/process.c | 5
> arch/x86/kernel/relocate_kernel_64.S | 8 -
> arch/x86/kernel/setup_percpu.c | 2
> arch/x86/kernel/vmlinux.lds.S | 13 +
> arch/x86/kvm/svm.c | 4
> arch/x86/lib/cmpxchg16b_emu.S | 8 -
> arch/x86/mm/dump_pagetables.c | 11 +
> arch/x86/power/hibernate_asm_64.S | 4
> arch/x86/tools/relocs.c | 170 +++++++++++++++++++++++--
> arch/x86/tools/relocs.h | 4
> arch/x86/tools/relocs_common.c | 15 +-
> arch/x86/xen/xen-asm.S | 12 -
> arch/x86/xen/xen-head.S | 9 -
> arch/x86/xen/xen-pvh.S | 13 +
> drivers/base/firmware_class.c | 4
> include/asm-generic/sections.h | 6
> include/asm-generic/vmlinux.lds.h | 12 +
> include/linux/compiler.h | 8 +
> init/Kconfig | 9 +
> kernel/kallsyms.c | 16 +-
> kernel/trace/trace.h | 4
> lib/dynamic_debug.c | 4
> 70 files changed, 1032 insertions(+), 308 deletions(-)
>
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