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(-) > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
