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Date: Mon, 9 Feb 2009 22:39:47 +0900 From: Tejun Heo <tj@...nel.org> To: hpa@...or.com, jeremy@...p.org, tglx@...utronix.de, mingo@...e.hu, linux-kernel@...r.kernel.org, x86@...nel.org, rusty@...tcorp.com.au Subject: [PATCHSET x86/master] add stack protector support for x86_32 Hello, This patchset adds stack protector support for x86_32. The basics are the same with x86_64 but there are some noticeable differences. * x86_32 uses %fs for percpu base. %gs is unused by the kernel and managed lazily. %gs is used for userland TLS and loading %gs with different value on kernel entry is known to cost quite a bit on some chips. Lazy %gs handling is made optional and disabled if stack protector is enabled. To do this, entry for %gs is added to pt_regs. This adds one "pushl $0" to SAVE_ALL in entry_32.S when lazy %gs is on. However, no overhead is added to common exit path and error_code entry path shed a few instructions. I don't think there will be noticeable overhead but then again it does add an instruction to a very hot path. Would this be okay? * x86_32 doesn't support direct access to shadow part of %gs and there's no swapgs, so GDT entry should be built for stack canary. GDT entry 28 is used for this. The boot cpu one is setup from head_32.S. Others while setting up percpu areas. * math_emu register access was completely broken. Fixed. * x86_32 exception handlers take register frame verbatim as struct pt_regs. With -fstack-protector, gcc copies pt_regs into the callee's stack frame to put it after the stack canary. Of course it doesn't copy back (as the callee owns the argument) and any change made to pt_regs is lost on return. This is currently worked around by adding -fno-stack-protector to any file containing such functions. We really need to teach gcc about the calling convention. This patchset contains the following eleven patches. 0001-x86-include-correct-gs-in-a.out-core-dump.patch 0002-x86-math_emu-info-cleanup.patch 0003-x86-fix-math_emu-register-frame-access.patch 0004-elf-add-ELF_CORE_COPY_KERNEL_REGS.patch 0005-x86-stackprotector.h-misc-update.patch 0006-stackprotector-update-make-rules.patch 0007-x86-no-stack-protector-for-vdso.patch 0008-x86-use-asm-.macro-instead-of-cpp-define-in-entry_.patch 0009-x86-add-gs-accessors-for-x86_32.patch 0010-x86-make-lazy-gs-optional-on-x86_32.patch 0011-x86-implement-x86_32-stack-protector.patch 0001 is a misc fix. 0002-0003 fixes math_emu register frame access. 0004-0008 preps for stack protector changes. 0009-0010 makes lazy %gs handling optional. 0011 implements stack protector support for x86_32. Jeremy, Rusty, can you guys please take a look at patch #0010 and #0011 and see whether xen and lguest are okay? I don't think anything is broken for those although stackp might not work but haven't tested them. I'll try to learn xen and lguest and test them in the future. This patchset is against the current x86/master[1]. If acked, please pull from the following git branch git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git tj-stackp32 to receive the following changes. Makefile | 3 arch/x86/Kconfig | 5 arch/x86/Makefile | 17 - arch/x86/include/asm/a.out-core.h | 4 arch/x86/include/asm/elf.h | 15 - arch/x86/include/asm/math_emu.h | 29 -- arch/x86/include/asm/mmu_context.h | 2 arch/x86/include/asm/processor.h | 6 arch/x86/include/asm/ptrace.h | 4 arch/x86/include/asm/segment.h | 9 arch/x86/include/asm/stackprotector.h | 96 ++++++ arch/x86/include/asm/system.h | 40 ++ arch/x86/include/asm/traps.h | 4 arch/x86/kernel/Makefile | 18 + arch/x86/kernel/asm-offsets_32.c | 1 arch/x86/kernel/cpu/common.c | 17 - arch/x86/kernel/entry_32.S | 423 ++++++++++++++++++------------ arch/x86/kernel/head_32.S | 20 + arch/x86/kernel/process_32.c | 11 arch/x86/kernel/ptrace.c | 19 - arch/x86/kernel/setup_percpu.c | 2 arch/x86/kernel/signal.c | 41 +- arch/x86/kernel/traps.c | 15 - arch/x86/kernel/vm86_32.c | 4 arch/x86/lguest/boot.c | 2 arch/x86/math-emu/fpu_entry.c | 6 arch/x86/math-emu/fpu_proto.h | 4 arch/x86/math-emu/fpu_system.h | 16 - arch/x86/math-emu/get_address.c | 75 ++--- arch/x86/vdso/Makefile | 2 arch/x86/xen/enlighten.c | 17 - include/linux/elfcore.h | 9 kernel/kexec.c | 2 kernel/panic.c | 4 scripts/gcc-x86_32-has-stack-protector.sh | 8 scripts/gcc-x86_64-has-stack-protector.sh | 4 36 files changed, 619 insertions(+), 335 deletions(-) Thanks. -- tejun [1] 2076fe22811d836936b80ad1c55997f70bb0ae8d -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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