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Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 asm changes from Ingo Molnar: "The main change in this cycle is another step in the big x86 system call interface rework by Andy Lutomirski, which moves most of the low level x86 entry code from assembly to C, for all syscall entries except native 64-bit system calls: arch/x86/entry/entry_32.S | 182 ++++------ arch/x86/entry/entry_64_compat.S | 547 ++++++++----------------------- 194 insertions(+), 535 deletions(-) ... our hope is that the final remaining step (converting native 64-bit system calls) will be less painful as all the previous steps, given that most of the legacies and quirks are concentrated around native 32-bit and compat environments" * 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (47 commits) x86/entry/32: Fix FS and GS restore in opportunistic SYSEXIT x86/entry/32: Fix entry_INT80_32() to expect interrupts to be on um/x86: Fix build after x86 syscall changes x86/asm: Remove the xyz_cfi macros from dwarf2.h selftests/x86: Style fixes for the 'unwind_vdso' test x86/entry/64/compat: Document sysenter_fix_flags's reason for existence x86/entry: Split and inline syscall_return_slowpath() x86/entry: Split and inline prepare_exit_to_usermode() x86/entry: Use pt_regs_to_thread_info() in syscall entry tracing x86/entry: Hide two syscall entry assertions behind CONFIG_DEBUG_ENTRY x86/entry: Micro-optimize compat fast syscall arg fetch x86/entry: Force inlining of 32-bit syscall code x86/entry: Make irqs_disabled checks in exit code depend on lockdep x86/entry: Remove unnecessary IRQ twiddling in fast 32-bit syscalls x86/asm: Remove thread_info.sysenter_return x86/entry/32: Re-implement SYSENTER using the new C path x86/entry/32: Switch INT80 to the new C syscall path x86/entry/32: Open-code return tracking from fork and kthreads x86/entry/compat: Implement opportunistic SYSRETL for compat syscalls x86/vdso/compat: Wire up SYSENTER and SYSCSALL for compat userspace ...
2 parents d2bea73 + 3bd2951 commit a75a3f6

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‎arch/x86/Kconfig

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@@ -2027,6 +2027,55 @@ config COMPAT_VDSO
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If unsure, say N: if you are compiling your own kernel, you
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are unlikely to be using a buggy version of glibc.
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choice
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prompt "vsyscall table for legacy applications"
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depends on X86_64
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default LEGACY_VSYSCALL_EMULATE
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help
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Legacy user code that does not know how to find the vDSO expects
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to be able to issue three syscalls by calling fixed addresses in
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kernel space. Since this location is not randomized with ASLR,
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it can be used to assist security vulnerability exploitation.
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This setting can be changed at boot time via the kernel command
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line parameter vsyscall=[native|emulate|none].
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On a system with recent enough glibc (2.14 or newer) and no
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static binaries, you can say None without a performance penalty
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to improve security.
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If unsure, select "Emulate".
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config LEGACY_VSYSCALL_NATIVE
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bool "Native"
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help
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Actual executable code is located in the fixed vsyscall
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address mapping, implementing time() efficiently. Since
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this makes the mapping executable, it can be used during
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security vulnerability exploitation (traditionally as
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ROP gadgets). This configuration is not recommended.
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config LEGACY_VSYSCALL_EMULATE
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bool "Emulate"
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help
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The kernel traps and emulates calls into the fixed
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vsyscall address mapping. This makes the mapping
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non-executable, but it still contains known contents,
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which could be used in certain rare security vulnerability
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exploits. This configuration is recommended when userspace
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still uses the vsyscall area.
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config LEGACY_VSYSCALL_NONE
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bool "None"
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help
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There will be no vsyscall mapping at all. This will
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eliminate any risk of ASLR bypass due to the vsyscall
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fixed address mapping. Attempts to use the vsyscalls
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will be reported to dmesg, so that either old or
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malicious userspace programs can be identified.
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endchoice
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config CMDLINE_BOOL
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bool "Built-in kernel command line"
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---help---

‎arch/x86/Makefile

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@@ -159,15 +159,21 @@ endif
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sp-$(CONFIG_X86_32) := esp
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sp-$(CONFIG_X86_64) := rsp
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# do binutils support CFI?
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cfi := $(call as-instr,.cfi_startproc\n.cfi_rel_offset $(sp-y)$(comma)0\n.cfi_endproc,-DCONFIG_AS_CFI=1)
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# is .cfi_signal_frame supported too?
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cfi-sigframe := $(call as-instr,.cfi_startproc\n.cfi_signal_frame\n.cfi_endproc,-DCONFIG_AS_CFI_SIGNAL_FRAME=1)
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cfi-sections := $(call as-instr,.cfi_sections .debug_frame,-DCONFIG_AS_CFI_SECTIONS=1)
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# does binutils support specific instructions?
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asinstr := $(call as-instr,fxsaveq (%rax),-DCONFIG_AS_FXSAVEQ=1)
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asinstr += $(call as-instr,pshufb %xmm0$(comma)%xmm0,-DCONFIG_AS_SSSE3=1)
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asinstr += $(call as-instr,crc32l %eax$(comma)%eax,-DCONFIG_AS_CRC32=1)
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avx_instr := $(call as-instr,vxorps %ymm0$(comma)%ymm1$(comma)%ymm2,-DCONFIG_AS_AVX=1)
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avx2_instr :=$(call as-instr,vpbroadcastb %xmm0$(comma)%ymm1,-DCONFIG_AS_AVX2=1)
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KBUILD_AFLAGS += $(asinstr) $(avx_instr) $(avx2_instr)
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KBUILD_CFLAGS += $(asinstr) $(avx_instr) $(avx2_instr)
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KBUILD_AFLAGS += $(cfi) $(cfi-sigframe) $(cfi-sections) $(asinstr) $(avx_instr) $(avx2_instr)
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KBUILD_CFLAGS += $(cfi) $(cfi-sigframe) $(cfi-sections) $(asinstr) $(avx_instr) $(avx2_instr)
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LDFLAGS := -m elf_$(UTS_MACHINE)
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