[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 0/9] x86: Enable Supervisor Mode Access Prevention (SMAP)
Supervisor Mode Access Prevention (SMAP) is a new security feature disclosed by Intel, please refer to the following document: http://software.intel.com/sites/default/files/319433-014.pdf Every access to a linear address is either a supervisor-mode access or a user-mode access. All accesses performed while the current privilege level (CPL) is less than 3 are supervisor-mode accesses. If CPL = 3, accesses are generally user-mode accesses. However, some operations implicitly access system data structures, and the resulting accesses to those data structures are supervisor-mode accesses regardless of CPL. Examples of such implicit supervisor accesses include the following: accesses to the global descriptor table (GDT) or local descriptor table (LDT) to load a segment descriptor; accesses to the interrupt descriptor table (IDT) when delivering an interrupt or exception; and accesses to the task-state segment (TSS) as part of a task switch or change of CPL. If CR4.SMAP = 1, supervisor-mode data accesses are not allowed to linear addresses that are accessible in user mode. If CPL < 3, SMAP protections are disabled if EFLAGS.AC = 1. If CPL = 3, SMAP applies to all supervisor-mode data accesses (these are implicit supervisor accesses) regardless of the value of EFLAGS.AC. Version 1: * Add two macros for STAC/CLAC instructions * Temporary disable SMAP to legally access user pages in kernel mode * Enable Supervisor Mode Access Prevention (SMAP) for Xen itself * Add SMAP support to HVM guest * Disable SMAP feature when guest is in non-paging mode Version 2: * Change the definition of ASM_STAC/ASM_CLAC. * Clear AC bit at the beginning of exception, interrup, hypercall. * Make construct_dom0() wrapped in a stac()/clac() part as a whole. * Reorder some patches in the series. * Combine some conditionals with SMEP. * Typo, etc. Version 3: * Clean-ups to ASM_STAC/ASM_CLAC * Enable SMAP after constructin domain 0 * Move common_interrupt to entry.S * Remove ASM_CLAC calls in some places where exception happens * Correct the logic in hvm_vcpu_has_smep()/hvm_vcpu_has_smap() * Make the output message more readable when SMAP violation happens * Use hvm_get_segment_register() to get the guest SS in guest_walk_tables() * Coding style changes, etc. Since Linux kernel has already supported SMAP, I tested this patch both in EPT and shadow mode with Linux guest, they work well. And I also tested the failure case, in which, I triggered an SMAP violation in the guest kernel and Linux successfully received the related page fault. Feng Wu (9): x86: define CPUINFO_features used as the base offset for cpu features x86: move common_interrupt to entry.S x86: Add support for STAC/CLAC instructions Clear AC bit in RFLAGS to protect Xen itself by SMAP x86: Temporary disable SMAP to legally access user pages in kernel mode VMX: Disable SMAP feature when guest is in non-paging mode x86: Enable Supervisor Mode Access Prevention (SMAP) for Xen x86/hvm: Add SMAP support to HVM guest x86/tools: Expose SMAP to HVM guests docs/misc/xen-command-line.markdown | 7 ++++ tools/libxc/xc_cpufeature.h | 1 + tools/libxc/xc_cpuid_x86.c | 1 + xen/arch/x86/boot/head.S | 2 +- xen/arch/x86/hvm/hvm.c | 3 ++ xen/arch/x86/hvm/vmx/vmx.c | 6 ++-- xen/arch/x86/i8259.c | 4 --- xen/arch/x86/mm/guest_walk.c | 39 ++++++++++++++++------ xen/arch/x86/setup.c | 13 ++++++++ xen/arch/x86/traps.c | 60 +++++++++++++++++++++++++--------- xen/arch/x86/usercopy.c | 6 ++++ xen/arch/x86/x86_64/asm-offsets.c | 2 +- xen/arch/x86/x86_64/compat/entry.S | 3 ++ xen/arch/x86/x86_64/entry.S | 16 +++++++++ xen/arch/x86/x86_64/traps.c | 4 +-- xen/include/asm-x86/asm_defns.h | 48 +++++++++++++++++++++++++++ xen/include/asm-x86/cpufeature.h | 5 +++ xen/include/asm-x86/domain.h | 6 ++-- xen/include/asm-x86/hvm/hvm.h | 16 +++++++++ xen/include/asm-x86/uaccess.h | 4 +++ xen/include/asm-x86/x86_64/asm_defns.h | 9 ----- xen/include/asm-x86/x86_64/system.h | 2 ++ 22 files changed, 210 insertions(+), 47 deletions(-) -- 1.8.3.1 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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