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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v4] xSplice v1 design and implementation.
Hey! Changelog: v3: http://www.gossamer-threads.com/lists/xen/devel/418262 and http://lists.xenproject.org/archives/html/xen-devel/2016-02/msg04106.html - Act on all reviews. - Redo the flow of patches v2: http://lists.xen.org/archives/html/xen-devel/2016-01/msg01597.html - Updated code/docs/design with review comments. - Make xen also have an PT_NOTE - Added more of Ross's patches - Combined build-id patchset with this. (since the RFC and the Seattle Xen presentation) - Finished off some of the work around the build-id. - Settled on the preemption mechanism. - Cleaned the patches a lot up, broke them up to easy review for maintainers. v1: http://lists.xenproject.org/archives/html/xen-devel/2015-09/msg02116.html - Put all the design comments in the code Prototype: http://lists.xenproject.org/archives/html/xen-devel/2015-10/msg02595.html [Posting by Ross] - Took all reviews into account. - Redid the patches *Flow of patches* The first five patches add the neccessary components that have been requested by Andrew. There are also four fixes I've included. I was not sure if it made sense to split it of as a standalone patchset (similar to how I did it in v3) or just include it in this patchset. To make it easier for folks to see the whole thing I've just included them in this giant patchset: compat/x86: Remove unncessary #define. libxc: Remove dead code (XENVER_capabilities) xsm/xen_version: Add XSM for the xen_version hypercall HYPERCALL_version_op. New hypercall mirroring XENVER_ but sane. libxc/libxl/python/xenstat: Use new XEN_VERSION_OP hypercall x86/arm: Add BUGFRAME_NR define and BUILD checks. arm/x86: Use struct virtual_region to do bug, symbol, and (x86) exception tables vmap: Make the while loop less fishy. vmap: ASSERT on NULL. vmap: Add vmalloc_cb and vfree_cb Since they are generic and touch ARM and x86 they have been tested on x86 (legacy and EFI) and on ARM (CubieTruck). Actually the whole branch has been tested on those three platforms. *What is xSplice?* A mechanism to binarily patch the running hypervisor with new opcodes that have come about due to primarily security updates. *What will this patchset do once I've it* Patch the hypervisor. *Why are you emailing me?* Please please review as many patches as possible. *OK, what do you have?* They are located at a git tree: git://xenbits.xen.org/people/konradwilk/xen.git xsplice.v4 (Copying from Ross's email): Much of the work is implementing a basic version of the Linux kernel module loader. The code: * Loading of xSplice ELF payloads. * Copying allocated sections into a new executable region of memory. * Resolving symbols. * Applying relocations. * Patching of altinstructions. * Special handling of bug frames and exception tables. * Unloading of xSplice ELF payloads. * Compiling a sample xSplice ELF payload * Resolving symbols * Using build-id dependencies * Support for shadow variable framework * Support for executing ELF payload functions on load/unload. The other main bit of this work is applying and reverting the patches safely. As implemented, the code is patched with each CPU waiting in the return-to-guest path (i.e. with no stack) or on the cpu-idle path which appears to be the safest way of patching. While it is safe we should still (in the next wave of patches) to verify to not patch cetain critical sections (say the code doing the patching) All of the following should work: * Applying patches safely. * Reverting patches safely. * Replacing patches safely (e.g. reverting any applied patches and applying a new patch). * Bug frames as part of modules. This means adding or changing WARN, ASSERT, BUG, and run_in_exception_handler works correctly. Line number only changes _are ignored_. * Exception tables as part of modules. E.g. wrmsr_safe and copy_to_user work correctly when used in a patch module. * Stacking of patches on top of each other * Resolving symbols (even of patches) *Limitations* The above is enough to fully implement an update system where multiple source patches are combined (using combinediff) and built into a single binary which then atomically replaces any existing loaded patches (this is why Ross added a REPLACE operation). This is the approach used by kPatch and kGraft. Multiple completely independent patches can also be loaded but unexpected interactions may occur. As it stands, the patches are statically linked which means that independent patches cannot be linked against one another (e.g. if one introduces a new symbol). Using the combinediff approach above fixes this. Backtraces containing functions from a patch module do not show the symbol name. There is no checking that a patch which is loaded is built for the correct hypervisor (need to use build-id). Binary patching works at the function level. *Testing* You can use the example code included in this patchset: # xl info | grep extra xen_extra : -unstable # xen-xsplice load /usr/lib/debug/xen_hello_world.xsplice Uploading /usr/lib/debug/xen_hello_world.xsplice (2071 bytes) Performing check: completed Performing apply:. completed # xl info | grep extra xen_extra : Hello World # xen-xsplice revert xen_hello_world Performing revert:. completed # xen-xsplice unload xen_hello_world Performing unload: completed # xl info | grep extra xen_extra : -unstable Or you can use git://xenbits.xen.org/people/konradwilk/xsplice-build-tools.git which generates the ELF payloads. This link has a nice description of how to use the tool: http://lists.xenproject.org/archives/html/xen-devel/2015-10/msg02595.html .gitignore | 3 + Config.mk | 12 + MAINTAINERS | 10 + docs/misc/xsplice.markdown | 1115 +++++++++++++++++++ tools/flask/policy/policy/modules/xen/xen.te | 21 + tools/libxc/include/xenctrl.h | 86 +- tools/libxc/xc_core.c | 35 +- tools/libxc/xc_dom_boot.c | 12 +- tools/libxc/xc_dom_x86.c | 7 - tools/libxc/xc_domain.c | 3 +- tools/libxc/xc_misc.c | 337 ++++++ tools/libxc/xc_private.c | 53 +- tools/libxc/xc_private.h | 7 +- tools/libxc/xc_resume.c | 3 +- tools/libxc/xc_sr_save.c | 9 +- tools/libxc/xg_save_restore.h | 6 +- tools/libxl/libxl.c | 94 +- tools/libxl/libxl.h | 5 + tools/libxl/libxl_types.idl | 1 + tools/libxl/xl_cmdimpl.c | 1 + tools/misc/Makefile | 4 + tools/misc/xen-xsplice.c | 463 ++++++++ tools/ocaml/libs/xc/xenctrl_stubs.c | 39 +- tools/python/xen/lowlevel/xc/xc.c | 30 +- tools/xenstat/libxenstat/src/xenstat.c | 12 +- tools/xentrace/xenctx.c | 3 +- xen/Makefile | 2 + xen/arch/arm/Makefile | 7 +- xen/arch/arm/traps.c | 46 +- xen/arch/arm/xen.lds.S | 20 +- xen/arch/arm/xsplice.c | 76 ++ xen/arch/x86/Makefile | 45 +- xen/arch/x86/alternative.c | 20 +- xen/arch/x86/boot/mkelf32.c | 137 ++- xen/arch/x86/domain.c | 4 + xen/arch/x86/extable.c | 44 +- xen/arch/x86/hvm/hvm.c | 1 + xen/arch/x86/hvm/svm/svm.c | 2 + xen/arch/x86/hvm/vmx/vmcs.c | 2 + xen/arch/x86/setup.c | 10 +- xen/arch/x86/test/Makefile | 87 ++ xen/arch/x86/test/xen_bye_world.c | 35 + xen/arch/x86/test/xen_bye_world_func.c | 25 + xen/arch/x86/test/xen_hello_world.c | 54 + xen/arch/x86/test/xen_hello_world_func.c | 26 + xen/arch/x86/test/xen_replace_world.c | 35 + xen/arch/x86/test/xen_replace_world_func.c | 25 + xen/arch/x86/traps.c | 51 +- xen/arch/x86/x86_64/compat/entry.S | 2 + xen/arch/x86/x86_64/entry.S | 2 + xen/arch/x86/xen.lds.S | 23 + xen/arch/x86/xsplice.c | 295 +++++ xen/common/Kconfig | 16 + xen/common/Makefile | 4 + xen/common/bug_ex_symbols.c | 119 +++ xen/common/compat/kernel.c | 4 +- xen/common/kernel.c | 328 +++++- xen/common/symbols.c | 62 +- xen/common/sysctl.c | 7 + xen/common/version.c | 82 ++ xen/common/vmap.c | 45 +- xen/common/vsprintf.c | 15 +- xen/common/xsplice.c | 1476 ++++++++++++++++++++++++++ xen/common/xsplice_elf.c | 385 +++++++ xen/common/xsplice_shadow.c | 109 ++ xen/include/asm-arm/bug.h | 2 + xen/include/asm-arm/nmi.h | 13 + xen/include/asm-x86/alternative.h | 6 + xen/include/asm-x86/bug.h | 3 +- xen/include/asm-x86/uaccess.h | 5 + xen/include/asm-x86/x86_64/page.h | 2 + xen/include/public/arch-arm.h | 3 + xen/include/public/sysctl.h | 169 +++ xen/include/public/version.h | 75 +- xen/include/public/xen.h | 1 + xen/include/xen/bug_ex_symbols.h | 74 ++ xen/include/xen/hypercall.h | 4 + xen/include/xen/kernel.h | 2 + xen/include/xen/symbols.h | 11 + xen/include/xen/version.h | 6 + xen/include/xen/vmap.h | 14 + xen/include/xen/xsplice.h | 129 +++ xen/include/xen/xsplice_elf.h | 56 + xen/include/xen/xsplice_patch.h | 95 ++ xen/include/xsm/dummy.h | 41 + xen/include/xsm/xsm.h | 12 + xen/xsm/dummy.c | 2 + xen/xsm/flask/hooks.c | 91 ++ xen/xsm/flask/policy/access_vectors | 52 + xen/xsm/flask/policy/security_classes | 1 + 90 files changed, 6661 insertions(+), 307 deletions(-) Konrad Rzeszutek Wilk (24): compat/x86: Remove unncessary #define. libxc: Remove dead code (XENVER_capabilities) xsm/xen_version: Add XSM for the xen_version hypercall HYPERCALL_version_op. New hypercall mirroring XENVER_ but sane. libxc/libxl/python/xenstat: Use new XEN_VERSION_OP hypercall x86/arm: Add BUGFRAME_NR define and BUILD checks. arm/x86: Use struct virtual_region to do bug, symbol, and (x86) exception tables vmap: Make the while loop less fishy. vmap: ASSERT on NULL. vmap: Add vmalloc_cb and vfree_cb xsplice: Design document xen/xsplice: Hypervisor implementation of XEN_XSPLICE_op libxc: Implementation of XEN_XSPLICE_op in libxc xen-xsplice: Tool to manipulate xsplice payloads x86/xen_hello_world.xsplice: Test payload for patching 'xen_extra_version'. xsplice,symbols: Implement symbol name resolution on address. build_id: Provide ld-embedded build-ids HYPERCALL_version_op: Add VERSION_OP_build_id to retrieve build-id. libxl: info: Display build_id of the hypervisor using XEN_VERSION_OP_build_id xsplice: Print build_id in keyhandler and on bootup. xsplice: Stacking build-id dependency checking. xsplice/xen_replace_world: Test-case for XSPLICE_ACTION_REPLACE xsplice: Print dependency and payloads build_id in the keyhandler. MAINTAINERS/xsplice: Add myself and Ross as the maintainers. Ross Lagerwall (10): xsplice: Add helper elf routines xsplice: Implement payload loading xsplice: Implement support for applying/reverting/replacing patches. x86, xsplice: Print payload's symbol name and payload name in backtraces xsplice: Add .xsplice.hooks functions and test-case xsplice: Add support for bug frames. xsplice: Add support for exception tables. xsplice: Add support for alternatives xsplice: Prevent duplicate payloads to be loaded. xsplice: Add support for shadow variables. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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