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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v10] xSplice v1 design and implementation.
Hey! Changelog: Since v9: [http://lists.xen.org/archives/html/xen-devel/2016-04/msg03052.html] - Worked on Ross's and Jan's comments. v8.1: http://lists.xen.org/archives/html/xen-devel/2016-04/msg01903.html - Worked on Jan's comments. v8: since http://lists.xen.org/archives/html/xen-devel/2016-04/msg01873.html - Posting the _RIGHT_ set of patches. v7: http://lists.xen.org/archives/html/xen-devel/2016-04/msg01476.html - Ingested newer version of x86/mm: Introduce modify_xen_mappings() - Implemented faster symbol table lookup (NEW) - Carried out tests on large CPU machine (240CPUs) - Made the struct xsplice_patch_func work on ARM32 and changed its size (64bit it is 64bytes, 32bit is 52 bytes - and the offset is different too) - Changed a bunch of printk to dprintk, adjusted XENLOG_ levels. - Resurrected the XENVER_build_id. - Reverted VERSION_op. v6: http://lists.xen.org/archives/html/xen-devel/2016-04/msg00871.html - Acted on all comments from Andrew, Julien, and Jan. - Got help from Andrew on one of them over the weekend. - Dropped: xsplice: Add .xsplice.hooks functions and test-case, xsplice: Add support for shadow variables. v5: http://lists.xen.org/archives/html/xen-devel/2016-03/msg03286.html - Acted at all comments from Jan. v4: http://lists.xen.org/archives/html/xen-devel/2016-03/msg01776.html - Lots of review. Lots of rework. Some patches checked in. 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 *Maintainers* Legend: * - See below R - Reviewed R+ - Reviewed by two folks A - Acked by maintainer of the area (hypervisor or toolstack) A xsplice: Design document R xen/xsplice: Hypervisor implementation of XEN_XSPLICE_op AR libxc: Implementation of XEN_XSPLICE_op in libxc A xen-xsplice: Tool to manipulate xsplice payloads AR arm/x86: Use struct virtual_region to do bug, symbol, and (x86) exception tables lookup. AR arm/x86/vmap: Add v[z|m]alloc_xen, vfree_xen and vm_init_type * A xsplice: Add helper elf routines [Ian acked it] * A xsplice: Implement payload loading [Julien Acked the ARM part, Needs Jan's Review or Ack]] A+ xsplice: Implement support for applying/reverting/replacing patches. AR x86/xen_hello_world.xsplice: Test payload for patching 'xen_extra_version'. AR xsplice,symbols: Implement symbol name resolution on address. AR xsplice, symbols: Implement fast symbol names -> virtual addresses lookup R+ x86, xsplice: Print payload's symbol name and payload name in backtraces R+ xsplice: Add support for bug frames. R+ xsplice: Add support for exception tables. R+ xsplice: Add support for alternatives AR build_id: Provide ld-embedded build-ids AR xsplice: Print build_id in keyhandler and on bootup. A XENVER_build_id/libxc: Provide ld-embedded build-id A libxl: info: Display build_id of the hypervisor. * xsplice: Stacking build-id dependency checking. * xsplice/xen_replace_world: Test-case for XSPLICE_ACTION_REPLACE R xsplice: Prevent duplicate payloads from being loaded. R MAINTAINERS/xsplice: Add myself and Ross as the maintainers. *Are there any TODOs left from v9 reviews?* These two need a simple review. I've also posted them inline in v9 review but that is harder to read. #7 xsplice: Add helper elf routines #8 xsplice: Implement payload loading And these two have makefile changes: #21 xsplice: Stacking build-id dependency checking. #22 xsplice/xen_replace_world: Test-case for XSPLICE_ACTION_REPLACE *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.v10 (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 | 5 + Config.mk | 12 + MAINTAINERS | 10 + docs/misc/xsplice.markdown | 1103 ++++++++++++++++++ tools/flask/policy/policy/modules/xen/xen.te | 2 + tools/libxc/include/xenctrl.h | 61 + tools/libxc/xc_misc.c | 350 ++++++ tools/libxc/xc_private.c | 7 + tools/libxc/xc_private.h | 11 + tools/libxl/libxl.c | 44 + tools/libxl/libxl.h | 6 + tools/libxl/libxl_types.idl | 1 + tools/libxl/xl_cmdimpl.c | 1 + tools/misc/Makefile | 4 + tools/misc/xen-xsplice.c | 463 ++++++++ xen/Makefile | 8 +- xen/arch/arm/Makefile | 6 +- xen/arch/arm/kernel.c | 2 +- xen/arch/arm/mm.c | 2 +- xen/arch/arm/setup.c | 4 + xen/arch/arm/traps.c | 39 +- xen/arch/arm/xen.lds.S | 15 +- xen/arch/arm/xsplice.c | 79 ++ xen/arch/x86/Makefile | 58 +- xen/arch/x86/alternative.c | 46 +- xen/arch/x86/boot/mkelf32.c | 142 ++- xen/arch/x86/domain.c | 6 + xen/arch/x86/extable.c | 41 +- xen/arch/x86/mm.c | 2 +- xen/arch/x86/platform_hypercall.c | 5 +- xen/arch/x86/setup.c | 6 + xen/arch/x86/test/Makefile | 88 ++ xen/arch/x86/test/xen_bye_world.c | 34 + xen/arch/x86/test/xen_bye_world_func.c | 22 + xen/arch/x86/test/xen_hello_world.c | 33 + xen/arch/x86/test/xen_hello_world_func.c | 39 + xen/arch/x86/test/xen_replace_world.c | 33 + xen/arch/x86/test/xen_replace_world_func.c | 22 + xen/arch/x86/traps.c | 45 +- xen/arch/x86/xen.lds.S | 30 +- xen/arch/x86/xsplice.c | 249 +++++ xen/common/Kconfig | 28 + xen/common/Makefile | 3 + xen/common/kernel.c | 36 + xen/common/symbols-dummy.c | 5 + xen/common/symbols.c | 75 +- xen/common/sysctl.c | 7 + xen/common/version.c | 75 ++ xen/common/virtual_region.c | 146 +++ xen/common/vmap.c | 169 +-- xen/common/vsprintf.c | 12 + xen/common/xsplice.c | 1556 ++++++++++++++++++++++++++ xen/common/xsplice_elf.c | 503 +++++++++ xen/drivers/acpi/osl.c | 2 +- xen/include/asm-x86/alternative.h | 4 + xen/include/asm-x86/current.h | 10 +- xen/include/asm-x86/uaccess.h | 2 + xen/include/public/sysctl.h | 185 +++ xen/include/public/version.h | 18 +- xen/include/xen/elfstructs.h | 8 + xen/include/xen/symbols.h | 21 +- xen/include/xen/version.h | 1 + xen/include/xen/virtual_region.h | 47 + xen/include/xen/vmap.h | 21 +- xen/include/xen/xsplice.h | 119 ++ xen/include/xen/xsplice_elf.h | 58 + xen/tools/symbols.c | 50 +- xen/xsm/flask/hooks.c | 7 + xen/xsm/flask/policy/access_vectors | 4 + 69 files changed, 6123 insertions(+), 185 deletions(-) Konrad Rzeszutek Wilk (15): 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 arm/x86: Use struct virtual_region to do bug, symbol, and (x86) exception tables lookup. arm/x86/vmap: Add vmalloc_xen and vm_init_type x86/xen_hello_world.xsplice: Test payload for patching 'xen_extra_version'. xsplice, symbols: Implement fast symbol names -> virtual addresses lookup build_id: Provide ld-embedded build-ids xsplice: Print build_id in keyhandler and on bootup. XENVER_build_id/libxc: Provide ld-embedded build-id libxl: info: Display build_id of the hypervisor. xsplice: Stacking build-id dependency checking. xsplice/xen_replace_world: Test-case for XSPLICE_ACTION_REPLACE MAINTAINERS/xsplice: Add myself and Ross as the maintainers. Ross Lagerwall (9): xsplice: Add helper elf routines xsplice: Implement payload loading xsplice: Implement support for applying/reverting/replacing patches. xsplice,symbols: Implement symbol name resolution on address. x86, xsplice: Print payload's symbol name and payload name in backtraces xsplice: Add support for bug frames. xsplice: Add support for exception tables. xsplice: Add support for alternatives xsplice: Prevent duplicate payloads from being loaded. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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