From patchwork Wed Aug 28 23:27:16 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 823753 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 14CC516078B; Wed, 28 Aug 2024 23:28:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724887712; cv=none; b=bCI/C6PQK/Opart8bewWRUTqv+H6c0pN80Q8j05E7z9W6vVAMjbtJtI+w2TPEu+Llcbp4+0lmokoy6cTZMFVqRRMv+OmEkmh328xcEgIlp+1R95MWVgpG7PhAhHy7Z4gCHKSKuswTiZFu1aQgxlqOrGDjwGZW0+D67gVvCGdh74= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724887712; c=relaxed/simple; bh=J0RMfc52lCw4O9UO/SflfJIRipiZAWJ0sVLJlJJCFdk=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=o104yaPha4xSOSPwbIC6lEpZvGLbNyQkzJddXDE/TtRGFKG4Tsm6uIS8ZYa/EKxN9hhLPIHTw9Mx6gQC4rBmjgSsZR4HKiqTDuKH4TD9uIKdyP0XU2HEDgjjuzul+QEYiPqXrteP10UiqFQQjCv5qDJI5VAZ3o3C9Kj2JZD23Pw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=f5qVZE6P; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="f5qVZE6P" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0909EC4CEC0; Wed, 28 Aug 2024 23:28:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724887711; bh=J0RMfc52lCw4O9UO/SflfJIRipiZAWJ0sVLJlJJCFdk=; h=From:Subject:Date:To:Cc:From; b=f5qVZE6P2WTL9ZB6EUy6u8VhoRnDwwDi9bxPFkYnSiiIU62BvEirjXxcbYlB2fPdI DNPbzHOSG1Ceu3p5eX4LUHD1+tlf471uWcDVz4TjIw47tyyD1278q5HPvIAl+EVRPI kYvbAhhHy6Dm1ehyzvuF9+x5bnsOge0UTcCMD4JsmTpVpCOu1vm5pAeDPZsxOiekoQ Tb7LttfAnGT8ixDVAkBkorhHlF7eVX3CABIvSq/OHgLyhmZdxzpbgLP9hojczp+0Ds C+rVFPa4zCE9Etp18IUcPJuLbliI3pXJlJpB3aD2cQmrRv9IJR2DJdeAUdVhyB1Eqi EGFaA2q/CBRjQ== From: Mark Brown Subject: [PATCH v12 00/39] arm64/gcs: Provide support for GCS in userspace Date: Thu, 29 Aug 2024 00:27:16 +0100 Message-Id: <20240829-arm64-gcs-v12-0-42fec947436a@kernel.org> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAFayz2YC/2XSzW7DIAwA4Fepcl4m2xB+dtp7TDvwY9poa1qRK tpU9d1HOm0lQpxs8dmAuXYz55Hn7mV37TIv4zyephIgPe26cHDTnvsxlkRHQALK6l0+Ktnvw9y zQHQeotFku7Lfu5l7n90UDqu4HM9r9pw5jV/3Fm/vJT6M8+WUv+8dF1yzv7U1qqr2gj30Pg1KJ yu8d+r1g/PEn8+nvO/WMgtVlGRNqdAYKGCUMhD7hoqKCqypKDTEmGyyBqI1DZUPakDXVBaqTEh OlCODsg0dKkpU06FQywkNxqgEyYaqf4oAtqaqUG14GCI7J2NsqH5Q3HbVhRJgkEb4qPXQUPNHJ dBm8ItZn8kmDlorLTg11D6ooqGmtlBISkiprDcJGorwsAY200FY39haJh8JLbSTRazw9rq4/ii J3qCVmoPf3vd2u/0AcGOELAwDAAA= To: Catalin Marinas , Will Deacon , Jonathan Corbet , Andrew Morton , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Arnd Bergmann , Oleg Nesterov , Eric Biederman , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , Kees Cook Cc: "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Florian Weimer , Christian Brauner , Thiago Jung Bauermann , Ross Burton , Yury Khrustalev , Wilco Dijkstra , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Mark Brown , David Hildenbrand , "Mike Rapoport (IBM)" , Kees Cook , Shuah Khan X-Mailer: b4 0.15-dev-37811 X-Developer-Signature: v=1; a=openpgp-sha256; l=16341; i=broonie@kernel.org; h=from:subject:message-id; bh=J0RMfc52lCw4O9UO/SflfJIRipiZAWJ0sVLJlJJCFdk=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBmz7J4XDMhBJhYEXCdFtuPf6bRbdo8PujMOln3Vl6g MayWoDaJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZs+yeAAKCRAk1otyXVSH0AOqB/ 9bGoOtn8XBfAZlx2oLlPcGDB73pSzYrm5Gmeo3MHHFxk9jdQGSS/OcifXLi/WcxmS3UZIh9+df1aV+ mX94ykh1J+rOxkUnP6de6bd0hUtOHVs/d/4BsfmmhbWBZtcCww7JclveZZ2FSx6GaX4X42De/88ww5 Fa4HjJFTaQ1Ta6JpqrUzEw/CS5l5v5A/butIiF4Gn3p8URU9lfRQ16iS/YzdkJ70hW7My6X6vdm6ok fnn8DW5HfCiKzSAxwqMRQosn/xXrWuW0Dr3si5aFBEF5+XfGUphVGOdlaVl633bWrVMgZqJmmjYj0m OjGQWRUe6wHIi27WCFFTfIupzJYwZm X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB The arm64 Guarded Control Stack (GCS) feature provides support for hardware protected stacks of return addresses, intended to provide hardening against return oriented programming (ROP) attacks and to make it easier to gather call stacks for applications such as profiling. When GCS is active a secondary stack called the Guarded Control Stack is maintained, protected with a memory attribute which means that it can only be written with specific GCS operations. The current GCS pointer can not be directly written to by userspace. When a BL is executed the value stored in LR is also pushed onto the GCS, and when a RET is executed the top of the GCS is popped and compared to LR with a fault being raised if the values do not match. GCS operations may only be performed on GCS pages, a data abort is generated if they are not. The combination of hardware enforcement and lack of extra instructions in the function entry and exit paths should result in something which has less overhead and is more difficult to attack than a purely software implementation like clang's shadow stacks. This series implements support for use of GCS by userspace, along with support for use of GCS within KVM guests. It does not enable use of GCS by either EL1 or EL2, this will be implemented separately. Executables are started without GCS and must use a prctl() to enable it, it is expected that this will be done very early in application execution by the dynamic linker or other startup code. For dynamic linking this will be done by checking that everything in the executable is marked as GCS compatible. x86 has an equivalent feature called shadow stacks, this series depends on the x86 patches for generic memory management support for the new guarded/shadow stack page type and shares APIs as much as possible. As there has been extensive discussion with the wider community around the ABI for shadow stacks I have as far as practical kept implementation decisions close to those for x86, anticipating that review would lead to similar conclusions in the absence of strong reasoning for divergence. The main divergence I am concious of is that x86 allows shadow stack to be enabled and disabled repeatedly, freeing the shadow stack for the thread whenever disabled, while this implementation keeps the GCS allocated after disable but refuses to reenable it. This is to avoid races with things actively walking the GCS during a disable, we do anticipate that some systems will wish to disable GCS at runtime but are not aware of any demand for subsequently reenabling it. x86 uses an arch_prctl() to manage enable and disable, since only x86 and S/390 use arch_prctl() a generic prctl() was proposed[1] as part of a patch set for the equivalent RISC-V Zicfiss feature which I initially adopted fairly directly but following review feedback has been revised quite a bit. We currently maintain the x86 pattern of implicitly allocating a shadow stack for threads started with shadow stack enabled, there has been some discussion of removing this support and requiring the use of clone3() with explicit allocation of shadow stacks instead. I have no strong feelings either way, implicit allocation is not really consistent with anything else we do and creates the potential for errors around thread exit but on the other hand it is existing ABI on x86 and minimises the changes needed in userspace code. glibc and bionic changes using this ABI have been implemented and tested. Headless Android systems have been validated and Ross Burton has used this code has been used to bring up a Yocto system with GCS enabed as standard, a test implementation of V8 support has also been done. uprobes are not currently supported, missing emulation was identified late in review. There is an open issue with support for CRIU, on x86 this required the ability to set the GCS mode via ptrace. This series supports configuring mode bits other than enable/disable via ptrace but it needs to be confirmed if this is sufficient. It is likely that we could relax some of the barriers added here with some more targeted placements, this is left for further study. There is an in process series adding clone3() support for shadow stacks: https://lore.kernel.org/r/20240819-clone3-shadow-stack-v9-0-962d74f99464@kernel.org Previous versions of this series depended on that, this dependency has been removed in order to make merging easier. [1] https://lore.kernel.org/lkml/20230213045351.3945824-1-debug@rivosinc.com/ Signed-off-by: Mark Brown --- Changes in v12: - Clarify and simplify the signal handling code so we work with the register state. - When checking for write aborts to shadow stack pages ensure the fault is a data abort. - Depend on !UPROBES. - Comment cleanups. - Link to v11: https://lore.kernel.org/r/20240822-arm64-gcs-v11-0-41b81947ecb5@kernel.org Changes in v11: - Remove the dependency on the addition of clone3() support for shadow stacks, rebasing onto v6.11-rc3. - Make ID_AA64PFR1_EL1.GCS writeable in KVM. - Hide GCS registers when GCS is not enabled for KVM guests. - Require HCRX_EL2.GCSEn if booting at EL1. - Require that GCSCR_EL1 and GCSCRE0_EL1 be initialised regardless of if we boot at EL2 or EL1. - Remove some stray use of bit 63 in signal cap tokens. - Warn if we see a GCS with VM_SHARED. - Remove rdundant check for VM_WRITE in fault handling. - Cleanups and clarifications in the ABI document. - Clean up and improve documentation of some sync placement. - Only set the EL0 GCS mode if it's actually changed. - Various minor fixes and tweaks. - Link to v10: https://lore.kernel.org/r/20240801-arm64-gcs-v10-0-699e2bd2190b@kernel.org Changes in v10: - Fix issues with THP. - Tighten up requirements for initialising GCSCR*. - Only generate GCS signal frames for threads using GCS. - Only context switch EL1 GCS registers if S1PIE is enabled. - Move context switch of GCSCRE0_EL1 to EL0 context switch. - Make GCS registers unconditionally visible to userspace. - Use FHU infrastructure. - Don't change writability of ID_AA64PFR1_EL1 for KVM. - Remove unused arguments from alloc_gcs(). - Typo fixes. - Link to v9: https://lore.kernel.org/r/20240625-arm64-gcs-v9-0-0f634469b8f0@kernel.org Changes in v9: - Rebase onto v6.10-rc3. - Restructure and clarify memory management fault handling. - Fix up basic-gcs for the latest clone3() changes. - Convert to newly merged KVM ID register based feature configuration. - Fixes for NV traps. - Link to v8: https://lore.kernel.org/r/20240203-arm64-gcs-v8-0-c9fec77673ef@kernel.org Changes in v8: - Invalidate signal cap token on stack when consuming. - Typo and other trivial fixes. - Don't try to use process_vm_write() on GCS, it intentionally does not work. - Fix leak of thread GCSs. - Rebase onto latest clone3() series. - Link to v7: https://lore.kernel.org/r/20231122-arm64-gcs-v7-0-201c483bd775@kernel.org Changes in v7: - Rebase onto v6.7-rc2 via the clone3() patch series. - Change the token used to cap the stack during signal handling to be compatible with GCSPOPM. - Fix flags for new page types. - Fold in support for clone3(). - Replace copy_to_user_gcs() with put_user_gcs(). - Link to v6: https://lore.kernel.org/r/20231009-arm64-gcs-v6-0-78e55deaa4dd@kernel.org Changes in v6: - Rebase onto v6.6-rc3. - Add some more gcsb_dsync() barriers following spec clarifications. - Due to ongoing discussion around clone()/clone3() I've not updated anything there, the behaviour is the same as on previous versions. - Link to v5: https://lore.kernel.org/r/20230822-arm64-gcs-v5-0-9ef181dd6324@kernel.org Changes in v5: - Don't map any permissions for user GCSs, we always use EL0 accessors or use a separate mapping of the page. - Reduce the standard size of the GCS to RLIMIT_STACK/2. - Enforce a PAGE_SIZE alignment requirement on map_shadow_stack(). - Clarifications and fixes to documentation. - More tests. - Link to v4: https://lore.kernel.org/r/20230807-arm64-gcs-v4-0-68cfa37f9069@kernel.org Changes in v4: - Implement flags for map_shadow_stack() allowing the cap and end of stack marker to be enabled independently or not at all. - Relax size and alignment requirements for map_shadow_stack(). - Add more blurb explaining the advantages of hardware enforcement. - Link to v3: https://lore.kernel.org/r/20230731-arm64-gcs-v3-0-cddf9f980d98@kernel.org Changes in v3: - Rebase onto v6.5-rc4. - Add a GCS barrier on context switch. - Add a GCS stress test. - Link to v2: https://lore.kernel.org/r/20230724-arm64-gcs-v2-0-dc2c1d44c2eb@kernel.org Changes in v2: - Rebase onto v6.5-rc3. - Rework prctl() interface to allow each bit to be locked independently. - map_shadow_stack() now places the cap token based on the size requested by the caller not the actual space allocated. - Mode changes other than enable via ptrace are now supported. - Expand test coverage. - Various smaller fixes and adjustments. - Link to v1: https://lore.kernel.org/r/20230716-arm64-gcs-v1-0-bf567f93bba6@kernel.org --- Mark Brown (39): mm: Introduce ARCH_HAS_USER_SHADOW_STACK arm64/mm: Restructure arch_validate_flags() for extensibility prctl: arch-agnostic prctl for shadow stack mman: Add map_shadow_stack() flags arm64: Document boot requirements for Guarded Control Stacks arm64/gcs: Document the ABI for Guarded Control Stacks arm64/sysreg: Add definitions for architected GCS caps arm64/gcs: Add manual encodings of GCS instructions arm64/gcs: Provide put_user_gcs() arm64/gcs: Provide basic EL2 setup to allow GCS usage at EL0 and EL1 arm64/cpufeature: Runtime detection of Guarded Control Stack (GCS) arm64/mm: Allocate PIE slots for EL0 guarded control stack mm: Define VM_SHADOW_STACK for arm64 when we support GCS arm64/mm: Map pages for guarded control stack KVM: arm64: Manage GCS access and registers for guests arm64/idreg: Add overrride for GCS arm64/hwcap: Add hwcap for GCS arm64/traps: Handle GCS exceptions arm64/mm: Handle GCS data aborts arm64/gcs: Context switch GCS state for EL0 arm64/gcs: Ensure that new threads have a GCS arm64/gcs: Implement shadow stack prctl() interface arm64/mm: Implement map_shadow_stack() arm64/signal: Set up and restore the GCS context for signal handlers arm64/signal: Expose GCS state in signal frames arm64/ptrace: Expose GCS via ptrace and core files arm64: Add Kconfig for Guarded Control Stack (GCS) kselftest/arm64: Verify the GCS hwcap kselftest/arm64: Add GCS as a detected feature in the signal tests kselftest/arm64: Add framework support for GCS to signal handling tests kselftest/arm64: Allow signals tests to specify an expected si_code kselftest/arm64: Always run signals tests with GCS enabled kselftest/arm64: Add very basic GCS test program kselftest/arm64: Add a GCS test program built with the system libc kselftest/arm64: Add test coverage for GCS mode locking kselftest/arm64: Add GCS signal tests kselftest/arm64: Add a GCS stress test kselftest/arm64: Enable GCS for the FP stress tests KVM: selftests: arm64: Add GCS registers to get-reg-list Documentation/admin-guide/kernel-parameters.txt | 3 + Documentation/arch/arm64/booting.rst | 32 + Documentation/arch/arm64/elf_hwcaps.rst | 2 + Documentation/arch/arm64/gcs.rst | 230 +++++++ Documentation/arch/arm64/index.rst | 1 + Documentation/filesystems/proc.rst | 2 +- arch/arm64/Kconfig | 21 + arch/arm64/include/asm/cpufeature.h | 6 + arch/arm64/include/asm/el2_setup.h | 29 + arch/arm64/include/asm/esr.h | 28 +- arch/arm64/include/asm/exception.h | 2 + arch/arm64/include/asm/gcs.h | 107 +++ arch/arm64/include/asm/hwcap.h | 1 + arch/arm64/include/asm/kvm_host.h | 12 + arch/arm64/include/asm/mman.h | 23 +- arch/arm64/include/asm/pgtable-prot.h | 14 +- arch/arm64/include/asm/processor.h | 7 + arch/arm64/include/asm/sysreg.h | 20 + arch/arm64/include/asm/uaccess.h | 40 ++ arch/arm64/include/asm/vncr_mapping.h | 2 + arch/arm64/include/uapi/asm/hwcap.h | 1 + arch/arm64/include/uapi/asm/ptrace.h | 8 + arch/arm64/include/uapi/asm/sigcontext.h | 9 + arch/arm64/kernel/cpufeature.c | 12 + arch/arm64/kernel/cpuinfo.c | 1 + arch/arm64/kernel/entry-common.c | 23 + arch/arm64/kernel/pi/idreg-override.c | 2 + arch/arm64/kernel/process.c | 88 +++ arch/arm64/kernel/ptrace.c | 54 ++ arch/arm64/kernel/signal.c | 227 ++++++- arch/arm64/kernel/traps.c | 11 + arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 49 +- arch/arm64/kvm/sys_regs.c | 27 +- arch/arm64/mm/Makefile | 1 + arch/arm64/mm/fault.c | 40 ++ arch/arm64/mm/gcs.c | 252 +++++++ arch/arm64/mm/mmap.c | 9 +- arch/arm64/tools/cpucaps | 1 + arch/x86/Kconfig | 1 + arch/x86/include/uapi/asm/mman.h | 3 - fs/proc/task_mmu.c | 2 +- include/linux/mm.h | 18 +- include/uapi/asm-generic/mman.h | 4 + include/uapi/linux/elf.h | 1 + include/uapi/linux/prctl.h | 22 + kernel/sys.c | 30 + mm/Kconfig | 6 + tools/testing/selftests/arm64/Makefile | 2 +- tools/testing/selftests/arm64/abi/hwcap.c | 19 + tools/testing/selftests/arm64/fp/assembler.h | 15 + tools/testing/selftests/arm64/fp/fpsimd-test.S | 2 + tools/testing/selftests/arm64/fp/sve-test.S | 2 + tools/testing/selftests/arm64/fp/za-test.S | 2 + tools/testing/selftests/arm64/fp/zt-test.S | 2 + tools/testing/selftests/arm64/gcs/.gitignore | 5 + tools/testing/selftests/arm64/gcs/Makefile | 24 + tools/testing/selftests/arm64/gcs/asm-offsets.h | 0 tools/testing/selftests/arm64/gcs/basic-gcs.c | 357 ++++++++++ tools/testing/selftests/arm64/gcs/gcs-locking.c | 200 ++++++ .../selftests/arm64/gcs/gcs-stress-thread.S | 311 +++++++++ tools/testing/selftests/arm64/gcs/gcs-stress.c | 530 +++++++++++++++ tools/testing/selftests/arm64/gcs/gcs-util.h | 100 +++ tools/testing/selftests/arm64/gcs/libc-gcs.c | 728 +++++++++++++++++++++ tools/testing/selftests/arm64/signal/.gitignore | 1 + .../testing/selftests/arm64/signal/test_signals.c | 17 +- .../testing/selftests/arm64/signal/test_signals.h | 6 + .../selftests/arm64/signal/test_signals_utils.c | 32 +- .../selftests/arm64/signal/test_signals_utils.h | 39 ++ .../arm64/signal/testcases/gcs_exception_fault.c | 62 ++ .../selftests/arm64/signal/testcases/gcs_frame.c | 88 +++ .../arm64/signal/testcases/gcs_write_fault.c | 67 ++ .../selftests/arm64/signal/testcases/testcases.c | 7 + .../selftests/arm64/signal/testcases/testcases.h | 1 + tools/testing/selftests/kvm/aarch64/get-reg-list.c | 28 + 74 files changed, 4088 insertions(+), 43 deletions(-) --- base-commit: 7c626ce4bae1ac14f60076d00eafe71af30450ba change-id: 20230303-arm64-gcs-e311ab0d8729 Best regards,