- 01 Apr, 2020 4 commits
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Ard Biesheuvel authored
When CONFIG_DEBUG_ALIGN_RODATA is enabled, kernel segments mapped with different permissions (r-x for .text, r-- for .rodata, rw- for .data, etc) are rounded up to 2 MiB so they can be mapped more efficiently. In particular, it permits the segments to be mapped using level 2 block entries when using 4k pages, which is expected to result in less TLB pressure. However, the mappings for the bulk of the kernel will use level 2 entries anyway, and the misaligned fringes are organized such that they can take advantage of the contiguous bit, and use far fewer level 3 entries than would be needed otherwise. This makes the value of this feature dubious at best, and since it is not enabled in defconfig or in the distro configs, it does not appear to be in wide use either. So let's just remove it. Signed-off-by:
Ard Biesheuvel <ardb@kernel.org> Acked-by:
Mark Rutland <mark.rutland@arm.com> Acked-by:
Will Deacon <will@kernel.org> Acked-by:
Laura Abbott <labbott@kernel.org> Signed-off-by:
Catalin Marinas <catalin.marinas@arm.com>
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Mark Brown authored
Compilers with branch protection support can be configured to enable it by default, it is likely that distributions will do this as part of deploying branch protection system wide. As well as the slight overhead from having some extra NOPs for unused branch protection features this can cause more serious problems when the kernel is providing pointer authentication to userspace but not built for pointer authentication itself. In that case our switching of keys for userspace can affect the kernel unexpectedly, causing pointer authentication instructions in the kernel to corrupt addresses. To ensure that we get consistent and reliable behaviour always explicitly initialise the branch protection mode, ensuring that the kernel is built the same way regardless of the compiler defaults. Fixes: 75031975 (arm64: add basic pointer authentication support) Reported-by:
Szabolcs Nagy <szabolcs.nagy@arm.com> Signed-off-by:
Mark Brown <broonie@kernel.org> Cc: stable@vger.kernel.org [catalin.marinas@arm.com: remove Kconfig option in favour of Makefile check] Signed-off-by:
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Amit Daniel Kachhap authored
Recent addition of ARM64_PTR_AUTH exposed a mismatch issue with binutils. 9.1+ versions of gcc inserts a section note .note.gnu.property but this can be used properly by binutils version greater than 2.33.1. If older binutils are used then the following warnings are generated, aarch64-linux-ld: warning: arch/arm64/kernel/vdso/vgettimeofday.o: unsupported GNU_PROPERTY_TYPE (5) type: 0xc0000000 aarch64-linux-objdump: warning: arch/arm64/lib/csum.o: unsupported GNU_PROPERTY_TYPE (5) type: 0xc0000000 aarch64-linux-nm: warning: .tmp_vmlinux1: unsupported GNU_PROPERTY_TYPE (5) type: 0xc0000000 This patch enables ARM64_PTR_AUTH when gcc and binutils versions are compatible with each other. Older gcc which do not insert such section continue to work as before. This scenario may not occur with clang as a recent commit 3b446c7d ("arm64: Kconfig: verify binutils support for ARM64_PTR_AUTH") masks binutils version lesser then 2.34. Reported-by:
kbuild test robot <lkp@intel.com> Suggested-by:
Vincenzo Frascino <Vincenzo.Frascino@arm.com> Signed-off-by:
Amit Daniel Kachhap <amit.kachhap@arm.com> [catalin.marinas@arm.com: slight adjustment to the comment] Signed-off-by:
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Amit Daniel Kachhap authored
This option can be used in Kconfig files to compare the ld version and enable/disable incompatible config options if required. This option is used in the subsequent patch along with GCC_VERSION to filter out an incompatible feature. Signed-off-by:
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- 26 Mar, 2020 1 commit
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Will Deacon authored
Commit dcde2373 ("mm: Avoid creating virtual address aliases in brk()/mmap()/mremap()") changed mremap() so that only the 'old' address is untagged, leaving the 'new' address in the form it was passed from userspace. This prevents the unexpected creation of aliasing virtual mappings in userspace, but looks a bit odd when you read the code. Add a comment justifying the untagging behaviour in mremap(). Reported-by:
Linus Torvalds <torvalds@linux-foundation.org> Acked-by:
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- 25 Mar, 2020 5 commits
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Catalin Marinas authored
* for-next/kernel-ptrauth: : Return address signing - in-kernel support arm64: Kconfig: verify binutils support for ARM64_PTR_AUTH lkdtm: arm64: test kernel pointer authentication arm64: compile the kernel with ptrauth return address signing kconfig: Add support for 'as-option' arm64: suspend: restore the kernel ptrauth keys arm64: __show_regs: strip PAC from lr in printk arm64: unwind: strip PAC from kernel addresses arm64: mask PAC bits of __builtin_return_address arm64: initialize ptrauth keys for kernel booting task arm64: initialize and switch ptrauth kernel keys arm64: enable ptrauth earlier arm64: cpufeature: handle conflicts based on capability arm64: cpufeature: Move cpu capability helpers inside C file arm64: ptrauth: Add bootup/runtime flags for __cpu_setup arm64: install user ptrauth keys at kernel exit time arm64: rename ptrauth key structures to be user-specific arm64: cpufeature: add pointer auth meta-capabilities arm64: cpufeature: Fix meta-capability cpufeature check
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Catalin Marinas authored
* for-next/asm-cleanups: : Various asm clean-ups (alignment, mov_q vs ldr, .idmap) arm64: move kimage_vaddr to .rodata arm64: use mov_q instead of literal ldr
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Catalin Marinas authored
* for-next/asm-annotations: : Modernise arm64 assembly annotations arm64: head: Convert install_el2_stub to SYM_INNER_LABEL arm64: Mark call_smc_arch_workaround_1 as __maybe_unused arm64: entry-ftrace.S: Fix missing argument for CONFIG_FUNCTION_GRAPH_TRACER=y arm64: vdso32: Convert to modern assembler annotations arm64: vdso: Convert to modern assembler annotations arm64: sdei: Annotate SDEI entry points using new style annotations arm64: kvm: Modernize __smccc_workaround_1_smc_start annotations arm64: kvm: Modernize annotation for __bp_harden_hyp_vecs arm64: kvm: Annotate assembly using modern annoations arm64: kernel: Convert to modern annotations for assembly data arm64: head: Annotate stext and preserve_boot_args as code arm64: head.S: Convert to modern annotations for assembly functions arm64: ftrace: Modernise annotation of return_to_handler arm64: ftrace: Correct annotation of ftrace_caller assembly arm64: entry-ftrace.S: Convert to modern annotations for assembly functions arm64: entry: Additional annotation conversions for entry.S arm64: entry: Annotate ret_from_fork as code arm64: entry: Annotate vector table and handlers as code arm64: crypto: Modernize names for AES function macros arm64: crypto: Modernize some extra assembly annotations
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Catalin Marinas authored
Merge branches 'for-next/memory-hotremove', 'for-next/arm_sdei', 'for-next/amu', 'for-next/final-cap-helper', 'for-next/cpu_ops-cleanup', 'for-next/misc' and 'for-next/perf' into for-next/core * for-next/memory-hotremove: : Memory hot-remove support for arm64 arm64/mm: Enable memory hot remove arm64/mm: Hold memory hotplug lock while walking for kernel page table dump * for-next/arm_sdei: : SDEI: fix double locking on return from hibernate and clean-up firmware: arm_sdei: clean up sdei_event_create() firmware: arm_sdei: Use cpus_read_lock() to avoid races with cpuhp firmware: arm_sdei: fix possible double-lock on hibernate error path firmware: arm_sdei: fix double-lock on hibernate with shared events * for-next/amu: : ARMv8.4 Activity Monitors support clocksource/drivers/arm_arch_timer: validate arch_timer_rate arm64: use activity monitors for frequency invariance cpufreq: add function to get the hardware max frequency Documentation: arm64: document support for the AMU extension arm64/kvm: disable access to AMU registers from kvm guests arm64: trap to EL1 accesses to AMU counters from EL0 arm64: add support for the AMU extension v1 * for-next/final-cap-helper: : Introduce cpus_have_final_cap_helper(), migrate arm64 KVM to it arm64: kvm: hyp: use cpus_have_final_cap() arm64: cpufeature: add cpus_have_final_cap() * for-next/cpu_ops-cleanup: : cpu_ops[] access code clean-up arm64: Introduce get_cpu_ops() helper function arm64: Rename cpu_read_ops() to init_cpu_ops() arm64: Declare ACPI parking protocol CPU operation if needed * for-next/misc: : Various fixes and clean-ups arm64: define __alloc_zeroed_user_highpage arm64/kernel: Simplify __cpu_up() by bailing out early arm64: remove redundant blank for '=' operator arm64: kexec_file: Fixed code style. arm64: add blank after 'if' arm64: fix spelling mistake "ca not" -> "cannot" arm64: entry: unmask IRQ in el0_sp() arm64: efi: add efi-entry.o to targets instead of extra-$(CONFIG_EFI) arm64: csum: Optimise IPv6 header checksum arch/arm64: fix typo in a comment arm64: remove gratuitious/stray .ltorg stanzas arm64: Update comment for ASID() macro arm64: mm: convert cpu_do_switch_mm() to C arm64: fix NUMA Kconfig typos * for-next/perf: : arm64 perf updates arm64: perf: Add support for ARMv8.5-PMU 64-bit counters KVM: arm64: limit PMU version to PMUv3 for ARMv8.1 arm64: cpufeature: Extract capped perfmon fields arm64: perf: Clean up enable/disable calls perf: arm-ccn: Use scnprintf() for robustness arm64: perf: Support new DT compatibles arm64: perf: Refactor PMU init callbacks perf: arm_spe: Remove unnecessary zero check on 'nr_pages'
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Mark Brown authored
New assembly annotations have recently been introduced which aim to make the way we describe symbols in assembly more consistent. Recently the arm64 assembler was converted to use these but install_el2_stub was missed. Signed-off-by:
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- 24 Mar, 2020 5 commits
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Gavin Shan authored
This introduces get_cpu_ops() to return the CPU operations according to the given CPU index. For now, it simply returns the @cpu_ops[cpu] as before. Also, helper function __cpu_try_die() is introduced to be shared by cpu_die() and ipi_cpu_crash_stop(). So it shouldn't introduce any functional changes. Signed-off-by:
Gavin Shan <gshan@redhat.com> Signed-off-by:
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Gavin Shan authored
This renames cpu_read_ops() to init_cpu_ops() as the function is only called in initialization phase. Also, we will introduce get_cpu_ops() in the subsequent patches, to retireve the CPU operation by the given CPU index. The usage of cpu_read_ops() and get_cpu_ops() are difficult to be distinguished from their names. Signed-off-by:
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Gavin Shan authored
It's obvious we needn't declare the corresponding CPU operation when CONFIG_ARM64_ACPI_PARKING_PROTOCOL is disabled, even it doesn't cause any compiling warnings. Signed-off-by:
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Remi Denis-Courmont authored
This datum is not referenced from .idmap.text: it does not need to be mapped in idmap. Lets move it to .rodata as it is never written to after early boot of the primary CPU. (Maybe .data.ro_after_init would be cleaner though?) Signed-off-by:
Rémi Denis-Courmont <remi@remlab.net> Acked-by:
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Remi Denis-Courmont authored
In practice, this requires only 2 instructions, or even only 1 for the idmap_pg_dir size (with 4 or 64 KiB pages). Only the MAIR values needed more than 2 instructions and it was already converted to mov_q by 95b3f74b. Signed-off-by:
Remi Denis-Courmont <remi.denis.courmont@huawei.com> Signed-off-by:
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- 20 Mar, 2020 1 commit
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Nick Desaulniers authored
Clang relies on GNU as from binutils to assemble the Linux kernel, currently. A recent patch to enable the armv8.3-a extension for pointer authentication checked for compiler support of the relevant flags. Everything works with binutils 2.34+, but for older versions we observe assembler errors: /tmp/vgettimeofday-36a54b.s: Assembler messages: /tmp/vgettimeofday-36a54b.s:40: Error: unknown pseudo-op: `.cfi_negate_ra_state' When compiling with Clang, require the assembler to support .cfi_negate_ra_state directives, in order to support CONFIG_ARM64_PTR_AUTH. Link: https://github.com/ClangBuiltLinux/linux/issues/938Signed-off-by:
Nick Desaulniers <ndesaulniers@google.com> Signed-off-by:
Nathan Chancellor <natechancellor@gmail.com> Tested-by:
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- 18 Mar, 2020 17 commits
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Amit Daniel Kachhap authored
This test is specific for arm64. When in-kernel Pointer Authentication config is enabled, the return address stored in the stack is signed. This feature helps in ROP kind of attack. If any parameters used to generate the pac (<key, sp, lr>) is modified then this will fail in the authentication stage and will lead to abort. This test changes the input parameter APIA kernel keys to cause abort. The pac computed from the new key can be same as last due to hash collision so this is retried for few times as there is no reliable way to compare the pacs. Even though this test may fail even after retries but this may cause authentication failure at a later stage in earlier function returns. This test can be invoked as, echo CORRUPT_PAC > /sys/kernel/debug/provoke-crash/DIRECT or as below if inserted as a module, insmod lkdtm.ko cpoint_name=DIRECT cpoint_type=CORRUPT_PAC cpoint_count=1 [ 13.118166] lkdtm: Performing direct entry CORRUPT_PAC [ 13.118298] lkdtm: Clearing PAC from the return address [ 13.118466] Unable to handle kernel paging request at virtual address bfff8000108648ec [ 13.118626] Mem abort info: [ 13.118666] ESR = 0x86000004 [ 13.118866] EC = 0x21: IABT (current EL), IL = 32 bits [ 13.118966] SET = 0, FnV = 0 [ 13.119117] EA = 0, S1PTW = 0 Signed-off-by:
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Kristina Martsenko authored
Compile all functions with two ptrauth instructions: PACIASP in the prologue to sign the return address, and AUTIASP in the epilogue to authenticate the return address (from the stack). If authentication fails, the return will cause an instruction abort to be taken, followed by an oops and killing the task. This should help protect the kernel against attacks using return-oriented programming. As ptrauth protects the return address, it can also serve as a replacement for CONFIG_STACKPROTECTOR, although note that it does not protect other parts of the stack. The new instructions are in the HINT encoding space, so on a system without ptrauth they execute as NOPs. CONFIG_ARM64_PTR_AUTH now not only enables ptrauth for userspace and KVM guests, but also automatically builds the kernel with ptrauth instructions if the compiler supports it. If there is no compiler support, we do not warn that the kernel was built without ptrauth instructions. GCC 7 and 8 support the -msign-return-address option, while GCC 9 deprecates that option and replaces it with -mbranch-protection. Support both options. Clang uses an external assembler hence this patch makes sure that the correct parameters (-march=armv8.3-a) are passed down to help it recognize the ptrauth instructions. Ftrace function tracer works properly with Ptrauth only when patchable-function-entry feature is present and is ensured by the Kconfig dependency. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Reviewed-by:
Kees Cook <keescook@chromium.org> Reviewed-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com> # not co-dev parts Co-developed-by:
Kristina Martsenko <kristina.martsenko@arm.com> [Amit: Cover leaf function, comments, Ftrace Kconfig] Signed-off-by:
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Vincenzo Frascino authored
Currently kconfig does not have a feature that allows to detect if the used assembler supports a specific compilation option. Introduce 'as-option' to serve this purpose in the context of Kconfig: config X def_bool $(as-option,...) Signed-off-by:Masahiro Yamada <masahiroy@kernel.org> Cc: linux-kbuild@vger.kernel.org Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Signed-off-by:
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Amit Daniel Kachhap authored
This patch restores the kernel keys from current task during cpu resume after the mmu is turned on and ptrauth is enabled. A flag is added in macro ptrauth_keys_install_kernel to check if isb instruction needs to be executed. Signed-off-by:
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Amit Daniel Kachhap authored
lr is printed with %pS which will try to find an entry in kallsyms. After enabling pointer authentication, this match will fail due to PAC present in the lr. Strip PAC from the lr to display the correct symbol name. Suggested-by:
James Morse <james.morse@arm.com> Signed-off-by:
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Mark Rutland authored
When we enable pointer authentication in the kernel, LR values saved to the stack will have a PAC which we must strip in order to retrieve the real return address. Strip PACs when unwinding the stack in order to account for this. When function graph tracer is used with patchable-function-entry then return_to_handler will also have pac bits so strip it too. Reviewed-by:
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Amit Daniel Kachhap authored
Functions like vmap() record how much memory has been allocated by their callers, and callers are identified using __builtin_return_address(). Once the kernel is using pointer-auth the return address will be signed. This means it will not match any kernel symbol, and will vary between threads even for the same caller. The output of /proc/vmallocinfo in this case may look like, 0x(____ptrval____)-0x(____ptrval____) 20480 0x86e28000100e7c60 pages=4 vmalloc N0=4 0x(____ptrval____)-0x(____ptrval____) 20480 0x86e28000100e7c60 pages=4 vmalloc N0=4 0x(____ptrval____)-0x(____ptrval____) 20480 0xc5c78000100e7c60 pages=4 vmalloc N0=4 The above three 64bit values should be the same symbol name and not different LR values. Use the pre-processor to add logic to clear the PAC to __builtin_return_address() callers. This patch adds a new file asm/compiler.h and is transitively included via include/compiler_types.h on the compiler command line so it is guaranteed to be loaded and the users of this macro will not find a wrong version. Helper macros ptrauth_kernel_pac_mask/ptrauth_clear_pac are created for this purpose and added in this file. Existing macro ptrauth_user_pac_mask moved from asm/pointer_auth.h. Signed-off-by:
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Amit Daniel Kachhap authored
This patch uses the existing boot_init_stack_canary arch function to initialize the ptrauth keys for the booting task in the primary core. The requirement here is that it should be always inline and the caller must never return. As pointer authentication too detects a subset of stack corruption so it makes sense to place this code here. Both pointer authentication and stack canary codes are protected by their respective config option. Suggested-by:
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Kristina Martsenko authored
Set up keys to use pointer authentication within the kernel. The kernel will be compiled with APIAKey instructions, the other keys are currently unused. Each task is given its own APIAKey, which is initialized during fork. The key is changed during context switch and on kernel entry from EL0. The keys for idle threads need to be set before calling any C functions, because it is not possible to enter and exit a function with different keys. Reviewed-by:
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Kristina Martsenko authored
When the kernel is compiled with pointer auth instructions, the boot CPU needs to start using address auth very early, so change the cpucap to account for this. Pointer auth must be enabled before we call C functions, because it is not possible to enter a function with pointer auth disabled and exit it with pointer auth enabled. Note, mismatches between architected and IMPDEF algorithms will still be caught by the cpufeature framework (the separate *_ARCH and *_IMP_DEF cpucaps). Note the change in behavior: if the boot CPU has address auth and a late CPU does not, then the late CPU is parked by the cpufeature framework. This is possible as kernel will only have NOP space intructions for PAC so such mismatched late cpu will silently ignore those instructions in C functions. Also, if the boot CPU does not have address auth and the late CPU has then the late cpu will still boot but with ptrauth feature disabled. Leave generic authentication as a "system scope" cpucap for now, since initially the kernel will only use address authentication. Reviewed-by:
Suzuki K Poulose <suzuki.poulose@arm.com> Reviewed-by:
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Kristina Martsenko authored
Each system capability can be of either boot, local, or system scope, depending on when the state of the capability is finalized. When we detect a conflict on a late CPU, we either offline the CPU or panic the system. We currently always panic if the conflict is caused by a boot scope capability, and offline the CPU if the conflict is caused by a local or system scope capability. We're going to want to add a new capability (for pointer authentication) which needs to be boot scope but doesn't need to panic the system when a conflict is detected. So add a new flag to specify whether the capability requires the system to panic or not. Current boot scope capabilities are updated to set the flag, so there should be no functional change as a result of this patch. Signed-off-by:
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Amit Daniel Kachhap authored
These helpers are used only by functions inside cpufeature.c and hence makes sense to be moved from cpufeature.h to cpufeature.c as they are not expected to be used globally. This change helps in reducing the header file size as well as to add future cpu capability types without confusion. Only a cpu capability type macro is sufficient to expose those capabilities globally. Signed-off-by:
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Amit Daniel Kachhap authored
This patch allows __cpu_setup to be invoked with one of these flags, ARM64_CPU_BOOT_PRIMARY, ARM64_CPU_BOOT_SECONDARY or ARM64_CPU_RUNTIME. This is required as some cpufeatures need different handling during different scenarios. The input parameter in x0 is preserved till the end to be used inside this function. There should be no functional change with this patch and is useful for the subsequent ptrauth patch which utilizes it. Some upcoming arm cpufeatures can also utilize these flags. Suggested-by:
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Kristina Martsenko authored
As we're going to enable pointer auth within the kernel and use a different APIAKey for the kernel itself, so move the user APIAKey switch to EL0 exception return. The other 4 keys could remain switched during task switch, but are also moved to keep things consistent. Reviewed-by:
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Kristina Martsenko authored
We currently enable ptrauth for userspace, but do not use it within the kernel. We're going to enable it for the kernel, and will need to manage a separate set of ptrauth keys for the kernel. We currently keep all 5 keys in struct ptrauth_keys. However, as the kernel will only need to use 1 key, it is a bit wasteful to allocate a whole ptrauth_keys struct for every thread. Therefore, a subsequent patch will define a separate struct, with only 1 key, for the kernel. In preparation for that, rename the existing struct (and associated macros and functions) to reflect that they are specific to userspace. Acked-by:
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Kristina Martsenko authored
To enable pointer auth for the kernel, we're going to need to check for the presence of address auth and generic auth using alternative_if. We currently have two cpucaps for each, but alternative_if needs to check a single cpucap. So define meta-capabilities that are present when either of the current two capabilities is present. Leave the existing four cpucaps in place, as they are still needed to check for mismatched systems where one CPU has the architected algorithm but another has the IMP DEF algorithm. Note, the meta-capabilities were present before but were removed in commit a56005d3 ("arm64: cpufeature: Reduce number of pointer auth CPU caps from 6 to 4") and commit 1e013d06 ("arm64: cpufeature: Rework ptr auth hwcaps using multi_entry_cap_matches"), as they were not needed then. Note, unlike before, the current patch checks the cpucap values directly, instead of reading the CPU ID register value. Reviewed-by:
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Amit Daniel Kachhap authored
Some existing/future meta cpucaps match need the presence of individual cpucaps. Currently the individual cpucaps checks it via an array based flag and this introduces dependency on the array entry order. This limitation exists only for system scope cpufeature. This patch introduces an internal helper function (__system_matches_cap) to invoke the matching handler for system scope. This helper has to be used during a narrow window when, - The system wide safe registers are set with all the SMP CPUs and, - The SYSTEM_FEATURE cpu_hwcaps may not have been set. Normal users should use the existing cpus_have_{const_}cap() global function. Suggested-by:
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- 17 Mar, 2020 7 commits
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Andrew Murray authored
At present ARMv8 event counters are limited to 32-bits, though by using the CHAIN event it's possible to combine adjacent counters to achieve 64-bits. The perf config1:0 bit can be set to use such a configuration. With the introduction of ARMv8.5-PMU support, all event counters can now be used as 64-bit counters. Let's enable 64-bit event counters where support exists. Unless the user sets config1:0 we will adjust the counter value such that it overflows upon 32-bit overflow. This follows the same behaviour as the cycle counter which has always been (and remains) 64-bits. Signed-off-by:
Andrew Murray <andrew.murray@arm.com> Reviewed-by:
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Andrew Murray authored
We currently expose the PMU version of the host to the guest via emulation of the DFR0_EL1 and AA64DFR0_EL1 debug feature registers. However many of the features offered beyond PMUv3 for 8.1 are not supported in KVM. Examples of this include support for the PMMIR registers (added in PMUv3 for ARMv8.4) and 64-bit event counters added in (PMUv3 for ARMv8.5). Let's trap the Debug Feature Registers in order to limit PMUVer/PerfMon in the Debug Feature Registers to PMUv3 for ARMv8.1 to avoid unexpected behaviour. Both ID_AA64DFR0.PMUVer and ID_DFR0.PerfMon follow the "Alternative ID scheme used for the Performance Monitors Extension version" where 0xF means an IMPLEMENTATION DEFINED PMU is implemented, and values 0x0-0xE are treated as with an unsigned field (with 0x0 meaning no PMU is present). As we don't expect to expose an IMPLEMENTATION DEFINED PMU, and our cap is below 0xF, we can treat these fields as unsigned when applying the cap. Signed-off-by:
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Andrew Murray authored
When emulating ID registers there is often a need to cap the version bits of a feature such that the guest will not use features that the host is not aware of. For example, when KVM mediates access to the PMU by emulating register accesses. Let's add a helper that extracts a performance monitors ID field and caps the version to a given value. Fields that identify the version of the Performance Monitors Extension do not follow the standard ID scheme, and instead follow the scheme described in ARM DDI 0487E.a page D13-2825 "Alternative ID scheme used for the Performance Monitors Extension version". The value 0xF means an IMPLEMENTATION DEFINED PMU is present, and values 0x0-OxE can be treated the same as an unsigned field with 0x0 meaning no PMU is present. Signed-off-by:
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Robin Murphy authored
Reading this code bordered on painful, what with all the repetition and pointless return values. More fundamentally, dribbling the hardware enables and disables in one bit at a time incurs needless system register overhead for chained events and on reset. We already use bitmask values for the KVM hooks, so consolidate all the register accesses to match, and make a reasonable saving in both source and object code. Signed-off-by:
Robin Murphy <robin.murphy@arm.com> Signed-off-by:
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Takashi Iwai authored
snprintf() is a hard-to-use function, it's especially difficult to use it for concatenating substrings in a buffer with a limited size. Since snprintf() returns the would-be-output size, not the actual size, the subsequent use of snprintf() may point to the incorrect position easily. Although the current code doesn't actually overflow the buffer, it's an incorrect usage. This patch replaces such snprintf() calls with a safer version, scnprintf(). Acked-by:
Takashi Iwai <tiwai@suse.de> Signed-off-by:
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glider@google.com authored
When running the kernel with init_on_alloc=1, calling the default implementation of __alloc_zeroed_user_highpage() from include/linux/highmem.h leads to double-initialization of the allocated page (first by the page allocator, then by clear_user_page(). Calling alloc_page_vma() with __GFP_ZERO, similarly to e.g. x86, seems to be enough to ensure the user page is zeroed only once. Signed-off-by:
Alexander Potapenko <glider@google.com> Signed-off-by:
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Gavin Shan authored
The function __cpu_up() is invoked to bring up the target CPU through the backend, PSCI for example. The nested if statements won't be needed if we bail out early on the following two conditions where the status won't be checked. The code looks simplified in that case. * Error returned from the backend (e.g. PSCI) * The target CPU has been marked as onlined Signed-off-by:
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