diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/admin-guide/perf/arm-cmn.rst | 65 | ||||
| -rw-r--r-- | Documentation/admin-guide/perf/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/arm64/cpu-feature-registers.rst | 2 | ||||
| -rw-r--r-- | Documentation/arm64/elf_hwcaps.rst | 4 | ||||
| -rw-r--r-- | Documentation/arm64/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/arm64/memory-tagging-extension.rst | 305 | ||||
| -rw-r--r-- | Documentation/devicetree/bindings/perf/arm,cmn.yaml | 57 | ||||
| -rw-r--r-- | Documentation/virt/kvm/arm/hyp-abi.rst | 6 |
8 files changed, 438 insertions, 3 deletions
diff --git a/Documentation/admin-guide/perf/arm-cmn.rst b/Documentation/admin-guide/perf/arm-cmn.rst new file mode 100644 index 000000000000..0e4809346014 --- /dev/null +++ b/Documentation/admin-guide/perf/arm-cmn.rst @@ -0,0 +1,65 @@ +============================= +Arm Coherent Mesh Network PMU +============================= + +CMN-600 is a configurable mesh interconnect consisting of a rectangular +grid of crosspoints (XPs), with each crosspoint supporting up to two +device ports to which various AMBA CHI agents are attached. + +CMN implements a distributed PMU design as part of its debug and trace +functionality. This consists of a local monitor (DTM) at every XP, which +counts up to 4 event signals from the connected device nodes and/or the +XP itself. Overflow from these local counters is accumulated in up to 8 +global counters implemented by the main controller (DTC), which provides +overall PMU control and interrupts for global counter overflow. + +PMU events +---------- + +The PMU driver registers a single PMU device for the whole interconnect, +see /sys/bus/event_source/devices/arm_cmn. Multi-chip systems may link +more than one CMN together via external CCIX links - in this situation, +each mesh counts its own events entirely independently, and additional +PMU devices will be named arm_cmn_{1..n}. + +Most events are specified in a format based directly on the TRM +definitions - "type" selects the respective node type, and "eventid" the +event number. Some events require an additional occupancy ID, which is +specified by "occupid". + +* Since RN-D nodes do not have any distinct events from RN-I nodes, they + are treated as the same type (0xa), and the common event templates are + named "rnid_*". + +* The cycle counter is treated as a synthetic event belonging to the DTC + node ("type" == 0x3, "eventid" is ignored). + +* XP events also encode the port and channel in the "eventid" field, to + match the underlying pmu_event0_id encoding for the pmu_event_sel + register. The event templates are named with prefixes to cover all + permutations. + +By default each event provides an aggregate count over all nodes of the +given type. To target a specific node, "bynodeid" must be set to 1 and +"nodeid" to the appropriate value derived from the CMN configuration +(as defined in the "Node ID Mapping" section of the TRM). + +Watchpoints +----------- + +The PMU can also count watchpoint events to monitor specific flit +traffic. Watchpoints are treated as a synthetic event type, and like PMU +events can be global or targeted with a particular XP's "nodeid" value. +Since the watchpoint direction is otherwise implicit in the underlying +register selection, separate events are provided for flit uploads and +downloads. + +The flit match value and mask are passed in config1 and config2 ("val" +and "mask" respectively). "wp_dev_sel", "wp_chn_sel", "wp_grp" and +"wp_exclusive" are specified per the TRM definitions for dtm_wp_config0. +Where a watchpoint needs to match fields from both match groups on the +REQ or SNP channel, it can be specified as two events - one for each +group - with the same nonzero "combine" value. The count for such a +pair of combined events will be attributed to the primary match. +Watchpoint events with a "combine" value of 0 are considered independent +and will count individually. diff --git a/Documentation/admin-guide/perf/index.rst b/Documentation/admin-guide/perf/index.rst index 47c99f40cc16..5a8f2529a033 100644 --- a/Documentation/admin-guide/perf/index.rst +++ b/Documentation/admin-guide/perf/index.rst @@ -12,6 +12,7 @@ Performance monitor support qcom_l2_pmu qcom_l3_pmu arm-ccn + arm-cmn xgene-pmu arm_dsu_pmu thunderx2-pmu diff --git a/Documentation/arm64/cpu-feature-registers.rst b/Documentation/arm64/cpu-feature-registers.rst index f28853f80089..328e0c454fbd 100644 --- a/Documentation/arm64/cpu-feature-registers.rst +++ b/Documentation/arm64/cpu-feature-registers.rst @@ -175,6 +175,8 @@ infrastructure: +------------------------------+---------+---------+ | Name | bits | visible | +------------------------------+---------+---------+ + | MTE | [11-8] | y | + +------------------------------+---------+---------+ | SSBS | [7-4] | y | +------------------------------+---------+---------+ | BT | [3-0] | y | diff --git a/Documentation/arm64/elf_hwcaps.rst b/Documentation/arm64/elf_hwcaps.rst index 84a9fd2d41b4..bbd9cf54db6c 100644 --- a/Documentation/arm64/elf_hwcaps.rst +++ b/Documentation/arm64/elf_hwcaps.rst @@ -240,6 +240,10 @@ HWCAP2_BTI Functionality implied by ID_AA64PFR0_EL1.BT == 0b0001. +HWCAP2_MTE + + Functionality implied by ID_AA64PFR1_EL1.MTE == 0b0010, as described + by Documentation/arm64/memory-tagging-extension.rst. 4. Unused AT_HWCAP bits ----------------------- diff --git a/Documentation/arm64/index.rst b/Documentation/arm64/index.rst index d9665d83c53a..43b0939d384e 100644 --- a/Documentation/arm64/index.rst +++ b/Documentation/arm64/index.rst @@ -14,6 +14,7 @@ ARM64 Architecture hugetlbpage legacy_instructions memory + memory-tagging-extension perf pointer-authentication silicon-errata diff --git a/Documentation/arm64/memory-tagging-extension.rst b/Documentation/arm64/memory-tagging-extension.rst new file mode 100644 index 000000000000..034d37c605e8 --- /dev/null +++ b/Documentation/arm64/memory-tagging-extension.rst @@ -0,0 +1,305 @@ +=============================================== +Memory Tagging Extension (MTE) in AArch64 Linux +=============================================== + +Authors: Vincenzo Frascino <vincenzo.frascino@arm.com> + Catalin Marinas <catalin.marinas@arm.com> + +Date: 2020-02-25 + +This document describes the provision of the Memory Tagging Extension +functionality in AArch64 Linux. + +Introduction +============ + +ARMv8.5 based processors introduce the Memory Tagging Extension (MTE) +feature. MTE is built on top of the ARMv8.0 virtual address tagging TBI +(Top Byte Ignore) feature and allows software to access a 4-bit +allocation tag for each 16-byte granule in the physical address space. +Such memory range must be mapped with the Normal-Tagged memory +attribute. A logical tag is derived from bits 59-56 of the virtual +address used for the memory access. A CPU with MTE enabled will compare +the logical tag against the allocation tag and potentially raise an +exception on mismatch, subject to system registers configuration. + +Userspace Support +================= + +When ``CONFIG_ARM64_MTE`` is selected and Memory Tagging Extension is +supported by the hardware, the kernel advertises the feature to +userspace via ``HWCAP2_MTE``. + +PROT_MTE +-------- + +To access the allocation tags, a user process must enable the Tagged +memory attribute on an address range using a new ``prot`` flag for +``mmap()`` and ``mprotect()``: + +``PROT_MTE`` - Pages allow access to the MTE allocation tags. + +The allocation tag is set to 0 when such pages are first mapped in the +user address space and preserved on copy-on-write. ``MAP_SHARED`` is +supported and the allocation tags can be shared between processes. + +**Note**: ``PROT_MTE`` is only supported on ``MAP_ANONYMOUS`` and +RAM-based file mappings (``tmpfs``, ``memfd``). Passing it to other +types of mapping will result in ``-EINVAL`` returned by these system +calls. + +**Note**: The ``PROT_MTE`` flag (and corresponding memory type) cannot +be cleared by ``mprotect()``. + +**Note**: ``madvise()`` memory ranges with ``MADV_DONTNEED`` and +``MADV_FREE`` may have the allocation tags cleared (set to 0) at any +point after the system call. + +Tag Check Faults +---------------- + +When ``PROT_MTE`` is enabled on an address range and a mismatch between +the logical and allocation tags occurs on access, there are three +configurable behaviours: + +- *Ignore* - This is the default mode. The CPU (and kernel) ignores the + tag check fault. + +- *Synchronous* - The kernel raises a ``SIGSEGV`` synchronously, with + ``.si_code = SEGV_MTESERR`` and ``.si_addr = <fault-address>``. The + memory access is not performed. If ``SIGSEGV`` is ignored or blocked + by the offending thread, the containing process is terminated with a + ``coredump``. + +- *Asynchronous* - The kernel raises a ``SIGSEGV``, in the offending + thread, asynchronously following one or multiple tag check faults, + with ``.si_code = SEGV_MTEAERR`` and ``.si_addr = 0`` (the faulting + address is unknown). + +The user can select the above modes, per thread, using the +``prctl(PR_SET_TAGGED_ADDR_CTRL, flags, 0, 0, 0)`` system call where +``flags`` contain one of the following values in the ``PR_MTE_TCF_MASK`` +bit-field: + +- ``PR_MTE_TCF_NONE`` - *Ignore* tag check faults +- ``PR_MTE_TCF_SYNC`` - *Synchronous* tag check fault mode +- ``PR_MTE_TCF_ASYNC`` - *Asynchronous* tag check fault mode + +The current tag check fault mode can be read using the +``prctl(PR_GET_TAGGED_ADDR_CTRL, 0, 0, 0, 0)`` system call. + +Tag checking can also be disabled for a user thread by setting the +``PSTATE.TCO`` bit with ``MSR TCO, #1``. + +**Note**: Signal handlers are always invoked with ``PSTATE.TCO = 0``, +irrespective of the interrupted context. ``PSTATE.TCO`` is restored on +``sigreturn()``. + +**Note**: There are no *match-all* logical tags available for user +applications. + +**Note**: Kernel accesses to the user address space (e.g. ``read()`` +system call) are not checked if the user thread tag checking mode is +``PR_MTE_TCF_NONE`` or ``PR_MTE_TCF_ASYNC``. If the tag checking mode is +``PR_MTE_TCF_SYNC``, the kernel makes a best effort to check its user +address accesses, however it cannot always guarantee it. + +Excluding Tags in the ``IRG``, ``ADDG`` and ``SUBG`` instructions +----------------------------------------------------------------- + +The architecture allows excluding certain tags to be randomly generated +via the ``GCR_EL1.Exclude`` register bit-field. By default, Linux +excludes all tags other than 0. A user thread can enable specific tags +in the randomly generated set using the ``prctl(PR_SET_TAGGED_ADDR_CTRL, +flags, 0, 0, 0)`` system call where ``flags`` contains the tags bitmap +in the ``PR_MTE_TAG_MASK`` bit-field. + +**Note**: The hardware uses an exclude mask but the ``prctl()`` +interface provides an include mask. An include mask of ``0`` (exclusion +mask ``0xffff``) results in the CPU always generating tag ``0``. + +Initial process state +--------------------- + +On ``execve()``, the new process has the following configuration: + +- ``PR_TAGGED_ADDR_ENABLE`` set to 0 (disabled) +- Tag checking mode set to ``PR_MTE_TCF_NONE`` +- ``PR_MTE_TAG_MASK`` set to 0 (all tags excluded) +- ``PSTATE.TCO`` set to 0 +- ``PROT_MTE`` not set on any of the initial memory maps + +On ``fork()``, the new process inherits the parent's configuration and +memory map attributes with the exception of the ``madvise()`` ranges +with ``MADV_WIPEONFORK`` which will have the data and tags cleared (set +to 0). + +The ``ptrace()`` interface +-------------------------- + +``PTRACE_PEEKMTETAGS`` and ``PTRACE_POKEMTETAGS`` allow a tracer to read +the tags from or set the tags to a tracee's address space. The +``ptrace()`` system call is invoked as ``ptrace(request, pid, addr, +data)`` where: + +- ``request`` - one of ``PTRACE_PEEKMTETAGS`` or ``PTRACE_POKEMTETAGS``. +- ``pid`` - the tracee's PID. +- ``addr`` - address in the tracee's address space. +- ``data`` - pointer to a ``struct iovec`` where ``iov_base`` points to + a buffer of ``iov_len`` length in the tracer's address space. + +The tags in the tracer's ``iov_base`` buffer are represented as one +4-bit tag per byte and correspond to a 16-byte MTE tag granule in the +tracee's address space. + +**Note**: If ``addr`` is not aligned to a 16-byte granule, the kernel +will use the corresponding aligned address. + +``ptrace()`` return value: + +- 0 - tags were copied, the tracer's ``iov_len`` was updated to the + number of tags transferred. This may be smaller than the requested + ``iov_len`` if the requested address range in the tracee's or the + tracer's space cannot be accessed or does not have valid tags. +- ``-EPERM`` - the specified process cannot be traced. +- ``-EIO`` - the tracee's address range cannot be accessed (e.g. invalid + address) and no tags copied. ``iov_len`` not updated. +- ``-EFAULT`` - fault on accessing the tracer's memory (``struct iovec`` + or ``iov_base`` buffer) and no tags copied. ``iov_len`` not updated. +- ``-EOPNOTSUPP`` - the tracee's address does not have valid tags (never + mapped with the ``PROT_MTE`` flag). ``iov_len`` not updated. + +**Note**: There are no transient errors for the requests above, so user +programs should not retry in case of a non-zero system call return. + +``PTRACE_GETREGSET`` and ``PTRACE_SETREGSET`` with ``addr == +``NT_ARM_TAGGED_ADDR_CTRL`` allow ``ptrace()`` access to the tagged +address ABI control and MTE configuration of a process as per the +``prctl()`` options described in +Documentation/arm64/tagged-address-abi.rst and above. The corresponding +``regset`` is 1 element of 8 bytes (``sizeof(long))``). + +Example of correct usage +======================== + +*MTE Example code* + +.. code-block:: c + + /* + * To be compiled with -march=armv8.5-a+memtag + */ + #include <errno.h> + #include <stdint.h> + #include <stdio.h> + #include <stdlib.h> + #include <unistd.h> + #include <sys/auxv.h> + #include <sys/mman.h> + #include <sys/prctl.h> + + /* + * From arch/arm64/include/uapi/asm/hwcap.h + */ + #define HWCAP2_MTE (1 << 18) + + /* + * From arch/arm64/include/uapi/asm/mman.h + */ + #define PROT_MTE 0x20 + + /* + * From include/uapi/linux/prctl.h + */ + #define PR_SET_TAGGED_ADDR_CTRL 55 + #define PR_GET_TAGGED_ADDR_CTRL 56 + # define PR_TAGGED_ADDR_ENABLE (1UL << 0) + # define PR_MTE_TCF_SHIFT 1 + # define PR_MTE_TCF_NONE (0UL << PR_MTE_TCF_SHIFT) + # define PR_MTE_TCF_SYNC (1UL << PR_MTE_TCF_SHIFT) + # define PR_MTE_TCF_ASYNC (2UL << PR_MTE_TCF_SHIFT) + # define PR_MTE_TCF_MASK (3UL << PR_MTE_TCF_SHIFT) + # define PR_MTE_TAG_SHIFT 3 + # define PR_MTE_TAG_MASK (0xffffUL << PR_MTE_TAG_SHIFT) + + /* + * Insert a random logical tag into the given pointer. + */ + #define insert_random_tag(ptr) ({ \ + uint64_t __val; \ + asm("irg %0, %1" : "=r" (__val) : "r" (ptr)); \ + __val; \ + }) + + /* + * Set the allocation tag on the destination address. + */ + #define set_tag(tagged_addr) do { \ + asm volatile("stg %0, [%0]" : : "r" (tagged_addr) : "memory"); \ + } while (0) + + int main() + { + unsigned char *a; + unsigned long page_sz = sysconf(_SC_PAGESIZE); + unsigned long hwcap2 = getauxval(AT_HWCAP2); + + /* check if MTE is present */ + if (!(hwcap2 & HWCAP2_MTE)) + return EXIT_FAILURE; + + /* + * Enable the tagged address ABI, synchronous MTE tag check faults and + * allow all non-zero tags in the randomly generated set. + */ + if (prctl(PR_SET_TAGGED_ADDR_CTRL, + PR_TAGGED_ADDR_ENABLE | PR_MTE_TCF_SYNC | (0xfffe << PR_MTE_TAG_SHIFT), + 0, 0, 0)) { + perror("prctl() failed"); + return EXIT_FAILURE; + } + + a = mmap(0, page_sz, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); + if (a == MAP_FAILED) { + perror("mmap() failed"); + return EXIT_FAILURE; + } + + /* + * Enable MTE on the above anonymous mmap. The flag could be passed + * directly to mmap() and skip this step. + */ + if (mprotect(a, page_sz, PROT_READ | PROT_WRITE | PROT_MTE)) { + perror("mprotect() failed"); + return EXIT_FAILURE; + } + + /* access with the default tag (0) */ + a[0] = 1; + a[1] = 2; + + printf("a[0] = %hhu a[1] = %hhu\n", a[0], a[1]); + + /* set the logical and allocation tags */ + a = (unsigned char *)insert_random_tag(a); + set_tag(a); + + printf("%p\n", a); + + /* non-zero tag access */ + a[0] = 3; + printf("a[0] = %hhu a[1] = %hhu\n", a[0], a[1]); + + /* + * If MTE is enabled correctly the next instruction will generate an + * exception. + */ + printf("Expecting SIGSEGV...\n"); + a[16] = 0xdd; + + /* this should not be printed in the PR_MTE_TCF_SYNC mode */ + printf("...haven't got one\n"); + + return EXIT_FAILURE; + } diff --git a/Documentation/devicetree/bindings/perf/arm,cmn.yaml b/Documentation/devicetree/bindings/perf/arm,cmn.yaml new file mode 100644 index 000000000000..e4fcc0de25e2 --- /dev/null +++ b/Documentation/devicetree/bindings/perf/arm,cmn.yaml @@ -0,0 +1,57 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +# Copyright 2020 Arm Ltd. +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/perf/arm,cmn.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Arm CMN (Coherent Mesh Network) Performance Monitors + +maintainers: + - Robin Murphy <robin.murphy@arm.com> + +properties: + compatible: + const: arm,cmn-600 + + reg: + items: + - description: Physical address of the base (PERIPHBASE) and + size (up to 64MB) of the configuration address space. + + interrupts: + minItems: 1 + maxItems: 4 + items: + - description: Overflow interrupt for DTC0 + - description: Overflow interrupt for DTC1 + - description: Overflow interrupt for DTC2 + - description: Overflow interrupt for DTC3 + description: One interrupt for each DTC domain implemented must + be specified, in order. DTC0 is always present. + + arm,root-node: + $ref: /schemas/types.yaml#/definitions/uint32 + description: Offset from PERIPHBASE of the configuration + discovery node (see TRM definition of ROOTNODEBASE). + +required: + - compatible + - reg + - interrupts + - arm,root-node + +additionalProperties: false + +examples: + - | + #include <dt-bindings/interrupt-controller/arm-gic.h> + #include <dt-bindings/interrupt-controller/irq.h> + pmu@50000000 { + compatible = "arm,cmn-600"; + reg = <0x50000000 0x4000000>; + /* 4x2 mesh with one DTC, and CFG node at 0,1,1,0 */ + interrupts = <GIC_SPI 46 IRQ_TYPE_LEVEL_HIGH>; + arm,root-node = <0x104000>; + }; +... diff --git a/Documentation/virt/kvm/arm/hyp-abi.rst b/Documentation/virt/kvm/arm/hyp-abi.rst index d9eba93aa364..83cadd8186fa 100644 --- a/Documentation/virt/kvm/arm/hyp-abi.rst +++ b/Documentation/virt/kvm/arm/hyp-abi.rst @@ -54,9 +54,9 @@ these functions (see arch/arm{,64}/include/asm/virt.h): x3 = x1's value when entering the next payload (arm64) x4 = x2's value when entering the next payload (arm64) - Mask all exceptions, disable the MMU, move the arguments into place - (arm64 only), and jump to the restart address while at HYP/EL2. This - hypercall is not expected to return to its caller. + Mask all exceptions, disable the MMU, clear I+D bits, move the arguments + into place (arm64 only), and jump to the restart address while at HYP/EL2. + This hypercall is not expected to return to its caller. Any other value of r0/x0 triggers a hypervisor-specific handling, which is not documented here. |