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The metric table needs to be delivered to userspace as a single atomic snapshot, but the current sysfs metrics_bin path is a file read: userspace can read it in chunks and observe a torn snapshot if an SMU refresh happens between read() calls. The same path is also bounded by PAGE_SIZE, so the ~13 KB table used by HSMP protocol version 7 on Family 1Ah Model 50h-5Fh cannot be returned at all, regardless of how userspace reads it. Rather than extend sysfs to lift both restrictions, expose the metric table through the existing HSMP character device using a new ioctl that always copies the table in one shot. Add struct hsmp_telemetry_data and HSMP_IOCTL_GET_TELEMETRY_DATA to the UAPI header. Under the surrounding #pragma pack(4), placing the __u64 user pointer first gives a tight 16-byte layout that is identical for 32- and 64-bit callers, and the trailing __u16 reserved field is rejected with -EINVAL if non-zero so future kernels can repurpose it without breaking already-deployed userspace. The command is encoded with _IOW because the kernel only reads the request struct; the snapshot travels through the user pointer it carries. The requested size may be anything from one byte up to the size firmware reported for that socket's table. A short request returns the leading bytes of the snapshot, so userspace built against an older table layout keeps working on firmware that grew the table, mirroring the relaxed response_sz rule applied to HSMP messages earlier in this series. A request larger than the firmware table is rejected with -EINVAL rather than short-written, so a caller can never mistake a partial copy for a full one. Dispatch hsmp_ioctl() on the ioctl command: the existing message handler is factored out as hsmp_ioctl_msg() for HSMP_IOCTL_CMD, and HSMP_IOCTL_GET_TELEMETRY_DATA goes to a new hsmp_ioctl_get_telemetry() helper. /dev/hsmp is a singleton character device that outlives an individual socket unbind, so an ioctl issued on an already-open fd can run concurrently with socket teardown. hsmp_sock_rwsem is the driver's contract for that: the data plane takes it for read, and probe and remove take it for write to drain the data plane before freeing the socket array, unmapping the metric tables and destroying the per-socket mutexes. hsmp_ioctl_get_telemetry() takes it for read across the socket lookup, the checks on that socket's metric-table state and the table read itself, so none of that state can be torn down underneath it. Without this the handler would sleep in its kvmalloc() holding no lock at all, and could resume with a freed socket, locking a destroyed mutex and reading from an unmapped iomem region. The lock is dropped before the copy_to_user(), because faulting in the destination can block indefinitely on a userfaultfd-backed buffer and would otherwise leave a socket unbind waiting for the write lock. Since hsmp_metric_tbl_read() reached the mailbox through hsmp_send_message(), which takes hsmp_sock_rwsem itself, calling it with the lock already held would recursively take the read side and can deadlock against a queued writer. Split out hsmp_metric_tbl_read_locked(), which asserts the lock and uses hsmp_send_message_locked(), and leave hsmp_metric_tbl_read() as a wrapper that takes the read lock for the sysfs callers. This also brings the whole fill-and-copy under the rwsem for those callers, where the memcpy_fromio() previously ran outside it, and makes the lock order uniformly hsmp_sock_rwsem -> metric_read_lock -> hsmp_sem. The user-controlled socket index in HSMP_IOCTL_GET_TELEMETRY_DATA is clamped with array_index_nospec() before indexing hsmp_pdev.sock[], mitigating Spectre v1 (CVE-2017-5753). Include linux/nospec.h, which the file relied on getting transitively. Co-developed-by: Muthusamy Ramalingam <muthusamy.ramalingam@amd.com> Signed-off-by: Muthusamy Ramalingam <muthusamy.ramalingam@amd.com> Signed-off-by: Muralidhara M K <muralidhara.mk@amd.com> Link: https://patch.msgid.link/20260727141542.3370108-5-muralidhara.mk@amd.com Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> |
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Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. Quick Start ----------- * Report a bug: See Documentation/admin-guide/reporting-issues.rst * Get the latest kernel: https://kernel.org * Build the kernel: See Documentation/admin-guide/quickly-build-trimmed-linux.rst * Join the community: https://lore.kernel.org/ Essential Documentation ----------------------- All users should be familiar with: * Building requirements: Documentation/process/changes.rst * Code of Conduct: Documentation/process/code-of-conduct.rst * License: See COPYING Documentation can be built with make htmldocs or viewed online at: https://www.kernel.org/doc/html/latest/ Who Are You? ============ Find your role below: * New Kernel Developer - Getting started with kernel development * Academic Researcher - Studying kernel internals and architecture * Security Expert - Hardening and vulnerability analysis * Backport/Maintenance Engineer - Maintaining stable kernels * System Administrator - Configuring and troubleshooting * Maintainer - Leading subsystems and reviewing patches * Hardware Vendor - Writing drivers for new hardware * Distribution Maintainer - Packaging kernels for distros * AI Coding Assistant - LLMs and AI-powered development tools For Specific Users ================== New Kernel Developer -------------------- Welcome! Start your kernel development journey here: * Getting Started: Documentation/process/development-process.rst * Your First Patch: Documentation/process/submitting-patches.rst * Coding Style: Documentation/process/coding-style.rst * Build System: Documentation/kbuild/index.rst * Development Tools: Documentation/dev-tools/index.rst * Kernel Hacking Guide: Documentation/kernel-hacking/hacking.rst * Core APIs: Documentation/core-api/index.rst Academic Researcher ------------------- Explore the kernel's architecture and internals: * Researcher Guidelines: Documentation/process/researcher-guidelines.rst * Memory Management: Documentation/mm/index.rst * Scheduler: Documentation/scheduler/index.rst * Networking Stack: Documentation/networking/index.rst * Filesystems: Documentation/filesystems/index.rst * RCU (Read-Copy Update): Documentation/RCU/index.rst * Locking Primitives: Documentation/locking/index.rst * Power Management: Documentation/power/index.rst Security Expert --------------- Security documentation and hardening guides: * Security Documentation: Documentation/security/index.rst * LSM Development: Documentation/security/lsm-development.rst * Self Protection: Documentation/security/self-protection.rst * Reporting Vulnerabilities: Documentation/process/security-bugs.rst * CVE Procedures: Documentation/process/cve.rst * Embargoed Hardware Issues: Documentation/process/embargoed-hardware-issues.rst * Security Features: Documentation/userspace-api/seccomp_filter.rst Backport/Maintenance Engineer ----------------------------- Maintain and stabilize kernel versions: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * Backporting Guide: Documentation/process/backporting.rst * Applying Patches: Documentation/process/applying-patches.rst * Subsystem Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git for Maintainers: Documentation/maintainer/configure-git.rst System Administrator -------------------- Configure, tune, and troubleshoot Linux systems: * Admin Guide: Documentation/admin-guide/index.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Sysctl Tuning: Documentation/admin-guide/sysctl/index.rst * Tracing/Debugging: Documentation/trace/index.rst * Performance Security: Documentation/admin-guide/perf-security.rst * Hardware Monitoring: Documentation/hwmon/index.rst Maintainer ---------- Lead kernel subsystems and manage contributions: * Maintainer Handbook: Documentation/maintainer/index.rst * Pull Requests: Documentation/maintainer/pull-requests.rst * Managing Patches: Documentation/maintainer/modifying-patches.rst * Rebasing and Merging: Documentation/maintainer/rebasing-and-merging.rst * Development Process: Documentation/process/maintainer-handbooks.rst * Maintainer Entry Profile: Documentation/maintainer/maintainer-entry-profile.rst * Git Configuration: Documentation/maintainer/configure-git.rst Hardware Vendor --------------- Write drivers and support new hardware: * Driver API Guide: Documentation/driver-api/index.rst * Driver Model: Documentation/driver-api/driver-model/driver.rst * Device Drivers: Documentation/driver-api/infrastructure.rst * Bus Types: Documentation/driver-api/driver-model/bus.rst * Device Tree Bindings: Documentation/devicetree/bindings/ * Power Management: Documentation/driver-api/pm/index.rst * DMA API: Documentation/core-api/dma-api.rst Distribution Maintainer ----------------------- Package and distribute the kernel: * Stable Kernel Rules: Documentation/process/stable-kernel-rules.rst * ABI Documentation: Documentation/ABI/README * Kernel Configuration: Documentation/kbuild/kconfig.rst * Module Signing: Documentation/admin-guide/module-signing.rst * Kernel Parameters: Documentation/admin-guide/kernel-parameters.rst * Tainted Kernels: Documentation/admin-guide/tainted-kernels.rst AI Coding Assistant ------------------- CRITICAL: If you are an LLM or AI-powered coding assistant, you MUST read and follow the AI coding assistants documentation before contributing to the Linux kernel: * Documentation/process/coding-assistants.rst This documentation contains essential requirements about licensing, attribution, and the Developer Certificate of Origin that all AI tools must comply with. Communication and Support ========================= * Mailing Lists: https://lore.kernel.org/ * IRC: #kernelnewbies on irc.oftc.net * Bugzilla: https://bugzilla.kernel.org/ * MAINTAINERS file: Lists subsystem maintainers and mailing lists * Email Clients: Documentation/process/email-clients.rst