linux-next.git/Documentation/userspace-api, branch master

Merge branch 'next' of https://git.kernel.org/pub/scm/linux/kernel/git/mic/linux.git

2026-08-20T12:58:57+00:00

Merge branch 'char-misc-next' of https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git

2026-08-20T12:57:31+00:00

Merge branch 'mm-unstable' of https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-08-20T12:20:13+00:00

Merge branch 'mm-stable' of https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2026-08-20T12:20:09+00:00

# Conflicts: # arch/riscv/Kconfig

alloc_tag: add ioctl to /proc/allocinfo

2026-08-20T03:15:58+00:00

Patch series "alloc_tag: introduce IOCTL-based filtering for MAP", v8. Currently, memory allocation profiling data is primarily exposed through /proc/allocinfo. While useful for manual inspection, this text-based interface poses challenges for production monitoring and large-scale analysis: 1. Userspace must parse large amounts of text to extract specific fields. 2. To find specific tags, userspace must read the entire dataset, requiring many context switches and high data copying. 3. The kernel currently aggregates per-CPU counters for every allocation size, even those the user intends to filter out immediately. This series introduces a new IOCTL-based binary interface for allocinfo that supports kernel-side filtering. By allowing the user to specify a filter mask, we significantly reduce the work performed in-kernel and the amount of data transferred to userspace. The IOCTL mechanism was chosen for allocinfo to address the per-CPU counter aggregation bottleneck. A traditional read() operation must report the total allocation count and sizes for every code tag in the system. Doing so requires iterating across all CPUs to sum their per-CPU counters for thousands of tags, which introduces substantial runtime overhead. The IOCTL interface allows userspace to push selective filtering criteria directly into the kernel before the per-CPU counter aggregation. The kernel aggregates per-CPU counters only for a small subset of tags that match the filter. This results in significant performance improvement. Beyond fast filtered retrieval, the IOCTL foundation allows introducing a context capture mechanism in the future to capture the context for specific allocations. Performance measurements were conducted on an Intel Xeon Platinum 8481C (224 CPUs) with caches dropped before each run. The IOCTL mechanism shows a ~20x performance improvement for filtered queries. The kernel avoids the expensive per-CPU counter aggregation (alloc_tag_read) for any tags that fail the initial string or location filters. Scenario 1: Specific File Filtering (arch/x86/events/rapl.c) 1. Traditional (cat /proc/allocinfo | grep): 22ms (sys) 2. IOCTL Interface: 1ms (sys) Scenario 2: Compound Filtering (Filename + Size) 1. Traditional: (cat ... | grep | awk): 21ms (sys) 2. IOCTL Interface: 1ms (sys) Scenario 3: Size-Based Filtering (min_size = 1MB) 1. Traditional: (cat ... | awk): 21ms (sys) 2. IOCTL Interface: 14ms (sys) This patch (of 6): Add the following ioctl commands for /proc/allocinfo file: ALLOCINFO_IOC_CONTENT_ID - gets content identifier which can be used to check whether the file content has changed specifically due to module load/unload. Every time a module is loaded / unloaded, the returned value will be different. By comparing the identifier value at the beginning and at the end of the content retrieval operation, users can validate retrieved information for consistency. ALLOCINFO_IOC_GET_AT - gets the record at the specified position. This is the position of a record in /proc/allocinfo. ALLOCINFO_IOC_GET_NEXT - gets the record next to the last retrieved one. If no records were previously retrieved, returns the first record. Note, function file and module names often have the same prefixes, therefore when filtering for them, we compare the last 64 characters to minimize the chances of name collisions. [akpm@linux-foundation.org: include compat.h, per Suren] Closes: https://lore.kernel.org/oe-kbuild-all/202607091820.qbjlGhKK-lkp@intel.com/ Link: https://lore.kernel.org/cover.1783532853.git.abhishekbapat@google.com Link: https://lore.kernel.org/15596de2607ef13e7c77c6d74763f4ae992ec475.1783532853.git.abhishekbapat@google.com Signed-off-by: Suren Baghdasaryan Signed-off-by: Abhishek Bapat Acked-by: Hao Ge Cc: Jonathan Corbet Cc: Kent Overstreet Cc: Sourav Panda Signed-off-by: Andrew Morton

landlock: Document tracepoints

2026-08-17T08:17:19+00:00

Until now, Landlock observability documentation covered only audit records. The tracepoints added by the previous commits introduce a second channel with different semantics (firing regardless of audit configuration and domain log flags, exposing the full ruleset and domain state to eBPF via BTF), which kernel developers, administrators, and userspace tool authors need to discover and compare against audit. Add a dedicated "Landlock Trace Events" reference covering the event categories, enabling events via tracefs, ruleset versioning, eBPF access through BPF_RAW_TRACEPOINT, and the same_exec and logged denial fields (logged being the kernel's audit-logging decision, so a stateless ftrace filter can select the denials audit would record with logged==1). Cross-reference it from the administrator, kernel-internals, and userspace API documents, contrasting tracepoints with audit: when each channel is preferred, what each guarantees, and how NOAUDIT hooks and audit rate limiting affect them. Also document the relational other-party domain fields the scope and ptrace denial tracepoints expose (tracee_domain, target_domain, peer_domain; 0 when the other party is unsandboxed), so a consumer can resolve them against the lifecycle events and reproduce the two-domain verdict. Cc: Günther Noack Cc: Tingmao Wang Link: https://patch.msgid.link/20260811094338.288094-20-mic@digikod.net [mic: Update dates] Signed-off-by: Mickaël Salaün

landlock: Document LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS

2026-08-15T07:14:47+00:00

Document setting no_new_privs with ruleset enforcement, following the same compatibility section style as previous ABI additions. Include a section explaining the tradeoffs of setting no_new_privs through any means for privileged users of Landlock. Signed-off-by: Justin Suess Link: https://patch.msgid.link/20260809154544.1253100-5-utilityemal77@gmail.com Signed-off-by: Mickaël Salaün

landlock: Link the erratum documentation for whiteout objects

2026-08-15T07:14:45+00:00

The documentation embeds the canonical erratum documentation from the header file, which is already a self-contained description of the issue. Signed-off-by: Günther Noack Link: https://patch.msgid.link/20260813093157.1436894-7-gnoack@google.com [mic: Update the documentation date] Signed-off-by: Mickaël Salaün

mm/mseal: fix mseal documentation for 32-bit kernels

2026-08-07T01:57:12+00:00

mseal.o is built only for 64-bit kernels, so 32-bit kernels fall back to sys_ni_syscall() and return -ENOSYS rather than -EPERM. Drop architecture description in mseal.rst, since the arch feature doc has the latest state of mseal for each architecture. Fix the CONFIG_MSEAL_SYSTEM_MAPPINGS typo in init/Kconfig. Link: https://lore.kernel.org/20260715131258.55499-1-leon.hwang@linux.dev Signed-off-by: Leon Hwang Acked-by: Lance Yang Cc: Alice Ryhl Cc: Anand Moon Cc: Doug Anderson Cc: Gary Guo Cc: Jann Horn Cc: Jonathan Corbet Cc: Leon Hwang Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Miguel Ojeda Cc: Nathan Chancellor Cc: Pedro Falcato Cc: Peter Zijlstra Cc: Randy Dunlap Cc: Thomas Weißschuh Cc: Vlastimil Babka Signed-off-by: Andrew Morton

docs: ntsync: align ioctl names and struct layouts with uapi

2026-07-31T12:15:54+00:00

The uAPI documentation used outdated or conceptual ioctl macro names and listed ntsync_event_args / ntsync_wait_args fields in the wrong order. Match include/uapi/linux/ntsync.h and note that absolute MONOTONIC timeouts are interpreted in the caller's time namespace. Signed-off-by: Iván Ezequiel Rodriguez Reviewed-by: Elizabeth Figura Signed-off-by: Elizabeth Figura Link: https://patch.msgid.link/20260723201301.11826-5-zfigura@codeweavers.com Signed-off-by: Greg Kroah-Hartman