From 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 21 Feb 2023 18:24:12 -0800 Subject: Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next Pull networking updates from Jakub Kicinski: "Core: - Add dedicated kmem_cache for typical/small skb->head, avoid having to access struct page at kfree time, and improve memory use. - Introduce sysctl to set default RPS configuration for new netdevs. - Define Netlink protocol specification format which can be used to describe messages used by each family and auto-generate parsers. Add tools for generating kernel data structures and uAPI headers. - Expose all net/core sysctls inside netns. - Remove 4s sleep in netpoll if carrier is instantly detected on boot. - Add configurable limit of MDB entries per port, and port-vlan. - Continue populating drop reasons throughout the stack. - Retire a handful of legacy Qdiscs and classifiers. Protocols: - Support IPv4 big TCP (TSO frames larger than 64kB). - Add IP_LOCAL_PORT_RANGE socket option, to control local port range on socket by socket basis. - Track and report in procfs number of MPTCP sockets used. - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path manager. - IPv6: don't check net.ipv6.route.max_size and rely on garbage collection to free memory (similarly to IPv4). - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986). - ICMP: add per-rate limit counters. - Add support for user scanning requests in ieee802154. - Remove static WEP support. - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate reporting. - WiFi 7 EHT channel puncturing support (client & AP). BPF: - Add a rbtree data structure following the "next-gen data structure" precedent set by recently added linked list, that is, by using kfunc + kptr instead of adding a new BPF map type. - Expose XDP hints via kfuncs with initial support for RX hash and timestamp metadata. - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to better support decap on GRE tunnel devices not operating in collect metadata. - Improve x86 JIT's codegen for PROBE_MEM runtime error checks. - Remove the need for trace_printk_lock for bpf_trace_printk and bpf_trace_vprintk helpers. - Extend libbpf's bpf_tracing.h support for tracing arguments of kprobes/uprobes and syscall as a special case. - Significantly reduce the search time for module symbols by livepatch and BPF. - Enable cpumasks to be used as kptrs, which is useful for tracing programs tracking which tasks end up running on which CPUs in different time intervals. - Add support for BPF trampoline on s390x and riscv64. - Add capability to export the XDP features supported by the NIC. - Add __bpf_kfunc tag for marking kernel functions as kfuncs. - Add cgroup.memory=nobpf kernel parameter option to disable BPF memory accounting for container environments. Netfilter: - Remove the CLUSTERIP target. It has been marked as obsolete for years, and we still have WARN splats wrt races of the out-of-band /proc interface installed by this target. - Add 'destroy' commands to nf_tables. They are identical to the existing 'delete' commands, but do not return an error if the referenced object (set, chain, rule...) did not exist. Driver API: - Improve cpumask_local_spread() locality to help NICs set the right IRQ affinity on AMD platforms. - Separate C22 and C45 MDIO bus transactions more clearly. - Introduce new DCB table to control DSCP rewrite on egress. - Support configuration of Physical Layer Collision Avoidance (PLCA) Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of shared medium Ethernet. - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing preemption of low priority frames by high priority frames. - Add support for controlling MACSec offload using netlink SET. - Rework devlink instance refcounts to allow registration and de-registration under the instance lock. Split the code into multiple files, drop some of the unnecessarily granular locks and factor out common parts of netlink operation handling. - Add TX frame aggregation parameters (for USB drivers). - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning messages with notifications for debug. - Allow offloading of UDP NEW connections via act_ct. - Add support for per action HW stats in TC. - Support hardware miss to TC action (continue processing in SW from a specific point in the action chain). - Warn if old Wireless Extension user space interface is used with modern cfg80211/mac80211 drivers. Do not support Wireless Extensions for Wi-Fi 7 devices at all. Everyone should switch to using nl80211 interface instead. - Improve the CAN bit timing configuration. Use extack to return error messages directly to user space, update the SJW handling, including the definition of a new default value that will benefit CAN-FD controllers, by increasing their oscillator tolerance. New hardware / drivers: - Ethernet: - nVidia BlueField-3 support (control traffic driver) - Ethernet support for imx93 SoCs - Motorcomm yt8531 gigabit Ethernet PHY - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA) - Microchip LAN8841 PHY (incl. cable diagnostics and PTP) - Amlogic gxl MDIO mux - WiFi: - RealTek RTL8188EU (rtl8xxxu) - Qualcomm Wi-Fi 7 devices (ath12k) - CAN: - Renesas R-Car V4H Drivers: - Bluetooth: - Set Per Platform Antenna Gain (PPAG) for Intel controllers. - Ethernet NICs: - Intel (1G, igc): - support TSN / Qbv / packet scheduling features of i226 model - Intel (100G, ice): - use GNSS subsystem instead of TTY - multi-buffer XDP support - extend support for GPIO pins to E823 devices - nVidia/Mellanox: - update the shared buffer configuration on PFC commands - implement PTP adjphase function for HW offset control - TC support for Geneve and GRE with VF tunnel offload - more efficient crypto key management method - multi-port eswitch support - Netronome/Corigine: - add DCB IEEE support - support IPsec offloading for NFP3800 - Freescale/NXP (enetc): - support XDP_REDIRECT for XDP non-linear buffers - improve reconfig, avoid link flap and waiting for idle - support MAC Merge layer - Other NICs: - sfc/ef100: add basic devlink support for ef100 - ionic: rx_push mode operation (writing descriptors via MMIO) - bnxt: use the auxiliary bus abstraction for RDMA - r8169: disable ASPM and reset bus in case of tx timeout - cpsw: support QSGMII mode for J721e CPSW9G - cpts: support pulse-per-second output - ngbe: add an mdio bus driver - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing - r8152: handle devices with FW with NCM support - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation - virtio-net: support multi buffer XDP - virtio/vsock: replace virtio_vsock_pkt with sk_buff - tsnep: XDP support - Ethernet high-speed switches: - nVidia/Mellanox (mlxsw): - add support for latency TLV (in FW control messages) - Microchip (sparx5): - separate explicit and implicit traffic forwarding rules, make the implicit rules always active - add support for egress DSCP rewrite - IS0 VCAP support (Ingress Classification) - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS etc.) - ES2 VCAP support (Egress Access Control) - support for Per-Stream Filtering and Policing (802.1Q, 8.6.5.1) - Ethernet embedded switches: - Marvell (mv88e6xxx): - add MAB (port auth) offload support - enable PTP receive for mv88e6390 - NXP (ocelot): - support MAC Merge layer - support for the the vsc7512 internal copper phys - Microchip: - lan9303: convert to PHYLINK - lan966x: support TC flower filter statistics - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x - lan937x: support Credit Based Shaper configuration - ksz9477: support Energy Efficient Ethernet - other: - qca8k: convert to regmap read/write API, use bulk operations - rswitch: Improve TX timestamp accuracy - Intel WiFi (iwlwifi): - EHT (Wi-Fi 7) rate reporting - STEP equalizer support: transfer some STEP (connection to radio on platforms with integrated wifi) related parameters from the BIOS to the firmware. - Qualcomm 802.11ax WiFi (ath11k): - IPQ5018 support - Fine Timing Measurement (FTM) responder role support - channel 177 support - MediaTek WiFi (mt76): - per-PHY LED support - mt7996: EHT (Wi-Fi 7) support - Wireless Ethernet Dispatch (WED) reset support - switch to using page pool allocator - RealTek WiFi (rtw89): - support new version of Bluetooth co-existance - Mobile: - rmnet: support TX aggregation" * tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits) page_pool: add a comment explaining the fragment counter usage net: ethtool: fix __ethtool_dev_mm_supported() implementation ethtool: pse-pd: Fix double word in comments xsk: add linux/vmalloc.h to xsk.c sefltests: netdevsim: wait for devlink instance after netns removal selftest: fib_tests: Always cleanup before exit net/mlx5e: Align IPsec ASO result memory to be as required by hardware net/mlx5e: TC, Set CT miss to the specific ct action instance net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG net/mlx5: Refactor tc miss handling to a single function net/mlx5: Kconfig: Make tc offload depend on tc skb extension net/sched: flower: Support hardware miss to tc action net/sched: flower: Move filter handle initialization earlier net/sched: cls_api: Support hardware miss to tc action net/sched: Rename user cookie and act cookie sfc: fix builds without CONFIG_RTC_LIB sfc: clean up some inconsistent indentings net/mlx4_en: Introduce flexible array to silence overflow warning net: lan966x: Fix possible deadlock inside PTP net/ulp: Remove redundant ->clone() test in inet_clone_ulp(). ... --- Documentation/mm/vmalloced-kernel-stacks.rst | 153 +++++++++++++++++++++++++++ 1 file changed, 153 insertions(+) create mode 100644 Documentation/mm/vmalloced-kernel-stacks.rst (limited to 'Documentation/mm/vmalloced-kernel-stacks.rst') diff --git a/Documentation/mm/vmalloced-kernel-stacks.rst b/Documentation/mm/vmalloced-kernel-stacks.rst new file mode 100644 index 000000000..fc8c67833 --- /dev/null +++ b/Documentation/mm/vmalloced-kernel-stacks.rst @@ -0,0 +1,153 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================================== +Virtually Mapped Kernel Stack Support +===================================== + +:Author: Shuah Khan + +.. contents:: :local: + +Overview +-------- + +This is a compilation of information from the code and original patch +series that introduced the `Virtually Mapped Kernel Stacks feature +` + +Introduction +------------ + +Kernel stack overflows are often hard to debug and make the kernel +susceptible to exploits. Problems could show up at a later time making +it difficult to isolate and root-cause. + +Virtually-mapped kernel stacks with guard pages causes kernel stack +overflows to be caught immediately rather than causing difficult to +diagnose corruptions. + +HAVE_ARCH_VMAP_STACK and VMAP_STACK configuration options enable +support for virtually mapped stacks with guard pages. This feature +causes reliable faults when the stack overflows. The usability of +the stack trace after overflow and response to the overflow itself +is architecture dependent. + +.. note:: + As of this writing, arm64, powerpc, riscv, s390, um, and x86 have + support for VMAP_STACK. + +HAVE_ARCH_VMAP_STACK +-------------------- + +Architectures that can support Virtually Mapped Kernel Stacks should +enable this bool configuration option. The requirements are: + +- vmalloc space must be large enough to hold many kernel stacks. This + may rule out many 32-bit architectures. +- Stacks in vmalloc space need to work reliably. For example, if + vmap page tables are created on demand, either this mechanism + needs to work while the stack points to a virtual address with + unpopulated page tables or arch code (switch_to() and switch_mm(), + most likely) needs to ensure that the stack's page table entries + are populated before running on a possibly unpopulated stack. +- If the stack overflows into a guard page, something reasonable + should happen. The definition of "reasonable" is flexible, but + instantly rebooting without logging anything would be unfriendly. + +VMAP_STACK +---------- + +VMAP_STACK bool configuration option when enabled allocates virtually +mapped task stacks. This option depends on HAVE_ARCH_VMAP_STACK. + +- Enable this if you want the use virtually-mapped kernel stacks + with guard pages. This causes kernel stack overflows to be caught + immediately rather than causing difficult-to-diagnose corruption. + +.. note:: + + Using this feature with KASAN requires architecture support + for backing virtual mappings with real shadow memory, and + KASAN_VMALLOC must be enabled. + +.. note:: + + VMAP_STACK is enabled, it is not possible to run DMA on stack + allocated data. + +Kernel configuration options and dependencies keep changing. Refer to +the latest code base: + +`Kconfig ` + +Allocation +----------- + +When a new kernel thread is created, thread stack is allocated from +virtually contiguous memory pages from the page level allocator. These +pages are mapped into contiguous kernel virtual space with PAGE_KERNEL +protections. + +alloc_thread_stack_node() calls __vmalloc_node_range() to allocate stack +with PAGE_KERNEL protections. + +- Allocated stacks are cached and later reused by new threads, so memcg + accounting is performed manually on assigning/releasing stacks to tasks. + Hence, __vmalloc_node_range is called without __GFP_ACCOUNT. +- vm_struct is cached to be able to find when thread free is initiated + in interrupt context. free_thread_stack() can be called in interrupt + context. +- On arm64, all VMAP's stacks need to have the same alignment to ensure + that VMAP'd stack overflow detection works correctly. Arch specific + vmap stack allocator takes care of this detail. +- This does not address interrupt stacks - according to the original patch + +Thread stack allocation is initiated from clone(), fork(), vfork(), +kernel_thread() via kernel_clone(). Leaving a few hints for searching +the code base to understand when and how thread stack is allocated. + +Bulk of the code is in: +`kernel/fork.c `. + +stack_vm_area pointer in task_struct keeps track of the virtually allocated +stack and a non-null stack_vm_area pointer serves as a indication that the +virtually mapped kernel stacks are enabled. + +:: + + struct vm_struct *stack_vm_area; + +Stack overflow handling +----------------------- + +Leading and trailing guard pages help detect stack overflows. When stack +overflows into the guard pages, handlers have to be careful not overflow +the stack again. When handlers are called, it is likely that very little +stack space is left. + +On x86, this is done by handling the page fault indicating the kernel +stack overflow on the double-fault stack. + +Testing VMAP allocation with guard pages +---------------------------------------- + +How do we ensure that VMAP_STACK is actually allocating with a leading +and trailing guard page? The following lkdtm tests can help detect any +regressions. + +:: + + void lkdtm_STACK_GUARD_PAGE_LEADING() + void lkdtm_STACK_GUARD_PAGE_TRAILING() + +Conclusions +----------- + +- A percpu cache of vmalloced stacks appears to be a bit faster than a + high-order stack allocation, at least when the cache hits. +- THREAD_INFO_IN_TASK gets rid of arch-specific thread_info entirely and + simply embed the thread_info (containing only flags) and 'int cpu' into + task_struct. +- The thread stack can be free'ed as soon as the task is dead (without + waiting for RCU) and then, if vmapped stacks are in use, cache the + entire stack for reuse on the same cpu. -- cgit v1.2.3