From cf9610f9116d55c5a66ef9f1faecacabd93a9322 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 24 Aug 2026 08:46:03 -0700 Subject: Merge tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl Pull pin control updates from Linus Walleij: "Core changes: - Use the non-blocking mux_state_try_select() in the generic MUX pin control back-end - Free pin maps on pinctrl_generic_to_map() failure in the core helpers New hardware pin control: - Qualcomm Maili TLMM SoC, PMG1110 PMIC, and Eliza LPASS LPI TLMM SoC (this is for the low power audio, LPASS = Low Power Audio SubSystem portions) - Upboard support on top of the Intel pin controller - Apple T6030 and T6031 support (just compatible strings) - Samsung Exynos 8855 SoC - Mediatek MT6858 SoC - Rockchip RK3308B and RV1106 SoCs - Airoha EN7523 and AN7563 SoCs Improvements: - Qualcomm TLMM GPIOs are unconditionally marked as wakeup capable - Qualcomm improvements on top of the Qualcomm PDC (power domain controller) irqchip improvements from tglx:s tree - Qualcomm IPQ806x and IPQ9650 non-urgent pin grop fixups - The NPCM8xx driver has been put into shape fixing many pin and group definitions - Some non-urgent Tegra 264 pin assignments are fixed up - Some non-urgent fixups to Airoha AN7581 and AN7583 registers and pin assignments, missing features etc" * tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl: (130 commits) dt-bindings: pinctrl: Convert TI DA850 pupd to DT schema pinctrl: meson: sync some modify from A4 pinctrl: meson: a4: Add input enable pin configuration pinctrl: realtek: rtd1625: remove unused group name spdif_sel pinctrl: realtek: rtd1625: fix base_bit for VE4 GPIO 13 dt-bindings: pinctrl: microchip,pic32mzda-pinctrl: Convert to DT schema Revert "Merge branch 'ib-rsk7204' into devel" pinctrl: rockchip: Add RV1106 pinctrl support dt-bindings: pinctrl: rockchip: Add RV1106 compatible pinctrl: rockchip: Decode drive strength in the get function pinctrl: fix PINCTRL_GENERIC_MUX not always being selectable pinctrl: airoha: add support of an7563 SoC dt-bindings: pinctrl: airoha: add support of an7563 pin controller pinctrl: airoha: try to find chip scu node by phandle first pinctrl: airoha: add support of en7523 SoC dt-bindings: pinctrl: airoha: add support of en7523 pin controller pinctrl: airoha: an7583: add support for olt pinmux pinctrl: airoha: an7583: add support for pon_alt pinmux pinctrl: airoha: an7583: add support for npu_uart pinmux dt-bindings: pinctrl: airoha: an7583: add missed features ... --- .../admin-guide/syscall-user-dispatch.rst | 99 ++++++++++++++++++++++ 1 file changed, 99 insertions(+) create mode 100644 Documentation/admin-guide/syscall-user-dispatch.rst (limited to 'Documentation/admin-guide/syscall-user-dispatch.rst') diff --git a/Documentation/admin-guide/syscall-user-dispatch.rst b/Documentation/admin-guide/syscall-user-dispatch.rst new file mode 100644 index 000000000..c1768d9e8 --- /dev/null +++ b/Documentation/admin-guide/syscall-user-dispatch.rst @@ -0,0 +1,99 @@ +.. SPDX-License-Identifier: GPL-2.0 + +===================== +Syscall User Dispatch +===================== + +Background +---------- + +Compatibility layers like Wine need a way to efficiently emulate system +calls of only a part of their process - the part that has the +incompatible code - while being able to execute native syscalls without +a high performance penalty on the native part of the process. Seccomp +falls short on this task, since it has limited support to efficiently +filter syscalls based on memory regions, and it doesn't support removing +filters. Therefore a new mechanism is necessary. + +Syscall User Dispatch brings the filtering of the syscall dispatcher +address back to userspace. The application is in control of a flip +switch, indicating the current personality of the process. A +multiple-personality application can then flip the switch without +invoking the kernel, when crossing the compatibility layer API +boundaries, to enable/disable the syscall redirection and execute +syscalls directly (disabled) or send them to be emulated in userspace +through a SIGSYS. + +The goal of this design is to provide very quick compatibility layer +boundary crosses, which is achieved by not executing a syscall to change +personality every time the compatibility layer executes. Instead, a +userspace memory region exposed to the kernel indicates the current +personality, and the application simply modifies that variable to +configure the mechanism. + +There is a relatively high cost associated with handling signals on most +architectures, like x86, but at least for Wine, syscalls issued by +native Windows code are currently not known to be a performance problem, +since they are quite rare, at least for modern gaming applications. + +Since this mechanism is designed to capture syscalls issued by +non-native applications, it must function on syscalls whose invocation +ABI is completely unexpected to Linux. Syscall User Dispatch, therefore +doesn't rely on any of the syscall ABI to make the filtering. It uses +only the syscall dispatcher address and the userspace key. + +As the ABI of these intercepted syscalls is unknown to Linux, these +syscalls are not instrumentable via ptrace or the syscall tracepoints. + +Interface +--------- + +A thread can setup this mechanism on supported kernels by executing the +following prctl: + + prctl(PR_SET_SYSCALL_USER_DISPATCH, , , , [selector]) + + is either PR_SYS_DISPATCH_EXCLUSIVE_ON/PR_SYS_DISPATCH_INCLUSIVE_ON +or PR_SYS_DISPATCH_OFF, to enable and disable the mechanism globally for +that thread. When PR_SYS_DISPATCH_OFF is used, the other fields must be zero. + +For PR_SYS_DISPATCH_EXCLUSIVE_ON [, +) delimit +a memory region interval from which syscalls are always executed directly, +regardless of the userspace selector. This provides a fast path for the +C library, which includes the most common syscall dispatchers in the native +code applications, and also provides a way for the signal handler to return +without triggering a nested SIGSYS on (rt\_)sigreturn. Users of this +interface should make sure that at least the signal trampoline code is +included in this region. In addition, for syscalls that implement the +trampoline code on the vDSO, that trampoline is never intercepted. + +For PR_SYS_DISPATCH_INCLUSIVE_ON [, +) delimit +a memory region interval from which syscalls are dispatched based on +the userspace selector. Syscalls from outside of the range are always +executed directly. + +[selector] is a pointer to a char-sized region in the process memory +region, that provides a quick way to enable disable syscall redirection +thread-wide, without the need to invoke the kernel directly. selector +can be set to SYSCALL_DISPATCH_FILTER_ALLOW or SYSCALL_DISPATCH_FILTER_BLOCK. +Any other value should terminate the program with a SIGSYS. + +Additionally, a tasks syscall user dispatch configuration can be peeked +and poked via the PTRACE_(GET|SET)_SYSCALL_USER_DISPATCH_CONFIG ptrace +requests. This is useful for checkpoint/restart software. + +Security Notes +-------------- + +Syscall User Dispatch provides functionality for compatibility layers to +quickly capture system calls issued by a non-native part of the +application, while not impacting the Linux native regions of the +process. It is not a mechanism for sandboxing system calls, and it +should not be seen as a security mechanism, since it is trivial for a +malicious application to subvert the mechanism by jumping to an allowed +dispatcher region prior to executing the syscall, or to discover the +address and modify the selector value. If the use case requires any +kind of security sandboxing, Seccomp should be used instead. + +Any fork or exec of the existing process resets the mechanism to +PR_SYS_DISPATCH_OFF. -- cgit v1.3.1