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![Gabriel Krisman Bertazi](/assets/img/avatar_default.png)
Syscall User Dispatch (SUD) must take precedence over seccomp and ptrace, since the use case is emulation (it can be invoked with a different ABI) such that seccomp filtering by syscall number doesn't make sense in the first place. In addition, either the syscall is dispatched back to userspace, in which case there is no resource for to trace, or the syscall will be executed, and seccomp/ptrace will execute next. Since SUD runs before tracepoints, it needs to be a SYSCALL_WORK_EXIT as well, just to prevent a trace exit event when dispatch was triggered. For that, the on_syscall_dispatch() examines context to skip the tracepoint, audit and other work. [ tglx: Add a comment on the exit side ] Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Andy Lutomirski <luto@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20201127193238.821364-5-krisman@collabora.com
435 lines
14 KiB
C
435 lines
14 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_ENTRYCOMMON_H
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#define __LINUX_ENTRYCOMMON_H
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#include <linux/tracehook.h>
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#include <linux/syscalls.h>
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#include <linux/seccomp.h>
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#include <linux/sched.h>
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#include <asm/entry-common.h>
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/*
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* Define dummy _TIF work flags if not defined by the architecture or for
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* disabled functionality.
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*/
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#ifndef _TIF_PATCH_PENDING
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# define _TIF_PATCH_PENDING (0)
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#endif
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#ifndef _TIF_UPROBE
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# define _TIF_UPROBE (0)
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#endif
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#ifndef _TIF_NOTIFY_SIGNAL
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# define _TIF_NOTIFY_SIGNAL (0)
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#endif
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/*
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* SYSCALL_WORK flags handled in syscall_enter_from_user_mode()
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*/
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#ifndef ARCH_SYSCALL_WORK_ENTER
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# define ARCH_SYSCALL_WORK_ENTER (0)
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#endif
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/*
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* SYSCALL_WORK flags handled in syscall_exit_to_user_mode()
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*/
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#ifndef ARCH_SYSCALL_WORK_EXIT
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# define ARCH_SYSCALL_WORK_EXIT (0)
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#endif
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#define SYSCALL_WORK_ENTER (SYSCALL_WORK_SECCOMP | \
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SYSCALL_WORK_SYSCALL_TRACEPOINT | \
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SYSCALL_WORK_SYSCALL_TRACE | \
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SYSCALL_WORK_SYSCALL_EMU | \
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SYSCALL_WORK_SYSCALL_AUDIT | \
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SYSCALL_WORK_SYSCALL_USER_DISPATCH | \
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ARCH_SYSCALL_WORK_ENTER)
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#define SYSCALL_WORK_EXIT (SYSCALL_WORK_SYSCALL_TRACEPOINT | \
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SYSCALL_WORK_SYSCALL_TRACE | \
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SYSCALL_WORK_SYSCALL_AUDIT | \
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SYSCALL_WORK_SYSCALL_USER_DISPATCH | \
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ARCH_SYSCALL_WORK_EXIT)
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/*
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* TIF flags handled in exit_to_user_mode_loop()
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*/
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#ifndef ARCH_EXIT_TO_USER_MODE_WORK
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# define ARCH_EXIT_TO_USER_MODE_WORK (0)
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#endif
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#define EXIT_TO_USER_MODE_WORK \
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(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
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_TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | \
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ARCH_EXIT_TO_USER_MODE_WORK)
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/**
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* arch_check_user_regs - Architecture specific sanity check for user mode regs
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* @regs: Pointer to currents pt_regs
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*
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* Defaults to an empty implementation. Can be replaced by architecture
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* specific code.
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*
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* Invoked from syscall_enter_from_user_mode() in the non-instrumentable
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* section. Use __always_inline so the compiler cannot push it out of line
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* and make it instrumentable.
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*/
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static __always_inline void arch_check_user_regs(struct pt_regs *regs);
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#ifndef arch_check_user_regs
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static __always_inline void arch_check_user_regs(struct pt_regs *regs) {}
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#endif
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/**
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* arch_syscall_enter_tracehook - Wrapper around tracehook_report_syscall_entry()
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* @regs: Pointer to currents pt_regs
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*
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* Returns: 0 on success or an error code to skip the syscall.
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*
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* Defaults to tracehook_report_syscall_entry(). Can be replaced by
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* architecture specific code.
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*
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* Invoked from syscall_enter_from_user_mode()
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*/
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static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs);
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#ifndef arch_syscall_enter_tracehook
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static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs)
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{
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return tracehook_report_syscall_entry(regs);
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}
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#endif
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/**
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* syscall_enter_from_user_mode_prepare - Establish state and enable interrupts
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* @regs: Pointer to currents pt_regs
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*
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* Invoked from architecture specific syscall entry code with interrupts
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* disabled. The calling code has to be non-instrumentable. When the
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* function returns all state is correct, interrupts are enabled and the
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* subsequent functions can be instrumented.
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*
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* This handles lockdep, RCU (context tracking) and tracing state.
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*
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* This is invoked when there is extra architecture specific functionality
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* to be done between establishing state and handling user mode entry work.
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*/
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void syscall_enter_from_user_mode_prepare(struct pt_regs *regs);
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/**
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* syscall_enter_from_user_mode_work - Check and handle work before invoking
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* a syscall
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* @regs: Pointer to currents pt_regs
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* @syscall: The syscall number
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*
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* Invoked from architecture specific syscall entry code with interrupts
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* enabled after invoking syscall_enter_from_user_mode_prepare() and extra
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* architecture specific work.
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*
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* Returns: The original or a modified syscall number
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*
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* If the returned syscall number is -1 then the syscall should be
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* skipped. In this case the caller may invoke syscall_set_error() or
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* syscall_set_return_value() first. If neither of those are called and -1
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* is returned, then the syscall will fail with ENOSYS.
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*
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* It handles the following work items:
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*
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* 1) syscall_work flag dependent invocations of
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* arch_syscall_enter_tracehook(), __secure_computing(), trace_sys_enter()
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* 2) Invocation of audit_syscall_entry()
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*/
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long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall);
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/**
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* syscall_enter_from_user_mode - Establish state and check and handle work
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* before invoking a syscall
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* @regs: Pointer to currents pt_regs
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* @syscall: The syscall number
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*
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* Invoked from architecture specific syscall entry code with interrupts
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* disabled. The calling code has to be non-instrumentable. When the
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* function returns all state is correct, interrupts are enabled and the
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* subsequent functions can be instrumented.
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*
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* This is combination of syscall_enter_from_user_mode_prepare() and
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* syscall_enter_from_user_mode_work().
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*
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* Returns: The original or a modified syscall number. See
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* syscall_enter_from_user_mode_work() for further explanation.
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*/
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long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall);
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/**
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* local_irq_enable_exit_to_user - Exit to user variant of local_irq_enable()
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* @ti_work: Cached TIF flags gathered with interrupts disabled
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*
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* Defaults to local_irq_enable(). Can be supplied by architecture specific
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* code.
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*/
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static inline void local_irq_enable_exit_to_user(unsigned long ti_work);
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#ifndef local_irq_enable_exit_to_user
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static inline void local_irq_enable_exit_to_user(unsigned long ti_work)
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{
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local_irq_enable();
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}
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#endif
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/**
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* local_irq_disable_exit_to_user - Exit to user variant of local_irq_disable()
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*
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* Defaults to local_irq_disable(). Can be supplied by architecture specific
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* code.
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*/
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static inline void local_irq_disable_exit_to_user(void);
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#ifndef local_irq_disable_exit_to_user
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static inline void local_irq_disable_exit_to_user(void)
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{
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local_irq_disable();
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}
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#endif
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/**
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* arch_exit_to_user_mode_work - Architecture specific TIF work for exit
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* to user mode.
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* @regs: Pointer to currents pt_regs
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* @ti_work: Cached TIF flags gathered with interrupts disabled
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*
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* Invoked from exit_to_user_mode_loop() with interrupt enabled
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*
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* Defaults to NOOP. Can be supplied by architecture specific code.
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*/
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static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
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unsigned long ti_work);
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#ifndef arch_exit_to_user_mode_work
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static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
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unsigned long ti_work)
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{
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}
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#endif
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/**
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* arch_exit_to_user_mode_prepare - Architecture specific preparation for
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* exit to user mode.
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* @regs: Pointer to currents pt_regs
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* @ti_work: Cached TIF flags gathered with interrupts disabled
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*
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* Invoked from exit_to_user_mode_prepare() with interrupt disabled as the last
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* function before return. Defaults to NOOP.
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*/
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static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
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unsigned long ti_work);
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#ifndef arch_exit_to_user_mode_prepare
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static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
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unsigned long ti_work)
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{
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}
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#endif
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/**
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* arch_exit_to_user_mode - Architecture specific final work before
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* exit to user mode.
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*
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* Invoked from exit_to_user_mode() with interrupt disabled as the last
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* function before return. Defaults to NOOP.
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*
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* This needs to be __always_inline because it is non-instrumentable code
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* invoked after context tracking switched to user mode.
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*
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* An architecture implementation must not do anything complex, no locking
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* etc. The main purpose is for speculation mitigations.
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*/
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static __always_inline void arch_exit_to_user_mode(void);
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#ifndef arch_exit_to_user_mode
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static __always_inline void arch_exit_to_user_mode(void) { }
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#endif
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/**
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* arch_do_signal_or_restart - Architecture specific signal delivery function
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* @regs: Pointer to currents pt_regs
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* @has_signal: actual signal to handle
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*
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* Invoked from exit_to_user_mode_loop().
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*/
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void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal);
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/**
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* arch_syscall_exit_tracehook - Wrapper around tracehook_report_syscall_exit()
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* @regs: Pointer to currents pt_regs
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* @step: Indicator for single step
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*
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* Defaults to tracehook_report_syscall_exit(). Can be replaced by
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* architecture specific code.
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*
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* Invoked from syscall_exit_to_user_mode()
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*/
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static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step);
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#ifndef arch_syscall_exit_tracehook
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static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step)
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{
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tracehook_report_syscall_exit(regs, step);
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}
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#endif
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/**
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* syscall_exit_to_user_mode - Handle work before returning to user mode
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* @regs: Pointer to currents pt_regs
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*
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* Invoked with interrupts enabled and fully valid regs. Returns with all
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* work handled, interrupts disabled such that the caller can immediately
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* switch to user mode. Called from architecture specific syscall and ret
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* from fork code.
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*
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* The call order is:
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* 1) One-time syscall exit work:
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* - rseq syscall exit
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* - audit
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* - syscall tracing
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* - tracehook (single stepping)
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*
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* 2) Preparatory work
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* - Exit to user mode loop (common TIF handling). Invokes
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* arch_exit_to_user_mode_work() for architecture specific TIF work
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* - Architecture specific one time work arch_exit_to_user_mode_prepare()
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* - Address limit and lockdep checks
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*
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* 3) Final transition (lockdep, tracing, context tracking, RCU). Invokes
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* arch_exit_to_user_mode() to handle e.g. speculation mitigations
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*/
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void syscall_exit_to_user_mode(struct pt_regs *regs);
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/**
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* irqentry_enter_from_user_mode - Establish state before invoking the irq handler
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* @regs: Pointer to currents pt_regs
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*
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* Invoked from architecture specific entry code with interrupts disabled.
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* Can only be called when the interrupt entry came from user mode. The
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* calling code must be non-instrumentable. When the function returns all
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* state is correct and the subsequent functions can be instrumented.
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*
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* The function establishes state (lockdep, RCU (context tracking), tracing)
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*/
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void irqentry_enter_from_user_mode(struct pt_regs *regs);
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/**
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* irqentry_exit_to_user_mode - Interrupt exit work
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* @regs: Pointer to current's pt_regs
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*
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* Invoked with interrupts disbled and fully valid regs. Returns with all
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* work handled, interrupts disabled such that the caller can immediately
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* switch to user mode. Called from architecture specific interrupt
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* handling code.
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*
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* The call order is #2 and #3 as described in syscall_exit_to_user_mode().
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* Interrupt exit is not invoking #1 which is the syscall specific one time
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* work.
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*/
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void irqentry_exit_to_user_mode(struct pt_regs *regs);
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#ifndef irqentry_state
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/**
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* struct irqentry_state - Opaque object for exception state storage
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* @exit_rcu: Used exclusively in the irqentry_*() calls; signals whether the
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* exit path has to invoke rcu_irq_exit().
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* @lockdep: Used exclusively in the irqentry_nmi_*() calls; ensures that
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* lockdep state is restored correctly on exit from nmi.
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*
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* This opaque object is filled in by the irqentry_*_enter() functions and
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* must be passed back into the corresponding irqentry_*_exit() functions
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* when the exception is complete.
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*
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* Callers of irqentry_*_[enter|exit]() must consider this structure opaque
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* and all members private. Descriptions of the members are provided to aid in
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* the maintenance of the irqentry_*() functions.
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*/
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typedef struct irqentry_state {
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union {
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bool exit_rcu;
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bool lockdep;
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};
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} irqentry_state_t;
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#endif
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/**
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* irqentry_enter - Handle state tracking on ordinary interrupt entries
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* @regs: Pointer to pt_regs of interrupted context
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*
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* Invokes:
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* - lockdep irqflag state tracking as low level ASM entry disabled
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* interrupts.
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*
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* - Context tracking if the exception hit user mode.
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*
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* - The hardirq tracer to keep the state consistent as low level ASM
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* entry disabled interrupts.
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*
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* As a precondition, this requires that the entry came from user mode,
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* idle, or a kernel context in which RCU is watching.
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*
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* For kernel mode entries RCU handling is done conditional. If RCU is
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* watching then the only RCU requirement is to check whether the tick has
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* to be restarted. If RCU is not watching then rcu_irq_enter() has to be
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* invoked on entry and rcu_irq_exit() on exit.
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*
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* Avoiding the rcu_irq_enter/exit() calls is an optimization but also
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* solves the problem of kernel mode pagefaults which can schedule, which
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* is not possible after invoking rcu_irq_enter() without undoing it.
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*
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* For user mode entries irqentry_enter_from_user_mode() is invoked to
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* establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
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* would not be possible.
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*
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* Returns: An opaque object that must be passed to idtentry_exit()
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*/
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irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
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/**
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* irqentry_exit_cond_resched - Conditionally reschedule on return from interrupt
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*
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* Conditional reschedule with additional sanity checks.
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*/
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void irqentry_exit_cond_resched(void);
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/**
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* irqentry_exit - Handle return from exception that used irqentry_enter()
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* @regs: Pointer to pt_regs (exception entry regs)
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* @state: Return value from matching call to irqentry_enter()
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*
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* Depending on the return target (kernel/user) this runs the necessary
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* preemption and work checks if possible and required and returns to
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* the caller with interrupts disabled and no further work pending.
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*
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* This is the last action before returning to the low level ASM code which
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* just needs to return to the appropriate context.
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*
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* Counterpart to irqentry_enter().
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*/
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void noinstr irqentry_exit(struct pt_regs *regs, irqentry_state_t state);
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/**
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* irqentry_nmi_enter - Handle NMI entry
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* @regs: Pointer to currents pt_regs
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*
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* Similar to irqentry_enter() but taking care of the NMI constraints.
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*/
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irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs);
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/**
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* irqentry_nmi_exit - Handle return from NMI handling
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* @regs: Pointer to pt_regs (NMI entry regs)
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* @irq_state: Return value from matching call to irqentry_nmi_enter()
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*
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* Last action before returning to the low level assembly code.
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*
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* Counterpart to irqentry_nmi_enter().
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*/
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void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state);
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#endif
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