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a9f3a74a29
Like syscall entry all architectures have similar and pointlessly different
code to handle pending work before returning from a syscall to user space.
1) One-time syscall exit work:
- rseq syscall exit
- audit
- syscall tracing
- tracehook (single stepping)
2) Preparatory work
- Exit to user mode loop (common TIF handling).
- Architecture specific one time work arch_exit_to_user_mode_prepare()
- Address limit and lockdep checks
3) Final transition (lockdep, tracing, context tracking, RCU). Invokes
arch_exit_to_user_mode() to handle e.g. speculation mitigations
Provide a generic version based on the x86 code which has all the RCU and
instrumentation protections right.
Provide a variant for interrupt return to user mode as well which shares
the above #2 and #3 work items.
After syscall_exit_to_user_mode() and irqentry_exit_to_user_mode() the
architecture code just has to return to user space. The code after
returning from these functions must not be instrumented.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20200722220519.613977173@linutronix.de
310 lines
9.2 KiB
C
310 lines
9.2 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_SYSCALL_EMU
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# define _TIF_SYSCALL_EMU (0)
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#endif
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#ifndef _TIF_SYSCALL_TRACEPOINT
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# define _TIF_SYSCALL_TRACEPOINT (0)
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#endif
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#ifndef _TIF_SECCOMP
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# define _TIF_SECCOMP (0)
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#endif
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#ifndef _TIF_SYSCALL_AUDIT
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# define _TIF_SYSCALL_AUDIT (0)
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#endif
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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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/*
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* TIF flags handled in syscall_enter_from_usermode()
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*/
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#ifndef ARCH_SYSCALL_ENTER_WORK
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# define ARCH_SYSCALL_ENTER_WORK (0)
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#endif
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#define SYSCALL_ENTER_WORK \
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(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \
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_TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_EMU | \
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ARCH_SYSCALL_ENTER_WORK)
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/*
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* TIF flags handled in syscall_exit_to_user_mode()
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*/
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#ifndef ARCH_SYSCALL_EXIT_WORK
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# define ARCH_SYSCALL_EXIT_WORK (0)
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#endif
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#define SYSCALL_EXIT_WORK \
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(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
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_TIF_SYSCALL_TRACEPOINT | ARCH_SYSCALL_EXIT_WORK)
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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 | \
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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 - 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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* disabled. The calling code has to be non-instrumentable. When the
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* function returns all state is correct and the subsequent functions can be
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* instrumented.
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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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* The following functionality is handled here:
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*
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* 1) Establish state (lockdep, RCU (context tracking), tracing)
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* 2) TIF flag dependent invocations of arch_syscall_enter_tracehook(),
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* __secure_computing(), trace_sys_enter()
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* 3) Invocation of audit_syscall_entry()
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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 - Architecture specific signal delivery function
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* @regs: Pointer to currents pt_regs
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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(struct pt_regs *regs);
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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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#endif
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