xref: /linux/include/linux/entry-common.h (revision a9f3a74a29af095f3e1b89e9176f8127912ae0f0)

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_ENTRYCOMMON_H
#define __LINUX_ENTRYCOMMON_H

#include <linux/tracehook.h>
#include <linux/syscalls.h>
#include <linux/seccomp.h>
#include <linux/sched.h>

#include <asm/entry-common.h>

/*
 * Define dummy _TIF work flags if not defined by the architecture or for
 * disabled functionality.
 */
#ifndef _TIF_SYSCALL_EMU
# define _TIF_SYSCALL_EMU		(0)
#endif

#ifndef _TIF_SYSCALL_TRACEPOINT
# define _TIF_SYSCALL_TRACEPOINT	(0)
#endif

#ifndef _TIF_SECCOMP
# define _TIF_SECCOMP			(0)
#endif

#ifndef _TIF_SYSCALL_AUDIT
# define _TIF_SYSCALL_AUDIT		(0)
#endif

#ifndef _TIF_PATCH_PENDING
# define _TIF_PATCH_PENDING		(0)
#endif

#ifndef _TIF_UPROBE
# define _TIF_UPROBE			(0)
#endif

/*
 * TIF flags handled in syscall_enter_from_usermode()
 */
#ifndef ARCH_SYSCALL_ENTER_WORK
# define ARCH_SYSCALL_ENTER_WORK	(0)
#endif

#define SYSCALL_ENTER_WORK						\
	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP |	\
	 _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_EMU |			\
	 ARCH_SYSCALL_ENTER_WORK)

/*
 * TIF flags handled in syscall_exit_to_user_mode()
 */
#ifndef ARCH_SYSCALL_EXIT_WORK
# define ARCH_SYSCALL_EXIT_WORK		(0)
#endif

#define SYSCALL_EXIT_WORK						\
	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT |			\
	 _TIF_SYSCALL_TRACEPOINT | ARCH_SYSCALL_EXIT_WORK)

/*
 * TIF flags handled in exit_to_user_mode_loop()
 */
#ifndef ARCH_EXIT_TO_USER_MODE_WORK
# define ARCH_EXIT_TO_USER_MODE_WORK		(0)
#endif

#define EXIT_TO_USER_MODE_WORK						\
	(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE |		\
	 _TIF_NEED_RESCHED | _TIF_PATCH_PENDING |			\
	 ARCH_EXIT_TO_USER_MODE_WORK)

/**
 * arch_check_user_regs - Architecture specific sanity check for user mode regs
 * @regs:	Pointer to currents pt_regs
 *
 * Defaults to an empty implementation. Can be replaced by architecture
 * specific code.
 *
 * Invoked from syscall_enter_from_user_mode() in the non-instrumentable
 * section. Use __always_inline so the compiler cannot push it out of line
 * and make it instrumentable.
 */
static __always_inline void arch_check_user_regs(struct pt_regs *regs);

#ifndef arch_check_user_regs
static __always_inline void arch_check_user_regs(struct pt_regs *regs) {}
#endif

/**
 * arch_syscall_enter_tracehook - Wrapper around tracehook_report_syscall_entry()
 * @regs:	Pointer to currents pt_regs
 *
 * Returns: 0 on success or an error code to skip the syscall.
 *
 * Defaults to tracehook_report_syscall_entry(). Can be replaced by
 * architecture specific code.
 *
 * Invoked from syscall_enter_from_user_mode()
 */
static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs);

#ifndef arch_syscall_enter_tracehook
static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs)
{
	return tracehook_report_syscall_entry(regs);
}
#endif

/**
 * syscall_enter_from_user_mode - Check and handle work before invoking
 *				 a syscall
 * @regs:	Pointer to currents pt_regs
 * @syscall:	The syscall number
 *
 * Invoked from architecture specific syscall entry code with interrupts
 * disabled. The calling code has to be non-instrumentable. When the
 * function returns all state is correct and the subsequent functions can be
 * instrumented.
 *
 * Returns: The original or a modified syscall number
 *
 * If the returned syscall number is -1 then the syscall should be
 * skipped. In this case the caller may invoke syscall_set_error() or
 * syscall_set_return_value() first.  If neither of those are called and -1
 * is returned, then the syscall will fail with ENOSYS.
 *
 * The following functionality is handled here:
 *
 *  1) Establish state (lockdep, RCU (context tracking), tracing)
 *  2) TIF flag dependent invocations of arch_syscall_enter_tracehook(),
 *     __secure_computing(), trace_sys_enter()
 *  3) Invocation of audit_syscall_entry()
 */
long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall);

/**
 * local_irq_enable_exit_to_user - Exit to user variant of local_irq_enable()
 * @ti_work:	Cached TIF flags gathered with interrupts disabled
 *
 * Defaults to local_irq_enable(). Can be supplied by architecture specific
 * code.
 */
static inline void local_irq_enable_exit_to_user(unsigned long ti_work);

#ifndef local_irq_enable_exit_to_user
static inline void local_irq_enable_exit_to_user(unsigned long ti_work)
{
	local_irq_enable();
}
#endif

/**
 * local_irq_disable_exit_to_user - Exit to user variant of local_irq_disable()
 *
 * Defaults to local_irq_disable(). Can be supplied by architecture specific
 * code.
 */
static inline void local_irq_disable_exit_to_user(void);

#ifndef local_irq_disable_exit_to_user
static inline void local_irq_disable_exit_to_user(void)
{
	local_irq_disable();
}
#endif

/**
 * arch_exit_to_user_mode_work - Architecture specific TIF work for exit
 *				 to user mode.
 * @regs:	Pointer to currents pt_regs
 * @ti_work:	Cached TIF flags gathered with interrupts disabled
 *
 * Invoked from exit_to_user_mode_loop() with interrupt enabled
 *
 * Defaults to NOOP. Can be supplied by architecture specific code.
 */
static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
					       unsigned long ti_work);

#ifndef arch_exit_to_user_mode_work
static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
					       unsigned long ti_work)
{
}
#endif

/**
 * arch_exit_to_user_mode_prepare - Architecture specific preparation for
 *				    exit to user mode.
 * @regs:	Pointer to currents pt_regs
 * @ti_work:	Cached TIF flags gathered with interrupts disabled
 *
 * Invoked from exit_to_user_mode_prepare() with interrupt disabled as the last
 * function before return. Defaults to NOOP.
 */
static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
						  unsigned long ti_work);

#ifndef arch_exit_to_user_mode_prepare
static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
						  unsigned long ti_work)
{
}
#endif

/**
 * arch_exit_to_user_mode - Architecture specific final work before
 *			    exit to user mode.
 *
 * Invoked from exit_to_user_mode() with interrupt disabled as the last
 * function before return. Defaults to NOOP.
 *
 * This needs to be __always_inline because it is non-instrumentable code
 * invoked after context tracking switched to user mode.
 *
 * An architecture implementation must not do anything complex, no locking
 * etc. The main purpose is for speculation mitigations.
 */
static __always_inline void arch_exit_to_user_mode(void);

#ifndef arch_exit_to_user_mode
static __always_inline void arch_exit_to_user_mode(void) { }
#endif

/**
 * arch_do_signal -  Architecture specific signal delivery function
 * @regs:	Pointer to currents pt_regs
 *
 * Invoked from exit_to_user_mode_loop().
 */
void arch_do_signal(struct pt_regs *regs);

/**
 * arch_syscall_exit_tracehook - Wrapper around tracehook_report_syscall_exit()
 * @regs:	Pointer to currents pt_regs
 * @step:	Indicator for single step
 *
 * Defaults to tracehook_report_syscall_exit(). Can be replaced by
 * architecture specific code.
 *
 * Invoked from syscall_exit_to_user_mode()
 */
static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step);

#ifndef arch_syscall_exit_tracehook
static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step)
{
	tracehook_report_syscall_exit(regs, step);
}
#endif

/**
 * syscall_exit_to_user_mode - Handle work before returning to user mode
 * @regs:	Pointer to currents pt_regs
 *
 * Invoked with interrupts enabled and fully valid regs. Returns with all
 * work handled, interrupts disabled such that the caller can immediately
 * switch to user mode. Called from architecture specific syscall and ret
 * from fork code.
 *
 * The call order is:
 *  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). Invokes
 *	  arch_exit_to_user_mode_work() for architecture specific TIF work
 *	- 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
 */
void syscall_exit_to_user_mode(struct pt_regs *regs);

/**
 * irqentry_enter_from_user_mode - Establish state before invoking the irq handler
 * @regs:	Pointer to currents pt_regs
 *
 * Invoked from architecture specific entry code with interrupts disabled.
 * Can only be called when the interrupt entry came from user mode. The
 * calling code must be non-instrumentable.  When the function returns all
 * state is correct and the subsequent functions can be instrumented.
 *
 * The function establishes state (lockdep, RCU (context tracking), tracing)
 */
void irqentry_enter_from_user_mode(struct pt_regs *regs);

/**
 * irqentry_exit_to_user_mode - Interrupt exit work
 * @regs:	Pointer to current's pt_regs
 *
 * Invoked with interrupts disbled and fully valid regs. Returns with all
 * work handled, interrupts disabled such that the caller can immediately
 * switch to user mode. Called from architecture specific interrupt
 * handling code.
 *
 * The call order is #2 and #3 as described in syscall_exit_to_user_mode().
 * Interrupt exit is not invoking #1 which is the syscall specific one time
 * work.
 */
void irqentry_exit_to_user_mode(struct pt_regs *regs);

#endif