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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_ENTRYCOMMON_H
#define __LINUX_ENTRYCOMMON_H
#include <linux/static_call_types.h>
#include <linux/ptrace.h>
#include <linux/syscalls.h>
#include <linux/seccomp.h>
#include <linux/sched.h>
#include <linux/context_tracking.h>
#include <linux/livepatch.h>
#include <linux/resume_user_mode.h>
#include <linux/tick.h>
#include <linux/kmsan.h>
#include <asm/entry-common.h>
/*
* Define dummy _TIF work flags if not defined by the architecture or for
* disabled functionality.
*/
#ifndef _TIF_PATCH_PENDING
# define _TIF_PATCH_PENDING (0)
#endif
#ifndef _TIF_UPROBE
# define _TIF_UPROBE (0)
#endif
/*
* SYSCALL_WORK flags handled in syscall_enter_from_user_mode()
*/
#ifndef ARCH_SYSCALL_WORK_ENTER
# define ARCH_SYSCALL_WORK_ENTER (0)
#endif
/*
* SYSCALL_WORK flags handled in syscall_exit_to_user_mode()
*/
#ifndef ARCH_SYSCALL_WORK_EXIT
# define ARCH_SYSCALL_WORK_EXIT (0)
#endif
#define SYSCALL_WORK_ENTER (SYSCALL_WORK_SECCOMP | \
SYSCALL_WORK_SYSCALL_TRACEPOINT | \
SYSCALL_WORK_SYSCALL_TRACE | \
SYSCALL_WORK_SYSCALL_EMU | \
SYSCALL_WORK_SYSCALL_AUDIT | \
SYSCALL_WORK_SYSCALL_USER_DISPATCH | \
ARCH_SYSCALL_WORK_ENTER)
#define SYSCALL_WORK_EXIT (SYSCALL_WORK_SYSCALL_TRACEPOINT | \
SYSCALL_WORK_SYSCALL_TRACE | \
SYSCALL_WORK_SYSCALL_AUDIT | \
SYSCALL_WORK_SYSCALL_USER_DISPATCH | \
SYSCALL_WORK_SYSCALL_EXIT_TRAP | \
ARCH_SYSCALL_WORK_EXIT)
/*
* 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 | _TIF_NOTIFY_SIGNAL | \
ARCH_EXIT_TO_USER_MODE_WORK)
/**
* arch_enter_from_user_mode - 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_enter_from_user_mode(struct pt_regs *regs);
#ifndef arch_enter_from_user_mode
static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs) {}
#endif
/**
* enter_from_user_mode - Establish state when coming from user mode
*
* Syscall/interrupt entry disables interrupts, but user mode is traced as
* interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
*
* 1) Tell lockdep that interrupts are disabled
* 2) Invoke context tracking if enabled to reactivate RCU
* 3) Trace interrupts off state
*
* 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 interrupts are still
* disabled. The subsequent functions can be instrumented.
*
* This is invoked when there is architecture specific functionality to be
* done between establishing state and enabling interrupts. The caller must
* enable interrupts before invoking syscall_enter_from_user_mode_work().
*/
static __always_inline void enter_from_user_mode(struct pt_regs *regs)
{
arch_enter_from_user_mode(regs);
lockdep_hardirqs_off(CALLER_ADDR0);
CT_WARN_ON(__ct_state() != CONTEXT_USER);
user_exit_irqoff();
instrumentation_begin();
kmsan_unpoison_entry_regs(regs);
trace_hardirqs_off_finish();
instrumentation_end();
}
/**
* syscall_enter_from_user_mode_prepare - Establish state and enable interrupts
* @regs: Pointer to currents pt_regs
*
* 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, interrupts are enabled and the
* subsequent functions can be instrumented.
*
* This handles lockdep, RCU (context tracking) and tracing state, i.e.
* the functionality provided by enter_from_user_mode().
*
* This is invoked when there is extra architecture specific functionality
* to be done between establishing state and handling user mode entry work.
*/
void syscall_enter_from_user_mode_prepare(struct pt_regs *regs);
long syscall_trace_enter(struct pt_regs *regs, long syscall,
unsigned long work);
/**
* syscall_enter_from_user_mode_work - 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
* enabled after invoking syscall_enter_from_user_mode_prepare() and extra
* architecture specific work.
*
* 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.
*
* It handles the following work items:
*
* 1) syscall_work flag dependent invocations of
* ptrace_report_syscall_entry(), __secure_computing(), trace_sys_enter()
* 2) Invocation of audit_syscall_entry()
*/
static __always_inline long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
{
unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
if (work & SYSCALL_WORK_ENTER)
syscall = syscall_trace_enter(regs, syscall, work);
return syscall;
}
/**
* syscall_enter_from_user_mode - Establish state and 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, interrupts are enabled and the
* subsequent functions can be instrumented.
*
* This is combination of syscall_enter_from_user_mode_prepare() and
* syscall_enter_from_user_mode_work().
*
* Returns: The original or a modified syscall number. See
* syscall_enter_from_user_mode_work() for further explanation.
*/
static __always_inline long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
{
long ret;
enter_from_user_mode(regs);
instrumentation_begin();
local_irq_enable();
ret = syscall_enter_from_user_mode_work(regs, syscall);
instrumentation_end();
return ret;
}
/**
* 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_or_restart - Architecture specific signal delivery function
* @regs: Pointer to currents pt_regs
*
* Invoked from exit_to_user_mode_loop().
*/
void arch_do_signal_or_restart(struct pt_regs *regs);
/**
* exit_to_user_mode_loop - do any pending work before leaving to user space
*/
unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
unsigned long ti_work);
/**
* exit_to_user_mode_prepare - call exit_to_user_mode_loop() if required
* @regs: Pointer to pt_regs on entry stack
*
* 1) check that interrupts are disabled
* 2) call tick_nohz_user_enter_prepare()
* 3) call exit_to_user_mode_loop() if any flags from
* EXIT_TO_USER_MODE_WORK are set
* 4) check that interrupts are still disabled
*/
static __always_inline void exit_to_user_mode_prepare(struct pt_regs *regs)
{
unsigned long ti_work;
lockdep_assert_irqs_disabled();
/* Flush pending rcuog wakeup before the last need_resched() check */
tick_nohz_user_enter_prepare();
ti_work = read_thread_flags();
if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
ti_work = exit_to_user_mode_loop(regs, ti_work);
arch_exit_to_user_mode_prepare(regs, ti_work);
/* Ensure that kernel state is sane for a return to userspace */
kmap_assert_nomap();
lockdep_assert_irqs_disabled();
lockdep_sys_exit();
}
/**
* exit_to_user_mode - Fixup state when exiting to user mode
*
* Syscall/interrupt exit enables interrupts, but the kernel state is
* interrupts disabled when this is invoked. Also tell RCU about it.
*
* 1) Trace interrupts on state
* 2) Invoke context tracking if enabled to adjust RCU state
* 3) Invoke architecture specific last minute exit code, e.g. speculation
* mitigations, etc.: arch_exit_to_user_mode()
* 4) Tell lockdep that interrupts are enabled
*
* Invoked from architecture specific code when syscall_exit_to_user_mode()
* is not suitable as the last step before returning to userspace. Must be
* invoked with interrupts disabled and the caller must be
* non-instrumentable.
* The caller has to invoke syscall_exit_to_user_mode_work() before this.
*/
static __always_inline void exit_to_user_mode(void)
{
instrumentation_begin();
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare();
instrumentation_end();
user_enter_irqoff();
arch_exit_to_user_mode();
lockdep_hardirqs_on(CALLER_ADDR0);
}
/**
* syscall_exit_to_user_mode_work - Handle work before returning to user mode
* @regs: Pointer to currents pt_regs
*
* Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
* exit_to_user_mode() to perform the final transition to user mode.
*
* Calling convention is the same as for syscall_exit_to_user_mode() and it
* returns with all work handled and interrupts disabled. The caller must
* invoke exit_to_user_mode() before actually switching to user mode to
* make the final state transitions. Interrupts must stay disabled between
* return from this function and the invocation of exit_to_user_mode().
*/
void syscall_exit_to_user_mode_work(struct pt_regs *regs);
/**
* 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
* - ptrace (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), i.e. the
* functionality in exit_to_user_mode().
*
* This is a combination of syscall_exit_to_user_mode_work() (1,2) and
* exit_to_user_mode(). This function is preferred unless there is a
* compelling architectural reason to use the separate functions.
*/
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 disabled 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);
#ifndef irqentry_state
/**
* struct irqentry_state - Opaque object for exception state storage
* @exit_rcu: Used exclusively in the irqentry_*() calls; signals whether the
* exit path has to invoke ct_irq_exit().
* @lockdep: Used exclusively in the irqentry_nmi_*() calls; ensures that
* lockdep state is restored correctly on exit from nmi.
*
* This opaque object is filled in by the irqentry_*_enter() functions and
* must be passed back into the corresponding irqentry_*_exit() functions
* when the exception is complete.
*
* Callers of irqentry_*_[enter|exit]() must consider this structure opaque
* and all members private. Descriptions of the members are provided to aid in
* the maintenance of the irqentry_*() functions.
*/
typedef struct irqentry_state {
union {
bool exit_rcu;
bool lockdep;
};
} irqentry_state_t;
#endif
/**
* irqentry_enter - Handle state tracking on ordinary interrupt entries
* @regs: Pointer to pt_regs of interrupted context
*
* Invokes:
* - lockdep irqflag state tracking as low level ASM entry disabled
* interrupts.
*
* - Context tracking if the exception hit user mode.
*
* - The hardirq tracer to keep the state consistent as low level ASM
* entry disabled interrupts.
*
* As a precondition, this requires that the entry came from user mode,
* idle, or a kernel context in which RCU is watching.
*
* For kernel mode entries RCU handling is done conditional. If RCU is
* watching then the only RCU requirement is to check whether the tick has
* to be restarted. If RCU is not watching then ct_irq_enter() has to be
* invoked on entry and ct_irq_exit() on exit.
*
* Avoiding the ct_irq_enter/exit() calls is an optimization but also
* solves the problem of kernel mode pagefaults which can schedule, which
* is not possible after invoking ct_irq_enter() without undoing it.
*
* For user mode entries irqentry_enter_from_user_mode() is invoked to
* establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
* would not be possible.
*
* Returns: An opaque object that must be passed to idtentry_exit()
*/
irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
/**
* irqentry_exit_cond_resched - Conditionally reschedule on return from interrupt
*
* Conditional reschedule with additional sanity checks.
*/
void raw_irqentry_exit_cond_resched(void);
#ifdef CONFIG_PREEMPT_DYNAMIC
#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
#define irqentry_exit_cond_resched_dynamic_enabled raw_irqentry_exit_cond_resched
#define irqentry_exit_cond_resched_dynamic_disabled NULL
DECLARE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
#define irqentry_exit_cond_resched() static_call(irqentry_exit_cond_resched)()
#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
void dynamic_irqentry_exit_cond_resched(void);
#define irqentry_exit_cond_resched() dynamic_irqentry_exit_cond_resched()
#endif
#else /* CONFIG_PREEMPT_DYNAMIC */
#define irqentry_exit_cond_resched() raw_irqentry_exit_cond_resched()
#endif /* CONFIG_PREEMPT_DYNAMIC */
/**
* irqentry_exit - Handle return from exception that used irqentry_enter()
* @regs: Pointer to pt_regs (exception entry regs)
* @state: Return value from matching call to irqentry_enter()
*
* Depending on the return target (kernel/user) this runs the necessary
* preemption and work checks if possible and required and returns to
* the caller with interrupts disabled and no further work pending.
*
* This is the last action before returning to the low level ASM code which
* just needs to return to the appropriate context.
*
* Counterpart to irqentry_enter().
*/
void noinstr irqentry_exit(struct pt_regs *regs, irqentry_state_t state);
/**
* irqentry_nmi_enter - Handle NMI entry
* @regs: Pointer to currents pt_regs
*
* Similar to irqentry_enter() but taking care of the NMI constraints.
*/
irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs);
/**
* irqentry_nmi_exit - Handle return from NMI handling
* @regs: Pointer to pt_regs (NMI entry regs)
* @irq_state: Return value from matching call to irqentry_nmi_enter()
*
* Last action before returning to the low level assembly code.
*
* Counterpart to irqentry_nmi_enter().
*/
void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state);
#endif