Commit 310de1a6 authored by Sven Schnelle's avatar Sven Schnelle Committed by Thomas Gleixner
Browse files

entry: Add exit_to_user_mode() wrapper 



Called from architecture specific code when syscall_exit_to_user_mode() is
not suitable. It simply calls __exit_to_user_mode().

This way __exit_to_user_mode() can still be inlined because it is declared
static __always_inline.

[ tglx: Amended comments and moved it to a different place in the header ]

Signed-off-by: default avatarSven Schnelle <svens@linux.ibm.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201201142755.31931-5-svens@linux.ibm.com
parent 96e2fbcc

include/linux/entry-common.h

+21 −2
Original line number Diff line number Diff line
@@ -300,6 +300,25 @@ static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step) 
}

#endif



/**

 * 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.

 */

void exit_to_user_mode(void);



/**

 * syscall_exit_to_user_mode - Handle work before returning to user mode

 * @regs:	Pointer to currents pt_regs
@@ -322,8 +341,8 @@ static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step) 
 *	- 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

 *  3) Final transition (lockdep, tracing, context tracking, RCU), i.e. the

 *     functionality in exit_to_user_mode().

 */

void syscall_exit_to_user_mode(struct pt_regs *regs);

kernel/entry/common.c

+6 −12
Original line number Diff line number Diff line
@@ -117,18 +117,7 @@ noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs) 
	instrumentation_end();

}



/**

 * __exit_to_user_mode - Fixup state when exiting to user mode

 *

 * Syscall/interupt 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.

 * 4) Tell lockdep that interrupts are enabled

 */

/* See comment for exit_to_user_mode() in entry-common.h */

static __always_inline void __exit_to_user_mode(void)

{

	instrumentation_begin();
@@ -141,6 +130,11 @@ static __always_inline void __exit_to_user_mode(void) 
	lockdep_hardirqs_on(CALLER_ADDR0);

}



void noinstr exit_to_user_mode(void)

{

	__exit_to_user_mode();

}



/* Workaround to allow gradual conversion of architecture code */

void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { }