Commit c6156e1d authored by Sven Schnelle's avatar Sven Schnelle Committed by Thomas Gleixner
Browse files

entry: Add syscall_exit_to_user_mode_work() 



This is the same as syscall_exit_to_user_mode() but without calling
exit_to_user_mode(). This can be used if there is an architectural reason
to avoid the combo function, e.g. restarting a syscall without returning to
userspace. Before returning to user space the caller has to invoke
exit_to_user_mode().

[ tglx: Amended comments ]

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/20201201142755.31931-6-svens@linux.ibm.com
parent 310de1a6

include/linux/entry-common.h

+20 −0
Original line number Diff line number Diff line
@@ -316,9 +316,25 @@ static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step) 
 * 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.

 */

void exit_to_user_mode(void);



/**

 * 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
@@ -343,6 +359,10 @@ void exit_to_user_mode(void); 
 *

 *  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 seperate functions.

 */

void syscall_exit_to_user_mode(struct pt_regs *regs);

kernel/entry/common.c

+12 −2
Original line number Diff line number Diff line
@@ -282,12 +282,22 @@ static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs) 
		syscall_exit_work(regs, work);

}



__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)

static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)

{

	instrumentation_begin();

	syscall_exit_to_user_mode_prepare(regs);

	local_irq_disable_exit_to_user();

	exit_to_user_mode_prepare(regs);

}



void syscall_exit_to_user_mode_work(struct pt_regs *regs)

{

	__syscall_exit_to_user_mode_work(regs);

}



__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)

{

	instrumentation_begin();

	__syscall_exit_to_user_mode_work(regs);

	instrumentation_end();

	__exit_to_user_mode();

}