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entry: Add syscall_exit_to_user_mode_work()

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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: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201201142755.31931-6-svens@linux.ibm.com
This commit is contained in:
Sven Schnelle 2020-12-01 15:27:55 +01:00 committed by Thomas Gleixner
parent 310de1a678
commit c6156e1da6
2 changed files with 32 additions and 2 deletions
include/linux
entry-common.h
kernel/entry
common.c

20
include/linux/entry-common.h
View File

@ -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 * is not suitable as the last step before returning to userspace. Must be
* invoked with interrupts disabled and the caller must be * invoked with interrupts disabled and the caller must be
* non-instrumentable. * non-instrumentable.
* The caller has to invoke syscall_exit_to_user_mode_work() before this.
*/ */
void exit_to_user_mode(void); 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 * syscall_exit_to_user_mode - Handle work before returning to user mode
* @regs: Pointer to currents pt_regs * @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 * 3) Final transition (lockdep, tracing, context tracking, RCU), i.e. the
* functionality in exit_to_user_mode(). * 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); void syscall_exit_to_user_mode(struct pt_regs *regs);

14
kernel/entry/common.c
View File

@ -282,12 +282,22 @@ static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
syscall_exit_work(regs, work); 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); syscall_exit_to_user_mode_prepare(regs);
local_irq_disable_exit_to_user(); local_irq_disable_exit_to_user();
exit_to_user_mode_prepare(regs); 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(); instrumentation_end();
__exit_to_user_mode(); __exit_to_user_mode();
} }