The following commit has been merged into the core/entry branch of tip: Commit-ID: 1568b5540b3e6ff3fe43a2cf889cb777cf8149fc Gitweb: https://git.kernel.org/tip/1568b5540b3e6ff3fe43a2cf889cb777cf8149fc Author: Sven Schnelle <sv...@linux.ibm.com> AuthorDate: Tue, 01 Dec 2020 15:27:55 +01:00 Committer: Thomas Gleixner <t...@linutronix.de> CommitterDate: Wed, 02 Dec 2020 10:32:18 +01:00
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: Sven Schnelle <sv...@linux.ibm.com> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Link: https://lore.kernel.org/r/20201201142755.31931-6-sv...@linux.ibm.com --- include/linux/entry-common.h | 20 ++++++++++++++++++++ kernel/entry/common.c | 14 ++++++++++++-- 2 files changed, 32 insertions(+), 2 deletions(-) diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h index e370be8..7c581a4 100644 --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -316,10 +316,26 @@ 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); diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 48d30ce..d6b7393 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -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(); }
