From 310de1a678b2184c078c593dae343cb79c807f8d Mon Sep 17 00:00:00 2001 From: Sven Schnelle Date: Tue, 1 Dec 2020 15:27:54 +0100 Subject: [PATCH] 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: Sven Schnelle Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20201201142755.31931-5-svens@linux.ibm.com --- include/linux/entry-common.h | 23 +++++++++++++++++++++-- kernel/entry/common.c | 18 ++++++------------ 2 files changed, 27 insertions(+), 14 deletions(-) diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h index da60980a2e7b6..e370be8121aa1 100644 --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -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); diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 17b1e032afe79..48d30ce2e00e8 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -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) { } -- 2.30.2