Messages in this thread Patch in this message | | | From | Andy Lutomirski <> | Subject | [PATCH v3 07/11] kentry: Make entry/exit_to_user_mode() arm64-only | Date | Thu, 4 Mar 2021 11:06:00 -0800 |
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exit_to_user_mode() does part, but not all, of the exit-to-user-mode work. It's used only by arm64, and arm64 should stop using it (hint, hint!). Compile it out on other architectures to minimize the chance of error.
enter_from_user_mode() is a legacy way to spell kentry_enter_from_user_mode(). It's also only used by arm64. Give it the same treatment.
Signed-off-by: Andy Lutomirski <luto@kernel.org> --- include/linux/entry-common.h | 34 ++++++---------------------------- kernel/entry/common.c | 4 ++++ 2 files changed, 10 insertions(+), 28 deletions(-)
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h index 5287c6c15a66..a75374f87258 100644 --- a/include/linux/entry-common.h +++ b/include/linux/entry-common.h @@ -97,26 +97,15 @@ static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs } #endif +#ifdef CONFIG_ARM64 /** * enter_from_user_mode - Establish state when coming from user mode * - * Syscall/interrupt entry disables interrupts, but user mode is traced as - * interrupts enabled. Also with NO_HZ_FULL RCU might be idle. + * Legacy variant of kentry_enter_from_user_mode(). Used only by arm64. * - * 1) Tell lockdep that interrupts are disabled - * 2) Invoke context tracking if enabled to reactivate RCU - * 3) Trace interrupts off state - * - * Invoked from architecture specific syscall entry code with interrupts - * disabled. The calling code has to be non-instrumentable. When the - * function returns all state is correct and interrupts are still - * disabled. The subsequent functions can be instrumented. - * - * This is invoked when there is architecture specific functionality to be - * done between establishing state and enabling interrupts. The caller must - * enable interrupts before invoking syscall_enter_from_user_mode_work(). */ void enter_from_user_mode(struct pt_regs *regs); +#endif /** * kentry_syscall_begin - Prepare to invoke a syscall handler @@ -261,25 +250,14 @@ static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step) } #endif +#ifdef CONFIG_ARM64 /** * 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. - * The caller has to invoke syscall_exit_to_user_mode_work() before this. + * Does the latter part of irqentry_exit_to_user_mode(). Only used by arm64. */ void exit_to_user_mode(void); +#endif /** * kentry_syscall_end - Finish syscall processing diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 800ad406431b..4ba82c684189 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -25,10 +25,12 @@ static __always_inline void __enter_from_user_mode(struct pt_regs *regs) instrumentation_end(); } +#ifdef CONFIG_ARM64 void noinstr enter_from_user_mode(struct pt_regs *regs) { __enter_from_user_mode(regs); } +#endif static inline void syscall_enter_audit(struct pt_regs *regs, long syscall) { @@ -106,10 +108,12 @@ static __always_inline void __exit_to_user_mode(void) lockdep_hardirqs_on(CALLER_ADDR0); } +#ifdef CONFIG_ARM64 void noinstr exit_to_user_mode(void) { __exit_to_user_mode(); } +#endif /* Workaround to allow gradual conversion of architecture code */ void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { } -- 2.29.2
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