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entry: Add exit_to_user_mode() wrapper

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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 <svens@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201201142755.31931-5-svens@linux.ibm.com
This commit is contained in:
Sven Schnelle 2020-12-01 15:27:54 +01:00 committed by Thomas Gleixner
parent 96e2fbccd0
commit 310de1a678
2 changed files with 27 additions and 14 deletions
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23
include/linux/entry-common.h
View File

@ -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);

18
kernel/entry/common.c
View File

@ -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) { }