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    SubjectRe: [RFC PATCH v2 10/18] livepatch/powerpc: add TIF_PATCH_PENDING thread flag
    On Thu 2016-04-28 15:44:41, Josh Poimboeuf wrote:
    > Add the TIF_PATCH_PENDING thread flag to enable the new livepatch
    > per-task consistency model for powerpc. The bit getting set indicates
    > the thread has a pending patch which needs to be applied when the thread
    > exits the kernel.
    >
    > The bit is included in the _TIF_USER_WORK_MASK macro so that
    > do_notify_resume() and klp_patch_task() get called when the bit is set.
    >
    > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
    > ---
    > arch/powerpc/include/asm/thread_info.h | 4 +++-
    > arch/powerpc/kernel/signal.c | 4 ++++
    > 2 files changed, 7 insertions(+), 1 deletion(-)
    >
    > diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
    > index 8febc3f..df262ca 100644
    > --- a/arch/powerpc/include/asm/thread_info.h
    > +++ b/arch/powerpc/include/asm/thread_info.h
    > @@ -88,6 +88,7 @@ static inline struct thread_info *current_thread_info(void)
    > TIF_NEED_RESCHED */
    > #define TIF_32BIT 4 /* 32 bit binary */
    > #define TIF_RESTORE_TM 5 /* need to restore TM FP/VEC/VSX */
    > +#define TIF_PATCH_PENDING 6 /* pending live patching update */
    > #define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
    > #define TIF_SINGLESTEP 8 /* singlestepping active */
    > #define TIF_NOHZ 9 /* in adaptive nohz mode */
    > @@ -111,6 +112,7 @@ static inline struct thread_info *current_thread_info(void)
    > #define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)
    > #define _TIF_32BIT (1<<TIF_32BIT)
    > #define _TIF_RESTORE_TM (1<<TIF_RESTORE_TM)
    > +#define _TIF_PATCH_PENDING (1<<TIF_PATCH_PENDING)
    > #define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
    > #define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
    > #define _TIF_SECCOMP (1<<TIF_SECCOMP)
    > @@ -127,7 +129,7 @@ static inline struct thread_info *current_thread_info(void)
    >
    > #define _TIF_USER_WORK_MASK (_TIF_SIGPENDING | _TIF_NEED_RESCHED | \
    > _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
    > - _TIF_RESTORE_TM)
    > + _TIF_RESTORE_TM | _TIF_PATCH_PENDING)
    > #define _TIF_PERSYSCALL_MASK (_TIF_RESTOREALL|_TIF_NOERROR)
    >
    > /* Bits in local_flags */
    > diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
    > index cb64d6f..844497b 100644
    > --- a/arch/powerpc/kernel/signal.c
    > +++ b/arch/powerpc/kernel/signal.c
    > @@ -14,6 +14,7 @@
    > #include <linux/uprobes.h>
    > #include <linux/key.h>
    > #include <linux/context_tracking.h>
    > +#include <linux/livepatch.h>
    > #include <asm/hw_breakpoint.h>
    > #include <asm/uaccess.h>
    > #include <asm/unistd.h>
    > @@ -159,6 +160,9 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
    > tracehook_notify_resume(regs);
    > }
    >
    > + if (thread_info_flags & _TIF_PATCH_PENDING)
    > + klp_patch_task(current);
    > +

    JFYI, if we later add the fake signal to speed up migration of
    sleeping task, we would need to move this up before calling
    do_signal(). It would help to avoid cycling here twice.
    Mirek surely knows more details about it.

    Best Regards,
    Petr

    > user_enter();
    > }
    >
    > --
    > 2.4.11
    >

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