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    Subject[tip: core/entry] tracepoints: Migrate to use SYSCALL_WORK flag
    The following commit has been merged into the core/entry branch of tip:

    Commit-ID: 524666cb5de7c38a1925e7401a6e59d68682dd8c
    Gitweb: https://git.kernel.org/tip/524666cb5de7c38a1925e7401a6e59d68682dd8c
    Author: Gabriel Krisman Bertazi <krisman@collabora.com>
    AuthorDate: Mon, 16 Nov 2020 12:42:01 -05:00
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitterDate: Mon, 16 Nov 2020 21:53:15 +01:00

    tracepoints: Migrate to use SYSCALL_WORK flag

    On architectures using the generic syscall entry code the architecture
    independent syscall work is moved to flags in thread_info::syscall_work.
    This removes architecture dependencies and frees up TIF bits.

    Define SYSCALL_WORK_SYSCALL_TRACEPOINT, use it in the generic entry code
    and convert the code which uses the TIF specific helper functions to use
    the new *_syscall_work() helpers which either resolve to the new mode for
    users of the generic entry code or to the TIF based functions for the other
    architectures.

    Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Andy Lutomirski <luto@kernel.org>
    Link: https://lore.kernel.org/r/20201116174206.2639648-6-krisman@collabora.com
    ---
    include/linux/entry-common.h | 13 +++++--------
    include/linux/thread_info.h | 2 ++
    include/trace/syscall.h | 6 +++---
    kernel/entry/common.c | 4 ++--
    kernel/trace/trace_events.c | 8 ++++----
    kernel/tracepoint.c | 4 ++--
    6 files changed, 18 insertions(+), 19 deletions(-)

    diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
    index fa3cdb1..2a01eee 100644
    --- a/include/linux/entry-common.h
    +++ b/include/linux/entry-common.h
    @@ -17,10 +17,6 @@
    # define _TIF_SYSCALL_EMU (0)
    #endif

    -#ifndef _TIF_SYSCALL_TRACEPOINT
    -# define _TIF_SYSCALL_TRACEPOINT (0)
    -#endif
    -
    #ifndef _TIF_SYSCALL_AUDIT
    # define _TIF_SYSCALL_AUDIT (0)
    #endif
    @@ -46,7 +42,7 @@

    #define SYSCALL_ENTER_WORK \
    (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
    - _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_EMU | \
    + _TIF_SYSCALL_EMU | \
    ARCH_SYSCALL_ENTER_WORK)

    /*
    @@ -58,10 +54,11 @@

    #define SYSCALL_EXIT_WORK \
    (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
    - _TIF_SYSCALL_TRACEPOINT | ARCH_SYSCALL_EXIT_WORK)
    + ARCH_SYSCALL_EXIT_WORK)

    -#define SYSCALL_WORK_ENTER (SYSCALL_WORK_SECCOMP)
    -#define SYSCALL_WORK_EXIT (0)
    +#define SYSCALL_WORK_ENTER (SYSCALL_WORK_SECCOMP | \
    + SYSCALL_WORK_SYSCALL_TRACEPOINT)
    +#define SYSCALL_WORK_EXIT (SYSCALL_WORK_SYSCALL_TRACEPOINT)

    /*
    * TIF flags handled in exit_to_user_mode_loop()
    diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
    index a308ba4..c232043 100644
    --- a/include/linux/thread_info.h
    +++ b/include/linux/thread_info.h
    @@ -37,9 +37,11 @@ enum {

    enum syscall_work_bit {
    SYSCALL_WORK_BIT_SECCOMP,
    + SYSCALL_WORK_BIT_SYSCALL_TRACEPOINT,
    };

    #define SYSCALL_WORK_SECCOMP BIT(SYSCALL_WORK_BIT_SECCOMP)
    +#define SYSCALL_WORK_SYSCALL_TRACEPOINT BIT(SYSCALL_WORK_BIT_SYSCALL_TRACEPOINT)

    #include <asm/thread_info.h>

    diff --git a/include/trace/syscall.h b/include/trace/syscall.h
    index dc8ac27..8e193f3 100644
    --- a/include/trace/syscall.h
    +++ b/include/trace/syscall.h
    @@ -37,10 +37,10 @@ struct syscall_metadata {
    #if defined(CONFIG_TRACEPOINTS) && defined(CONFIG_HAVE_SYSCALL_TRACEPOINTS)
    static inline void syscall_tracepoint_update(struct task_struct *p)
    {
    - if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
    - set_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT);
    + if (test_syscall_work(SYSCALL_TRACEPOINT))
    + set_task_syscall_work(p, SYSCALL_TRACEPOINT);
    else
    - clear_tsk_thread_flag(p, TIF_SYSCALL_TRACEPOINT);
    + clear_task_syscall_work(p, SYSCALL_TRACEPOINT);
    }
    #else
    static inline void syscall_tracepoint_update(struct task_struct *p)
    diff --git a/kernel/entry/common.c b/kernel/entry/common.c
    index 5747a6e..f651967 100644
    --- a/kernel/entry/common.c
    +++ b/kernel/entry/common.c
    @@ -63,7 +63,7 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall,
    /* Either of the above might have changed the syscall number */
    syscall = syscall_get_nr(current, regs);

    - if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
    + if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
    trace_sys_enter(regs, syscall);

    syscall_enter_audit(regs, syscall);
    @@ -233,7 +233,7 @@ static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work,

    audit_syscall_exit(regs);

    - if (ti_work & _TIF_SYSCALL_TRACEPOINT)
    + if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
    trace_sys_exit(regs, syscall_get_return_value(current, regs));

    step = report_single_step(ti_work);
    diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
    index 47a71f9..adf65b5 100644
    --- a/kernel/trace/trace_events.c
    +++ b/kernel/trace/trace_events.c
    @@ -3428,10 +3428,10 @@ static __init int event_trace_enable(void)
    * initialize events and perhaps start any events that are on the
    * command line. Unfortunately, there are some events that will not
    * start this early, like the system call tracepoints that need
    - * to set the TIF_SYSCALL_TRACEPOINT flag of pid 1. But event_trace_enable()
    - * is called before pid 1 starts, and this flag is never set, making
    - * the syscall tracepoint never get reached, but the event is enabled
    - * regardless (and not doing anything).
    + * to set the %SYSCALL_WORK_SYSCALL_TRACEPOINT flag of pid 1. But
    + * event_trace_enable() is called before pid 1 starts, and this flag
    + * is never set, making the syscall tracepoint never get reached, but
    + * the event is enabled regardless (and not doing anything).
    */
    static __init int event_trace_enable_again(void)
    {
    diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
    index 3f659f8..7261fa0 100644
    --- a/kernel/tracepoint.c
    +++ b/kernel/tracepoint.c
    @@ -594,7 +594,7 @@ int syscall_regfunc(void)
    if (!sys_tracepoint_refcount) {
    read_lock(&tasklist_lock);
    for_each_process_thread(p, t) {
    - set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
    + set_task_syscall_work(t, SYSCALL_TRACEPOINT);
    }
    read_unlock(&tasklist_lock);
    }
    @@ -611,7 +611,7 @@ void syscall_unregfunc(void)
    if (!sys_tracepoint_refcount) {
    read_lock(&tasklist_lock);
    for_each_process_thread(p, t) {
    - clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
    + clear_task_syscall_work(t, SYSCALL_TRACEPOINT);
    }
    read_unlock(&tasklist_lock);
    }
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