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    Subject[for-next][PATCH 11/18] s390/function_graph: Simplify with function_graph_entry()
    From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

    The function_graph_entry() function does the work of calling the function
    graph hook function and the management of the shadow stack, simplifying the
    work done in the architecture dependent prepare_ftrace_return().

    Have s390 use the new code, and remove the shadow stack management as well as
    having to set up the trace structure.

    This is needed to prepare for a fix of a design bug on how the curr_ret_stack
    is used.

    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
    Cc: Julian Wiedmann <jwi@linux.ibm.com>
    Cc: linux-s390@vger.kernel.org
    Cc: stable@kernel.org
    Fixes: 03274a3ffb449 ("tracing/fgraph: Adjust fgraph depth before calling trace return callback")
    Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
    ---
    arch/s390/kernel/ftrace.c | 13 ++-----------
    1 file changed, 2 insertions(+), 11 deletions(-)

    diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
    index 84be7f02d0c2..39b13d71a8fe 100644
    --- a/arch/s390/kernel/ftrace.c
    +++ b/arch/s390/kernel/ftrace.c
    @@ -203,22 +203,13 @@ device_initcall(ftrace_plt_init);
    */
    unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
    {
    - struct ftrace_graph_ent trace;
    -
    if (unlikely(ftrace_graph_is_dead()))
    goto out;
    if (unlikely(atomic_read(&current->tracing_graph_pause)))
    goto out;
    ip -= MCOUNT_INSN_SIZE;
    - trace.func = ip;
    - trace.depth = current->curr_ret_stack + 1;
    - /* Only trace if the calling function expects to. */
    - if (!ftrace_graph_entry(&trace))
    - goto out;
    - if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
    - NULL) == -EBUSY)
    - goto out;
    - parent = (unsigned long) return_to_handler;
    + if (!function_graph_enter(parent, ip, 0, NULL))
    + parent = (unsigned long) return_to_handler;
    out:
    return parent;
    }
    --
    2.19.1

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