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    Subject[for-next][PATCH 10/33] ftrace: Add another example of register_ftrace_direct() use case
    From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

    Add another module sample that registers a direct trampoline to a function
    via register_ftrace_direct(). Having another module that does this allows to
    test the use case of multiple direct callers registered, as more than one
    direct caller goes into another path, and is needed to perform proper
    testing of the register_ftrace_direct() call.

    Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
    ---
    samples/ftrace/Makefile | 1 +
    samples/ftrace/ftrace-direct-too.c | 51 ++++++++++++++++++++++++++++++
    2 files changed, 52 insertions(+)
    create mode 100644 samples/ftrace/ftrace-direct-too.c

    diff --git a/samples/ftrace/Makefile b/samples/ftrace/Makefile
    index 3718ab39eba3..d8217c4e072e 100644
    --- a/samples/ftrace/Makefile
    +++ b/samples/ftrace/Makefile
    @@ -1,3 +1,4 @@
    # SPDX-License-Identifier: GPL-2.0-only

    obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct.o
    +obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-too.o
    diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
    new file mode 100644
    index 000000000000..27efa5f6ff52
    --- /dev/null
    +++ b/samples/ftrace/ftrace-direct-too.c
    @@ -0,0 +1,51 @@
    +// SPDX-License-Identifier: GPL-2.0-only
    +#include <linux/module.h>
    +
    +#include <linux/mm.h> /* for handle_mm_fault() */
    +#include <linux/ftrace.h>
    +
    +void my_direct_func(struct vm_area_struct *vma,
    + unsigned long address, unsigned int flags)
    +{
    + trace_printk("handle mm fault vma=%p address=%lx flags=%x\n",
    + vma, address, flags);
    +}
    +
    +extern void my_tramp(void *);
    +
    +asm (
    +" .pushsection .text, \"ax\", @progbits\n"
    +" my_tramp:"
    +" pushq %rbp\n"
    +" movq %rsp, %rbp\n"
    +" pushq %rdi\n"
    +" pushq %rsi\n"
    +" pushq %rdx\n"
    +" call my_direct_func\n"
    +" popq %rdx\n"
    +" popq %rsi\n"
    +" popq %rdi\n"
    +" leave\n"
    +" ret\n"
    +" .popsection\n"
    +);
    +
    +
    +static int __init ftrace_direct_init(void)
    +{
    + return register_ftrace_direct((unsigned long)handle_mm_fault,
    + (unsigned long)my_tramp);
    +}
    +
    +static void __exit ftrace_direct_exit(void)
    +{
    + unregister_ftrace_direct((unsigned long)handle_mm_fault,
    + (unsigned long)my_tramp);
    +}
    +
    +module_init(ftrace_direct_init);
    +module_exit(ftrace_direct_exit);
    +
    +MODULE_AUTHOR("Steven Rostedt");
    +MODULE_DESCRIPTION("Another example use case of using register_ftrace_direct()");
    +MODULE_LICENSE("GPL");
    --
    2.23.0

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