From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Date: Fri, 8 Nov 2019 15:27:45 -0500
Subject: ftrace: Add another example of register_ftrace_direct() use case
Patch-mainline: v5.5-rc1
Git-commit: 156473a0ff4f9c209114b4c3ad968099eb541e33
References: bsc#1177028

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>
Acked-by: Gary Lin <glin@suse.com>
---
 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

--- 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
--- /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");