[RFC PATCH 14/14] samples/ftrace: Add powerpc support for ftrace direct samples

["Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>]

Add a simple powerpc trampoline to demonstrate use of ftrace direct on
powerpc.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
 samples/Kconfig                       |  2 +-
 samples/ftrace/ftrace-direct-modify.c | 58 +++++++++++++++++++++++++++
 samples/ftrace/ftrace-direct-too.c    | 48 ++++++++++++++++++++--
 samples/ftrace/ftrace-direct.c        | 45 +++++++++++++++++++--
 4 files changed, 144 insertions(+), 9 deletions(-)

diff --git a/samples/Kconfig b/samples/Kconfig
index 0ed6e4d71d87b1..fdc9e44dba3b95 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -26,7 +26,7 @@ config SAMPLE_TRACE_PRINTK
 config SAMPLE_FTRACE_DIRECT
 	tristate "Build register_ftrace_direct() example"
 	depends on DYNAMIC_FTRACE_WITH_DIRECT_CALLS && m
-	depends on X86_64 # has x86_64 inlined asm
+	depends on X86_64 || PPC64 # has inlined asm
 	help
 	  This builds an ftrace direct function example
 	  that hooks to wake_up_process and prints the parameters.
diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c
index c13a5bc5095bea..89d66a12d300e1 100644
--- a/samples/ftrace/ftrace-direct-modify.c
+++ b/samples/ftrace/ftrace-direct-modify.c
@@ -2,6 +2,7 @@
 #include <linux/module.h>
 #include <linux/kthread.h>
 #include <linux/ftrace.h>
+#include <linux/kprobes.h>
 
 void my_direct_func1(void)
 {
@@ -18,6 +19,7 @@ extern void my_tramp2(void *);
 
 static unsigned long my_ip = (unsigned long)schedule;
 
+#ifdef CONFIG_X86
 asm (
 "	.pushsection    .text, \"ax\", @progbits\n"
 "	.type		my_tramp1, @function\n"
@@ -38,6 +40,58 @@ asm (
 "	.size		my_tramp2, .-my_tramp2\n"
 "	.popsection\n"
 );
+#elif CONFIG_PPC64
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp1, @function\n"
+"	.global		my_tramp1\n"
+"   my_tramp1:\n"
+"	std	0, 16(1)\n"
+"	stdu	1, -480(1)\n"
+"	std	2, 24(1)\n"
+"	mflr	7\n"
+"	std	7, 368(1)\n"
+"	bcl	20, 31, 1f\n"
+"1:	mflr	12\n"
+"	ld	2, (3f - 1b)(12)\n"
+"	bl	my_direct_func1\n"
+"	nop\n"
+"	ld	2, 24(1)\n"
+"	ld	7, 368(1)\n"
+"	mtctr	7\n"
+"	addi	1, 1, 480\n"
+"	ld	0, 16(1)\n"
+"	mtlr	0\n"
+"	bctr\n"
+"	.size		my_tramp1, .-my_tramp1\n"
+"	nop\n"
+"	.type		my_tramp2, @function\n"
+"	.global		my_tramp2\n"
+"   my_tramp2:\n"
+"	std	0, 16(1)\n"
+"	stdu	1, -480(1)\n"
+"	std	2, 24(1)\n"
+"	mflr	7\n"
+"	std	7, 368(1)\n"
+"	bcl	20, 31, 2f\n"
+"2:	mflr	12\n"
+"	ld	2, (3f - 2b)(12)\n"
+"	bl	my_direct_func2\n"
+"	nop\n"
+"	ld	2, 24(1)\n"
+"	ld	7, 368(1)\n"
+"	mtctr	7\n"
+"	addi	1, 1, 480\n"
+"	ld	0, 16(1)\n"
+"	mtlr	0\n"
+"	bctr\n"
+"	.size		my_tramp2, .-my_tramp2\n"
+"3:\n"
+"	.quad		.TOC.@tocbase\n"
+"	.popsection\n"
+);
+#endif
+
 
 static unsigned long my_tramp = (unsigned long)my_tramp1;
 static unsigned long tramps[2] = {
@@ -72,6 +126,10 @@ static int __init ftrace_direct_init(void)
 {
 	int ret;
 
+#ifdef CONFIG_PPC64
+	my_ip = ppc_function_entry((void *)my_ip) + 4;
+#endif
+
 	ret = register_ftrace_direct(my_ip, my_tramp);
 	if (!ret)
 		simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
index d5c5022be66429..9a82abecbe0dcc 100644
--- a/samples/ftrace/ftrace-direct-too.c
+++ b/samples/ftrace/ftrace-direct-too.c
@@ -3,6 +3,7 @@
 
 #include <linux/mm.h> /* for handle_mm_fault() */
 #include <linux/ftrace.h>
+#include <linux/kprobes.h>
 
 void my_direct_func(struct vm_area_struct *vma,
 			unsigned long address, unsigned int flags)
@@ -13,6 +14,9 @@ void my_direct_func(struct vm_area_struct *vma,
 
 extern void my_tramp(void *);
 
+static unsigned long my_ip = (unsigned long)handle_mm_fault;
+
+#ifdef CONFIG_X86
 asm (
 "	.pushsection    .text, \"ax\", @progbits\n"
 "	.type		my_tramp, @function\n"
@@ -31,18 +35,54 @@ asm (
 "	.size		my_tramp, .-my_tramp\n"
 "	.popsection\n"
 );
+#elif CONFIG_PPC64
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
+"	.global		my_tramp\n"
+"   my_tramp:\n"
+"	std	0, 16(1)\n"
+"	stdu	1, -480(1)\n"
+"	std	2, 24(1)\n"
+"	std	3, 136(1)\n"
+"	std	4, 144(1)\n"
+"	std	5, 152(1)\n"
+"	mflr	7\n"
+"	std	7, 368(1)\n"
+"	bcl	20, 31, 1f\n"
+"1:	mflr	12\n"
+"	ld	2, (2f - 1b)(12)\n"
+"	bl	my_direct_func\n"
+"	nop\n"
+"	ld	5, 152(1)\n"
+"	ld	4, 144(1)\n"
+"	ld	3, 136(1)\n"
+"	ld	2, 24(1)\n"
+"	ld	7, 368(1)\n"
+"	mtctr	7\n"
+"	addi	1, 1, 480\n"
+"	ld	0, 16(1)\n"
+"	mtlr	0\n"
+"	bctr\n"
+"	.size		my_tramp, .-my_tramp\n"
+"2:\n"
+"	.quad		.TOC.@tocbase\n"
+"	.popsection\n"
+);
+#endif
 
 
 static int __init ftrace_direct_init(void)
 {
-	return register_ftrace_direct((unsigned long)handle_mm_fault,
-				     (unsigned long)my_tramp);
+#ifdef CONFIG_PPC64
+	my_ip = ppc_function_entry((void *)my_ip) + 4;
+#endif
+	return register_ftrace_direct(my_ip, (unsigned long)my_tramp);
 }
 
 static void __exit ftrace_direct_exit(void)
 {
-	unregister_ftrace_direct((unsigned long)handle_mm_fault,
-				 (unsigned long)my_tramp);
+	unregister_ftrace_direct(my_ip, (unsigned long)my_tramp);
 }
 
 module_init(ftrace_direct_init);
diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
index 63ca06d42c803f..da67b6217f91d2 100644
--- a/samples/ftrace/ftrace-direct.c
+++ b/samples/ftrace/ftrace-direct.c
@@ -3,6 +3,7 @@
 
 #include <linux/sched.h> /* for wake_up_process() */
 #include <linux/ftrace.h>
+#include <linux/kprobes.h> /* for ppc_function_entry() */
 
 void my_direct_func(struct task_struct *p)
 {
@@ -11,6 +12,9 @@ void my_direct_func(struct task_struct *p)
 
 extern void my_tramp(void *);
 
+static unsigned long my_ip = (unsigned long)wake_up_process;
+
+#ifdef CONFIG_X86
 asm (
 "	.pushsection    .text, \"ax\", @progbits\n"
 "	.type		my_tramp, @function\n"
@@ -25,18 +29,51 @@ asm (
 "	.size		my_tramp, .-my_tramp\n"
 "	.popsection\n"
 );
+#elif CONFIG_PPC64
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
+"	.global		my_tramp\n"
+"   my_tramp:\n"
+"	std	0, 16(1)\n"
+"	stdu	1, -480(1)\n"
+"	std	2, 24(1)\n"
+"	std	3, 136(1)\n"
+"	mflr	7\n"
+"	std	7, 368(1)\n"
+"	bcl	20, 31, 1f\n"
+"1:	mflr	12\n"
+"	ld	2, (2f - 1b)(12)\n"
+"	bl	my_direct_func\n"
+"	nop\n"
+"	ld	3, 136(1)\n"
+"	ld	2, 24(1)\n"
+"	ld	7, 368(1)\n"
+"	mtctr	7\n"
+"	addi	1, 1, 480\n"
+"	ld	0, 16(1)\n"
+"	mtlr	0\n"
+"	bctr\n"
+"	.size		my_tramp, .-my_tramp\n"
+"2:\n"
+"	.quad		.TOC.@tocbase\n"
+"	.popsection\n"
+);
+#endif
 
 
 static int __init ftrace_direct_init(void)
 {
-	return register_ftrace_direct((unsigned long)wake_up_process,
-				     (unsigned long)my_tramp);
+#ifdef CONFIG_PPC64
+	/* Ftrace location is (usually) the second instruction at a function's local entry point */
+	my_ip = ppc_function_entry((void *)my_ip) + 4;
+#endif
+	return register_ftrace_direct(my_ip, (unsigned long)my_tramp);
 }
 
 static void __exit ftrace_direct_exit(void)
 {
-	unregister_ftrace_direct((unsigned long)wake_up_process,
-				 (unsigned long)my_tramp);
+	unregister_ftrace_direct(my_ip, (unsigned long)my_tramp);
 }
 
 module_init(ftrace_direct_init);
-- 
2.25.4