1 files changed, 132 insertions, 0 deletions
diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
new file mode 100644
index 0000000000..32c477da1e
--- /dev/null
+++ b/samples/ftrace/ftrace-direct.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/module.h>
+
+#include <linux/sched.h> /* for wake_up_process() */
+#include <linux/ftrace.h>
+#ifndef CONFIG_ARM64
+#include <asm/asm-offsets.h>
+#endif
+
+extern void my_direct_func(struct task_struct *p);
+
+void my_direct_func(struct task_struct *p)
+{
+	trace_printk("waking up %s-%d\n", p->comm, p->pid);
+}
+
+extern void my_tramp(void *);
+
+#ifdef CONFIG_X86_64
+
+#include <asm/ibt.h>
+#include <asm/nospec-branch.h>
+
+asm (
+"	.pushsection    .text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
+"	.globl		my_tramp\n"
+"   my_tramp:"
+	ASM_ENDBR
+"	pushq %rbp\n"
+"	movq %rsp, %rbp\n"
+	CALL_DEPTH_ACCOUNT
+"	pushq %rdi\n"
+"	call my_direct_func\n"
+"	popq %rdi\n"
+"	leave\n"
+	ASM_RET
+"	.size		my_tramp, .-my_tramp\n"
+"	.popsection\n"
+);
+
+#endif /* CONFIG_X86_64 */
+
+#ifdef CONFIG_S390
+
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
+"	.globl		my_tramp\n"
+"   my_tramp:"
+"	lgr		%r1,%r15\n"
+"	stmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
+"	stg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
+"	aghi		%r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
+"	stg		%r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
+"	brasl		%r14,my_direct_func\n"
+"	aghi		%r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
+"	lmg		%r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
+"	lg		%r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
+"	lgr		%r1,%r0\n"
+"	br		%r1\n"
+"	.size		my_tramp, .-my_tramp\n"
+"	.popsection\n"
+);
+
+#endif /* CONFIG_S390 */
+
+#ifdef CONFIG_ARM64
+
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
+"	.globl		my_tramp\n"
+"   my_tramp:"
+"	hint	34\n" // bti	c
+"	sub	sp, sp, #32\n"
+"	stp	x9, x30, [sp]\n"
+"	str	x0, [sp, #16]\n"
+"	bl	my_direct_func\n"
+"	ldp	x30, x9, [sp]\n"
+"	ldr	x0, [sp, #16]\n"
+"	add	sp, sp, #32\n"
+"	ret	x9\n"
+"	.size		my_tramp, .-my_tramp\n"
+"	.popsection\n"
+);
+
+#endif /* CONFIG_ARM64 */
+
+#ifdef CONFIG_LOONGARCH
+
+asm (
+"	.pushsection	.text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
+"	.globl		my_tramp\n"
+"   my_tramp:\n"
+"	addi.d	$sp, $sp, -32\n"
+"	st.d	$a0, $sp, 0\n"
+"	st.d	$t0, $sp, 8\n"
+"	st.d	$ra, $sp, 16\n"
+"	bl	my_direct_func\n"
+"	ld.d	$a0, $sp, 0\n"
+"	ld.d	$t0, $sp, 8\n"
+"	ld.d	$ra, $sp, 16\n"
+"	addi.d	$sp, $sp, 32\n"
+"	jr	$t0\n"
+"	.size		my_tramp, .-my_tramp\n"
+"	.popsection\n"
+);
+
+#endif /* CONFIG_LOONGARCH */
+
+static struct ftrace_ops direct;
+
+static int __init ftrace_direct_init(void)
+{
+	ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
+
+	return register_ftrace_direct(&direct, (unsigned long) my_tramp);
+}
+
+static void __exit ftrace_direct_exit(void)
+{
+	unregister_ftrace_direct(&direct, (unsigned long)my_tramp, true);
+}
+
+module_init(ftrace_direct_init);
+module_exit(ftrace_direct_exit);
+
+MODULE_AUTHOR("Steven Rostedt");
+MODULE_DESCRIPTION("Example use case of using register_ftrace_direct()");
+MODULE_LICENSE("GPL");