Commit e1067a07 authored by Jiri Olsa's avatar Jiri Olsa Committed by Steven Rostedt (VMware)
Browse files

ftrace/samples: Add module to test multi direct modify interface 

Adding ftrace-direct-multi-modify.ko kernel module that uses
modify_ftrace_direct_multi API. The core functionality is taken
from ftrace-direct-modify.ko kernel module and changed to fit
multi direct interface.

The init function creates kthread that periodically calls
modify_ftrace_direct_multi to change the trampoline address
for the direct ftrace_ops. The ftrace trace_pipe then shows
trace from both trampolines.

Link: https://lkml.kernel.org/r/20211206182032.87248-4-jolsa@kernel.org



Cc: Ingo Molnar <mingo@redhat.com>
Reviewed-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Tested-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent fea3ffa4

samples/ftrace/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct.o 
obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-too.o

obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-modify.o

obj-$(CONFIG_SAMPLE_FTRACE_DIRECT_MULTI) += ftrace-direct-multi.o

obj-$(CONFIG_SAMPLE_FTRACE_DIRECT_MULTI) += ftrace-direct-multi-modify.o



CFLAGS_sample-trace-array.o := -I$(src)

obj-$(CONFIG_SAMPLE_TRACE_ARRAY) += sample-trace-array.o

samples/ftrace/ftrace-direct-multi-modify.c

0 → 100644
+152 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0-only

#include <linux/module.h>

#include <linux/kthread.h>

#include <linux/ftrace.h>

#include <asm/asm-offsets.h>



void my_direct_func1(unsigned long ip)

{

	trace_printk("my direct func1 ip %lx\n", ip);

}



void my_direct_func2(unsigned long ip)

{

	trace_printk("my direct func2 ip %lx\n", ip);

}



extern void my_tramp1(void *);

extern void my_tramp2(void *);



#ifdef CONFIG_X86_64



asm (

"	.pushsection    .text, \"ax\", @progbits\n"

"	.type		my_tramp1, @function\n"

"	.globl		my_tramp1\n"

"   my_tramp1:"

"	pushq %rbp\n"

"	movq %rsp, %rbp\n"

"	pushq %rdi\n"

"	movq 8(%rbp), %rdi\n"

"	call my_direct_func1\n"

"	popq %rdi\n"

"	leave\n"

"	ret\n"

"	.size		my_tramp1, .-my_tramp1\n"

"	.type		my_tramp2, @function\n"

"\n"

"	.globl		my_tramp2\n"

"   my_tramp2:"

"	pushq %rbp\n"

"	movq %rsp, %rbp\n"

"	pushq %rdi\n"

"	movq 8(%rbp), %rdi\n"

"	call my_direct_func2\n"

"	popq %rdi\n"

"	leave\n"

"	ret\n"

"	.size		my_tramp2, .-my_tramp2\n"

"	.popsection\n"

);



#endif /* CONFIG_X86_64 */



#ifdef CONFIG_S390



asm (

"       .pushsection    .text, \"ax\", @progbits\n"

"       .type           my_tramp1, @function\n"

"       .globl          my_tramp1\n"

"   my_tramp1:"

"       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"

"       lgr             %r2,%r0\n"

"       brasl           %r14,my_direct_func1\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_tramp1, .-my_tramp1\n"

"\n"

"       .type           my_tramp2, @function\n"

"       .globl          my_tramp2\n"

"   my_tramp2:"

"       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"

"       lgr             %r2,%r0\n"

"       brasl           %r14,my_direct_func2\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_tramp2, .-my_tramp2\n"

"       .popsection\n"

);



#endif /* CONFIG_S390 */



static unsigned long my_tramp = (unsigned long)my_tramp1;

static unsigned long tramps[2] = {

	(unsigned long)my_tramp1,

	(unsigned long)my_tramp2,

};



static struct ftrace_ops direct;



static int simple_thread(void *arg)

{

	static int t;

	int ret = 0;



	while (!kthread_should_stop()) {

		set_current_state(TASK_INTERRUPTIBLE);

		schedule_timeout(2 * HZ);



		if (ret)

			continue;

		t ^= 1;

		ret = modify_ftrace_direct_multi(&direct, tramps[t]);

		if (!ret)

			my_tramp = tramps[t];

		WARN_ON_ONCE(ret);

	}



	return 0;

}



static struct task_struct *simple_tsk;



static int __init ftrace_direct_multi_init(void)

{

	int ret;



	ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);

	ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);



	ret = register_ftrace_direct_multi(&direct, my_tramp);



	if (!ret)

		simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");

	return ret;

}



static void __exit ftrace_direct_multi_exit(void)

{

	kthread_stop(simple_tsk);

	unregister_ftrace_direct_multi(&direct, my_tramp);

}



module_init(ftrace_direct_multi_init);

module_exit(ftrace_direct_multi_exit);



MODULE_AUTHOR("Jiri Olsa");

MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");

MODULE_LICENSE("GPL");