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Jiri Olsarostedt
Jiri Olsa
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rostedt
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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/[email protected] Cc: Ingo Molnar <[email protected]> Reviewed-by: Heiko Carstens <[email protected]> Tested-by: Heiko Carstens <[email protected]> Signed-off-by: Jiri Olsa <[email protected]> Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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‎samples/ftrace/Makefile

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@@ -4,6 +4,7 @@ obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct.o
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obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-too.o
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obj-$(CONFIG_SAMPLE_FTRACE_DIRECT) += ftrace-direct-modify.o
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obj-$(CONFIG_SAMPLE_FTRACE_DIRECT_MULTI) += ftrace-direct-multi.o
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obj-$(CONFIG_SAMPLE_FTRACE_DIRECT_MULTI) += ftrace-direct-multi-modify.o
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CFLAGS_sample-trace-array.o := -I$(src)
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obj-$(CONFIG_SAMPLE_TRACE_ARRAY) += sample-trace-array.o

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

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// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/module.h>
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#include <linux/kthread.h>
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#include <linux/ftrace.h>
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#include <asm/asm-offsets.h>
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void my_direct_func1(unsigned long ip)
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{
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trace_printk("my direct func1 ip %lx\n", ip);
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}
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void my_direct_func2(unsigned long ip)
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{
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trace_printk("my direct func2 ip %lx\n", ip);
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}
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extern void my_tramp1(void *);
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extern void my_tramp2(void *);
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#ifdef CONFIG_X86_64
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asm (
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" .pushsection .text, \"ax\", @progbits\n"
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" .type my_tramp1, @function\n"
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" .globl my_tramp1\n"
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" my_tramp1:"
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" pushq %rbp\n"
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" movq %rsp, %rbp\n"
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" pushq %rdi\n"
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" movq 8(%rbp), %rdi\n"
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" call my_direct_func1\n"
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" popq %rdi\n"
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" leave\n"
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" ret\n"
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" .size my_tramp1, .-my_tramp1\n"
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" .type my_tramp2, @function\n"
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"\n"
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" .globl my_tramp2\n"
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" my_tramp2:"
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" pushq %rbp\n"
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" movq %rsp, %rbp\n"
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" pushq %rdi\n"
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" movq 8(%rbp), %rdi\n"
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" call my_direct_func2\n"
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" popq %rdi\n"
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" leave\n"
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" ret\n"
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" .size my_tramp2, .-my_tramp2\n"
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" .popsection\n"
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);
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#endif /* CONFIG_X86_64 */
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#ifdef CONFIG_S390
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asm (
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" .pushsection .text, \"ax\", @progbits\n"
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" .type my_tramp1, @function\n"
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" .globl my_tramp1\n"
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" my_tramp1:"
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" lgr %r1,%r15\n"
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" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
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" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
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" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
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" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
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" lgr %r2,%r0\n"
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" brasl %r14,my_direct_func1\n"
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" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
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" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
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" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
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" lgr %r1,%r0\n"
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" br %r1\n"
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" .size my_tramp1, .-my_tramp1\n"
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"\n"
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" .type my_tramp2, @function\n"
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" .globl my_tramp2\n"
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" my_tramp2:"
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" lgr %r1,%r15\n"
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" stmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
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" stg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
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" aghi %r15,"__stringify(-STACK_FRAME_OVERHEAD)"\n"
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" stg %r1,"__stringify(__SF_BACKCHAIN)"(%r15)\n"
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" lgr %r2,%r0\n"
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" brasl %r14,my_direct_func2\n"
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" aghi %r15,"__stringify(STACK_FRAME_OVERHEAD)"\n"
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" lmg %r0,%r5,"__stringify(__SF_GPRS)"(%r15)\n"
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" lg %r14,"__stringify(__SF_GPRS+8*8)"(%r15)\n"
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" lgr %r1,%r0\n"
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" br %r1\n"
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" .size my_tramp2, .-my_tramp2\n"
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" .popsection\n"
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);
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#endif /* CONFIG_S390 */
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static unsigned long my_tramp = (unsigned long)my_tramp1;
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static unsigned long tramps[2] = {
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(unsigned long)my_tramp1,
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(unsigned long)my_tramp2,
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};
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static struct ftrace_ops direct;
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static int simple_thread(void *arg)
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{
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static int t;
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int ret = 0;
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while (!kthread_should_stop()) {
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set_current_state(TASK_INTERRUPTIBLE);
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schedule_timeout(2 * HZ);
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if (ret)
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continue;
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t ^= 1;
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ret = modify_ftrace_direct_multi(&direct, tramps[t]);
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if (!ret)
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my_tramp = tramps[t];
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WARN_ON_ONCE(ret);
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}
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return 0;
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}
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static struct task_struct *simple_tsk;
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static int __init ftrace_direct_multi_init(void)
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{
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int ret;
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ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0);
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ftrace_set_filter_ip(&direct, (unsigned long) schedule, 0, 0);
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ret = register_ftrace_direct_multi(&direct, my_tramp);
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if (!ret)
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simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn");
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return ret;
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}
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static void __exit ftrace_direct_multi_exit(void)
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{
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kthread_stop(simple_tsk);
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unregister_ftrace_direct_multi(&direct, my_tramp);
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}
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module_init(ftrace_direct_multi_init);
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module_exit(ftrace_direct_multi_exit);
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MODULE_AUTHOR("Jiri Olsa");
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MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()");
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MODULE_LICENSE("GPL");

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