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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/20211206182032.87248-4-jolsa@kernel.org Cc: Ingo Molnar <mingo@redhat.com> Reviewed-by: Heiko Carstens <hca@linux.ibm.com> Tested-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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// SPDX-License-Identifier: GPL-2.0-only | ||
#include <linux/module.h> | ||
#include <linux/kthread.h> | ||
#include <linux/ftrace.h> | ||
#include <asm/asm-offsets.h> | ||
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void my_direct_func1(unsigned long ip) | ||
{ | ||
trace_printk("my direct func1 ip %lx\n", ip); | ||
} | ||
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void my_direct_func2(unsigned long ip) | ||
{ | ||
trace_printk("my direct func2 ip %lx\n", ip); | ||
} | ||
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extern void my_tramp1(void *); | ||
extern void my_tramp2(void *); | ||
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#ifdef CONFIG_X86_64 | ||
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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" | ||
); | ||
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#endif /* CONFIG_X86_64 */ | ||
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#ifdef CONFIG_S390 | ||
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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" | ||
); | ||
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#endif /* CONFIG_S390 */ | ||
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static unsigned long my_tramp = (unsigned long)my_tramp1; | ||
static unsigned long tramps[2] = { | ||
(unsigned long)my_tramp1, | ||
(unsigned long)my_tramp2, | ||
}; | ||
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static struct ftrace_ops direct; | ||
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static int simple_thread(void *arg) | ||
{ | ||
static int t; | ||
int ret = 0; | ||
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while (!kthread_should_stop()) { | ||
set_current_state(TASK_INTERRUPTIBLE); | ||
schedule_timeout(2 * HZ); | ||
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if (ret) | ||
continue; | ||
t ^= 1; | ||
ret = modify_ftrace_direct_multi(&direct, tramps[t]); | ||
if (!ret) | ||
my_tramp = tramps[t]; | ||
WARN_ON_ONCE(ret); | ||
} | ||
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return 0; | ||
} | ||
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static struct task_struct *simple_tsk; | ||
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static int __init ftrace_direct_multi_init(void) | ||
{ | ||
int ret; | ||
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ftrace_set_filter_ip(&direct, (unsigned long) wake_up_process, 0, 0); | ||
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) | ||
simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); | ||
return ret; | ||
} | ||
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static void __exit ftrace_direct_multi_exit(void) | ||
{ | ||
kthread_stop(simple_tsk); | ||
unregister_ftrace_direct_multi(&direct, my_tramp); | ||
} | ||
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module_init(ftrace_direct_multi_init); | ||
module_exit(ftrace_direct_multi_exit); | ||
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MODULE_AUTHOR("Jiri Olsa"); | ||
MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct_multi()"); | ||
MODULE_LICENSE("GPL"); |