Messages in this thread Patch in this message | | | From | Jiri Olsa <> | Subject | [PATCH 3/3] ftrace/samples: Add module to test multi direct modify interface | Date | Mon, 6 Dec 2021 00:20:36 +0100 |
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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.
Also adding SAMPLE_FTRACE_MULTI_DIRECT to enable build of direct multi interface sample modules. It's used in Makefile, but not defined at the moment.
Same as for ftrace-direct-multi.ko, the new module is enabled only for x86_64, so there's no need to ifdef the inlined assembly.
Signed-off-by: Jiri Olsa <jolsa@kernel.org> --- samples/Kconfig | 8 ++ samples/ftrace/Makefile | 1 + samples/ftrace/ftrace-direct-multi-modify.c | 105 ++++++++++++++++++++ 3 files changed, 114 insertions(+) create mode 100644 samples/ftrace/ftrace-direct-multi-modify.c
diff --git a/samples/Kconfig b/samples/Kconfig index bec3528aa2de..38daae5a06b5 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -31,6 +31,14 @@ config SAMPLE_FTRACE_DIRECT This builds an ftrace direct function example that hooks to wake_up_process and prints the parameters. +config SAMPLE_FTRACE_MULTI_DIRECT + tristate "Build register_ftrace_direct_multi() examples" + depends on DYNAMIC_FTRACE_WITH_DIRECT_CALLS && m + depends on HAVE_SAMPLE_FTRACE_MULTI_DIRECT + help + This builds an ftrace direct multi function examples + that hooks trampolines to multiple functions. + config SAMPLE_TRACE_ARRAY tristate "Build sample module for kernel access to Ftrace instancess" depends on EVENT_TRACING && m diff --git a/samples/ftrace/Makefile b/samples/ftrace/Makefile index e8a3f8520a44..027d375890f8 100644 --- a/samples/ftrace/Makefile +++ b/samples/ftrace/Makefile @@ -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_MULTI_DIRECT) += ftrace-direct-multi.o +obj-$(CONFIG_SAMPLE_FTRACE_MULTI_DIRECT) += ftrace-direct-multi-modify.o CFLAGS_sample-trace-array.o := -I$(src) obj-$(CONFIG_SAMPLE_TRACE_ARRAY) += sample-trace-array.o diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c new file mode 100644 index 000000000000..ba309cb33c77 --- /dev/null +++ b/samples/ftrace/ftrace-direct-multi-modify.c @@ -0,0 +1,105 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <linux/module.h> +#include <linux/kthread.h> +#include <linux/ftrace.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 *); + +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" +); + +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"); -- 2.33.1
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