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Diffstat (limited to '')
| -rw-r--r-- | samples/ftrace/ftrace-direct-modify.c | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c new file mode 100644 index 000000000..39146fa83 --- /dev/null +++ b/samples/ftrace/ftrace-direct-modify.c @@ -0,0 +1,146 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <linux/module.h> +#include <linux/kthread.h> +#include <linux/ftrace.h> +#include <asm/asm-offsets.h> + +extern void my_direct_func1(void); +extern void my_direct_func2(void); + +void my_direct_func1(void) +{ + trace_printk("my direct func1\n"); +} + +void my_direct_func2(void) +{ + trace_printk("my direct func2\n"); +} + +extern void my_tramp1(void *); +extern void my_tramp2(void *); + +static unsigned long my_ip = (unsigned long)schedule; + +#ifdef CONFIG_X86_64 + +#include <asm/ibt.h> + +asm ( +" .pushsection .text, \"ax\", @progbits\n" +" .type my_tramp1, @function\n" +" .globl my_tramp1\n" +" my_tramp1:" + ASM_ENDBR +" pushq %rbp\n" +" movq %rsp, %rbp\n" +" call my_direct_func1\n" +" leave\n" +" .size my_tramp1, .-my_tramp1\n" + ASM_RET + +" .type my_tramp2, @function\n" +" .globl my_tramp2\n" +" my_tramp2:" + ASM_ENDBR +" pushq %rbp\n" +" movq %rsp, %rbp\n" +" call my_direct_func2\n" +" leave\n" + ASM_RET +" .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" +" 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" +" .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" +" 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 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(my_ip, my_tramp, 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_init(void) +{ + int ret; + + ret = register_ftrace_direct(my_ip, my_tramp); + if (!ret) + simple_tsk = kthread_run(simple_thread, NULL, "event-sample-fn"); + return ret; +} + +static void __exit ftrace_direct_exit(void) +{ + kthread_stop(simple_tsk); + unregister_ftrace_direct(my_ip, my_tramp); +} + +module_init(ftrace_direct_init); +module_exit(ftrace_direct_exit); + +MODULE_AUTHOR("Steven Rostedt"); +MODULE_DESCRIPTION("Example use case of using modify_ftrace_direct()"); +MODULE_LICENSE("GPL"); |