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-rw-r--r--samples/kprobes/Makefile6
-rw-r--r--samples/kprobes/kprobe_example.c128
-rw-r--r--samples/kprobes/kretprobe_example.c107
3 files changed, 241 insertions, 0 deletions
diff --git a/samples/kprobes/Makefile b/samples/kprobes/Makefile
new file mode 100644
index 0000000000..e774592718
--- /dev/null
+++ b/samples/kprobes/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# builds the kprobes example kernel modules;
+# then to use one (as root): insmod <module_name.ko>
+
+obj-$(CONFIG_SAMPLE_KPROBES) += kprobe_example.o
+obj-$(CONFIG_SAMPLE_KRETPROBES) += kretprobe_example.o
diff --git a/samples/kprobes/kprobe_example.c b/samples/kprobes/kprobe_example.c
new file mode 100644
index 0000000000..ef44c614c6
--- /dev/null
+++ b/samples/kprobes/kprobe_example.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Here's a sample kernel module showing the use of kprobes to dump a
+ * stack trace and selected registers when kernel_clone() is called.
+ *
+ * For more information on theory of operation of kprobes, see
+ * Documentation/trace/kprobes.rst
+ *
+ * You will see the trace data in /var/log/messages and on the console
+ * whenever kernel_clone() is invoked to create a new process.
+ */
+
+#define pr_fmt(fmt) "%s: " fmt, __func__
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/kprobes.h>
+
+static char symbol[KSYM_NAME_LEN] = "kernel_clone";
+module_param_string(symbol, symbol, KSYM_NAME_LEN, 0644);
+
+/* For each probe you need to allocate a kprobe structure */
+static struct kprobe kp = {
+ .symbol_name = symbol,
+};
+
+/* kprobe pre_handler: called just before the probed instruction is executed */
+static int __kprobes handler_pre(struct kprobe *p, struct pt_regs *regs)
+{
+#ifdef CONFIG_X86
+ pr_info("<%s> p->addr = 0x%p, ip = %lx, flags = 0x%lx\n",
+ p->symbol_name, p->addr, regs->ip, regs->flags);
+#endif
+#ifdef CONFIG_PPC
+ pr_info("<%s> p->addr = 0x%p, nip = 0x%lx, msr = 0x%lx\n",
+ p->symbol_name, p->addr, regs->nip, regs->msr);
+#endif
+#ifdef CONFIG_MIPS
+ pr_info("<%s> p->addr = 0x%p, epc = 0x%lx, status = 0x%lx\n",
+ p->symbol_name, p->addr, regs->cp0_epc, regs->cp0_status);
+#endif
+#ifdef CONFIG_ARM64
+ pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, pstate = 0x%lx\n",
+ p->symbol_name, p->addr, (long)regs->pc, (long)regs->pstate);
+#endif
+#ifdef CONFIG_ARM
+ pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, cpsr = 0x%lx\n",
+ p->symbol_name, p->addr, (long)regs->ARM_pc, (long)regs->ARM_cpsr);
+#endif
+#ifdef CONFIG_RISCV
+ pr_info("<%s> p->addr = 0x%p, pc = 0x%lx, status = 0x%lx\n",
+ p->symbol_name, p->addr, regs->epc, regs->status);
+#endif
+#ifdef CONFIG_S390
+ pr_info("<%s> p->addr, 0x%p, ip = 0x%lx, flags = 0x%lx\n",
+ p->symbol_name, p->addr, regs->psw.addr, regs->flags);
+#endif
+#ifdef CONFIG_LOONGARCH
+ pr_info("<%s> p->addr = 0x%p, era = 0x%lx, estat = 0x%lx\n",
+ p->symbol_name, p->addr, regs->csr_era, regs->csr_estat);
+#endif
+
+ /* A dump_stack() here will give a stack backtrace */
+ return 0;
+}
+
+/* kprobe post_handler: called after the probed instruction is executed */
+static void __kprobes handler_post(struct kprobe *p, struct pt_regs *regs,
+ unsigned long flags)
+{
+#ifdef CONFIG_X86
+ pr_info("<%s> p->addr = 0x%p, flags = 0x%lx\n",
+ p->symbol_name, p->addr, regs->flags);
+#endif
+#ifdef CONFIG_PPC
+ pr_info("<%s> p->addr = 0x%p, msr = 0x%lx\n",
+ p->symbol_name, p->addr, regs->msr);
+#endif
+#ifdef CONFIG_MIPS
+ pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n",
+ p->symbol_name, p->addr, regs->cp0_status);
+#endif
+#ifdef CONFIG_ARM64
+ pr_info("<%s> p->addr = 0x%p, pstate = 0x%lx\n",
+ p->symbol_name, p->addr, (long)regs->pstate);
+#endif
+#ifdef CONFIG_ARM
+ pr_info("<%s> p->addr = 0x%p, cpsr = 0x%lx\n",
+ p->symbol_name, p->addr, (long)regs->ARM_cpsr);
+#endif
+#ifdef CONFIG_RISCV
+ pr_info("<%s> p->addr = 0x%p, status = 0x%lx\n",
+ p->symbol_name, p->addr, regs->status);
+#endif
+#ifdef CONFIG_S390
+ pr_info("<%s> p->addr, 0x%p, flags = 0x%lx\n",
+ p->symbol_name, p->addr, regs->flags);
+#endif
+#ifdef CONFIG_LOONGARCH
+ pr_info("<%s> p->addr = 0x%p, estat = 0x%lx\n",
+ p->symbol_name, p->addr, regs->csr_estat);
+#endif
+}
+
+static int __init kprobe_init(void)
+{
+ int ret;
+ kp.pre_handler = handler_pre;
+ kp.post_handler = handler_post;
+
+ ret = register_kprobe(&kp);
+ if (ret < 0) {
+ pr_err("register_kprobe failed, returned %d\n", ret);
+ return ret;
+ }
+ pr_info("Planted kprobe at %p\n", kp.addr);
+ return 0;
+}
+
+static void __exit kprobe_exit(void)
+{
+ unregister_kprobe(&kp);
+ pr_info("kprobe at %p unregistered\n", kp.addr);
+}
+
+module_init(kprobe_init)
+module_exit(kprobe_exit)
+MODULE_LICENSE("GPL");
diff --git a/samples/kprobes/kretprobe_example.c b/samples/kprobes/kretprobe_example.c
new file mode 100644
index 0000000000..cbf16542d8
--- /dev/null
+++ b/samples/kprobes/kretprobe_example.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kretprobe_example.c
+ *
+ * Here's a sample kernel module showing the use of return probes to
+ * report the return value and total time taken for probed function
+ * to run.
+ *
+ * usage: insmod kretprobe_example.ko func=<func_name>
+ *
+ * If no func_name is specified, kernel_clone is instrumented
+ *
+ * For more information on theory of operation of kretprobes, see
+ * Documentation/trace/kprobes.rst
+ *
+ * Build and insert the kernel module as done in the kprobe example.
+ * You will see the trace data in /var/log/messages and on the console
+ * whenever the probed function returns. (Some messages may be suppressed
+ * if syslogd is configured to eliminate duplicate messages.)
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/kprobes.h>
+#include <linux/ktime.h>
+#include <linux/sched.h>
+
+static char func_name[KSYM_NAME_LEN] = "kernel_clone";
+module_param_string(func, func_name, KSYM_NAME_LEN, 0644);
+MODULE_PARM_DESC(func, "Function to kretprobe; this module will report the"
+ " function's execution time");
+
+/* per-instance private data */
+struct my_data {
+ ktime_t entry_stamp;
+};
+
+/* Here we use the entry_hanlder to timestamp function entry */
+static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+ struct my_data *data;
+
+ if (!current->mm)
+ return 1; /* Skip kernel threads */
+
+ data = (struct my_data *)ri->data;
+ data->entry_stamp = ktime_get();
+ return 0;
+}
+NOKPROBE_SYMBOL(entry_handler);
+
+/*
+ * Return-probe handler: Log the return value and duration. Duration may turn
+ * out to be zero consistently, depending upon the granularity of time
+ * accounting on the platform.
+ */
+static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+ unsigned long retval = regs_return_value(regs);
+ struct my_data *data = (struct my_data *)ri->data;
+ s64 delta;
+ ktime_t now;
+
+ now = ktime_get();
+ delta = ktime_to_ns(ktime_sub(now, data->entry_stamp));
+ pr_info("%s returned %lu and took %lld ns to execute\n",
+ func_name, retval, (long long)delta);
+ return 0;
+}
+NOKPROBE_SYMBOL(ret_handler);
+
+static struct kretprobe my_kretprobe = {
+ .handler = ret_handler,
+ .entry_handler = entry_handler,
+ .data_size = sizeof(struct my_data),
+ /* Probe up to 20 instances concurrently. */
+ .maxactive = 20,
+};
+
+static int __init kretprobe_init(void)
+{
+ int ret;
+
+ my_kretprobe.kp.symbol_name = func_name;
+ ret = register_kretprobe(&my_kretprobe);
+ if (ret < 0) {
+ pr_err("register_kretprobe failed, returned %d\n", ret);
+ return ret;
+ }
+ pr_info("Planted return probe at %s: %p\n",
+ my_kretprobe.kp.symbol_name, my_kretprobe.kp.addr);
+ return 0;
+}
+
+static void __exit kretprobe_exit(void)
+{
+ unregister_kretprobe(&my_kretprobe);
+ pr_info("kretprobe at %p unregistered\n", my_kretprobe.kp.addr);
+
+ /* nmissed > 0 suggests that maxactive was set too low. */
+ pr_info("Missed probing %d instances of %s\n",
+ my_kretprobe.nmissed, my_kretprobe.kp.symbol_name);
+}
+
+module_init(kretprobe_init)
+module_exit(kretprobe_exit)
+MODULE_LICENSE("GPL");