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Subject[PATCH 7/7] Add kprobes smoke tests under tests/
From: Ananth N Mavinakayanahalli <ananth@in.ibm.com>

Here is a quick and naive smoke test for kprobes. This is intended to
just verify if some unrelated change broke the *probes subsystem. It is
self contained, architecture agnostic and isn't of any great use by itself.

This needs to be built in the kernel and runs a basic set of tests to
verify if kprobes, jprobes and kretprobes run fine on the kernel. In case
of an error, it'll print out a message with a "BUG" prefix.

This is a start; we intend to add more tests to this bucket over time.

Thanks to Jim Keniston and Masami Hiramatsu for comments and suggestions.

Tested on x86 (32/64) and powerpc.

PS: This can't be built as a module (yet), as noinline doesn't always
work reliably and I am yet to figure out a solution (non-varargs based),
so jprobes tests can work seamlessly.

Updated to live under tests/

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
---
include/linux/kprobes.h | 9 +
kernel/kprobes.c | 2
tests/Kconfig | 12 ++
tests/Makefile | 1
tests/test_kprobes.c | 218 ++++++++++++++++++++++++++++++++++++++++++++++++
5 files changed, 242 insertions(+)
Index: linux-2.6.24-rc6/tests/Kconfig
===================================================================
--- linux-2.6.24-rc6.orig/tests/Kconfig
+++ linux-2.6.24-rc6/tests/Kconfig
@@ -66,5 +66,17 @@ config LKDTM
Documentation on how to use the module can be found in
drivers/misc/lkdtm.c

+config KPROBES_SANITY_TEST
+ bool "Kprobes sanity tests"
+ depends on DEBUG_KERNEL
+ depends on KPROBES
+ default n
+ help
+ This option provides for testing basic kprobes functionality on
+ boot. A sample kprobe, jprobe and kretprobe are inserted and
+ verified for functionality.
+
+ Say N if you are unsure.
+
endif # KERNEL_TESTS

Index: linux-2.6.24-rc6/tests/Makefile
===================================================================
--- linux-2.6.24-rc6.orig/tests/Makefile
+++ linux-2.6.24-rc6/tests/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_RCU_TORTURE_TEST) += rcutor
obj-$(CONFIG_RT_MUTEX_TESTER) += rtmutex-tester.o
obj-$(CONFIG_DEBUG_SYNCHRO_TEST) += synchro-test.o
obj-$(CONFIG_LKDTM) += lkdtm.o
+obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
Index: linux-2.6.24-rc6/tests/test_kprobes.c
===================================================================
--- /dev/null
+++ linux-2.6.24-rc6/tests/test_kprobes.c
@@ -0,0 +1,218 @@
+/*
+ * test_kprobes.c - simple sanity test for *probes
+ *
+ * Copyright IBM Corp. 2008
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
+ * the GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/kprobes.h>
+#include <linux/random.h>
+
+#define div_factor 3
+
+static u32 rand1, preh_val, posth_val, jph_val;
+static int errors, handler_errors, num_tests;
+
+static noinline u32 kprobe_target(u32 value)
+{
+ /*
+ * gcc ignores noinline on some architectures unless we stuff
+ * sufficient lard into the function. The get_kprobe() here is
+ * just for that.
+ *
+ * NOTE: We aren't concerned about the correctness of get_kprobe()
+ * here; hence, this call is neither under !preempt nor with the
+ * kprobe_mutex held. This is fine(tm)
+ */
+ if (get_kprobe((void *)0xdeadbeef))
+ printk(KERN_INFO "Kprobe smoke test: probe on 0xdeadbeef!\n");
+
+ return (value / div_factor);
+}
+
+static int kp_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+ preh_val = (rand1 / div_factor);
+ return 0;
+}
+
+static void kp_post_handler(struct kprobe *p, struct pt_regs *regs,
+ unsigned long flags)
+{
+ if (preh_val != (rand1 / div_factor)) {
+ handler_errors++;
+ printk(KERN_ERR "Kprobe smoke test failed: "
+ "incorrect value in post_handler\n");
+ }
+ posth_val = preh_val + div_factor;
+}
+
+static struct kprobe kp = {
+ .symbol_name = "kprobe_target",
+ .pre_handler = kp_pre_handler,
+ .post_handler = kp_post_handler
+};
+
+static int test_kprobe(void)
+{
+ int ret;
+
+ ret = register_kprobe(&kp);
+ if (ret < 0) {
+ printk(KERN_ERR "Kprobe smoke test failed: "
+ "register_kprobe returned %d\n", ret);
+ return ret;
+ }
+
+ ret = kprobe_target(rand1);
+ unregister_kprobe(&kp);
+
+ if (preh_val == 0) {
+ printk(KERN_ERR "Kprobe smoke test failed: "
+ "kprobe pre_handler not called\n");
+ handler_errors++;
+ }
+
+ if (posth_val == 0) {
+ printk(KERN_ERR "Kprobe smoke test failed: "
+ "kprobe post_handler not called\n");
+ handler_errors++;
+ }
+
+ return 0;
+}
+
+static u32 j_kprobe_target(u32 value)
+{
+ if (value != rand1) {
+ handler_errors++;
+ printk(KERN_ERR "Kprobe smoke test failed: "
+ "incorrect value in jprobe handler\n");
+ }
+
+ jph_val = rand1;
+ jprobe_return();
+ return 0;
+}
+
+static struct jprobe jp = {
+ .entry = j_kprobe_target,
+ .kp.symbol_name = "kprobe_target"
+};
+
+static int test_jprobe(void)
+{
+ int ret;
+
+ ret = register_jprobe(&jp);
+ if (ret < 0) {
+ printk(KERN_ERR "Kprobe smoke test failed: "
+ "register_jprobe returned %d\n", ret);
+ return ret;
+ }
+
+ ret = kprobe_target(rand1);
+ unregister_jprobe(&jp);
+ if (jph_val == 0) {
+ /* Pre-handler was never called */
+ printk(KERN_ERR "Kprobe smoke test failed: "
+ "jprobe handler not called\n");
+ handler_errors++;
+ }
+
+ return 0;
+}
+
+#ifdef CONFIG_KRETPROBES
+static u32 krph_val;
+
+static int return_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+ unsigned long ret = regs_return_value(regs);
+
+ if (ret != (rand1 / div_factor)) {
+ handler_errors++;
+ printk(KERN_ERR "Kprobe smoke test failed: "
+ "incorrect value in kretprobe handler\n");
+ }
+
+ krph_val = (rand1 / div_factor);
+ return 0;
+}
+
+static struct kretprobe rp = {
+ .handler = return_handler,
+ .kp.symbol_name = "kprobe_target"
+};
+
+static int test_kretprobe(void)
+{
+ int ret;
+
+ ret = register_kretprobe(&rp);
+ if (ret < 0) {
+ printk(KERN_ERR "Kprobe smoke test failed: "
+ "register_kretprobe returned %d\n", ret);
+ return ret;
+ }
+
+ ret = kprobe_target(rand1);
+ unregister_kretprobe(&rp);
+ if (krph_val == 0) {
+ /* Pre-handler was never called */
+ printk(KERN_ERR "Kprobe smoke test failed: "
+ "kretprobe handler not called\n");
+ handler_errors++;
+ }
+
+ return 0;
+}
+#endif /* CONFIG_KRETPROBES */
+
+int init_test_probes(void)
+{
+ int ret;
+
+ do {
+ rand1 = random32();
+ } while (rand1 <= div_factor);
+
+ printk(KERN_INFO "Kprobe smoke test started\n");
+ num_tests++;
+ ret = test_kprobe();
+ if (ret < 0)
+ errors++;
+
+ num_tests++;
+ ret = test_jprobe();
+ if (ret < 0)
+ errors++;
+
+#ifdef CONFIG_KRETPROBES
+ num_tests++;
+ ret = test_kretprobe();
+ if (ret < 0)
+ errors++;
+#endif /* CONFIG_KRETPROBES */
+
+ if (errors)
+ printk(KERN_ERR "BUG: Kprobe smoke test: %d out of "
+ "%d tests failed\n", errors, num_tests);
+ else if (handler_errors)
+ printk(KERN_ERR "BUG: Kprobe smoke test: %d error(s) "
+ "running handlers\n", handler_errors);
+ else
+ printk(KERN_INFO "Kprobe smoke test passed successfully\n");
+
+ return 0;
+}
Index: linux-2.6.24-rc6/include/linux/kprobes.h
===================================================================
--- linux-2.6.24-rc6.orig/include/linux/kprobes.h
+++ linux-2.6.24-rc6/include/linux/kprobes.h
@@ -182,6 +182,15 @@ static inline void kretprobe_assert(stru
}
}

+#ifdef CONFIG_KPROBES_SANITY_TEST
+extern int init_test_probes(void);
+#else
+static inline int init_test_probes(void)
+{
+ return 0;
+}
+#endif /* CONFIG_KPROBES_SANITY_TEST */
+
extern spinlock_t kretprobe_lock;
extern struct mutex kprobe_mutex;
extern int arch_prepare_kprobe(struct kprobe *p);
Index: linux-2.6.24-rc6/kernel/kprobes.c
===================================================================
--- linux-2.6.24-rc6.orig/kernel/kprobes.c
+++ linux-2.6.24-rc6/kernel/kprobes.c
@@ -824,6 +824,8 @@ static int __init init_kprobes(void)
if (!err)
err = register_die_notifier(&kprobe_exceptions_nb);

+ if (!err)
+ init_test_probes();
return err;
}


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