[PATCH] test_kprobes: clear kprobes between test runs

[PATCH] test_kprobes: clear kprobes between test runs

[Martin Kaiser]

Running the kprobes sanity tests twice makes all tests fail and
eventually crashes the kernel.

[root@martin-riscv-1 ~]# echo 1 > /sys/kernel/debug/kunit/kprobes_test/run
...
   # Totals: pass:5 fail:0 skip:0 total:5
   ok 1 kprobes_test
[root@martin-riscv-1 ~]# echo 1 > /sys/kernel/debug/kunit/kprobes_test/run
...
  # test_kprobe: EXPECTATION FAILED at lib/tests/test_kprobes.c:64
  Expected 0 == register_kprobe(&kp), but
      register_kprobe(&kp) == -22 (0xffffffffffffffea)
...
  Unable to handle kernel paging request ...

The testsuite defines several kprobes and kretprobes as static variables
that are preserved across test runs.

After register_kprobe and unregister_kprobe, a kprobe contains some
leftover data that must be cleared before the kprobe can be registered
again. The tests are setting symbol_name to define the probe location.
Address and flags must be cleared.

The existing code clears some of the probes between subsequent tests, but
not between two test runs. The leftover data from a previous test run
makes the registrations fail in the next run.

Move the cleanups for all kprobes into kprobes_test_init, this function
is called before each single test (including the first test of a test
run).

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
---
 lib/tests/test_kprobes.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/lib/tests/test_kprobes.c b/lib/tests/test_kprobes.c
index b7582010125c..06e729e4de05 100644
--- a/lib/tests/test_kprobes.c
+++ b/lib/tests/test_kprobes.c
@@ -12,6 +12,12 @@
 
 #define div_factor 3
 
+#define KP_CLEAR(_kp) \
+do { \
+	(_kp).addr = NULL; \
+	(_kp).flags = 0; \
+} while (0)
+
 static u32 rand1, preh_val, posth_val;
 static u32 (*target)(u32 value);
 static u32 (*recursed_target)(u32 value);
@@ -125,10 +131,6 @@ static void test_kprobes(struct kunit *test)
 
 	current_test = test;
 
-	/* addr and flags should be cleard for reusing kprobe. */
-	kp.addr = NULL;
-	kp.flags = 0;
-
 	KUNIT_EXPECT_EQ(test, 0, register_kprobes(kps, 2));
 	preh_val = 0;
 	posth_val = 0;
@@ -226,9 +228,6 @@ static void test_kretprobes(struct kunit *test)
 	struct kretprobe *rps[2] = {&rp, &rp2};
 
 	current_test = test;
-	/* addr and flags should be cleard for reusing kprobe. */
-	rp.kp.addr = NULL;
-	rp.kp.flags = 0;
 	KUNIT_EXPECT_EQ(test, 0, register_kretprobes(rps, 2));
 
 	krph_val = 0;
@@ -290,8 +289,6 @@ static void test_stacktrace_on_kretprobe(struct kunit *test)
 	unsigned long myretaddr = (unsigned long)__builtin_return_address(0);
 
 	current_test = test;
-	rp3.kp.addr = NULL;
-	rp3.kp.flags = 0;
 
 	/*
 	 * Run the stacktrace_driver() to record correct return address in
@@ -352,8 +349,6 @@ static void test_stacktrace_on_nested_kretprobe(struct kunit *test)
 	struct kretprobe *rps[2] = {&rp3, &rp4};
 
 	current_test = test;
-	rp3.kp.addr = NULL;
-	rp3.kp.flags = 0;
 
 	//KUNIT_ASSERT_NE(test, myretaddr, stacktrace_driver());
 
@@ -367,6 +362,18 @@ static void test_stacktrace_on_nested_kretprobe(struct kunit *test)
 
 static int kprobes_test_init(struct kunit *test)
 {
+	KP_CLEAR(kp);
+	KP_CLEAR(kp2);
+	KP_CLEAR(kp_missed);
+#ifdef CONFIG_KRETPROBES
+	KP_CLEAR(rp.kp);
+	KP_CLEAR(rp2.kp);
+#ifdef CONFIG_ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
+	KP_CLEAR(rp3.kp);
+	KP_CLEAR(rp4.kp);
+#endif
+#endif
+
 	target = kprobe_target;
 	target2 = kprobe_target2;
 	recursed_target = kprobe_recursed_target;
-- 
2.43.7

Re: [PATCH] test_kprobes: clear kprobes between test runs

[Masami Hiramatsu]

On Thu,  7 May 2026 15:44:33 +0200
Martin Kaiser <martin@kaiser.cx> wrote:

> Running the kprobes sanity tests twice makes all tests fail and
> eventually crashes the kernel.
> 
> [root@martin-riscv-1 ~]# echo 1 > /sys/kernel/debug/kunit/kprobes_test/run
> ...
>    # Totals: pass:5 fail:0 skip:0 total:5
>    ok 1 kprobes_test
> [root@martin-riscv-1 ~]# echo 1 > /sys/kernel/debug/kunit/kprobes_test/run
> ...
>   # test_kprobe: EXPECTATION FAILED at lib/tests/test_kprobes.c:64
>   Expected 0 == register_kprobe(&kp), but
>       register_kprobe(&kp) == -22 (0xffffffffffffffea)
> ...
>   Unable to handle kernel paging request ...

Oops, good catch! Thanks for fixing!

> 
> The testsuite defines several kprobes and kretprobes as static variables
> that are preserved across test runs.
> 
> After register_kprobe and unregister_kprobe, a kprobe contains some
> leftover data that must be cleared before the kprobe can be registered
> again. The tests are setting symbol_name to define the probe location.
> Address and flags must be cleared.
> 
> The existing code clears some of the probes between subsequent tests, but
> not between two test runs. The leftover data from a previous test run
> makes the registrations fail in the next run.
> 
> Move the cleanups for all kprobes into kprobes_test_init, this function
> is called before each single test (including the first test of a test
> run).

Yeah, this looks good to me. Let me pick it.

> 
> Signed-off-by: Martin Kaiser <martin@kaiser.cx>
> ---
>  lib/tests/test_kprobes.c | 29 ++++++++++++++++++-----------
>  1 file changed, 18 insertions(+), 11 deletions(-)
> 
> diff --git a/lib/tests/test_kprobes.c b/lib/tests/test_kprobes.c
> index b7582010125c..06e729e4de05 100644
> --- a/lib/tests/test_kprobes.c
> +++ b/lib/tests/test_kprobes.c
> @@ -12,6 +12,12 @@
>  
>  #define div_factor 3
>  
> +#define KP_CLEAR(_kp) \
> +do { \
> +	(_kp).addr = NULL; \
> +	(_kp).flags = 0; \
> +} while (0)
> +
>  static u32 rand1, preh_val, posth_val;
>  static u32 (*target)(u32 value);
>  static u32 (*recursed_target)(u32 value);
> @@ -125,10 +131,6 @@ static void test_kprobes(struct kunit *test)
>  
>  	current_test = test;
>  
> -	/* addr and flags should be cleard for reusing kprobe. */
> -	kp.addr = NULL;
> -	kp.flags = 0;
> -
>  	KUNIT_EXPECT_EQ(test, 0, register_kprobes(kps, 2));
>  	preh_val = 0;
>  	posth_val = 0;
> @@ -226,9 +228,6 @@ static void test_kretprobes(struct kunit *test)
>  	struct kretprobe *rps[2] = {&rp, &rp2};
>  
>  	current_test = test;
> -	/* addr and flags should be cleard for reusing kprobe. */
> -	rp.kp.addr = NULL;
> -	rp.kp.flags = 0;
>  	KUNIT_EXPECT_EQ(test, 0, register_kretprobes(rps, 2));
>  
>  	krph_val = 0;
> @@ -290,8 +289,6 @@ static void test_stacktrace_on_kretprobe(struct kunit *test)
>  	unsigned long myretaddr = (unsigned long)__builtin_return_address(0);
>  
>  	current_test = test;
> -	rp3.kp.addr = NULL;
> -	rp3.kp.flags = 0;
>  
>  	/*
>  	 * Run the stacktrace_driver() to record correct return address in
> @@ -352,8 +349,6 @@ static void test_stacktrace_on_nested_kretprobe(struct kunit *test)
>  	struct kretprobe *rps[2] = {&rp3, &rp4};
>  
>  	current_test = test;
> -	rp3.kp.addr = NULL;
> -	rp3.kp.flags = 0;
>  
>  	//KUNIT_ASSERT_NE(test, myretaddr, stacktrace_driver());
>  
> @@ -367,6 +362,18 @@ static void test_stacktrace_on_nested_kretprobe(struct kunit *test)
>  
>  static int kprobes_test_init(struct kunit *test)
>  {
> +	KP_CLEAR(kp);
> +	KP_CLEAR(kp2);
> +	KP_CLEAR(kp_missed);
> +#ifdef CONFIG_KRETPROBES
> +	KP_CLEAR(rp.kp);
> +	KP_CLEAR(rp2.kp);
> +#ifdef CONFIG_ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
> +	KP_CLEAR(rp3.kp);
> +	KP_CLEAR(rp4.kp);
> +#endif
> +#endif
> +
>  	target = kprobe_target;
>  	target2 = kprobe_target2;
>  	recursed_target = kprobe_recursed_target;
> -- 
> 2.43.7
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>