kprobes: Add a test case for stacktrace from kretprobe handler

Add a test case for stacktrace from kretprobe handler and
nested kretprobe handlers.

This test checks both of stack trace inside kretprobe handler
and stack trace from pt_regs. Those stack trace must include
actual function return address instead of kretprobe trampoline.
The nested kretprobe stacktrace test checks whether the unwinder
can correctly unwind the call frame on the stack which has been
modified by the kretprobe.

Since the stacktrace on kretprobe is correctly fixed only on x86,
this introduces a meta kconfig ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
which tells user that the stacktrace on kretprobe is correct or not.

The test results will be shown like below;

 TAP version 14
 1..1
     # Subtest: kprobes_test
     1..6
     ok 1 - test_kprobe
     ok 2 - test_kprobes
     ok 3 - test_kretprobe
     ok 4 - test_kretprobes
     ok 5 - test_stacktrace_on_kretprobe
     ok 6 - test_stacktrace_on_nested_kretprobe
 # kprobes_test: pass:6 fail:0 skip:0 total:6
 # Totals: pass:6 fail:0 skip:0 total:6
 ok 1 - kprobes_test

Link: https://lkml.kernel.org/r/163516211244.604541.18350507860972214415.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/arch/Kconfig b/arch/Kconfig
index 8df1c71026435dfa4eb8e2d1978f7fd1bd5a7015..8378f83b462c0c5e330798fa440e0521a6d7f740 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -191,6 +191,14 @@ config HAVE_OPTPROBES
 config HAVE_KPROBES_ON_FTRACE
        bool
 
+config ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
+       bool
+       help
+         Since kretprobes modifies return address on the stack, the
+         stacktrace may see the kretprobe trampoline address instead
+         of correct one. If the architecture stacktrace code and
+         unwinder can adjust such entries, select this configuration.
+
 config HAVE_FUNCTION_ERROR_INJECTION
        bool
 

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index e39e2bd6acc532960d8bb4cfa9c6d5a1c6a514d4..cc9ba6798848a3be29323c4c564069a12f9c79b6 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -61,6 +61,7 @@ config X86
        select ACPI_SYSTEM_POWER_STATES_SUPPORT if ACPI
        select ARCH_32BIT_OFF_T                 if X86_32
        select ARCH_CLOCKSOURCE_INIT
+       select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
        select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE && MIGRATION
        select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64 || (X86_32 && HIGHMEM)
        select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG

diff --git a/kernel/test_kprobes.c b/kernel/test_kprobes.c
index e78f18144145937f8bbfb4d2b229a69ab9c4bf3c..a5edc2ebc947a6ba770065dc6e8dbe8e2688f7c2 100644 (file)
--- a/kernel/test_kprobes.c
+++ b/kernel/test_kprobes.c
@@ -17,6 +17,11 @@ static u32 (*target)(u32 value);
 static u32 (*target2)(u32 value);
 static struct kunit *current_test;
 
+static unsigned long (*internal_target)(void);
+static unsigned long (*stacktrace_target)(void);
+static unsigned long (*stacktrace_driver)(void);
+static unsigned long target_return_address[2];
+
 static noinline u32 kprobe_target(u32 value)
 {
        return (value / div_factor);
@@ -58,6 +63,33 @@ static noinline u32 kprobe_target2(u32 value)
        return (value / div_factor) + 1;
 }
 
+static noinline unsigned long kprobe_stacktrace_internal_target(void)
+{
+       if (!target_return_address[0])
+               target_return_address[0] = (unsigned long)__builtin_return_address(0);
+       return target_return_address[0];
+}
+
+static noinline unsigned long kprobe_stacktrace_target(void)
+{
+       if (!target_return_address[1])
+               target_return_address[1] = (unsigned long)__builtin_return_address(0);
+
+       if (internal_target)
+               internal_target();
+
+       return target_return_address[1];
+}
+
+static noinline unsigned long kprobe_stacktrace_driver(void)
+{
+       if (stacktrace_target)
+               stacktrace_target();
+
+       /* This is for preventing inlining the function */
+       return (unsigned long)__builtin_return_address(0);
+}
+
 static int kp_pre_handler2(struct kprobe *p, struct pt_regs *regs)
 {
        preh_val = (rand1 / div_factor) + 1;
@@ -175,12 +207,138 @@ static void test_kretprobes(struct kunit *test)
        KUNIT_EXPECT_EQ(test, krph_val, rand1);
        unregister_kretprobes(rps, 2);
 }
+
+#ifdef CONFIG_ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
+#define STACK_BUF_SIZE 16
+static unsigned long stack_buf[STACK_BUF_SIZE];
+
+static int stacktrace_return_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+       unsigned long retval = regs_return_value(regs);
+       int i, ret;
+
+       KUNIT_EXPECT_FALSE(current_test, preemptible());
+       KUNIT_EXPECT_EQ(current_test, retval, target_return_address[1]);
+
+       /*
+        * Test stacktrace inside the kretprobe handler, this will involves
+        * kretprobe trampoline, but must include correct return address
+        * of the target function.
+        */
+       ret = stack_trace_save(stack_buf, STACK_BUF_SIZE, 0);
+       KUNIT_EXPECT_NE(current_test, ret, 0);
+
+       for (i = 0; i < ret; i++) {
+               if (stack_buf[i] == target_return_address[1])
+                       break;
+       }
+       KUNIT_EXPECT_NE(current_test, i, ret);
+
+#if !IS_MODULE(CONFIG_KPROBES_SANITY_TEST)
+       /*
+        * Test stacktrace from pt_regs at the return address. Thus the stack
+        * trace must start from the target return address.
+        */
+       ret = stack_trace_save_regs(regs, stack_buf, STACK_BUF_SIZE, 0);
+       KUNIT_EXPECT_NE(current_test, ret, 0);
+       KUNIT_EXPECT_EQ(current_test, stack_buf[0], target_return_address[1]);
+#endif
+
+       return 0;
+}
+
+static struct kretprobe rp3 = {
+       .handler        = stacktrace_return_handler,
+       .kp.symbol_name = "kprobe_stacktrace_target"
+};
+
+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
+        * stacktrace_target() and ensure stacktrace_driver() call is not
+        * inlined by checking the return address of stacktrace_driver()
+        * and the return address of this function is different.
+        */
+       KUNIT_ASSERT_NE(test, myretaddr, stacktrace_driver());
+
+       KUNIT_ASSERT_EQ(test, 0, register_kretprobe(&rp3));
+       KUNIT_ASSERT_NE(test, myretaddr, stacktrace_driver());
+       unregister_kretprobe(&rp3);
+}
+
+static int stacktrace_internal_return_handler(struct kretprobe_instance *ri, struct pt_regs *regs)
+{
+       unsigned long retval = regs_return_value(regs);
+       int i, ret;
+
+       KUNIT_EXPECT_FALSE(current_test, preemptible());
+       KUNIT_EXPECT_EQ(current_test, retval, target_return_address[0]);
+
+       /*
+        * Test stacktrace inside the kretprobe handler for nested case.
+        * The unwinder will find the kretprobe_trampoline address on the
+        * return address, and kretprobe must solve that.
+        */
+       ret = stack_trace_save(stack_buf, STACK_BUF_SIZE, 0);
+       KUNIT_EXPECT_NE(current_test, ret, 0);
+
+       for (i = 0; i < ret - 1; i++) {
+               if (stack_buf[i] == target_return_address[0]) {
+                       KUNIT_EXPECT_EQ(current_test, stack_buf[i + 1], target_return_address[1]);
+                       break;
+               }
+       }
+       KUNIT_EXPECT_NE(current_test, i, ret);
+
+#if !IS_MODULE(CONFIG_KPROBES_SANITY_TEST)
+       /* Ditto for the regs version. */
+       ret = stack_trace_save_regs(regs, stack_buf, STACK_BUF_SIZE, 0);
+       KUNIT_EXPECT_NE(current_test, ret, 0);
+       KUNIT_EXPECT_EQ(current_test, stack_buf[0], target_return_address[0]);
+       KUNIT_EXPECT_EQ(current_test, stack_buf[1], target_return_address[1]);
+#endif
+
+       return 0;
+}
+
+static struct kretprobe rp4 = {
+       .handler        = stacktrace_internal_return_handler,
+       .kp.symbol_name = "kprobe_stacktrace_internal_target"
+};
+
+static void test_stacktrace_on_nested_kretprobe(struct kunit *test)
+{
+       unsigned long myretaddr = (unsigned long)__builtin_return_address(0);
+       struct kretprobe *rps[2] = {&rp3, &rp4};
+
+       current_test = test;
+       rp3.kp.addr = NULL;
+       rp3.kp.flags = 0;
+
+       //KUNIT_ASSERT_NE(test, myretaddr, stacktrace_driver());
+
+       KUNIT_ASSERT_EQ(test, 0, register_kretprobes(rps, 2));
+       KUNIT_ASSERT_NE(test, myretaddr, stacktrace_driver());
+       unregister_kretprobes(rps, 2);
+}
+#endif /* CONFIG_ARCH_CORRECT_STACKTRACE_ON_KRETPROBE */
+
 #endif /* CONFIG_KRETPROBES */
 
 static int kprobes_test_init(struct kunit *test)
 {
        target = kprobe_target;
        target2 = kprobe_target2;
+       stacktrace_target = kprobe_stacktrace_target;
+       internal_target = kprobe_stacktrace_internal_target;
+       stacktrace_driver = kprobe_stacktrace_driver;
 
        do {
                rand1 = prandom_u32();
@@ -194,6 +352,10 @@ static struct kunit_case kprobes_testcases[] = {
 #ifdef CONFIG_KRETPROBES
        KUNIT_CASE(test_kretprobe),
        KUNIT_CASE(test_kretprobes),
+#ifdef CONFIG_ARCH_CORRECT_STACKTRACE_ON_KRETPROBE
+       KUNIT_CASE(test_stacktrace_on_kretprobe),
+       KUNIT_CASE(test_stacktrace_on_nested_kretprobe),
+#endif
 #endif
        {}
 };