From c570be0da77e963d77bac099d468bc0cd5f1bd63 Mon Sep 17 00:00:00 2001
From: Michael Jeanson <mjeanson@efficios.com>
Date: Mon, 13 Sep 2021 14:16:22 -0400
Subject: [PATCH 2/2] fix: Revert "Makefile: Enable -Wimplicit-fallthrough for
 Clang" (v5.15)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Starting with v5.15, "-Wimplicit-fallthrough=5" was added to the build
flags which requires the use of "__attribute__((__fallthrough__))" to
annotate fallthrough case statements.

See upstream commit by the man himself:

  commit d936eb23874433caa3e3d841cfa16f5434b85dcf
  Author: Linus Torvalds <torvalds@linux-foundation.org>
  Date:   Thu Jul 15 18:05:31 2021 -0700

    Revert "Makefile: Enable -Wimplicit-fallthrough for Clang"

    This reverts commit b7eb335e26a9c7f258c96b3962c283c379d3ede0.

    It turns out that the problem with the clang -Wimplicit-fallthrough
    warning is not about the kernel source code, but about clang itself, and
    that the warning is unusable until clang fixes its broken ways.

    In particular, when you enable this warning for clang, you not only get
    warnings about implicit fallthroughs.  You also get this:

       warning: fallthrough annotation in unreachable code [-Wimplicit-fallthrough]

    which is completely broken becasue it

     (a) doesn't even tell you where the problem is (seriously: no line
         numbers, no filename, no nothing).

     (b) is fundamentally broken anyway, because there are perfectly valid
         reasons to have a fallthrough statement even if it turns out that
         it can perhaps not be reached.

    In the kernel, an example of that second case is code in the scheduler:

                    switch (state) {
                    case cpuset:
                            if (IS_ENABLED(CONFIG_CPUSETS)) {
                                    cpuset_cpus_allowed_fallback(p);
                                    state = possible;
                                    break;
                            }
                            fallthrough;
                    case possible:

    where if CONFIG_CPUSETS is enabled you actually never hit the
    fallthrough case at all.  But that in no way makes the fallthrough
    wrong.

    So the warning is completely broken, and enabling it for clang is a very
    bad idea.

    In the meantime, we can keep the gcc option enabled, and make the gcc
    build use

        -Wimplicit-fallthrough=5

    which means that we will at least continue to require a proper
    fallthrough statement, and that gcc won't silently accept the magic
    comment versions. Because gcc does this all correctly, and while the odd
    "=5" part is kind of obscure, it's documented in [1]:

      "-Wimplicit-fallthrough=5 doesn’t recognize any comments as
       fallthrough comments, only attributes disable the warning"

    so if clang ever fixes its bad behavior we can try enabling it there again.

Upstream-Status: backport [https://git.lttng.org/?p=lttng-modules.git;a=commit;h=c190d76e8c7b44d62b3651ab845b765c1b1f8104]

Change-Id: Iea69849592fb69ac04fb9bb28efcd6b8dce8ba88
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 include/counter/counter-api.h         |   4 +-
 include/lttng/events-internal.h       |  11 ++-
 include/wrapper/compiler_attributes.h |  34 +++++++
 src/lib/counter/counter.c             |  13 ++-
 src/lttng-abi.c                       |  91 ++++++++++++------
 src/lttng-bytecode-interpreter.c      |   4 +-
 src/lttng-bytecode-specialize.c       |   5 +-
 src/lttng-events.c                    | 129 +++++++++++++++++---------
 src/lttng-string-utils.c              |   3 +-
 src/probes/lttng-kretprobes.c         |   7 +-
 10 files changed, 215 insertions(+), 86 deletions(-)
 create mode 100644 include/wrapper/compiler_attributes.h

diff --git a/include/counter/counter-api.h b/include/counter/counter-api.h
index fbc65818..c9f2b141 100644
--- a/include/counter/counter-api.h
+++ b/include/counter/counter-api.h
@@ -15,6 +15,7 @@
 #include <linux/bitops.h>
 #include <counter/counter.h>
 #include <counter/counter-internal.h>
+#include <wrapper/compiler_attributes.h>
 #include <wrapper/limits.h>
 
 /*
@@ -256,7 +257,8 @@ static __always_inline int lttng_counter_add(const struct lib_counter_config *co
 				    const size_t *dimension_indexes, int64_t v)
 {
 	switch (config->alloc) {
-	case COUNTER_ALLOC_PER_CPU:	/* Fallthrough */
+	case COUNTER_ALLOC_PER_CPU:
+		lttng_fallthrough;
 	case COUNTER_ALLOC_PER_CPU | COUNTER_ALLOC_GLOBAL:
 		return __lttng_counter_add_percpu(config, counter, dimension_indexes, v);
 	case COUNTER_ALLOC_GLOBAL:
diff --git a/include/lttng/events-internal.h b/include/lttng/events-internal.h
index cd560de8..ca2190c4 100644
--- a/include/lttng/events-internal.h
+++ b/include/lttng/events-internal.h
@@ -8,6 +8,8 @@
 #ifndef _LTTNG_EVENTS_INTERNAL_H
 #define _LTTNG_EVENTS_INTERNAL_H
 
+#include <wrapper/compiler_attributes.h>
+
 #include <lttng/events.h>
 
 struct lttng_syscall_filter;
@@ -561,9 +563,12 @@ static inline bool lttng_kernel_type_is_bytewise_integer(const struct lttng_kern
 	if (!type_integer)
 		return false;
 	switch (type_integer->size) {
-	case 8:		/* Fall-through. */
-	case 16:	/* Fall-through. */
-	case 32:	/* Fall-through. */
+	case 8:
+		lttng_fallthrough;
+	case 16:
+		lttng_fallthrough;
+	case 32:
+		lttng_fallthrough;
 	case 64:
 		break;
 	default:
diff --git a/include/wrapper/compiler_attributes.h b/include/wrapper/compiler_attributes.h
new file mode 100644
index 00000000..c2c96e76
--- /dev/null
+++ b/include/wrapper/compiler_attributes.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
+ *
+ * wrapper/compiler_attributes.h
+ *
+ * Copyright (C) 2021 Michael Jeanson <mjeanson@efficios.com>
+ */
+
+#ifndef _LTTNG_WRAPPER_COMPILER_ATTRIBUTES_H
+#define _LTTNG_WRAPPER_COMPILER_ATTRIBUTES_H
+
+#include <lttng/kernel-version.h>
+
+#if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(4,20,0))
+#include <linux/compiler_attributes.h>
+#endif
+
+#if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,4,0))
+
+/*
+ * Use the kernel provided fallthrough attribute macro.
+ */
+#define lttng_fallthrough fallthrough
+
+#else /* LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,4,0) */
+
+/*
+ * Fallback to the comment for kernels pre 5.15 that don't build with
+ * '-Wimplicit-fallthrough=5'.
+ */
+#define lttng_fallthrough do {} while (0)  /* fallthrough */
+
+#endif /* LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,4,0) */
+
+#endif /* _LTTNG_WRAPPER_COMPILER_ATTRIBUTES_H */
diff --git a/src/lib/counter/counter.c b/src/lib/counter/counter.c
index a4500a0e..bf038aac 100644
--- a/src/lib/counter/counter.c
+++ b/src/lib/counter/counter.c
@@ -11,6 +11,7 @@
 #include <linux/cpumask.h>
 #include <counter/counter.h>
 #include <counter/counter-internal.h>
+#include <wrapper/compiler_attributes.h>
 #include <wrapper/vmalloc.h>
 #include <wrapper/limits.h>
 
@@ -324,7 +325,8 @@ int lttng_counter_aggregate(const struct lib_counter_config *config,
 	*underflow = false;
 
 	switch (config->alloc) {
-	case COUNTER_ALLOC_GLOBAL:	/* Fallthrough */
+	case COUNTER_ALLOC_GLOBAL:
+		lttng_fallthrough;
 	case COUNTER_ALLOC_PER_CPU | COUNTER_ALLOC_GLOBAL:
 		/* Read global counter. */
 		ret = lttng_counter_read(config, counter, dimension_indexes,
@@ -342,7 +344,8 @@ int lttng_counter_aggregate(const struct lib_counter_config *config,
 	switch (config->alloc) {
 	case COUNTER_ALLOC_GLOBAL:
 		break;
-	case COUNTER_ALLOC_PER_CPU | COUNTER_ALLOC_GLOBAL:	/* Fallthrough */
+	case COUNTER_ALLOC_PER_CPU | COUNTER_ALLOC_GLOBAL:
+		lttng_fallthrough;
 	case COUNTER_ALLOC_PER_CPU:
 		//TODO: integrate with CPU hotplug and online cpus
 		for (cpu = 0; cpu < num_possible_cpus(); cpu++) {
@@ -448,7 +451,8 @@ int lttng_counter_clear(const struct lib_counter_config *config,
 	int cpu, ret;
 
 	switch (config->alloc) {
-	case COUNTER_ALLOC_GLOBAL:	/* Fallthrough */
+	case COUNTER_ALLOC_GLOBAL:
+		lttng_fallthrough;
 	case COUNTER_ALLOC_PER_CPU | COUNTER_ALLOC_GLOBAL:
 		/* Clear global counter. */
 		ret = lttng_counter_clear_cpu(config, counter, dimension_indexes, -1);
@@ -462,7 +466,8 @@ int lttng_counter_clear(const struct lib_counter_config *config,
 	switch (config->alloc) {
 	case COUNTER_ALLOC_GLOBAL:
 		break;
-	case COUNTER_ALLOC_PER_CPU | COUNTER_ALLOC_GLOBAL:	/* Fallthrough */
+	case COUNTER_ALLOC_PER_CPU | COUNTER_ALLOC_GLOBAL:
+		lttng_fallthrough;
 	case COUNTER_ALLOC_PER_CPU:
 		//TODO: integrate with CPU hotplug and online cpus
 		for (cpu = 0; cpu < num_possible_cpus(); cpu++) {
diff --git a/src/lttng-abi.c b/src/lttng-abi.c
index cc453894..eac1afd1 100644
--- a/src/lttng-abi.c
+++ b/src/lttng-abi.c
@@ -34,6 +34,7 @@
 #include <ringbuffer/vfs.h>
 #include <ringbuffer/backend.h>
 #include <ringbuffer/frontend.h>
+#include <wrapper/compiler_attributes.h>
 #include <wrapper/poll.h>
 #include <wrapper/file.h>
 #include <wrapper/kref.h>
@@ -1332,7 +1333,8 @@ long lttng_metadata_ring_buffer_ioctl(struct file *filp,
 		 */
 		return -ENOSYS;
 	}
-	case LTTNG_KERNEL_ABI_RING_BUFFER_FLUSH_EMPTY:	/* Fall-through. */
+	case LTTNG_KERNEL_ABI_RING_BUFFER_FLUSH_EMPTY:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_RING_BUFFER_FLUSH:
 	{
 		struct lttng_metadata_stream *stream = filp->private_data;
@@ -1441,7 +1443,8 @@ long lttng_metadata_ring_buffer_compat_ioctl(struct file *filp,
 		 */
 		return -ENOSYS;
 	}
-	case LTTNG_KERNEL_ABI_RING_BUFFER_FLUSH_EMPTY:	/* Fall-through. */
+	case LTTNG_KERNEL_ABI_RING_BUFFER_FLUSH_EMPTY:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_RING_BUFFER_FLUSH:
 	{
 		struct lttng_metadata_stream *stream = filp->private_data;
@@ -1758,8 +1761,10 @@ int lttng_abi_validate_event_param(struct lttng_kernel_abi_event *event_param)
 	switch (event_param->instrumentation) {
 	case LTTNG_KERNEL_ABI_SYSCALL:
 		switch (event_param->u.syscall.entryexit) {
-		case LTTNG_KERNEL_ABI_SYSCALL_ENTRY:	/* Fall-through */
-		case LTTNG_KERNEL_ABI_SYSCALL_EXIT:		/* Fall-through */
+		case LTTNG_KERNEL_ABI_SYSCALL_ENTRY:
+			lttng_fallthrough;
+		case LTTNG_KERNEL_ABI_SYSCALL_EXIT:
+			lttng_fallthrough;
 		case LTTNG_KERNEL_ABI_SYSCALL_ENTRYEXIT:
 			break;
 		default:
@@ -1783,20 +1788,26 @@ int lttng_abi_validate_event_param(struct lttng_kernel_abi_event *event_param)
 		switch (event_param->u.kretprobe.entryexit) {
 		case LTTNG_KERNEL_ABI_SYSCALL_ENTRYEXIT:
 			break;
-		case LTTNG_KERNEL_ABI_SYSCALL_ENTRY:	/* Fall-through */
-		case LTTNG_KERNEL_ABI_SYSCALL_EXIT:		/* Fall-through */
+		case LTTNG_KERNEL_ABI_SYSCALL_ENTRY:
+			lttng_fallthrough;
+		case LTTNG_KERNEL_ABI_SYSCALL_EXIT:
+			lttng_fallthrough;
 		default:
 			return -EINVAL;
 		}
 		break;
 
-	case LTTNG_KERNEL_ABI_TRACEPOINT:	/* Fall-through */
-	case LTTNG_KERNEL_ABI_KPROBE:	/* Fall-through */
+	case LTTNG_KERNEL_ABI_TRACEPOINT:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_UPROBE:
 		break;
 
-	case LTTNG_KERNEL_ABI_FUNCTION:	/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		return -EINVAL;
 	}
@@ -1830,18 +1841,23 @@ int lttng_abi_create_event(struct file *channel_file,
 	}
 
 	switch (event_param->instrumentation) {
-	case LTTNG_KERNEL_ABI_TRACEPOINT:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_TRACEPOINT:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_SYSCALL:
 		fops = &lttng_event_recorder_enabler_fops;
 		break;
-	case LTTNG_KERNEL_ABI_KPROBE:			/* Fall-through */
-	case LTTNG_KERNEL_ABI_KRETPROBE:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_KRETPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_UPROBE:
 		fops = &lttng_event_recorder_event_fops;
 		break;
 
-	case LTTNG_KERNEL_ABI_FUNCTION:			/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:			/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		return -EINVAL;
 	}
@@ -1867,7 +1883,8 @@ int lttng_abi_create_event(struct file *channel_file,
 		goto event_error;
 
 	switch (event_param->instrumentation) {
-	case LTTNG_KERNEL_ABI_TRACEPOINT:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_TRACEPOINT:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_SYSCALL:
 	{
 		struct lttng_event_enabler *event_enabler;
@@ -1887,8 +1904,10 @@ int lttng_abi_create_event(struct file *channel_file,
 		break;
 	}
 
-	case LTTNG_KERNEL_ABI_KPROBE:			/* Fall-through */
-	case LTTNG_KERNEL_ABI_KRETPROBE:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_KRETPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_UPROBE:
 	{
 		struct lttng_kernel_event_recorder *event;
@@ -1908,8 +1927,10 @@ int lttng_abi_create_event(struct file *channel_file,
 		break;
 	}
 
-	case LTTNG_KERNEL_ABI_FUNCTION:			/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:			/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		ret = -EINVAL;
 		goto event_error;
@@ -2043,18 +2064,23 @@ int lttng_abi_create_event_notifier(struct file *event_notifier_group_file,
 	}
 
 	switch (event_notifier_param->event.instrumentation) {
-	case LTTNG_KERNEL_ABI_TRACEPOINT:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_TRACEPOINT:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_SYSCALL:
 		fops = &lttng_event_notifier_enabler_fops;
 		break;
-	case LTTNG_KERNEL_ABI_KPROBE:			/* Fall-through */
-	case LTTNG_KERNEL_ABI_KRETPROBE:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_KRETPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_UPROBE:
 		fops = &lttng_event_notifier_event_fops;
 		break;
 
-	case LTTNG_KERNEL_ABI_FUNCTION:			/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:			/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		ret = -EINVAL;
 		goto inval_instr;
@@ -2086,7 +2112,8 @@ int lttng_abi_create_event_notifier(struct file *event_notifier_group_file,
 		goto event_notifier_error;
 
 	switch (event_notifier_param->event.instrumentation) {
-	case LTTNG_KERNEL_ABI_TRACEPOINT:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_TRACEPOINT:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_SYSCALL:
 	{
 		struct lttng_event_notifier_enabler *enabler;
@@ -2110,8 +2137,10 @@ int lttng_abi_create_event_notifier(struct file *event_notifier_group_file,
 		break;
 	}
 
-	case LTTNG_KERNEL_ABI_KPROBE:			/* Fall-through */
-	case LTTNG_KERNEL_ABI_KRETPROBE:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_KRETPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_UPROBE:
 	{
 		struct lttng_kernel_event_notifier *event_notifier;
@@ -2135,8 +2164,10 @@ int lttng_abi_create_event_notifier(struct file *event_notifier_group_file,
 		break;
 	}
 
-	case LTTNG_KERNEL_ABI_FUNCTION:			/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:			/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		ret = -EINVAL;
 		goto event_notifier_error;
diff --git a/src/lttng-bytecode-interpreter.c b/src/lttng-bytecode-interpreter.c
index b46a23b7..a2a932c6 100644
--- a/src/lttng-bytecode-interpreter.c
+++ b/src/lttng-bytecode-interpreter.c
@@ -7,6 +7,7 @@
  * Copyright (C) 2010-2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  */
 
+#include <wrapper/compiler_attributes.h>
 #include <wrapper/uaccess.h>
 #include <wrapper/objtool.h>
 #include <wrapper/types.h>
@@ -421,7 +422,8 @@ static int dynamic_get_index(struct lttng_kernel_probe_ctx *lttng_probe_ctx,
 		}
 		break;
 	case LOAD_ROOT_CONTEXT:
-	case LOAD_ROOT_APP_CONTEXT:	/* Fall-through */
+		lttng_fallthrough;
+	case LOAD_ROOT_APP_CONTEXT:
 	{
 		ret = context_get_index(lttng_probe_ctx,
 				&stack_top->u.ptr,
diff --git a/src/lttng-bytecode-specialize.c b/src/lttng-bytecode-specialize.c
index c4b9d04b..f8b5f19d 100644
--- a/src/lttng-bytecode-specialize.c
+++ b/src/lttng-bytecode-specialize.c
@@ -8,6 +8,8 @@
  */
 
 #include <linux/slab.h>
+#include <wrapper/compiler_attributes.h>
+
 #include <lttng/lttng-bytecode.h>
 #include <lttng/align.h>
 #include <lttng/events-internal.h>
@@ -271,7 +273,8 @@ static int specialize_get_index(struct bytecode_runtime *runtime,
 		}
 		case OBJECT_TYPE_STRUCT:
 			/* Only generated by the specialize phase. */
-		case OBJECT_TYPE_VARIANT:	/* Fall-through */
+		case OBJECT_TYPE_VARIANT:
+			lttng_fallthrough;
 		default:
 			printk(KERN_WARNING "LTTng: bytecode: Unexpected get index type %d",
 				(int) stack_top->load.object_type);
diff --git a/src/lttng-events.c b/src/lttng-events.c
index e785fe4d..230e3934 100644
--- a/src/lttng-events.c
+++ b/src/lttng-events.c
@@ -28,6 +28,7 @@
 #include <linux/vmalloc.h>
 #include <linux/dmi.h>
 
+#include <wrapper/compiler_attributes.h>
 #include <wrapper/uuid.h>
 #include <wrapper/vmalloc.h>	/* for wrapper_vmalloc_sync_mappings() */
 #include <wrapper/random.h>
@@ -659,12 +660,14 @@ int lttng_event_enable(struct lttng_kernel_event_common *event)
 		goto end;
 	}
 	switch (event->priv->instrumentation) {
-	case LTTNG_KERNEL_ABI_TRACEPOINT:	/* Fall-through */
+	case LTTNG_KERNEL_ABI_TRACEPOINT:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_SYSCALL:
 		ret = -EINVAL;
 		break;
 
-	case LTTNG_KERNEL_ABI_KPROBE:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_UPROBE:
 		WRITE_ONCE(event->enabled, 1);
 		break;
@@ -673,8 +676,10 @@ int lttng_event_enable(struct lttng_kernel_event_common *event)
 		ret = lttng_kretprobes_event_enable_state(event, 1);
 		break;
 
-	case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 		ret = -EINVAL;
@@ -719,12 +724,14 @@ int lttng_event_disable(struct lttng_kernel_event_common *event)
 		goto end;
 	}
 	switch (event->priv->instrumentation) {
-	case LTTNG_KERNEL_ABI_TRACEPOINT:	/* Fall-through */
+	case LTTNG_KERNEL_ABI_TRACEPOINT:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_SYSCALL:
 		ret = -EINVAL;
 		break;
 
-	case LTTNG_KERNEL_ABI_KPROBE:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_UPROBE:
 		WRITE_ONCE(event->enabled, 0);
 		break;
@@ -733,8 +740,10 @@ int lttng_event_disable(struct lttng_kernel_event_common *event)
 		ret = lttng_kretprobes_event_enable_state(event, 0);
 		break;
 
-	case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 		ret = -EINVAL;
@@ -873,15 +882,20 @@ struct lttng_kernel_event_recorder *_lttng_kernel_event_recorder_create(struct l
 		event_name = event_desc->event_name;
 		break;
 
-	case LTTNG_KERNEL_ABI_KPROBE:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_UPROBE:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_KRETPROBE:	/* Fall-through */
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_UPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_KRETPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_SYSCALL:
 		event_name = event_param->name;
 		break;
 
-	case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 		ret = -EINVAL;
@@ -1093,8 +1107,10 @@ struct lttng_kernel_event_recorder *_lttng_kernel_event_recorder_create(struct l
 		WARN_ON_ONCE(!ret);
 		break;
 
-	case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 		ret = -EINVAL;
@@ -1141,15 +1157,20 @@ struct lttng_kernel_event_notifier *_lttng_event_notifier_create(
 		event_name = event_desc->event_name;
 		break;
 
-	case LTTNG_KERNEL_ABI_KPROBE:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_UPROBE:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_UPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_SYSCALL:
 		event_name = event_notifier_param->event.name;
 		break;
 
-	case LTTNG_KERNEL_ABI_KRETPROBE:	/* Fall-through */
-	case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KRETPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 		ret = -EINVAL;
@@ -1296,9 +1317,12 @@ struct lttng_kernel_event_notifier *_lttng_event_notifier_create(
 		WARN_ON_ONCE(!ret);
 		break;
 
-	case LTTNG_KERNEL_ABI_KRETPROBE:	/* Fall-through */
-	case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KRETPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 		ret = -EINVAL;
@@ -1423,14 +1447,18 @@ void register_event(struct lttng_kernel_event_recorder *event_recorder)
 		ret = lttng_syscall_filter_enable_event(event_recorder->chan, event_recorder);
 		break;
 
-	case LTTNG_KERNEL_ABI_KPROBE:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_UPROBE:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_UPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_KRETPROBE:
 		ret = 0;
 		break;
 
-	case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 	}
@@ -1481,7 +1509,8 @@ int _lttng_event_unregister(struct lttng_kernel_event_recorder *event_recorder)
 		ret = 0;
 		break;
 
-	case LTTNG_KERNEL_ABI_FUNCTION:	/* Fall-through */
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 	}
@@ -1512,14 +1541,18 @@ void register_event_notifier(struct lttng_kernel_event_notifier *event_notifier)
 		ret = lttng_syscall_filter_enable_event_notifier(event_notifier);
 		break;
 
-	case LTTNG_KERNEL_ABI_KPROBE:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KPROBE:
+		lttng_fallthrough;
 	case LTTNG_KERNEL_ABI_UPROBE:
 		ret = 0;
 		break;
 
-	case LTTNG_KERNEL_ABI_KRETPROBE:	/* Fall-through */
-	case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KRETPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 	}
@@ -1559,9 +1592,12 @@ int _lttng_event_notifier_unregister(
 		ret = lttng_syscall_filter_disable_event_notifier(event_notifier);
 		break;
 
-	case LTTNG_KERNEL_ABI_KRETPROBE:	/* Fall-through */
-	case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-	case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+	case LTTNG_KERNEL_ABI_KRETPROBE:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_FUNCTION:
+		lttng_fallthrough;
+	case LTTNG_KERNEL_ABI_NOOP:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 	}
@@ -1614,8 +1650,10 @@ void _lttng_event_destroy(struct lttng_kernel_event_common *event)
 			lttng_uprobes_destroy_event_private(event_recorder);
 			break;
 
-		case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-		case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+		case LTTNG_KERNEL_ABI_FUNCTION:
+			lttng_fallthrough;
+		case LTTNG_KERNEL_ABI_NOOP:
+			lttng_fallthrough;
 		default:
 			WARN_ON_ONCE(1);
 		}
@@ -1647,9 +1685,12 @@ void _lttng_event_destroy(struct lttng_kernel_event_common *event)
 			lttng_uprobes_destroy_event_notifier_private(event_notifier);
 			break;
 
-		case LTTNG_KERNEL_ABI_KRETPROBE:	/* Fall-through */
-		case LTTNG_KERNEL_ABI_FUNCTION:		/* Fall-through */
-		case LTTNG_KERNEL_ABI_NOOP:		/* Fall-through */
+		case LTTNG_KERNEL_ABI_KRETPROBE:
+			lttng_fallthrough;
+		case LTTNG_KERNEL_ABI_FUNCTION:
+			lttng_fallthrough;
+		case LTTNG_KERNEL_ABI_NOOP:
+			lttng_fallthrough;
 		default:
 			WARN_ON_ONCE(1);
 		}
@@ -2713,7 +2754,8 @@ void lttng_session_sync_event_enablers(struct lttng_kernel_session *session)
 		int nr_filters = 0;
 
 		switch (event_recorder_priv->parent.instrumentation) {
-		case LTTNG_KERNEL_ABI_TRACEPOINT:	/* Fall-through */
+		case LTTNG_KERNEL_ABI_TRACEPOINT:
+			lttng_fallthrough;
 		case LTTNG_KERNEL_ABI_SYSCALL:
 			/* Enable events */
 			list_for_each_entry(enabler_ref,
@@ -2807,7 +2849,8 @@ void lttng_event_notifier_group_sync_enablers(struct lttng_event_notifier_group
 		int nr_filters = 0, nr_captures = 0;
 
 		switch (event_notifier_priv->parent.instrumentation) {
-		case LTTNG_KERNEL_ABI_TRACEPOINT:	/* Fall-through */
+		case LTTNG_KERNEL_ABI_TRACEPOINT:
+			lttng_fallthrough;
 		case LTTNG_KERNEL_ABI_SYSCALL:
 			/* Enable event_notifiers */
 			list_for_each_entry(enabler_ref,
@@ -3877,7 +3920,7 @@ int print_escaped_ctf_string(struct lttng_kernel_session *session, const char *s
 			if (ret)
 				goto error;
 			/* We still print the current char */
-			/* Fallthrough */
+			lttng_fallthrough;
 		default:
 			ret = lttng_metadata_printf(session, "%c", cur);
 			break;
diff --git a/src/lttng-string-utils.c b/src/lttng-string-utils.c
index d9447903..65946193 100644
--- a/src/lttng-string-utils.c
+++ b/src/lttng-string-utils.c
@@ -4,6 +4,7 @@
  */
 
 #include <linux/types.h>
+#include <wrapper/compiler_attributes.h>
 
 #include <lttng/string-utils.h>
 
@@ -302,7 +303,7 @@ retry:
 			p = pattern_get_char_at_cb(p_at,
 				pattern_get_char_at_cb_data);
 
-			/* Fall-through. */
+			lttng_fallthrough;
 		default:
 			/*
 			 * Default case which will compare the escaped
diff --git a/src/probes/lttng-kretprobes.c b/src/probes/lttng-kretprobes.c
index 0fa6a1bf..1d0a5ecb 100644
--- a/src/probes/lttng-kretprobes.c
+++ b/src/probes/lttng-kretprobes.c
@@ -14,6 +14,7 @@
 #include <lttng/events.h>
 #include <lttng/events-internal.h>
 #include <ringbuffer/frontend_types.h>
+#include <wrapper/compiler_attributes.h>
 #include <wrapper/vmalloc.h>
 #include <wrapper/irqflags.h>
 #include <lttng/tracer.h>
@@ -61,7 +62,8 @@ int _lttng_kretprobes_handler(struct kretprobe_instance *krpi,
 			return 0;
 		break;
 	}
-	case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:	/* Fall-through. */
+	case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 	}
@@ -90,7 +92,8 @@ int _lttng_kretprobes_handler(struct kretprobe_instance *krpi,
 		chan->ops->event_commit(&ctx);
 		break;
 	}
-	case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:	/* Fall-through. */
+	case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER:
+		lttng_fallthrough;
 	default:
 		WARN_ON_ONCE(1);
 	}
-- 
2.19.1