diff mbox series

[RFC,1/3] llvm-cov: add Clang's Source-based Code Coverage support

Message ID 20240824230641.385839-2-wentaoz5@illinois.edu
State Superseded
Headers show
Series Enable measuring the kernel's Source-based Code Coverage and MC/DC with Clang | expand

Commit Message

Wentao Zhang Aug. 24, 2024, 11:06 p.m. UTC
Implement debugfs entries for serializing profiles and resetting
counters/bitmaps. Also adds Source-based Code Coverage flags and kconfig
options.

This work reuses a portion of code from a previous effort by Sami
Tolvanen et al. [1], specifically its debugfs interface and the
underlying profile processing, but discards all its PGO-specific parts,
notably value profiling.  To our end (code coverage, like MC/DC,
required for high assurance), we do instrumentation at the compiler
frontend, instead of IR; we care about counters and bitmaps, but not
value profiling.

[1] https://lore.kernel.org/lkml/20210407211704.367039-1-morbo@google.com/

Signed-off-by: Wentao Zhang <wentaoz5@illinois.edu>
Signed-off-by: Chuck Wolber <chuck.wolber@boeing.com>
---
 Makefile                          |   3 +
 arch/Kconfig                      |   1 +
 arch/x86/Kconfig                  |   1 +
 arch/x86/kernel/vmlinux.lds.S     |   2 +
 include/asm-generic/vmlinux.lds.h |  38 +++++
 kernel/Makefile                   |   1 +
 kernel/llvm-cov/Kconfig           |  29 ++++
 kernel/llvm-cov/Makefile          |   5 +
 kernel/llvm-cov/fs.c              | 253 ++++++++++++++++++++++++++++++
 kernel/llvm-cov/llvm-cov.h        | 156 ++++++++++++++++++
 scripts/Makefile.lib              |  10 ++
 scripts/mod/modpost.c             |   2 +
 12 files changed, 501 insertions(+)
 create mode 100644 kernel/llvm-cov/Kconfig
 create mode 100644 kernel/llvm-cov/Makefile
 create mode 100644 kernel/llvm-cov/fs.c
 create mode 100644 kernel/llvm-cov/llvm-cov.h

Comments

Thomas Gleixner Aug. 25, 2024, 11:52 a.m. UTC | #1
On Sat, Aug 24 2024 at 18:06, Wentao Zhang wrote:
>  Makefile                          |   3 +
>  arch/Kconfig                      |   1 +
>  arch/x86/Kconfig                  |   1 +
>  arch/x86/kernel/vmlinux.lds.S     |   2 +
>  include/asm-generic/vmlinux.lds.h |  38 +++++
>  kernel/Makefile                   |   1 +
>  kernel/llvm-cov/Kconfig           |  29 ++++
>  kernel/llvm-cov/Makefile          |   5 +
>  kernel/llvm-cov/fs.c              | 253 ++++++++++++++++++++++++++++++
>  kernel/llvm-cov/llvm-cov.h        | 156 ++++++++++++++++++
>  scripts/Makefile.lib              |  10 ++
>  scripts/mod/modpost.c             |   2 +

Please split this into two parts:

   1) Add the infrastructure
   2) Enable it on x86

Also the ordering of this patch series is wrong.

First you enable it on x86 and then you mark the places which cannot be
instrumented. You really want to do this in this order:

   1) Add the infrastructure
   2) Prevent instrumentation in drivers/firmware
   3) Prevent instrumentation in kernel/trace
   4) Prevent instrumentation in modfinal
   5) Prevent instrumentation in x86
   6) Enable it on x86

Thanks,

        tglx
diff mbox series

Patch

diff --git a/Makefile b/Makefile
index 68ebd6d6b444..1750a2b7dfe8 100644
--- a/Makefile
+++ b/Makefile
@@ -737,6 +737,9 @@  endif # KBUILD_EXTMOD
 # Defaults to vmlinux, but the arch makefile usually adds further targets
 all: vmlinux
 
+CFLAGS_LLVM_COV := -fprofile-instr-generate -fcoverage-mapping
+export CFLAGS_LLVM_COV
+
 CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage
 ifdef CONFIG_CC_IS_GCC
 CFLAGS_GCOV	+= -fno-tree-loop-im
diff --git a/arch/Kconfig b/arch/Kconfig
index 975dd22a2dbd..0727265f677f 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1601,6 +1601,7 @@  config ARCH_HAS_KERNEL_FPU_SUPPORT
 	  the kernel, as described in Documentation/core-api/floating-point.rst.
 
 source "kernel/gcov/Kconfig"
+source "kernel/llvm-cov/Kconfig"
 
 source "scripts/gcc-plugins/Kconfig"
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 007bab9f2a0e..87a793b82bab 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -85,6 +85,7 @@  config X86
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_KCOV			if X86_64
+	select ARCH_HAS_LLVM_COV		if X86_64
 	select ARCH_HAS_KERNEL_FPU_SUPPORT
 	select ARCH_HAS_MEM_ENCRYPT
 	select ARCH_HAS_MEMBARRIER_SYNC_CORE
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 6e73403e874f..90433772240a 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -191,6 +191,8 @@  SECTIONS
 
 	BUG_TABLE
 
+	LLVM_COV_DATA
+
 	ORC_UNWIND_TABLE
 
 	. = ALIGN(PAGE_SIZE);
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 1ae44793132a..770ff8469dcd 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -334,6 +334,44 @@ 
 #define THERMAL_TABLE(name)
 #endif
 
+#ifdef CONFIG_LLVM_COV_KERNEL
+#define LLVM_COV_DATA							\
+	__llvm_prf_data : AT(ADDR(__llvm_prf_data) - LOAD_OFFSET) {	\
+		__llvm_prf_start = .;					\
+		__llvm_prf_data_start = .;				\
+		*(__llvm_prf_data)					\
+		__llvm_prf_data_end = .;				\
+	}								\
+	__llvm_prf_cnts : AT(ADDR(__llvm_prf_cnts) - LOAD_OFFSET) {	\
+		__llvm_prf_cnts_start = .;				\
+		*(__llvm_prf_cnts)					\
+		__llvm_prf_cnts_end = .;				\
+	}								\
+	__llvm_prf_names : AT(ADDR(__llvm_prf_names) - LOAD_OFFSET) {	\
+		__llvm_prf_names_start = .;				\
+		*(__llvm_prf_names)					\
+		__llvm_prf_names_end = .;				\
+	}								\
+	__llvm_prf_bits : AT(ADDR(__llvm_prf_bits) - LOAD_OFFSET) {	\
+		__llvm_prf_bits_start = .;				\
+		*(__llvm_prf_bits)					\
+		__llvm_prf_bits_end = .;				\
+	}								\
+	__llvm_covfun : AT(ADDR(__llvm_covfun) - LOAD_OFFSET) {		\
+		__llvm_covfun_start = .;				\
+		*(__llvm_covfun)					\
+		__llvm_covfun_end = .;					\
+	}								\
+	__llvm_covmap : AT(ADDR(__llvm_covmap) - LOAD_OFFSET) {		\
+		__llvm_covmap_start = .;				\
+		*(__llvm_covmap)					\
+		__llvm_covmap_end = .;					\
+		__llvm_prf_end = .;					\
+	}
+#else
+#define LLVM_COV_DATA
+#endif
+
 #define KERNEL_DTB()							\
 	STRUCT_ALIGN();							\
 	__dtb_start = .;						\
diff --git a/kernel/Makefile b/kernel/Makefile
index 3c13240dfc9f..773e6a9ee00a 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -117,6 +117,7 @@  obj-$(CONFIG_HAVE_STATIC_CALL) += static_call.o
 obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call_inline.o
 obj-$(CONFIG_CFI_CLANG) += cfi.o
 obj-$(CONFIG_NUMA) += numa.o
+obj-$(CONFIG_LLVM_COV_KERNEL) += llvm-cov/
 
 obj-$(CONFIG_PERF_EVENTS) += events/
 
diff --git a/kernel/llvm-cov/Kconfig b/kernel/llvm-cov/Kconfig
new file mode 100644
index 000000000000..505eba5bd23c
--- /dev/null
+++ b/kernel/llvm-cov/Kconfig
@@ -0,0 +1,29 @@ 
+# SPDX-License-Identifier: GPL-2.0-only
+menu "Clang's source-based kernel coverage measurement (EXPERIMENTAL)"
+
+config ARCH_HAS_LLVM_COV
+	bool
+
+config LLVM_COV_KERNEL
+	bool "Enable Clang's source-based kernel coverage measurement"
+	depends on DEBUG_FS
+	depends on ARCH_HAS_LLVM_COV
+	depends on CC_IS_CLANG && CLANG_VERSION >= 180000
+	default n
+	help
+	  This option enables Clang's Source-based Code Coverage.
+
+	  If unsure, say N.
+
+	  On a kernel compiled with this option, run your test suites, and
+	  download the raw profile from /sys/kernel/debug/llvm-cov/profraw.
+	  This file can then be converted into the indexed format with
+	  llvm-profdata and used to generate coverage reports with llvm-cov.
+
+	  Note that a kernel compiled with coverage flags will be significantly
+	  larger and run slower.
+
+	  Note that the debugfs filesystem has to be mounted to access the raw
+	  profile.
+
+endmenu
diff --git a/kernel/llvm-cov/Makefile b/kernel/llvm-cov/Makefile
new file mode 100644
index 000000000000..a0f45e05f8fb
--- /dev/null
+++ b/kernel/llvm-cov/Makefile
@@ -0,0 +1,5 @@ 
+# SPDX-License-Identifier: GPL-2.0
+GCOV_PROFILE		:= n
+LLVM_COV_PROFILE	:= n
+
+obj-y	+= fs.o
\ No newline at end of file
diff --git a/kernel/llvm-cov/fs.c b/kernel/llvm-cov/fs.c
new file mode 100644
index 000000000000..c56f660a174e
--- /dev/null
+++ b/kernel/llvm-cov/fs.c
@@ -0,0 +1,253 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019	Sami Tolvanen <samitolvanen@google.com>, Google, Inc.
+ * Copyright (C) 2024	Jinghao Jia   <jinghao7@illinois.edu>,   UIUC
+ * Copyright (C) 2024	Wentao Zhang  <wentaoz5@illinois.edu>,   UIUC
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will 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.
+ *
+ */
+
+#define pr_fmt(fmt)	"llvm-cov: " fmt
+
+#include <linux/kernel.h>
+#include <linux/debugfs.h>
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/spinlock.h>
+#include "llvm-cov.h"
+
+/*
+ * This lock guards both counter/bitmap reset and serialization of the
+ * raw profile data. Keeping both of these activities separate via locking
+ * ensures that we don't try to serialize data that's being reset.
+ */
+DEFINE_SPINLOCK(llvm_cov_lock);
+
+static struct dentry *directory;
+
+struct llvm_cov_private_data {
+	char *buffer;
+	unsigned long size;
+};
+
+/*
+ * Raw profile data format:
+ * https://llvm.org/docs/InstrProfileFormat.html#raw-profile-format. We will
+ * only populate information that's relevant to basic Source-based Code Coverage
+ * before serialization. Other features like binary IDs, continuous mode,
+ * single-byte mode, value profiling, type profiling etc are not implemented.
+ */
+
+static void llvm_cov_fill_raw_profile_header(void **buffer)
+{
+	struct __llvm_profile_header *header = *(struct __llvm_profile_header **)buffer;
+
+	header->magic = INSTR_PROF_RAW_MAGIC_64;
+	header->version = INSTR_PROF_RAW_VERSION;
+	header->binary_ids_size = 0;
+	header->num_data = __llvm_prf_data_count();
+	header->padding_bytes_before_counters = 0;
+	header->num_counters = __llvm_prf_cnts_count();
+	header->padding_bytes_after_counters =
+		__llvm_prf_get_padding(__llvm_prf_cnts_size());
+	header->num_bitmap_bytes = __llvm_prf_bits_size();
+	header->padding_bytes_after_bitmap_bytes =
+		__llvm_prf_get_padding(__llvm_prf_bits_size());
+	header->names_size = __llvm_prf_names_size();
+	header->counters_delta = (u64)__llvm_prf_cnts_start -
+				 (u64)__llvm_prf_data_start;
+	header->bitmap_delta   = (u64)__llvm_prf_bits_start -
+				 (u64)__llvm_prf_data_start;
+	header->names_delta    = (u64)__llvm_prf_names_start;
+#if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION >= 190000
+	header->num_v_tables = 0;
+	header->v_names_size = 0;
+#endif
+	header->value_kind_last = IPVK_LAST;
+
+	*buffer += sizeof(*header);
+}
+
+/*
+ * Copy the source into the buffer, incrementing the pointer into buffer in the
+ * process.
+ */
+static void llvm_cov_copy_section_to_buffer(void **buffer, void *src,
+					    unsigned long size)
+{
+	memcpy(*buffer, src, size);
+	*buffer += size;
+}
+
+static unsigned long llvm_cov_get_raw_profile_size(void)
+{
+	return sizeof(struct __llvm_profile_header) +
+	       __llvm_prf_data_size() +
+	       __llvm_prf_cnts_size() +
+	       __llvm_prf_get_padding(__llvm_prf_cnts_size()) +
+	       __llvm_prf_bits_size() +
+	       __llvm_prf_get_padding(__llvm_prf_bits_size()) +
+	       __llvm_prf_names_size() +
+	       __llvm_prf_get_padding(__llvm_prf_names_size());
+}
+
+/*
+ * Serialize in-memory data into a format LLVM tools can understand
+ * (https://llvm.org/docs/InstrProfileFormat.html#raw-profile-format)
+ */
+static int llvm_cov_serialize_raw_profile(struct llvm_cov_private_data *p)
+{
+	int err = 0;
+	void *buffer;
+
+	p->size = llvm_cov_get_raw_profile_size();
+	p->buffer = vzalloc(p->size);
+
+	if (!p->buffer) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	buffer = p->buffer;
+
+	llvm_cov_fill_raw_profile_header(&buffer);
+	llvm_cov_copy_section_to_buffer(&buffer, __llvm_prf_data_start,
+					__llvm_prf_data_size());
+	llvm_cov_copy_section_to_buffer(&buffer, __llvm_prf_cnts_start,
+					__llvm_prf_cnts_size());
+	buffer += __llvm_prf_get_padding(__llvm_prf_cnts_size());
+	llvm_cov_copy_section_to_buffer(&buffer, __llvm_prf_bits_start,
+					__llvm_prf_bits_size());
+	buffer += __llvm_prf_get_padding(__llvm_prf_bits_size());
+	llvm_cov_copy_section_to_buffer(&buffer, __llvm_prf_names_start,
+					__llvm_prf_names_size());
+	buffer += __llvm_prf_get_padding(__llvm_prf_names_size());
+
+out:
+	return err;
+}
+
+/* open() implementation for llvm-cov data file. */
+static int llvm_cov_open(struct inode *inode, struct file *file)
+{
+	struct llvm_cov_private_data *data;
+	unsigned long flags;
+	int err;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	flags = llvm_cov_claim_lock();
+
+	err = llvm_cov_serialize_raw_profile(data);
+	if (unlikely(err)) {
+		kfree(data);
+		goto out_unlock;
+	}
+
+	file->private_data = data;
+
+out_unlock:
+	llvm_cov_release_lock(flags);
+out:
+	return err;
+}
+
+/* read() implementation for llvm-cov data file. */
+static ssize_t llvm_cov_read(struct file *file, char __user *buf, size_t count,
+			loff_t *ppos)
+{
+	struct llvm_cov_private_data *data = file->private_data;
+
+	if (!data)
+		return -EBADF;
+
+	return simple_read_from_buffer(buf, count, ppos, data->buffer,
+				       data->size);
+}
+
+/* release() implementation for llvm-cov data file. */
+static int llvm_cov_release(struct inode *inode, struct file *file)
+{
+	struct llvm_cov_private_data *data = file->private_data;
+
+	if (data) {
+		vfree(data->buffer);
+		kfree(data);
+	}
+
+	return 0;
+}
+
+static const struct file_operations llvm_cov_data_fops = {
+	.owner		= THIS_MODULE,
+	.open		= llvm_cov_open,
+	.read		= llvm_cov_read,
+	.llseek		= default_llseek,
+	.release	= llvm_cov_release
+};
+
+/* write() implementation for llvm-cov reset file */
+static ssize_t reset_write(struct file *file, const char __user *addr,
+			   size_t len, loff_t *pos)
+{
+	unsigned long flags;
+
+	flags = llvm_cov_claim_lock();
+	memset(__llvm_prf_cnts_start, 0, __llvm_prf_cnts_size());
+	memset(__llvm_prf_bits_start, 0, __llvm_prf_bits_size());
+	llvm_cov_release_lock(flags);
+
+	return len;
+}
+
+static const struct file_operations llvm_cov_reset_fops = {
+	.owner		= THIS_MODULE,
+	.write		= reset_write,
+	.llseek		= noop_llseek,
+};
+
+/* Create debugfs entries. */
+static int __init llvm_cov_init(void)
+{
+	directory = debugfs_create_dir("llvm-cov", NULL);
+	if (!directory)
+		goto err_remove;
+
+	if (!debugfs_create_file("profraw", 0400, directory, NULL,
+				 &llvm_cov_data_fops))
+		goto err_remove;
+
+	if (!debugfs_create_file("reset", 0200, directory, NULL,
+				 &llvm_cov_reset_fops))
+		goto err_remove;
+
+	return 0;
+
+err_remove:
+	debugfs_remove_recursive(directory);
+	pr_err("initialization failed\n");
+	return -EIO;
+}
+
+/* Remove debugfs entries. */
+static void __exit llvm_cov_exit(void)
+{
+	debugfs_remove_recursive(directory);
+}
+
+module_init(llvm_cov_init);
+module_exit(llvm_cov_exit);
diff --git a/kernel/llvm-cov/llvm-cov.h b/kernel/llvm-cov/llvm-cov.h
new file mode 100644
index 000000000000..d9551a685756
--- /dev/null
+++ b/kernel/llvm-cov/llvm-cov.h
@@ -0,0 +1,156 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019	Sami Tolvanen <samitolvanen@google.com>, Google, Inc.
+ * Copyright (C) 2024	Jinghao Jia   <jinghao7@illinois.edu>,   UIUC
+ * Copyright (C) 2024	Wentao Zhang  <wentaoz5@illinois.edu>,   UIUC
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will 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.
+ *
+ */
+
+#ifndef _LLVM_COV_H
+#define _LLVM_COV_H
+
+extern spinlock_t llvm_cov_lock;
+
+static __always_inline unsigned long llvm_cov_claim_lock(void)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&llvm_cov_lock, flags);
+
+	return flags;
+}
+
+static __always_inline void llvm_cov_release_lock(unsigned long flags)
+{
+	spin_unlock_irqrestore(&llvm_cov_lock, flags);
+}
+
+/*
+ * Note: These internal LLVM definitions must match the compiler version.
+ * See llvm/include/llvm/ProfileData/InstrProfData.inc in LLVM's source code.
+ */
+
+#define INSTR_PROF_RAW_MAGIC_64		\
+		((u64)255 << 56 |	\
+		 (u64)'l' << 48 |	\
+		 (u64)'p' << 40 |	\
+		 (u64)'r' << 32 |	\
+		 (u64)'o' << 24 |	\
+		 (u64)'f' << 16 |	\
+		 (u64)'r' << 8  |	\
+		 (u64)129)
+
+#if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION >= 190000
+#define INSTR_PROF_RAW_VERSION		10
+#define INSTR_PROF_DATA_ALIGNMENT	8
+#define IPVK_LAST			2
+#elif defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION >= 180000
+#define INSTR_PROF_RAW_VERSION		9
+#define INSTR_PROF_DATA_ALIGNMENT	8
+#define IPVK_LAST			1
+#endif
+
+/**
+ * struct __llvm_profile_header - represents the raw profile header data
+ * structure. Description of each member can be found here:
+ * https://llvm.org/docs/InstrProfileFormat.html#header.
+ */
+struct __llvm_profile_header {
+	u64 magic;
+	u64 version;
+	u64 binary_ids_size;
+	u64 num_data;
+	u64 padding_bytes_before_counters;
+	u64 num_counters;
+	u64 padding_bytes_after_counters;
+	u64 num_bitmap_bytes;
+	u64 padding_bytes_after_bitmap_bytes;
+	u64 names_size;
+	u64 counters_delta;
+	u64 bitmap_delta;
+	u64 names_delta;
+#if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION >= 190000
+	u64 num_v_tables;
+	u64 v_names_size;
+#endif
+	u64 value_kind_last;
+};
+
+/**
+ * struct __llvm_profile_data - represents the per-function control structure.
+ * Description of each member can be found here:
+ * https://llvm.org/docs/InstrProfileFormat.html#profile-metadata. To measure
+ * Source-based Code Coverage, the internals of this struct don't matter at run
+ * time. The only purpose of the definition below is to run sizeof() against it
+ * so that we can calculate the "num_data" field in header.
+ */
+struct __llvm_profile_data {
+	const u64 name_ref;
+	const u64 func_hash;
+	const void *counter_ptr;
+	const void *bitmap_ptr;
+	const void *function_pointer;
+	void *values;
+	const u32 num_counters;
+	const u16 num_value_sites[IPVK_LAST + 1];
+	const u32 num_bitmap_bytes;
+} __aligned(INSTR_PROF_DATA_ALIGNMENT);
+
+/* Payload sections */
+
+extern struct __llvm_profile_data __llvm_prf_data_start[];
+extern struct __llvm_profile_data __llvm_prf_data_end[];
+
+extern u64 __llvm_prf_cnts_start[];
+extern u64 __llvm_prf_cnts_end[];
+
+extern char __llvm_prf_names_start[];
+extern char __llvm_prf_names_end[];
+
+extern char __llvm_prf_bits_start[];
+extern char __llvm_prf_bits_end[];
+
+#define __DEFINE_SECTION_SIZE(s)					\
+	static inline unsigned long __llvm_prf_ ## s ## _size(void)	\
+	{								\
+		unsigned long start =					\
+			(unsigned long)__llvm_prf_ ## s ## _start;	\
+		unsigned long end =					\
+			(unsigned long)__llvm_prf_ ## s ## _end;	\
+		return end - start;					\
+	}
+#define __DEFINE_SECTION_COUNT(s)					\
+	static inline unsigned long __llvm_prf_ ## s ## _count(void)	\
+	{								\
+		return __llvm_prf_ ## s ## _size() /			\
+			sizeof(__llvm_prf_ ## s ## _start[0]);		\
+	}
+
+__DEFINE_SECTION_SIZE(data)
+__DEFINE_SECTION_SIZE(cnts)
+__DEFINE_SECTION_SIZE(names)
+__DEFINE_SECTION_SIZE(bits)
+
+__DEFINE_SECTION_COUNT(data)
+__DEFINE_SECTION_COUNT(cnts)
+__DEFINE_SECTION_COUNT(names)
+__DEFINE_SECTION_COUNT(bits)
+
+#undef __DEFINE_SECTION_SIZE
+#undef __DEFINE_SECTION_COUNT
+
+static inline unsigned long __llvm_prf_get_padding(unsigned long size)
+{
+	return 7 & (sizeof(u64) - size % sizeof(u64));
+}
+
+#endif /* _LLVM_COV_H */
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index fe3668dc4954..b9ceaee34b28 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -158,6 +158,16 @@  _c_flags += $(if $(patsubst n%,, \
 		$(CFLAGS_GCOV))
 endif
 
+#
+# Enable Clang's Source-based Code Coverage flags for a file or directory
+# depending on variables LLVM_COV_PROFILE_obj.o and LLVM_COV_PROFILE.
+#
+ifeq ($(CONFIG_LLVM_COV_KERNEL),y)
+_c_flags += $(if $(patsubst n%,, \
+		$(LLVM_COV_PROFILE_$(basetarget).o)$(LLVM_COV_PROFILE)y), \
+		$(CFLAGS_LLVM_COV))
+endif
+
 #
 # Enable address sanitizer flags for kernel except some files or directories
 # we don't want to check (depends on variables KASAN_SANITIZE_obj.o, KASAN_SANITIZE)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index d16d0ace2775..836c2289b8d8 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -743,6 +743,8 @@  static const char *const section_white_list[] =
 	".gnu.lto*",
 	".discard.*",
 	".llvm.call-graph-profile",	/* call graph */
+	"__llvm_covfun",
+	"__llvm_covmap",
 	NULL
 };