gcov support

add gcov support and export results as files in debugfs

Reviewed by:	hps@
MFC after:	1 week
Sponsored by:	iX Systems
Differential Revision:	https://reviews.freebsd.org/D19260

10 files changed, 1842 insertions, 1 deletions

diff --git a/sys/conf/files b/sys/conf/files
index c12d4f38bac0..51fba1c8270f 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -3726,6 +3726,11 @@ fs/cd9660/cd9660_util.c	optional cd9660
 fs/cd9660/cd9660_vfsops.c	optional cd9660
 fs/cd9660/cd9660_vnops.c	optional cd9660
 fs/cd9660/cd9660_iconv.c	optional cd9660_iconv
+gnu/gcov/gcc_4_7.c		optional gcov
+gnu/gcov/gcov_fs.c		optional gcov  lindebugfs \
+	compile-with "${LINUXKPI_C}"
+gnu/gcov/gcov_subr.c		optional gcov
+
 kern/bus_if.m			standard
 kern/clock_if.m			standard
 kern/cpufreq_if.m		standard
@@ -4475,6 +4480,12 @@ compat/linuxkpi/common/src/linux_usb.c		optional compat_linuxkpi usb \
 compat/linuxkpi/common/src/linux_work.c		optional compat_linuxkpi \
 	compile-with "${LINUXKPI_C}"
 
+compat/linuxkpi/common/src/linux_seq_file.c		optional compat_linuxkpi | lindebugfs \
+	compile-with "${LINUXKPI_C}"
+
+compat/lindebugfs/lindebugfs.c			optional lindebugfs \
+	compile-with "${LINUXKPI_C}"
+
 # OpenFabrics Enterprise Distribution (Infiniband)
 ofed/drivers/infiniband/core/ib_addr.c			optional ofed	\
 	compile-with "${OFED_C}"
diff --git a/sys/conf/kern.mk b/sys/conf/kern.mk
index 398df66f66fd..5803f8bb1bc2 100644
--- a/sys/conf/kern.mk
+++ b/sys/conf/kern.mk
@@ -56,7 +56,7 @@ CWARNEXTRA?=	-Wno-error=address				\
 		-Wno-error=maybe-uninitialized			\
 		-Wno-error=overflow				\
 		-Wno-error=sequence-point			\
-		-Wno-error=unused-but-set-variable
+		-Wno-unused-but-set-variable
 .if ${COMPILER_VERSION} >= 60100
 CWARNEXTRA+=	-Wno-error=misleading-indentation		\
 		-Wno-error=nonnull-compare			\
diff --git a/sys/conf/kern.post.mk b/sys/conf/kern.post.mk
index 398dc7165984..5a0dcb6e1ee0 100644
--- a/sys/conf/kern.post.mk
+++ b/sys/conf/kern.post.mk
@@ -32,6 +32,10 @@ MKMODULESENV+=	WITH_EXTRA_TCP_STACKS="${WITH_EXTRA_TCP_STACKS}"
 MKMODULESENV+=	SAN_CFLAGS="${SAN_CFLAGS}"
 .endif
 
+.if defined(GCOV_CFLAGS)
+MKMODULESENV+=	GCOV_CFLAGS="${GCOV_CFLAGS}"
+.endif
+
 # Allow overriding the kernel debug directory, so kernel and user debug may be
 # installed in different directories. Setting it to "" restores the historical
 # behavior of installing debug files in the kernel directory.
diff --git a/sys/conf/kern.pre.mk b/sys/conf/kern.pre.mk
index 407bfee936c9..f34329268c52 100644
--- a/sys/conf/kern.pre.mk
+++ b/sys/conf/kern.pre.mk
@@ -130,6 +130,15 @@ SAN_CFLAGS+=	-fsanitize-coverage=trace-pc
 
 CFLAGS+=	${SAN_CFLAGS}
 
+GCOV_ENABLED!=	grep GCOV opt_global.h || true ; echo
+.if !empty(GCOV_ENABLED)
+.if ${COMPILER_TYPE} == "gcc"
+GCOV_CFLAGS+=	 -fprofile-arcs -ftest-coverage
+.endif
+.endif
+
+CFLAGS+=	${GCOV_CFLAGS}
+
 # Put configuration-specific C flags last (except for ${PROF}) so that they
 # can override the others.
 CFLAGS+=	${CONF_CFLAGS}
diff --git a/sys/conf/kmod.mk b/sys/conf/kmod.mk
index 4f239d10bd3a..3a3e19456a88 100644
--- a/sys/conf/kmod.mk
+++ b/sys/conf/kmod.mk
@@ -380,6 +380,9 @@ ${_src}:
 # Add the sanitizer C flags
 CFLAGS+=	${SAN_CFLAGS}
 
+# Add the gcov flags
+CFLAGS+=	${GCOV_CFLAGS}
+
 # Respect configuration-specific C flags.
 CFLAGS+=	${ARCH_FLAGS} ${CONF_CFLAGS}
 
diff --git a/sys/conf/options b/sys/conf/options
index c0ef70f26541..d26f88e17157 100644
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -1013,3 +1013,7 @@ NVME_USE_NVD	opt_nvme.h
 
 # amdsbwd options
 AMDSBWD_DEBUG	opt_amdsbwd.h
+
+# gcov support
+GCOV		opt_global.h
+LINDEBUGFS
diff --git a/sys/gnu/gcov/gcc_4_7.c b/sys/gnu/gcov/gcc_4_7.c
new file mode 100644
index 000000000000..7d56c0257b01
--- /dev/null
+++ b/sys/gnu/gcov/gcc_4_7.c
@@ -0,0 +1,597 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  This code provides functions to handle gcc's profiling data format
+ *  introduced with gcc 4.7.
+ *
+ *  This file is based heavily on gcc_3_4.c file.
+ *
+ *  For a better understanding, refer to gcc source:
+ *  gcc/gcov-io.h
+ *  libgcc/libgcov.c
+ *
+ *  Uses gcc-internal data definitions.
+ */
+
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/types.h>
+#include <sys/systm.h>
+#include <sys/sbuf.h>
+#include <sys/malloc.h>
+#include <sys/module.h>
+#include <gnu/gcov/gcov.h>
+
+
+#if (__GNUC__ >= 7)
+#define GCOV_COUNTERS			9
+#elif (__GNUC__ > 5) || (__GNUC__ == 5 && __GNUC_MINOR__ >= 1)
+#define GCOV_COUNTERS			10
+#elif __GNUC__ == 4 && __GNUC_MINOR__ >= 9
+#define GCOV_COUNTERS			9
+#else
+#define GCOV_COUNTERS			8
+#endif
+
+#define GCOV_TAG_FUNCTION_LENGTH	3
+
+static struct gcov_info *gcov_info_head;
+
+/**
+ * struct gcov_ctr_info - information about counters for a single function
+ * @num: number of counter values for this type
+ * @values: array of counter values for this type
+ *
+ * This data is generated by gcc during compilation and doesn't change
+ * at run-time with the exception of the values array.
+ */
+struct gcov_ctr_info {
+	unsigned int num;
+	gcov_type *values;
+};
+
+/**
+ * struct gcov_fn_info - profiling meta data per function
+ * @key: comdat key
+ * @ident: unique ident of function
+ * @lineno_checksum: function lineo_checksum
+ * @cfg_checksum: function cfg checksum
+ * @ctrs: instrumented counters
+ *
+ * This data is generated by gcc during compilation and doesn't change
+ * at run-time.
+ *
+ * Information about a single function.  This uses the trailing array
+ * idiom. The number of counters is determined from the merge pointer
+ * array in gcov_info.  The key is used to detect which of a set of
+ * comdat functions was selected -- it points to the gcov_info object
+ * of the object file containing the selected comdat function.
+ */
+struct gcov_fn_info {
+	const struct gcov_info *key;
+	unsigned int ident;
+	unsigned int lineno_checksum;
+	unsigned int cfg_checksum;
+	struct gcov_ctr_info ctrs[0];
+};
+
+/**
+ * struct gcov_info - profiling data per object file
+ * @version: gcov version magic indicating the gcc version used for compilation
+ * @next: list head for a singly-linked list
+ * @stamp: uniquifying time stamp
+ * @filename: name of the associated gcov data file
+ * @merge: merge functions (null for unused counter type)
+ * @n_functions: number of instrumented functions
+ * @functions: pointer to pointers to function information
+ *
+ * This data is generated by gcc during compilation and doesn't change
+ * at run-time with the exception of the next pointer.
+ */
+struct gcov_info {
+	unsigned int version;
+	struct gcov_info *next;
+	unsigned int stamp;
+	const char *filename;
+	void (*merge[GCOV_COUNTERS])(gcov_type *, unsigned int);
+	unsigned int n_functions;
+	struct gcov_fn_info **functions;
+};
+
+/**
+ * gcov_info_filename - return info filename
+ * @info: profiling data set
+ */
+const char *
+gcov_info_filename(struct gcov_info *info)
+{
+	return (info->filename);
+}
+
+/**
+ * gcov_info_version - return info version
+ * @info: profiling data set
+ */
+unsigned int
+gcov_info_version(struct gcov_info *info)
+{
+	return (info->version);
+}
+
+/**
+ * gcov_info_next - return next profiling data set
+ * @info: profiling data set
+ *
+ * Returns next gcov_info following @info or first gcov_info in the chain if
+ * @info is %NULL.
+ */
+struct gcov_info *
+gcov_info_next(struct gcov_info *info)
+{
+	if (!info)
+		return gcov_info_head;
+
+	return (info->next);
+}
+
+/**
+ * gcov_info_link - link/add profiling data set to the list
+ * @info: profiling data set
+ */
+void
+gcov_info_link(struct gcov_info *info)
+{
+	info->next = gcov_info_head;
+	gcov_info_head = info;
+}
+
+/**
+ * gcov_info_unlink - unlink/remove profiling data set from the list
+ * @prev: previous profiling data set
+ * @info: profiling data set
+ */
+void
+gcov_info_unlink(struct gcov_info *prev, struct gcov_info *info)
+{
+	if (prev)
+		prev->next = info->next;
+	else
+		gcov_info_head = info->next;
+}
+
+/* Symbolic links to be created for each profiling data file. */
+const struct gcov_link gcov_link[] = {
+	{ OBJ_TREE, "gcno" },	/* Link to .gcno file in $(objtree). */
+	{ 0, NULL},
+};
+
+/*
+ * Determine whether a counter is active. Doesn't change at run-time.
+ */
+static int
+counter_active(struct gcov_info *info, unsigned int type)
+{
+	return (info->merge[type] ? 1 : 0);
+}
+
+/* Determine number of active counters. Based on gcc magic. */
+static unsigned int
+num_counter_active(struct gcov_info *info)
+{
+	unsigned int i;
+	unsigned int result = 0;
+
+	for (i = 0; i < GCOV_COUNTERS; i++) {
+		if (counter_active(info, i))
+			result++;
+	}
+	return (result);
+}
+
+/**
+ * gcov_info_reset - reset profiling data to zero
+ * @info: profiling data set
+ */
+void
+gcov_info_reset(struct gcov_info *info)
+{
+	struct gcov_ctr_info *ci_ptr;
+	unsigned int fi_idx;
+	unsigned int ct_idx;
+
+	for (fi_idx = 0; fi_idx < info->n_functions; fi_idx++) {
+		ci_ptr = info->functions[fi_idx]->ctrs;
+
+		for (ct_idx = 0; ct_idx < GCOV_COUNTERS; ct_idx++) {
+			if (!counter_active(info, ct_idx))
+				continue;
+
+			memset(ci_ptr->values, 0,
+					sizeof(gcov_type) * ci_ptr->num);
+			ci_ptr++;
+		}
+	}
+}
+
+/**
+ * gcov_info_is_compatible - check if profiling data can be added
+ * @info1: first profiling data set
+ * @info2: second profiling data set
+ *
+ * Returns non-zero if profiling data can be added, zero otherwise.
+ */
+int
+gcov_info_is_compatible(struct gcov_info *info1, struct gcov_info *info2)
+{
+	return (info1->stamp == info2->stamp);
+}
+
+/**
+ * gcov_info_add - add up profiling data
+ * @dest: profiling data set to which data is added
+ * @source: profiling data set which is added
+ *
+ * Adds profiling counts of @source to @dest.
+ */
+void
+gcov_info_add(struct gcov_info *dst, struct gcov_info *src)
+{
+	struct gcov_ctr_info *dci_ptr;
+	struct gcov_ctr_info *sci_ptr;
+	unsigned int fi_idx;
+	unsigned int ct_idx;
+	unsigned int val_idx;
+
+	for (fi_idx = 0; fi_idx < src->n_functions; fi_idx++) {
+		dci_ptr = dst->functions[fi_idx]->ctrs;
+		sci_ptr = src->functions[fi_idx]->ctrs;
+
+		for (ct_idx = 0; ct_idx < GCOV_COUNTERS; ct_idx++) {
+			if (!counter_active(src, ct_idx))
+				continue;
+
+			for (val_idx = 0; val_idx < sci_ptr->num; val_idx++)
+				dci_ptr->values[val_idx] +=
+					sci_ptr->values[val_idx];
+
+			dci_ptr++;
+			sci_ptr++;
+		}
+	}
+}
+
+/**
+ * gcov_info_dup - duplicate profiling data set
+ * @info: profiling data set to duplicate
+ *
+ * Return newly allocated duplicate on success, %NULL on error.
+ */
+struct gcov_info *
+gcov_info_dup(struct gcov_info *info)
+{
+	struct gcov_info *dup;
+	struct gcov_ctr_info *dci_ptr; /* dst counter info */
+	struct gcov_ctr_info *sci_ptr; /* src counter info */
+	unsigned int active;
+	unsigned int fi_idx; /* function info idx */
+	unsigned int ct_idx; /* counter type idx */
+	size_t fi_size; /* function info size */
+	size_t cv_size; /* counter values size */
+
+	if ((dup = malloc(sizeof(*dup), M_GCOV, M_NOWAIT|M_ZERO)) == NULL)
+		return (NULL);
+	memcpy(dup, info, sizeof(*dup));
+
+	dup->next = NULL;
+	dup->filename = NULL;
+	dup->functions = NULL;
+
+	dup->filename = strdup_flags(info->filename, M_GCOV, M_NOWAIT);
+	if (dup->filename == NULL)
+		goto err_free;
+
+	dup->functions = malloc(info->n_functions * sizeof(struct gcov_fn_info *), M_GCOV, M_NOWAIT|M_ZERO);
+	if (dup->functions == NULL)
+		goto err_free;
+	active = num_counter_active(info);
+	fi_size = sizeof(struct gcov_fn_info);
+	fi_size += sizeof(struct gcov_ctr_info) * active;
+
+	for (fi_idx = 0; fi_idx < info->n_functions; fi_idx++) {
+		dup->functions[fi_idx] = malloc(fi_size, M_GCOV, M_NOWAIT|M_ZERO);
+		if (!dup->functions[fi_idx])
+			goto err_free;
+
+		*(dup->functions[fi_idx]) = *(info->functions[fi_idx]);
+
+		sci_ptr = info->functions[fi_idx]->ctrs;
+		dci_ptr = dup->functions[fi_idx]->ctrs;
+
+		for (ct_idx = 0; ct_idx < active; ct_idx++) {
+
+			cv_size = sizeof(gcov_type) * sci_ptr->num;
+
+			dci_ptr->values = malloc(cv_size, M_GCOV, M_NOWAIT);
+
+			if (!dci_ptr->values)
+				goto err_free;
+
+			dci_ptr->num = sci_ptr->num;
+			memcpy(dci_ptr->values, sci_ptr->values, cv_size);
+
+			sci_ptr++;
+			dci_ptr++;
+		}
+	}
+
+	return (dup);
+err_free:
+	gcov_info_free(dup);
+	return (NULL);
+}
+
+/**
+ * gcov_info_free - release memory for profiling data set duplicate
+ * @info: profiling data set duplicate to free
+ */
+void
+gcov_info_free(struct gcov_info *info)
+{
+	unsigned int active;
+	unsigned int fi_idx;
+	unsigned int ct_idx;
+	struct gcov_ctr_info *ci_ptr;
+
+	if (!info->functions)
+		goto free_info;
+
+	active = num_counter_active(info);
+
+	for (fi_idx = 0; fi_idx < info->n_functions; fi_idx++) {
+		if (!info->functions[fi_idx])
+			continue;
+
+		ci_ptr = info->functions[fi_idx]->ctrs;
+
+		for (ct_idx = 0; ct_idx < active; ct_idx++, ci_ptr++)
+			free(ci_ptr->values, M_GCOV);
+
+		free(info->functions[fi_idx], M_GCOV);
+	}
+
+free_info:
+	free(info->functions, M_GCOV);
+	free(__DECONST(char *, info->filename), M_GCOV);
+	free(info, M_GCOV);
+ }
+
+#define ITER_STRIDE	PAGE_SIZE
+
+/**
+ * struct gcov_iterator - specifies current file position in logical records
+ * @info: associated profiling data
+ * @buffer: buffer containing file data
+ * @size: size of buffer
+ * @pos: current position in file
+ */
+struct gcov_iterator {
+	struct gcov_info *info;
+	caddr_t buffer;
+	size_t size;
+	off_t pos;
+};
+
+/**
+ * store_gcov_uint32 - store 32 bit number in gcov format to buffer
+ * @buffer: target buffer or NULL
+ * @off: offset into the buffer
+ * @v: value to be stored
+ *
+ * Number format defined by gcc: numbers are recorded in the 32 bit
+ * unsigned binary form of the endianness of the machine generating the
+ * file. Returns the number of bytes stored. If @buffer is %NULL, doesn't
+ * store anything.
+ */
+static size_t
+store_gcov_uint32(void *buffer, size_t off, uint32_t v)
+{
+	uint32_t *data;
+
+	if (buffer) {
+		data = (void*)((caddr_t)buffer + off);
+		*data = v;
+	}
+
+	return sizeof(*data);
+}
+
+/**
+ * store_gcov_uint64 - store 64 bit number in gcov format to buffer
+ * @buffer: target buffer or NULL
+ * @off: offset into the buffer
+ * @v: value to be stored
+ *
+ * Number format defined by gcc: numbers are recorded in the 32 bit
+ * unsigned binary form of the endianness of the machine generating the
+ * file. 64 bit numbers are stored as two 32 bit numbers, the low part
+ * first. Returns the number of bytes stored. If @buffer is %NULL, doesn't store
+ * anything.
+ */
+
+static size_t
+store_gcov_uint64(void *buffer, size_t off, uint64_t v)
+{
+	uint32_t *data;
+
+	if (buffer) {
+		data = (void*)((caddr_t)buffer + off);
+
+		data[0] = (v & 0xffffffffUL);
+		data[1] = (v >> 32);
+	}
+
+	return sizeof(*data) * 2;
+}
+
+/**
+ * convert_to_gcda - convert profiling data set to gcda file format
+ * @buffer: the buffer to store file data or %NULL if no data should be stored
+ * @info: profiling data set to be converted
+ *
+ * Returns the number of bytes that were/would have been stored into the buffer.
+ */
+static size_t
+convert_to_gcda(char *buffer, struct gcov_info *info)
+{
+	struct gcov_fn_info *fi_ptr;
+	struct gcov_ctr_info *ci_ptr;
+	unsigned int fi_idx;
+	unsigned int ct_idx;
+	unsigned int cv_idx;
+	size_t pos = 0;
+
+	/* File header. */
+	pos += store_gcov_uint32(buffer, pos, GCOV_DATA_MAGIC);
+	pos += store_gcov_uint32(buffer, pos, info->version);
+	pos += store_gcov_uint32(buffer, pos, info->stamp);
+
+	for (fi_idx = 0; fi_idx < info->n_functions; fi_idx++) {
+		fi_ptr = info->functions[fi_idx];
+
+		/* Function record. */
+		pos += store_gcov_uint32(buffer, pos, GCOV_TAG_FUNCTION);
+		pos += store_gcov_uint32(buffer, pos, GCOV_TAG_FUNCTION_LENGTH);
+		pos += store_gcov_uint32(buffer, pos, fi_ptr->ident);
+		pos += store_gcov_uint32(buffer, pos, fi_ptr->lineno_checksum);
+		pos += store_gcov_uint32(buffer, pos, fi_ptr->cfg_checksum);
+
+		ci_ptr = fi_ptr->ctrs;
+
+		for (ct_idx = 0; ct_idx < GCOV_COUNTERS; ct_idx++) {
+			if (!counter_active(info, ct_idx))
+				continue;
+
+			/* Counter record. */
+			pos += store_gcov_uint32(buffer, pos,
+					      GCOV_TAG_FOR_COUNTER(ct_idx));
+			pos += store_gcov_uint32(buffer, pos, ci_ptr->num * 2);
+
+			for (cv_idx = 0; cv_idx < ci_ptr->num; cv_idx++) {
+				pos += store_gcov_uint64(buffer, pos,
+						      ci_ptr->values[cv_idx]);
+			}
+
+			ci_ptr++;
+		}
+	}
+
+	return (pos);
+}
+
+/**
+ * gcov_iter_new - allocate and initialize profiling data iterator
+ * @info: profiling data set to be iterated
+ *
+ * Return file iterator on success, %NULL otherwise.
+ */
+struct gcov_iterator *
+gcov_iter_new(struct gcov_info *info)
+{
+	struct gcov_iterator *iter;
+
+	iter = malloc(sizeof(struct gcov_iterator), M_GCOV, M_NOWAIT|M_ZERO);
+	if (iter == NULL)
+		goto err_free;
+
+	iter->info = info;
+	/* Dry-run to get the actual buffer size. */
+	iter->size = convert_to_gcda(NULL, info);
+	iter->buffer = malloc(iter->size, M_GCOV, M_NOWAIT);
+	if (!iter->buffer)
+		goto err_free;
+
+	convert_to_gcda(iter->buffer, info);
+
+	return iter;
+
+err_free:
+	free(iter, M_GCOV);
+	return (NULL);
+}
+
+
+/**
+ * gcov_iter_get_info - return profiling data set for given file iterator
+ * @iter: file iterator
+ */
+void
+gcov_iter_free(struct gcov_iterator *iter)
+{
+	free(iter->buffer, M_GCOV);
+	free(iter, M_GCOV);
+}
+
+/**
+ * gcov_iter_get_info - return profiling data set for given file iterator
+ * @iter: file iterator
+ */
+struct gcov_info *
+gcov_iter_get_info(struct gcov_iterator *iter)
+{
+	return (iter->info);
+}
+
+/**
+ * gcov_iter_start - reset file iterator to starting position
+ * @iter: file iterator
+ */
+void
+gcov_iter_start(struct gcov_iterator *iter)
+{
+	iter->pos = 0;
+}
+
+/**
+ * gcov_iter_next - advance file iterator to next logical record
+ * @iter: file iterator
+ *
+ * Return zero if new position is valid, non-zero if iterator has reached end.
+ */
+int
+gcov_iter_next(struct gcov_iterator *iter)
+{
+	if (iter->pos < iter->size)
+		iter->pos += ITER_STRIDE;
+
+	if (iter->pos >= iter->size)
+		return (EINVAL);
+
+	return 0;
+}
+
+/**
+ * gcov_iter_write - write data for current pos to seq_file
+ * @iter: file iterator
+ * @seq: seq_file handle
+ *
+ * Return zero on success, non-zero otherwise.
+ */
+int
+gcov_iter_write(struct gcov_iterator *iter, struct sbuf *sbuf)
+{
+	size_t len;
+
+	if (iter->pos >= iter->size)
+		return (EINVAL);
+
+	len = ITER_STRIDE;
+	if (iter->pos + len > iter->size)
+		len = iter->size - iter->pos;
+
+	sbuf_bcat(sbuf, iter->buffer + iter->pos, len);
+
+	return (0);
+}
diff --git a/sys/gnu/gcov/gcov.h b/sys/gnu/gcov/gcov.h
new file mode 100644
index 000000000000..3ee775dbfe77
--- /dev/null
+++ b/sys/gnu/gcov/gcov.h
@@ -0,0 +1,99 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2019, Matthew Macy <mmacy@freebsd.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ *
+ */
+
+#ifndef _SYS_GCOV_H_
+#define _SYS_GCOV_H_
+
+MALLOC_DECLARE(M_GCOV);
+
+/*
+ * Profiling data types used for gcc 3.4 and above - these are defined by
+ * gcc and need to be kept as close to the original definition as possible to
+ * remain compatible.
+ */
+#define GCOV_DATA_MAGIC		((unsigned int) 0x67636461)
+#define GCOV_TAG_FUNCTION	((unsigned int) 0x01000000)
+#define GCOV_TAG_COUNTER_BASE	((unsigned int) 0x01a10000)
+#define GCOV_TAG_FOR_COUNTER(count)					\
+	(GCOV_TAG_COUNTER_BASE + ((unsigned int) (count) << 17))
+
+typedef uint64_t gcov_type;
+
+/* Opaque gcov_info. The gcov structures can change as for example in gcc 4.7 so
+ * we cannot use full definition here and they need to be placed in gcc specific
+ * implementation of gcov. This also means no direct access to the members in
+ * generic code and usage of the interface below.*/
+struct gcov_info;
+
+/* Interface to access gcov_info data  */
+const char *gcov_info_filename(struct gcov_info *info);
+unsigned int gcov_info_version(struct gcov_info *info);
+struct gcov_info *gcov_info_next(struct gcov_info *info);
+void gcov_info_link(struct gcov_info *info);
+void gcov_info_unlink(struct gcov_info *prev, struct gcov_info *info);
+
+/* Base interface. */
+enum gcov_action {
+	GCOV_ADD,
+	GCOV_REMOVE,
+};
+
+/* Iterator control. */
+struct gcov_iterator;
+
+struct gcov_iterator *gcov_iter_new(struct gcov_info *info);
+void gcov_iter_free(struct gcov_iterator *iter);
+void gcov_iter_start(struct gcov_iterator *iter);
+int gcov_iter_next(struct gcov_iterator *iter);
+int gcov_iter_write(struct gcov_iterator *iter, struct sbuf *sbuf);
+struct gcov_info *gcov_iter_get_info(struct gcov_iterator *iter);
+
+/* gcov_info control. */
+void gcov_info_reset(struct gcov_info *info);
+int gcov_info_is_compatible(struct gcov_info *info1, struct gcov_info *info2);
+void gcov_info_add(struct gcov_info *dest, struct gcov_info *source);
+struct gcov_info *gcov_info_dup(struct gcov_info *info);
+void gcov_info_free(struct gcov_info *info);
+void gcov_stats_reset(void);
+void gcov_enable_events(void);
+void gcov_module_unload(void *, module_t);
+void gcov_fs_init(void);
+
+int within_module(vm_offset_t addr, module_t mod);
+
+struct gcov_link {
+	enum {
+		OBJ_TREE,
+		SRC_TREE,
+	} dir;
+	const char *ext;
+};
+extern const struct gcov_link gcov_link[];
+#endif
diff --git a/sys/gnu/gcov/gcov_fs.c b/sys/gnu/gcov/gcov_fs.c
new file mode 100644
index 000000000000..00f80ad249f2
--- /dev/null
+++ b/sys/gnu/gcov/gcov_fs.c
@@ -0,0 +1,945 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  This code exports profiling data as debugfs files to userspace.
+ *
+ *    Copyright IBM Corp. 2009
+ *    Author(s): Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
+ *
+ *    Uses gcc-internal data definitions.
+ *    Based on the gcov-kernel patch by:
+ *		 Hubertus Franke <frankeh@us.ibm.com>
+ *		 Nigel Hinds <nhinds@us.ibm.com>
+ *		 Rajan Ravindran <rajancr@us.ibm.com>
+ *		 Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
+ *		 Paul Larson
+ *		 Yi CDL Yang
+ */
+
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <sys/systm.h>
+#include <sys/param.h>
+#include <sys/sbuf.h>
+
+#include <sys/queue.h>
+#include <sys/linker.h>
+#include <sys/module.h>
+#include <sys/eventhandler.h>
+#include <sys/kernel.h>
+#include <sys/malloc.h>
+#include <sys/syslog.h>
+#include <sys/proc.h>
+#include <sys/sched.h>
+#include <sys/syslog.h>
+#include <sys/sysctl.h>
+#include <linux/debugfs.h>
+
+#include <gnu/gcov/gcov.h>
+#include <sys/queue.h>
+
+extern int gcov_events_enabled;
+static int gcov_persist;
+static struct mtx gcov_mtx;
+MTX_SYSINIT(gcov_init, &gcov_mtx, "gcov_mtx", MTX_DEF);
+MALLOC_DEFINE(M_GCOV, "gcov", "gcov");
+
+void __gcov_init(struct gcov_info *info);
+void __gcov_flush(void);
+void __gcov_merge_add(gcov_type *counters, unsigned int n_counters);
+void __gcov_merge_single(gcov_type *counters, unsigned int n_counters);
+void __gcov_merge_delta(gcov_type *counters, unsigned int n_counters);
+void __gcov_merge_ior(gcov_type *counters, unsigned int n_counters);
+void __gcov_merge_time_profile(gcov_type *counters, unsigned int n_counters);
+void __gcov_merge_icall_topn(gcov_type *counters, unsigned int n_counters);
+void __gcov_exit(void);
+
+static void gcov_event(enum gcov_action action, struct gcov_info *info);
+
+
+/*
+ * Private copy taken from libc
+ */
+static char *
+(basename)(char *path)
+{
+	char *ptr;
+
+	/*
+	 * If path is a null pointer or points to an empty string,
+	 * basename() shall return a pointer to the string ".".
+	 */
+	if (path == NULL || *path == '\0')
+		return (__DECONST(char *, "."));
+
+	/* Find end of last pathname component and null terminate it. */
+	ptr = path + strlen(path);
+	while (ptr > path + 1 && *(ptr - 1) == '/')
+		--ptr;
+	*ptr-- = '\0';
+
+	/* Find beginning of last pathname component. */
+	while (ptr > path && *(ptr - 1) != '/')
+		--ptr;
+	return (ptr);
+}
+
+/*
+ * __gcov_init is called by gcc-generated constructor code for each object
+ * file compiled with -fprofile-arcs.
+ */
+void
+__gcov_init(struct gcov_info *info)
+{
+	static unsigned int gcov_version;
+
+	mtx_lock(&gcov_mtx);
+	if (gcov_version == 0) {
+		gcov_version = gcov_info_version(info);
+		/*
+		 * Printing gcc's version magic may prove useful for debugging
+		 * incompatibility reports.
+		 */
+		log(LOG_INFO, "version magic: 0x%x\n", gcov_version);
+	}
+	/*
+	 * Add new profiling data structure to list and inform event
+	 * listener.
+	 */
+	gcov_info_link(info);
+	if (gcov_events_enabled)
+		gcov_event(GCOV_ADD, info);
+	mtx_unlock(&gcov_mtx);
+}
+
+/*
+ * These functions may be referenced by gcc-generated profiling code but serve
+ * no function for kernel profiling.
+ */
+void
+__gcov_flush(void)
+{
+	/* Unused. */
+}
+
+void
+__gcov_merge_add(gcov_type *counters, unsigned int n_counters)
+{
+	/* Unused. */
+}
+
+void
+__gcov_merge_single(gcov_type *counters, unsigned int n_counters)
+{
+	/* Unused. */
+}
+
+void
+__gcov_merge_delta(gcov_type *counters, unsigned int n_counters)
+{
+	/* Unused. */
+}
+
+void
+__gcov_merge_ior(gcov_type *counters, unsigned int n_counters)
+{
+	/* Unused. */
+}
+
+void
+__gcov_merge_time_profile(gcov_type *counters, unsigned int n_counters)
+{
+	/* Unused. */
+}
+
+void
+__gcov_merge_icall_topn(gcov_type *counters, unsigned int n_counters)
+{
+	/* Unused. */
+}
+
+void
+__gcov_exit(void)
+{
+	/* Unused. */
+}
+
+
+/**
+ * struct gcov_node - represents a debugfs entry
+ * @entry: list entry for parent's child node list
+ * @children: child nodes
+ * @all_entry: list entry for list of all nodes
+ * @parent: parent node
+ * @loaded_info: array of pointers to profiling data sets for loaded object
+ *   files.
+ * @num_loaded: number of profiling data sets for loaded object files.
+ * @unloaded_info: accumulated copy of profiling data sets for unloaded
+ *   object files. Used only when gcov_persist=1.
+ * @dentry: main debugfs entry, either a directory or data file
+ * @links: associated symbolic links
+ * @name: data file basename
+ *
+ * struct gcov_node represents an entity within the gcov/ subdirectory
+ * of debugfs. There are directory and data file nodes. The latter represent
+ * the actual synthesized data file plus any associated symbolic links which
+ * are needed by the gcov tool to work correctly.
+ */
+struct gcov_node {
+	LIST_ENTRY(gcov_node) children_entry;
+	LIST_ENTRY(gcov_node) all_entry;
+	struct {
+		struct gcov_node *lh_first;
+	} children;
+	struct gcov_node *parent;
+	struct gcov_info **loaded_info;
+	struct gcov_info *unloaded_info;
+	struct dentry *dentry;
+	struct dentry **links;
+	int num_loaded;
+	char name[0];
+};
+
+#ifdef notyet
+static const char objtree[] = OBJTREE;
+static const char srctree[] = SRCTREE;
+#else
+static const char objtree[] = "";
+static const char srctree[] = "";
+#endif
+static struct gcov_node root_node;
+static struct {
+	struct gcov_node *lh_first;
+} all_head;
+static struct mtx node_lock;
+MTX_SYSINIT(node_init, &node_lock, "node_lock", MTX_DEF);
+static void remove_node(struct gcov_node *node);
+
+/*
+ * seq_file.start() implementation for gcov data files. Note that the
+ * gcov_iterator interface is designed to be more restrictive than seq_file
+ * (no start from arbitrary position, etc.), to simplify the iterator
+ * implementation.
+ */
+static void *
+gcov_seq_start(struct seq_file *seq, off_t *pos)
+{
+	off_t i;
+
+	gcov_iter_start(seq->private);
+	for (i = 0; i < *pos; i++) {
+		if (gcov_iter_next(seq->private))
+			return NULL;
+	}
+	return seq->private;
+}
+
+/* seq_file.next() implementation for gcov data files. */
+static void *
+gcov_seq_next(struct seq_file *seq, void *data, off_t *pos)
+{
+	struct gcov_iterator *iter = data;
+
+	if (gcov_iter_next(iter))
+		return NULL;
+	(*pos)++;
+
+	return iter;
+}
+
+/* seq_file.show() implementation for gcov data files. */
+static int
+gcov_seq_show(struct seq_file *seq, void *data)
+{
+	struct gcov_iterator *iter = data;
+
+	if (gcov_iter_write(iter, seq->buf))
+		return (-EINVAL);
+	return (0);
+}
+
+static void
+gcov_seq_stop(struct seq_file *seq, void *data)
+{
+	/* Unused. */
+}
+
+static const struct seq_operations gcov_seq_ops = {
+	.start	= gcov_seq_start,
+	.next	= gcov_seq_next,
+	.show	= gcov_seq_show,
+	.stop	= gcov_seq_stop,
+};
+
+/*
+ * Return a profiling data set associated with the given node. This is
+ * either a data set for a loaded object file or a data set copy in case
+ * all associated object files have been unloaded.
+ */
+static struct gcov_info *
+get_node_info(struct gcov_node *node)
+{
+	if (node->num_loaded > 0)
+		return (node->loaded_info[0]);
+
+	return (node->unloaded_info);
+}
+
+/*
+ * Return a newly allocated profiling data set which contains the sum of
+ * all profiling data associated with the given node.
+ */
+static struct gcov_info *
+get_accumulated_info(struct gcov_node *node)
+{
+	struct gcov_info *info;
+	int i = 0;
+
+	if (node->unloaded_info)
+		info = gcov_info_dup(node->unloaded_info);
+	else
+		info = gcov_info_dup(node->loaded_info[i++]);
+	if (info == NULL)
+		return (NULL);
+	for (; i < node->num_loaded; i++)
+		gcov_info_add(info, node->loaded_info[i]);
+
+	return (info);
+}
+
+/*
+ * open() implementation for gcov data files. Create a copy of the profiling
+ * data set and initialize the iterator and seq_file interface.
+ */
+static int
+gcov_seq_open(struct inode *inode, struct file *file)
+{
+	struct gcov_node *node = inode->i_private;
+	struct gcov_iterator *iter;
+	struct seq_file *seq;
+	struct gcov_info *info;
+	int rc = -ENOMEM;
+
+	mtx_lock(&node_lock);
+	/*
+	 * Read from a profiling data copy to minimize reference tracking
+	 * complexity and concurrent access and to keep accumulating multiple
+	 * profiling data sets associated with one node simple.
+	 */
+	info = get_accumulated_info(node);
+	if (info == NULL)
+		goto out_unlock;
+	iter = gcov_iter_new(info);
+	if (iter == NULL)
+		goto err_free_info;
+	rc = seq_open(file, &gcov_seq_ops);
+	if (rc)
+		goto err_free_iter_info;
+	seq = file->private_data;
+	seq->private = iter;
+out_unlock:
+	mtx_unlock(&node_lock);
+	return (rc);
+
+err_free_iter_info:
+	gcov_iter_free(iter);
+err_free_info:
+	gcov_info_free(info);
+	goto out_unlock;
+}
+
+/*
+ * release() implementation for gcov data files. Release resources allocated
+ * by open().
+ */
+static int
+gcov_seq_release(struct inode *inode, struct file *file)
+{
+	struct gcov_iterator *iter;
+	struct gcov_info *info;
+	struct seq_file *seq;
+
+	seq = file->private_data;
+	iter = seq->private;
+	info = gcov_iter_get_info(iter);
+	gcov_iter_free(iter);
+	gcov_info_free(info);
+	seq_release(inode, file);
+
+	return (0);
+}
+
+/*
+ * Find a node by the associated data file name. Needs to be called with
+ * node_lock held.
+ */
+static struct gcov_node *
+get_node_by_name(const char *name)
+{
+	struct gcov_node *node;
+	struct gcov_info *info;
+
+	LIST_FOREACH(node, &all_head, all_entry) {
+		info = get_node_info(node);
+		if (info && (strcmp(gcov_info_filename(info), name) == 0))
+			return (node);
+	}
+
+	return (NULL);
+}
+
+/*
+ * Reset all profiling data associated with the specified node.
+ */
+static void
+reset_node(struct gcov_node *node)
+{
+	int i;
+
+	if (node->unloaded_info)
+		gcov_info_reset(node->unloaded_info);
+	for (i = 0; i < node->num_loaded; i++)
+		gcov_info_reset(node->loaded_info[i]);
+}
+
+void
+gcov_stats_reset(void)
+{
+	struct gcov_node *node;
+
+	mtx_lock(&node_lock);
+ restart:
+	LIST_FOREACH(node, &all_head, all_entry) {
+		if (node->num_loaded > 0)
+			reset_node(node);
+		else if (LIST_EMPTY(&node->children)) {
+			remove_node(node);
+			goto restart;
+		}
+	}
+	mtx_unlock(&node_lock);
+}
+
+/*
+ * write() implementation for gcov data files. Reset profiling data for the
+ * corresponding file. If all associated object files have been unloaded,
+ * remove the debug fs node as well.
+ */
+static ssize_t
+gcov_seq_write(struct file *file, const char *addr, size_t len, off_t *pos)
+{
+	struct seq_file *seq;
+	struct gcov_info *info;
+	struct gcov_node *node;
+
+	seq = file->private_data;
+	info = gcov_iter_get_info(seq->private);
+	mtx_lock(&node_lock);
+	node = get_node_by_name(gcov_info_filename(info));
+	if (node) {
+		/* Reset counts or remove node for unloaded modules. */
+		if (node->num_loaded == 0)
+			remove_node(node);
+		else
+			reset_node(node);
+	}
+	/* Reset counts for open file. */
+	gcov_info_reset(info);
+	mtx_unlock(&node_lock);
+
+	return (len);
+}
+
+/*
+ * Given a string <path> representing a file path of format:
+ *   path/to/file.gcda
+ * construct and return a new string:
+ *   <dir/>path/to/file.<ext>
+ */
+static char *
+link_target(const char *dir, const char *path, const char *ext)
+{
+	char *target;
+	char *old_ext;
+	char *copy;
+
+	copy = strdup_flags(path, M_GCOV, M_NOWAIT);
+	if (!copy)
+		return (NULL);
+	old_ext = strrchr(copy, '.');
+	if (old_ext)
+		*old_ext = '\0';
+	target = NULL;
+	if (dir)
+		asprintf(&target, M_GCOV, "%s/%s.%s", dir, copy, ext);
+	else
+		asprintf(&target, M_GCOV, "%s.%s", copy, ext);
+	free(copy, M_GCOV);
+
+	return (target);
+}
+
+/*
+ * Construct a string representing the symbolic link target for the given
+ * gcov data file name and link type. Depending on the link type and the
+ * location of the data file, the link target can either point to a
+ * subdirectory of srctree, objtree or in an external location.
+ */
+static char *
+get_link_target(const char *filename, const struct gcov_link *ext)
+{
+	const char *rel;
+	char *result;
+
+	if (strncmp(filename, objtree, strlen(objtree)) == 0) {
+		rel = filename + strlen(objtree) + 1;
+		if (ext->dir == SRC_TREE)
+			result = link_target(srctree, rel, ext->ext);
+		else
+			result = link_target(objtree, rel, ext->ext);
+	} else {
+		/* External compilation. */
+		result = link_target(NULL, filename, ext->ext);
+	}
+
+	return (result);
+}
+
+#define SKEW_PREFIX	".tmp_"
+
+/*
+ * For a filename .tmp_filename.ext return filename.ext. Needed to compensate
+ * for filename skewing caused by the mod-versioning mechanism.
+ */
+static const char *
+deskew(const char *basename)
+{
+	if (strncmp(basename, SKEW_PREFIX, sizeof(SKEW_PREFIX) - 1) == 0)
+		return (basename + sizeof(SKEW_PREFIX) - 1);
+	return (basename);
+}
+
+/*
+ * Create links to additional files (usually .c and .gcno files) which the
+ * gcov tool expects to find in the same directory as the gcov data file.
+ */
+static void
+add_links(struct gcov_node *node, struct dentry *parent)
+{
+	const char *path_basename;
+	char *target;
+	int num;
+	int i;
+
+	for (num = 0; gcov_link[num].ext; num++)
+		/* Nothing. */;
+	node->links = malloc((num*sizeof(struct dentry *)), M_GCOV, M_NOWAIT|M_ZERO);
+	if (node->links == NULL)
+		return;
+	for (i = 0; i < num; i++) {
+		target = get_link_target(
+				gcov_info_filename(get_node_info(node)),
+				&gcov_link[i]);
+		if (target == NULL)
+			goto out_err;
+		path_basename = basename(target);
+		if (path_basename == target)
+			goto out_err;
+		node->links[i] = debugfs_create_symlink(deskew(path_basename),
+							parent,	target);
+		if (!node->links[i])
+			goto out_err;
+		free(target, M_GCOV);
+	}
+
+	return;
+out_err:
+	free(target, M_GCOV);
+	while (i-- > 0)
+		debugfs_remove(node->links[i]);
+	free(node->links, M_GCOV);
+	node->links = NULL;
+}
+
+static const struct file_operations gcov_data_fops = {
+	.open		= gcov_seq_open,
+	.release	= gcov_seq_release,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.write		= gcov_seq_write,
+};
+
+/* Basic initialization of a new node. */
+static void
+init_node(struct gcov_node *node, struct gcov_info *info,
+   const char *name, struct gcov_node *parent)
+{
+	LIST_INIT(&node->children);
+	if (node->loaded_info) {
+		node->loaded_info[0] = info;
+		node->num_loaded = 1;
+	}
+	node->parent = parent;
+	if (name)
+		strcpy(node->name, name);
+}
+
+/*
+ * Create a new node and associated debugfs entry. Needs to be called with
+ * node_lock held.
+ */
+static struct gcov_node *
+new_node(struct gcov_node *parent, struct gcov_info *info, const char *name)
+{
+	struct gcov_node *node;
+
+	node = malloc(sizeof(struct gcov_node) + strlen(name) + 1, M_GCOV, M_NOWAIT|M_ZERO);
+	if (!node)
+		goto err_nomem;
+	if (info) {
+		node->loaded_info = malloc(sizeof(struct gcov_info *), M_GCOV, M_NOWAIT|M_ZERO);
+		if (!node->loaded_info)
+			goto err_nomem;
+	}
+	init_node(node, info, name, parent);
+	/* Differentiate between gcov data file nodes and directory nodes. */
+	if (info) {
+		node->dentry = debugfs_create_file(deskew(node->name), 0600,
+					parent->dentry, node, &gcov_data_fops);
+	} else
+		node->dentry = debugfs_create_dir(node->name, parent->dentry);
+	if (!node->dentry) {
+		log(LOG_WARNING, "could not create file\n");
+		free(node, M_GCOV);
+		return NULL;
+	}
+	if (info)
+		add_links(node, parent->dentry);
+	LIST_INSERT_HEAD(&parent->children, node, children_entry);
+	LIST_INSERT_HEAD(&all_head, node, all_entry);
+
+	return (node);
+
+err_nomem:
+	free(node, M_GCOV);
+	log(LOG_WARNING, "out of memory\n");
+	return NULL;
+}
+
+/* Remove symbolic links associated with node. */
+static void
+remove_links(struct gcov_node *node)
+{
+
+	if (node->links == NULL)
+		return;
+	for (int i = 0; gcov_link[i].ext; i++)
+		debugfs_remove(node->links[i]);
+	free(node->links, M_GCOV);
+	node->links = NULL;
+}
+
+/*
+ * Remove node from all lists and debugfs and release associated resources.
+ * Needs to be called with node_lock held.
+ */
+static void
+release_node(struct gcov_node *node)
+{
+	LIST_REMOVE(node, children_entry);
+	LIST_REMOVE(node, all_entry);
+	debugfs_remove(node->dentry);
+	remove_links(node);
+	free(node->loaded_info, M_GCOV);
+	if (node->unloaded_info)
+		gcov_info_free(node->unloaded_info);
+	free(node, M_GCOV);
+}
+
+/* Release node and empty parents. Needs to be called with node_lock held. */
+static void
+remove_node(struct gcov_node *node)
+{
+	struct gcov_node *parent;
+
+	while ((node != &root_node) && LIST_EMPTY(&node->children)) {
+		parent = node->parent;
+		release_node(node);
+		node = parent;
+	}
+}
+
+/*
+ * Find child node with given basename. Needs to be called with node_lock
+ * held.
+ */
+static struct gcov_node *
+get_child_by_name(struct gcov_node *parent, const char *name)
+{
+	struct gcov_node *node;
+
+	LIST_FOREACH(node, &parent->children, children_entry) {
+		if (strcmp(node->name, name) == 0)
+			return (node);
+	}
+
+	return (NULL);
+}
+
+/*
+ * Create a node for a given profiling data set and add it to all lists and
+ * debugfs. Needs to be called with node_lock held.
+ */
+static void
+add_node(struct gcov_info *info)
+{
+	char *filename;
+	char *curr;
+	char *next;
+	struct gcov_node *parent;
+	struct gcov_node *node;
+
+	filename = strdup_flags(gcov_info_filename(info), M_GCOV, M_NOWAIT);
+	if (filename == NULL)
+		return;
+	parent = &root_node;
+	/* Create directory nodes along the path. */
+	for (curr = filename; (next = strchr(curr, '/')); curr = next + 1) {
+		if (curr == next)
+			continue;
+		*next = 0;
+		if (strcmp(curr, ".") == 0)
+			continue;
+		if (strcmp(curr, "..") == 0) {
+			if (!parent->parent)
+				goto err_remove;
+			parent = parent->parent;
+			continue;
+		}
+		node = get_child_by_name(parent, curr);
+		if (!node) {
+			node = new_node(parent, NULL, curr);
+			if (!node)
+				goto err_remove;
+		}
+		parent = node;
+	}
+	/* Create file node. */
+	node = new_node(parent, info, curr);
+	if (!node)
+		goto err_remove;
+out:
+	free(filename, M_GCOV);
+	return;
+
+err_remove:
+	remove_node(parent);
+	goto out;
+}
+
+/*
+ * Associate a profiling data set with an existing node. Needs to be called
+ * with node_lock held.
+ */
+static void
+add_info(struct gcov_node *node, struct gcov_info *info)
+{
+	struct gcov_info **loaded_info;
+	int num = node->num_loaded;
+
+	/*
+	 * Prepare new array. This is done first to simplify cleanup in
+	 * case the new data set is incompatible, the node only contains
+	 * unloaded data sets and there's not enough memory for the array.
+	 */
+	loaded_info = malloc((num + 1)* sizeof(struct gcov_info *), M_GCOV, M_NOWAIT|M_ZERO);
+	if (!loaded_info) {
+		log(LOG_WARNING, "could not add '%s' (out of memory)\n",
+			gcov_info_filename(info));
+		return;
+	}
+	memcpy(loaded_info, node->loaded_info,
+	       num * sizeof(struct gcov_info *));
+	loaded_info[num] = info;
+	/* Check if the new data set is compatible. */
+	if (num == 0) {
+		/*
+		 * A module was unloaded, modified and reloaded. The new
+		 * data set replaces the copy of the last one.
+		 */
+		if (!gcov_info_is_compatible(node->unloaded_info, info)) {
+			log(LOG_WARNING, "discarding saved data for %s "
+				"(incompatible version)\n",
+				gcov_info_filename(info));
+			gcov_info_free(node->unloaded_info);
+			node->unloaded_info = NULL;
+		}
+	} else {
+		/*
+		 * Two different versions of the same object file are loaded.
+		 * The initial one takes precedence.
+		 */
+		if (!gcov_info_is_compatible(node->loaded_info[0], info)) {
+			log(LOG_WARNING, "could not add '%s' (incompatible "
+				"version)\n", gcov_info_filename(info));
+			free(loaded_info, M_GCOV);
+			return;
+		}
+	}
+	/* Overwrite previous array. */
+	free(node->loaded_info, M_GCOV);
+	node->loaded_info = loaded_info;
+	node->num_loaded = num + 1;
+}
+
+/*
+ * Return the index of a profiling data set associated with a node.
+ */
+static int
+get_info_index(struct gcov_node *node, struct gcov_info *info)
+{
+	int i;
+
+	for (i = 0; i < node->num_loaded; i++) {
+		if (node->loaded_info[i] == info)
+			return (i);
+	}
+	return (ENOENT);
+}
+
+/*
+ * Save the data of a profiling data set which is being unloaded.
+ */
+static void
+save_info(struct gcov_node *node, struct gcov_info *info)
+{
+	if (node->unloaded_info)
+		gcov_info_add(node->unloaded_info, info);
+	else {
+		node->unloaded_info = gcov_info_dup(info);
+		if (!node->unloaded_info) {
+			log(LOG_WARNING, "could not save data for '%s' "
+				"(out of memory)\n",
+				gcov_info_filename(info));
+		}
+	}
+}
+
+/*
+ * Disassociate a profiling data set from a node. Needs to be called with
+ * node_lock held.
+ */
+static void
+remove_info(struct gcov_node *node, struct gcov_info *info)
+{
+	int i;
+
+	i = get_info_index(node, info);
+	if (i < 0) {
+		log(LOG_WARNING, "could not remove '%s' (not found)\n",
+			gcov_info_filename(info));
+		return;
+	}
+	if (gcov_persist)
+		save_info(node, info);
+	/* Shrink array. */
+	node->loaded_info[i] = node->loaded_info[node->num_loaded - 1];
+	node->num_loaded--;
+	if (node->num_loaded > 0)
+		return;
+	/* Last loaded data set was removed. */
+	free(node->loaded_info, M_GCOV);
+	node->loaded_info = NULL;
+	node->num_loaded = 0;
+	if (!node->unloaded_info)
+		remove_node(node);
+}
+
+/*
+ * Callback to create/remove profiling files when code compiled with
+ * -fprofile-arcs is loaded/unloaded.
+ */
+static void
+gcov_event(enum gcov_action action, struct gcov_info *info)
+{
+	struct gcov_node *node;
+
+	mtx_lock(&node_lock);
+	node = get_node_by_name(gcov_info_filename(info));
+	switch (action) {
+	case GCOV_ADD:
+		if (node)
+			add_info(node, info);
+		else
+			add_node(info);
+		break;
+	case GCOV_REMOVE:
+		if (node)
+			remove_info(node, info);
+		else {
+			log(LOG_WARNING, "could not remove '%s' (not found)\n",
+				gcov_info_filename(info));
+		}
+		break;
+	}
+	mtx_unlock(&node_lock);
+}
+
+/**
+ * gcov_enable_events - enable event reporting through gcov_event()
+ *
+ * Turn on reporting of profiling data load/unload-events through the
+ * gcov_event() callback. Also replay all previous events once. This function
+ * is needed because some events are potentially generated too early for the
+ * callback implementation to handle them initially.
+ */
+void
+gcov_enable_events(void)
+{
+	struct gcov_info *info = NULL;
+	int count;
+
+	mtx_lock(&gcov_mtx);
+	count = 0;
+
+	/* Perform event callback for previously registered entries. */
+	while ((info = gcov_info_next(info))) {
+		gcov_event(GCOV_ADD, info);
+		sched_relinquish(curthread);
+		count++;
+	}
+
+	mtx_unlock(&gcov_mtx);
+	printf("%s found %d events\n", __func__, count);
+}
+
+/* Update list and generate events when modules are unloaded. */
+void
+gcov_module_unload(void *arg __unused, module_t mod)
+{
+	struct gcov_info *info = NULL;
+	struct gcov_info *prev = NULL;
+
+	mtx_lock(&gcov_mtx );
+
+	/* Remove entries located in module from linked list. */
+	while ((info = gcov_info_next(info))) {
+		if (within_module((vm_offset_t)info, mod)) {
+			gcov_info_unlink(prev, info);
+			if (gcov_events_enabled)
+				gcov_event(GCOV_REMOVE, info);
+		} else
+			prev = info;
+	}
+
+	mtx_unlock(&gcov_mtx);
+}
+
+void
+gcov_fs_init(void)
+{
+	init_node(&root_node, NULL, NULL, NULL);
+	root_node.dentry = debugfs_create_dir("gcov", NULL);
+}
diff --git a/sys/gnu/gcov/gcov_subr.c b/sys/gnu/gcov/gcov_subr.c
new file mode 100644
index 000000000000..8726cb3273ca
--- /dev/null
+++ b/sys/gnu/gcov/gcov_subr.c
@@ -0,0 +1,169 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2019, Matthew Macy <mmacy@freebsd.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <sys/systm.h>
+#include <sys/param.h>
+#include <sys/sbuf.h>
+
+#include <sys/queue.h>
+#include <sys/linker.h>
+#include <sys/module.h>
+#include <sys/eventhandler.h>
+#include <sys/kernel.h>
+#include <sys/malloc.h>
+#include <sys/syslog.h>
+#include <sys/proc.h>
+#include <sys/sched.h>
+#include <sys/syslog.h>
+#include <sys/sysctl.h>
+#include <gnu/gcov/gcov.h>
+#include <sys/queue.h>
+#include "linker_if.h"
+
+
+static void gcov_invoke_ctors(void);
+static int gcov_ctors_done;
+int gcov_events_enabled;
+
+static int
+gcov_stats_reset_sysctl(SYSCTL_HANDLER_ARGS)
+{
+	int error, v;
+
+	v = 0;
+	error = sysctl_handle_int(oidp, &v, 0, req);
+	if (error)
+		return (error);
+	if (req->newptr == NULL)
+		return (error);
+	if (v == 0)
+		return (0);
+	gcov_stats_reset();
+
+	return (0);
+}
+
+static int
+gcov_stats_enable_sysctl(SYSCTL_HANDLER_ARGS)
+{
+	int error, v;
+
+	v = gcov_events_enabled;
+	error = sysctl_handle_int(oidp, &v, v, req);
+	if (error)
+		return (error);
+	if (req->newptr == NULL)
+		return (error);
+	if (v == gcov_events_enabled)
+		return (0);
+	//gcov_events_reset();
+	gcov_events_enabled = !!v;
+	if (!gcov_ctors_done)
+		gcov_invoke_ctors();
+	if (gcov_events_enabled)
+		gcov_enable_events();
+
+	return (0);
+}
+
+int
+within_module(vm_offset_t addr, module_t mod)
+{
+	linker_file_t link_info;
+	vm_offset_t mod_addr;
+	size_t mod_size;
+
+	link_info = module_file(mod);
+	mod_addr = (vm_offset_t)link_info->address;
+	mod_size = link_info->size;
+	if (addr >= mod_addr && addr < mod_addr + mod_size)
+		return (1);
+	return (0);
+}
+
+
+
+#define GCOV_PREFIX "_GLOBAL__sub_I_65535_0_"
+
+static int
+gcov_invoke_ctor(const char *name, void *arg)
+{
+	void (*ctor)(void);
+	c_linker_sym_t sym;
+	linker_symval_t symval;
+	linker_file_t lf;
+
+	if (strstr(name, GCOV_PREFIX) == NULL)
+		return (0);
+	lf = arg;
+	LINKER_LOOKUP_SYMBOL(lf, name, &sym);
+	LINKER_SYMBOL_VALUES(lf, sym, &symval);
+	ctor = (void *)symval.value;
+	ctor();
+	return (0);
+}
+
+static int
+gcov_invoke_lf_ctors(linker_file_t lf, void *arg __unused)
+{
+
+	printf("%s processing file: %s\n", __func__, lf->filename);
+	LINKER_EACH_FUNCTION_NAME(lf, gcov_invoke_ctor, lf);
+	return (0);
+}
+
+static void
+gcov_invoke_ctors(void)
+{
+
+	gcov_fs_init();
+
+	linker_file_foreach(gcov_invoke_lf_ctors, NULL);
+	gcov_ctors_done = 1;
+}
+
+static int
+gcov_init(void *arg __unused)
+{
+	EVENTHANDLER_REGISTER(module_unload, gcov_module_unload, NULL, 0);
+	gcov_enable_events();
+	return (0);
+}
+
+SYSINIT(gcov_init, SI_SUB_EVENTHANDLER, SI_ORDER_ANY, gcov_init, NULL);
+
+static SYSCTL_NODE(_debug, OID_AUTO, gcov, CTLFLAG_RD, NULL,
+    "gcov code coverage");
+SYSCTL_PROC(_debug_gcov, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
+    NULL, 0, gcov_stats_reset_sysctl, "I", "Reset all profiling counts");
+SYSCTL_PROC(_debug_gcov, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
+    NULL, 0, gcov_stats_enable_sysctl, "I", "Enable code coverage");