Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 628 insertions, 0 deletions

diff --git a/fs/hfsplus/unicode.c b/fs/hfsplus/unicode.c
new file mode 100644
index 000000000..008fec186
--- /dev/null
+++ b/fs/hfsplus/unicode.c
@@ -0,0 +1,628 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/hfsplus/unicode.c
+ *
+ * Copyright (C) 2001
+ * Brad Boyer (flar@allandria.com)
+ * (C) 2003 Ardis Technologies <roman@ardistech.com>
+ *
+ * Handler routines for unicode strings
+ */
+
+#include <linux/types.h>
+#include <linux/nls.h>
+
+#include <kunit/visibility.h>
+
+#include "hfsplus_fs.h"
+#include "hfsplus_raw.h"
+
+/* Fold the case of a unicode char, given the 16 bit value */
+/* Returns folded char, or 0 if ignorable */
+static inline u16 case_fold(u16 c)
+{
+	u16 tmp;
+
+	tmp = hfsplus_case_fold_table[c >> 8];
+	if (tmp)
+		tmp = hfsplus_case_fold_table[tmp + (c & 0xff)];
+	else
+		tmp = c;
+	return tmp;
+}
+
+/* Compare unicode strings, return values like normal strcmp */
+int hfsplus_strcasecmp(const struct hfsplus_unistr *s1,
+		       const struct hfsplus_unistr *s2)
+{
+	u16 len1, len2, c1, c2;
+	const hfsplus_unichr *p1, *p2;
+
+	len1 = be16_to_cpu(s1->length);
+	len2 = be16_to_cpu(s2->length);
+	p1 = s1->unicode;
+	p2 = s2->unicode;
+
+	if (len1 > HFSPLUS_MAX_STRLEN) {
+		len1 = HFSPLUS_MAX_STRLEN;
+		pr_err("invalid length %u has been corrected to %d\n",
+			be16_to_cpu(s1->length), len1);
+	}
+
+	if (len2 > HFSPLUS_MAX_STRLEN) {
+		len2 = HFSPLUS_MAX_STRLEN;
+		pr_err("invalid length %u has been corrected to %d\n",
+			be16_to_cpu(s2->length), len2);
+	}
+
+	while (1) {
+		c1 = c2 = 0;
+
+		while (len1 && !c1) {
+			c1 = case_fold(be16_to_cpu(*p1));
+			p1++;
+			len1--;
+		}
+		while (len2 && !c2) {
+			c2 = case_fold(be16_to_cpu(*p2));
+			p2++;
+			len2--;
+		}
+
+		if (c1 != c2)
+			return (c1 < c2) ? -1 : 1;
+		if (!c1 && !c2)
+			return 0;
+	}
+}
+EXPORT_SYMBOL_IF_KUNIT(hfsplus_strcasecmp);
+
+/* Compare names as a sequence of 16-bit unsigned integers */
+int hfsplus_strcmp(const struct hfsplus_unistr *s1,
+		   const struct hfsplus_unistr *s2)
+{
+	u16 len1, len2, c1, c2;
+	const hfsplus_unichr *p1, *p2;
+	int len;
+
+	len1 = be16_to_cpu(s1->length);
+	len2 = be16_to_cpu(s2->length);
+	p1 = s1->unicode;
+	p2 = s2->unicode;
+
+	if (len1 > HFSPLUS_MAX_STRLEN) {
+		len1 = HFSPLUS_MAX_STRLEN;
+		pr_err("invalid length %u has been corrected to %d\n",
+			be16_to_cpu(s1->length), len1);
+	}
+
+	if (len2 > HFSPLUS_MAX_STRLEN) {
+		len2 = HFSPLUS_MAX_STRLEN;
+		pr_err("invalid length %u has been corrected to %d\n",
+			be16_to_cpu(s2->length), len2);
+	}
+
+	for (len = min(len1, len2); len > 0; len--) {
+		c1 = be16_to_cpu(*p1);
+		c2 = be16_to_cpu(*p2);
+		if (c1 != c2)
+			return c1 < c2 ? -1 : 1;
+		p1++;
+		p2++;
+	}
+
+	return len1 < len2 ? -1 :
+	       len1 > len2 ? 1 : 0;
+}
+EXPORT_SYMBOL_IF_KUNIT(hfsplus_strcmp);
+
+#define Hangul_SBase	0xac00
+#define Hangul_LBase	0x1100
+#define Hangul_VBase	0x1161
+#define Hangul_TBase	0x11a7
+#define Hangul_SCount	11172
+#define Hangul_LCount	19
+#define Hangul_VCount	21
+#define Hangul_TCount	28
+#define Hangul_NCount	(Hangul_VCount * Hangul_TCount)
+
+
+static u16 *hfsplus_compose_lookup(u16 *p, u16 cc)
+{
+	int i, s, e;
+
+	s = 1;
+	e = p[1];
+	if (!e || cc < p[s * 2] || cc > p[e * 2])
+		return NULL;
+	do {
+		i = (s + e) / 2;
+		if (cc > p[i * 2])
+			s = i + 1;
+		else if (cc < p[i * 2])
+			e = i - 1;
+		else
+			return hfsplus_compose_table + p[i * 2 + 1];
+	} while (s <= e);
+	return NULL;
+}
+
+/*
+ * In HFS+, a filename can contain / because : is the separator.
+ * The slash is a valid filename character on macOS.
+ * But on Linux, / is the path separator and
+ * it cannot appear in a filename component.
+ * There's a parallel mapping for the NUL character (0 -> U+2400).
+ * NUL terminates strings in C/POSIX but is valid in HFS+ filenames.
+ */
+static inline
+void hfsplus_mac2linux_compatibility_check(u16 symbol, u16 *conversion,
+					   int name_type)
+{
+	*conversion = symbol;
+
+	switch (name_type) {
+	case HFS_XATTR_NAME:
+		/* ignore conversion */
+		return;
+
+	default:
+		/* continue logic */
+		break;
+	}
+
+	switch (symbol) {
+	case 0:
+		*conversion = 0x2400;
+		break;
+	case '/':
+		*conversion = ':';
+		break;
+	}
+}
+
+static int hfsplus_uni2asc(struct super_block *sb,
+			   const struct hfsplus_unistr *ustr,
+			   int max_len, char *astr, int *len_p,
+			   int name_type)
+{
+	const hfsplus_unichr *ip;
+	struct nls_table *nls = HFSPLUS_SB(sb)->nls;
+	u8 *op;
+	u16 cc, c0, c1;
+	u16 *ce1, *ce2;
+	int i, len, ustrlen, res, compose;
+
+	op = astr;
+	ip = ustr->unicode;
+
+	ustrlen = be16_to_cpu(ustr->length);
+	if (ustrlen > max_len) {
+		ustrlen = max_len;
+		pr_err("invalid length %u has been corrected to %d\n",
+			be16_to_cpu(ustr->length), ustrlen);
+	}
+
+	len = *len_p;
+	ce1 = NULL;
+	compose = !test_bit(HFSPLUS_SB_NODECOMPOSE, &HFSPLUS_SB(sb)->flags);
+
+	while (ustrlen > 0) {
+		c0 = be16_to_cpu(*ip++);
+		ustrlen--;
+		/* search for single decomposed char */
+		if (likely(compose))
+			ce1 = hfsplus_compose_lookup(hfsplus_compose_table, c0);
+		if (ce1)
+			cc = ce1[0];
+		else
+			cc = 0;
+		if (cc) {
+			/* start of a possibly decomposed Hangul char */
+			if (cc != 0xffff)
+				goto done;
+			if (!ustrlen)
+				goto same;
+			c1 = be16_to_cpu(*ip) - Hangul_VBase;
+			if (c1 < Hangul_VCount) {
+				/* compose the Hangul char */
+				cc = (c0 - Hangul_LBase) * Hangul_VCount;
+				cc = (cc + c1) * Hangul_TCount;
+				cc += Hangul_SBase;
+				ip++;
+				ustrlen--;
+				if (!ustrlen)
+					goto done;
+				c1 = be16_to_cpu(*ip) - Hangul_TBase;
+				if (c1 > 0 && c1 < Hangul_TCount) {
+					cc += c1;
+					ip++;
+					ustrlen--;
+				}
+				goto done;
+			}
+		}
+		while (1) {
+			/* main loop for common case of not composed chars */
+			if (!ustrlen)
+				goto same;
+			c1 = be16_to_cpu(*ip);
+			if (likely(compose))
+				ce1 = hfsplus_compose_lookup(
+					hfsplus_compose_table, c1);
+			if (ce1)
+				break;
+			hfsplus_mac2linux_compatibility_check(c0, &c0,
+							      name_type);
+			res = nls->uni2char(c0, op, len);
+			if (res < 0) {
+				if (res == -ENAMETOOLONG)
+					goto out;
+				*op = '?';
+				res = 1;
+			}
+			op += res;
+			len -= res;
+			c0 = c1;
+			ip++;
+			ustrlen--;
+		}
+		ce2 = hfsplus_compose_lookup(ce1, c0);
+		if (ce2) {
+			i = 1;
+			while (i < ustrlen) {
+				ce1 = hfsplus_compose_lookup(ce2,
+					be16_to_cpu(ip[i]));
+				if (!ce1)
+					break;
+				i++;
+				ce2 = ce1;
+			}
+			cc = ce2[0];
+			if (cc) {
+				ip += i;
+				ustrlen -= i;
+				goto done;
+			}
+		}
+same:
+		hfsplus_mac2linux_compatibility_check(c0, &cc,
+						      name_type);
+done:
+		res = nls->uni2char(cc, op, len);
+		if (res < 0) {
+			if (res == -ENAMETOOLONG)
+				goto out;
+			*op = '?';
+			res = 1;
+		}
+		op += res;
+		len -= res;
+	}
+	res = 0;
+out:
+	*len_p = (char *)op - astr;
+	return res;
+}
+
+inline int hfsplus_uni2asc_str(struct super_block *sb,
+			       const struct hfsplus_unistr *ustr, char *astr,
+			       int *len_p)
+{
+	return hfsplus_uni2asc(sb,
+				ustr, HFSPLUS_MAX_STRLEN,
+				astr, len_p,
+				HFS_REGULAR_NAME);
+}
+EXPORT_SYMBOL_IF_KUNIT(hfsplus_uni2asc_str);
+
+inline int hfsplus_uni2asc_xattr_str(struct super_block *sb,
+				     const struct hfsplus_attr_unistr *ustr,
+				     char *astr, int *len_p)
+{
+	return hfsplus_uni2asc(sb, (const struct hfsplus_unistr *)ustr,
+				HFSPLUS_ATTR_MAX_STRLEN, astr, len_p,
+				HFS_XATTR_NAME);
+}
+EXPORT_SYMBOL_IF_KUNIT(hfsplus_uni2asc_xattr_str);
+
+/*
+ * In HFS+, a filename can contain / because : is the separator.
+ * The slash is a valid filename character on macOS.
+ * But on Linux, / is the path separator and
+ * it cannot appear in a filename component.
+ * There's a parallel mapping for the NUL character (0 -> U+2400).
+ * NUL terminates strings in C/POSIX but is valid in HFS+ filenames.
+ */
+static inline
+void hfsplus_linux2mac_compatibility_check(wchar_t *uc, int name_type)
+{
+	switch (name_type) {
+	case HFS_XATTR_NAME:
+		/* ignore conversion */
+		return;
+
+	default:
+		/* continue logic */
+		break;
+	}
+
+	switch (*uc) {
+	case 0x2400:
+		*uc = 0;
+		break;
+	case ':':
+		*uc = '/';
+		break;
+	}
+}
+
+/*
+ * Convert one or more ASCII characters into a single unicode character.
+ * Returns the number of ASCII characters corresponding to the unicode char.
+ */
+static inline int asc2unichar(struct super_block *sb, const char *astr, int len,
+			      wchar_t *uc, int name_type)
+{
+	int size = HFSPLUS_SB(sb)->nls->char2uni(astr, len, uc);
+
+	if (size <= 0) {
+		*uc = '?';
+		size = 1;
+	}
+
+	hfsplus_linux2mac_compatibility_check(uc, name_type);
+	return size;
+}
+
+/* Decomposes a non-Hangul unicode character. */
+static u16 *hfsplus_decompose_nonhangul(wchar_t uc, int *size)
+{
+	int off;
+
+	off = hfsplus_decompose_table[(uc >> 12) & 0xf];
+	if (off == 0 || off == 0xffff)
+		return NULL;
+
+	off = hfsplus_decompose_table[off + ((uc >> 8) & 0xf)];
+	if (!off)
+		return NULL;
+
+	off = hfsplus_decompose_table[off + ((uc >> 4) & 0xf)];
+	if (!off)
+		return NULL;
+
+	off = hfsplus_decompose_table[off + (uc & 0xf)];
+	*size = off & 3;
+	if (*size == 0)
+		return NULL;
+	return hfsplus_decompose_table + (off / 4);
+}
+
+/*
+ * Try to decompose a unicode character as Hangul. Return 0 if @uc is not
+ * precomposed Hangul, otherwise return the length of the decomposition.
+ *
+ * This function was adapted from sample code from the Unicode Standard
+ * Annex #15: Unicode Normalization Forms, version 3.2.0.
+ *
+ * Copyright (C) 1991-2018 Unicode, Inc.  All rights reserved.  Distributed
+ * under the Terms of Use in http://www.unicode.org/copyright.html.
+ */
+static int hfsplus_try_decompose_hangul(wchar_t uc, u16 *result)
+{
+	int index;
+	int l, v, t;
+
+	index = uc - Hangul_SBase;
+	if (index < 0 || index >= Hangul_SCount)
+		return 0;
+
+	l = Hangul_LBase + index / Hangul_NCount;
+	v = Hangul_VBase + (index % Hangul_NCount) / Hangul_TCount;
+	t = Hangul_TBase + index % Hangul_TCount;
+
+	result[0] = l;
+	result[1] = v;
+	if (t != Hangul_TBase) {
+		result[2] = t;
+		return 3;
+	}
+	return 2;
+}
+
+/* Decomposes a single unicode character. */
+static u16 *decompose_unichar(wchar_t uc, int *size, u16 *hangul_buffer)
+{
+	u16 *result;
+
+	/* Hangul is handled separately */
+	result = hangul_buffer;
+	*size = hfsplus_try_decompose_hangul(uc, result);
+	if (*size == 0)
+		result = hfsplus_decompose_nonhangul(uc, size);
+	return result;
+}
+
+int hfsplus_asc2uni(struct super_block *sb,
+		    struct hfsplus_unistr *ustr, int max_unistr_len,
+		    const char *astr, int len, int name_type)
+{
+	int size, dsize, decompose;
+	u16 *dstr, outlen = 0;
+	wchar_t c;
+	u16 dhangul[3];
+
+	decompose = !test_bit(HFSPLUS_SB_NODECOMPOSE, &HFSPLUS_SB(sb)->flags);
+	while (outlen < max_unistr_len && len > 0) {
+		size = asc2unichar(sb, astr, len, &c, name_type);
+
+		if (decompose)
+			dstr = decompose_unichar(c, &dsize, dhangul);
+		else
+			dstr = NULL;
+		if (dstr) {
+			if (outlen + dsize > max_unistr_len)
+				break;
+			do {
+				ustr->unicode[outlen++] = cpu_to_be16(*dstr++);
+			} while (--dsize > 0);
+		} else
+			ustr->unicode[outlen++] = cpu_to_be16(c);
+
+		astr += size;
+		len -= size;
+	}
+	ustr->length = cpu_to_be16(outlen);
+	if (len > 0)
+		return -ENAMETOOLONG;
+	return 0;
+}
+EXPORT_SYMBOL_IF_KUNIT(hfsplus_asc2uni);
+
+/*
+ * Hash a string to an integer as appropriate for the HFS+ filesystem.
+ * Composed unicode characters are decomposed and case-folding is performed
+ * if the appropriate bits are (un)set on the superblock.
+ */
+int hfsplus_hash_dentry(const struct dentry *dentry, struct qstr *str)
+{
+	struct super_block *sb = dentry->d_sb;
+	const char *astr;
+	const u16 *dstr;
+	int casefold, decompose, size, len;
+	unsigned long hash;
+	wchar_t c;
+	u16 c2;
+	u16 dhangul[3];
+
+	casefold = test_bit(HFSPLUS_SB_CASEFOLD, &HFSPLUS_SB(sb)->flags);
+	decompose = !test_bit(HFSPLUS_SB_NODECOMPOSE, &HFSPLUS_SB(sb)->flags);
+	hash = init_name_hash(dentry);
+	astr = str->name;
+	len = str->len;
+	while (len > 0) {
+		int dsize;
+		size = asc2unichar(sb, astr, len, &c, HFS_REGULAR_NAME);
+		astr += size;
+		len -= size;
+
+		if (decompose)
+			dstr = decompose_unichar(c, &dsize, dhangul);
+		else
+			dstr = NULL;
+		if (dstr) {
+			do {
+				c2 = *dstr++;
+				if (casefold)
+					c2 = case_fold(c2);
+				if (!casefold || c2)
+					hash = partial_name_hash(c2, hash);
+			} while (--dsize > 0);
+		} else {
+			c2 = c;
+			if (casefold)
+				c2 = case_fold(c2);
+			if (!casefold || c2)
+				hash = partial_name_hash(c2, hash);
+		}
+	}
+	str->hash = end_name_hash(hash);
+
+	return 0;
+}
+EXPORT_SYMBOL_IF_KUNIT(hfsplus_hash_dentry);
+
+/*
+ * Compare strings with HFS+ filename ordering.
+ * Composed unicode characters are decomposed and case-folding is performed
+ * if the appropriate bits are (un)set on the superblock.
+ */
+int hfsplus_compare_dentry(const struct dentry *dentry,
+		unsigned int len, const char *str, const struct qstr *name)
+{
+	struct super_block *sb = dentry->d_sb;
+	int casefold, decompose, size;
+	int dsize1, dsize2, len1, len2;
+	const u16 *dstr1, *dstr2;
+	const char *astr1, *astr2;
+	u16 c1, c2;
+	wchar_t c;
+	u16 dhangul_1[3], dhangul_2[3];
+
+	casefold = test_bit(HFSPLUS_SB_CASEFOLD, &HFSPLUS_SB(sb)->flags);
+	decompose = !test_bit(HFSPLUS_SB_NODECOMPOSE, &HFSPLUS_SB(sb)->flags);
+	astr1 = str;
+	len1 = len;
+	astr2 = name->name;
+	len2 = name->len;
+	dsize1 = dsize2 = 0;
+	dstr1 = dstr2 = NULL;
+
+	while (len1 > 0 && len2 > 0) {
+		if (!dsize1) {
+			size = asc2unichar(sb, astr1, len1, &c,
+					   HFS_REGULAR_NAME);
+			astr1 += size;
+			len1 -= size;
+
+			if (decompose)
+				dstr1 = decompose_unichar(c, &dsize1,
+							  dhangul_1);
+			if (!decompose || !dstr1) {
+				c1 = c;
+				dstr1 = &c1;
+				dsize1 = 1;
+			}
+		}
+
+		if (!dsize2) {
+			size = asc2unichar(sb, astr2, len2, &c,
+					   HFS_REGULAR_NAME);
+			astr2 += size;
+			len2 -= size;
+
+			if (decompose)
+				dstr2 = decompose_unichar(c, &dsize2,
+							  dhangul_2);
+			if (!decompose || !dstr2) {
+				c2 = c;
+				dstr2 = &c2;
+				dsize2 = 1;
+			}
+		}
+
+		c1 = *dstr1;
+		c2 = *dstr2;
+		if (casefold) {
+			c1 = case_fold(c1);
+			if (!c1) {
+				dstr1++;
+				dsize1--;
+				continue;
+			}
+			c2 = case_fold(c2);
+			if (!c2) {
+				dstr2++;
+				dsize2--;
+				continue;
+			}
+		}
+		if (c1 < c2)
+			return -1;
+		else if (c1 > c2)
+			return 1;
+
+		dstr1++;
+		dsize1--;
+		dstr2++;
+		dsize2--;
+	}
+
+	if (len1 < len2)
+		return -1;
+	if (len1 > len2)
+		return 1;
+	return 0;
+}
+EXPORT_SYMBOL_IF_KUNIT(hfsplus_compare_dentry);