/*
 * Copyright (C) 2003 David Brownell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/string.h>
#include <linux/device.h>
#include <linux/nls.h>

#include <linux/usb/ch9.h>
#include <linux/usb/gadget.h>


/**
 * usb_gadget_get_string - fill out a string descriptor 
 * @table: of c strings encoded using UTF-8
 * @id: string id, from low byte of wValue in get string descriptor
 * @buf: at least 256 bytes, must be 16-bit aligned
 *
 * Finds the UTF-8 string matching the ID, and converts it into a
 * string descriptor in utf16-le.
 * Returns length of descriptor (always even) or negative errno
 *
 * If your driver needs stings in multiple languages, you'll probably
 * "switch (wIndex) { ... }"  in your ep0 string descriptor logic,
 * using this routine after choosing which set of UTF-8 strings to use.
 * Note that US-ASCII is a strict subset of UTF-8; any string bytes with
 * the eighth bit set will be multibyte UTF-8 characters, not ISO-8859/1
 * characters (which are also widely used in C strings).
 */
int
usb_gadget_get_string (struct usb_gadget_strings *table, int id, u8 *buf)
{
	struct usb_string	*s;
	int			len;

	/* descriptor 0 has the language id */
	if (id == 0) {
		buf [0] = 4;
		buf [1] = USB_DT_STRING;
		buf [2] = (u8) table->language;
		buf [3] = (u8) (table->language >> 8);
		return 4;
	}
	for (s = table->strings; s && s->s; s++)
		if (s->id == id)
			break;

	/* unrecognized: stall. */
	if (!s || !s->s)
		return -EINVAL;

	/* string descriptors have length, tag, then UTF16-LE text */
	len = min ((size_t) 126, strlen (s->s));
	len = utf8s_to_utf16s(s->s, len, UTF16_LITTLE_ENDIAN,
			(wchar_t *) &buf[2], 126);
	if (len < 0)
		return -EINVAL;
	buf [0] = (len + 1) * 2;
	buf [1] = USB_DT_STRING;
	return buf [0];
}
EXPORT_SYMBOL_GPL(usb_gadget_get_string);
e4237993c481d'>diff</a></td><td class='form'><form class='right' method='get' action='/cgit.cgi/linux/net-next.git/log/include/crypto/internal'>
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<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/commit/?id=52d7e48b86fc108e45a656d8e53e4237993c481d'>root</a>/<a href='/cgit.cgi/linux/net-next.git/commit/include?id=52d7e48b86fc108e45a656d8e53e4237993c481d'>include</a>/<a href='/cgit.cgi/linux/net-next.git/commit/include/crypto?id=52d7e48b86fc108e45a656d8e53e4237993c481d'>crypto</a>/<a href='/cgit.cgi/linux/net-next.git/commit/include/crypto/internal?id=52d7e48b86fc108e45a656d8e53e4237993c481d'>internal</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='52d7e48b86fc108e45a656d8e53e4237993c481d'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Paul E. McKenney &lt;paulmck@linux.vnet.ibm.com&gt;</td><td class='right'>2017-01-10 02:28:26 -0800</td></tr>
<tr><th>committer</th><td>Paul E. McKenney &lt;paulmck@linux.vnet.ibm.com&gt;</td><td class='right'>2017-01-14 21:23:48 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/crypto/internal?id=52d7e48b86fc108e45a656d8e53e4237993c481d'>52d7e48b86fc108e45a656d8e53e4237993c481d</a> (<a href='/cgit.cgi/linux/net-next.git/patch/include/crypto/internal?id=52d7e48b86fc108e45a656d8e53e4237993c481d'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=52d7e48b86fc108e45a656d8e53e4237993c481d'>5e95c29eb7a49a5c026e8f4af0c6b9da46f52122</a> /<a href='/cgit.cgi/linux/net-next.git/tree/include/crypto/internal?id=52d7e48b86fc108e45a656d8e53e4237993c481d'>include/crypto/internal</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/include/crypto/internal?id=f466ae66fa6a599f9a53b5f9bafea4b8cfffa7fb'>f466ae66fa6a599f9a53b5f9bafea4b8cfffa7fb</a> (<a href='/cgit.cgi/linux/net-next.git/diff/include/crypto/internal?id=52d7e48b86fc108e45a656d8e53e4237993c481d&amp;id2=f466ae66fa6a599f9a53b5f9bafea4b8cfffa7fb'>diff</a>)</td></tr></table>
<div class='commit-subject'>rcu: Narrow early boot window of illegal synchronous grace periods</div><div class='commit-msg'>The current preemptible RCU implementation goes through three phases
during bootup.  In the first phase, there is only one CPU that is running
with preemption disabled, so that a no-op is a synchronous grace period.
In the second mid-boot phase, the scheduler is running, but RCU has
not yet gotten its kthreads spawned (and, for expedited grace periods,
workqueues are not yet running.  During this time, any attempt to do
a synchronous grace period will hang the system (or complain bitterly,
depending).  In the third and final phase, RCU is fully operational and
everything works normally.

This has been OK for some time, but there has recently been some
synchronous grace periods showing up during the second mid-boot phase.
This code worked "by accident" for awhile, but started failing as soon
as expedited RCU grace periods switched over to workqueues in commit
8b355e3bc140 ("rcu: Drive expedited grace periods from workqueue").
Note that the code was buggy even before this commit, as it was subject
to failure on real-time systems that forced all expedited grace periods
to run as normal grace periods (for example, using the rcu_normal ksysfs
parameter).  The callchain from the failure case is as follows:

early_amd_iommu_init()
|-&gt; acpi_put_table(ivrs_base);
|-&gt; acpi_tb_put_table(table_desc);
|-&gt; acpi_tb_invalidate_table(table_desc);
|-&gt; acpi_tb_release_table(...)
|-&gt; acpi_os_unmap_memory
|-&gt; acpi_os_unmap_iomem
|-&gt; acpi_os_map_cleanup
|-&gt; synchronize_rcu_expedited

The kernel showing this callchain was built with CONFIG_PREEMPT_RCU=y,
which caused the code to try using workqueues before they were
initialized, which did not go well.

This commit therefore reworks RCU to permit synchronous grace periods
to proceed during this mid-boot phase.  This commit is therefore a
fix to a regression introduced in v4.9, and is therefore being put
forward post-merge-window in v4.10.

This commit sets a flag from the existing rcu_scheduler_starting()
function which causes all synchronous grace periods to take the expedited
path.  The expedited path now checks this flag, using the requesting task
to drive the expedited grace period forward during the mid-boot phase.
Finally, this flag is updated by a core_initcall() function named
rcu_exp_runtime_mode(), which causes the runtime codepaths to be used.

Note that this arrangement assumes that tasks are not sent POSIX signals
(or anything similar) from the time that the first task is spawned
through core_initcall() time.

Fixes: 8b355e3bc140 ("rcu: Drive expedited grace periods from workqueue")
Reported-by: "Zheng, Lv" &lt;lv.zheng@intel.com&gt;
Reported-by: Borislav Petkov &lt;bp@alien8.de&gt;
Signed-off-by: Paul E. McKenney &lt;paulmck@linux.vnet.ibm.com&gt;
Tested-by: Stan Kain &lt;stan.kain@gmail.com&gt;
Tested-by: Ivan &lt;waffolz@hotmail.com&gt;
Tested-by: Emanuel Castelo &lt;emanuel.castelo@gmail.com&gt;
Tested-by: Bruno Pesavento &lt;bpesavento@infinito.it&gt;
Tested-by: Borislav Petkov &lt;bp@suse.de&gt;
Tested-by: Frederic Bezies &lt;fredbezies@gmail.com&gt;
Cc: &lt;stable@vger.kernel.org&gt; # 4.9.0-
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=52d7e48b86fc108e45a656d8e53e4237993c481d'>Diffstat</a> (limited to 'include/crypto/internal')</div><table summary='diffstat' class='diffstat'>