/*
 * sysret_ss_attrs.c - test that syscalls return valid hidden SS attributes
 * Copyright (c) 2015 Andrew Lutomirski
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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.
 *
 * On AMD CPUs, SYSRET can return with a valid SS descriptor with with
 * the hidden attributes set to an unusable state.  Make sure the kernel
 * doesn't let this happen.
 */

#define _GNU_SOURCE

#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <err.h>
#include <stddef.h>
#include <stdbool.h>
#include <pthread.h>

static void *threadproc(void *ctx)
{
	/*
	 * Do our best to cause sleeps on this CPU to exit the kernel and
	 * re-enter with SS = 0.
	 */
	while (true)
		;

	return NULL;
}

#ifdef __x86_64__
extern unsigned long call32_from_64(void *stack, void (*function)(void));

asm (".pushsection .text\n\t"
     ".code32\n\t"
     "test_ss:\n\t"
     "pushl $0\n\t"
     "popl %eax\n\t"
     "ret\n\t"
     ".code64");
extern void test_ss(void);
#endif

int main()
{
	/*
	 * Start a busy-looping thread on the same CPU we're on.
	 * For simplicity, just stick everything to CPU 0.  This will
	 * fail in some containers, but that's probably okay.
	 */
	cpu_set_t cpuset;
	CPU_ZERO(&cpuset);
	CPU_SET(0, &cpuset);
	if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
		printf("[WARN]\tsched_setaffinity failed\n");

	pthread_t thread;
	if (pthread_create(&thread, 0, threadproc, 0) != 0)
		err(1, "pthread_create");

#ifdef __x86_64__
	unsigned char *stack32 = mmap(NULL, 4096, PROT_READ | PROT_WRITE,
				      MAP_32BIT | MAP_ANONYMOUS | MAP_PRIVATE,
				      -1, 0);
	if (stack32 == MAP_FAILED)
		err(1, "mmap");
#endif

	printf("[RUN]\tSyscalls followed by SS validation\n");

	for (int i = 0; i < 1000; i++) {
		/*
		 * Go to sleep and return using sysret (if we're 64-bit
		 * or we're 32-bit on AMD on a 64-bit kernel).  On AMD CPUs,
		 * SYSRET doesn't fix up the cached SS descriptor, so the
		 * kernel needs some kind of workaround to make sure that we
		 * end the system call with a valid stack segment.  This
		 * can be a confusing failure because the SS *selector*
		 * is the same regardless.
		 */
		usleep(2);

#ifdef __x86_64__
		/*
		 * On 32-bit, just doing a syscall through glibc is enough
		 * to cause a crash if our cached SS descriptor is invalid.
		 * On 64-bit, it's not, so try extra hard.
		 */
		call32_from_64(stack32 + 4088, test_ss);
#endif
	}

	printf("[OK]\tWe survived\n");

#ifdef __x86_64__
	munmap(stack32, 4096);
#endif

	return 0;
}
/linux/net-next.git/commit/?h=nds-private-remove&amp;id=0a019a28e0ca0af7dc2691d1a9527960b07ad2bb'>root</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools?h=nds-private-remove&amp;id=0a019a28e0ca0af7dc2691d1a9527960b07ad2bb'>tools</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/build?h=nds-private-remove&amp;id=0a019a28e0ca0af7dc2691d1a9527960b07ad2bb'>build</a>/<a href='/cgit.cgi/linux/net-next.git/commit/tools/build/Build?h=nds-private-remove&amp;id=0a019a28e0ca0af7dc2691d1a9527960b07ad2bb'>Build</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='h' value='nds-private-remove'/><input type='hidden' name='id' value='0a019a28e0ca0af7dc2691d1a9527960b07ad2bb'/><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>Olof Johansson &lt;olof@lixom.net&gt;</td><td class='right'>2017-01-29 21:00:48 -0800</td></tr>
<tr><th>committer</th><td>Olof Johansson &lt;olof@lixom.net&gt;</td><td class='right'>2017-01-29 21:00:48 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/tools/build/Build?h=nds-private-remove&amp;id=0a019a28e0ca0af7dc2691d1a9527960b07ad2bb'>0a019a28e0ca0af7dc2691d1a9527960b07ad2bb</a> (<a href='/cgit.cgi/linux/net-next.git/patch/tools/build/Build?id=0a019a28e0ca0af7dc2691d1a9527960b07ad2bb'>patch</a>)</td></tr>
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<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/tools/build/Build?h=nds-private-remove&amp;id=ec026b5020688a8bde5fae9a69ae3c59b66ba3ae'>ec026b5020688a8bde5fae9a69ae3c59b66ba3ae</a> (<a href='/cgit.cgi/linux/net-next.git/diff/tools/build/Build?h=nds-private-remove&amp;id=0a019a28e0ca0af7dc2691d1a9527960b07ad2bb&amp;id2=ec026b5020688a8bde5fae9a69ae3c59b66ba3ae'>diff</a>)</td></tr><tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/tools/build/Build?h=nds-private-remove&amp;id=8413299cb3933dade6186bbee8363f190032107e'>8413299cb3933dade6186bbee8363f190032107e</a> (<a href='/cgit.cgi/linux/net-next.git/diff/tools/build/Build?h=nds-private-remove&amp;id=0a019a28e0ca0af7dc2691d1a9527960b07ad2bb&amp;id2=8413299cb3933dade6186bbee8363f190032107e'>diff</a>)</td></tr></table>
<div class='commit-subject'>Merge tag 'sti-dt-for-v4.10-rc' of git://git.kernel.org/pub/scm/linux/kernel/git/pchotard/sti into fixes</div><div class='commit-msg'>STi DT fix:

Since v4.10-rc1, xhci is complaining in loop with :
    [  801.953836] usb usb6-port1: Cannot enable. Maybe the USB cable is bad?
    [  801.960455] xhci-hcd xhci-hcd.0.auto: Cannot set link state.
    [  801.966611] usb usb6-port1: cannot disable (err = -32)

set property "snps,dis_u3_susphy_quirk" in DT fix it.

* tag 'sti-dt-for-v4.10-rc' of git://git.kernel.org/pub/scm/linux/kernel/git/pchotard/sti:
  ARM: dts: STiH407-family: set snps,dis_u3_susphy_quirk

Signed-off-by: Olof Johansson &lt;olof@lixom.net&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?h=nds-private-remove&amp;id=0a019a28e0ca0af7dc2691d1a9527960b07ad2bb'>Diffstat</a> (limited to 'tools/build/Build')</div><table summary='diffstat' class='diffstat'>