cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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debugfs.c (7719B)


      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * KCSAN debugfs interface.
      4 *
      5 * Copyright (C) 2019, Google LLC.
      6 */
      7
      8#define pr_fmt(fmt) "kcsan: " fmt
      9
     10#include <linux/atomic.h>
     11#include <linux/bsearch.h>
     12#include <linux/bug.h>
     13#include <linux/debugfs.h>
     14#include <linux/init.h>
     15#include <linux/kallsyms.h>
     16#include <linux/sched.h>
     17#include <linux/seq_file.h>
     18#include <linux/slab.h>
     19#include <linux/sort.h>
     20#include <linux/string.h>
     21#include <linux/uaccess.h>
     22
     23#include "kcsan.h"
     24
     25atomic_long_t kcsan_counters[KCSAN_COUNTER_COUNT];
     26static const char *const counter_names[] = {
     27	[KCSAN_COUNTER_USED_WATCHPOINTS]		= "used_watchpoints",
     28	[KCSAN_COUNTER_SETUP_WATCHPOINTS]		= "setup_watchpoints",
     29	[KCSAN_COUNTER_DATA_RACES]			= "data_races",
     30	[KCSAN_COUNTER_ASSERT_FAILURES]			= "assert_failures",
     31	[KCSAN_COUNTER_NO_CAPACITY]			= "no_capacity",
     32	[KCSAN_COUNTER_REPORT_RACES]			= "report_races",
     33	[KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN]		= "races_unknown_origin",
     34	[KCSAN_COUNTER_UNENCODABLE_ACCESSES]		= "unencodable_accesses",
     35	[KCSAN_COUNTER_ENCODING_FALSE_POSITIVES]	= "encoding_false_positives",
     36};
     37static_assert(ARRAY_SIZE(counter_names) == KCSAN_COUNTER_COUNT);
     38
     39/*
     40 * Addresses for filtering functions from reporting. This list can be used as a
     41 * whitelist or blacklist.
     42 */
     43static struct {
     44	unsigned long	*addrs;		/* array of addresses */
     45	size_t		size;		/* current size */
     46	int		used;		/* number of elements used */
     47	bool		sorted;		/* if elements are sorted */
     48	bool		whitelist;	/* if list is a blacklist or whitelist */
     49} report_filterlist = {
     50	.addrs		= NULL,
     51	.size		= 8,		/* small initial size */
     52	.used		= 0,
     53	.sorted		= false,
     54	.whitelist	= false,	/* default is blacklist */
     55};
     56static DEFINE_SPINLOCK(report_filterlist_lock);
     57
     58/*
     59 * The microbenchmark allows benchmarking KCSAN core runtime only. To run
     60 * multiple threads, pipe 'microbench=<iters>' from multiple tasks into the
     61 * debugfs file. This will not generate any conflicts, and tests fast-path only.
     62 */
     63static noinline void microbenchmark(unsigned long iters)
     64{
     65	const struct kcsan_ctx ctx_save = current->kcsan_ctx;
     66	const bool was_enabled = READ_ONCE(kcsan_enabled);
     67	u64 cycles;
     68
     69	/* We may have been called from an atomic region; reset context. */
     70	memset(&current->kcsan_ctx, 0, sizeof(current->kcsan_ctx));
     71	/*
     72	 * Disable to benchmark fast-path for all accesses, and (expected
     73	 * negligible) call into slow-path, but never set up watchpoints.
     74	 */
     75	WRITE_ONCE(kcsan_enabled, false);
     76
     77	pr_info("%s begin | iters: %lu\n", __func__, iters);
     78
     79	cycles = get_cycles();
     80	while (iters--) {
     81		unsigned long addr = iters & ((PAGE_SIZE << 8) - 1);
     82		int type = !(iters & 0x7f) ? KCSAN_ACCESS_ATOMIC :
     83				(!(iters & 0xf) ? KCSAN_ACCESS_WRITE : 0);
     84		__kcsan_check_access((void *)addr, sizeof(long), type);
     85	}
     86	cycles = get_cycles() - cycles;
     87
     88	pr_info("%s end   | cycles: %llu\n", __func__, cycles);
     89
     90	WRITE_ONCE(kcsan_enabled, was_enabled);
     91	/* restore context */
     92	current->kcsan_ctx = ctx_save;
     93}
     94
     95static int cmp_filterlist_addrs(const void *rhs, const void *lhs)
     96{
     97	const unsigned long a = *(const unsigned long *)rhs;
     98	const unsigned long b = *(const unsigned long *)lhs;
     99
    100	return a < b ? -1 : a == b ? 0 : 1;
    101}
    102
    103bool kcsan_skip_report_debugfs(unsigned long func_addr)
    104{
    105	unsigned long symbolsize, offset;
    106	unsigned long flags;
    107	bool ret = false;
    108
    109	if (!kallsyms_lookup_size_offset(func_addr, &symbolsize, &offset))
    110		return false;
    111	func_addr -= offset; /* Get function start */
    112
    113	spin_lock_irqsave(&report_filterlist_lock, flags);
    114	if (report_filterlist.used == 0)
    115		goto out;
    116
    117	/* Sort array if it is unsorted, and then do a binary search. */
    118	if (!report_filterlist.sorted) {
    119		sort(report_filterlist.addrs, report_filterlist.used,
    120		     sizeof(unsigned long), cmp_filterlist_addrs, NULL);
    121		report_filterlist.sorted = true;
    122	}
    123	ret = !!bsearch(&func_addr, report_filterlist.addrs,
    124			report_filterlist.used, sizeof(unsigned long),
    125			cmp_filterlist_addrs);
    126	if (report_filterlist.whitelist)
    127		ret = !ret;
    128
    129out:
    130	spin_unlock_irqrestore(&report_filterlist_lock, flags);
    131	return ret;
    132}
    133
    134static void set_report_filterlist_whitelist(bool whitelist)
    135{
    136	unsigned long flags;
    137
    138	spin_lock_irqsave(&report_filterlist_lock, flags);
    139	report_filterlist.whitelist = whitelist;
    140	spin_unlock_irqrestore(&report_filterlist_lock, flags);
    141}
    142
    143/* Returns 0 on success, error-code otherwise. */
    144static ssize_t insert_report_filterlist(const char *func)
    145{
    146	unsigned long flags;
    147	unsigned long addr = kallsyms_lookup_name(func);
    148	ssize_t ret = 0;
    149
    150	if (!addr) {
    151		pr_err("could not find function: '%s'\n", func);
    152		return -ENOENT;
    153	}
    154
    155	spin_lock_irqsave(&report_filterlist_lock, flags);
    156
    157	if (report_filterlist.addrs == NULL) {
    158		/* initial allocation */
    159		report_filterlist.addrs =
    160			kmalloc_array(report_filterlist.size,
    161				      sizeof(unsigned long), GFP_ATOMIC);
    162		if (report_filterlist.addrs == NULL) {
    163			ret = -ENOMEM;
    164			goto out;
    165		}
    166	} else if (report_filterlist.used == report_filterlist.size) {
    167		/* resize filterlist */
    168		size_t new_size = report_filterlist.size * 2;
    169		unsigned long *new_addrs =
    170			krealloc(report_filterlist.addrs,
    171				 new_size * sizeof(unsigned long), GFP_ATOMIC);
    172
    173		if (new_addrs == NULL) {
    174			/* leave filterlist itself untouched */
    175			ret = -ENOMEM;
    176			goto out;
    177		}
    178
    179		report_filterlist.size = new_size;
    180		report_filterlist.addrs = new_addrs;
    181	}
    182
    183	/* Note: deduplicating should be done in userspace. */
    184	report_filterlist.addrs[report_filterlist.used++] =
    185		kallsyms_lookup_name(func);
    186	report_filterlist.sorted = false;
    187
    188out:
    189	spin_unlock_irqrestore(&report_filterlist_lock, flags);
    190
    191	return ret;
    192}
    193
    194static int show_info(struct seq_file *file, void *v)
    195{
    196	int i;
    197	unsigned long flags;
    198
    199	/* show stats */
    200	seq_printf(file, "enabled: %i\n", READ_ONCE(kcsan_enabled));
    201	for (i = 0; i < KCSAN_COUNTER_COUNT; ++i) {
    202		seq_printf(file, "%s: %ld\n", counter_names[i],
    203			   atomic_long_read(&kcsan_counters[i]));
    204	}
    205
    206	/* show filter functions, and filter type */
    207	spin_lock_irqsave(&report_filterlist_lock, flags);
    208	seq_printf(file, "\n%s functions: %s\n",
    209		   report_filterlist.whitelist ? "whitelisted" : "blacklisted",
    210		   report_filterlist.used == 0 ? "none" : "");
    211	for (i = 0; i < report_filterlist.used; ++i)
    212		seq_printf(file, " %ps\n", (void *)report_filterlist.addrs[i]);
    213	spin_unlock_irqrestore(&report_filterlist_lock, flags);
    214
    215	return 0;
    216}
    217
    218static int debugfs_open(struct inode *inode, struct file *file)
    219{
    220	return single_open(file, show_info, NULL);
    221}
    222
    223static ssize_t
    224debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *off)
    225{
    226	char kbuf[KSYM_NAME_LEN];
    227	char *arg;
    228	int read_len = count < (sizeof(kbuf) - 1) ? count : (sizeof(kbuf) - 1);
    229
    230	if (copy_from_user(kbuf, buf, read_len))
    231		return -EFAULT;
    232	kbuf[read_len] = '\0';
    233	arg = strstrip(kbuf);
    234
    235	if (!strcmp(arg, "on")) {
    236		WRITE_ONCE(kcsan_enabled, true);
    237	} else if (!strcmp(arg, "off")) {
    238		WRITE_ONCE(kcsan_enabled, false);
    239	} else if (str_has_prefix(arg, "microbench=")) {
    240		unsigned long iters;
    241
    242		if (kstrtoul(&arg[strlen("microbench=")], 0, &iters))
    243			return -EINVAL;
    244		microbenchmark(iters);
    245	} else if (!strcmp(arg, "whitelist")) {
    246		set_report_filterlist_whitelist(true);
    247	} else if (!strcmp(arg, "blacklist")) {
    248		set_report_filterlist_whitelist(false);
    249	} else if (arg[0] == '!') {
    250		ssize_t ret = insert_report_filterlist(&arg[1]);
    251
    252		if (ret < 0)
    253			return ret;
    254	} else {
    255		return -EINVAL;
    256	}
    257
    258	return count;
    259}
    260
    261static const struct file_operations debugfs_ops =
    262{
    263	.read	 = seq_read,
    264	.open	 = debugfs_open,
    265	.write	 = debugfs_write,
    266	.release = single_release
    267};
    268
    269static int __init kcsan_debugfs_init(void)
    270{
    271	debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops);
    272	return 0;
    273}
    274
    275late_initcall(kcsan_debugfs_init);