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976aac5f88
clang with CONFIG_LTO_CLANG points out that an initcall function should return an 'int' due to the changes made to the initcall macros in commit3578ad11f3
("init: lto: fix PREL32 relocations"): kernel/kcsan/debugfs.c:274:15: error: returning 'void' from a function with incompatible result type 'int' late_initcall(kcsan_debugfs_init); ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~ include/linux/init.h:292:46: note: expanded from macro 'late_initcall' #define late_initcall(fn) __define_initcall(fn, 7) Fixes:e36299efe7
("kcsan, debugfs: Move debugfs file creation out of early init") Cc: stable <stable@vger.kernel.org> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Marco Elver <elver@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Reviewed-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
276 lines
7.5 KiB
C
276 lines
7.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* KCSAN debugfs interface.
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*
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* Copyright (C) 2019, Google LLC.
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*/
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#define pr_fmt(fmt) "kcsan: " fmt
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#include <linux/atomic.h>
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#include <linux/bsearch.h>
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#include <linux/bug.h>
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#include <linux/debugfs.h>
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#include <linux/init.h>
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#include <linux/kallsyms.h>
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#include <linux/sched.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include <linux/sort.h>
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#include <linux/string.h>
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#include <linux/uaccess.h>
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#include "kcsan.h"
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atomic_long_t kcsan_counters[KCSAN_COUNTER_COUNT];
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static const char *const counter_names[] = {
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[KCSAN_COUNTER_USED_WATCHPOINTS] = "used_watchpoints",
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[KCSAN_COUNTER_SETUP_WATCHPOINTS] = "setup_watchpoints",
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[KCSAN_COUNTER_DATA_RACES] = "data_races",
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[KCSAN_COUNTER_ASSERT_FAILURES] = "assert_failures",
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[KCSAN_COUNTER_NO_CAPACITY] = "no_capacity",
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[KCSAN_COUNTER_REPORT_RACES] = "report_races",
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[KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN] = "races_unknown_origin",
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[KCSAN_COUNTER_UNENCODABLE_ACCESSES] = "unencodable_accesses",
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[KCSAN_COUNTER_ENCODING_FALSE_POSITIVES] = "encoding_false_positives",
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};
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static_assert(ARRAY_SIZE(counter_names) == KCSAN_COUNTER_COUNT);
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/*
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* Addresses for filtering functions from reporting. This list can be used as a
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* whitelist or blacklist.
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*/
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static struct {
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unsigned long *addrs; /* array of addresses */
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size_t size; /* current size */
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int used; /* number of elements used */
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bool sorted; /* if elements are sorted */
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bool whitelist; /* if list is a blacklist or whitelist */
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} report_filterlist = {
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.addrs = NULL,
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.size = 8, /* small initial size */
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.used = 0,
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.sorted = false,
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.whitelist = false, /* default is blacklist */
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};
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static DEFINE_SPINLOCK(report_filterlist_lock);
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/*
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* The microbenchmark allows benchmarking KCSAN core runtime only. To run
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* multiple threads, pipe 'microbench=<iters>' from multiple tasks into the
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* debugfs file. This will not generate any conflicts, and tests fast-path only.
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*/
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static noinline void microbenchmark(unsigned long iters)
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{
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const struct kcsan_ctx ctx_save = current->kcsan_ctx;
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const bool was_enabled = READ_ONCE(kcsan_enabled);
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cycles_t cycles;
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/* We may have been called from an atomic region; reset context. */
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memset(¤t->kcsan_ctx, 0, sizeof(current->kcsan_ctx));
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/*
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* Disable to benchmark fast-path for all accesses, and (expected
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* negligible) call into slow-path, but never set up watchpoints.
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*/
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WRITE_ONCE(kcsan_enabled, false);
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pr_info("%s begin | iters: %lu\n", __func__, iters);
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cycles = get_cycles();
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while (iters--) {
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unsigned long addr = iters & ((PAGE_SIZE << 8) - 1);
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int type = !(iters & 0x7f) ? KCSAN_ACCESS_ATOMIC :
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(!(iters & 0xf) ? KCSAN_ACCESS_WRITE : 0);
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__kcsan_check_access((void *)addr, sizeof(long), type);
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}
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cycles = get_cycles() - cycles;
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pr_info("%s end | cycles: %llu\n", __func__, cycles);
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WRITE_ONCE(kcsan_enabled, was_enabled);
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/* restore context */
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current->kcsan_ctx = ctx_save;
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}
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static int cmp_filterlist_addrs(const void *rhs, const void *lhs)
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{
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const unsigned long a = *(const unsigned long *)rhs;
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const unsigned long b = *(const unsigned long *)lhs;
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return a < b ? -1 : a == b ? 0 : 1;
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}
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bool kcsan_skip_report_debugfs(unsigned long func_addr)
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{
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unsigned long symbolsize, offset;
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unsigned long flags;
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bool ret = false;
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if (!kallsyms_lookup_size_offset(func_addr, &symbolsize, &offset))
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return false;
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func_addr -= offset; /* Get function start */
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spin_lock_irqsave(&report_filterlist_lock, flags);
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if (report_filterlist.used == 0)
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goto out;
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/* Sort array if it is unsorted, and then do a binary search. */
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if (!report_filterlist.sorted) {
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sort(report_filterlist.addrs, report_filterlist.used,
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sizeof(unsigned long), cmp_filterlist_addrs, NULL);
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report_filterlist.sorted = true;
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}
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ret = !!bsearch(&func_addr, report_filterlist.addrs,
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report_filterlist.used, sizeof(unsigned long),
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cmp_filterlist_addrs);
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if (report_filterlist.whitelist)
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ret = !ret;
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out:
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spin_unlock_irqrestore(&report_filterlist_lock, flags);
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return ret;
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}
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static void set_report_filterlist_whitelist(bool whitelist)
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{
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unsigned long flags;
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spin_lock_irqsave(&report_filterlist_lock, flags);
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report_filterlist.whitelist = whitelist;
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spin_unlock_irqrestore(&report_filterlist_lock, flags);
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}
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/* Returns 0 on success, error-code otherwise. */
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static ssize_t insert_report_filterlist(const char *func)
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{
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unsigned long flags;
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unsigned long addr = kallsyms_lookup_name(func);
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ssize_t ret = 0;
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if (!addr) {
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pr_err("could not find function: '%s'\n", func);
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return -ENOENT;
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}
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spin_lock_irqsave(&report_filterlist_lock, flags);
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if (report_filterlist.addrs == NULL) {
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/* initial allocation */
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report_filterlist.addrs =
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kmalloc_array(report_filterlist.size,
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sizeof(unsigned long), GFP_ATOMIC);
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if (report_filterlist.addrs == NULL) {
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ret = -ENOMEM;
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goto out;
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}
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} else if (report_filterlist.used == report_filterlist.size) {
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/* resize filterlist */
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size_t new_size = report_filterlist.size * 2;
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unsigned long *new_addrs =
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krealloc(report_filterlist.addrs,
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new_size * sizeof(unsigned long), GFP_ATOMIC);
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if (new_addrs == NULL) {
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/* leave filterlist itself untouched */
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ret = -ENOMEM;
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goto out;
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}
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report_filterlist.size = new_size;
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report_filterlist.addrs = new_addrs;
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}
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/* Note: deduplicating should be done in userspace. */
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report_filterlist.addrs[report_filterlist.used++] =
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kallsyms_lookup_name(func);
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report_filterlist.sorted = false;
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out:
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spin_unlock_irqrestore(&report_filterlist_lock, flags);
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return ret;
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}
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static int show_info(struct seq_file *file, void *v)
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{
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int i;
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unsigned long flags;
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/* show stats */
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seq_printf(file, "enabled: %i\n", READ_ONCE(kcsan_enabled));
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for (i = 0; i < KCSAN_COUNTER_COUNT; ++i) {
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seq_printf(file, "%s: %ld\n", counter_names[i],
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atomic_long_read(&kcsan_counters[i]));
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}
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/* show filter functions, and filter type */
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spin_lock_irqsave(&report_filterlist_lock, flags);
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seq_printf(file, "\n%s functions: %s\n",
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report_filterlist.whitelist ? "whitelisted" : "blacklisted",
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report_filterlist.used == 0 ? "none" : "");
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for (i = 0; i < report_filterlist.used; ++i)
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seq_printf(file, " %ps\n", (void *)report_filterlist.addrs[i]);
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spin_unlock_irqrestore(&report_filterlist_lock, flags);
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return 0;
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}
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static int debugfs_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_info, NULL);
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}
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static ssize_t
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debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *off)
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{
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char kbuf[KSYM_NAME_LEN];
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char *arg;
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int read_len = count < (sizeof(kbuf) - 1) ? count : (sizeof(kbuf) - 1);
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if (copy_from_user(kbuf, buf, read_len))
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return -EFAULT;
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kbuf[read_len] = '\0';
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arg = strstrip(kbuf);
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if (!strcmp(arg, "on")) {
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WRITE_ONCE(kcsan_enabled, true);
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} else if (!strcmp(arg, "off")) {
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WRITE_ONCE(kcsan_enabled, false);
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} else if (str_has_prefix(arg, "microbench=")) {
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unsigned long iters;
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if (kstrtoul(&arg[strlen("microbench=")], 0, &iters))
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return -EINVAL;
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microbenchmark(iters);
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} else if (!strcmp(arg, "whitelist")) {
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set_report_filterlist_whitelist(true);
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} else if (!strcmp(arg, "blacklist")) {
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set_report_filterlist_whitelist(false);
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} else if (arg[0] == '!') {
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ssize_t ret = insert_report_filterlist(&arg[1]);
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if (ret < 0)
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return ret;
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} else {
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return -EINVAL;
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}
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return count;
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}
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static const struct file_operations debugfs_ops =
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{
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.read = seq_read,
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.open = debugfs_open,
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.write = debugfs_write,
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.release = single_release
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};
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static int __init kcsan_debugfs_init(void)
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{
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debugfs_create_file("kcsan", 0644, NULL, NULL, &debugfs_ops);
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return 0;
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}
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late_initcall(kcsan_debugfs_init);
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