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275 lines
7.5 KiB
275 lines
7.5 KiB
// 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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u64 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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