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1054 lines
28 KiB
1054 lines
28 KiB
// SPDX-License-Identifier: GPL-2.0 |
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#define pr_fmt(fmt) "kcov: " fmt |
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#define DISABLE_BRANCH_PROFILING |
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#include <linux/atomic.h> |
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#include <linux/compiler.h> |
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#include <linux/errno.h> |
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#include <linux/export.h> |
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#include <linux/types.h> |
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#include <linux/file.h> |
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#include <linux/fs.h> |
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#include <linux/hashtable.h> |
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#include <linux/init.h> |
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#include <linux/mm.h> |
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#include <linux/preempt.h> |
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#include <linux/printk.h> |
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#include <linux/sched.h> |
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#include <linux/slab.h> |
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#include <linux/spinlock.h> |
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#include <linux/vmalloc.h> |
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#include <linux/debugfs.h> |
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#include <linux/uaccess.h> |
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#include <linux/kcov.h> |
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#include <linux/refcount.h> |
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#include <linux/log2.h> |
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#include <asm/setup.h> |
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#define kcov_debug(fmt, ...) pr_debug("%s: " fmt, __func__, ##__VA_ARGS__) |
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/* Number of 64-bit words written per one comparison: */ |
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#define KCOV_WORDS_PER_CMP 4 |
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/* |
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* kcov descriptor (one per opened debugfs file). |
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* State transitions of the descriptor: |
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* - initial state after open() |
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* - then there must be a single ioctl(KCOV_INIT_TRACE) call |
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* - then, mmap() call (several calls are allowed but not useful) |
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* - then, ioctl(KCOV_ENABLE, arg), where arg is |
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* KCOV_TRACE_PC - to trace only the PCs |
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* or |
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* KCOV_TRACE_CMP - to trace only the comparison operands |
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* - then, ioctl(KCOV_DISABLE) to disable the task. |
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* Enabling/disabling ioctls can be repeated (only one task a time allowed). |
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*/ |
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struct kcov { |
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/* |
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* Reference counter. We keep one for: |
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* - opened file descriptor |
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* - task with enabled coverage (we can't unwire it from another task) |
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* - each code section for remote coverage collection |
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*/ |
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refcount_t refcount; |
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/* The lock protects mode, size, area and t. */ |
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spinlock_t lock; |
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enum kcov_mode mode; |
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/* Size of arena (in long's). */ |
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unsigned int size; |
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/* Coverage buffer shared with user space. */ |
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void *area; |
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/* Task for which we collect coverage, or NULL. */ |
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struct task_struct *t; |
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/* Collecting coverage from remote (background) threads. */ |
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bool remote; |
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/* Size of remote area (in long's). */ |
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unsigned int remote_size; |
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/* |
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* Sequence is incremented each time kcov is reenabled, used by |
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* kcov_remote_stop(), see the comment there. |
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*/ |
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int sequence; |
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}; |
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struct kcov_remote_area { |
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struct list_head list; |
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unsigned int size; |
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}; |
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struct kcov_remote { |
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u64 handle; |
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struct kcov *kcov; |
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struct hlist_node hnode; |
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}; |
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static DEFINE_SPINLOCK(kcov_remote_lock); |
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static DEFINE_HASHTABLE(kcov_remote_map, 4); |
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static struct list_head kcov_remote_areas = LIST_HEAD_INIT(kcov_remote_areas); |
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struct kcov_percpu_data { |
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void *irq_area; |
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unsigned int saved_mode; |
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unsigned int saved_size; |
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void *saved_area; |
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struct kcov *saved_kcov; |
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int saved_sequence; |
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}; |
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static DEFINE_PER_CPU(struct kcov_percpu_data, kcov_percpu_data); |
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/* Must be called with kcov_remote_lock locked. */ |
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static struct kcov_remote *kcov_remote_find(u64 handle) |
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{ |
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struct kcov_remote *remote; |
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hash_for_each_possible(kcov_remote_map, remote, hnode, handle) { |
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if (remote->handle == handle) |
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return remote; |
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} |
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return NULL; |
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} |
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/* Must be called with kcov_remote_lock locked. */ |
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static struct kcov_remote *kcov_remote_add(struct kcov *kcov, u64 handle) |
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{ |
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struct kcov_remote *remote; |
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if (kcov_remote_find(handle)) |
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return ERR_PTR(-EEXIST); |
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remote = kmalloc(sizeof(*remote), GFP_ATOMIC); |
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if (!remote) |
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return ERR_PTR(-ENOMEM); |
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remote->handle = handle; |
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remote->kcov = kcov; |
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hash_add(kcov_remote_map, &remote->hnode, handle); |
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return remote; |
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} |
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/* Must be called with kcov_remote_lock locked. */ |
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static struct kcov_remote_area *kcov_remote_area_get(unsigned int size) |
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{ |
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struct kcov_remote_area *area; |
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struct list_head *pos; |
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list_for_each(pos, &kcov_remote_areas) { |
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area = list_entry(pos, struct kcov_remote_area, list); |
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if (area->size == size) { |
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list_del(&area->list); |
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return area; |
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} |
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} |
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return NULL; |
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} |
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/* Must be called with kcov_remote_lock locked. */ |
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static void kcov_remote_area_put(struct kcov_remote_area *area, |
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unsigned int size) |
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{ |
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INIT_LIST_HEAD(&area->list); |
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area->size = size; |
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list_add(&area->list, &kcov_remote_areas); |
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} |
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static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t) |
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{ |
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unsigned int mode; |
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|
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/* |
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* We are interested in code coverage as a function of a syscall inputs, |
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* so we ignore code executed in interrupts, unless we are in a remote |
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* coverage collection section in a softirq. |
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*/ |
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if (!in_task() && !(in_serving_softirq() && t->kcov_softirq)) |
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return false; |
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mode = READ_ONCE(t->kcov_mode); |
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/* |
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* There is some code that runs in interrupts but for which |
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* in_interrupt() returns false (e.g. preempt_schedule_irq()). |
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* READ_ONCE()/barrier() effectively provides load-acquire wrt |
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* interrupts, there are paired barrier()/WRITE_ONCE() in |
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* kcov_start(). |
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*/ |
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barrier(); |
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return mode == needed_mode; |
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} |
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static notrace unsigned long canonicalize_ip(unsigned long ip) |
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{ |
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#ifdef CONFIG_RANDOMIZE_BASE |
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ip -= kaslr_offset(); |
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#endif |
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return ip; |
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} |
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/* |
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* Entry point from instrumented code. |
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* This is called once per basic-block/edge. |
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*/ |
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void notrace __sanitizer_cov_trace_pc(void) |
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{ |
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struct task_struct *t; |
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unsigned long *area; |
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unsigned long ip = canonicalize_ip(_RET_IP_); |
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unsigned long pos; |
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t = current; |
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if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t)) |
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return; |
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area = t->kcov_area; |
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/* The first 64-bit word is the number of subsequent PCs. */ |
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pos = READ_ONCE(area[0]) + 1; |
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if (likely(pos < t->kcov_size)) { |
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area[pos] = ip; |
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WRITE_ONCE(area[0], pos); |
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} |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_pc); |
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#ifdef CONFIG_KCOV_ENABLE_COMPARISONS |
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static void notrace write_comp_data(u64 type, u64 arg1, u64 arg2, u64 ip) |
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{ |
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struct task_struct *t; |
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u64 *area; |
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u64 count, start_index, end_pos, max_pos; |
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t = current; |
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if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t)) |
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return; |
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ip = canonicalize_ip(ip); |
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/* |
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* We write all comparison arguments and types as u64. |
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* The buffer was allocated for t->kcov_size unsigned longs. |
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*/ |
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area = (u64 *)t->kcov_area; |
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max_pos = t->kcov_size * sizeof(unsigned long); |
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count = READ_ONCE(area[0]); |
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/* Every record is KCOV_WORDS_PER_CMP 64-bit words. */ |
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start_index = 1 + count * KCOV_WORDS_PER_CMP; |
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end_pos = (start_index + KCOV_WORDS_PER_CMP) * sizeof(u64); |
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if (likely(end_pos <= max_pos)) { |
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area[start_index] = type; |
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area[start_index + 1] = arg1; |
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area[start_index + 2] = arg2; |
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area[start_index + 3] = ip; |
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WRITE_ONCE(area[0], count + 1); |
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} |
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} |
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void notrace __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2) |
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{ |
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write_comp_data(KCOV_CMP_SIZE(0), arg1, arg2, _RET_IP_); |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1); |
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void notrace __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2) |
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{ |
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write_comp_data(KCOV_CMP_SIZE(1), arg1, arg2, _RET_IP_); |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2); |
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void notrace __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2) |
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{ |
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write_comp_data(KCOV_CMP_SIZE(2), arg1, arg2, _RET_IP_); |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4); |
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void notrace __sanitizer_cov_trace_cmp8(u64 arg1, u64 arg2) |
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{ |
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write_comp_data(KCOV_CMP_SIZE(3), arg1, arg2, _RET_IP_); |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8); |
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void notrace __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2) |
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{ |
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write_comp_data(KCOV_CMP_SIZE(0) | KCOV_CMP_CONST, arg1, arg2, |
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_RET_IP_); |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1); |
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void notrace __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2) |
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{ |
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write_comp_data(KCOV_CMP_SIZE(1) | KCOV_CMP_CONST, arg1, arg2, |
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_RET_IP_); |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2); |
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void notrace __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2) |
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{ |
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write_comp_data(KCOV_CMP_SIZE(2) | KCOV_CMP_CONST, arg1, arg2, |
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_RET_IP_); |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4); |
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void notrace __sanitizer_cov_trace_const_cmp8(u64 arg1, u64 arg2) |
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{ |
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write_comp_data(KCOV_CMP_SIZE(3) | KCOV_CMP_CONST, arg1, arg2, |
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_RET_IP_); |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8); |
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void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases) |
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{ |
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u64 i; |
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u64 count = cases[0]; |
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u64 size = cases[1]; |
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u64 type = KCOV_CMP_CONST; |
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switch (size) { |
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case 8: |
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type |= KCOV_CMP_SIZE(0); |
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break; |
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case 16: |
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type |= KCOV_CMP_SIZE(1); |
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break; |
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case 32: |
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type |= KCOV_CMP_SIZE(2); |
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break; |
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case 64: |
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type |= KCOV_CMP_SIZE(3); |
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break; |
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default: |
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return; |
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} |
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for (i = 0; i < count; i++) |
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write_comp_data(type, cases[i + 2], val, _RET_IP_); |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_switch); |
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#endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */ |
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static void kcov_start(struct task_struct *t, struct kcov *kcov, |
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unsigned int size, void *area, enum kcov_mode mode, |
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int sequence) |
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{ |
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kcov_debug("t = %px, size = %u, area = %px\n", t, size, area); |
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t->kcov = kcov; |
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/* Cache in task struct for performance. */ |
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t->kcov_size = size; |
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t->kcov_area = area; |
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t->kcov_sequence = sequence; |
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/* See comment in check_kcov_mode(). */ |
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barrier(); |
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WRITE_ONCE(t->kcov_mode, mode); |
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} |
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static void kcov_stop(struct task_struct *t) |
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{ |
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WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED); |
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barrier(); |
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t->kcov = NULL; |
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t->kcov_size = 0; |
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t->kcov_area = NULL; |
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} |
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static void kcov_task_reset(struct task_struct *t) |
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{ |
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kcov_stop(t); |
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t->kcov_sequence = 0; |
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t->kcov_handle = 0; |
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} |
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void kcov_task_init(struct task_struct *t) |
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{ |
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kcov_task_reset(t); |
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t->kcov_handle = current->kcov_handle; |
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} |
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static void kcov_reset(struct kcov *kcov) |
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{ |
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kcov->t = NULL; |
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kcov->mode = KCOV_MODE_INIT; |
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kcov->remote = false; |
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kcov->remote_size = 0; |
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kcov->sequence++; |
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} |
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static void kcov_remote_reset(struct kcov *kcov) |
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{ |
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int bkt; |
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struct kcov_remote *remote; |
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struct hlist_node *tmp; |
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unsigned long flags; |
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spin_lock_irqsave(&kcov_remote_lock, flags); |
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hash_for_each_safe(kcov_remote_map, bkt, tmp, remote, hnode) { |
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if (remote->kcov != kcov) |
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continue; |
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hash_del(&remote->hnode); |
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kfree(remote); |
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} |
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/* Do reset before unlock to prevent races with kcov_remote_start(). */ |
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kcov_reset(kcov); |
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spin_unlock_irqrestore(&kcov_remote_lock, flags); |
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} |
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static void kcov_disable(struct task_struct *t, struct kcov *kcov) |
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{ |
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kcov_task_reset(t); |
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if (kcov->remote) |
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kcov_remote_reset(kcov); |
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else |
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kcov_reset(kcov); |
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} |
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static void kcov_get(struct kcov *kcov) |
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{ |
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refcount_inc(&kcov->refcount); |
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} |
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static void kcov_put(struct kcov *kcov) |
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{ |
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if (refcount_dec_and_test(&kcov->refcount)) { |
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kcov_remote_reset(kcov); |
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vfree(kcov->area); |
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kfree(kcov); |
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} |
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} |
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void kcov_task_exit(struct task_struct *t) |
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{ |
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struct kcov *kcov; |
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unsigned long flags; |
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kcov = t->kcov; |
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if (kcov == NULL) |
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return; |
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spin_lock_irqsave(&kcov->lock, flags); |
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kcov_debug("t = %px, kcov->t = %px\n", t, kcov->t); |
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/* |
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* For KCOV_ENABLE devices we want to make sure that t->kcov->t == t, |
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* which comes down to: |
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* WARN_ON(!kcov->remote && kcov->t != t); |
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* |
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* For KCOV_REMOTE_ENABLE devices, the exiting task is either: |
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* |
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* 1. A remote task between kcov_remote_start() and kcov_remote_stop(). |
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* In this case we should print a warning right away, since a task |
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* shouldn't be exiting when it's in a kcov coverage collection |
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* section. Here t points to the task that is collecting remote |
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* coverage, and t->kcov->t points to the thread that created the |
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* kcov device. Which means that to detect this case we need to |
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* check that t != t->kcov->t, and this gives us the following: |
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* WARN_ON(kcov->remote && kcov->t != t); |
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* |
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* 2. The task that created kcov exiting without calling KCOV_DISABLE, |
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* and then again we make sure that t->kcov->t == t: |
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* WARN_ON(kcov->remote && kcov->t != t); |
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* |
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* By combining all three checks into one we get: |
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*/ |
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if (WARN_ON(kcov->t != t)) { |
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spin_unlock_irqrestore(&kcov->lock, flags); |
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return; |
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} |
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/* Just to not leave dangling references behind. */ |
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kcov_disable(t, kcov); |
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spin_unlock_irqrestore(&kcov->lock, flags); |
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kcov_put(kcov); |
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} |
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|
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static int kcov_mmap(struct file *filep, struct vm_area_struct *vma) |
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{ |
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int res = 0; |
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void *area; |
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struct kcov *kcov = vma->vm_file->private_data; |
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unsigned long size, off; |
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struct page *page; |
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unsigned long flags; |
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|
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area = vmalloc_user(vma->vm_end - vma->vm_start); |
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if (!area) |
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return -ENOMEM; |
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|
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spin_lock_irqsave(&kcov->lock, flags); |
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size = kcov->size * sizeof(unsigned long); |
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if (kcov->mode != KCOV_MODE_INIT || vma->vm_pgoff != 0 || |
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vma->vm_end - vma->vm_start != size) { |
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res = -EINVAL; |
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goto exit; |
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} |
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if (!kcov->area) { |
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kcov->area = area; |
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vma->vm_flags |= VM_DONTEXPAND; |
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spin_unlock_irqrestore(&kcov->lock, flags); |
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for (off = 0; off < size; off += PAGE_SIZE) { |
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page = vmalloc_to_page(kcov->area + off); |
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if (vm_insert_page(vma, vma->vm_start + off, page)) |
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WARN_ONCE(1, "vm_insert_page() failed"); |
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} |
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return 0; |
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} |
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exit: |
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spin_unlock_irqrestore(&kcov->lock, flags); |
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vfree(area); |
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return res; |
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} |
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|
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static int kcov_open(struct inode *inode, struct file *filep) |
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{ |
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struct kcov *kcov; |
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|
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kcov = kzalloc(sizeof(*kcov), GFP_KERNEL); |
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if (!kcov) |
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return -ENOMEM; |
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kcov->mode = KCOV_MODE_DISABLED; |
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kcov->sequence = 1; |
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refcount_set(&kcov->refcount, 1); |
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spin_lock_init(&kcov->lock); |
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filep->private_data = kcov; |
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return nonseekable_open(inode, filep); |
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} |
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|
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static int kcov_close(struct inode *inode, struct file *filep) |
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{ |
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kcov_put(filep->private_data); |
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return 0; |
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} |
|
|
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static int kcov_get_mode(unsigned long arg) |
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{ |
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if (arg == KCOV_TRACE_PC) |
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return KCOV_MODE_TRACE_PC; |
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else if (arg == KCOV_TRACE_CMP) |
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#ifdef CONFIG_KCOV_ENABLE_COMPARISONS |
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return KCOV_MODE_TRACE_CMP; |
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#else |
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return -ENOTSUPP; |
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#endif |
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else |
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return -EINVAL; |
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} |
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|
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/* |
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* Fault in a lazily-faulted vmalloc area before it can be used by |
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* __santizer_cov_trace_pc(), to avoid recursion issues if any code on the |
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* vmalloc fault handling path is instrumented. |
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*/ |
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static void kcov_fault_in_area(struct kcov *kcov) |
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{ |
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unsigned long stride = PAGE_SIZE / sizeof(unsigned long); |
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unsigned long *area = kcov->area; |
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unsigned long offset; |
|
|
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for (offset = 0; offset < kcov->size; offset += stride) |
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READ_ONCE(area[offset]); |
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} |
|
|
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static inline bool kcov_check_handle(u64 handle, bool common_valid, |
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bool uncommon_valid, bool zero_valid) |
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{ |
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if (handle & ~(KCOV_SUBSYSTEM_MASK | KCOV_INSTANCE_MASK)) |
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return false; |
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switch (handle & KCOV_SUBSYSTEM_MASK) { |
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case KCOV_SUBSYSTEM_COMMON: |
|
return (handle & KCOV_INSTANCE_MASK) ? |
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common_valid : zero_valid; |
|
case KCOV_SUBSYSTEM_USB: |
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return uncommon_valid; |
|
default: |
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return false; |
|
} |
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return false; |
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} |
|
|
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static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd, |
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unsigned long arg) |
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{ |
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struct task_struct *t; |
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unsigned long size, unused; |
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int mode, i; |
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struct kcov_remote_arg *remote_arg; |
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struct kcov_remote *remote; |
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unsigned long flags; |
|
|
|
switch (cmd) { |
|
case KCOV_INIT_TRACE: |
|
/* |
|
* Enable kcov in trace mode and setup buffer size. |
|
* Must happen before anything else. |
|
*/ |
|
if (kcov->mode != KCOV_MODE_DISABLED) |
|
return -EBUSY; |
|
/* |
|
* Size must be at least 2 to hold current position and one PC. |
|
* Later we allocate size * sizeof(unsigned long) memory, |
|
* that must not overflow. |
|
*/ |
|
size = arg; |
|
if (size < 2 || size > INT_MAX / sizeof(unsigned long)) |
|
return -EINVAL; |
|
kcov->size = size; |
|
kcov->mode = KCOV_MODE_INIT; |
|
return 0; |
|
case KCOV_ENABLE: |
|
/* |
|
* Enable coverage for the current task. |
|
* At this point user must have been enabled trace mode, |
|
* and mmapped the file. Coverage collection is disabled only |
|
* at task exit or voluntary by KCOV_DISABLE. After that it can |
|
* be enabled for another task. |
|
*/ |
|
if (kcov->mode != KCOV_MODE_INIT || !kcov->area) |
|
return -EINVAL; |
|
t = current; |
|
if (kcov->t != NULL || t->kcov != NULL) |
|
return -EBUSY; |
|
mode = kcov_get_mode(arg); |
|
if (mode < 0) |
|
return mode; |
|
kcov_fault_in_area(kcov); |
|
kcov->mode = mode; |
|
kcov_start(t, kcov, kcov->size, kcov->area, kcov->mode, |
|
kcov->sequence); |
|
kcov->t = t; |
|
/* Put either in kcov_task_exit() or in KCOV_DISABLE. */ |
|
kcov_get(kcov); |
|
return 0; |
|
case KCOV_DISABLE: |
|
/* Disable coverage for the current task. */ |
|
unused = arg; |
|
if (unused != 0 || current->kcov != kcov) |
|
return -EINVAL; |
|
t = current; |
|
if (WARN_ON(kcov->t != t)) |
|
return -EINVAL; |
|
kcov_disable(t, kcov); |
|
kcov_put(kcov); |
|
return 0; |
|
case KCOV_REMOTE_ENABLE: |
|
if (kcov->mode != KCOV_MODE_INIT || !kcov->area) |
|
return -EINVAL; |
|
t = current; |
|
if (kcov->t != NULL || t->kcov != NULL) |
|
return -EBUSY; |
|
remote_arg = (struct kcov_remote_arg *)arg; |
|
mode = kcov_get_mode(remote_arg->trace_mode); |
|
if (mode < 0) |
|
return mode; |
|
if (remote_arg->area_size > LONG_MAX / sizeof(unsigned long)) |
|
return -EINVAL; |
|
kcov->mode = mode; |
|
t->kcov = kcov; |
|
kcov->t = t; |
|
kcov->remote = true; |
|
kcov->remote_size = remote_arg->area_size; |
|
spin_lock_irqsave(&kcov_remote_lock, flags); |
|
for (i = 0; i < remote_arg->num_handles; i++) { |
|
if (!kcov_check_handle(remote_arg->handles[i], |
|
false, true, false)) { |
|
spin_unlock_irqrestore(&kcov_remote_lock, |
|
flags); |
|
kcov_disable(t, kcov); |
|
return -EINVAL; |
|
} |
|
remote = kcov_remote_add(kcov, remote_arg->handles[i]); |
|
if (IS_ERR(remote)) { |
|
spin_unlock_irqrestore(&kcov_remote_lock, |
|
flags); |
|
kcov_disable(t, kcov); |
|
return PTR_ERR(remote); |
|
} |
|
} |
|
if (remote_arg->common_handle) { |
|
if (!kcov_check_handle(remote_arg->common_handle, |
|
true, false, false)) { |
|
spin_unlock_irqrestore(&kcov_remote_lock, |
|
flags); |
|
kcov_disable(t, kcov); |
|
return -EINVAL; |
|
} |
|
remote = kcov_remote_add(kcov, |
|
remote_arg->common_handle); |
|
if (IS_ERR(remote)) { |
|
spin_unlock_irqrestore(&kcov_remote_lock, |
|
flags); |
|
kcov_disable(t, kcov); |
|
return PTR_ERR(remote); |
|
} |
|
t->kcov_handle = remote_arg->common_handle; |
|
} |
|
spin_unlock_irqrestore(&kcov_remote_lock, flags); |
|
/* Put either in kcov_task_exit() or in KCOV_DISABLE. */ |
|
kcov_get(kcov); |
|
return 0; |
|
default: |
|
return -ENOTTY; |
|
} |
|
} |
|
|
|
static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) |
|
{ |
|
struct kcov *kcov; |
|
int res; |
|
struct kcov_remote_arg *remote_arg = NULL; |
|
unsigned int remote_num_handles; |
|
unsigned long remote_arg_size; |
|
unsigned long flags; |
|
|
|
if (cmd == KCOV_REMOTE_ENABLE) { |
|
if (get_user(remote_num_handles, (unsigned __user *)(arg + |
|
offsetof(struct kcov_remote_arg, num_handles)))) |
|
return -EFAULT; |
|
if (remote_num_handles > KCOV_REMOTE_MAX_HANDLES) |
|
return -EINVAL; |
|
remote_arg_size = struct_size(remote_arg, handles, |
|
remote_num_handles); |
|
remote_arg = memdup_user((void __user *)arg, remote_arg_size); |
|
if (IS_ERR(remote_arg)) |
|
return PTR_ERR(remote_arg); |
|
if (remote_arg->num_handles != remote_num_handles) { |
|
kfree(remote_arg); |
|
return -EINVAL; |
|
} |
|
arg = (unsigned long)remote_arg; |
|
} |
|
|
|
kcov = filep->private_data; |
|
spin_lock_irqsave(&kcov->lock, flags); |
|
res = kcov_ioctl_locked(kcov, cmd, arg); |
|
spin_unlock_irqrestore(&kcov->lock, flags); |
|
|
|
kfree(remote_arg); |
|
|
|
return res; |
|
} |
|
|
|
static const struct file_operations kcov_fops = { |
|
.open = kcov_open, |
|
.unlocked_ioctl = kcov_ioctl, |
|
.compat_ioctl = kcov_ioctl, |
|
.mmap = kcov_mmap, |
|
.release = kcov_close, |
|
}; |
|
|
|
/* |
|
* kcov_remote_start() and kcov_remote_stop() can be used to annotate a section |
|
* of code in a kernel background thread or in a softirq to allow kcov to be |
|
* used to collect coverage from that part of code. |
|
* |
|
* The handle argument of kcov_remote_start() identifies a code section that is |
|
* used for coverage collection. A userspace process passes this handle to |
|
* KCOV_REMOTE_ENABLE ioctl to make the used kcov device start collecting |
|
* coverage for the code section identified by this handle. |
|
* |
|
* The usage of these annotations in the kernel code is different depending on |
|
* the type of the kernel thread whose code is being annotated. |
|
* |
|
* For global kernel threads that are spawned in a limited number of instances |
|
* (e.g. one USB hub_event() worker thread is spawned per USB HCD) and for |
|
* softirqs, each instance must be assigned a unique 4-byte instance id. The |
|
* instance id is then combined with a 1-byte subsystem id to get a handle via |
|
* kcov_remote_handle(subsystem_id, instance_id). |
|
* |
|
* For local kernel threads that are spawned from system calls handler when a |
|
* user interacts with some kernel interface (e.g. vhost workers), a handle is |
|
* passed from a userspace process as the common_handle field of the |
|
* kcov_remote_arg struct (note, that the user must generate a handle by using |
|
* kcov_remote_handle() with KCOV_SUBSYSTEM_COMMON as the subsystem id and an |
|
* arbitrary 4-byte non-zero number as the instance id). This common handle |
|
* then gets saved into the task_struct of the process that issued the |
|
* KCOV_REMOTE_ENABLE ioctl. When this process issues system calls that spawn |
|
* kernel threads, the common handle must be retrieved via kcov_common_handle() |
|
* and passed to the spawned threads via custom annotations. Those kernel |
|
* threads must in turn be annotated with kcov_remote_start(common_handle) and |
|
* kcov_remote_stop(). All of the threads that are spawned by the same process |
|
* obtain the same handle, hence the name "common". |
|
* |
|
* See Documentation/dev-tools/kcov.rst for more details. |
|
* |
|
* Internally, kcov_remote_start() looks up the kcov device associated with the |
|
* provided handle, allocates an area for coverage collection, and saves the |
|
* pointers to kcov and area into the current task_struct to allow coverage to |
|
* be collected via __sanitizer_cov_trace_pc(). |
|
* In turns kcov_remote_stop() clears those pointers from task_struct to stop |
|
* collecting coverage and copies all collected coverage into the kcov area. |
|
*/ |
|
|
|
static inline bool kcov_mode_enabled(unsigned int mode) |
|
{ |
|
return (mode & ~KCOV_IN_CTXSW) != KCOV_MODE_DISABLED; |
|
} |
|
|
|
static void kcov_remote_softirq_start(struct task_struct *t) |
|
{ |
|
struct kcov_percpu_data *data = this_cpu_ptr(&kcov_percpu_data); |
|
unsigned int mode; |
|
|
|
mode = READ_ONCE(t->kcov_mode); |
|
barrier(); |
|
if (kcov_mode_enabled(mode)) { |
|
data->saved_mode = mode; |
|
data->saved_size = t->kcov_size; |
|
data->saved_area = t->kcov_area; |
|
data->saved_sequence = t->kcov_sequence; |
|
data->saved_kcov = t->kcov; |
|
kcov_stop(t); |
|
} |
|
} |
|
|
|
static void kcov_remote_softirq_stop(struct task_struct *t) |
|
{ |
|
struct kcov_percpu_data *data = this_cpu_ptr(&kcov_percpu_data); |
|
|
|
if (data->saved_kcov) { |
|
kcov_start(t, data->saved_kcov, data->saved_size, |
|
data->saved_area, data->saved_mode, |
|
data->saved_sequence); |
|
data->saved_mode = 0; |
|
data->saved_size = 0; |
|
data->saved_area = NULL; |
|
data->saved_sequence = 0; |
|
data->saved_kcov = NULL; |
|
} |
|
} |
|
|
|
void kcov_remote_start(u64 handle) |
|
{ |
|
struct task_struct *t = current; |
|
struct kcov_remote *remote; |
|
struct kcov *kcov; |
|
unsigned int mode; |
|
void *area; |
|
unsigned int size; |
|
int sequence; |
|
unsigned long flags; |
|
|
|
if (WARN_ON(!kcov_check_handle(handle, true, true, true))) |
|
return; |
|
if (!in_task() && !in_serving_softirq()) |
|
return; |
|
|
|
local_irq_save(flags); |
|
|
|
/* |
|
* Check that kcov_remote_start() is not called twice in background |
|
* threads nor called by user tasks (with enabled kcov). |
|
*/ |
|
mode = READ_ONCE(t->kcov_mode); |
|
if (WARN_ON(in_task() && kcov_mode_enabled(mode))) { |
|
local_irq_restore(flags); |
|
return; |
|
} |
|
/* |
|
* Check that kcov_remote_start() is not called twice in softirqs. |
|
* Note, that kcov_remote_start() can be called from a softirq that |
|
* happened while collecting coverage from a background thread. |
|
*/ |
|
if (WARN_ON(in_serving_softirq() && t->kcov_softirq)) { |
|
local_irq_restore(flags); |
|
return; |
|
} |
|
|
|
spin_lock(&kcov_remote_lock); |
|
remote = kcov_remote_find(handle); |
|
if (!remote) { |
|
spin_unlock_irqrestore(&kcov_remote_lock, flags); |
|
return; |
|
} |
|
kcov_debug("handle = %llx, context: %s\n", handle, |
|
in_task() ? "task" : "softirq"); |
|
kcov = remote->kcov; |
|
/* Put in kcov_remote_stop(). */ |
|
kcov_get(kcov); |
|
/* |
|
* Read kcov fields before unlock to prevent races with |
|
* KCOV_DISABLE / kcov_remote_reset(). |
|
*/ |
|
mode = kcov->mode; |
|
sequence = kcov->sequence; |
|
if (in_task()) { |
|
size = kcov->remote_size; |
|
area = kcov_remote_area_get(size); |
|
} else { |
|
size = CONFIG_KCOV_IRQ_AREA_SIZE; |
|
area = this_cpu_ptr(&kcov_percpu_data)->irq_area; |
|
} |
|
spin_unlock_irqrestore(&kcov_remote_lock, flags); |
|
|
|
/* Can only happen when in_task(). */ |
|
if (!area) { |
|
area = vmalloc(size * sizeof(unsigned long)); |
|
if (!area) { |
|
kcov_put(kcov); |
|
return; |
|
} |
|
} |
|
|
|
local_irq_save(flags); |
|
|
|
/* Reset coverage size. */ |
|
*(u64 *)area = 0; |
|
|
|
if (in_serving_softirq()) { |
|
kcov_remote_softirq_start(t); |
|
t->kcov_softirq = 1; |
|
} |
|
kcov_start(t, kcov, size, area, mode, sequence); |
|
|
|
local_irq_restore(flags); |
|
|
|
} |
|
EXPORT_SYMBOL(kcov_remote_start); |
|
|
|
static void kcov_move_area(enum kcov_mode mode, void *dst_area, |
|
unsigned int dst_area_size, void *src_area) |
|
{ |
|
u64 word_size = sizeof(unsigned long); |
|
u64 count_size, entry_size_log; |
|
u64 dst_len, src_len; |
|
void *dst_entries, *src_entries; |
|
u64 dst_occupied, dst_free, bytes_to_move, entries_moved; |
|
|
|
kcov_debug("%px %u <= %px %lu\n", |
|
dst_area, dst_area_size, src_area, *(unsigned long *)src_area); |
|
|
|
switch (mode) { |
|
case KCOV_MODE_TRACE_PC: |
|
dst_len = READ_ONCE(*(unsigned long *)dst_area); |
|
src_len = *(unsigned long *)src_area; |
|
count_size = sizeof(unsigned long); |
|
entry_size_log = __ilog2_u64(sizeof(unsigned long)); |
|
break; |
|
case KCOV_MODE_TRACE_CMP: |
|
dst_len = READ_ONCE(*(u64 *)dst_area); |
|
src_len = *(u64 *)src_area; |
|
count_size = sizeof(u64); |
|
BUILD_BUG_ON(!is_power_of_2(KCOV_WORDS_PER_CMP)); |
|
entry_size_log = __ilog2_u64(sizeof(u64) * KCOV_WORDS_PER_CMP); |
|
break; |
|
default: |
|
WARN_ON(1); |
|
return; |
|
} |
|
|
|
/* As arm can't divide u64 integers use log of entry size. */ |
|
if (dst_len > ((dst_area_size * word_size - count_size) >> |
|
entry_size_log)) |
|
return; |
|
dst_occupied = count_size + (dst_len << entry_size_log); |
|
dst_free = dst_area_size * word_size - dst_occupied; |
|
bytes_to_move = min(dst_free, src_len << entry_size_log); |
|
dst_entries = dst_area + dst_occupied; |
|
src_entries = src_area + count_size; |
|
memcpy(dst_entries, src_entries, bytes_to_move); |
|
entries_moved = bytes_to_move >> entry_size_log; |
|
|
|
switch (mode) { |
|
case KCOV_MODE_TRACE_PC: |
|
WRITE_ONCE(*(unsigned long *)dst_area, dst_len + entries_moved); |
|
break; |
|
case KCOV_MODE_TRACE_CMP: |
|
WRITE_ONCE(*(u64 *)dst_area, dst_len + entries_moved); |
|
break; |
|
default: |
|
break; |
|
} |
|
} |
|
|
|
/* See the comment before kcov_remote_start() for usage details. */ |
|
void kcov_remote_stop(void) |
|
{ |
|
struct task_struct *t = current; |
|
struct kcov *kcov; |
|
unsigned int mode; |
|
void *area; |
|
unsigned int size; |
|
int sequence; |
|
unsigned long flags; |
|
|
|
if (!in_task() && !in_serving_softirq()) |
|
return; |
|
|
|
local_irq_save(flags); |
|
|
|
mode = READ_ONCE(t->kcov_mode); |
|
barrier(); |
|
if (!kcov_mode_enabled(mode)) { |
|
local_irq_restore(flags); |
|
return; |
|
} |
|
/* |
|
* When in softirq, check if the corresponding kcov_remote_start() |
|
* actually found the remote handle and started collecting coverage. |
|
*/ |
|
if (in_serving_softirq() && !t->kcov_softirq) { |
|
local_irq_restore(flags); |
|
return; |
|
} |
|
/* Make sure that kcov_softirq is only set when in softirq. */ |
|
if (WARN_ON(!in_serving_softirq() && t->kcov_softirq)) { |
|
local_irq_restore(flags); |
|
return; |
|
} |
|
|
|
kcov = t->kcov; |
|
area = t->kcov_area; |
|
size = t->kcov_size; |
|
sequence = t->kcov_sequence; |
|
|
|
kcov_stop(t); |
|
if (in_serving_softirq()) { |
|
t->kcov_softirq = 0; |
|
kcov_remote_softirq_stop(t); |
|
} |
|
|
|
spin_lock(&kcov->lock); |
|
/* |
|
* KCOV_DISABLE could have been called between kcov_remote_start() |
|
* and kcov_remote_stop(), hence the sequence check. |
|
*/ |
|
if (sequence == kcov->sequence && kcov->remote) |
|
kcov_move_area(kcov->mode, kcov->area, kcov->size, area); |
|
spin_unlock(&kcov->lock); |
|
|
|
if (in_task()) { |
|
spin_lock(&kcov_remote_lock); |
|
kcov_remote_area_put(area, size); |
|
spin_unlock(&kcov_remote_lock); |
|
} |
|
|
|
local_irq_restore(flags); |
|
|
|
/* Get in kcov_remote_start(). */ |
|
kcov_put(kcov); |
|
} |
|
EXPORT_SYMBOL(kcov_remote_stop); |
|
|
|
/* See the comment before kcov_remote_start() for usage details. */ |
|
u64 kcov_common_handle(void) |
|
{ |
|
if (!in_task()) |
|
return 0; |
|
return current->kcov_handle; |
|
} |
|
EXPORT_SYMBOL(kcov_common_handle); |
|
|
|
static int __init kcov_init(void) |
|
{ |
|
int cpu; |
|
|
|
for_each_possible_cpu(cpu) { |
|
void *area = vmalloc(CONFIG_KCOV_IRQ_AREA_SIZE * |
|
sizeof(unsigned long)); |
|
if (!area) |
|
return -ENOMEM; |
|
per_cpu_ptr(&kcov_percpu_data, cpu)->irq_area = area; |
|
} |
|
|
|
/* |
|
* The kcov debugfs file won't ever get removed and thus, |
|
* there is no need to protect it against removal races. The |
|
* use of debugfs_create_file_unsafe() is actually safe here. |
|
*/ |
|
debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops); |
|
|
|
return 0; |
|
} |
|
|
|
device_initcall(kcov_init);
|
|
|