| #define pr_fmt(fmt) "kcov: " fmt |
| |
| #define DISABLE_BRANCH_PROFILING |
| #include <linux/compiler.h> |
| #include <linux/types.h> |
| #include <linux/file.h> |
| #include <linux/fs.h> |
| #include <linux/mm.h> |
| #include <linux/printk.h> |
| #include <linux/sched.h> |
| #include <linux/slab.h> |
| #include <linux/spinlock.h> |
| #include <linux/vmalloc.h> |
| #include <linux/debugfs.h> |
| #include <linux/uaccess.h> |
| #include <linux/kcov.h> |
| |
| /* |
| * kcov descriptor (one per opened debugfs file). |
| * State transitions of the descriptor: |
| * - initial state after open() |
| * - then there must be a single ioctl(KCOV_INIT_TRACE) call |
| * - then, mmap() call (several calls are allowed but not useful) |
| * - then, repeated enable/disable for a task (only one task a time allowed) |
| */ |
| struct kcov { |
| /* |
| * Reference counter. We keep one for: |
| * - opened file descriptor |
| * - task with enabled coverage (we can't unwire it from another task) |
| */ |
| atomic_t refcount; |
| /* The lock protects mode, size, area and t. */ |
| spinlock_t lock; |
| enum kcov_mode mode; |
| /* Size of arena (in long's for KCOV_MODE_TRACE). */ |
| unsigned size; |
| /* Coverage buffer shared with user space. */ |
| void *area; |
| /* Task for which we collect coverage, or NULL. */ |
| struct task_struct *t; |
| }; |
| |
| /* |
| * Entry point from instrumented code. |
| * This is called once per basic-block/edge. |
| */ |
| void notrace __sanitizer_cov_trace_pc(void) |
| { |
| struct task_struct *t; |
| enum kcov_mode mode; |
| |
| t = current; |
| /* |
| * We are interested in code coverage as a function of a syscall inputs, |
| * so we ignore code executed in interrupts. |
| * The checks for whether we are in an interrupt are open-coded, because |
| * 1. We can't use in_interrupt() here, since it also returns true |
| * when we are inside local_bh_disable() section. |
| * 2. We don't want to use (in_irq() | in_serving_softirq() | in_nmi()), |
| * since that leads to slower generated code (three separate tests, |
| * one for each of the flags). |
| */ |
| if (!t || (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_OFFSET |
| | NMI_MASK))) |
| return; |
| mode = READ_ONCE(t->kcov_mode); |
| if (mode == KCOV_MODE_TRACE) { |
| unsigned long *area; |
| unsigned long pos; |
| |
| /* |
| * There is some code that runs in interrupts but for which |
| * in_interrupt() returns false (e.g. preempt_schedule_irq()). |
| * READ_ONCE()/barrier() effectively provides load-acquire wrt |
| * interrupts, there are paired barrier()/WRITE_ONCE() in |
| * kcov_ioctl_locked(). |
| */ |
| barrier(); |
| area = t->kcov_area; |
| /* The first word is number of subsequent PCs. */ |
| pos = READ_ONCE(area[0]) + 1; |
| if (likely(pos < t->kcov_size)) { |
| area[pos] = _RET_IP_; |
| WRITE_ONCE(area[0], pos); |
| } |
| } |
| } |
| EXPORT_SYMBOL(__sanitizer_cov_trace_pc); |
| |
| static void kcov_get(struct kcov *kcov) |
| { |
| atomic_inc(&kcov->refcount); |
| } |
| |
| static void kcov_put(struct kcov *kcov) |
| { |
| if (atomic_dec_and_test(&kcov->refcount)) { |
| vfree(kcov->area); |
| kfree(kcov); |
| } |
| } |
| |
| void kcov_task_init(struct task_struct *t) |
| { |
| t->kcov_mode = KCOV_MODE_DISABLED; |
| t->kcov_size = 0; |
| t->kcov_area = NULL; |
| t->kcov = NULL; |
| } |
| |
| void kcov_task_exit(struct task_struct *t) |
| { |
| struct kcov *kcov; |
| |
| kcov = t->kcov; |
| if (kcov == NULL) |
| return; |
| spin_lock(&kcov->lock); |
| if (WARN_ON(kcov->t != t)) { |
| spin_unlock(&kcov->lock); |
| return; |
| } |
| /* Just to not leave dangling references behind. */ |
| kcov_task_init(t); |
| kcov->t = NULL; |
| spin_unlock(&kcov->lock); |
| kcov_put(kcov); |
| } |
| |
| static int kcov_mmap(struct file *filep, struct vm_area_struct *vma) |
| { |
| int res = 0; |
| void *area; |
| struct kcov *kcov = vma->vm_file->private_data; |
| unsigned long size, off; |
| struct page *page; |
| |
| area = vmalloc_user(vma->vm_end - vma->vm_start); |
| if (!area) |
| return -ENOMEM; |
| |
| spin_lock(&kcov->lock); |
| size = kcov->size * sizeof(unsigned long); |
| if (kcov->mode == KCOV_MODE_DISABLED || vma->vm_pgoff != 0 || |
| vma->vm_end - vma->vm_start != size) { |
| res = -EINVAL; |
| goto exit; |
| } |
| if (!kcov->area) { |
| kcov->area = area; |
| vma->vm_flags |= VM_DONTEXPAND; |
| spin_unlock(&kcov->lock); |
| for (off = 0; off < size; off += PAGE_SIZE) { |
| page = vmalloc_to_page(kcov->area + off); |
| if (vm_insert_page(vma, vma->vm_start + off, page)) |
| WARN_ONCE(1, "vm_insert_page() failed"); |
| } |
| return 0; |
| } |
| exit: |
| spin_unlock(&kcov->lock); |
| vfree(area); |
| return res; |
| } |
| |
| static int kcov_open(struct inode *inode, struct file *filep) |
| { |
| struct kcov *kcov; |
| |
| kcov = kzalloc(sizeof(*kcov), GFP_KERNEL); |
| if (!kcov) |
| return -ENOMEM; |
| atomic_set(&kcov->refcount, 1); |
| spin_lock_init(&kcov->lock); |
| filep->private_data = kcov; |
| return nonseekable_open(inode, filep); |
| } |
| |
| static int kcov_close(struct inode *inode, struct file *filep) |
| { |
| kcov_put(filep->private_data); |
| return 0; |
| } |
| |
| static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd, |
| unsigned long arg) |
| { |
| struct task_struct *t; |
| unsigned long size, unused; |
| |
| 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_TRACE; |
| 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. |
| */ |
| unused = arg; |
| if (unused != 0 || kcov->mode == KCOV_MODE_DISABLED || |
| kcov->area == NULL) |
| return -EINVAL; |
| t = current; |
| if (kcov->t != NULL || t->kcov != NULL) |
| return -EBUSY; |
| /* Cache in task struct for performance. */ |
| t->kcov_size = kcov->size; |
| t->kcov_area = kcov->area; |
| /* See comment in __sanitizer_cov_trace_pc(). */ |
| barrier(); |
| WRITE_ONCE(t->kcov_mode, kcov->mode); |
| t->kcov = kcov; |
| kcov->t = t; |
| /* This is 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_task_init(t); |
| kcov->t = NULL; |
| kcov_put(kcov); |
| return 0; |
| default: |
| return -ENOTTY; |
| } |
| } |
| |
| static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) |
| { |
| struct kcov *kcov; |
| int res; |
| |
| kcov = filep->private_data; |
| spin_lock(&kcov->lock); |
| res = kcov_ioctl_locked(kcov, cmd, arg); |
| spin_unlock(&kcov->lock); |
| return res; |
| } |
| |
| static const struct file_operations kcov_fops = { |
| .open = kcov_open, |
| .unlocked_ioctl = kcov_ioctl, |
| .mmap = kcov_mmap, |
| .release = kcov_close, |
| }; |
| |
| static int __init kcov_init(void) |
| { |
| /* |
| * 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. |
| */ |
| if (!debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops)) { |
| pr_err("failed to create kcov in debugfs\n"); |
| return -ENOMEM; |
| } |
| return 0; |
| } |
| |
| device_initcall(kcov_init); |