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287 lines
7.1 KiB
287 lines
7.1 KiB
#define pr_fmt(fmt) "kcov: " fmt |
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#define DISABLE_BRANCH_PROFILING |
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#include <linux/compiler.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/mm.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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/* |
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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, repeated enable/disable for a task (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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*/ |
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atomic_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 for KCOV_MODE_TRACE). */ |
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unsigned 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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}; |
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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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enum kcov_mode mode; |
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t = current; |
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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. |
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* The checks for whether we are in an interrupt are open-coded, because |
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* 1. We can't use in_interrupt() here, since it also returns true |
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* when we are inside local_bh_disable() section. |
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* 2. We don't want to use (in_irq() | in_serving_softirq() | in_nmi()), |
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* since that leads to slower generated code (three separate tests, |
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* one for each of the flags). |
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*/ |
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if (!t || (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_OFFSET |
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| NMI_MASK))) |
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return; |
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mode = READ_ONCE(t->kcov_mode); |
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if (mode == KCOV_MODE_TRACE) { |
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unsigned long *area; |
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unsigned long pos; |
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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_ioctl_locked(). |
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*/ |
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barrier(); |
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area = t->kcov_area; |
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/* The first word is 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] = _RET_IP_; |
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WRITE_ONCE(area[0], pos); |
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} |
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} |
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} |
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EXPORT_SYMBOL(__sanitizer_cov_trace_pc); |
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static void kcov_get(struct kcov *kcov) |
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{ |
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atomic_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 (atomic_dec_and_test(&kcov->refcount)) { |
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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_init(struct task_struct *t) |
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{ |
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t->kcov_mode = KCOV_MODE_DISABLED; |
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t->kcov_size = 0; |
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t->kcov_area = NULL; |
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t->kcov = NULL; |
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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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kcov = t->kcov; |
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if (kcov == NULL) |
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return; |
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spin_lock(&kcov->lock); |
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if (WARN_ON(kcov->t != t)) { |
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spin_unlock(&kcov->lock); |
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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_task_init(t); |
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kcov->t = NULL; |
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spin_unlock(&kcov->lock); |
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kcov_put(kcov); |
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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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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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spin_lock(&kcov->lock); |
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size = kcov->size * sizeof(unsigned long); |
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if (kcov->mode == KCOV_MODE_DISABLED || 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(&kcov->lock); |
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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(&kcov->lock); |
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vfree(area); |
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return res; |
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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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kcov = kzalloc(sizeof(*kcov), GFP_KERNEL); |
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if (!kcov) |
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return -ENOMEM; |
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atomic_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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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_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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switch (cmd) { |
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case KCOV_INIT_TRACE: |
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/* |
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* Enable kcov in trace mode and setup buffer size. |
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* Must happen before anything else. |
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*/ |
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if (kcov->mode != KCOV_MODE_DISABLED) |
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return -EBUSY; |
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/* |
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* Size must be at least 2 to hold current position and one PC. |
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* Later we allocate size * sizeof(unsigned long) memory, |
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* that must not overflow. |
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*/ |
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size = arg; |
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if (size < 2 || size > INT_MAX / sizeof(unsigned long)) |
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return -EINVAL; |
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kcov->size = size; |
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kcov->mode = KCOV_MODE_TRACE; |
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return 0; |
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case KCOV_ENABLE: |
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/* |
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* Enable coverage for the current task. |
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* At this point user must have been enabled trace mode, |
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* and mmapped the file. Coverage collection is disabled only |
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* at task exit or voluntary by KCOV_DISABLE. After that it can |
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* be enabled for another task. |
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*/ |
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unused = arg; |
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if (unused != 0 || kcov->mode == KCOV_MODE_DISABLED || |
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kcov->area == NULL) |
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return -EINVAL; |
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if (kcov->t != NULL) |
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return -EBUSY; |
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t = current; |
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/* Cache in task struct for performance. */ |
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t->kcov_size = kcov->size; |
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t->kcov_area = kcov->area; |
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/* See comment in __sanitizer_cov_trace_pc(). */ |
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barrier(); |
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WRITE_ONCE(t->kcov_mode, kcov->mode); |
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t->kcov = kcov; |
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kcov->t = t; |
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/* This is put either in kcov_task_exit() or in KCOV_DISABLE. */ |
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kcov_get(kcov); |
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return 0; |
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case KCOV_DISABLE: |
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/* Disable coverage for the current task. */ |
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unused = arg; |
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if (unused != 0 || current->kcov != kcov) |
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return -EINVAL; |
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t = current; |
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if (WARN_ON(kcov->t != t)) |
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return -EINVAL; |
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kcov_task_init(t); |
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kcov->t = NULL; |
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kcov_put(kcov); |
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return 0; |
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default: |
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return -ENOTTY; |
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} |
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} |
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static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) |
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{ |
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struct kcov *kcov; |
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int res; |
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kcov = filep->private_data; |
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spin_lock(&kcov->lock); |
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res = kcov_ioctl_locked(kcov, cmd, arg); |
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spin_unlock(&kcov->lock); |
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return res; |
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} |
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static const struct file_operations kcov_fops = { |
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.open = kcov_open, |
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.unlocked_ioctl = kcov_ioctl, |
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.mmap = kcov_mmap, |
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.release = kcov_close, |
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}; |
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static int __init kcov_init(void) |
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{ |
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/* |
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* The kcov debugfs file won't ever get removed and thus, |
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* there is no need to protect it against removal races. The |
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* use of debugfs_create_file_unsafe() is actually safe here. |
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*/ |
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if (!debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops)) { |
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pr_err("failed to create kcov in debugfs\n"); |
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return -ENOMEM; |
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} |
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return 0; |
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} |
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device_initcall(kcov_init);
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