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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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![Dmitry Vyukov](/assets/img/avatar_default.png)
in_interrupt() semantics are confusing and wrong for most users as it also returns true when bh is disabled. Thus we open coded a proper check for interrupts in __sanitizer_cov_trace_pc() with a lengthy explanatory comment. Use the new in_task() predicate instead. Link: http://lkml.kernel.org/r/20170321091026.139655-1-dvyukov@google.com Signed-off-by: Dmitry Vyukov <dvyukov@google.com> Cc: Kefeng Wang <wangkefeng.wang@huawei.com> Cc: James Morse <james.morse@arm.com> Cc: Alexander Popov <alex.popov@linux.com> Cc: Andrey Konovalov <andreyknvl@google.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
291 lines
6.9 KiB
C
291 lines
6.9 KiB
C
#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/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 <asm/setup.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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*/
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if (!t || !in_task())
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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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unsigned long ip = _RET_IP_;
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#ifdef CONFIG_RANDOMIZE_BASE
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ip -= kaslr_offset();
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#endif
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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] = 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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