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-rw-r--r--kernel/Makefile12
-rw-r--r--kernel/exit.c2
-rw-r--r--kernel/fork.c3
-rw-r--r--kernel/kcov.c273
-rw-r--r--kernel/locking/Makefile3
-rw-r--r--kernel/rcu/Makefile4
-rw-r--r--kernel/sched/Makefile4
7 files changed, 301 insertions, 0 deletions
diff --git a/kernel/Makefile b/kernel/Makefile
index baa55e50a315..f0c40bf49d9f 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -18,6 +18,17 @@ ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_irq_work.o = $(CC_FLAGS_FTRACE)
endif
+# Prevents flicker of uninteresting __do_softirq()/__local_bh_disable_ip()
+# in coverage traces.
+KCOV_INSTRUMENT_softirq.o := n
+# These are called from save_stack_trace() on slub debug path,
+# and produce insane amounts of uninteresting coverage.
+KCOV_INSTRUMENT_module.o := n
+KCOV_INSTRUMENT_extable.o := n
+# Don't self-instrument.
+KCOV_INSTRUMENT_kcov.o := n
+KASAN_SANITIZE_kcov.o := n
+
# cond_syscall is currently not LTO compatible
CFLAGS_sys_ni.o = $(DISABLE_LTO)
@@ -68,6 +79,7 @@ obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
obj-$(CONFIG_AUDIT_WATCH) += audit_watch.o audit_fsnotify.o
obj-$(CONFIG_AUDIT_TREE) += audit_tree.o
obj-$(CONFIG_GCOV_KERNEL) += gcov/
+obj-$(CONFIG_KCOV) += kcov.o
obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_KGDB) += debug/
obj-$(CONFIG_DETECT_HUNG_TASK) += hung_task.o
diff --git a/kernel/exit.c b/kernel/exit.c
index 10e088237fed..953d1a1c0387 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -53,6 +53,7 @@
#include <linux/oom.h>
#include <linux/writeback.h>
#include <linux/shm.h>
+#include <linux/kcov.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
@@ -655,6 +656,7 @@ void do_exit(long code)
TASKS_RCU(int tasks_rcu_i);
profile_task_exit(tsk);
+ kcov_task_exit(tsk);
WARN_ON(blk_needs_flush_plug(tsk));
diff --git a/kernel/fork.c b/kernel/fork.c
index 5b8d1e7ceeea..d277e83ed3e0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -75,6 +75,7 @@
#include <linux/aio.h>
#include <linux/compiler.h>
#include <linux/sysctl.h>
+#include <linux/kcov.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -392,6 +393,8 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
account_kernel_stack(ti, 1);
+ kcov_task_init(tsk);
+
return tsk;
free_ti:
diff --git a/kernel/kcov.c b/kernel/kcov.c
new file mode 100644
index 000000000000..3efbee0834a8
--- /dev/null
+++ b/kernel/kcov.c
@@ -0,0 +1,273 @@
+#define pr_fmt(fmt) "kcov: " fmt
+
+#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/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 __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.
+ */
+ if (!t || in_interrupt())
+ 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;
+ if (kcov->t != NULL)
+ return -EBUSY;
+ t = current;
+ /* 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)
+{
+ if (!debugfs_create_file("kcov", 0600, NULL, NULL, &kcov_fops)) {
+ pr_err("failed to create kcov in debugfs\n");
+ return -ENOMEM;
+ }
+ return 0;
+}
+
+device_initcall(kcov_init);
diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
index 8e96f6cc2a4a..31322a4275cd 100644
--- a/kernel/locking/Makefile
+++ b/kernel/locking/Makefile
@@ -1,3 +1,6 @@
+# Any varying coverage in these files is non-deterministic
+# and is generally not a function of system call inputs.
+KCOV_INSTRUMENT := n
obj-y += mutex.o semaphore.o rwsem.o percpu-rwsem.o
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index 61a16569ffbf..032b2c015beb 100644
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -1,3 +1,7 @@
+# Any varying coverage in these files is non-deterministic
+# and is generally not a function of system call inputs.
+KCOV_INSTRUMENT := n
+
obj-y += update.o sync.o
obj-$(CONFIG_SRCU) += srcu.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 302d6ebd64f7..414d9c16da42 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -2,6 +2,10 @@ ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_clock.o = $(CC_FLAGS_FTRACE)
endif
+# These files are disabled because they produce non-interesting flaky coverage
+# that is not a function of syscall inputs. E.g. involuntary context switches.
+KCOV_INSTRUMENT := n
+
ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
# According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
# needed for x86 only. Why this used to be enabled for all architectures is beyond