Revision 1f08fe266560fc2d1383fd9c8c08fdd432ea302b authored by Antoine Tenart on 24 June 2016, 21:49:42 UTC, committed by Linus Torvalds on 25 June 2016, 00:23:52 UTC
There are different versions of Boris' name and email in the log, and one typo. Add his emails in mailmap to have all of his contributions under the same name/email tuple. Link: http://lkml.kernel.org/r/20160609130323.27706-2-antoine.tenart@free-electrons.com Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com> Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent a8a47ff
kcov.c
#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/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.
*/
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)
{
/*
* 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);
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