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-rw-r--r--kernel/kcov.c1080
1 files changed, 1080 insertions, 0 deletions
diff --git a/kernel/kcov.c b/kernel/kcov.c
new file mode 100644
index 000000000..e5cd09fd8
--- /dev/null
+++ b/kernel/kcov.c
@@ -0,0 +1,1080 @@
+// SPDX-License-Identifier: GPL-2.0
+#define pr_fmt(fmt) "kcov: " fmt
+
+#define DISABLE_BRANCH_PROFILING
+#include <linux/atomic.h>
+#include <linux/compiler.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/types.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/hashtable.h>
+#include <linux/init.h>
+#include <linux/kmsan-checks.h>
+#include <linux/mm.h>
+#include <linux/preempt.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>
+#include <linux/refcount.h>
+#include <linux/log2.h>
+#include <asm/setup.h>
+
+#define kcov_debug(fmt, ...) pr_debug("%s: " fmt, __func__, ##__VA_ARGS__)
+
+/* Number of 64-bit words written per one comparison: */
+#define KCOV_WORDS_PER_CMP 4
+
+/*
+ * 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, ioctl(KCOV_ENABLE, arg), where arg is
+ * KCOV_TRACE_PC - to trace only the PCs
+ * or
+ * KCOV_TRACE_CMP - to trace only the comparison operands
+ * - then, ioctl(KCOV_DISABLE) to disable the task.
+ * Enabling/disabling ioctls can be repeated (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)
+ * - each code section for remote coverage collection
+ */
+ refcount_t refcount;
+ /* The lock protects mode, size, area and t. */
+ spinlock_t lock;
+ enum kcov_mode mode;
+ /* Size of arena (in long's). */
+ unsigned int size;
+ /* Coverage buffer shared with user space. */
+ void *area;
+ /* Task for which we collect coverage, or NULL. */
+ struct task_struct *t;
+ /* Collecting coverage from remote (background) threads. */
+ bool remote;
+ /* Size of remote area (in long's). */
+ unsigned int remote_size;
+ /*
+ * Sequence is incremented each time kcov is reenabled, used by
+ * kcov_remote_stop(), see the comment there.
+ */
+ int sequence;
+};
+
+struct kcov_remote_area {
+ struct list_head list;
+ unsigned int size;
+};
+
+struct kcov_remote {
+ u64 handle;
+ struct kcov *kcov;
+ struct hlist_node hnode;
+};
+
+static DEFINE_SPINLOCK(kcov_remote_lock);
+static DEFINE_HASHTABLE(kcov_remote_map, 4);
+static struct list_head kcov_remote_areas = LIST_HEAD_INIT(kcov_remote_areas);
+
+struct kcov_percpu_data {
+ void *irq_area;
+ local_lock_t lock;
+
+ unsigned int saved_mode;
+ unsigned int saved_size;
+ void *saved_area;
+ struct kcov *saved_kcov;
+ int saved_sequence;
+};
+
+static DEFINE_PER_CPU(struct kcov_percpu_data, kcov_percpu_data) = {
+ .lock = INIT_LOCAL_LOCK(lock),
+};
+
+/* Must be called with kcov_remote_lock locked. */
+static struct kcov_remote *kcov_remote_find(u64 handle)
+{
+ struct kcov_remote *remote;
+
+ hash_for_each_possible(kcov_remote_map, remote, hnode, handle) {
+ if (remote->handle == handle)
+ return remote;
+ }
+ return NULL;
+}
+
+/* Must be called with kcov_remote_lock locked. */
+static struct kcov_remote *kcov_remote_add(struct kcov *kcov, u64 handle)
+{
+ struct kcov_remote *remote;
+
+ if (kcov_remote_find(handle))
+ return ERR_PTR(-EEXIST);
+ remote = kmalloc(sizeof(*remote), GFP_ATOMIC);
+ if (!remote)
+ return ERR_PTR(-ENOMEM);
+ remote->handle = handle;
+ remote->kcov = kcov;
+ hash_add(kcov_remote_map, &remote->hnode, handle);
+ return remote;
+}
+
+/* Must be called with kcov_remote_lock locked. */
+static struct kcov_remote_area *kcov_remote_area_get(unsigned int size)
+{
+ struct kcov_remote_area *area;
+ struct list_head *pos;
+
+ list_for_each(pos, &kcov_remote_areas) {
+ area = list_entry(pos, struct kcov_remote_area, list);
+ if (area->size == size) {
+ list_del(&area->list);
+ return area;
+ }
+ }
+ return NULL;
+}
+
+/* Must be called with kcov_remote_lock locked. */
+static void kcov_remote_area_put(struct kcov_remote_area *area,
+ unsigned int size)
+{
+ INIT_LIST_HEAD(&area->list);
+ area->size = size;
+ list_add(&area->list, &kcov_remote_areas);
+ /*
+ * KMSAN doesn't instrument this file, so it may not know area->list
+ * is initialized. Unpoison it explicitly to avoid reports in
+ * kcov_remote_area_get().
+ */
+ kmsan_unpoison_memory(&area->list, sizeof(area->list));
+}
+
+static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
+{
+ unsigned int mode;
+
+ /*
+ * We are interested in code coverage as a function of a syscall inputs,
+ * so we ignore code executed in interrupts, unless we are in a remote
+ * coverage collection section in a softirq.
+ */
+ if (!in_task() && !(in_serving_softirq() && t->kcov_softirq))
+ return false;
+ mode = READ_ONCE(t->kcov_mode);
+ /*
+ * 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_start().
+ */
+ barrier();
+ return mode == needed_mode;
+}
+
+static notrace unsigned long canonicalize_ip(unsigned long ip)
+{
+#ifdef CONFIG_RANDOMIZE_BASE
+ ip -= kaslr_offset();
+#endif
+ return ip;
+}
+
+/*
+ * Entry point from instrumented code.
+ * This is called once per basic-block/edge.
+ */
+void notrace __sanitizer_cov_trace_pc(void)
+{
+ struct task_struct *t;
+ unsigned long *area;
+ unsigned long ip = canonicalize_ip(_RET_IP_);
+ unsigned long pos;
+
+ t = current;
+ if (!check_kcov_mode(KCOV_MODE_TRACE_PC, t))
+ return;
+
+ area = t->kcov_area;
+ /* The first 64-bit word is the number of subsequent PCs. */
+ pos = READ_ONCE(area[0]) + 1;
+ if (likely(pos < t->kcov_size)) {
+ /* Previously we write pc before updating pos. However, some
+ * early interrupt code could bypass check_kcov_mode() check
+ * and invoke __sanitizer_cov_trace_pc(). If such interrupt is
+ * raised between writing pc and updating pos, the pc could be
+ * overitten by the recursive __sanitizer_cov_trace_pc().
+ * Update pos before writing pc to avoid such interleaving.
+ */
+ WRITE_ONCE(area[0], pos);
+ barrier();
+ area[pos] = ip;
+ }
+}
+EXPORT_SYMBOL(__sanitizer_cov_trace_pc);
+
+#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
+static void notrace write_comp_data(u64 type, u64 arg1, u64 arg2, u64 ip)
+{
+ struct task_struct *t;
+ u64 *area;
+ u64 count, start_index, end_pos, max_pos;
+
+ t = current;
+ if (!check_kcov_mode(KCOV_MODE_TRACE_CMP, t))
+ return;
+
+ ip = canonicalize_ip(ip);
+
+ /*
+ * We write all comparison arguments and types as u64.
+ * The buffer was allocated for t->kcov_size unsigned longs.
+ */
+ area = (u64 *)t->kcov_area;
+ max_pos = t->kcov_size * sizeof(unsigned long);
+
+ count = READ_ONCE(area[0]);
+
+ /* Every record is KCOV_WORDS_PER_CMP 64-bit words. */
+ start_index = 1 + count * KCOV_WORDS_PER_CMP;
+ end_pos = (start_index + KCOV_WORDS_PER_CMP) * sizeof(u64);
+ if (likely(end_pos <= max_pos)) {
+ /* See comment in __sanitizer_cov_trace_pc(). */
+ WRITE_ONCE(area[0], count + 1);
+ barrier();
+ area[start_index] = type;
+ area[start_index + 1] = arg1;
+ area[start_index + 2] = arg2;
+ area[start_index + 3] = ip;
+ }
+}
+
+void notrace __sanitizer_cov_trace_cmp1(u8 arg1, u8 arg2)
+{
+ write_comp_data(KCOV_CMP_SIZE(0), arg1, arg2, _RET_IP_);
+}
+EXPORT_SYMBOL(__sanitizer_cov_trace_cmp1);
+
+void notrace __sanitizer_cov_trace_cmp2(u16 arg1, u16 arg2)
+{
+ write_comp_data(KCOV_CMP_SIZE(1), arg1, arg2, _RET_IP_);
+}
+EXPORT_SYMBOL(__sanitizer_cov_trace_cmp2);
+
+void notrace __sanitizer_cov_trace_cmp4(u32 arg1, u32 arg2)
+{
+ write_comp_data(KCOV_CMP_SIZE(2), arg1, arg2, _RET_IP_);
+}
+EXPORT_SYMBOL(__sanitizer_cov_trace_cmp4);
+
+void notrace __sanitizer_cov_trace_cmp8(u64 arg1, u64 arg2)
+{
+ write_comp_data(KCOV_CMP_SIZE(3), arg1, arg2, _RET_IP_);
+}
+EXPORT_SYMBOL(__sanitizer_cov_trace_cmp8);
+
+void notrace __sanitizer_cov_trace_const_cmp1(u8 arg1, u8 arg2)
+{
+ write_comp_data(KCOV_CMP_SIZE(0) | KCOV_CMP_CONST, arg1, arg2,
+ _RET_IP_);
+}
+EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp1);
+
+void notrace __sanitizer_cov_trace_const_cmp2(u16 arg1, u16 arg2)
+{
+ write_comp_data(KCOV_CMP_SIZE(1) | KCOV_CMP_CONST, arg1, arg2,
+ _RET_IP_);
+}
+EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp2);
+
+void notrace __sanitizer_cov_trace_const_cmp4(u32 arg1, u32 arg2)
+{
+ write_comp_data(KCOV_CMP_SIZE(2) | KCOV_CMP_CONST, arg1, arg2,
+ _RET_IP_);
+}
+EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp4);
+
+void notrace __sanitizer_cov_trace_const_cmp8(u64 arg1, u64 arg2)
+{
+ write_comp_data(KCOV_CMP_SIZE(3) | KCOV_CMP_CONST, arg1, arg2,
+ _RET_IP_);
+}
+EXPORT_SYMBOL(__sanitizer_cov_trace_const_cmp8);
+
+void notrace __sanitizer_cov_trace_switch(u64 val, u64 *cases)
+{
+ u64 i;
+ u64 count = cases[0];
+ u64 size = cases[1];
+ u64 type = KCOV_CMP_CONST;
+
+ switch (size) {
+ case 8:
+ type |= KCOV_CMP_SIZE(0);
+ break;
+ case 16:
+ type |= KCOV_CMP_SIZE(1);
+ break;
+ case 32:
+ type |= KCOV_CMP_SIZE(2);
+ break;
+ case 64:
+ type |= KCOV_CMP_SIZE(3);
+ break;
+ default:
+ return;
+ }
+ for (i = 0; i < count; i++)
+ write_comp_data(type, cases[i + 2], val, _RET_IP_);
+}
+EXPORT_SYMBOL(__sanitizer_cov_trace_switch);
+#endif /* ifdef CONFIG_KCOV_ENABLE_COMPARISONS */
+
+static void kcov_start(struct task_struct *t, struct kcov *kcov,
+ unsigned int size, void *area, enum kcov_mode mode,
+ int sequence)
+{
+ kcov_debug("t = %px, size = %u, area = %px\n", t, size, area);
+ t->kcov = kcov;
+ /* Cache in task struct for performance. */
+ t->kcov_size = size;
+ t->kcov_area = area;
+ t->kcov_sequence = sequence;
+ /* See comment in check_kcov_mode(). */
+ barrier();
+ WRITE_ONCE(t->kcov_mode, mode);
+}
+
+static void kcov_stop(struct task_struct *t)
+{
+ WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);
+ barrier();
+ t->kcov = NULL;
+ t->kcov_size = 0;
+ t->kcov_area = NULL;
+}
+
+static void kcov_task_reset(struct task_struct *t)
+{
+ kcov_stop(t);
+ t->kcov_sequence = 0;
+ t->kcov_handle = 0;
+}
+
+void kcov_task_init(struct task_struct *t)
+{
+ kcov_task_reset(t);
+ t->kcov_handle = current->kcov_handle;
+}
+
+static void kcov_reset(struct kcov *kcov)
+{
+ kcov->t = NULL;
+ kcov->mode = KCOV_MODE_INIT;
+ kcov->remote = false;
+ kcov->remote_size = 0;
+ kcov->sequence++;
+}
+
+static void kcov_remote_reset(struct kcov *kcov)
+{
+ int bkt;
+ struct kcov_remote *remote;
+ struct hlist_node *tmp;
+ unsigned long flags;
+
+ spin_lock_irqsave(&kcov_remote_lock, flags);
+ hash_for_each_safe(kcov_remote_map, bkt, tmp, remote, hnode) {
+ if (remote->kcov != kcov)
+ continue;
+ hash_del(&remote->hnode);
+ kfree(remote);
+ }
+ /* Do reset before unlock to prevent races with kcov_remote_start(). */
+ kcov_reset(kcov);
+ spin_unlock_irqrestore(&kcov_remote_lock, flags);
+}
+
+static void kcov_disable(struct task_struct *t, struct kcov *kcov)
+{
+ kcov_task_reset(t);
+ if (kcov->remote)
+ kcov_remote_reset(kcov);
+ else
+ kcov_reset(kcov);
+}
+
+static void kcov_get(struct kcov *kcov)
+{
+ refcount_inc(&kcov->refcount);
+}
+
+static void kcov_put(struct kcov *kcov)
+{
+ if (refcount_dec_and_test(&kcov->refcount)) {
+ kcov_remote_reset(kcov);
+ vfree(kcov->area);
+ kfree(kcov);
+ }
+}
+
+void kcov_task_exit(struct task_struct *t)
+{
+ struct kcov *kcov;
+ unsigned long flags;
+
+ kcov = t->kcov;
+ if (kcov == NULL)
+ return;
+
+ spin_lock_irqsave(&kcov->lock, flags);
+ kcov_debug("t = %px, kcov->t = %px\n", t, kcov->t);
+ /*
+ * For KCOV_ENABLE devices we want to make sure that t->kcov->t == t,
+ * which comes down to:
+ * WARN_ON(!kcov->remote && kcov->t != t);
+ *
+ * For KCOV_REMOTE_ENABLE devices, the exiting task is either:
+ *
+ * 1. A remote task between kcov_remote_start() and kcov_remote_stop().
+ * In this case we should print a warning right away, since a task
+ * shouldn't be exiting when it's in a kcov coverage collection
+ * section. Here t points to the task that is collecting remote
+ * coverage, and t->kcov->t points to the thread that created the
+ * kcov device. Which means that to detect this case we need to
+ * check that t != t->kcov->t, and this gives us the following:
+ * WARN_ON(kcov->remote && kcov->t != t);
+ *
+ * 2. The task that created kcov exiting without calling KCOV_DISABLE,
+ * and then again we make sure that t->kcov->t == t:
+ * WARN_ON(kcov->remote && kcov->t != t);
+ *
+ * By combining all three checks into one we get:
+ */
+ if (WARN_ON(kcov->t != t)) {
+ spin_unlock_irqrestore(&kcov->lock, flags);
+ return;
+ }
+ /* Just to not leave dangling references behind. */
+ kcov_disable(t, kcov);
+ spin_unlock_irqrestore(&kcov->lock, flags);
+ kcov_put(kcov);
+}
+
+static int kcov_mmap(struct file *filep, struct vm_area_struct *vma)
+{
+ int res = 0;
+ struct kcov *kcov = vma->vm_file->private_data;
+ unsigned long size, off;
+ struct page *page;
+ unsigned long flags;
+
+ spin_lock_irqsave(&kcov->lock, flags);
+ size = kcov->size * sizeof(unsigned long);
+ if (kcov->area == NULL || vma->vm_pgoff != 0 ||
+ vma->vm_end - vma->vm_start != size) {
+ res = -EINVAL;
+ goto exit;
+ }
+ spin_unlock_irqrestore(&kcov->lock, flags);
+ vma->vm_flags |= VM_DONTEXPAND;
+ for (off = 0; off < size; off += PAGE_SIZE) {
+ page = vmalloc_to_page(kcov->area + off);
+ res = vm_insert_page(vma, vma->vm_start + off, page);
+ if (res) {
+ pr_warn_once("kcov: vm_insert_page() failed\n");
+ return res;
+ }
+ }
+ return 0;
+exit:
+ spin_unlock_irqrestore(&kcov->lock, flags);
+ 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;
+ kcov->mode = KCOV_MODE_DISABLED;
+ kcov->sequence = 1;
+ refcount_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_get_mode(unsigned long arg)
+{
+ if (arg == KCOV_TRACE_PC)
+ return KCOV_MODE_TRACE_PC;
+ else if (arg == KCOV_TRACE_CMP)
+#ifdef CONFIG_KCOV_ENABLE_COMPARISONS
+ return KCOV_MODE_TRACE_CMP;
+#else
+ return -ENOTSUPP;
+#endif
+ else
+ return -EINVAL;
+}
+
+/*
+ * Fault in a lazily-faulted vmalloc area before it can be used by
+ * __santizer_cov_trace_pc(), to avoid recursion issues if any code on the
+ * vmalloc fault handling path is instrumented.
+ */
+static void kcov_fault_in_area(struct kcov *kcov)
+{
+ unsigned long stride = PAGE_SIZE / sizeof(unsigned long);
+ unsigned long *area = kcov->area;
+ unsigned long offset;
+
+ for (offset = 0; offset < kcov->size; offset += stride)
+ READ_ONCE(area[offset]);
+}
+
+static inline bool kcov_check_handle(u64 handle, bool common_valid,
+ bool uncommon_valid, bool zero_valid)
+{
+ if (handle & ~(KCOV_SUBSYSTEM_MASK | KCOV_INSTANCE_MASK))
+ return false;
+ switch (handle & KCOV_SUBSYSTEM_MASK) {
+ case KCOV_SUBSYSTEM_COMMON:
+ return (handle & KCOV_INSTANCE_MASK) ?
+ common_valid : zero_valid;
+ case KCOV_SUBSYSTEM_USB:
+ return uncommon_valid;
+ default:
+ return false;
+ }
+ return false;
+}
+
+static int kcov_ioctl_locked(struct kcov *kcov, unsigned int cmd,
+ unsigned long arg)
+{
+ struct task_struct *t;
+ unsigned long flags, unused;
+ int mode, i;
+ struct kcov_remote_arg *remote_arg;
+ struct kcov_remote *remote;
+
+ switch (cmd) {
+ 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.
+ */
+ if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
+ return -EINVAL;
+ t = current;
+ if (kcov->t != NULL || t->kcov != NULL)
+ return -EBUSY;
+ mode = kcov_get_mode(arg);
+ if (mode < 0)
+ return mode;
+ kcov_fault_in_area(kcov);
+ kcov->mode = mode;
+ kcov_start(t, kcov, kcov->size, kcov->area, kcov->mode,
+ kcov->sequence);
+ kcov->t = t;
+ /* 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_disable(t, kcov);
+ kcov_put(kcov);
+ return 0;
+ case KCOV_REMOTE_ENABLE:
+ if (kcov->mode != KCOV_MODE_INIT || !kcov->area)
+ return -EINVAL;
+ t = current;
+ if (kcov->t != NULL || t->kcov != NULL)
+ return -EBUSY;
+ remote_arg = (struct kcov_remote_arg *)arg;
+ mode = kcov_get_mode(remote_arg->trace_mode);
+ if (mode < 0)
+ return mode;
+ if (remote_arg->area_size > LONG_MAX / sizeof(unsigned long))
+ return -EINVAL;
+ kcov->mode = mode;
+ t->kcov = kcov;
+ kcov->t = t;
+ kcov->remote = true;
+ kcov->remote_size = remote_arg->area_size;
+ spin_lock_irqsave(&kcov_remote_lock, flags);
+ for (i = 0; i < remote_arg->num_handles; i++) {
+ if (!kcov_check_handle(remote_arg->handles[i],
+ false, true, false)) {
+ spin_unlock_irqrestore(&kcov_remote_lock,
+ flags);
+ kcov_disable(t, kcov);
+ return -EINVAL;
+ }
+ remote = kcov_remote_add(kcov, remote_arg->handles[i]);
+ if (IS_ERR(remote)) {
+ spin_unlock_irqrestore(&kcov_remote_lock,
+ flags);
+ kcov_disable(t, kcov);
+ return PTR_ERR(remote);
+ }
+ }
+ if (remote_arg->common_handle) {
+ if (!kcov_check_handle(remote_arg->common_handle,
+ true, false, false)) {
+ spin_unlock_irqrestore(&kcov_remote_lock,
+ flags);
+ kcov_disable(t, kcov);
+ return -EINVAL;
+ }
+ remote = kcov_remote_add(kcov,
+ remote_arg->common_handle);
+ if (IS_ERR(remote)) {
+ spin_unlock_irqrestore(&kcov_remote_lock,
+ flags);
+ kcov_disable(t, kcov);
+ return PTR_ERR(remote);
+ }
+ t->kcov_handle = remote_arg->common_handle;
+ }
+ spin_unlock_irqrestore(&kcov_remote_lock, flags);
+ /* Put either in kcov_task_exit() or in KCOV_DISABLE. */
+ kcov_get(kcov);
+ return 0;
+ default:
+ return -ENOTTY;
+ }
+}
+
+static long kcov_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
+{
+ struct kcov *kcov;
+ int res;
+ struct kcov_remote_arg *remote_arg = NULL;
+ unsigned int remote_num_handles;
+ unsigned long remote_arg_size;
+ unsigned long size, flags;
+ void *area;
+
+ kcov = filep->private_data;
+ switch (cmd) {
+ case KCOV_INIT_TRACE:
+ /*
+ * Enable kcov in trace mode and setup buffer size.
+ * Must happen before anything else.
+ *
+ * First check the size argument - it must be at least 2
+ * to hold the current position and one PC.
+ */
+ size = arg;
+ if (size < 2 || size > INT_MAX / sizeof(unsigned long))
+ return -EINVAL;
+ area = vmalloc_user(size * sizeof(unsigned long));
+ if (area == NULL)
+ return -ENOMEM;
+ spin_lock_irqsave(&kcov->lock, flags);
+ if (kcov->mode != KCOV_MODE_DISABLED) {
+ spin_unlock_irqrestore(&kcov->lock, flags);
+ vfree(area);
+ return -EBUSY;
+ }
+ kcov->area = area;
+ kcov->size = size;
+ kcov->mode = KCOV_MODE_INIT;
+ spin_unlock_irqrestore(&kcov->lock, flags);
+ return 0;
+ case KCOV_REMOTE_ENABLE:
+ if (get_user(remote_num_handles, (unsigned __user *)(arg +
+ offsetof(struct kcov_remote_arg, num_handles))))
+ return -EFAULT;
+ if (remote_num_handles > KCOV_REMOTE_MAX_HANDLES)
+ return -EINVAL;
+ remote_arg_size = struct_size(remote_arg, handles,
+ remote_num_handles);
+ remote_arg = memdup_user((void __user *)arg, remote_arg_size);
+ if (IS_ERR(remote_arg))
+ return PTR_ERR(remote_arg);
+ if (remote_arg->num_handles != remote_num_handles) {
+ kfree(remote_arg);
+ return -EINVAL;
+ }
+ arg = (unsigned long)remote_arg;
+ fallthrough;
+ default:
+ /*
+ * All other commands can be normally executed under a spin lock, so we
+ * obtain and release it here in order to simplify kcov_ioctl_locked().
+ */
+ spin_lock_irqsave(&kcov->lock, flags);
+ res = kcov_ioctl_locked(kcov, cmd, arg);
+ spin_unlock_irqrestore(&kcov->lock, flags);
+ kfree(remote_arg);
+ return res;
+ }
+}
+
+static const struct file_operations kcov_fops = {
+ .open = kcov_open,
+ .unlocked_ioctl = kcov_ioctl,
+ .compat_ioctl = kcov_ioctl,
+ .mmap = kcov_mmap,
+ .release = kcov_close,
+};
+
+/*
+ * kcov_remote_start() and kcov_remote_stop() can be used to annotate a section
+ * of code in a kernel background thread or in a softirq to allow kcov to be
+ * used to collect coverage from that part of code.
+ *
+ * The handle argument of kcov_remote_start() identifies a code section that is
+ * used for coverage collection. A userspace process passes this handle to
+ * KCOV_REMOTE_ENABLE ioctl to make the used kcov device start collecting
+ * coverage for the code section identified by this handle.
+ *
+ * The usage of these annotations in the kernel code is different depending on
+ * the type of the kernel thread whose code is being annotated.
+ *
+ * For global kernel threads that are spawned in a limited number of instances
+ * (e.g. one USB hub_event() worker thread is spawned per USB HCD) and for
+ * softirqs, each instance must be assigned a unique 4-byte instance id. The
+ * instance id is then combined with a 1-byte subsystem id to get a handle via
+ * kcov_remote_handle(subsystem_id, instance_id).
+ *
+ * For local kernel threads that are spawned from system calls handler when a
+ * user interacts with some kernel interface (e.g. vhost workers), a handle is
+ * passed from a userspace process as the common_handle field of the
+ * kcov_remote_arg struct (note, that the user must generate a handle by using
+ * kcov_remote_handle() with KCOV_SUBSYSTEM_COMMON as the subsystem id and an
+ * arbitrary 4-byte non-zero number as the instance id). This common handle
+ * then gets saved into the task_struct of the process that issued the
+ * KCOV_REMOTE_ENABLE ioctl. When this process issues system calls that spawn
+ * kernel threads, the common handle must be retrieved via kcov_common_handle()
+ * and passed to the spawned threads via custom annotations. Those kernel
+ * threads must in turn be annotated with kcov_remote_start(common_handle) and
+ * kcov_remote_stop(). All of the threads that are spawned by the same process
+ * obtain the same handle, hence the name "common".
+ *
+ * See Documentation/dev-tools/kcov.rst for more details.
+ *
+ * Internally, kcov_remote_start() looks up the kcov device associated with the
+ * provided handle, allocates an area for coverage collection, and saves the
+ * pointers to kcov and area into the current task_struct to allow coverage to
+ * be collected via __sanitizer_cov_trace_pc().
+ * In turns kcov_remote_stop() clears those pointers from task_struct to stop
+ * collecting coverage and copies all collected coverage into the kcov area.
+ */
+
+static inline bool kcov_mode_enabled(unsigned int mode)
+{
+ return (mode & ~KCOV_IN_CTXSW) != KCOV_MODE_DISABLED;
+}
+
+static void kcov_remote_softirq_start(struct task_struct *t)
+{
+ struct kcov_percpu_data *data = this_cpu_ptr(&kcov_percpu_data);
+ unsigned int mode;
+
+ mode = READ_ONCE(t->kcov_mode);
+ barrier();
+ if (kcov_mode_enabled(mode)) {
+ data->saved_mode = mode;
+ data->saved_size = t->kcov_size;
+ data->saved_area = t->kcov_area;
+ data->saved_sequence = t->kcov_sequence;
+ data->saved_kcov = t->kcov;
+ kcov_stop(t);
+ }
+}
+
+static void kcov_remote_softirq_stop(struct task_struct *t)
+{
+ struct kcov_percpu_data *data = this_cpu_ptr(&kcov_percpu_data);
+
+ if (data->saved_kcov) {
+ kcov_start(t, data->saved_kcov, data->saved_size,
+ data->saved_area, data->saved_mode,
+ data->saved_sequence);
+ data->saved_mode = 0;
+ data->saved_size = 0;
+ data->saved_area = NULL;
+ data->saved_sequence = 0;
+ data->saved_kcov = NULL;
+ }
+}
+
+void kcov_remote_start(u64 handle)
+{
+ struct task_struct *t = current;
+ struct kcov_remote *remote;
+ struct kcov *kcov;
+ unsigned int mode;
+ void *area;
+ unsigned int size;
+ int sequence;
+ unsigned long flags;
+
+ if (WARN_ON(!kcov_check_handle(handle, true, true, true)))
+ return;
+ if (!in_task() && !in_serving_softirq())
+ return;
+
+ local_lock_irqsave(&kcov_percpu_data.lock, flags);
+
+ /*
+ * Check that kcov_remote_start() is not called twice in background
+ * threads nor called by user tasks (with enabled kcov).
+ */
+ mode = READ_ONCE(t->kcov_mode);
+ if (WARN_ON(in_task() && kcov_mode_enabled(mode))) {
+ local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
+ return;
+ }
+ /*
+ * Check that kcov_remote_start() is not called twice in softirqs.
+ * Note, that kcov_remote_start() can be called from a softirq that
+ * happened while collecting coverage from a background thread.
+ */
+ if (WARN_ON(in_serving_softirq() && t->kcov_softirq)) {
+ local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
+ return;
+ }
+
+ spin_lock(&kcov_remote_lock);
+ remote = kcov_remote_find(handle);
+ if (!remote) {
+ spin_unlock(&kcov_remote_lock);
+ local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
+ return;
+ }
+ kcov_debug("handle = %llx, context: %s\n", handle,
+ in_task() ? "task" : "softirq");
+ kcov = remote->kcov;
+ /* Put in kcov_remote_stop(). */
+ kcov_get(kcov);
+ /*
+ * Read kcov fields before unlock to prevent races with
+ * KCOV_DISABLE / kcov_remote_reset().
+ */
+ mode = kcov->mode;
+ sequence = kcov->sequence;
+ if (in_task()) {
+ size = kcov->remote_size;
+ area = kcov_remote_area_get(size);
+ } else {
+ size = CONFIG_KCOV_IRQ_AREA_SIZE;
+ area = this_cpu_ptr(&kcov_percpu_data)->irq_area;
+ }
+ spin_unlock(&kcov_remote_lock);
+
+ /* Can only happen when in_task(). */
+ if (!area) {
+ local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
+ area = vmalloc(size * sizeof(unsigned long));
+ if (!area) {
+ kcov_put(kcov);
+ return;
+ }
+ local_lock_irqsave(&kcov_percpu_data.lock, flags);
+ }
+
+ /* Reset coverage size. */
+ *(u64 *)area = 0;
+
+ if (in_serving_softirq()) {
+ kcov_remote_softirq_start(t);
+ t->kcov_softirq = 1;
+ }
+ kcov_start(t, kcov, size, area, mode, sequence);
+
+ local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
+
+}
+EXPORT_SYMBOL(kcov_remote_start);
+
+static void kcov_move_area(enum kcov_mode mode, void *dst_area,
+ unsigned int dst_area_size, void *src_area)
+{
+ u64 word_size = sizeof(unsigned long);
+ u64 count_size, entry_size_log;
+ u64 dst_len, src_len;
+ void *dst_entries, *src_entries;
+ u64 dst_occupied, dst_free, bytes_to_move, entries_moved;
+
+ kcov_debug("%px %u <= %px %lu\n",
+ dst_area, dst_area_size, src_area, *(unsigned long *)src_area);
+
+ switch (mode) {
+ case KCOV_MODE_TRACE_PC:
+ dst_len = READ_ONCE(*(unsigned long *)dst_area);
+ src_len = *(unsigned long *)src_area;
+ count_size = sizeof(unsigned long);
+ entry_size_log = __ilog2_u64(sizeof(unsigned long));
+ break;
+ case KCOV_MODE_TRACE_CMP:
+ dst_len = READ_ONCE(*(u64 *)dst_area);
+ src_len = *(u64 *)src_area;
+ count_size = sizeof(u64);
+ BUILD_BUG_ON(!is_power_of_2(KCOV_WORDS_PER_CMP));
+ entry_size_log = __ilog2_u64(sizeof(u64) * KCOV_WORDS_PER_CMP);
+ break;
+ default:
+ WARN_ON(1);
+ return;
+ }
+
+ /* As arm can't divide u64 integers use log of entry size. */
+ if (dst_len > ((dst_area_size * word_size - count_size) >>
+ entry_size_log))
+ return;
+ dst_occupied = count_size + (dst_len << entry_size_log);
+ dst_free = dst_area_size * word_size - dst_occupied;
+ bytes_to_move = min(dst_free, src_len << entry_size_log);
+ dst_entries = dst_area + dst_occupied;
+ src_entries = src_area + count_size;
+ memcpy(dst_entries, src_entries, bytes_to_move);
+ entries_moved = bytes_to_move >> entry_size_log;
+
+ switch (mode) {
+ case KCOV_MODE_TRACE_PC:
+ WRITE_ONCE(*(unsigned long *)dst_area, dst_len + entries_moved);
+ break;
+ case KCOV_MODE_TRACE_CMP:
+ WRITE_ONCE(*(u64 *)dst_area, dst_len + entries_moved);
+ break;
+ default:
+ break;
+ }
+}
+
+/* See the comment before kcov_remote_start() for usage details. */
+void kcov_remote_stop(void)
+{
+ struct task_struct *t = current;
+ struct kcov *kcov;
+ unsigned int mode;
+ void *area;
+ unsigned int size;
+ int sequence;
+ unsigned long flags;
+
+ if (!in_task() && !in_serving_softirq())
+ return;
+
+ local_lock_irqsave(&kcov_percpu_data.lock, flags);
+
+ mode = READ_ONCE(t->kcov_mode);
+ barrier();
+ if (!kcov_mode_enabled(mode)) {
+ local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
+ return;
+ }
+ /*
+ * When in softirq, check if the corresponding kcov_remote_start()
+ * actually found the remote handle and started collecting coverage.
+ */
+ if (in_serving_softirq() && !t->kcov_softirq) {
+ local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
+ return;
+ }
+ /* Make sure that kcov_softirq is only set when in softirq. */
+ if (WARN_ON(!in_serving_softirq() && t->kcov_softirq)) {
+ local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
+ return;
+ }
+
+ kcov = t->kcov;
+ area = t->kcov_area;
+ size = t->kcov_size;
+ sequence = t->kcov_sequence;
+
+ kcov_stop(t);
+ if (in_serving_softirq()) {
+ t->kcov_softirq = 0;
+ kcov_remote_softirq_stop(t);
+ }
+
+ spin_lock(&kcov->lock);
+ /*
+ * KCOV_DISABLE could have been called between kcov_remote_start()
+ * and kcov_remote_stop(), hence the sequence check.
+ */
+ if (sequence == kcov->sequence && kcov->remote)
+ kcov_move_area(kcov->mode, kcov->area, kcov->size, area);
+ spin_unlock(&kcov->lock);
+
+ if (in_task()) {
+ spin_lock(&kcov_remote_lock);
+ kcov_remote_area_put(area, size);
+ spin_unlock(&kcov_remote_lock);
+ }
+
+ local_unlock_irqrestore(&kcov_percpu_data.lock, flags);
+
+ /* Get in kcov_remote_start(). */
+ kcov_put(kcov);
+}
+EXPORT_SYMBOL(kcov_remote_stop);
+
+/* See the comment before kcov_remote_start() for usage details. */
+u64 kcov_common_handle(void)
+{
+ if (!in_task())
+ return 0;
+ return current->kcov_handle;
+}
+EXPORT_SYMBOL(kcov_common_handle);
+
+static int __init kcov_init(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ void *area = vmalloc_node(CONFIG_KCOV_IRQ_AREA_SIZE *
+ sizeof(unsigned long), cpu_to_node(cpu));
+ if (!area)
+ return -ENOMEM;
+ per_cpu_ptr(&kcov_percpu_data, cpu)->irq_area = area;
+ }
+
+ /*
+ * 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.
+ */
+ debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops);
+
+ return 0;
+}
+
+device_initcall(kcov_init);
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-28 12:07:23 +0000