// 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); vm_flags_set(vma, 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);