// 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/init.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 <asm/setup.h> /* 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)	 */	refcount_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;}; 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.	 */	if (!in_task())		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_ioctl_locked().	 */	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)) {		area[pos] = ip;		WRITE_ONCE(area[0], pos);	}}EXPORT_SYMBOL(__sanitizer_cov_trace_pc); #ifdef CONFIG_KCOV_ENABLE_COMPARISONSstatic 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)) {		area[start_index] = type;		area[start_index + 1] = arg1;		area[start_index + 2] = arg2;		area[start_index + 3] = ip;		WRITE_ONCE(area[0], count + 1);	}} 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_get(struct kcov *kcov){	refcount_inc(&kcov->refcount);} static void kcov_put(struct kcov *kcov){	if (refcount_dec_and_test(&kcov->refcount)) {		vfree(kcov->area);		kfree(kcov);	}} void kcov_task_init(struct task_struct *t){	WRITE_ONCE(t->kcov_mode, KCOV_MODE_DISABLED);	barrier();	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;	kcov->mode = KCOV_MODE_INIT;	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_INIT || 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;	kcov->mode = KCOV_MODE_DISABLED;	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;} /* * 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 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_INIT;		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.		 */		if (kcov->mode != KCOV_MODE_INIT || !kcov->area)			return -EINVAL;		t = current;		if (kcov->t != NULL || t->kcov != NULL)			return -EBUSY;		if (arg == KCOV_TRACE_PC)			kcov->mode = KCOV_MODE_TRACE_PC;		else if (arg == KCOV_TRACE_CMP)#ifdef CONFIG_KCOV_ENABLE_COMPARISONS			kcov->mode = KCOV_MODE_TRACE_CMP;#else		return -ENOTSUPP;#endif		else			return -EINVAL;		kcov_fault_in_area(kcov);		/* Cache in task struct for performance. */		t->kcov_size = kcov->size;		t->kcov_area = kcov->area;		/* See comment in check_kcov_mode(). */		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->mode = KCOV_MODE_INIT;		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,	.compat_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.	 */	debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops); 	return 0;} device_initcall(kcov_init);