When unregistering kcov from the coverage interface we should use the unregister function, not the register function. Sponsored by: DARPA, AFRL
567 lines
15 KiB
C
567 lines
15 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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*
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* Copyright (C) 2018 The FreeBSD Foundation. All rights reserved.
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* Copyright (C) 2018, 2019 Andrew Turner
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*
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* This software was developed by Mitchell Horne under sponsorship of
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* the FreeBSD Foundation.
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*
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* This software was developed by SRI International and the University of
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* Cambridge Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
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* ("CTSRD"), as part of the DARPA CRASH research programme.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/conf.h>
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#include <sys/kcov.h>
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#include <sys/kernel.h>
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#include <sys/limits.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mman.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/rwlock.h>
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#include <sys/sysctl.h>
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#include <vm/vm.h>
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#include <vm/pmap.h>
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#include <vm/vm_extern.h>
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#include <vm/vm_object.h>
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#include <vm/vm_page.h>
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#include <vm/vm_pager.h>
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MALLOC_DEFINE(M_KCOV_INFO, "kcovinfo", "KCOV info type");
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#define KCOV_ELEMENT_SIZE sizeof(uint64_t)
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/*
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* To know what the code can safely perform at any point in time we use a
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* state machine. In the normal case the state transitions are:
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*
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* OPEN -> READY -> RUNNING -> DYING
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* | | ^ | ^ ^
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* | | +--------+ | |
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* | +-------------------+ |
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* +-----------------------------+
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*
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* The states are:
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* OPEN: The kcov fd has been opened, but no buffer is available to store
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* coverage data.
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* READY: The buffer to store coverage data has been allocated. Userspace
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* can set this by using ioctl(fd, KIOSETBUFSIZE, entries);. When
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* this has been set the buffer can be written to by the kernel,
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* and mmaped by userspace.
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* RUNNING: The coverage probes are able to store coverage data in the buffer.
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* This is entered with ioctl(fd, KIOENABLE, mode);. The READY state
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* can be exited by ioctl(fd, KIODISABLE); or exiting the thread to
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* return to the READY state to allow tracing to be reused, or by
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* closing the kcov fd to enter the DYING state.
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* DYING: The fd has been closed. All states can enter into this state when
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* userspace closes the kcov fd.
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*
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* We need to be careful when moving into and out of the RUNNING state. As
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* an interrupt may happen while this is happening the ordering of memory
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* operations is important so struct kcov_info is valid for the tracing
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* functions.
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*
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* When moving into the RUNNING state prior stores to struct kcov_info need
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* to be observed before the state is set. This allows for interrupts that
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* may call into one of the coverage functions to fire at any point while
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* being enabled and see a consistent struct kcov_info.
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*
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* When moving out of the RUNNING state any later stores to struct kcov_info
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* need to be observed after the state is set. As with entering this is to
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* present a consistent struct kcov_info to interrupts.
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*/
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typedef enum {
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KCOV_STATE_INVALID,
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KCOV_STATE_OPEN, /* The device is open, but with no buffer */
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KCOV_STATE_READY, /* The buffer has been allocated */
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KCOV_STATE_RUNNING, /* Recording trace data */
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KCOV_STATE_DYING, /* The fd was closed */
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} kcov_state_t;
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/*
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* (l) Set while holding the kcov_lock mutex and not in the RUNNING state.
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* (o) Only set once while in the OPEN state. Cleaned up while in the DYING
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* state, and with no thread associated with the struct kcov_info.
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* (s) Set atomically to enter or exit the RUNNING state, non-atomically
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* otherwise. See above for a description of the other constraints while
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* moving into or out of the RUNNING state.
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*/
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struct kcov_info {
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struct thread *thread; /* (l) */
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vm_object_t bufobj; /* (o) */
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vm_offset_t kvaddr; /* (o) */
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size_t entries; /* (o) */
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size_t bufsize; /* (o) */
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kcov_state_t state; /* (s) */
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int mode; /* (l) */
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bool mmap;
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};
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/* Prototypes */
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static d_open_t kcov_open;
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static d_close_t kcov_close;
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static d_mmap_single_t kcov_mmap_single;
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static d_ioctl_t kcov_ioctl;
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static int kcov_alloc(struct kcov_info *info, size_t entries);
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static void kcov_init(const void *unused);
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static struct cdevsw kcov_cdevsw = {
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.d_version = D_VERSION,
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.d_open = kcov_open,
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.d_close = kcov_close,
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.d_mmap_single = kcov_mmap_single,
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.d_ioctl = kcov_ioctl,
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.d_name = "kcov",
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};
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SYSCTL_NODE(_kern, OID_AUTO, kcov, CTLFLAG_RW, 0, "Kernel coverage");
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static u_int kcov_max_entries = KCOV_MAXENTRIES;
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SYSCTL_UINT(_kern_kcov, OID_AUTO, max_entries, CTLFLAG_RW,
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&kcov_max_entries, 0,
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"Maximum number of entries in the kcov buffer");
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static struct mtx kcov_lock;
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static int active_count;
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static struct kcov_info *
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get_kinfo(struct thread *td)
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{
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struct kcov_info *info;
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/* We might have a NULL thread when releasing the secondary CPUs */
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if (td == NULL)
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return (NULL);
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/*
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* We are in an interrupt, stop tracing as it is not explicitly
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* part of a syscall.
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*/
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if (td->td_intr_nesting_level > 0 || td->td_intr_frame != NULL)
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return (NULL);
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/*
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* If info is NULL or the state is not running we are not tracing.
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*/
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info = td->td_kcov_info;
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if (info == NULL ||
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atomic_load_acq_int(&info->state) != KCOV_STATE_RUNNING)
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return (NULL);
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return (info);
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}
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static void
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trace_pc(uintptr_t ret)
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{
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struct thread *td;
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struct kcov_info *info;
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uint64_t *buf, index;
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td = curthread;
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info = get_kinfo(td);
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if (info == NULL)
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return;
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/*
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* Check we are in the PC-trace mode.
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*/
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if (info->mode != KCOV_MODE_TRACE_PC)
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return;
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KASSERT(info->kvaddr != 0,
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("__sanitizer_cov_trace_pc: NULL buf while running"));
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buf = (uint64_t *)info->kvaddr;
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/* The first entry of the buffer holds the index */
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index = buf[0];
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if (index + 2 > info->entries)
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return;
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buf[index + 1] = ret;
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buf[0] = index + 1;
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}
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static bool
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trace_cmp(uint64_t type, uint64_t arg1, uint64_t arg2, uint64_t ret)
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{
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struct thread *td;
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struct kcov_info *info;
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uint64_t *buf, index;
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td = curthread;
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info = get_kinfo(td);
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if (info == NULL)
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return (false);
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/*
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* Check we are in the comparison-trace mode.
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*/
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if (info->mode != KCOV_MODE_TRACE_CMP)
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return (false);
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KASSERT(info->kvaddr != 0,
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("__sanitizer_cov_trace_pc: NULL buf while running"));
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buf = (uint64_t *)info->kvaddr;
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/* The first entry of the buffer holds the index */
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index = buf[0];
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/* Check we have space to store all elements */
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if (index * 4 + 4 + 1 > info->entries)
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return (false);
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buf[index * 4 + 1] = type;
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buf[index * 4 + 2] = arg1;
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buf[index * 4 + 3] = arg2;
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buf[index * 4 + 4] = ret;
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buf[0] = index + 1;
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return (true);
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}
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/*
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* The fd is being closed, cleanup everything we can.
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*/
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static void
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kcov_mmap_cleanup(void *arg)
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{
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struct kcov_info *info = arg;
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struct thread *thread;
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mtx_lock_spin(&kcov_lock);
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/*
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* Move to KCOV_STATE_DYING to stop adding new entries.
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*
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* If the thread is running we need to wait until thread exit to
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* clean up as it may currently be adding a new entry. If this is
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* the case being in KCOV_STATE_DYING will signal that the buffer
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* needs to be cleaned up.
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*/
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atomic_store_int(&info->state, KCOV_STATE_DYING);
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atomic_thread_fence_seq_cst();
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thread = info->thread;
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mtx_unlock_spin(&kcov_lock);
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if (thread != NULL)
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return;
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/*
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* We can safely clean up the info struct as it is in the
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* KCOV_STATE_DYING state with no thread associated.
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*
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* The KCOV_STATE_DYING stops new threads from using it.
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* The lack of a thread means nothing is currently using the buffers.
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*/
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if (info->kvaddr != 0) {
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pmap_qremove(info->kvaddr, info->bufsize / PAGE_SIZE);
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kva_free(info->kvaddr, info->bufsize);
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}
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if (info->bufobj != NULL && !info->mmap)
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vm_object_deallocate(info->bufobj);
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free(info, M_KCOV_INFO);
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}
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static int
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kcov_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
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{
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struct kcov_info *info;
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int error;
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info = malloc(sizeof(struct kcov_info), M_KCOV_INFO, M_ZERO | M_WAITOK);
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info->state = KCOV_STATE_OPEN;
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info->thread = NULL;
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info->mode = -1;
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info->mmap = false;
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if ((error = devfs_set_cdevpriv(info, kcov_mmap_cleanup)) != 0)
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kcov_mmap_cleanup(info);
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return (error);
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}
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static int
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kcov_close(struct cdev *dev, int fflag, int devtype, struct thread *td)
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{
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struct kcov_info *info;
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int error;
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if ((error = devfs_get_cdevpriv((void **)&info)) != 0)
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return (error);
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KASSERT(info != NULL, ("kcov_close with no kcov_info structure"));
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/* Trying to close, but haven't disabled */
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if (info->state == KCOV_STATE_RUNNING)
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return (EBUSY);
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return (0);
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}
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static int
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kcov_mmap_single(struct cdev *dev, vm_ooffset_t *offset, vm_size_t size,
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struct vm_object **object, int nprot)
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{
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struct kcov_info *info;
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int error;
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if ((nprot & (PROT_EXEC | PROT_READ | PROT_WRITE)) !=
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(PROT_READ | PROT_WRITE))
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return (EINVAL);
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if ((error = devfs_get_cdevpriv((void **)&info)) != 0)
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return (error);
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if (info->kvaddr == 0 || size / KCOV_ELEMENT_SIZE != info->entries ||
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info->mmap != false)
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return (EINVAL);
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info->mmap = true;
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*offset = 0;
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*object = info->bufobj;
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return (0);
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}
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static int
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kcov_alloc(struct kcov_info *info, size_t entries)
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{
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size_t n, pages;
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vm_page_t *m;
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KASSERT(info->kvaddr == 0, ("kcov_alloc: Already have a buffer"));
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KASSERT(info->state == KCOV_STATE_OPEN,
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("kcov_alloc: Not in open state (%x)", info->state));
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if (entries < 2 || entries > kcov_max_entries)
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return (EINVAL);
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/* Align to page size so mmap can't access other kernel memory */
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info->bufsize = roundup2(entries * KCOV_ELEMENT_SIZE, PAGE_SIZE);
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pages = info->bufsize / PAGE_SIZE;
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if ((info->kvaddr = kva_alloc(info->bufsize)) == 0)
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return (ENOMEM);
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info->bufobj = vm_pager_allocate(OBJT_PHYS, 0, info->bufsize,
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PROT_READ | PROT_WRITE, 0, curthread->td_ucred);
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m = malloc(sizeof(*m) * pages, M_TEMP, M_WAITOK);
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VM_OBJECT_WLOCK(info->bufobj);
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for (n = 0; n < pages; n++) {
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m[n] = vm_page_grab(info->bufobj, n,
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VM_ALLOC_NOBUSY | VM_ALLOC_ZERO | VM_ALLOC_WIRED);
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m[n]->valid = VM_PAGE_BITS_ALL;
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}
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VM_OBJECT_WUNLOCK(info->bufobj);
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pmap_qenter(info->kvaddr, m, pages);
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free(m, M_TEMP);
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info->entries = entries;
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return (0);
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}
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static int
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kcov_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag __unused,
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struct thread *td)
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{
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struct kcov_info *info;
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int mode, error;
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if ((error = devfs_get_cdevpriv((void **)&info)) != 0)
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return (error);
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if (cmd == KIOSETBUFSIZE) {
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/*
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* Set the size of the coverage buffer. Should be called
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* before enabling coverage collection for that thread.
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*/
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if (info->state != KCOV_STATE_OPEN) {
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return (EBUSY);
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}
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error = kcov_alloc(info, *(u_int *)data);
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if (error == 0)
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info->state = KCOV_STATE_READY;
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return (error);
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}
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mtx_lock_spin(&kcov_lock);
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switch (cmd) {
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case KIOENABLE:
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if (info->state != KCOV_STATE_READY) {
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error = EBUSY;
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break;
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}
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if (td->td_kcov_info != NULL) {
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error = EINVAL;
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break;
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}
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mode = *(int *)data;
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if (mode != KCOV_MODE_TRACE_PC && mode != KCOV_MODE_TRACE_CMP) {
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error = EINVAL;
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break;
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}
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/* Lets hope nobody opens this 2 billion times */
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KASSERT(active_count < INT_MAX,
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("%s: Open too many times", __func__));
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active_count++;
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if (active_count == 1) {
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cov_register_pc(&trace_pc);
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cov_register_cmp(&trace_cmp);
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}
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KASSERT(info->thread == NULL,
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("Enabling kcov when already enabled"));
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info->thread = td;
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info->mode = mode;
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/*
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* Ensure the mode has been set before starting coverage
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* tracing.
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*/
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atomic_store_rel_int(&info->state, KCOV_STATE_RUNNING);
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td->td_kcov_info = info;
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break;
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case KIODISABLE:
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/* Only the currently enabled thread may disable itself */
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if (info->state != KCOV_STATE_RUNNING ||
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info != td->td_kcov_info) {
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error = EINVAL;
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break;
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}
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KASSERT(active_count > 0, ("%s: Open count is zero", __func__));
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active_count--;
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if (active_count == 0) {
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cov_unregister_pc();
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cov_unregister_cmp();
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}
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td->td_kcov_info = NULL;
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atomic_store_int(&info->state, KCOV_STATE_READY);
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/*
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* Ensure we have exited the READY state before clearing the
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* rest of the info struct.
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*/
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atomic_thread_fence_rel();
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info->mode = -1;
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info->thread = NULL;
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break;
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default:
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error = EINVAL;
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break;
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}
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mtx_unlock_spin(&kcov_lock);
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return (error);
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}
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static void
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kcov_thread_dtor(void *arg __unused, struct thread *td)
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{
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struct kcov_info *info;
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info = td->td_kcov_info;
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if (info == NULL)
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return;
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mtx_lock_spin(&kcov_lock);
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KASSERT(active_count > 0, ("%s: Open count is zero", __func__));
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active_count--;
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if (active_count == 0) {
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cov_unregister_pc();
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cov_unregister_cmp();
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}
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td->td_kcov_info = NULL;
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if (info->state != KCOV_STATE_DYING) {
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/*
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* The kcov file is still open. Mark it as unused and
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* wait for it to be closed before cleaning up.
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*/
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|
atomic_store_int(&info->state, KCOV_STATE_READY);
|
|
atomic_thread_fence_seq_cst();
|
|
/* This info struct is unused */
|
|
info->thread = NULL;
|
|
mtx_unlock_spin(&kcov_lock);
|
|
return;
|
|
}
|
|
mtx_unlock_spin(&kcov_lock);
|
|
|
|
/*
|
|
* We can safely clean up the info struct as it is in the
|
|
* KCOV_STATE_DYING state where the info struct is associated with
|
|
* the current thread that's about to exit.
|
|
*
|
|
* The KCOV_STATE_DYING stops new threads from using it.
|
|
* It also stops the current thread from trying to use the info struct.
|
|
*/
|
|
|
|
if (info->kvaddr != 0) {
|
|
pmap_qremove(info->kvaddr, info->bufsize / PAGE_SIZE);
|
|
kva_free(info->kvaddr, info->bufsize);
|
|
}
|
|
if (info->bufobj != NULL && !info->mmap)
|
|
vm_object_deallocate(info->bufobj);
|
|
free(info, M_KCOV_INFO);
|
|
}
|
|
|
|
static void
|
|
kcov_init(const void *unused)
|
|
{
|
|
struct make_dev_args args;
|
|
struct cdev *dev;
|
|
|
|
mtx_init(&kcov_lock, "kcov lock", NULL, MTX_SPIN);
|
|
|
|
make_dev_args_init(&args);
|
|
args.mda_devsw = &kcov_cdevsw;
|
|
args.mda_uid = UID_ROOT;
|
|
args.mda_gid = GID_WHEEL;
|
|
args.mda_mode = 0600;
|
|
if (make_dev_s(&args, &dev, "kcov") != 0) {
|
|
printf("%s", "Failed to create kcov device");
|
|
return;
|
|
}
|
|
|
|
EVENTHANDLER_REGISTER(thread_dtor, kcov_thread_dtor, NULL,
|
|
EVENTHANDLER_PRI_ANY);
|
|
}
|
|
|
|
SYSINIT(kcovdev, SI_SUB_LAST, SI_ORDER_ANY, kcov_init, NULL);
|