// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 * Copyright (C) IBM Corporation, 2005
 *               Jeff Muizelaar, 2006, 2007
 *               Pekka Paalanen, 2008 <pq@iki.fi>
 *
 * Derived from the read-mod example from relay-examples by Tom Zanussi.
 */

#define pr_fmt(fmt) "mmiotrace: " fmt

#include <linux/moduleparam.h>
#include <linux/debugfs.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/mmiotrace.h>
#include <linux/pgtable.h>
#include <asm/e820/api.h> /* for ISA_START_ADDRESS */
#include <linux/atomic.h>
#include <linux/percpu.h>
#include <linux/cpu.h>

#include "pf_in.h"

struct trap_reason {
        unsigned long addr;
        unsigned long ip;
        enum reason_type type;
        int active_traces;
};

struct remap_trace {
        struct list_head list;
        struct kmmio_probe probe;
        resource_size_t phys;
        unsigned long id;
};

/* Accessed per-cpu. */
static DEFINE_PER_CPU(struct trap_reason, pf_reason);
static DEFINE_PER_CPU(struct mmiotrace_rw, cpu_trace);

static DEFINE_MUTEX(mmiotrace_mutex);
static DEFINE_SPINLOCK(trace_lock);
static atomic_t mmiotrace_enabled;
static LIST_HEAD(trace_list);           /* struct remap_trace */

/*
 * Locking in this file:
 * - mmiotrace_mutex enforces enable/disable_mmiotrace() critical sections.
 * - mmiotrace_enabled may be modified only when holding mmiotrace_mutex
 *   and trace_lock.
 * - Routines depending on is_enabled() must take trace_lock.
 * - trace_list users must hold trace_lock.
 * - is_enabled() guarantees that mmio_trace_{rw,mapping} are allowed.
 * - pre/post callbacks assume the effect of is_enabled() being true.
 */

/* module parameters */
static unsigned long    filter_offset;
static bool             nommiotrace;
static bool             trace_pc;

module_param(filter_offset, ulong, 0);
module_param(nommiotrace, bool, 0);
module_param(trace_pc, bool, 0);

MODULE_PARM_DESC(filter_offset, "Start address of traced mappings.");
MODULE_PARM_DESC(nommiotrace, "Disable actual MMIO tracing.");
MODULE_PARM_DESC(trace_pc, "Record address of faulting instructions.");

static bool is_enabled(void)
{
        return atomic_read(&mmiotrace_enabled);
}

static void print_pte(unsigned long address)
{
        unsigned int level;
        pte_t *pte = lookup_address(address, &level);

        if (!pte) {
                pr_err("Error in %s: no pte for page 0x%08lx\n",
                       __func__, address);
                return;
        }

        if (level == PG_LEVEL_2M) {
                pr_emerg("4MB pages are not currently supported: 0x%08lx\n",
                         address);
                BUG();
        }
        pr_info("pte for 0x%lx: 0x%llx 0x%llx\n",
                address,
                (unsigned long long)pte_val(*pte),
                (unsigned long long)pte_val(*pte) & _PAGE_PRESENT);
}

/*
 * For some reason the pre/post pairs have been called in an
 * unmatched order. Report and die.
 */
static void die_kmmio_nesting_error(struct pt_regs *regs, unsigned long addr)
{
        const struct trap_reason *my_reason = &get_cpu_var(pf_reason);
        pr_emerg("unexpected fault for address: 0x%08lx, last fault for address: 0x%08lx\n",
                 addr, my_reason->addr);
        print_pte(addr);
        pr_emerg("faulting IP is at %pS\n", (void *)regs->ip);
        pr_emerg("last faulting IP was at %pS\n", (void *)my_reason->ip);
#ifdef __i386__
        pr_emerg("eax: %08lx   ebx: %08lx   ecx: %08lx   edx: %08lx\n",
                 regs->ax, regs->bx, regs->cx, regs->dx);
        pr_emerg("esi: %08lx   edi: %08lx   ebp: %08lx   esp: %08lx\n",
                 regs->si, regs->di, regs->bp, regs->sp);
#else
        pr_emerg("rax: %016lx   rcx: %016lx   rdx: %016lx\n",
                 regs->ax, regs->cx, regs->dx);
        pr_emerg("rsi: %016lx   rdi: %016lx   rbp: %016lx   rsp: %016lx\n",
                 regs->si, regs->di, regs->bp, regs->sp);
#endif
        put_cpu_var(pf_reason);
        BUG();
}

static void pre(struct kmmio_probe *p, struct pt_regs *regs,
                                                unsigned long addr)
{
        struct trap_reason *my_reason = &get_cpu_var(pf_reason);
        struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);
        const unsigned long instptr = instruction_pointer(regs);
        const enum reason_type type = get_ins_type(instptr);
        struct remap_trace *trace = p->private;

        /* it doesn't make sense to have more than one active trace per cpu */
        if (my_reason->active_traces)
                die_kmmio_nesting_error(regs, addr);
        else
                my_reason->active_traces++;

        my_reason->type = type;
        my_reason->addr = addr;
        my_reason->ip = instptr;

        my_trace->phys = addr - trace->probe.addr + trace->phys;
        my_trace->map_id = trace->id;

        /*
         * Only record the program counter when requested.
         * It may taint clean-room reverse engineering.
         */
        if (trace_pc)
                my_trace->pc = instptr;
        else
                my_trace->pc = 0;

        /*
         * XXX: the timestamp recorded will be *after* the tracing has been
         * done, not at the time we hit the instruction. SMP implications
         * on event ordering?
         */

        switch (type) {
        case REG_READ:
                my_trace->opcode = MMIO_READ;
                my_trace->width = get_ins_mem_width(instptr);
                break;
        case REG_WRITE:
                my_trace->opcode = MMIO_WRITE;
                my_trace->width = get_ins_mem_width(instptr);
                my_trace->value = get_ins_reg_val(instptr, regs);
                break;
        case IMM_WRITE:
                my_trace->opcode = MMIO_WRITE;
                my_trace->width = get_ins_mem_width(instptr);
                my_trace->value = get_ins_imm_val(instptr);
                break;
        default:
                {
                        unsigned char *ip = (unsigned char *)instptr;
                        my_trace->opcode = MMIO_UNKNOWN_OP;
                        my_trace->width = 0;
                        my_trace->value = (*ip) << 16 | *(ip + 1) << 8 |
                                                                *(ip + 2);
                }
        }
        put_cpu_var(cpu_trace);
        put_cpu_var(pf_reason);
}

static void post(struct kmmio_probe *p, unsigned long condition,
                                                        struct pt_regs *regs)
{
        struct trap_reason *my_reason = &get_cpu_var(pf_reason);
        struct mmiotrace_rw *my_trace = &get_cpu_var(cpu_trace);

        /* this should always return the active_trace count to 0 */
        my_reason->active_traces--;
        if (my_reason->active_traces) {
                pr_emerg("unexpected post handler");
                BUG();
        }

        switch (my_reason->type) {
        case REG_READ:
                my_trace->value = get_ins_reg_val(my_reason->ip, regs);
                break;
        default:
                break;
        }

        mmio_trace_rw(my_trace);
        put_cpu_var(cpu_trace);
        put_cpu_var(pf_reason);
}

static void ioremap_trace_core(resource_size_t offset, unsigned long size,
                                                        void __iomem *addr)
{
        static atomic_t next_id;
        struct remap_trace *trace = kmalloc(sizeof(*trace), GFP_KERNEL);
        /* These are page-unaligned. */
        struct mmiotrace_map map = {
                .phys = offset,
                .virt = (unsigned long)addr,
                .len = size,
                .opcode = MMIO_PROBE
        };

        if (!trace) {
                pr_err("kmalloc failed in ioremap\n");
                return;
        }

        *trace = (struct remap_trace) {
                .probe = {
                        .addr = (unsigned long)addr,
                        .len = size,
                        .pre_handler = pre,
                        .post_handler = post,
                        .private = trace
                },
                .phys = offset,
                .id = atomic_inc_return(&next_id)
        };
        map.map_id = trace->id;

        spin_lock_irq(&trace_lock);
        if (!is_enabled()) {
                kfree(trace);
                goto not_enabled;
        }

        mmio_trace_mapping(&map);
        list_add_tail(&trace->list, &trace_list);
        if (!nommiotrace)
                register_kmmio_probe(&trace->probe);

not_enabled:
        spin_unlock_irq(&trace_lock);
}

void mmiotrace_ioremap(resource_size_t offset, unsigned long size,
                                                void __iomem *addr)
{
        if (!is_enabled()) /* recheck and proper locking in *_core() */
                return;

        pr_debug("ioremap_*(0x%llx, 0x%lx) = %p\n",
                 (unsigned long long)offset, size, addr);
        if ((filter_offset) && (offset != filter_offset))
                return;
        ioremap_trace_core(offset, size, addr);
}

static void iounmap_trace_core(volatile void __iomem *addr)
{
        struct mmiotrace_map map = {
                .phys = 0,
                .virt = (unsigned long)addr,
                .len = 0,
                .opcode = MMIO_UNPROBE
        };
        struct remap_trace *trace;
        struct remap_trace *tmp;
        struct remap_trace *found_trace = NULL;

        pr_debug("Unmapping %p.\n", addr);

        spin_lock_irq(&trace_lock);
        if (!is_enabled())
                goto not_enabled;

        list_for_each_entry_safe(trace, tmp, &trace_list, list) {
                if ((unsigned long)addr == trace->probe.addr) {
                        if (!nommiotrace)
                                unregister_kmmio_probe(&trace->probe);
                        list_del(&trace->list);
                        found_trace = trace;
                        break;
                }
        }
        map.map_id = (found_trace) ? found_trace->id : -1;
        mmio_trace_mapping(&map);

not_enabled:
        spin_unlock_irq(&trace_lock);
        if (found_trace) {
                synchronize_rcu(); /* unregister_kmmio_probe() requirement */
                kfree(found_trace);
        }
}

void mmiotrace_iounmap(volatile void __iomem *addr)
{
        might_sleep();
        if (is_enabled()) /* recheck and proper locking in *_core() */
                iounmap_trace_core(addr);
}

int mmiotrace_printk(const char *fmt, ...)
{
        int ret = 0;
        va_list args;
        unsigned long flags;
        va_start(args, fmt);

        spin_lock_irqsave(&trace_lock, flags);
        if (is_enabled())
                ret = mmio_trace_printk(fmt, args);
        spin_unlock_irqrestore(&trace_lock, flags);

        va_end(args);
        return ret;
}
EXPORT_SYMBOL(mmiotrace_printk);

static void clear_trace_list(void)
{
        struct remap_trace *trace;
        struct remap_trace *tmp;

        /*
         * No locking required, because the caller ensures we are in a
         * critical section via mutex, and is_enabled() is false,
         * i.e. nothing can traverse or modify this list.
         * Caller also ensures is_enabled() cannot change.
         */
        list_for_each_entry(trace, &trace_list, list) {
                pr_notice("purging non-iounmapped trace @0x%08lx, size 0x%lx.\n",
                          trace->probe.addr, trace->probe.len);
                if (!nommiotrace)
                        unregister_kmmio_probe(&trace->probe);
        }
        synchronize_rcu(); /* unregister_kmmio_probe() requirement */

        list_for_each_entry_safe(trace, tmp, &trace_list, list) {
                list_del(&trace->list);
                kfree(trace);
        }
}

#ifdef CONFIG_HOTPLUG_CPU
static cpumask_var_t downed_cpus;

static void enter_uniprocessor(void)
{
        int cpu;
        int err;

        if (!cpumask_available(downed_cpus) &&
            !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
                pr_notice("Failed to allocate mask\n");
                goto out;
        }

        cpus_read_lock();
        cpumask_copy(downed_cpus, cpu_online_mask);
        cpumask_clear_cpu(cpumask_first(cpu_online_mask), downed_cpus);
        if (num_online_cpus() > 1)
                pr_notice("Disabling non-boot CPUs...\n");
        cpus_read_unlock();

        for_each_cpu(cpu, downed_cpus) {
                err = remove_cpu(cpu);
                if (!err)
                        pr_info("CPU%d is down.\n", cpu);
                else
                        pr_err("Error taking CPU%d down: %d\n", cpu, err);
        }
out:
        if (num_online_cpus() > 1)
                pr_warn("multiple CPUs still online, may miss events.\n");
}

static void leave_uniprocessor(void)
{
        int cpu;
        int err;

        if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
                return;
        pr_notice("Re-enabling CPUs...\n");
        for_each_cpu(cpu, downed_cpus) {
                err = add_cpu(cpu);
                if (!err)
                        pr_info("enabled CPU%d.\n", cpu);
                else
                        pr_err("cannot re-enable CPU%d: %d\n", cpu, err);
        }
}

#else /* !CONFIG_HOTPLUG_CPU */
static void enter_uniprocessor(void)
{
        if (num_online_cpus() > 1)
                pr_warn("multiple CPUs are online, may miss events. "
                        "Suggest booting with maxcpus=1 kernel argument.\n");
}

static void leave_uniprocessor(void)
{
}
#endif

void enable_mmiotrace(void)
{
        mutex_lock(&mmiotrace_mutex);
        if (is_enabled())
                goto out;

        if (nommiotrace)
                pr_info("MMIO tracing disabled.\n");
        kmmio_init();
        enter_uniprocessor();
        spin_lock_irq(&trace_lock);
        atomic_inc(&mmiotrace_enabled);
        spin_unlock_irq(&trace_lock);
        pr_info("enabled.\n");
out:
        mutex_unlock(&mmiotrace_mutex);
}

void disable_mmiotrace(void)
{
        mutex_lock(&mmiotrace_mutex);
        if (!is_enabled())
                goto out;

        spin_lock_irq(&trace_lock);
        atomic_dec(&mmiotrace_enabled);
        BUG_ON(is_enabled());
        spin_unlock_irq(&trace_lock);

        clear_trace_list(); /* guarantees: no more kmmio callbacks */
        leave_uniprocessor();
        kmmio_cleanup();
        pr_info("disabled.\n");
out:
        mutex_unlock(&mmiotrace_mutex);
}