text: // 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;
  	}
  
  	get_online_cpus();
  	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");
  	put_online_cpus();
  
  	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);
  }
  