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-rw-r--r--arch/x86/mm/kmmio.c510
1 files changed, 510 insertions, 0 deletions
diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
new file mode 100644
index 000000000000..93d82038af4b
--- /dev/null
+++ b/arch/x86/mm/kmmio.c
@@ -0,0 +1,510 @@
+/* Support for MMIO probes.
+ * Benfit many code from kprobes
+ * (C) 2002 Louis Zhuang <louis.zhuang@intel.com>.
+ * 2007 Alexander Eichner
+ * 2008 Pekka Paalanen <pq@iki.fi>
+ */
+
+#include <linux/list.h>
+#include <linux/rculist.h>
+#include <linux/spinlock.h>
+#include <linux/hash.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/uaccess.h>
+#include <linux/ptrace.h>
+#include <linux/preempt.h>
+#include <linux/percpu.h>
+#include <linux/kdebug.h>
+#include <linux/mutex.h>
+#include <linux/io.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+#include <linux/errno.h>
+#include <asm/debugreg.h>
+#include <linux/mmiotrace.h>
+
+#define KMMIO_PAGE_HASH_BITS 4
+#define KMMIO_PAGE_TABLE_SIZE (1 << KMMIO_PAGE_HASH_BITS)
+
+struct kmmio_fault_page {
+ struct list_head list;
+ struct kmmio_fault_page *release_next;
+ unsigned long page; /* location of the fault page */
+
+ /*
+ * Number of times this page has been registered as a part
+ * of a probe. If zero, page is disarmed and this may be freed.
+ * Used only by writers (RCU).
+ */
+ int count;
+};
+
+struct kmmio_delayed_release {
+ struct rcu_head rcu;
+ struct kmmio_fault_page *release_list;
+};
+
+struct kmmio_context {
+ struct kmmio_fault_page *fpage;
+ struct kmmio_probe *probe;
+ unsigned long saved_flags;
+ unsigned long addr;
+ int active;
+};
+
+static DEFINE_SPINLOCK(kmmio_lock);
+
+/* Protected by kmmio_lock */
+unsigned int kmmio_count;
+
+/* Read-protected by RCU, write-protected by kmmio_lock. */
+static struct list_head kmmio_page_table[KMMIO_PAGE_TABLE_SIZE];
+static LIST_HEAD(kmmio_probes);
+
+static struct list_head *kmmio_page_list(unsigned long page)
+{
+ return &kmmio_page_table[hash_long(page, KMMIO_PAGE_HASH_BITS)];
+}
+
+/* Accessed per-cpu */
+static DEFINE_PER_CPU(struct kmmio_context, kmmio_ctx);
+
+/*
+ * this is basically a dynamic stabbing problem:
+ * Could use the existing prio tree code or
+ * Possible better implementations:
+ * The Interval Skip List: A Data Structure for Finding All Intervals That
+ * Overlap a Point (might be simple)
+ * Space Efficient Dynamic Stabbing with Fast Queries - Mikkel Thorup
+ */
+/* Get the kmmio at this addr (if any). You must be holding RCU read lock. */
+static struct kmmio_probe *get_kmmio_probe(unsigned long addr)
+{
+ struct kmmio_probe *p;
+ list_for_each_entry_rcu(p, &kmmio_probes, list) {
+ if (addr >= p->addr && addr <= (p->addr + p->len))
+ return p;
+ }
+ return NULL;
+}
+
+/* You must be holding RCU read lock. */
+static struct kmmio_fault_page *get_kmmio_fault_page(unsigned long page)
+{
+ struct list_head *head;
+ struct kmmio_fault_page *p;
+
+ page &= PAGE_MASK;
+ head = kmmio_page_list(page);
+ list_for_each_entry_rcu(p, head, list) {
+ if (p->page == page)
+ return p;
+ }
+ return NULL;
+}
+
+static void set_page_present(unsigned long addr, bool present,
+ unsigned int *pglevel)
+{
+ pteval_t pteval;
+ pmdval_t pmdval;
+ unsigned int level;
+ pmd_t *pmd;
+ pte_t *pte = lookup_address(addr, &level);
+
+ if (!pte) {
+ pr_err("kmmio: no pte for page 0x%08lx\n", addr);
+ return;
+ }
+
+ if (pglevel)
+ *pglevel = level;
+
+ switch (level) {
+ case PG_LEVEL_2M:
+ pmd = (pmd_t *)pte;
+ pmdval = pmd_val(*pmd) & ~_PAGE_PRESENT;
+ if (present)
+ pmdval |= _PAGE_PRESENT;
+ set_pmd(pmd, __pmd(pmdval));
+ break;
+
+ case PG_LEVEL_4K:
+ pteval = pte_val(*pte) & ~_PAGE_PRESENT;
+ if (present)
+ pteval |= _PAGE_PRESENT;
+ set_pte_atomic(pte, __pte(pteval));
+ break;
+
+ default:
+ pr_err("kmmio: unexpected page level 0x%x.\n", level);
+ return;
+ }
+
+ __flush_tlb_one(addr);
+}
+
+/** Mark the given page as not present. Access to it will trigger a fault. */
+static void arm_kmmio_fault_page(unsigned long page, unsigned int *pglevel)
+{
+ set_page_present(page & PAGE_MASK, false, pglevel);
+}
+
+/** Mark the given page as present. */
+static void disarm_kmmio_fault_page(unsigned long page, unsigned int *pglevel)
+{
+ set_page_present(page & PAGE_MASK, true, pglevel);
+}
+
+/*
+ * This is being called from do_page_fault().
+ *
+ * We may be in an interrupt or a critical section. Also prefecthing may
+ * trigger a page fault. We may be in the middle of process switch.
+ * We cannot take any locks, because we could be executing especially
+ * within a kmmio critical section.
+ *
+ * Local interrupts are disabled, so preemption cannot happen.
+ * Do not enable interrupts, do not sleep, and watch out for other CPUs.
+ */
+/*
+ * Interrupts are disabled on entry as trap3 is an interrupt gate
+ * and they remain disabled thorough out this function.
+ */
+int kmmio_handler(struct pt_regs *regs, unsigned long addr)
+{
+ struct kmmio_context *ctx;
+ struct kmmio_fault_page *faultpage;
+ int ret = 0; /* default to fault not handled */
+
+ /*
+ * Preemption is now disabled to prevent process switch during
+ * single stepping. We can only handle one active kmmio trace
+ * per cpu, so ensure that we finish it before something else
+ * gets to run. We also hold the RCU read lock over single
+ * stepping to avoid looking up the probe and kmmio_fault_page
+ * again.
+ */
+ preempt_disable();
+ rcu_read_lock();
+
+ faultpage = get_kmmio_fault_page(addr);
+ if (!faultpage) {
+ /*
+ * Either this page fault is not caused by kmmio, or
+ * another CPU just pulled the kmmio probe from under
+ * our feet. The latter case should not be possible.
+ */
+ goto no_kmmio;
+ }
+
+ ctx = &get_cpu_var(kmmio_ctx);
+ if (ctx->active) {
+ disarm_kmmio_fault_page(faultpage->page, NULL);
+ if (addr == ctx->addr) {
+ /*
+ * On SMP we sometimes get recursive probe hits on the
+ * same address. Context is already saved, fall out.
+ */
+ pr_debug("kmmio: duplicate probe hit on CPU %d, for "
+ "address 0x%08lx.\n",
+ smp_processor_id(), addr);
+ ret = 1;
+ goto no_kmmio_ctx;
+ }
+ /*
+ * Prevent overwriting already in-flight context.
+ * This should not happen, let's hope disarming at least
+ * prevents a panic.
+ */
+ pr_emerg("kmmio: recursive probe hit on CPU %d, "
+ "for address 0x%08lx. Ignoring.\n",
+ smp_processor_id(), addr);
+ pr_emerg("kmmio: previous hit was at 0x%08lx.\n",
+ ctx->addr);
+ goto no_kmmio_ctx;
+ }
+ ctx->active++;
+
+ ctx->fpage = faultpage;
+ ctx->probe = get_kmmio_probe(addr);
+ ctx->saved_flags = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF));
+ ctx->addr = addr;
+
+ if (ctx->probe && ctx->probe->pre_handler)
+ ctx->probe->pre_handler(ctx->probe, regs, addr);
+
+ /*
+ * Enable single-stepping and disable interrupts for the faulting
+ * context. Local interrupts must not get enabled during stepping.
+ */
+ regs->flags |= X86_EFLAGS_TF;
+ regs->flags &= ~X86_EFLAGS_IF;
+
+ /* Now we set present bit in PTE and single step. */
+ disarm_kmmio_fault_page(ctx->fpage->page, NULL);
+
+ /*
+ * If another cpu accesses the same page while we are stepping,
+ * the access will not be caught. It will simply succeed and the
+ * only downside is we lose the event. If this becomes a problem,
+ * the user should drop to single cpu before tracing.
+ */
+
+ put_cpu_var(kmmio_ctx);
+ return 1; /* fault handled */
+
+no_kmmio_ctx:
+ put_cpu_var(kmmio_ctx);
+no_kmmio:
+ rcu_read_unlock();
+ preempt_enable_no_resched();
+ return ret;
+}
+
+/*
+ * Interrupts are disabled on entry as trap1 is an interrupt gate
+ * and they remain disabled thorough out this function.
+ * This must always get called as the pair to kmmio_handler().
+ */
+static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
+{
+ int ret = 0;
+ struct kmmio_context *ctx = &get_cpu_var(kmmio_ctx);
+
+ if (!ctx->active) {
+ pr_debug("kmmio: spurious debug trap on CPU %d.\n",
+ smp_processor_id());
+ goto out;
+ }
+
+ if (ctx->probe && ctx->probe->post_handler)
+ ctx->probe->post_handler(ctx->probe, condition, regs);
+
+ arm_kmmio_fault_page(ctx->fpage->page, NULL);
+
+ regs->flags &= ~X86_EFLAGS_TF;
+ regs->flags |= ctx->saved_flags;
+
+ /* These were acquired in kmmio_handler(). */
+ ctx->active--;
+ BUG_ON(ctx->active);
+ rcu_read_unlock();
+ preempt_enable_no_resched();
+
+ /*
+ * if somebody else is singlestepping across a probe point, flags
+ * will have TF set, in which case, continue the remaining processing
+ * of do_debug, as if this is not a probe hit.
+ */
+ if (!(regs->flags & X86_EFLAGS_TF))
+ ret = 1;
+out:
+ put_cpu_var(kmmio_ctx);
+ return ret;
+}
+
+/* You must be holding kmmio_lock. */
+static int add_kmmio_fault_page(unsigned long page)
+{
+ struct kmmio_fault_page *f;
+
+ page &= PAGE_MASK;
+ f = get_kmmio_fault_page(page);
+ if (f) {
+ if (!f->count)
+ arm_kmmio_fault_page(f->page, NULL);
+ f->count++;
+ return 0;
+ }
+
+ f = kmalloc(sizeof(*f), GFP_ATOMIC);
+ if (!f)
+ return -1;
+
+ f->count = 1;
+ f->page = page;
+ list_add_rcu(&f->list, kmmio_page_list(f->page));
+
+ arm_kmmio_fault_page(f->page, NULL);
+
+ return 0;
+}
+
+/* You must be holding kmmio_lock. */
+static void release_kmmio_fault_page(unsigned long page,
+ struct kmmio_fault_page **release_list)
+{
+ struct kmmio_fault_page *f;
+
+ page &= PAGE_MASK;
+ f = get_kmmio_fault_page(page);
+ if (!f)
+ return;
+
+ f->count--;
+ BUG_ON(f->count < 0);
+ if (!f->count) {
+ disarm_kmmio_fault_page(f->page, NULL);
+ f->release_next = *release_list;
+ *release_list = f;
+ }
+}
+
+/*
+ * With page-unaligned ioremaps, one or two armed pages may contain
+ * addresses from outside the intended mapping. Events for these addresses
+ * are currently silently dropped. The events may result only from programming
+ * mistakes by accessing addresses before the beginning or past the end of a
+ * mapping.
+ */
+int register_kmmio_probe(struct kmmio_probe *p)
+{
+ unsigned long flags;
+ int ret = 0;
+ unsigned long size = 0;
+ const unsigned long size_lim = p->len + (p->addr & ~PAGE_MASK);
+
+ spin_lock_irqsave(&kmmio_lock, flags);
+ if (get_kmmio_probe(p->addr)) {
+ ret = -EEXIST;
+ goto out;
+ }
+ kmmio_count++;
+ list_add_rcu(&p->list, &kmmio_probes);
+ while (size < size_lim) {
+ if (add_kmmio_fault_page(p->addr + size))
+ pr_err("kmmio: Unable to set page fault.\n");
+ size += PAGE_SIZE;
+ }
+out:
+ spin_unlock_irqrestore(&kmmio_lock, flags);
+ /*
+ * XXX: What should I do here?
+ * Here was a call to global_flush_tlb(), but it does not exist
+ * anymore. It seems it's not needed after all.
+ */
+ return ret;
+}
+EXPORT_SYMBOL(register_kmmio_probe);
+
+static void rcu_free_kmmio_fault_pages(struct rcu_head *head)
+{
+ struct kmmio_delayed_release *dr = container_of(
+ head,
+ struct kmmio_delayed_release,
+ rcu);
+ struct kmmio_fault_page *p = dr->release_list;
+ while (p) {
+ struct kmmio_fault_page *next = p->release_next;
+ BUG_ON(p->count);
+ kfree(p);
+ p = next;
+ }
+ kfree(dr);
+}
+
+static void remove_kmmio_fault_pages(struct rcu_head *head)
+{
+ struct kmmio_delayed_release *dr = container_of(
+ head,
+ struct kmmio_delayed_release,
+ rcu);
+ struct kmmio_fault_page *p = dr->release_list;
+ struct kmmio_fault_page **prevp = &dr->release_list;
+ unsigned long flags;
+ spin_lock_irqsave(&kmmio_lock, flags);
+ while (p) {
+ if (!p->count)
+ list_del_rcu(&p->list);
+ else
+ *prevp = p->release_next;
+ prevp = &p->release_next;
+ p = p->release_next;
+ }
+ spin_unlock_irqrestore(&kmmio_lock, flags);
+ /* This is the real RCU destroy call. */
+ call_rcu(&dr->rcu, rcu_free_kmmio_fault_pages);
+}
+
+/*
+ * Remove a kmmio probe. You have to synchronize_rcu() before you can be
+ * sure that the callbacks will not be called anymore. Only after that
+ * you may actually release your struct kmmio_probe.
+ *
+ * Unregistering a kmmio fault page has three steps:
+ * 1. release_kmmio_fault_page()
+ * Disarm the page, wait a grace period to let all faults finish.
+ * 2. remove_kmmio_fault_pages()
+ * Remove the pages from kmmio_page_table.
+ * 3. rcu_free_kmmio_fault_pages()
+ * Actally free the kmmio_fault_page structs as with RCU.
+ */
+void unregister_kmmio_probe(struct kmmio_probe *p)
+{
+ unsigned long flags;
+ unsigned long size = 0;
+ const unsigned long size_lim = p->len + (p->addr & ~PAGE_MASK);
+ struct kmmio_fault_page *release_list = NULL;
+ struct kmmio_delayed_release *drelease;
+
+ spin_lock_irqsave(&kmmio_lock, flags);
+ while (size < size_lim) {
+ release_kmmio_fault_page(p->addr + size, &release_list);
+ size += PAGE_SIZE;
+ }
+ list_del_rcu(&p->list);
+ kmmio_count--;
+ spin_unlock_irqrestore(&kmmio_lock, flags);
+
+ drelease = kmalloc(sizeof(*drelease), GFP_ATOMIC);
+ if (!drelease) {
+ pr_crit("kmmio: leaking kmmio_fault_page objects.\n");
+ return;
+ }
+ drelease->release_list = release_list;
+
+ /*
+ * This is not really RCU here. We have just disarmed a set of
+ * pages so that they cannot trigger page faults anymore. However,
+ * we cannot remove the pages from kmmio_page_table,
+ * because a probe hit might be in flight on another CPU. The
+ * pages are collected into a list, and they will be removed from
+ * kmmio_page_table when it is certain that no probe hit related to
+ * these pages can be in flight. RCU grace period sounds like a
+ * good choice.
+ *
+ * If we removed the pages too early, kmmio page fault handler might
+ * not find the respective kmmio_fault_page and determine it's not
+ * a kmmio fault, when it actually is. This would lead to madness.
+ */
+ call_rcu(&drelease->rcu, remove_kmmio_fault_pages);
+}
+EXPORT_SYMBOL(unregister_kmmio_probe);
+
+static int kmmio_die_notifier(struct notifier_block *nb, unsigned long val,
+ void *args)
+{
+ struct die_args *arg = args;
+
+ if (val == DIE_DEBUG && (arg->err & DR_STEP))
+ if (post_kmmio_handler(arg->err, arg->regs) == 1)
+ return NOTIFY_STOP;
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block nb_die = {
+ .notifier_call = kmmio_die_notifier
+};
+
+static int __init init_kmmio(void)
+{
+ int i;
+ for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++)
+ INIT_LIST_HEAD(&kmmio_page_table[i]);
+ return register_die_notifier(&nb_die);
+}
+fs_initcall(init_kmmio); /* should be before device_initcall() */
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