x86/mm/kmmio: Switch to arch_spin_lock()
The mmiotrace tracer is "special". The purpose is to help reverse engineer binary drivers by removing the memory allocated by the driver and when the driver goes to access it, a fault occurs, the mmiotracer will record what the driver was doing and then do the work on its behalf by single stepping through the process. But to achieve this ability, it must do some special things. One is it needs to grab a lock while in the breakpoint handler. This is considered an NMI state, and then lockdep warns that the lock is being held in both an NMI state (really a breakpoint handler) and also in normal context. As the breakpoint/NMI state only happens when the driver is accessing memory, there's no concern of a race condition against the setup and tear-down of mmiotracer. To make lockdep and mmiotrace work together, convert the locks used in the breakpoint handler into arch_spin_lock(). Link: https://lkml.kernel.org/r/20221206191229.656244029@goodmis.org Link: https://lore.kernel.org/lkml/20221201213126.620b7dd3@gandalf.local.home/ Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Karol Herbst <karolherbst@gmail.com> Cc: Pekka Paalanen <ppaalanen@gmail.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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@ -62,7 +62,13 @@ struct kmmio_context {
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int active;
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};
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static DEFINE_SPINLOCK(kmmio_lock);
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/*
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* The kmmio_lock is taken in int3 context, which is treated as NMI context.
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* This causes lockdep to complain about it bein in both NMI and normal
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* context. Hide it from lockdep, as it should not have any other locks
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* taken under it, and this is only enabled for debugging mmio anyway.
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*/
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static arch_spinlock_t kmmio_lock = __ARCH_SPIN_LOCK_UNLOCKED;
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/* Protected by kmmio_lock */
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unsigned int kmmio_count;
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@ -346,10 +352,10 @@ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
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ctx->probe->post_handler(ctx->probe, condition, regs);
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/* Prevent racing against release_kmmio_fault_page(). */
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spin_lock(&kmmio_lock);
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arch_spin_lock(&kmmio_lock);
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if (ctx->fpage->count)
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arm_kmmio_fault_page(ctx->fpage);
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spin_unlock(&kmmio_lock);
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arch_spin_unlock(&kmmio_lock);
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regs->flags &= ~X86_EFLAGS_TF;
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regs->flags |= ctx->saved_flags;
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@ -440,7 +446,8 @@ int register_kmmio_probe(struct kmmio_probe *p)
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unsigned int l;
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pte_t *pte;
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spin_lock_irqsave(&kmmio_lock, flags);
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local_irq_save(flags);
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arch_spin_lock(&kmmio_lock);
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if (get_kmmio_probe(addr)) {
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ret = -EEXIST;
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goto out;
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@ -460,7 +467,9 @@ int register_kmmio_probe(struct kmmio_probe *p)
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size += page_level_size(l);
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}
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out:
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spin_unlock_irqrestore(&kmmio_lock, flags);
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arch_spin_unlock(&kmmio_lock);
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local_irq_restore(flags);
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/*
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* XXX: What should I do here?
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* Here was a call to global_flush_tlb(), but it does not exist
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@ -494,7 +503,8 @@ static void remove_kmmio_fault_pages(struct rcu_head *head)
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struct kmmio_fault_page **prevp = &dr->release_list;
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unsigned long flags;
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spin_lock_irqsave(&kmmio_lock, flags);
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local_irq_save(flags);
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arch_spin_lock(&kmmio_lock);
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while (f) {
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if (!f->count) {
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list_del_rcu(&f->list);
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@ -506,7 +516,8 @@ static void remove_kmmio_fault_pages(struct rcu_head *head)
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}
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f = *prevp;
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}
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spin_unlock_irqrestore(&kmmio_lock, flags);
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arch_spin_unlock(&kmmio_lock);
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local_irq_restore(flags);
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/* This is the real RCU destroy call. */
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call_rcu(&dr->rcu, rcu_free_kmmio_fault_pages);
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@ -540,14 +551,16 @@ void unregister_kmmio_probe(struct kmmio_probe *p)
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if (!pte)
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return;
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spin_lock_irqsave(&kmmio_lock, flags);
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local_irq_save(flags);
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arch_spin_lock(&kmmio_lock);
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while (size < size_lim) {
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release_kmmio_fault_page(addr + size, &release_list);
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size += page_level_size(l);
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}
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list_del_rcu(&p->list);
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kmmio_count--;
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spin_unlock_irqrestore(&kmmio_lock, flags);
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arch_spin_unlock(&kmmio_lock);
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local_irq_restore(flags);
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if (!release_list)
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return;
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