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86ec2da037
pmd_present() is expected to test positive after pmdp_mknotpresent() as the PMD entry still points to a valid huge page in memory. pmdp_mknotpresent() implies that given PMD entry is just invalidated from MMU perspective while still holding on to pmd_page() referred valid huge page thus also clearing pmd_present() test. This creates the following situation which is counter intuitive. [pmd_present(pmd_mknotpresent(pmd)) = true] This renames pmd_mknotpresent() as pmd_mkinvalid() reflecting the helper's functionality more accurately while changing the above mentioned situation as follows. This does not create any functional change. [pmd_present(pmd_mkinvalid(pmd)) = true] This is not applicable for platforms that define own pmdp_invalidate() via __HAVE_ARCH_PMDP_INVALIDATE. Suggestion for renaming came during a previous discussion here. https://patchwork.kernel.org/patch/11019637/ [anshuman.khandual@arm.com: change pmd_mknotvalid() to pmd_mkinvalid() per Will] Link: http://lkml.kernel.org/r/1587520326-10099-3-git-send-email-anshuman.khandual@arm.com Suggested-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Will Deacon <will@kernel.org> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Russell King <linux@armlinux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <paulus@samba.org> Link: http://lkml.kernel.org/r/1584680057-13753-3-git-send-email-anshuman.khandual@arm.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
622 lines
16 KiB
C
622 lines
16 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Support for MMIO probes.
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* Benfit many code from kprobes
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* (C) 2002 Louis Zhuang <louis.zhuang@intel.com>.
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* 2007 Alexander Eichner
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* 2008 Pekka Paalanen <pq@iki.fi>
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/list.h>
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#include <linux/rculist.h>
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#include <linux/spinlock.h>
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#include <linux/hash.h>
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#include <linux/export.h>
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#include <linux/kernel.h>
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#include <linux/uaccess.h>
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#include <linux/ptrace.h>
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#include <linux/preempt.h>
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#include <linux/percpu.h>
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#include <linux/kdebug.h>
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#include <linux/mutex.h>
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#include <linux/io.h>
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#include <linux/slab.h>
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#include <asm/cacheflush.h>
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#include <asm/tlbflush.h>
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#include <linux/errno.h>
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#include <asm/debugreg.h>
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#include <linux/mmiotrace.h>
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#define KMMIO_PAGE_HASH_BITS 4
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#define KMMIO_PAGE_TABLE_SIZE (1 << KMMIO_PAGE_HASH_BITS)
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struct kmmio_fault_page {
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struct list_head list;
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struct kmmio_fault_page *release_next;
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unsigned long addr; /* the requested address */
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pteval_t old_presence; /* page presence prior to arming */
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bool armed;
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/*
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* Number of times this page has been registered as a part
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* of a probe. If zero, page is disarmed and this may be freed.
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* Used only by writers (RCU) and post_kmmio_handler().
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* Protected by kmmio_lock, when linked into kmmio_page_table.
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*/
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int count;
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bool scheduled_for_release;
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};
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struct kmmio_delayed_release {
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struct rcu_head rcu;
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struct kmmio_fault_page *release_list;
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};
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struct kmmio_context {
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struct kmmio_fault_page *fpage;
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struct kmmio_probe *probe;
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unsigned long saved_flags;
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unsigned long addr;
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int active;
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};
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static DEFINE_SPINLOCK(kmmio_lock);
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/* Protected by kmmio_lock */
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unsigned int kmmio_count;
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/* Read-protected by RCU, write-protected by kmmio_lock. */
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static struct list_head kmmio_page_table[KMMIO_PAGE_TABLE_SIZE];
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static LIST_HEAD(kmmio_probes);
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static struct list_head *kmmio_page_list(unsigned long addr)
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{
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unsigned int l;
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pte_t *pte = lookup_address(addr, &l);
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if (!pte)
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return NULL;
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addr &= page_level_mask(l);
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return &kmmio_page_table[hash_long(addr, KMMIO_PAGE_HASH_BITS)];
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}
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/* Accessed per-cpu */
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static DEFINE_PER_CPU(struct kmmio_context, kmmio_ctx);
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/*
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* this is basically a dynamic stabbing problem:
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* Could use the existing prio tree code or
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* Possible better implementations:
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* The Interval Skip List: A Data Structure for Finding All Intervals That
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* Overlap a Point (might be simple)
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* Space Efficient Dynamic Stabbing with Fast Queries - Mikkel Thorup
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*/
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/* Get the kmmio at this addr (if any). You must be holding RCU read lock. */
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static struct kmmio_probe *get_kmmio_probe(unsigned long addr)
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{
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struct kmmio_probe *p;
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list_for_each_entry_rcu(p, &kmmio_probes, list) {
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if (addr >= p->addr && addr < (p->addr + p->len))
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return p;
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}
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return NULL;
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}
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/* You must be holding RCU read lock. */
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static struct kmmio_fault_page *get_kmmio_fault_page(unsigned long addr)
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{
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struct list_head *head;
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struct kmmio_fault_page *f;
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unsigned int l;
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pte_t *pte = lookup_address(addr, &l);
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if (!pte)
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return NULL;
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addr &= page_level_mask(l);
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head = kmmio_page_list(addr);
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list_for_each_entry_rcu(f, head, list) {
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if (f->addr == addr)
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return f;
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}
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return NULL;
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}
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static void clear_pmd_presence(pmd_t *pmd, bool clear, pmdval_t *old)
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{
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pmd_t new_pmd;
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pmdval_t v = pmd_val(*pmd);
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if (clear) {
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*old = v;
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new_pmd = pmd_mkinvalid(*pmd);
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} else {
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/* Presume this has been called with clear==true previously */
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new_pmd = __pmd(*old);
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}
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set_pmd(pmd, new_pmd);
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}
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static void clear_pte_presence(pte_t *pte, bool clear, pteval_t *old)
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{
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pteval_t v = pte_val(*pte);
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if (clear) {
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*old = v;
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/* Nothing should care about address */
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pte_clear(&init_mm, 0, pte);
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} else {
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/* Presume this has been called with clear==true previously */
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set_pte_atomic(pte, __pte(*old));
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}
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}
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static int clear_page_presence(struct kmmio_fault_page *f, bool clear)
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{
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unsigned int level;
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pte_t *pte = lookup_address(f->addr, &level);
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if (!pte) {
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pr_err("no pte for addr 0x%08lx\n", f->addr);
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return -1;
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}
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switch (level) {
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case PG_LEVEL_2M:
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clear_pmd_presence((pmd_t *)pte, clear, &f->old_presence);
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break;
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case PG_LEVEL_4K:
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clear_pte_presence(pte, clear, &f->old_presence);
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break;
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default:
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pr_err("unexpected page level 0x%x.\n", level);
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return -1;
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}
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__flush_tlb_one_kernel(f->addr);
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return 0;
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}
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/*
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* Mark the given page as not present. Access to it will trigger a fault.
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*
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* Struct kmmio_fault_page is protected by RCU and kmmio_lock, but the
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* protection is ignored here. RCU read lock is assumed held, so the struct
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* will not disappear unexpectedly. Furthermore, the caller must guarantee,
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* that double arming the same virtual address (page) cannot occur.
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*
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* Double disarming on the other hand is allowed, and may occur when a fault
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* and mmiotrace shutdown happen simultaneously.
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*/
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static int arm_kmmio_fault_page(struct kmmio_fault_page *f)
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{
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int ret;
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WARN_ONCE(f->armed, KERN_ERR pr_fmt("kmmio page already armed.\n"));
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if (f->armed) {
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pr_warn("double-arm: addr 0x%08lx, ref %d, old %d\n",
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f->addr, f->count, !!f->old_presence);
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}
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ret = clear_page_presence(f, true);
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WARN_ONCE(ret < 0, KERN_ERR pr_fmt("arming at 0x%08lx failed.\n"),
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f->addr);
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f->armed = true;
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return ret;
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}
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/** Restore the given page to saved presence state. */
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static void disarm_kmmio_fault_page(struct kmmio_fault_page *f)
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{
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int ret = clear_page_presence(f, false);
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WARN_ONCE(ret < 0,
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KERN_ERR "kmmio disarming at 0x%08lx failed.\n", f->addr);
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f->armed = false;
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}
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/*
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* This is being called from do_page_fault().
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*
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* We may be in an interrupt or a critical section. Also prefecthing may
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* trigger a page fault. We may be in the middle of process switch.
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* We cannot take any locks, because we could be executing especially
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* within a kmmio critical section.
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*
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* Local interrupts are disabled, so preemption cannot happen.
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* Do not enable interrupts, do not sleep, and watch out for other CPUs.
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*/
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/*
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* Interrupts are disabled on entry as trap3 is an interrupt gate
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* and they remain disabled throughout this function.
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*/
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int kmmio_handler(struct pt_regs *regs, unsigned long addr)
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{
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struct kmmio_context *ctx;
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struct kmmio_fault_page *faultpage;
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int ret = 0; /* default to fault not handled */
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unsigned long page_base = addr;
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unsigned int l;
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pte_t *pte = lookup_address(addr, &l);
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if (!pte)
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return -EINVAL;
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page_base &= page_level_mask(l);
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/*
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* Preemption is now disabled to prevent process switch during
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* single stepping. We can only handle one active kmmio trace
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* per cpu, so ensure that we finish it before something else
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* gets to run. We also hold the RCU read lock over single
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* stepping to avoid looking up the probe and kmmio_fault_page
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* again.
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*/
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preempt_disable();
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rcu_read_lock();
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faultpage = get_kmmio_fault_page(page_base);
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if (!faultpage) {
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/*
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* Either this page fault is not caused by kmmio, or
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* another CPU just pulled the kmmio probe from under
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* our feet. The latter case should not be possible.
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*/
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goto no_kmmio;
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}
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ctx = this_cpu_ptr(&kmmio_ctx);
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if (ctx->active) {
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if (page_base == ctx->addr) {
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/*
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* A second fault on the same page means some other
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* condition needs handling by do_page_fault(), the
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* page really not being present is the most common.
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*/
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pr_debug("secondary hit for 0x%08lx CPU %d.\n",
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addr, smp_processor_id());
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if (!faultpage->old_presence)
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pr_info("unexpected secondary hit for address 0x%08lx on CPU %d.\n",
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addr, smp_processor_id());
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} else {
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/*
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* Prevent overwriting already in-flight context.
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* This should not happen, let's hope disarming at
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* least prevents a panic.
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*/
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pr_emerg("recursive probe hit on CPU %d, for address 0x%08lx. Ignoring.\n",
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smp_processor_id(), addr);
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pr_emerg("previous hit was at 0x%08lx.\n", ctx->addr);
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disarm_kmmio_fault_page(faultpage);
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}
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goto no_kmmio;
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}
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ctx->active++;
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ctx->fpage = faultpage;
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ctx->probe = get_kmmio_probe(page_base);
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ctx->saved_flags = (regs->flags & (X86_EFLAGS_TF | X86_EFLAGS_IF));
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ctx->addr = page_base;
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if (ctx->probe && ctx->probe->pre_handler)
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ctx->probe->pre_handler(ctx->probe, regs, addr);
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/*
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* Enable single-stepping and disable interrupts for the faulting
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* context. Local interrupts must not get enabled during stepping.
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*/
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regs->flags |= X86_EFLAGS_TF;
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regs->flags &= ~X86_EFLAGS_IF;
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/* Now we set present bit in PTE and single step. */
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disarm_kmmio_fault_page(ctx->fpage);
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/*
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* If another cpu accesses the same page while we are stepping,
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* the access will not be caught. It will simply succeed and the
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* only downside is we lose the event. If this becomes a problem,
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* the user should drop to single cpu before tracing.
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*/
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return 1; /* fault handled */
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no_kmmio:
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rcu_read_unlock();
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preempt_enable_no_resched();
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return ret;
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}
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/*
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* Interrupts are disabled on entry as trap1 is an interrupt gate
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* and they remain disabled throughout this function.
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* This must always get called as the pair to kmmio_handler().
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*/
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static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs)
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{
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int ret = 0;
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struct kmmio_context *ctx = this_cpu_ptr(&kmmio_ctx);
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if (!ctx->active) {
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/*
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* debug traps without an active context are due to either
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* something external causing them (f.e. using a debugger while
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* mmio tracing enabled), or erroneous behaviour
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*/
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pr_warn("unexpected debug trap on CPU %d.\n", smp_processor_id());
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goto out;
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}
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if (ctx->probe && ctx->probe->post_handler)
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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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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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regs->flags &= ~X86_EFLAGS_TF;
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regs->flags |= ctx->saved_flags;
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/* These were acquired in kmmio_handler(). */
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ctx->active--;
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BUG_ON(ctx->active);
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rcu_read_unlock();
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preempt_enable_no_resched();
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/*
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* if somebody else is singlestepping across a probe point, flags
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* will have TF set, in which case, continue the remaining processing
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* of do_debug, as if this is not a probe hit.
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*/
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if (!(regs->flags & X86_EFLAGS_TF))
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ret = 1;
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out:
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return ret;
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}
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/* You must be holding kmmio_lock. */
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static int add_kmmio_fault_page(unsigned long addr)
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{
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struct kmmio_fault_page *f;
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f = get_kmmio_fault_page(addr);
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if (f) {
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if (!f->count)
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arm_kmmio_fault_page(f);
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f->count++;
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return 0;
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}
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f = kzalloc(sizeof(*f), GFP_ATOMIC);
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if (!f)
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return -1;
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f->count = 1;
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f->addr = addr;
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if (arm_kmmio_fault_page(f)) {
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kfree(f);
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return -1;
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}
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list_add_rcu(&f->list, kmmio_page_list(f->addr));
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return 0;
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}
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/* You must be holding kmmio_lock. */
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static void release_kmmio_fault_page(unsigned long addr,
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struct kmmio_fault_page **release_list)
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{
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struct kmmio_fault_page *f;
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f = get_kmmio_fault_page(addr);
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if (!f)
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return;
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f->count--;
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BUG_ON(f->count < 0);
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if (!f->count) {
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disarm_kmmio_fault_page(f);
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if (!f->scheduled_for_release) {
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f->release_next = *release_list;
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*release_list = f;
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f->scheduled_for_release = true;
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}
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}
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}
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/*
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* With page-unaligned ioremaps, one or two armed pages may contain
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* addresses from outside the intended mapping. Events for these addresses
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* are currently silently dropped. The events may result only from programming
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* mistakes by accessing addresses before the beginning or past the end of a
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* mapping.
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*/
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int register_kmmio_probe(struct kmmio_probe *p)
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{
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unsigned long flags;
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int ret = 0;
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unsigned long size = 0;
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unsigned long addr = p->addr & PAGE_MASK;
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const unsigned long size_lim = p->len + (p->addr & ~PAGE_MASK);
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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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if (get_kmmio_probe(addr)) {
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ret = -EEXIST;
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goto out;
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}
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pte = lookup_address(addr, &l);
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if (!pte) {
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ret = -EINVAL;
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goto out;
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}
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kmmio_count++;
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list_add_rcu(&p->list, &kmmio_probes);
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while (size < size_lim) {
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if (add_kmmio_fault_page(addr + size))
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pr_err("Unable to set page fault.\n");
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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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/*
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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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* anymore. It seems it's not needed after all.
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*/
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return ret;
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}
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|
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 *f = dr->release_list;
|
|
while (f) {
|
|
struct kmmio_fault_page *next = f->release_next;
|
|
BUG_ON(f->count);
|
|
kfree(f);
|
|
f = 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 *f = dr->release_list;
|
|
struct kmmio_fault_page **prevp = &dr->release_list;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&kmmio_lock, flags);
|
|
while (f) {
|
|
if (!f->count) {
|
|
list_del_rcu(&f->list);
|
|
prevp = &f->release_next;
|
|
} else {
|
|
*prevp = f->release_next;
|
|
f->release_next = NULL;
|
|
f->scheduled_for_release = false;
|
|
}
|
|
f = *prevp;
|
|
}
|
|
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()
|
|
* Actually free the kmmio_fault_page structs as with RCU.
|
|
*/
|
|
void unregister_kmmio_probe(struct kmmio_probe *p)
|
|
{
|
|
unsigned long flags;
|
|
unsigned long size = 0;
|
|
unsigned long addr = p->addr & PAGE_MASK;
|
|
const unsigned long size_lim = p->len + (p->addr & ~PAGE_MASK);
|
|
struct kmmio_fault_page *release_list = NULL;
|
|
struct kmmio_delayed_release *drelease;
|
|
unsigned int l;
|
|
pte_t *pte;
|
|
|
|
pte = lookup_address(addr, &l);
|
|
if (!pte)
|
|
return;
|
|
|
|
spin_lock_irqsave(&kmmio_lock, flags);
|
|
while (size < size_lim) {
|
|
release_kmmio_fault_page(addr + size, &release_list);
|
|
size += page_level_size(l);
|
|
}
|
|
list_del_rcu(&p->list);
|
|
kmmio_count--;
|
|
spin_unlock_irqrestore(&kmmio_lock, flags);
|
|
|
|
if (!release_list)
|
|
return;
|
|
|
|
drelease = kmalloc(sizeof(*drelease), GFP_ATOMIC);
|
|
if (!drelease) {
|
|
pr_crit("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;
|
|
unsigned long* dr6_p = (unsigned long *)ERR_PTR(arg->err);
|
|
|
|
if (val == DIE_DEBUG && (*dr6_p & DR_STEP))
|
|
if (post_kmmio_handler(*dr6_p, arg->regs) == 1) {
|
|
/*
|
|
* Reset the BS bit in dr6 (pointed by args->err) to
|
|
* denote completion of processing
|
|
*/
|
|
*dr6_p &= ~DR_STEP;
|
|
return NOTIFY_STOP;
|
|
}
|
|
|
|
return NOTIFY_DONE;
|
|
}
|
|
|
|
static struct notifier_block nb_die = {
|
|
.notifier_call = kmmio_die_notifier
|
|
};
|
|
|
|
int kmmio_init(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);
|
|
}
|
|
|
|
void kmmio_cleanup(void)
|
|
{
|
|
int i;
|
|
|
|
unregister_die_notifier(&nb_die);
|
|
for (i = 0; i < KMMIO_PAGE_TABLE_SIZE; i++) {
|
|
WARN_ONCE(!list_empty(&kmmio_page_table[i]),
|
|
KERN_ERR "kmmio_page_table not empty at cleanup, any further tracing will leak memory.\n");
|
|
}
|
|
}
|