diff options
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/mm/kmmio.c | 66 |
1 files changed, 44 insertions, 22 deletions
diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c index fb1f11546fcd..be361eb828c8 100644 --- a/arch/x86/mm/kmmio.c +++ b/arch/x86/mm/kmmio.c @@ -32,6 +32,8 @@ struct kmmio_fault_page { struct list_head list; struct kmmio_fault_page *release_next; unsigned long page; /* location of the fault page */ + bool old_presence; /* page presence prior to arming */ + bool armed; /* * Number of times this page has been registered as a part @@ -105,8 +107,7 @@ static struct kmmio_fault_page *get_kmmio_fault_page(unsigned long page) return NULL; } -static int set_page_present(unsigned long addr, bool present, - unsigned int *pglevel) +static int set_page_presence(unsigned long addr, bool present, bool *old) { pteval_t pteval; pmdval_t pmdval; @@ -119,20 +120,21 @@ static int set_page_present(unsigned long addr, bool present, return -1; } - if (pglevel) - *pglevel = level; - switch (level) { case PG_LEVEL_2M: pmd = (pmd_t *)pte; - pmdval = pmd_val(*pmd) & ~_PAGE_PRESENT; + pmdval = pmd_val(*pmd); + *old = !!(pmdval & _PAGE_PRESENT); + pmdval &= ~_PAGE_PRESENT; if (present) pmdval |= _PAGE_PRESENT; set_pmd(pmd, __pmd(pmdval)); break; case PG_LEVEL_4K: - pteval = pte_val(*pte) & ~_PAGE_PRESENT; + pteval = pte_val(*pte); + *old = !!(pteval & _PAGE_PRESENT); + pteval &= ~_PAGE_PRESENT; if (present) pteval |= _PAGE_PRESENT; set_pte_atomic(pte, __pte(pteval)); @@ -148,19 +150,39 @@ static int set_page_present(unsigned long addr, bool present, return 0; } -/** Mark the given page as not present. Access to it will trigger a fault. */ -static int arm_kmmio_fault_page(unsigned long page, unsigned int *pglevel) +/* + * Mark the given page as not present. Access to it will trigger a fault. + * + * Struct kmmio_fault_page is protected by RCU and kmmio_lock, but the + * protection is ignored here. RCU read lock is assumed held, so the struct + * will not disappear unexpectedly. Furthermore, the caller must guarantee, + * that double arming the same virtual address (page) cannot occur. + * + * Double disarming on the other hand is allowed, and may occur when a fault + * and mmiotrace shutdown happen simultaneously. + */ +static int arm_kmmio_fault_page(struct kmmio_fault_page *f) { - int ret = set_page_present(page & PAGE_MASK, false, pglevel); - WARN_ONCE(ret < 0, KERN_ERR "kmmio arming 0x%08lx failed.\n", page); + int ret; + WARN_ONCE(f->armed, KERN_ERR "kmmio page already armed.\n"); + if (f->armed) { + pr_warning("kmmio double-arm: page 0x%08lx, ref %d, old %d\n", + f->page, f->count, f->old_presence); + } + ret = set_page_presence(f->page, false, &f->old_presence); + WARN_ONCE(ret < 0, KERN_ERR "kmmio arming 0x%08lx failed.\n", f->page); + f->armed = true; return ret; } -/** Mark the given page as present. */ -static void disarm_kmmio_fault_page(unsigned long page, unsigned int *pglevel) +/** Restore the given page to saved presence state. */ +static void disarm_kmmio_fault_page(struct kmmio_fault_page *f) { - int ret = set_page_present(page & PAGE_MASK, true, pglevel); - WARN_ONCE(ret < 0, KERN_ERR "kmmio disarming 0x%08lx failed.\n", page); + bool tmp; + int ret = set_page_presence(f->page, f->old_presence, &tmp); + WARN_ONCE(ret < 0, + KERN_ERR "kmmio disarming 0x%08lx failed.\n", f->page); + f->armed = false; } /* @@ -207,7 +229,7 @@ int kmmio_handler(struct pt_regs *regs, unsigned long addr) ctx = &get_cpu_var(kmmio_ctx); if (ctx->active) { - disarm_kmmio_fault_page(faultpage->page, NULL); + disarm_kmmio_fault_page(faultpage); if (addr == ctx->addr) { /* * On SMP we sometimes get recursive probe hits on the @@ -249,7 +271,7 @@ int kmmio_handler(struct pt_regs *regs, unsigned long addr) regs->flags &= ~X86_EFLAGS_IF; /* Now we set present bit in PTE and single step. */ - disarm_kmmio_fault_page(ctx->fpage->page, NULL); + disarm_kmmio_fault_page(ctx->fpage); /* * If another cpu accesses the same page while we are stepping, @@ -288,7 +310,7 @@ static int post_kmmio_handler(unsigned long condition, struct pt_regs *regs) if (ctx->probe && ctx->probe->post_handler) ctx->probe->post_handler(ctx->probe, condition, regs); - arm_kmmio_fault_page(ctx->fpage->page, NULL); + arm_kmmio_fault_page(ctx->fpage); regs->flags &= ~X86_EFLAGS_TF; regs->flags |= ctx->saved_flags; @@ -320,19 +342,19 @@ static int add_kmmio_fault_page(unsigned long page) f = get_kmmio_fault_page(page); if (f) { if (!f->count) - arm_kmmio_fault_page(f->page, NULL); + arm_kmmio_fault_page(f); f->count++; return 0; } - f = kmalloc(sizeof(*f), GFP_ATOMIC); + f = kzalloc(sizeof(*f), GFP_ATOMIC); if (!f) return -1; f->count = 1; f->page = page; - if (arm_kmmio_fault_page(f->page, NULL)) { + if (arm_kmmio_fault_page(f)) { kfree(f); return -1; } @@ -356,7 +378,7 @@ static void release_kmmio_fault_page(unsigned long page, f->count--; BUG_ON(f->count < 0); if (!f->count) { - disarm_kmmio_fault_page(f->page, NULL); + disarm_kmmio_fault_page(f); f->release_next = *release_list; *release_list = f; } |