2 files changed, 112 insertions, 120 deletions

diff --git a/arch/tile/include/asm/stack.h b/arch/tile/include/asm/stack.h
index 4d97a2db932e..0e9d382a2d45 100644
--- a/arch/tile/include/asm/stack.h
+++ b/arch/tile/include/asm/stack.h
@@ -25,7 +25,6 @@
 struct KBacktraceIterator {
         BacktraceIterator it;
         struct task_struct *task;     /* task we are backtracing */
-        pte_t *pgtable;               /* page table for user space access */
         int end;                      /* iteration complete. */
         int new_context;              /* new context is starting */
         int profile;                  /* profiling, so stop on async intrpt */
diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c
index 0be6b0109ce0..b2f44c28dda6 100644
--- a/arch/tile/kernel/stack.c
+++ b/arch/tile/kernel/stack.c
@@ -21,9 +21,10 @@
 #include <linux/stacktrace.h>
 #include <linux/uaccess.h>
 #include <linux/mmzone.h>
+#include <linux/dcache.h>
+#include <linux/fs.h>
 #include <asm/backtrace.h>
 #include <asm/page.h>
-#include <asm/tlbflush.h>
 #include <asm/ucontext.h>
 #include <asm/switch_to.h>
 #include <asm/sigframe.h>
@@ -45,72 +46,23 @@ static int in_kernel_stack(struct KBacktraceIterator *kbt, unsigned long sp)
         return sp >= kstack_base && sp < kstack_base + THREAD_SIZE;
 }
 
-/* Is address valid for reading? */
-static int valid_address(struct KBacktraceIterator *kbt, unsigned long address)
-{
-        HV_PTE *l1_pgtable = kbt->pgtable;
-        HV_PTE *l2_pgtable;
-        unsigned long pfn;
-        HV_PTE pte;
-        struct page *page;
-
-        if (l1_pgtable == NULL)
-                return 0;       /* can't read user space in other tasks */
-
-#ifdef CONFIG_64BIT
-        /* Find the real l1_pgtable by looking in the l0_pgtable. */
-        pte = l1_pgtable[HV_L0_INDEX(address)];
-        if (!hv_pte_get_present(pte))
-                return 0;
-        pfn = hv_pte_get_pfn(pte);
-        if (pte_huge(pte)) {
-                if (!pfn_valid(pfn)) {
-                        pr_err("L0 huge page has bad pfn %#lx\n", pfn);
-                        return 0;
-                }
-                return hv_pte_get_present(pte) && hv_pte_get_readable(pte);
-        }
-        page = pfn_to_page(pfn);
-        BUG_ON(PageHighMem(page));  /* No HIGHMEM on 64-bit. */
-        l1_pgtable = (HV_PTE *)pfn_to_kaddr(pfn);
-#endif
-        pte = l1_pgtable[HV_L1_INDEX(address)];
-        if (!hv_pte_get_present(pte))
-                return 0;
-        pfn = hv_pte_get_pfn(pte);
-        if (pte_huge(pte)) {
-                if (!pfn_valid(pfn)) {
-                        pr_err("huge page has bad pfn %#lx\n", pfn);
-                        return 0;
-                }
-                return hv_pte_get_present(pte) && hv_pte_get_readable(pte);
-        }
-
-        page = pfn_to_page(pfn);
-        if (PageHighMem(page)) {
-                pr_err("L2 page table not in LOWMEM (%#llx)\n",
-                       HV_PFN_TO_CPA(pfn));
-                return 0;
-        }
-        l2_pgtable = (HV_PTE *)pfn_to_kaddr(pfn);
-        pte = l2_pgtable[HV_L2_INDEX(address)];
-        return hv_pte_get_present(pte) && hv_pte_get_readable(pte);
-}
-
 /* Callback for backtracer; basically a glorified memcpy */
 static bool read_memory_func(void *result, unsigned long address,
                              unsigned int size, void *vkbt)
 {
         int retval;
         struct KBacktraceIterator *kbt = (struct KBacktraceIterator *)vkbt;
+
+        if (address == 0)
+                return 0;
         if (__kernel_text_address(address)) {
                 /* OK to read kernel code. */
         } else if (address >= PAGE_OFFSET) {
                 /* We only tolerate kernel-space reads of this task's stack */
                 if (!in_kernel_stack(kbt, address))
                         return 0;
-        } else if (!valid_address(kbt, address)) {
-                return 0;       /* invalid user-space address */
+        } else if (!kbt->is_current) {
+                return 0;       /* can't read from other user address spaces */
         }
         pagefault_disable();
         retval = __copy_from_user_inatomic(result,
@@ -128,6 +80,8 @@ static struct pt_regs *valid_fault_handler(struct KBacktraceIterator* kbt)
         unsigned long sp = kbt->it.sp;
         struct pt_regs *p;
 
+        if (sp % sizeof(long) != 0)
+                return NULL;
         if (!in_kernel_stack(kbt, sp))
                 return NULL;
         if (!in_kernel_stack(kbt, sp + C_ABI_SAVE_AREA_SIZE + PTREGS_SIZE-1))
@@ -170,27 +124,27 @@ static int is_sigreturn(unsigned long pc)
 }
 
 /* Return a pt_regs pointer for a valid signal handler frame */
-static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt)
+static struct pt_regs *valid_sigframe(struct KBacktraceIterator* kbt,
+                                      struct rt_sigframe* kframe)
 {
         BacktraceIterator *b = &kbt->it;
 
-        if (b->pc == VDSO_BASE) {
-                struct rt_sigframe *frame;
-                unsigned long sigframe_top =
-                        b->sp + sizeof(struct rt_sigframe) - 1;
-                if (!valid_address(kbt, b->sp) ||
-                    !valid_address(kbt, sigframe_top)) {
-                        if (kbt->verbose)
-                                pr_err("  (odd signal: sp %#lx?)\n",
-                                       (unsigned long)(b->sp));
+        if (b->pc == VDSO_BASE && b->sp < PAGE_OFFSET &&
+            b->sp % sizeof(long) == 0) {
+                int retval;
+                pagefault_disable();
+                retval = __copy_from_user_inatomic(
+                        kframe, (void __user __force *)b->sp,
+                        sizeof(*kframe));
+                pagefault_enable();
+                if (retval != 0 ||
+                    (unsigned int)(kframe->info.si_signo) >= _NSIG)
                         return NULL;
-                }
-                frame = (struct rt_sigframe *)b->sp;
                 if (kbt->verbose) {
                         pr_err("  <received signal %d>\n",
-                               frame->info.si_signo);
+                               kframe->info.si_signo);
                 }
-                return (struct pt_regs *)&frame->uc.uc_mcontext;
+                return (struct pt_regs *)&kframe->uc.uc_mcontext;
         }
         return NULL;
 }
@@ -203,10 +157,11 @@ static int KBacktraceIterator_is_sigreturn(struct KBacktraceIterator *kbt)
 static int KBacktraceIterator_restart(struct KBacktraceIterator *kbt)
 {
         struct pt_regs *p;
+        struct rt_sigframe kframe;
 
         p = valid_fault_handler(kbt);
         if (p == NULL)
-                p = valid_sigframe(kbt);
+                p = valid_sigframe(kbt, &kframe);
         if (p == NULL)
                 return 0;
         backtrace_init(&kbt->it, read_memory_func, kbt,
@@ -266,41 +221,19 @@ void KBacktraceIterator_init(struct KBacktraceIterator *kbt,
 
         /*
          * Set up callback information.  We grab the kernel stack base
-         * so we will allow reads of that address range, and if we're
-         * asking about the current process we grab the page table
-         * so we can check user accesses before trying to read them.
-         * We flush the TLB to avoid any weird skew issues.
+         * so we will allow reads of that address range.
          */
-        is_current = (t == NULL);
+        is_current = (t == NULL || t == current);
         kbt->is_current = is_current;
         if (is_current)
                 t = validate_current();
         kbt->task = t;
-        kbt->pgtable = NULL;
         kbt->verbose = 0;   /* override in caller if desired */
         kbt->profile = 0;   /* override in caller if desired */
         kbt->end = KBT_ONGOING;
-        kbt->new_context = 0;
-        if (is_current) {
-                HV_PhysAddr pgdir_pa = hv_inquire_context().page_table;
-                if (pgdir_pa == (unsigned long)swapper_pg_dir - PAGE_OFFSET) {
-                        /*
-                         * Not just an optimization: this also allows
-                         * this to work at all before va/pa mappings
-                         * are set up.
-                         */
-                        kbt->pgtable = swapper_pg_dir;
-                } else {
-                        struct page *page = pfn_to_page(PFN_DOWN(pgdir_pa));
-                        if (!PageHighMem(page))
-                                kbt->pgtable = __va(pgdir_pa);
-                        else
-                                pr_err("page table not in LOWMEM"
-                                       " (%#llx)\n", pgdir_pa);
-                }
-                local_flush_tlb_all();
+        kbt->new_context = 1;
+        if (is_current)
                 validate_stack(regs);
-        }
 
         if (regs == NULL) {
                 if (is_current || t->state == TASK_RUNNING) {
@@ -346,6 +279,78 @@ void KBacktraceIterator_next(struct KBacktraceIterator *kbt)
 }
 EXPORT_SYMBOL(KBacktraceIterator_next);
 
+static void describe_addr(struct KBacktraceIterator *kbt,
+                          unsigned long address,
+                          int have_mmap_sem, char *buf, size_t bufsize)
+{
+        struct vm_area_struct *vma;
+        size_t namelen, remaining;
+        unsigned long size, offset, adjust;
+        char *p, *modname;
+        const char *name;
+        int rc;
+
+        /*
+         * Look one byte back for every caller frame (i.e. those that
+         * aren't a new context) so we look up symbol data for the
+         * call itself, not the following instruction, which may be on
+         * a different line (or in a different function).
+         */
+        adjust = !kbt->new_context;
+        address -= adjust;
+
+        if (address >= PAGE_OFFSET) {
+                /* Handle kernel symbols. */
+                BUG_ON(bufsize < KSYM_NAME_LEN);
+                name = kallsyms_lookup(address, &size, &offset,
+                                       &modname, buf);
+                if (name == NULL) {
+                        buf[0] = '\0';
+                        return;
+                }
+                namelen = strlen(buf);
+                remaining = (bufsize - 1) - namelen;
+                p = buf + namelen;
+                rc = snprintf(p, remaining, "+%#lx/%#lx ",
+                              offset + adjust, size);
+                if (modname && rc < remaining)
+                        snprintf(p + rc, remaining - rc, "[%s] ", modname);
+                buf[bufsize-1] = '\0';
+                return;
+        }
+
+        /* If we don't have the mmap_sem, we can't show any more info. */
+        buf[0] = '\0';
+        if (!have_mmap_sem)
+                return;
+
+        /* Find vma info. */
+        vma = find_vma(kbt->task->mm, address);
+        if (vma == NULL || address < vma->vm_start) {
+                snprintf(buf, bufsize, "[unmapped address] ");
+                return;
+        }
+
+        if (vma->vm_file) {
+                char *s;
+                p = d_path(&vma->vm_file->f_path, buf, bufsize);
+                if (IS_ERR(p))
+                        p = "?";
+                s = strrchr(p, '/');
+                if (s)
+                        p = s+1;
+        } else {
+                p = "anon";
+        }
+
+        /* Generate a string description of the vma info. */
+        namelen = strlen(p);
+        remaining = (bufsize - 1) - namelen;
+        memmove(buf, p, namelen);
+        snprintf(buf + namelen, remaining, "[%lx+%lx] ",
+                 vma->vm_start, vma->vm_end - vma->vm_start);
+}
+
 /*
  * This method wraps the backtracer's more generic support.
  * It is only invoked from the architecture-specific code; show_stack()
@@ -354,6 +359,7 @@ EXPORT_SYMBOL(KBacktraceIterator_next);
 void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
 {
         int i;
+        int have_mmap_sem = 0;
 
         if (headers) {
                 /*
@@ -370,31 +376,16 @@ void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
         kbt->verbose = 1;
         i = 0;
         for (; !KBacktraceIterator_end(kbt); KBacktraceIterator_next(kbt)) {
-                char *modname;
-                const char *name;
-                unsigned long address = kbt->it.pc;
-                unsigned long offset, size;
                 char namebuf[KSYM_NAME_LEN+100];
+                unsigned long address = kbt->it.pc;
 
-                if (address >= PAGE_OFFSET)
-                        name = kallsyms_lookup(address, &size, &offset,
-                                               &modname, namebuf);
-                else
-                        name = NULL;
-
-                if (!name)
-                        namebuf[0] = '\0';
-                else {
-                        size_t namelen = strlen(namebuf);
-                        size_t remaining = (sizeof(namebuf) - 1) - namelen;
-                        char *p = namebuf + namelen;
-                        int rc = snprintf(p, remaining, "+%#lx/%#lx ",
-                                          offset, size);
-                        if (modname && rc < remaining)
-                                snprintf(p + rc, remaining - rc,
-                                         "[%s] ", modname);
-                        namebuf[sizeof(namebuf)-1] = '\0';
-                }
+                /* Try to acquire the mmap_sem as we pass into userspace. */
+                if (address < PAGE_OFFSET && !have_mmap_sem && kbt->task->mm)
+                        have_mmap_sem =
+                                down_read_trylock(&kbt->task->mm->mmap_sem);
+
+                describe_addr(kbt, address, have_mmap_sem,
+                              namebuf, sizeof(namebuf));
 
                 pr_err("  frame %d: 0x%lx %s(sp 0x%lx)\n",
                        i++, address, namebuf, (unsigned long)(kbt->it.sp));
@@ -409,6 +400,8 @@ void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
                 pr_err("Stack dump stopped; next frame identical to this one\n");
         if (headers)
                 pr_err("Stack dump complete\n");
+        if (have_mmap_sem)
+                up_read(&kbt->task->mm->mmap_sem);
 }
 EXPORT_SYMBOL(tile_show_stack);