Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=3963333fe6767f15141ab2dc3b933721c636c212
Commit:     3963333fe6767f15141ab2dc3b933721c636c212
Parent:     42a2b54ce8c7b9d4f418995a7950e7e2e15e52ce
Author:     Jeff Dike <[EMAIL PROTECTED]>
AuthorDate: Mon Feb 4 22:31:01 2008 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Tue Feb 5 09:44:29 2008 -0800

    uml: cover stubs with a VMA
    
    Give the stubs a VMA.  This allows the removal of a truly nasty kludge to 
make
    sure that mm->nr_ptes was correct in exit_mmap.  The underlying problem was
    always that the stubs, which have ptes, and thus allocated a page table,
    weren't covered by a VMA.
    
    This patch fixes that by using install_special_mapping in arch_dup_mmap and
    activate_context to create the VMA.  The stubs have to be moved, since
    shift_arg_pages seems to assume that the stack is the only VMA present at 
that
    point during exec, and uses vma_adjust to fiddle its VMA.  However, that
    extends the stub VMA by the amount removed from the stack VMA.
    
    To avoid this problem, the stubs were moved to a different fixed location at
    the start of the address space.
    
    The init_stub_pte calls were moved from init_new_context to arch_dup_mmap
    because I was occasionally seeing arch_dup_mmap not being called, causing
    exit_mmap to die.  Rather than figure out what was really happening, I 
decided
    it was cleaner to just move the calls so that there's no doubt that both the
    pte and VMA creation happen, no matter what.  arch_exit_mmap is used to 
clear
    the stub ptes at exit time.
    
    The STUB_* constants in as-layout.h no longer depend on UM_TASK_SIZE, that
    that definition is removed, along with the comments complaining about gcc.
    
    Because the stubs are no longer at the top of the address space, some care 
is
    needed while flushing TLBs.  update_pte_range checks for addresses in the 
stub
    range and skips them.  flush_thread now issues two unmaps, one for the range
    before STUB_START and one for the range after STUB_END.
    
    Signed-off-by: Jeff Dike <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 arch/um/include/as-layout.h      |   19 ++------
 arch/um/include/common-offsets.h |    3 -
 arch/um/kernel/exec.c            |    5 +-
 arch/um/kernel/skas/mmu.c        |  104 +++++++++++++++++++++----------------
 arch/um/kernel/tlb.c             |   11 ++---
 include/asm-um/mmu_context.h     |    7 ++-
 6 files changed, 75 insertions(+), 74 deletions(-)

diff --git a/arch/um/include/as-layout.h b/arch/um/include/as-layout.h
index a2008f5..606bb5c 100644
--- a/arch/um/include/as-layout.h
+++ b/arch/um/include/as-layout.h
@@ -29,21 +29,10 @@
 #define _AC(X, Y)      __AC(X, Y)
 #endif
 
-/*
- * The "- 1"'s are to avoid gcc complaining about integer overflows
- * and unrepresentable decimal constants.  With 3-level page tables,
- * TASK_SIZE is 0x80000000, which gets turned into its signed decimal
- * equivalent in asm-offsets.s.  gcc then complains about that being
- * unsigned only in C90.  To avoid that, UM_TASK_SIZE is defined as
- * TASK_SIZE - 1.  To compensate, we need to add the 1 back here.
- * However, adding it back to UM_TASK_SIZE produces more gcc
- * complaints.  So, I adjust the thing being subtracted from
- * UM_TASK_SIZE instead.  Bah.
- */
-#define STUB_CODE _AC((unsigned long), \
-                     UM_TASK_SIZE - (2 * UM_KERN_PAGE_SIZE - 1))
-#define STUB_DATA _AC((unsigned long), UM_TASK_SIZE - (UM_KERN_PAGE_SIZE - 1))
-#define STUB_START _AC(, STUB_CODE)
+#define STUB_START _AC(, 0x100000)
+#define STUB_CODE _AC((unsigned long), STUB_START)
+#define STUB_DATA _AC((unsigned long), STUB_CODE + UM_KERN_PAGE_SIZE)
+#define STUB_END _AC((unsigned long), STUB_DATA + UM_KERN_PAGE_SIZE)
 
 #ifndef __ASSEMBLY__
 
diff --git a/arch/um/include/common-offsets.h b/arch/um/include/common-offsets.h
index 5b67d7c..b54bd35 100644
--- a/arch/um/include/common-offsets.h
+++ b/arch/um/include/common-offsets.h
@@ -39,6 +39,3 @@ DEFINE(UM_HZ, HZ);
 DEFINE(UM_USEC_PER_SEC, USEC_PER_SEC);
 DEFINE(UM_NSEC_PER_SEC, NSEC_PER_SEC);
 DEFINE(UM_NSEC_PER_USEC, NSEC_PER_USEC);
-
-/* See as-layout.h for an explanation of the "- 1".  Bah. */
-DEFINE(UM_TASK_SIZE, TASK_SIZE - 1);
diff --git a/arch/um/kernel/exec.c b/arch/um/kernel/exec.c
index bf66b5b..76a62c0 100644
--- a/arch/um/kernel/exec.c
+++ b/arch/um/kernel/exec.c
@@ -19,12 +19,13 @@
 void flush_thread(void)
 {
        void *data = NULL;
-       unsigned long end = proc_mm ? TASK_SIZE : STUB_START;
        int ret;
 
        arch_flush_thread(&current->thread.arch);
 
-       ret = unmap(&current->mm->context.id, 0, end, 1, &data);
+       ret = unmap(&current->mm->context.id, 0, STUB_START, 0, &data);
+       ret = ret || unmap(&current->mm->context.id, STUB_END,
+                          TASK_SIZE - STUB_END, 1, &data);
        if (ret) {
                printk(KERN_ERR "flush_thread - clearing address space failed, "
                       "err = %d\n", ret);
diff --git a/arch/um/kernel/skas/mmu.c b/arch/um/kernel/skas/mmu.c
index 6da9ab4..e8dc854 100644
--- a/arch/um/kernel/skas/mmu.c
+++ b/arch/um/kernel/skas/mmu.c
@@ -34,25 +34,6 @@ static int init_stub_pte(struct mm_struct *mm, unsigned long 
proc,
        if (!pte)
                goto out_pte;
 
-       /*
-        * There's an interaction between the skas0 stub pages, stack
-        * randomization, and the BUG at the end of exit_mmap.  exit_mmap
-        * checks that the number of page tables freed is the same as had
-        * been allocated.  If the stack is on the last page table page,
-        * then the stack pte page will be freed, and if not, it won't.  To
-        * avoid having to know where the stack is, or if the process mapped
-        * something at the top of its address space for some other reason,
-        * we set TASK_SIZE to end at the start of the last page table.
-        * This keeps exit_mmap off the last page, but introduces a leak
-        * of that page.  So, we hang onto it here and free it in
-        * destroy_context_skas.
-        */
-
-       mm->context.last_page_table = pmd_page_vaddr(*pmd);
-#ifdef CONFIG_3_LEVEL_PGTABLES
-       mm->context.last_pmd = (unsigned long) __va(pud_val(*pud));
-#endif
-
        *pte = mk_pte(virt_to_page(kernel), __pgprot(_PAGE_PRESENT));
        *pte = pte_mkread(*pte);
        return 0;
@@ -76,24 +57,6 @@ int init_new_context(struct task_struct *task, struct 
mm_struct *mm)
                stack = get_zeroed_page(GFP_KERNEL);
                if (stack == 0)
                        goto out;
-
-               /*
-                * This zeros the entry that pgd_alloc didn't, needed since
-                * we are about to reinitialize it, and want mm.nr_ptes to
-                * be accurate.
-                */
-               mm->pgd[USER_PTRS_PER_PGD] = __pgd(0);
-
-               ret = init_stub_pte(mm, STUB_CODE,
-                                   (unsigned long) &__syscall_stub_start);
-               if (ret)
-                       goto out_free;
-
-               ret = init_stub_pte(mm, STUB_DATA, stack);
-               if (ret)
-                       goto out_free;
-
-               mm->nr_ptes--;
        }
 
        to_mm->id.stack = stack;
@@ -137,6 +100,64 @@ int init_new_context(struct task_struct *task, struct 
mm_struct *mm)
        return ret;
 }
 
+void arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
+{
+       struct page **pages;
+       int err, ret;
+
+       if (!skas_needs_stub)
+               return;
+
+       ret = init_stub_pte(mm, STUB_CODE,
+                           (unsigned long) &__syscall_stub_start);
+       if (ret)
+               goto out;
+
+       ret = init_stub_pte(mm, STUB_DATA, mm->context.id.stack);
+       if (ret)
+               goto out;
+
+       pages = kmalloc(2 * sizeof(struct page *), GFP_KERNEL);
+       if (pages == NULL) {
+               printk(KERN_ERR "arch_dup_mmap failed to allocate 2 page "
+                      "pointers\n");
+               goto out;
+       }
+
+       pages[0] = virt_to_page(&__syscall_stub_start);
+       pages[1] = virt_to_page(mm->context.id.stack);
+
+       /* dup_mmap already holds mmap_sem */
+       err = install_special_mapping(mm, STUB_START, STUB_END - STUB_START,
+                                     VM_READ | VM_MAYREAD | VM_EXEC |
+                                     VM_MAYEXEC | VM_DONTCOPY, pages);
+       if (err) {
+               printk(KERN_ERR "install_special_mapping returned %d\n", err);
+               goto out_free;
+       }
+       return;
+
+out_free:
+       kfree(pages);
+out:
+       force_sigsegv(SIGSEGV, current);
+}
+
+void arch_exit_mmap(struct mm_struct *mm)
+{
+       pte_t *pte;
+
+       pte = virt_to_pte(mm, STUB_CODE);
+       if (pte != NULL)
+               pte_clear(mm, STUB_CODE, pte);
+
+       pte = virt_to_pte(mm, STUB_DATA);
+       if (pte == NULL)
+               return;
+
+       pte_clear(mm, STUB_DATA, pte);
+}
+
 void destroy_context(struct mm_struct *mm)
 {
        struct mm_context *mmu = &mm->context;
@@ -146,15 +167,8 @@ void destroy_context(struct mm_struct *mm)
        else
                os_kill_ptraced_process(mmu->id.u.pid, 1);
 
-       if (!proc_mm || !ptrace_faultinfo) {
+       if (skas_needs_stub)
                free_page(mmu->id.stack);
-               pte_lock_deinit(virt_to_page(mmu->last_page_table));
-               pte_free_kernel(mm, (pte_t *) mmu->last_page_table);
-               dec_zone_page_state(virt_to_page(mmu->last_page_table), 
NR_PAGETABLE);
-#ifdef CONFIG_3_LEVEL_PGTABLES
-               pmd_free(mm, (pmd_t *) mmu->last_pmd);
-#endif
-       }
 
        free_ldt(mmu);
 }
diff --git a/arch/um/kernel/tlb.c b/arch/um/kernel/tlb.c
index 429fed2..ef5a2a2 100644
--- a/arch/um/kernel/tlb.c
+++ b/arch/um/kernel/tlb.c
@@ -184,6 +184,9 @@ static inline int update_pte_range(pmd_t *pmd, unsigned 
long addr,
 
        pte = pte_offset_kernel(pmd, addr);
        do {
+               if ((addr >= STUB_START) && (addr < STUB_END))
+                       continue;
+
                r = pte_read(*pte);
                w = pte_write(*pte);
                x = pte_exec(*pte);
@@ -486,9 +489,6 @@ void __flush_tlb_one(unsigned long addr)
 static void fix_range(struct mm_struct *mm, unsigned long start_addr,
                      unsigned long end_addr, int force)
 {
-       if (!proc_mm && (end_addr > STUB_START))
-               end_addr = STUB_START;
-
        fix_range_common(mm, start_addr, end_addr, force);
 }
 
@@ -502,8 +502,6 @@ void flush_tlb_range(struct vm_area_struct *vma, unsigned 
long start,
 
 void flush_tlb_mm(struct mm_struct *mm)
 {
-       unsigned long end;
-
        /*
         * Don't bother flushing if this address space is about to be
         * destroyed.
@@ -511,8 +509,7 @@ void flush_tlb_mm(struct mm_struct *mm)
        if (atomic_read(&mm->mm_users) == 0)
                return;
 
-       end = proc_mm ? TASK_SIZE : STUB_START;
-       fix_range(mm, 0, end, 0);
+       fix_range(mm, 0, TASK_SIZE, 0);
 }
 
 void force_flush_all(void)
diff --git a/include/asm-um/mmu_context.h b/include/asm-um/mmu_context.h
index 5f3b863..6686fc5 100644
--- a/include/asm-um/mmu_context.h
+++ b/include/asm-um/mmu_context.h
@@ -6,11 +6,12 @@
 #ifndef __UM_MMU_CONTEXT_H
 #define __UM_MMU_CONTEXT_H
 
-#include <asm-generic/mm_hooks.h>
-
 #include "linux/sched.h"
 #include "um_mmu.h"
 
+extern void arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm);
+extern void arch_exit_mmap(struct mm_struct *mm);
+
 #define get_mmu_context(task) do ; while(0)
 #define activate_context(tsk) do ; while(0)
 
@@ -30,6 +31,8 @@ static inline void activate_mm(struct mm_struct *old, struct 
mm_struct *new)
         */
        if (old != new && (current->flags & PF_BORROWED_MM))
                __switch_mm(&new->context.id);
+
+       arch_dup_mmap(old, new);
 }
 
 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, 
-
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