mm: variable length argument support

Remove the arg+env limit of MAX_ARG_PAGES by copying the strings directly from
the old mm into the new mm.

We create the new mm before the binfmt code runs, and place the new stack at
the very top of the address space.  Once the binfmt code runs and figures out
where the stack should be, we move it downwards.

It is a bit peculiar in that we have one task with two mm's, one of which is
inactive.

[a.p.zijlstra@chello.nl: limit stack size]
Signed-off-by: Ollie Wild <aaw@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <linux-arch@vger.kernel.org>
Cc: Hugh Dickins <hugh@veritas.com>
[bunk@stusta.de: unexport bprm_mm_init]
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 37 insertions, 28 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index 724f342bcf89..7afc7a7cec6f 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1571,33 +1571,11 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
 }
 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
 
-#ifdef CONFIG_STACK_GROWSUP
-int expand_stack(struct vm_area_struct *vma, unsigned long address)
-{
-        return expand_upwards(vma, address);
-}
-
-struct vm_area_struct *
-find_extend_vma(struct mm_struct *mm, unsigned long addr)
-{
-        struct vm_area_struct *vma, *prev;
-
-        addr &= PAGE_MASK;
-        vma = find_vma_prev(mm, addr, &prev);
-        if (vma && (vma->vm_start <= addr))
-                return vma;
-        if (!prev || expand_stack(prev, addr))
-                return NULL;
-        if (prev->vm_flags & VM_LOCKED) {
-                make_pages_present(addr, prev->vm_end);
-        }
-        return prev;
-}
-#else
 /*
  * vma is the first one with address < vma->vm_start.  Have to extend vma.
  */
-int expand_stack(struct vm_area_struct *vma, unsigned long address)
+static inline int expand_downwards(struct vm_area_struct *vma,
+                                   unsigned long address)
 {
         int error;
 
@@ -1634,6 +1612,38 @@ int expand_stack(struct vm_area_struct *vma, unsigned long address)
         return error;
 }
 
+int expand_stack_downwards(struct vm_area_struct *vma, unsigned long address)
+{
+        return expand_downwards(vma, address);
+}
+
+#ifdef CONFIG_STACK_GROWSUP
+int expand_stack(struct vm_area_struct *vma, unsigned long address)
+{
+        return expand_upwards(vma, address);
+}
+
+struct vm_area_struct *
+find_extend_vma(struct mm_struct *mm, unsigned long addr)
+{
+        struct vm_area_struct *vma, *prev;
+
+        addr &= PAGE_MASK;
+        vma = find_vma_prev(mm, addr, &prev);
+        if (vma && (vma->vm_start <= addr))
+                return vma;
+        if (!prev || expand_stack(prev, addr))
+                return NULL;
+        if (prev->vm_flags & VM_LOCKED)
+                make_pages_present(addr, prev->vm_end);
+        return prev;
+}
+#else
+int expand_stack(struct vm_area_struct *vma, unsigned long address)
+{
+        return expand_downwards(vma, address);
+}
+
 struct vm_area_struct *
 find_extend_vma(struct mm_struct * mm, unsigned long addr)
 {
@@ -1651,9 +1661,8 @@ find_extend_vma(struct mm_struct * mm, unsigned long addr)
         start = vma->vm_start;
         if (expand_stack(vma, addr))
                 return NULL;
-        if (vma->vm_flags & VM_LOCKED) {
+        if (vma->vm_flags & VM_LOCKED)
                 make_pages_present(addr, start);
-        }
         return vma;
 }
 #endif
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 3b8f3c0c63f3..e8346c30abec 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -128,7 +128,7 @@ static void change_protection(struct vm_area_struct *vma,
         flush_tlb_range(vma, start, end);
 }
 
-static int
+int
 mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
         unsigned long start, unsigned long end, unsigned long newflags)
 {
diff --git a/mm/mremap.c b/mm/mremap.c
index bc7c52efc71b..8ea5c2412c6e 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -120,7 +120,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 
 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
 
-static unsigned long move_page_tables(struct vm_area_struct *vma,
+unsigned long move_page_tables(struct vm_area_struct *vma,
                 unsigned long old_addr, struct vm_area_struct *new_vma,
                 unsigned long new_addr, unsigned long len)
 {