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>

1 files changed, 35 insertions, 26 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