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, 17 insertions, 110 deletions

diff --git a/arch/ia64/ia32/binfmt_elf32.c b/arch/ia64/ia32/binfmt_elf32.c
index 6f4d3d06f0ed..e1189ba1ca5e 100644
--- a/arch/ia64/ia32/binfmt_elf32.c
+++ b/arch/ia64/ia32/binfmt_elf32.c
@@ -195,62 +195,27 @@ ia64_elf32_init (struct pt_regs *regs)
         ia32_load_state(current);
 }
 
+/*
+ * Undo the override of setup_arg_pages() without this ia32_setup_arg_pages()
+ * will suffer infinite self recursion.
+ */
+#undef setup_arg_pages
+
 int
 ia32_setup_arg_pages (struct linux_binprm *bprm, int executable_stack)
 {
-        unsigned long stack_base;
-        struct vm_area_struct *mpnt;
-        struct mm_struct *mm = current->mm;
-        int i, ret;
-
-        stack_base = IA32_STACK_TOP - MAX_ARG_PAGES*PAGE_SIZE;
-        mm->arg_start = bprm->p + stack_base;
-
-        bprm->p += stack_base;
-        if (bprm->loader)
-                bprm->loader += stack_base;
-        bprm->exec += stack_base;
-
-        mpnt = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
-        if (!mpnt)
-                return -ENOMEM;
-
-        down_write(&current->mm->mmap_sem);
-        {
-                mpnt->vm_mm = current->mm;
-                mpnt->vm_start = PAGE_MASK & (unsigned long) bprm->p;
-                mpnt->vm_end = IA32_STACK_TOP;
-                if (executable_stack == EXSTACK_ENABLE_X)
-                        mpnt->vm_flags = VM_STACK_FLAGS |  VM_EXEC;
-                else if (executable_stack == EXSTACK_DISABLE_X)
-                        mpnt->vm_flags = VM_STACK_FLAGS & ~VM_EXEC;
-                else
-                        mpnt->vm_flags = VM_STACK_FLAGS;
-                mpnt->vm_page_prot = (mpnt->vm_flags & VM_EXEC)?
-                                        PAGE_COPY_EXEC: PAGE_COPY;
-                if ((ret = insert_vm_struct(current->mm, mpnt))) {
-                        up_write(&current->mm->mmap_sem);
-                        kmem_cache_free(vm_area_cachep, mpnt);
-                        return ret;
-                }
-                current->mm->stack_vm = current->mm->total_vm = vma_pages(mpnt);
+        int ret;
+
+        ret = setup_arg_pages(bprm, IA32_STACK_TOP, executable_stack);
+        if (!ret) {
+                /*
+                 * Can't do it in ia64_elf32_init(). Needs to be done before
+                 * calls to elf32_map()
+                 */
+                current->thread.ppl = ia32_init_pp_list();
         }
 
-        for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
-                struct page *page = bprm->page[i];
-                if (page) {
-                        bprm->page[i] = NULL;
-                        install_arg_page(mpnt, page, stack_base);
-                }
-                stack_base += PAGE_SIZE;
-        }
-        up_write(&current->mm->mmap_sem);
-
-        /* Can't do it in ia64_elf32_init(). Needs to be done before calls to
-           elf32_map() */
-        current->thread.ppl = ia32_init_pp_list();
-
-        return 0;
+        return ret;
 }
 
 static void
diff --git a/arch/x86_64/ia32/ia32_aout.c b/arch/x86_64/ia32/ia32_aout.c
index fe83edb93c10..08781370256d 100644
--- a/arch/x86_64/ia32/ia32_aout.c
+++ b/arch/x86_64/ia32/ia32_aout.c
@@ -404,7 +404,7 @@ beyond_if:
 
         set_brk(current->mm->start_brk, current->mm->brk);
 
-        retval = ia32_setup_arg_pages(bprm, IA32_STACK_TOP, EXSTACK_DEFAULT);
+        retval = setup_arg_pages(bprm, IA32_STACK_TOP, EXSTACK_DEFAULT);
         if (retval < 0) { 
                 /* Someone check-me: is this error path enough? */ 
                 send_sig(SIGKILL, current, 0); 
diff --git a/arch/x86_64/ia32/ia32_binfmt.c b/arch/x86_64/ia32/ia32_binfmt.c
index 185399baaf6d..ed56a8806eab 100644
--- a/arch/x86_64/ia32/ia32_binfmt.c
+++ b/arch/x86_64/ia32/ia32_binfmt.c
@@ -232,9 +232,6 @@ do {							\
 #define load_elf_binary load_elf32_binary
 
 #define ELF_PLAT_INIT(r, load_addr)     elf32_init(r)
-#define setup_arg_pages(bprm, stack_top, exec_stack) \
-        ia32_setup_arg_pages(bprm, stack_top, exec_stack)
-int ia32_setup_arg_pages(struct linux_binprm *bprm, unsigned long stack_top, int executable_stack);
 
 #undef start_thread
 #define start_thread(regs,new_rip,new_rsp) do { \
@@ -286,61 +283,6 @@ static void elf32_init(struct pt_regs *regs)
         me->thread.es = __USER_DS;
 }
 
-int ia32_setup_arg_pages(struct linux_binprm *bprm, unsigned long stack_top,
-                         int executable_stack)
-{
-        unsigned long stack_base;
-        struct vm_area_struct *mpnt;
-        struct mm_struct *mm = current->mm;
-        int i, ret;
-
-        stack_base = stack_top - MAX_ARG_PAGES * PAGE_SIZE;
-        mm->arg_start = bprm->p + stack_base;
-
-        bprm->p += stack_base;
-        if (bprm->loader)
-                bprm->loader += stack_base;
-        bprm->exec += stack_base;
-
-        mpnt = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
-        if (!mpnt) 
-                return -ENOMEM; 
-
-        down_write(&mm->mmap_sem);
-        {
-                mpnt->vm_mm = mm;
-                mpnt->vm_start = PAGE_MASK & (unsigned long) bprm->p;
-                mpnt->vm_end = stack_top;
-                if (executable_stack == EXSTACK_ENABLE_X)
-                        mpnt->vm_flags = VM_STACK_FLAGS |  VM_EXEC;
-                else if (executable_stack == EXSTACK_DISABLE_X)
-                        mpnt->vm_flags = VM_STACK_FLAGS & ~VM_EXEC;
-                else
-                        mpnt->vm_flags = VM_STACK_FLAGS;
-                mpnt->vm_page_prot = (mpnt->vm_flags & VM_EXEC) ? 
-                        PAGE_COPY_EXEC : PAGE_COPY;
-                if ((ret = insert_vm_struct(mm, mpnt))) {
-                        up_write(&mm->mmap_sem);
-                        kmem_cache_free(vm_area_cachep, mpnt);
-                        return ret;
-                }
-                mm->stack_vm = mm->total_vm = vma_pages(mpnt);
-        } 
-
-        for (i = 0 ; i < MAX_ARG_PAGES ; i++) {
-                struct page *page = bprm->page[i];
-                if (page) {
-                        bprm->page[i] = NULL;
-                        install_arg_page(mpnt, page, stack_base);
-                }
-                stack_base += PAGE_SIZE;
-        }
-        up_write(&mm->mmap_sem);
-        
-        return 0;
-}
-EXPORT_SYMBOL(ia32_setup_arg_pages);
-
 #ifdef CONFIG_SYSCTL
 /* Register vsyscall32 into the ABI table */
 #include <linux/sysctl.h>