[PATCH 1/5 V2] Align stack boundaries based on personality

[Eric Munson]

This patch adds a personality flag that requests hugetlb pages be used for
a processes stack.  It adds a helper function that chooses the proper ALIGN
macro based on tthe process personality and calls this function from
setup_arg_pages when aligning the stack address.

Signed-off-by: Andy Whitcroft <apw at shadowen.org>
Signed-off-by: Eric Munson <ebmunson at us.ibm.com>

---
Based on 2.6.26-rc8-mm1

Changes from V1:
Rebase to 2.6.26-rc8-mm1

 fs/exec.c                   |   15 ++++++++++++++-
 include/linux/hugetlb.h     |    3 +++
 include/linux/personality.h |    3 +++
 3 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index af9b29c..c99ba24 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -49,6 +49,7 @@
 #include <linux/tsacct_kern.h>
 #include <linux/cn_proc.h>
 #include <linux/audit.h>
+#include <linux/hugetlb.h>
 
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
@@ -155,6 +156,18 @@ exit:
 	goto out;
 }
 
+static unsigned long personality_page_align(unsigned long addr)
+{
+	if (current->personality & HUGETLB_STACK)
+#ifdef CONFIG_STACK_GROWSUP
+		return HPAGE_ALIGN(addr);
+#else
+		return addr & HPAGE_MASK;
+#endif
+
+	return PAGE_ALIGN(addr);
+}
+
 #ifdef CONFIG_MMU
 
 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
@@ -596,7 +609,7 @@ int setup_arg_pages(struct linux_binprm *bprm,
 	bprm->p = vma->vm_end - stack_shift;
 #else
 	stack_top = arch_align_stack(stack_top);
-	stack_top = PAGE_ALIGN(stack_top);
+	stack_top = personality_page_align(stack_top);
 	stack_shift = vma->vm_end - stack_top;
 
 	bprm->p -= stack_shift;
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 9a71d4c..eed37d7 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -95,6 +95,9 @@ static inline unsigned long hugetlb_total_pages(void)
 #ifndef HPAGE_MASK
 #define HPAGE_MASK	PAGE_MASK		/* Keep the compiler happy */
 #define HPAGE_SIZE	PAGE_SIZE
+
+/* to align the pointer to the (next) huge page boundary */
+#define HPAGE_ALIGN(addr)	ALIGN(addr, HPAGE_SIZE)
 #endif
 
 #endif /* !CONFIG_HUGETLB_PAGE */
diff --git a/include/linux/personality.h b/include/linux/personality.h
index a84e9ff..2bb0f95 100644
--- a/include/linux/personality.h
+++ b/include/linux/personality.h
@@ -22,6 +22,9 @@ extern int		__set_personality(unsigned long);
  * These occupy the top three bytes.
  */
 enum {
+	HUGETLB_STACK =		0x0020000,	/* Attempt to use hugetlb pages
+						 * for the process stack
+						 */
 	ADDR_NO_RANDOMIZE = 	0x0040000,	/* disable randomization of VA space */
 	FDPIC_FUNCPTRS =	0x0080000,	/* userspace function ptrs point to descriptors
 						 * (signal handling)
-- 
1.5.6.1