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Subject[PATCH 1/5 V2] Align stack boundaries based on personality
Date
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@shadowen.org>
Signed-off-by: Eric Munson <ebmunson@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


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