lkml.org 
[lkml]   [2011]   [May]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[15/71] Dont lock guardpage if the stack is growing up
2.6.38-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>

commit a09a79f66874c905af35d5bb5e5f2fdc7b6b894d upstream.

Linux kernel excludes guard page when performing mlock on a VMA with
down-growing stack. However, some architectures have up-growing stack
and locking the guard page should be excluded in this case too.

This patch fixes lvm2 on PA-RISC (and possibly other architectures with
up-growing stack). lvm2 calculates number of used pages when locking and
when unlocking and reports an internal error if the numbers mismatch.

[ Patch changed fairly extensively to also fix /proc/<pid>/maps for the
grows-up case, and to move things around a bit to clean it all up and
share the infrstructure with the /proc bits.

Tested on ia64 that has both grow-up and grow-down segments - Linus ]

Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Tested-by: Tony Luck <tony.luck@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/proc/task_mmu.c | 12 +++++++-----
include/linux/mm.h | 24 +++++++++++++++++++++++-
mm/memory.c | 16 +++++++---------
3 files changed, 37 insertions(+), 15 deletions(-)

--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -211,7 +211,7 @@ static void show_map_vma(struct seq_file
int flags = vma->vm_flags;
unsigned long ino = 0;
unsigned long long pgoff = 0;
- unsigned long start;
+ unsigned long start, end;
dev_t dev = 0;
int len;

@@ -224,13 +224,15 @@ static void show_map_vma(struct seq_file

/* We don't show the stack guard page in /proc/maps */
start = vma->vm_start;
- if (vma->vm_flags & VM_GROWSDOWN)
- if (!vma_stack_continue(vma->vm_prev, vma->vm_start))
- start += PAGE_SIZE;
+ if (stack_guard_page_start(vma, start))
+ start += PAGE_SIZE;
+ end = vma->vm_end;
+ if (stack_guard_page_end(vma, end))
+ end -= PAGE_SIZE;

seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
start,
- vma->vm_end,
+ end,
flags & VM_READ ? 'r' : '-',
flags & VM_WRITE ? 'w' : '-',
flags & VM_EXEC ? 'x' : '-',
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -994,11 +994,33 @@ int set_page_dirty_lock(struct page *pag
int clear_page_dirty_for_io(struct page *page);

/* Is the vma a continuation of the stack vma above it? */
-static inline int vma_stack_continue(struct vm_area_struct *vma, unsigned long addr)
+static inline int vma_growsdown(struct vm_area_struct *vma, unsigned long addr)
{
return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);
}

+static inline int stack_guard_page_start(struct vm_area_struct *vma,
+ unsigned long addr)
+{
+ return (vma->vm_flags & VM_GROWSDOWN) &&
+ (vma->vm_start == addr) &&
+ !vma_growsdown(vma->vm_prev, addr);
+}
+
+/* Is the vma a continuation of the stack vma below it? */
+static inline int vma_growsup(struct vm_area_struct *vma, unsigned long addr)
+{
+ return vma && (vma->vm_start == addr) && (vma->vm_flags & VM_GROWSUP);
+}
+
+static inline int stack_guard_page_end(struct vm_area_struct *vma,
+ unsigned long addr)
+{
+ return (vma->vm_flags & VM_GROWSUP) &&
+ (vma->vm_end == addr) &&
+ !vma_growsup(vma->vm_next, addr);
+}
+
extern 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);
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1412,9 +1412,8 @@ no_page_table:

static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
{
- return (vma->vm_flags & VM_GROWSDOWN) &&
- (vma->vm_start == addr) &&
- !vma_stack_continue(vma->vm_prev, addr);
+ return stack_guard_page_start(vma, addr) ||
+ stack_guard_page_end(vma, addr+PAGE_SIZE);
}

int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
@@ -1502,12 +1501,6 @@ int __get_user_pages(struct task_struct
continue;
}

- /*
- * For mlock, just skip the stack guard page.
- */
- if ((gup_flags & FOLL_MLOCK) && stack_guard_page(vma, start))
- goto next_page;
-
do {
struct page *page;
unsigned int foll_flags = gup_flags;
@@ -1524,6 +1517,11 @@ int __get_user_pages(struct task_struct
int ret;
unsigned int fault_flags = 0;

+ /* For mlock, just skip the stack guard page. */
+ if (foll_flags & FOLL_MLOCK) {
+ if (stack_guard_page(vma, start))
+ goto next_page;
+ }
if (foll_flags & FOLL_WRITE)
fault_flags |= FAULT_FLAG_WRITE;
if (nonblocking)



\
 
 \ /
  Last update: 2011-05-19 20:25    [W:0.194 / U:40.944 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site