proc: use vma flags for determing vmas with MAP_GROWSDOWN

When a kernel didn't show vma flags, we set MAP_GROWSDOWN for stack
vmas, but it's not reliable. E.g. thread stacks are mapped without
MAP_GROWSDOWN.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-dump.c

@@ -695,8 +695,6 @@ static int dump_task_core_all(struct parasite_ctl *ctl,
 	if (ret)
 		goto err_free;
 
-	mark_stack_vma(CORE_THREAD_ARCH_INFO(core)->gpregs->sp, &vma_area_list->h);
-
 	ret = get_task_futex_robust_list(pid, core->thread_core);
 	if (ret)
 		goto err_free;

cr-restore.c

@@ -1802,9 +1802,6 @@ static int sigreturn_restore(pid_t pid, CoreEntry *core)
 	if (ret < 0)
 		goto err;
 
-	/* required to unmap stack _with_ guard page */
-	mark_stack_vma((long) &self_vmas, &self_vmas.h);
-
 	self_vmas_len = round_up((self_vmas.nr + 1) * sizeof(VmaEntry), PAGE_SIZE);
 	vmas_len = round_up((rst_vmas.nr + 1) * sizeof(VmaEntry), PAGE_SIZE);
 

include/util.h

@@ -133,8 +133,6 @@ extern void pr_vma(unsigned int loglevel, const struct vma_area *vma_area);
 		p__;						\
 	})
 
-extern void mark_stack_vma(unsigned long sp, struct list_head *vma_area_list);
-
 extern int move_img_fd(int *img_fd, int want_fd);
 extern int close_safe(int *fd);
 

proc_parse.c

@@ -96,9 +96,10 @@ static int parse_vmflags(char *buf, struct vma_area *vma_area)
 
 	do {
 		/* mmap() block */
-		if (_vmflag_match(tok, "gd"))
+		if (_vmflag_match(tok, "gd")) {
 			vma_area->vma.flags |= MAP_GROWSDOWN;
-		else if (_vmflag_match(tok, "lo"))
+			vma_area->vma.start -= PAGE_SIZE; /* Guard page */
+		} else if (_vmflag_match(tok, "lo"))
 			vma_area->vma.flags |= MAP_LOCKED;
 		else if (_vmflag_match(tok, "nr"))
 			vma_area->vma.flags |= MAP_NORESERVE;

util.c

@@ -36,26 +36,6 @@
 
 #include "crtools.h"
 
-/* /proc/PID/maps can contain not up to date information about stack */
-void mark_stack_vma(unsigned long sp, struct list_head *vma_area_list)
-{
-	struct vma_area *vma_area;
-	list_for_each_entry(vma_area, vma_area_list, list) {
-		if (in_vma_area(vma_area, sp)) {
-			vma_area->vma.status |= VMA_AREA_STACK;
-			vma_area->vma.flags  |= MAP_GROWSDOWN;
-
-			/*
-			 * The kernel doesn't show stack guard pages on
-			 * proc output, so add pages here by hands.
-			 */
-			vma_area->vma.start -= PAGE_SIZE;
-			return;
-		}
-	}
-	BUG();
-}
-
 #define VMA_OPT_LEN	128
 
 static void vma_opt_str(const struct vma_area *v, char *opt)