[PATCH] mm: add VM_STATIC flag to vmalloc and prevent from removing the areas

Hoeun Ryu
2017-04-12T05:03:13Z

vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area
during boot process and those virtually mapped areas are never unmapped.
So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing
existing vmlist entries and prevent those areas from being removed from the
rbtree by accident.

Signed-off-by: Hoeun Ryu <hoeun.ryu@gmail.com>
---
include/linux/vmalloc.h | 1 +
mm/vmalloc.c | 9 ++++++---
2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 46991ad..3df53fc 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -19,6 +19,7 @@ struct notifier_block; /* in notifier.h */
#define VM_UNINITIALIZED 0x00000020 /* vm_struct is not fully initialized */
#define VM_NO_GUARD 0x00000040 /* don't add guard page */
#define VM_KASAN 0x00000080 /* has allocated kasan shadow memory */
+#define VM_STATIC 0x00000200
/* bits [20..32] reserved for arch specific ioremap internals */

/*
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 8ef8ea1..fb5049a 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1262,7 +1262,7 @@ void __init vmalloc_init(void)
/* Import existing vmlist entries. */
for (tmp = vmlist; tmp; tmp = tmp->next) {
va = kzalloc(sizeof(struct vmap_area), GFP_NOWAIT);
- va->flags = VM_VM_AREA;
+ va->flags = VM_VM_AREA | VM_STATIC;
va->va_start = (unsigned long)tmp->addr;
va->va_end = va->va_start + tmp->size;
va->vm = tmp;
@@ -1480,7 +1480,7 @@ struct vm_struct *remove_vm_area(const void *addr)
might_sleep();

va = find_vmap_area((unsigned long)addr);
- if (va && va->flags & VM_VM_AREA) {
+ if (va && va->flags & VM_VM_AREA && likely(!(va->flags & VM_STATIC))) {
struct vm_struct *vm = va->vm;

spin_lock(&vmap_area_lock);
@@ -1510,7 +1510,7 @@ static void __vunmap(const void *addr, int deallocate_pages)

area = remove_vm_area(addr);
if (unlikely(!area)) {
- WARN(1, KERN_ERR "Trying to vfree() nonexistent vm area (%p)\n",
+ WARN(1, KERN_ERR "Trying to vfree() nonexistent or static vm area (%p)\n",
addr);
return;
}
@@ -2708,6 +2708,9 @@ static int s_show(struct seq_file *m, void *p)
if (v->phys_addr)
seq_printf(m, " phys=%pa", &v->phys_addr);

+ if (v->flags & VM_STATIC)
+ seq_puts(m, " static");
+
if (v->flags & VM_IOREMAP)
seq_puts(m, " ioremap");

--
2.7.4