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Store small shadow fields in-place

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Signed-off-by: Seth Jennings <sjenning@redhat.com>
This commit is contained in:
Seth Jennings 2014-09-08 15:02:34 -05:00
parent 3343eed007
commit eb75f0aaae
1 changed files with 39 additions and 9 deletions
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48
kmod/core/shadow.c
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@ -53,10 +53,34 @@ struct kpatch_shadow {
struct hlist_node node;
struct rcu_head rcu_head;
void *obj;
char *var;
union {
char *var; /* assumed to be 4-byte aligned */
unsigned long flags;
};
void *data;
};
#define SHADOW_FLAG_INPLACE 0x1
#define SHADOW_FLAG_RESERVED0 0x2 /* reserved for future use */
#define SHADOW_FLAG_MASK 0x3
#define SHADOW_PTR_MASK (~(SHADOW_FLAG_MASK))
static inline void shadow_set_inplace(struct kpatch_shadow *shadow)
{
shadow->flags |= SHADOW_FLAG_INPLACE;
}
static inline int shadow_is_inplace(struct kpatch_shadow *shadow)
{
return shadow->flags & SHADOW_FLAG_INPLACE;
}
static inline char *shadow_var(struct kpatch_shadow *shadow)
{
return (char *)((unsigned long)shadow->var & SHADOW_PTR_MASK);
}
void *kpatch_shadow_alloc(void *obj, char *var, size_t size, gfp_t gfp)
{
unsigned long flags;
@ -72,10 +96,15 @@ void *kpatch_shadow_alloc(void *obj, char *var, size_t size, gfp_t gfp)
if (!shadow->var)
return NULL;
shadow->data = kmalloc(size, gfp);
if (!shadow->data) {
kfree(shadow->var);
return NULL;
if (size <= sizeof(shadow->data)) {
shadow->data = &shadow->data;
shadow_set_inplace(shadow);
} else {
shadow->data = kmalloc(size, gfp);
if (!shadow->data) {
kfree(shadow->var);
return NULL;
}
}
spin_lock_irqsave(&kpatch_shadow_lock, flags);
@ -92,8 +121,9 @@ static void kpatch_shadow_rcu_free(struct rcu_head *head)
shadow = container_of(head, struct kpatch_shadow, rcu_head);
kfree(shadow->data);
kfree(shadow->var);
if (!shadow_is_inplace(shadow))
kfree(shadow->data);
kfree(shadow_var(shadow));
kfree(shadow);
}
@ -106,7 +136,7 @@ void kpatch_shadow_free(void *obj, char *var)
hash_for_each_possible(kpatch_shadow_hash, shadow, node,
(unsigned long)obj) {
if (shadow->obj == obj && !strcmp(shadow->var, var)) {
if (shadow->obj == obj && !strcmp(shadow_var(shadow), var)) {
hash_del_rcu(&shadow->node);
spin_unlock_irqrestore(&kpatch_shadow_lock, flags);
call_rcu(&shadow->rcu_head, kpatch_shadow_rcu_free);
@ -126,7 +156,7 @@ void *kpatch_shadow_get(void *obj, char *var)
hash_for_each_possible_rcu(kpatch_shadow_hash, shadow, node,
(unsigned long)obj) {
if (shadow->obj == obj && !strcmp(shadow->var, var)) {
if (shadow->obj == obj && !strcmp(shadow_var(shadow), var)) {
rcu_read_unlock();
return shadow->data;
}