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#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/mutex.h>
// __stp_tf_vma_mutex protects the hash table.
static DEFINE_MUTEX(__stp_tf_vma_mutex);
#define __STP_TF_HASH_BITS 4
#define __STP_TF_TABLE_SIZE (1 << __STP_TF_HASH_BITS)
struct __stp_tf_vma_entry {
struct hlist_node hlist;
pid_t pid;
unsigned long addr;
unsigned long vm_start;
unsigned long vm_end;
unsigned long vm_pgoff;
// Is that enough? Should we store a dcookie for vm_file?
};
static struct hlist_head __stp_tf_vma_table[__STP_TF_TABLE_SIZE];
static inline u32
__stp_tf_vma_hash(struct task_struct *tsk, unsigned long addr)
{
#ifdef CONFIG_64BIT
return (jhash_3words(tsk->pid, (u32)addr, (u32)(addr >> 32), 0)
& (__STP_TF_TABLE_SIZE - 1));
#else
return (jhash_2words(tsk->pid, addr, 0) & (__STP_TF_TABLE_SIZE - 1));
#endif
}
// Get vma_entry if the vma is present in the vma hash table.
// Returns NULL if not present.
static struct __stp_tf_vma_entry *
__stp_tf_get_vma_entry(struct task_struct *tsk, unsigned long addr)
{
struct hlist_head *head;
struct hlist_node *node;
struct __stp_tf_vma_entry *entry;
mutex_lock(&__stp_tf_vma_mutex);
head = &__stp_tf_vma_table[__stp_tf_vma_hash(tsk, addr)];
hlist_for_each_entry(entry, node, head, hlist) {
if (tsk->pid == entry->pid
&& addr == entry->addr) {
mutex_unlock(&__stp_tf_vma_mutex);
return entry;
}
}
mutex_unlock(&__stp_tf_vma_mutex);
return NULL;
}
// Add the vma info to the vma hash table.
static int
__stp_tf_add_vma(struct task_struct *tsk, unsigned long addr,
struct vm_area_struct *vma)
{
struct hlist_head *head;
struct hlist_node *node;
struct __stp_tf_vma_entry *entry;
mutex_lock(&__stp_tf_vma_mutex);
head = &__stp_tf_vma_table[__stp_tf_vma_hash(tsk, addr)];
hlist_for_each_entry(entry, node, head, hlist) {
if (tsk->pid == entry->pid
&& addr == entry->addr) {
printk(KERN_NOTICE
"vma (pid: %d, vm_start: 0x%lx) present?\n",
tsk->pid, vma->vm_start);
mutex_unlock(&__stp_tf_vma_mutex);
return -EBUSY; /* Already there */
}
}
// Using kmalloc here to allocate an element. Could cause some
// memory fragmentation if overused.
entry = kmalloc(sizeof(struct __stp_tf_vma_entry), GFP_KERNEL);
if (!entry) {
mutex_unlock(&__stp_tf_vma_mutex);
return -ENOMEM;
}
entry->pid = tsk->pid;
entry->addr = addr;
entry->vm_start = vma->vm_start;
entry->vm_end = vma->vm_end;
entry->vm_pgoff = vma->vm_pgoff;
hlist_add_head(&entry->hlist, head);
mutex_unlock(&__stp_tf_vma_mutex);
return 0;
}
// Remove the vma entry from the vma hash table.
static int
__stp_tf_remove_vma_entry(struct __stp_tf_vma_entry *entry)
{
struct hlist_head *head;
struct hlist_node *node;
int found = 0;
if (entry != NULL) {
mutex_lock(&__stp_tf_vma_mutex);
hlist_del(&entry->hlist);
kfree(entry);
mutex_unlock(&__stp_tf_vma_mutex);
}
return 0;
}
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