cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

vmacache.c (2792B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * Copyright (C) 2014 Davidlohr Bueso.
      4 */
      5#include <linux/sched/signal.h>
      6#include <linux/sched/task.h>
      7#include <linux/mm.h>
      8#include <linux/vmacache.h>
      9
     10/*
     11 * Hash based on the pmd of addr if configured with MMU, which provides a good
     12 * hit rate for workloads with spatial locality.  Otherwise, use pages.
     13 */
     14#ifdef CONFIG_MMU
     15#define VMACACHE_SHIFT	PMD_SHIFT
     16#else
     17#define VMACACHE_SHIFT	PAGE_SHIFT
     18#endif
     19#define VMACACHE_HASH(addr) ((addr >> VMACACHE_SHIFT) & VMACACHE_MASK)
     20
     21/*
     22 * This task may be accessing a foreign mm via (for example)
     23 * get_user_pages()->find_vma().  The vmacache is task-local and this
     24 * task's vmacache pertains to a different mm (ie, its own).  There is
     25 * nothing we can do here.
     26 *
     27 * Also handle the case where a kernel thread has adopted this mm via
     28 * kthread_use_mm(). That kernel thread's vmacache is not applicable to this mm.
     29 */
     30static inline bool vmacache_valid_mm(struct mm_struct *mm)
     31{
     32	return current->mm == mm && !(current->flags & PF_KTHREAD);
     33}
     34
     35void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
     36{
     37	if (vmacache_valid_mm(newvma->vm_mm))
     38		current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
     39}
     40
     41static bool vmacache_valid(struct mm_struct *mm)
     42{
     43	struct task_struct *curr;
     44
     45	if (!vmacache_valid_mm(mm))
     46		return false;
     47
     48	curr = current;
     49	if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
     50		/*
     51		 * First attempt will always be invalid, initialize
     52		 * the new cache for this task here.
     53		 */
     54		curr->vmacache.seqnum = mm->vmacache_seqnum;
     55		vmacache_flush(curr);
     56		return false;
     57	}
     58	return true;
     59}
     60
     61struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
     62{
     63	int idx = VMACACHE_HASH(addr);
     64	int i;
     65
     66	count_vm_vmacache_event(VMACACHE_FIND_CALLS);
     67
     68	if (!vmacache_valid(mm))
     69		return NULL;
     70
     71	for (i = 0; i < VMACACHE_SIZE; i++) {
     72		struct vm_area_struct *vma = current->vmacache.vmas[idx];
     73
     74		if (vma) {
     75#ifdef CONFIG_DEBUG_VM_VMACACHE
     76			if (WARN_ON_ONCE(vma->vm_mm != mm))
     77				break;
     78#endif
     79			if (vma->vm_start <= addr && vma->vm_end > addr) {
     80				count_vm_vmacache_event(VMACACHE_FIND_HITS);
     81				return vma;
     82			}
     83		}
     84		if (++idx == VMACACHE_SIZE)
     85			idx = 0;
     86	}
     87
     88	return NULL;
     89}
     90
     91#ifndef CONFIG_MMU
     92struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
     93					   unsigned long start,
     94					   unsigned long end)
     95{
     96	int idx = VMACACHE_HASH(start);
     97	int i;
     98
     99	count_vm_vmacache_event(VMACACHE_FIND_CALLS);
    100
    101	if (!vmacache_valid(mm))
    102		return NULL;
    103
    104	for (i = 0; i < VMACACHE_SIZE; i++) {
    105		struct vm_area_struct *vma = current->vmacache.vmas[idx];
    106
    107		if (vma && vma->vm_start == start && vma->vm_end == end) {
    108			count_vm_vmacache_event(VMACACHE_FIND_HITS);
    109			return vma;
    110		}
    111		if (++idx == VMACACHE_SIZE)
    112			idx = 0;
    113	}
    114
    115	return NULL;
    116}
    117#endif