cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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drop_caches.c (1898B)

      1// SPDX-License-Identifier: GPL-2.0
      2/*
      3 * Implement the manual drop-all-pagecache function
      4 */
      5
      6#include <linux/pagemap.h>
      7#include <linux/kernel.h>
      8#include <linux/mm.h>
      9#include <linux/fs.h>
     10#include <linux/writeback.h>
     11#include <linux/sysctl.h>
     12#include <linux/gfp.h>
     13#include "internal.h"
     14
     15/* A global variable is a bit ugly, but it keeps the code simple */
     16int sysctl_drop_caches;
     17
     18static void drop_pagecache_sb(struct super_block *sb, void *unused)
     19{
     20	struct inode *inode, *toput_inode = NULL;
     21
     22	spin_lock(&sb->s_inode_list_lock);
     23	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
     24		spin_lock(&inode->i_lock);
     25		/*
     26		 * We must skip inodes in unusual state. We may also skip
     27		 * inodes without pages but we deliberately won't in case
     28		 * we need to reschedule to avoid softlockups.
     29		 */
     30		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
     31		    (mapping_empty(inode->i_mapping) && !need_resched())) {
     32			spin_unlock(&inode->i_lock);
     33			continue;
     34		}
     35		__iget(inode);
     36		spin_unlock(&inode->i_lock);
     37		spin_unlock(&sb->s_inode_list_lock);
     38
     39		invalidate_mapping_pages(inode->i_mapping, 0, -1);
     40		iput(toput_inode);
     41		toput_inode = inode;
     42
     43		cond_resched();
     44		spin_lock(&sb->s_inode_list_lock);
     45	}
     46	spin_unlock(&sb->s_inode_list_lock);
     47	iput(toput_inode);
     48}
     49
     50int drop_caches_sysctl_handler(struct ctl_table *table, int write,
     51		void *buffer, size_t *length, loff_t *ppos)
     52{
     53	int ret;
     54
     55	ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
     56	if (ret)
     57		return ret;
     58	if (write) {
     59		static int stfu;
     60
     61		if (sysctl_drop_caches & 1) {
     62			iterate_supers(drop_pagecache_sb, NULL);
     63			count_vm_event(DROP_PAGECACHE);
     64		}
     65		if (sysctl_drop_caches & 2) {
     66			drop_slab();
     67			count_vm_event(DROP_SLAB);
     68		}
     69		if (!stfu) {
     70			pr_info("%s (%d): drop_caches: %d\n",
     71				current->comm, task_pid_nr(current),
     72				sysctl_drop_caches);
     73		}
     74		stfu |= sysctl_drop_caches & 4;
     75	}
     76	return 0;
     77}