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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genpool.c (3399B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * MCE event pool management in MCE context
      4 *
      5 * Copyright (C) 2015 Intel Corp.
      6 * Author: Chen, Gong <gong.chen@linux.intel.com>
      7 */
      8#include <linux/smp.h>
      9#include <linux/mm.h>
     10#include <linux/genalloc.h>
     11#include <linux/llist.h>
     12#include "internal.h"
     13
     14/*
     15 * printk() is not safe in MCE context. This is a lock-less memory allocator
     16 * used to save error information organized in a lock-less list.
     17 *
     18 * This memory pool is only to be used to save MCE records in MCE context.
     19 * MCE events are rare, so a fixed size memory pool should be enough. Use
     20 * 2 pages to save MCE events for now (~80 MCE records at most).
     21 */
     22#define MCE_POOLSZ	(2 * PAGE_SIZE)
     23
     24static struct gen_pool *mce_evt_pool;
     25static LLIST_HEAD(mce_event_llist);
     26static char gen_pool_buf[MCE_POOLSZ];
     27
     28/*
     29 * Compare the record "t" with each of the records on list "l" to see if
     30 * an equivalent one is present in the list.
     31 */
     32static bool is_duplicate_mce_record(struct mce_evt_llist *t, struct mce_evt_llist *l)
     33{
     34	struct mce_evt_llist *node;
     35	struct mce *m1, *m2;
     36
     37	m1 = &t->mce;
     38
     39	llist_for_each_entry(node, &l->llnode, llnode) {
     40		m2 = &node->mce;
     41
     42		if (!mce_cmp(m1, m2))
     43			return true;
     44	}
     45	return false;
     46}
     47
     48/*
     49 * The system has panicked - we'd like to peruse the list of MCE records
     50 * that have been queued, but not seen by anyone yet.  The list is in
     51 * reverse time order, so we need to reverse it. While doing that we can
     52 * also drop duplicate records (these were logged because some banks are
     53 * shared between cores or by all threads on a socket).
     54 */
     55struct llist_node *mce_gen_pool_prepare_records(void)
     56{
     57	struct llist_node *head;
     58	LLIST_HEAD(new_head);
     59	struct mce_evt_llist *node, *t;
     60
     61	head = llist_del_all(&mce_event_llist);
     62	if (!head)
     63		return NULL;
     64
     65	/* squeeze out duplicates while reversing order */
     66	llist_for_each_entry_safe(node, t, head, llnode) {
     67		if (!is_duplicate_mce_record(node, t))
     68			llist_add(&node->llnode, &new_head);
     69	}
     70
     71	return new_head.first;
     72}
     73
     74void mce_gen_pool_process(struct work_struct *__unused)
     75{
     76	struct llist_node *head;
     77	struct mce_evt_llist *node, *tmp;
     78	struct mce *mce;
     79
     80	head = llist_del_all(&mce_event_llist);
     81	if (!head)
     82		return;
     83
     84	head = llist_reverse_order(head);
     85	llist_for_each_entry_safe(node, tmp, head, llnode) {
     86		mce = &node->mce;
     87		blocking_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
     88		gen_pool_free(mce_evt_pool, (unsigned long)node, sizeof(*node));
     89	}
     90}
     91
     92bool mce_gen_pool_empty(void)
     93{
     94	return llist_empty(&mce_event_llist);
     95}
     96
     97int mce_gen_pool_add(struct mce *mce)
     98{
     99	struct mce_evt_llist *node;
    100
    101	if (filter_mce(mce))
    102		return -EINVAL;
    103
    104	if (!mce_evt_pool)
    105		return -EINVAL;
    106
    107	node = (void *)gen_pool_alloc(mce_evt_pool, sizeof(*node));
    108	if (!node) {
    109		pr_warn_ratelimited("MCE records pool full!\n");
    110		return -ENOMEM;
    111	}
    112
    113	memcpy(&node->mce, mce, sizeof(*mce));
    114	llist_add(&node->llnode, &mce_event_llist);
    115
    116	return 0;
    117}
    118
    119static int mce_gen_pool_create(void)
    120{
    121	struct gen_pool *tmpp;
    122	int ret = -ENOMEM;
    123
    124	tmpp = gen_pool_create(ilog2(sizeof(struct mce_evt_llist)), -1);
    125	if (!tmpp)
    126		goto out;
    127
    128	ret = gen_pool_add(tmpp, (unsigned long)gen_pool_buf, MCE_POOLSZ, -1);
    129	if (ret) {
    130		gen_pool_destroy(tmpp);
    131		goto out;
    132	}
    133
    134	mce_evt_pool = tmpp;
    135
    136out:
    137	return ret;
    138}
    139
    140int mce_gen_pool_init(void)
    141{
    142	/* Just init mce_gen_pool once. */
    143	if (mce_evt_pool)
    144		return 0;
    145
    146	return mce_gen_pool_create();
    147}