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/* SPDX-License-Identifier: GPL-2.0 */
/*
* x86 KFENCE support.
*
* Copyright (C) 2020, Google LLC.
*/
#ifndef _ASM_X86_KFENCE_H
#define _ASM_X86_KFENCE_H
#ifndef MODULE
#include <linux/bug.h>
#include <linux/kfence.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/set_memory.h>
#include <asm/tlbflush.h>
/* Force 4K pages for __kfence_pool. */
static inline bool arch_kfence_init_pool(void)
{
unsigned long addr;
for (addr = (unsigned long)__kfence_pool; is_kfence_address((void *)addr);
addr += PAGE_SIZE) {
unsigned int level;
if (!lookup_address(addr, &level))
return false;
if (level != PG_LEVEL_4K)
set_memory_4k(addr, 1);
}
return true;
}
/* Protect the given page and flush TLB. */
static inline bool kfence_protect_page(unsigned long addr, bool protect)
{
unsigned int level;
pte_t *pte = lookup_address(addr, &level);
pteval_t val, new;
if (WARN_ON(!pte || level != PG_LEVEL_4K))
return false;
val = pte_val(*pte);
/*
* protect requires making the page not-present. If the PTE is
* already in the right state, there's nothing to do.
*/
if (protect != !!(val & _PAGE_PRESENT))
return true;
/*
* Otherwise, flip the Present bit, taking care to avoid writing an
* L1TF-vulnerable PTE (not present, without the high address bits
* set).
*/
new = val ^ _PAGE_PRESENT;
set_pte(pte, __pte(flip_protnone_guard(val, new, PTE_PFN_MASK)));
/*
* If the page was protected (non-present) and we're making it
* present, there is no need to flush the TLB at all.
*/
if (!protect)
return true;
/*
* We need to avoid IPIs, as we may get KFENCE allocations or faults
* with interrupts disabled. Therefore, the below is best-effort, and
* does not flush TLBs on all CPUs. We can tolerate some inaccuracy;
* lazy fault handling takes care of faults after the page is PRESENT.
*/
/*
* Flush this CPU's TLB, assuming whoever did the allocation/free is
* likely to continue running on this CPU.
*/
preempt_disable();
flush_tlb_one_kernel(addr);
preempt_enable();
return true;
}
#endif /* !MODULE */
#endif /* _ASM_X86_KFENCE_H */
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