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KVM: arm64: Add guard pages for pKVM (protected nVHE) hypervisor stack

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Map the stack pages in the flexible private VA range and allocate
guard pages below the stack as unbacked VA space. The stack is aligned
so that any valid stack address has PAGE_SHIFT bit as 1 - this is used
for overflow detection (implemented in a subsequent patch in the series)

Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220420214317.3303360-5-kaleshsingh@google.com
This commit is contained in:
Kalesh Singh 2022-04-20 14:42:55 -07:00 committed by Marc Zyngier
parent ce3354318a
commit 1a919b17ef
1 changed files with 28 additions and 3 deletions
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31
arch/arm64/kvm/hyp/nvhe/setup.c
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@ -99,17 +99,42 @@ static int recreate_hyp_mappings(phys_addr_t phys, unsigned long size,
return ret;
for (i = 0; i < hyp_nr_cpus; i++) {
struct kvm_nvhe_init_params *params = per_cpu_ptr(&kvm_init_params, i);
unsigned long hyp_addr;
start = (void *)kern_hyp_va(per_cpu_base[i]);
end = start + PAGE_ALIGN(hyp_percpu_size);
ret = pkvm_create_mappings(start, end, PAGE_HYP);
if (ret)
return ret;
end = (void *)per_cpu_ptr(&kvm_init_params, i)->stack_hyp_va;
start = end - PAGE_SIZE;
ret = pkvm_create_mappings(start, end, PAGE_HYP);
/*
* Allocate a contiguous HYP private VA range for the stack
* and guard page. The allocation is also aligned based on
* the order of its size.
*/
ret = pkvm_alloc_private_va_range(PAGE_SIZE * 2, &hyp_addr);
if (ret)
return ret;
/*
* Since the stack grows downwards, map the stack to the page
* at the higher address and leave the lower guard page
* unbacked.
*
* Any valid stack address now has the PAGE_SHIFT bit as 1
* and addresses corresponding to the guard page have the
* PAGE_SHIFT bit as 0 - this is used for overflow detection.
*/
hyp_spin_lock(&pkvm_pgd_lock);
ret = kvm_pgtable_hyp_map(&pkvm_pgtable, hyp_addr + PAGE_SIZE,
PAGE_SIZE, params->stack_pa, PAGE_HYP);
hyp_spin_unlock(&pkvm_pgd_lock);
if (ret)
return ret;
/* Update stack_hyp_va to end of the stack's private VA range */
params->stack_hyp_va = hyp_addr + (2 * PAGE_SIZE);
}
/*