Commit 1a919b17 authored by Kalesh Singh's avatar Kalesh Singh Committed by Marc Zyngier
Browse files

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



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: default avatarKalesh Singh <kaleshsingh@google.com>
Tested-by: default avatarFuad Tabba <tabba@google.com>
Reviewed-by: default avatarFuad Tabba <tabba@google.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220420214317.3303360-5-kaleshsingh@google.com
parent ce335431

arch/arm64/kvm/hyp/nvhe/setup.c

+28 −3
Original line number Diff line number Diff line
@@ -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);

	}



	/*