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KVM: arm64: Apply hyp relocations at runtime 

KVM nVHE code runs under a different VA mapping than the kernel, hence
so far it avoided using absolute addressing because the VA in a constant
pool is relocated by the linker to a kernel VA (see hyp_symbol_addr).

Now the kernel has access to a list of positions that contain a kimg VA
but will be accessed only in hyp execution context. These are generated
by the gen-hyprel build-time tool and stored in .hyp.reloc.

Add early boot pass over the entries and convert the kimg VAs to hyp VAs.
Note that this requires for .hyp* ELF sections to be mapped read-write
at that point.

Signed-off-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210105180541.65031-6-dbrazdil@google.com
This commit is contained in:
David Brazdil 2021-01-05 18:05:38 +00:00 committed by Marc Zyngier
parent 8c49b5d43d
commit 6ec6259d70
4 changed files with 33 additions and 1 deletions
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1
arch/arm64/include/asm/kvm_mmu.h
View File

@ -129,6 +129,7 @@ alternative_cb_end
void kvm_update_va_mask(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst);
void kvm_compute_layout(void);
void kvm_apply_hyp_relocations(void);
static __always_inline unsigned long __kern_hyp_va(unsigned long v)
{

1
arch/arm64/include/asm/sections.h
View File

@ -12,6 +12,7 @@ extern char __hibernate_exit_text_start[], __hibernate_exit_text_end[];
extern char __hyp_idmap_text_start[], __hyp_idmap_text_end[];
extern char __hyp_text_start[], __hyp_text_end[];
extern char __hyp_rodata_start[], __hyp_rodata_end[];
extern char __hyp_reloc_begin[], __hyp_reloc_end[];
extern char __idmap_text_start[], __idmap_text_end[];
extern char __initdata_begin[], __initdata_end[];
extern char __inittext_begin[], __inittext_end[];

4
arch/arm64/kernel/smp.c
View File

@ -434,8 +434,10 @@ static void __init hyp_mode_check(void)
"CPU: CPUs started in inconsistent modes");
else
pr_info("CPU: All CPU(s) started at EL1\n");
if (IS_ENABLED(CONFIG_KVM) && !is_kernel_in_hyp_mode())
if (IS_ENABLED(CONFIG_KVM) && !is_kernel_in_hyp_mode()) {
kvm_compute_layout();
kvm_apply_hyp_relocations();
}
}
void __init smp_cpus_done(unsigned int max_cpus)

28
arch/arm64/kvm/va_layout.c
View File

@ -81,6 +81,34 @@ __init void kvm_compute_layout(void)
init_hyp_physvirt_offset();
}
/*
* The .hyp.reloc ELF section contains a list of kimg positions that
* contains kimg VAs but will be accessed only in hyp execution context.
* Convert them to hyp VAs. See gen-hyprel.c for more details.
*/
__init void kvm_apply_hyp_relocations(void)
{
int32_t *rel;
int32_t *begin = (int32_t *)__hyp_reloc_begin;
int32_t *end = (int32_t *)__hyp_reloc_end;
for (rel = begin; rel < end; ++rel) {
uintptr_t *ptr, kimg_va;
/*
* Each entry contains a 32-bit relative offset from itself
* to a kimg VA position.
*/
ptr = (uintptr_t *)lm_alias((char *)rel + *rel);
/* Read the kimg VA value at the relocation address. */
kimg_va = *ptr;
/* Convert to hyp VA and store back to the relocation address. */
*ptr = __early_kern_hyp_va((uintptr_t)lm_alias(kimg_va));
}
}
static u32 compute_instruction(int n, u32 rd, u32 rn)
{
u32 insn = AARCH64_BREAK_FAULT;