From 6ec6259d7084ed32e164c9f7b69049464dd90fa5 Mon Sep 17 00:00:00 2001 From: David Brazdil Date: Tue, 5 Jan 2021 18:05:38 +0000 Subject: [PATCH 1/1] 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 Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20210105180541.65031-6-dbrazdil@google.com --- arch/arm64/include/asm/kvm_mmu.h | 1 + arch/arm64/include/asm/sections.h | 1 + arch/arm64/kernel/smp.c | 4 +++- arch/arm64/kvm/va_layout.c | 28 ++++++++++++++++++++++++++++ 4 files changed, 33 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h index e52d82aeadca..6bbb44011c84 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h @@ -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) { diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h index a6f3557d1ab2..2f36b16a5b5d 100644 --- a/arch/arm64/include/asm/sections.h +++ b/arch/arm64/include/asm/sections.h @@ -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[]; diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index ad00f99ee9b0..357590beaabb 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -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) diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c index 70fcd6a12fe1..fee7dcd95d73 100644 --- a/arch/arm64/kvm/va_layout.c +++ b/arch/arm64/kvm/va_layout.c @@ -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; -- 2.20.1