KVM writes the Spectre-v2 mitigation template at the beginning of each vector when a CPU requires a specific sequence to run.
Because the template is copied, it can not be modified by the alternatives at runtime. As the KVM template code is intertwined with the bp-hardening callbacks, all templates must have a bp-hardening callback.
Add templates for calling ARCH_WORKAROUND_3 and one for each value of K in the brancy-loop. Identify these sequences by a new parameter template_start, and add a copy of install_bp_hardening_cb() that is able to install them.
Signed-off-by: James Morse james.morse@arm.com --- arch/arm64/include/asm/cpucaps.h | 3 +- arch/arm64/include/asm/kvm_mmu.h | 2 +- arch/arm64/include/asm/mmu.h | 6 +++ arch/arm64/kernel/bpi.S | 50 ++++++++++++++++++++++ arch/arm64/kernel/cpu_errata.c | 71 +++++++++++++++++++++++++++++++- 5 files changed, 128 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h index d4a46764c1ad..9935e55a3cc7 100644 --- a/arch/arm64/include/asm/cpucaps.h +++ b/arch/arm64/include/asm/cpucaps.h @@ -39,7 +39,8 @@ #define ARM64_SSBD 18 #define ARM64_MISMATCHED_CACHE_TYPE 19 #define ARM64_WORKAROUND_1188873 20 +#define ARM64_SPECTRE_BHB 21
-#define ARM64_NCAPS 21 +#define ARM64_NCAPS 22
#endif /* __ASM_CPUCAPS_H */ diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h index ff721659eb94..4a2c95854856 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h @@ -362,7 +362,7 @@ static inline void *kvm_get_hyp_vector(void) struct bp_hardening_data *data = arm64_get_bp_hardening_data(); void *vect = kvm_ksym_ref(__kvm_hyp_vector);
- if (data->fn) { + if (data->template_start) { vect = __bp_harden_hyp_vecs_start + data->hyp_vectors_slot * SZ_2K;
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h index 5eff1c49270d..f4377b005cba 100644 --- a/arch/arm64/include/asm/mmu.h +++ b/arch/arm64/include/asm/mmu.h @@ -45,6 +45,12 @@ typedef void (*bp_hardening_cb_t)(void); struct bp_hardening_data { int hyp_vectors_slot; bp_hardening_cb_t fn; + + /* + * template_start is only used by the BHB mitigation to identify the + * hyp_vectors_slot sequence. + */ + const char *template_start; };
#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR diff --git a/arch/arm64/kernel/bpi.S b/arch/arm64/kernel/bpi.S index dc4eb154e33b..313f2b59eef9 100644 --- a/arch/arm64/kernel/bpi.S +++ b/arch/arm64/kernel/bpi.S @@ -73,3 +73,53 @@ ENTRY(__smccc_workaround_1_smc_end) ENTRY(__smccc_workaround_1_hvc_start) smccc_workaround_1 hvc ENTRY(__smccc_workaround_1_hvc_end) + +ENTRY(__smccc_workaround_3_smc_start) + sub sp, sp, #(8 * 4) + stp x2, x3, [sp, #(8 * 0)] + stp x0, x1, [sp, #(8 * 2)] + mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3 + smc #0 + ldp x2, x3, [sp, #(8 * 0)] + ldp x0, x1, [sp, #(8 * 2)] + add sp, sp, #(8 * 4) +ENTRY(__smccc_workaround_3_smc_end) + +ENTRY(__spectre_bhb_loop_k8_start) + sub sp, sp, #(8 * 2) + stp x0, x1, [sp, #(8 * 0)] + mov x0, #8 +2: b . + 4 + subs x0, x0, #1 + b.ne 2b + dsb nsh + isb + ldp x0, x1, [sp, #(8 * 0)] + add sp, sp, #(8 * 2) +ENTRY(__spectre_bhb_loop_k8_end) + +ENTRY(__spectre_bhb_loop_k24_start) + sub sp, sp, #(8 * 2) + stp x0, x1, [sp, #(8 * 0)] + mov x0, #24 +2: b . + 4 + subs x0, x0, #1 + b.ne 2b + dsb nsh + isb + ldp x0, x1, [sp, #(8 * 0)] + add sp, sp, #(8 * 2) +ENTRY(__spectre_bhb_loop_k24_end) + +ENTRY(__spectre_bhb_loop_k32_start) + sub sp, sp, #(8 * 2) + stp x0, x1, [sp, #(8 * 0)] + mov x0, #32 +2: b . + 4 + subs x0, x0, #1 + b.ne 2b + dsb nsh + isb + ldp x0, x1, [sp, #(8 * 0)] + add sp, sp, #(8 * 2) +ENTRY(__spectre_bhb_loop_k32_end) diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 0d08249cbdab..acccc685b670 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -74,6 +74,14 @@ extern char __smccc_workaround_1_smc_start[]; extern char __smccc_workaround_1_smc_end[]; extern char __smccc_workaround_1_hvc_start[]; extern char __smccc_workaround_1_hvc_end[]; +extern char __smccc_workaround_3_smc_start[]; +extern char __smccc_workaround_3_smc_end[]; +extern char __spectre_bhb_loop_k8_start[]; +extern char __spectre_bhb_loop_k8_end[]; +extern char __spectre_bhb_loop_k24_start[]; +extern char __spectre_bhb_loop_k24_end[]; +extern char __spectre_bhb_loop_k32_start[]; +extern char __spectre_bhb_loop_k32_end[];
static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start, const char *hyp_vecs_end) @@ -87,12 +95,14 @@ static void __copy_hyp_vect_bpi(int slot, const char *hyp_vecs_start, flush_icache_range((uintptr_t)dst, (uintptr_t)dst + SZ_2K); }
+static DEFINE_SPINLOCK(bp_lock); +static int last_slot = -1; + static void __install_bp_hardening_cb(bp_hardening_cb_t fn, const char *hyp_vecs_start, const char *hyp_vecs_end) { - static int last_slot = -1; - static DEFINE_SPINLOCK(bp_lock); + int cpu, slot = -1;
spin_lock(&bp_lock); @@ -113,6 +123,7 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
__this_cpu_write(bp_hardening_data.hyp_vectors_slot, slot); __this_cpu_write(bp_hardening_data.fn, fn); + __this_cpu_write(bp_hardening_data.template_start, hyp_vecs_start); spin_unlock(&bp_lock); } #else @@ -544,3 +555,59 @@ const struct arm64_cpu_capabilities arm64_errata[] = { { } }; + +#ifdef CONFIG_KVM +static const char *kvm_bhb_get_vecs_end(const char *start) +{ + if (start == __smccc_workaround_3_smc_start) + return __smccc_workaround_3_smc_end; + else if (start == __spectre_bhb_loop_k8_start) + return __spectre_bhb_loop_k8_end; + else if (start == __spectre_bhb_loop_k24_start) + return __spectre_bhb_loop_k24_end; + else if (start == __spectre_bhb_loop_k32_start) + return __spectre_bhb_loop_k32_end; + + return NULL; +} + +void kvm_setup_bhb_slot(const char *hyp_vecs_start) +{ + int cpu, slot = -1; + const char *hyp_vecs_end; + + if (!IS_ENABLED(CONFIG_KVM) || !is_hyp_mode_available()) + return; + + hyp_vecs_end = kvm_bhb_get_vecs_end(hyp_vecs_start); + if (WARN_ON_ONCE(!hyp_vecs_start || !hyp_vecs_end)) + return; + + spin_lock(&bp_lock); + for_each_possible_cpu(cpu) { + if (per_cpu(bp_hardening_data.template_start, cpu) == hyp_vecs_start) { + slot = per_cpu(bp_hardening_data.hyp_vectors_slot, cpu); + break; + } + } + + if (slot == -1) { + last_slot++; + BUG_ON(((__bp_harden_hyp_vecs_end - __bp_harden_hyp_vecs_start) + / SZ_2K) <= last_slot); + slot = last_slot; + __copy_hyp_vect_bpi(slot, hyp_vecs_start, hyp_vecs_end); + } + + __this_cpu_write(bp_hardening_data.hyp_vectors_slot, slot); + __this_cpu_write(bp_hardening_data.template_start, hyp_vecs_start); + spin_unlock(&bp_lock); +} +#else +#define __smccc_workaround_3_smc_start NULL +#define __spectre_bhb_loop_k8_start NULL +#define __spectre_bhb_loop_k24_start NULL +#define __spectre_bhb_loop_k32_start NULL + +void kvm_setup_bhb_slot(const char *hyp_vecs_start) { }; +#endif