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 | 6 ++- arch/arm64/include/asm/mmu.h | 6 +++ arch/arm64/kernel/cpu_errata.c | 65 +++++++++++++++++++++++++++++++- arch/arm64/kvm/hyp/hyp-entry.S | 54 ++++++++++++++++++++++++++ 5 files changed, 130 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h index df8fe8ecc37e..64ae14371cae 100644 --- a/arch/arm64/include/asm/cpucaps.h +++ b/arch/arm64/include/asm/cpucaps.h @@ -54,7 +54,8 @@ #define ARM64_WORKAROUND_1463225 33 #define ARM64_SSBS 34 #define ARM64_WORKAROUND_1542419 35 +#define ARM64_SPECTRE_BHB 36
-#define ARM64_NCAPS 36 +#define ARM64_NCAPS 37
#endif /* __ASM_CPUCAPS_H */ diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h index b2558447c67d..44d3fdbcdf62 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h @@ -438,7 +438,8 @@ static inline void *kvm_get_hyp_vector(void) void *vect = kern_hyp_va(kvm_ksym_ref(__kvm_hyp_vector)); int slot = -1;
- if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR) && data->fn) { + if ((cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR) || + cpus_have_const_cap(ARM64_SPECTRE_BHB)) && data->template_start) { vect = kern_hyp_va(kvm_ksym_ref(__bp_harden_hyp_vecs_start)); slot = data->hyp_vectors_slot; } @@ -467,7 +468,8 @@ static inline int kvm_map_vectors(void) * !HBP + HEL2 -> allocate one vector slot and use exec mapping * HBP + HEL2 -> use hardened vertors and use exec mapping */ - if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR)) { + if (cpus_have_const_cap(ARM64_HARDEN_BRANCH_PREDICTOR) || + cpus_have_const_cap(ARM64_SPECTRE_BHB)) { __kvm_bp_vect_base = kvm_ksym_ref(__bp_harden_hyp_vecs_start); __kvm_bp_vect_base = kern_hyp_va(__kvm_bp_vect_base); } diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h index 1f61519fc23f..b37d185e0e84 100644 --- a/arch/arm64/include/asm/mmu.h +++ b/arch/arm64/include/asm/mmu.h @@ -49,6 +49,12 @@ 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; };
#if (defined(CONFIG_HARDEN_BRANCH_PREDICTOR) || \ diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index d055ed21eeeb..791dd8dadd9e 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -97,6 +97,14 @@ DEFINE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data); #ifdef CONFIG_KVM_INDIRECT_VECTORS extern char __smccc_workaround_1_smc_start[]; extern char __smccc_workaround_1_smc_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) @@ -110,11 +118,11 @@ 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 void install_bp_hardening_cb(bp_hardening_cb_t fn, const char *hyp_vecs_start, const char *hyp_vecs_end) { - static DEFINE_SPINLOCK(bp_lock); int cpu, slot = -1;
spin_lock(&bp_lock); @@ -133,6 +141,7 @@ 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 @@ -935,3 +944,57 @@ enum mitigation_state arm64_get_spectre_bhb_state(void) { return spectre_bhb_state; } + +#ifdef CONFIG_KVM_INDIRECT_VECTORS +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) { + slot = atomic_inc_return(&arm64_el2_vector_last_slot); + BUG_ON(slot >= BP_HARDEN_EL2_SLOTS); + __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 diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S index ea063312bca1..05593f631eca 100644 --- a/arch/arm64/kvm/hyp/hyp-entry.S +++ b/arch/arm64/kvm/hyp/hyp-entry.S @@ -334,4 +334,58 @@ ENTRY(__smccc_workaround_1_smc_start) ldp x0, x1, [sp, #(8 * 2)] add sp, sp, #(8 * 4) ENTRY(__smccc_workaround_1_smc_end) + +ENTRY(__smccc_workaround_3_smc_start) + esb + 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) + esb + 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) + esb + 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) + esb + 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) #endif