arm64: Add percpu vectors for EL1

commit bd09128d16fac3c34b80bd6a29088ac632e8ce09 upstream.

The Spectre-BHB workaround adds a firmware call to the vectors. This
is needed on some CPUs, but not others. To avoid the unaffected CPU in
a big/little pair from making the firmware call, create per cpu vectors.

The per-cpu vectors only apply when returning from EL0.

Systems using KPTI can use the canonical 'full-fat' vectors directly at
EL1, the trampoline exit code will switch to this_cpu_vector on exit to
EL0. Systems not using KPTI should always use this_cpu_vector.

this_cpu_vector will point at a vector in tramp_vecs or
__bp_harden_el1_vectors, depending on whether KPTI is in use.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 6ac34c75f4e136a831cfc5d8b9db0281e12355a7..5eff1c49270da799ed5900b06885655b491a9b06 100644 (file)
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -34,7 +34,7 @@ typedef struct {
  */
 #define ASID(mm)       ((mm)->context.id.counter & 0xffff)
 
-static inline bool arm64_kernel_unmapped_at_el0(void)
+static __always_inline bool arm64_kernel_unmapped_at_el0(void)
 {
        return IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0) &&
               cpus_have_const_cap(ARM64_UNMAP_KERNEL_AT_EL0);

diff --git a/arch/arm64/include/asm/vectors.h b/arch/arm64/include/asm/vectors.h
index 16ca7426037533bf9b357c06e3e3e1ca591dffe3..3f76dfd9e0744f06d0d67bd8f11dc1fc65581297 100644 (file)
--- a/arch/arm64/include/asm/vectors.h
+++ b/arch/arm64/include/asm/vectors.h
@@ -5,6 +5,15 @@
 #ifndef __ASM_VECTORS_H
 #define __ASM_VECTORS_H
 
+#include <linux/bug.h>
+#include <linux/percpu.h>
+
+#include <asm/fixmap.h>
+
+extern char vectors[];
+extern char tramp_vectors[];
+extern char __bp_harden_el1_vectors[];
+
 /*
  * Note: the order of this enum corresponds to two arrays in entry.S:
  * tramp_vecs and __bp_harden_el1_vectors. By default the canonical
@@ -31,4 +40,22 @@ enum arm64_bp_harden_el1_vectors {
        EL1_VECTOR_KPTI,
 };
 
+/* The vectors to use on return from EL0. e.g. to remap the kernel */
+DECLARE_PER_CPU_READ_MOSTLY(const char *, this_cpu_vector);
+
+#ifndef CONFIG_UNMAP_KERNEL_AT_EL0
+#define TRAMP_VALIAS   0
+#endif
+
+static inline const char *
+arm64_get_bp_hardening_vector(enum arm64_bp_harden_el1_vectors slot)
+{
+       if (arm64_kernel_unmapped_at_el0())
+               return (char *)TRAMP_VALIAS + SZ_2K * slot;
+
+       WARN_ON_ONCE(slot == EL1_VECTOR_KPTI);
+
+       return __bp_harden_el1_vectors + SZ_2K * slot;
+}
+
 #endif /* __ASM_VECTORS_H */

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 1b5afb80247dd1221b5b84d539e0f14624e45337..b4a6f881c3c0ca79b205e34d2e2412773927fcec 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -20,15 +20,18 @@
 
 #include <linux/bsearch.h>
 #include <linux/cpumask.h>
+#include <linux/percpu.h>
 #include <linux/sort.h>
 #include <linux/stop_machine.h>
 #include <linux/types.h>
+
 #include <asm/cpu.h>
 #include <asm/cpufeature.h>
 #include <asm/cpu_ops.h>
 #include <asm/mmu_context.h>
 #include <asm/processor.h>
 #include <asm/sysreg.h>
+#include <asm/vectors.h>
 #include <asm/virt.h>
 
 unsigned long elf_hwcap __read_mostly;
@@ -49,6 +52,8 @@ unsigned int compat_elf_hwcap2 __read_mostly;
 DECLARE_BITMAP(cpu_hwcaps, ARM64_NCAPS);
 EXPORT_SYMBOL(cpu_hwcaps);
 
+DEFINE_PER_CPU_READ_MOSTLY(const char *, this_cpu_vector) = vectors;
+
 DEFINE_STATIC_KEY_ARRAY_FALSE(cpu_hwcap_keys, ARM64_NCAPS);
 EXPORT_SYMBOL(cpu_hwcap_keys);
 
@@ -821,6 +826,12 @@ kpti_install_ng_mappings(const struct arm64_cpu_capabilities *__unused)
        static bool kpti_applied = false;
        int cpu = smp_processor_id();
 
+       if (__this_cpu_read(this_cpu_vector) == vectors) {
+               const char *v = arm64_get_bp_hardening_vector(EL1_VECTOR_KPTI);
+
+               __this_cpu_write(this_cpu_vector, v);
+       }
+
        if (kpti_applied)
                return;
 

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index ec46c89759a8a5e566ca9117d21f2392ec93d561..746a5fe133c587fd7254315747c43e9d7915d38c 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -75,7 +75,6 @@
        .macro kernel_ventry, el, label, regsize = 64
        .align 7
 .Lventry_start\@:
-#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
        .if     \el == 0
        /*
         * This must be the first instruction of the EL0 vector entries. It is
@@ -90,7 +89,6 @@
        .endif
 .Lskip_tramp_vectors_cleanup\@:
        .endif
-#endif
 
        sub     sp, sp, #S_FRAME_SIZE
        b       el\()\el\()_\label
@@ -983,10 +981,14 @@ __ni_sys_trace:
        .endm
 
        .macro tramp_exit, regsize = 64
-       adr     x30, tramp_vectors
-#ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
-       add     x30, x30, SZ_4K
-#endif
+       tramp_data_read_var     x30, this_cpu_vector
+alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
+       mrs     x29, tpidr_el1
+alternative_else
+       mrs     x29, tpidr_el2
+alternative_endif
+       ldr     x30, [x30, x29]
+
        msr     vbar_el1, x30
        ldr     lr, [sp, #S_LR]
        tramp_unmap_kernel      x29
@@ -1046,6 +1048,8 @@ __entry_tramp_data_vectors:
 __entry_tramp_data___sdei_asm_trampoline_next_handler:
        .quad   __sdei_asm_handler
 #endif /* CONFIG_ARM_SDE_INTERFACE */
+__entry_tramp_data_this_cpu_vector:
+       .quad   this_cpu_vector
        .popsection                             // .rodata
 #endif /* CONFIG_RANDOMIZE_BASE */
 #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 0a2f37bceab0a5110c874dad4d71bbd284d14c4b..1751d2763cc12ef6ad0d05642d8cff3e19c2ad6b 100644 (file)
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -26,7 +26,7 @@
 #include <asm/kvm_emulate.h>
 #include <asm/kvm_hyp.h>
 #include <asm/uaccess.h>
-
+#include <asm/vectors.h>
 extern struct exception_table_entry __start___kvm_ex_table;
 extern struct exception_table_entry __stop___kvm_ex_table;
 
@@ -107,11 +107,14 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
 
 static void __hyp_text __deactivate_traps_vhe(void)
 {
-       extern char vectors[];  /* kernel exception vectors */
+       const char *host_vectors = vectors;
 
        write_sysreg(HCR_HOST_VHE_FLAGS, hcr_el2);
        write_sysreg(CPACR_EL1_FPEN, cpacr_el1);
-       write_sysreg(vectors, vbar_el1);
+
+       if (!arm64_kernel_unmapped_at_el0())
+               host_vectors = __this_cpu_read(this_cpu_vector);
+       write_sysreg(host_vectors, vbar_el1);
 }
 
 static void __hyp_text __deactivate_traps_nvhe(void)