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: Sasha Levin <sashal@kernel.org>

diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index f217e32929193114d0cf8e5f85fd0bff35ba9cfe..353450011e3d4050eca51a22bd96a64995afab59 100644 (file)
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -29,7 +29,7 @@ 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 6b77e4942495faa3cc27bde90803024365f57e1e..0d89d535720f83be6da27ac1cf27fb5f7720be9b 100644 (file)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -10,11 +10,13 @@
 #include <linux/bsearch.h>
 #include <linux/cpumask.h>
 #include <linux/crash_dump.h>
+#include <linux/percpu.h>
 #include <linux/sort.h>
 #include <linux/stop_machine.h>
 #include <linux/types.h>
 #include <linux/mm.h>
 #include <linux/cpu.h>
+
 #include <asm/cpu.h>
 #include <asm/cpufeature.h>
 #include <asm/cpu_ops.h>
@@ -23,6 +25,7 @@
 #include <asm/processor.h>
 #include <asm/sysreg.h>
 #include <asm/traps.h>
+#include <asm/vectors.h>
 #include <asm/virt.h>
 
 /* Kernel representation of AT_HWCAP and AT_HWCAP2 */
@@ -45,6 +48,8 @@ static struct arm64_cpu_capabilities const __ro_after_init *cpu_hwcaps_ptrs[ARM6
 /* Need also bit for ARM64_CB_PATCH */
 DECLARE_BITMAP(boot_capabilities, ARM64_NPATCHABLE);
 
+DEFINE_PER_CPU_READ_MOSTLY(const char *, this_cpu_vector) = vectors;
+
 /*
  * Flag to indicate if we have computed the system wide
  * capabilities based on the boot time active CPUs. This
@@ -1047,6 +1052,12 @@ 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);
+       }
+
        /*
         * We don't need to rewrite the page-tables if either we've done
         * it already or we have KASLR enabled and therefore have not

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index e4b5a15c2e2e184282236c626d952e71240c5586..fcfbb2b009e239dfa9be52d41ff14c2906feffd9 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -60,7 +60,6 @@
        .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
@@ -75,7 +74,6 @@
        .endif
 .Lskip_tramp_vectors_cleanup\@:
        .endif
-#endif
 
        sub     sp, sp, #S_FRAME_SIZE
 #ifdef CONFIG_VMAP_STACK
@@ -1129,10 +1127,14 @@ alternative_else_nop_endif
        .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
@@ -1193,6 +1195,8 @@ __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 14607fac7ca38364f88ea052545a475366f755d8..768983bd232618afd1c1956d08d02beb8b5f1da6 100644 (file)
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -25,6 +25,7 @@
 #include <asm/debug-monitors.h>
 #include <asm/processor.h>
 #include <asm/thread_info.h>
+#include <asm/vectors.h>
 
 extern struct exception_table_entry __start___kvm_ex_table;
 extern struct exception_table_entry __stop___kvm_ex_table;
@@ -152,7 +153,7 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
 
 static void deactivate_traps_vhe(void)
 {
-       extern char vectors[];  /* kernel exception vectors */
+       const char *host_vectors = vectors;
        write_sysreg(HCR_HOST_VHE_FLAGS, hcr_el2);
 
        /*
@@ -163,7 +164,10 @@ static void deactivate_traps_vhe(void)
        asm(ALTERNATIVE("nop", "isb", ARM64_WORKAROUND_1165522));
 
        write_sysreg(CPACR_EL1_DEFAULT, 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);
 }
 NOKPROBE_SYMBOL(deactivate_traps_vhe);