arm64: entry: Add non-kpti __bp_harden_el1_vectors for mitigations

kpti is an optional feature, for systems not using kpti a set of
vectors for the spectre-bhb mitigations is needed.

Add another set of vectors, __bp_harden_el1_vectors, that will be
used if a mitigation is needed and kpti is not in use.

The EL1 ventries are repeated verbatim as there is no additional
work needed for entry from EL1.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index e0a0c1da5db8c9ecc41f944acc53b940e969a2eb..9c4ff75f983e51a12d048ad7082c663087a32574 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -649,10 +649,11 @@ alternative_else_nop_endif
        .macro tramp_ventry, vector_start, regsize, kpti
        .align  7
 1:
-       .if     \kpti == 1
        .if     \regsize == 64
        msr     tpidrro_el0, x30        // Restored in kernel_ventry
        .endif
+
+       .if     \kpti == 1
        /*
         * Defend against branch aliasing attacks by pushing a dummy
         * entry onto the return stack and using a RET instruction to
@@ -739,6 +740,38 @@ SYM_DATA_END(__entry_tramp_data_start)
 #endif /* CONFIG_RANDOMIZE_BASE */
 #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
 
+/*
+ * Exception vectors for spectre mitigations on entry from EL1 when
+ * kpti is not in use.
+ */
+       .macro generate_el1_vector
+.Lvector_start\@:
+       kernel_ventry   1, t, 64, sync          // Synchronous EL1t
+       kernel_ventry   1, t, 64, irq           // IRQ EL1t
+       kernel_ventry   1, t, 64, fiq           // FIQ EL1h
+       kernel_ventry   1, t, 64, error         // Error EL1t
+
+       kernel_ventry   1, h, 64, sync          // Synchronous EL1h
+       kernel_ventry   1, h, 64, irq           // IRQ EL1h
+       kernel_ventry   1, h, 64, fiq           // FIQ EL1h
+       kernel_ventry   1, h, 64, error         // Error EL1h
+
+       .rept   4
+       tramp_ventry    .Lvector_start\@, 64, kpti=0
+       .endr
+       .rept 4
+       tramp_ventry    .Lvector_start\@, 32, kpti=0
+       .endr
+       .endm
+
+       .pushsection ".entry.text", "ax"
+       .align  11
+SYM_CODE_START(__bp_harden_el1_vectors)
+       generate_el1_vector
+SYM_CODE_END(__bp_harden_el1_vectors)
+       .popsection
+
+
 /*
  * Register switch for AArch64. The callee-saved registers need to be saved
  * and restored. On entry: