arm64: entry: Make the kpti trampoline's kpti sequence optional

commit c47e4d04ba0f1ea17353d85d45f611277507e07a upstream.

Spectre-BHB needs to add sequences to the vectors. Having one global
set of vectors is a problem for big/little systems where the sequence
is costly on cpus that are not vulnerable.

Making the vectors per-cpu in the style of KVM's bh_harden_hyp_vecs
requires the vectors to be generated by macros.

Make the kpti re-mapping of the kernel optional, so the macros can be
used without kpti.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 11e3fa0..d87b6c8 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -646,9 +646,10 @@ alternative_else_nop_endif
        sub     \dst, \dst, PAGE_SIZE
        .endm
 
-       .macro tramp_ventry, vector_start, regsize
+       .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
@@ -671,9 +672,14 @@ alternative_insn isb, nop, ARM64_WORKAROUND_QCOM_FALKOR_E1003
 alternative_if_not ARM64_WORKAROUND_CAVIUM_TX2_219_PRFM
        prfm    plil1strm, [x30, #(1b - \vector_start)]
 alternative_else_nop_endif
+
        msr     vbar_el1, x30
-       add     x30, x30, #(1b - \vector_start + 4)
        isb
+       .else
+       ldr     x30, =vectors
+       .endif // \kpti == 1
+
+       add     x30, x30, #(1b - \vector_start + 4)
        ret
 .org 1b + 128  // Did we overflow the ventry slot?
        .endm
@@ -691,15 +697,15 @@ alternative_else_nop_endif
        sb
        .endm
 
-       .macro  generate_tramp_vector
+       .macro  generate_tramp_vector,  kpti
 .Lvector_start\@:
        .space  0x400
 
        .rept   4
-       tramp_ventry    .Lvector_start\@, 64
+       tramp_ventry    .Lvector_start\@, 64, \kpti
        .endr
        .rept   4
-       tramp_ventry    .Lvector_start\@, 32
+       tramp_ventry    .Lvector_start\@, 32, \kpti
        .endr
        .endm
 
@@ -710,7 +716,7 @@ alternative_else_nop_endif
        .pushsection ".entry.tramp.text", "ax"
        .align  11
 SYM_CODE_START_NOALIGN(tramp_vectors)
-       generate_tramp_vector
+       generate_tramp_vector   kpti=1
 SYM_CODE_END(tramp_vectors)
 
 SYM_CODE_START(tramp_exit_native)