[PATCH 4.19 33/57] arm64: entry: Make the kpti trampolines kpti sequence optional

Greg Kroah-Hartman
2022-03-21T14:02:23Z

From: James Morse <james.morse@arm.com>

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>
---
arch/arm64/kernel/entry.S | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -970,9 +970,10 @@ 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
@@ -994,8 +995,12 @@ alternative_insn isb, nop, ARM64_WORKARO
#endif
prfm plil1strm, [x30, #(1b - \vector_start)]
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
@@ -1012,15 +1017,15 @@ alternative_insn isb, nop, ARM64_WORKARO
eret
.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

@@ -1031,7 +1036,7 @@ alternative_insn isb, nop, ARM64_WORKARO
.pushsection ".entry.tramp.text", "ax"
.align 11
ENTRY(tramp_vectors)
- generate_tramp_vector
+ generate_tramp_vector kpti=1
END(tramp_vectors)

ENTRY(tramp_exit_native)