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

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commit c47e4d04ba 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>
This commit is contained in:
James Morse 2021-11-18 13:16:23 +00:00 committed by Greg Kroah-Hartman
parent a40472d463
commit 6895584a92
1 changed files with 12 additions and 6 deletions
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18
arch/arm64/kernel/entry.S
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@ -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)