[stable:PATCH v4.14.274 18/27] arm64: entry: Add non-kpti __bp_harden_el1_vectors for mitigations

James Morse
2022-03-31T18:35:46Z

commit aff65393fa1401e034656e349abd655cfe272de0 upstream.

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>
---
arch/arm64/kernel/entry.S | 34 +++++++++++++++++++++++++++++++++-
1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f50539bdf5be..bf6f4513c81f 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -1025,10 +1025,11 @@ 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
@@ -1111,6 +1112,37 @@ __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, sync_invalid // Synchronous EL1t
+ kernel_ventry 1, irq_invalid // IRQ EL1t
+ kernel_ventry 1, fiq_invalid // FIQ EL1t
+ kernel_ventry 1, error_invalid // Error EL1t
+
+ kernel_ventry 1, sync // Synchronous EL1h
+ kernel_ventry 1, irq // IRQ EL1h
+ kernel_ventry 1, fiq_invalid // FIQ EL1h
+ kernel_ventry 1, error_invalid // 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
+ENTRY(__bp_harden_el1_vectors)
+ generate_el1_vector
+END(__bp_harden_el1_vectors)
+ .popsection
+
/*
* Special system call wrappers.
*/
--
2.30.2