From: James Morse <james.morse@arm.com>
Date: Wed, 24 Nov 2021 15:36:12 +0000
Subject: arm64: entry: Make the trampoline cleanup optional
Git-commit: d739da1694a0eaef0358a42b76904b611539b77b
Patch-mainline: v5.17 or v5.17-rc8 (next release)
References: bsc#1085308 CVE-2022-23960 CVE-2022-0001 CVE-2022-0002
Subsequent patches will add additional sets of vectors that use
the same tricks as the kpti vectors to reach the full-fat vectors.
The full-fat vectors contain some cleanup for kpti that is patched
in by alternatives when kpti is in use. Once there are additional
vectors, the cleanup will be needed in more cases.
But on big/little systems, the cleanup would be harmful if no
trampoline vector were in use. Instead of forcing CPUs that don't
need a trampoline vector to use one, make the trampoline cleanup
optional.
Entry at the top of the vectors will skip the cleanup. The trampoline
vectors can then skip the first instruction, triggering the cleanup
to run.
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: Matthias Brugger <mbrugger@suse.com>
---
arch/arm64/kernel/entry.S | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index d97eb024adec..bdbdb92b5f77 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -40,14 +40,18 @@
.Lventry_start\@:
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
.if \el == 0
-alternative_if ARM64_UNMAP_KERNEL_AT_EL0
+ /*
+ * This must be the first instruction of the EL0 vector entries. It is
+ * skipped by the trampoline vectors, to trigger the cleanup.
+ */
+ b .Lskip_tramp_vectors_cleanup\@
.if \regsize == 64
mrs x30, tpidrro_el0
msr tpidrro_el0, xzr
.else
mov x30, xzr
.endif
-alternative_else_nop_endif
+.Lskip_tramp_vectors_cleanup\@:
.endif
#endif
@@ -661,7 +665,7 @@ alternative_if_not ARM64_WORKAROUND_CAVIUM_TX2_219_PRFM
prfm plil1strm, [x30, #(1b - tramp_vectors)]
alternative_else_nop_endif
msr vbar_el1, x30
- add x30, x30, #(1b - tramp_vectors)
+ add x30, x30, #(1b - tramp_vectors + 4)
isb
ret
.org 1b + 128 // Did we overflow the ventry slot?
--
2.34.1