This is a note to let you know that I've just added the patch titled
arm64: entry: Make the trampoline cleanup optional
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm64-entry-make-the-trampoline-cleanup-optional.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f44bc676e3ffb0cc5512bc3790f81526139b8686
Author: James Morse <james.morse@xxxxxxx>
Date: Tue Mar 15 18:23:59 2022 +0000
arm64: entry: Make the trampoline cleanup optional
commit d739da1694a0eaef0358a42b76904b611539b77b upstream.
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@xxxxxxxxxxxxxxx>
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: James Morse <james.morse@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 98991aa9d0b1..a6dcd68ce7de 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -61,16 +61,20 @@
.align 7
.Lventry_start\@:
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
-alternative_if ARM64_UNMAP_KERNEL_AT_EL0
.if \el == 0
+ /*
+ * 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
+.Lskip_tramp_vectors_cleanup\@:
.endif
-alternative_else_nop_endif
#endif
sub sp, sp, #S_FRAME_SIZE
@@ -1079,7 +1083,7 @@ 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?
