From: James Morse james.morse@arm.com
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@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 | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
--- 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_CAVI 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?