UPSTREAM: arm64: entry: Add fake CPU feature for unmapping the kernel at EL0
Allow explicit disabling of the entry trampoline on the kernel command
line (kpti=off) by adding a fake CPU feature (ARM64_UNMAP_KERNEL_AT_EL0)
that can be used to toggle the alternative sequences in our entry code and
avoid use of the trampoline altogether if desired. This also allows us to
make use of a static key in arm64_kernel_unmapped_at_el0().
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from commit ea1e3de85e94d711f63437c04624aa0e8de5c8b3)
[toddpoynor@google.com: fixup context, cpus_have_const_cap ->
cpus_have_cap]
Change-Id: I72936d608b0d4c0dd9725eced7674b95e4abcf2d
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Git-commit: f79ff2d82888428c2b0f7dbdedce553313156fae
Git-repo: https://android.googlesource.com/kernel/common/
[ckadabi@codeaurora.org: Update ARM64_NCAPS and ARM64_UNMAP_KERNEL_AT_EL0
values based on current supported capabilities]
Signed-off-by: Channagoud Kadabi <ckadabi@codeaurora.org>
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 139a5e3..43a7f64 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -74,6 +74,7 @@
.macro kernel_ventry, el, label, regsize = 64
.align 7
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+alternative_if ARM64_UNMAP_KERNEL_AT_EL0
.if \el == 0
.if \regsize == 64
mrs x30, tpidrro_el0
@@ -82,6 +83,7 @@
mov x30, xzr
.endif
.endif
+alternative_else_nop_endif
#endif
sub sp, sp, #S_FRAME_SIZE
@@ -269,10 +271,9 @@
ldr lr, [sp, #S_LR]
add sp, sp, #S_FRAME_SIZE // restore sp
-#ifndef CONFIG_UNMAP_KERNEL_AT_EL0
- eret
-#else
.if \el == 0
+alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
bne 4f
msr far_el1, x30
tramp_alias x30, tramp_exit_native
@@ -280,10 +281,10 @@
4:
tramp_alias x30, tramp_exit_compat
br x30
+#endif
.else
eret
.endif
-#endif
.endm
.macro irq_stack_entry