arm64: kernel: avoid literal load of virtual address with MMU off

Literal loads of virtual addresses are subject to runtime relocation when
CONFIG_RELOCATABLE=y, and given that the relocation routines run with the
MMU and caches enabled, literal loads of relocated values performed with
the MMU off are not guaranteed to return the latest value unless the
memory covering the literal is cleaned to the PoC explicitly.

So defer the literal load until after the MMU has been enabled, just like
we do for primary_switch() and secondary_switch() in head.S.

Fixes: 1e48ef7fcc37 ("arm64: add support for building vmlinux as a relocatable PIE binary")
Cc: <stable@vger.kernel.org> # 4.6+
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index 9a3aec97ac09..ccf79d849e0a 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -101,12 +101,20 @@ ENTRY(cpu_resume)
         bl      el2_setup               // if in EL2 drop to EL1 cleanly
         /* enable the MMU early - so we can access sleep_save_stash by va */
         adr_l   lr, __enable_mmu        /* __cpu_setup will return here */
-        ldr     x27, =_cpu_resume       /* __enable_mmu will branch here */
+        adr_l   x27, _resume_switched   /* __enable_mmu will branch here */
         adrp    x25, idmap_pg_dir
         adrp    x26, swapper_pg_dir
         b       __cpu_setup
 ENDPROC(cpu_resume)
 
+        .pushsection    ".idmap.text", "ax"
+_resume_switched:
+        ldr     x8, =_cpu_resume
+        br      x8
+ENDPROC(_resume_switched)
+        .ltorg
+        .popsection
+
 ENTRY(_cpu_resume)
         mrs     x1, mpidr_el1
         adrp    x8, mpidr_hash