arm64: kernel: use literal for relocated address of __secondary_switched

We can simply use a relocated 64-bit literal to store the address of
__secondary_switched(), and the relocation code will ensure that it
holds the correct value at secondary entry time, as long as we make sure
that the literal is not dereferenced until after we have enabled the MMU.

So jump via a small __secondary_switch() function covered by the ID map
that performs the literal load and branch-to-register.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index ac27d8d..f13276d 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -468,9 +468,7 @@ __mmap_switched:
        str     x15, [x11, x23]
        b       0b
 
-2:     adr_l   x8, kimage_vaddr                // make relocated kimage_vaddr
-       dc      cvac, x8                        // value visible to secondaries
-       dsb     sy                              // with MMU off
+2:
 #endif
 
        adr_l   sp, initial_sp, x4
@@ -699,12 +697,9 @@ secondary_startup:
        adrp    x26, swapper_pg_dir
        bl      __cpu_setup                     // initialise processor
 
-       ldr     x8, kimage_vaddr
-       ldr     w9, 0f
-       sub     x27, x8, w9, sxtw               // address to jump to after enabling the MMU
+       adr_l   x27, __secondary_switch         // address to jump to after enabling the MMU
        b       __enable_mmu
 ENDPROC(secondary_startup)
-0:     .long   (_text - TEXT_OFFSET) - __secondary_switched
 
 __secondary_switched:
        adr_l   x5, vectors
@@ -806,3 +801,8 @@ __no_granule_support:
        wfi
        b 1b
 ENDPROC(__no_granule_support)
+
+__secondary_switch:
+       ldr     x8, =__secondary_switched
+       br      x8
+ENDPROC(__secondary_switch)