arm64: kernel: drop use of x24 from primary boot path

Keeping __PHYS_OFFSET in x24 is actually less clear than simply taking
the value of __PHYS_OFFSET using an adrp instruction in the three places
that we need it. So change that.

Reviewed-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 45b865e022ccb1e4c8019f0658c0affca18371ab..4dee51045e790283d42641c30e06e31af1ec8e54 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -211,8 +211,8 @@ efi_header_end:
 ENTRY(stext)
        bl      preserve_boot_args
        bl      el2_setup                       // Drop to EL1, w0=cpu_boot_mode
-       adrp    x24, __PHYS_OFFSET
-       and     x23, x24, MIN_KIMG_ALIGN - 1    // KASLR offset, defaults to 0
+       adrp    x23, __PHYS_OFFSET
+       and     x23, x23, MIN_KIMG_ALIGN - 1    // KASLR offset, defaults to 0
        bl      set_cpu_boot_mode_flag
        bl      __create_page_tables
        /*
@@ -412,6 +412,8 @@ ENDPROC(__create_page_tables)
 
 /*
  * The following fragment of code is executed with the MMU enabled.
+ *
+ *   x0 = __PHYS_OFFSET
  */
        .set    initial_sp, init_thread_union + THREAD_START_SP
 __primary_switched:
@@ -420,6 +422,12 @@ __primary_switched:
        msr     vbar_el1, x8                    // vector table address
        isb
 
+       str_l   x21, __fdt_pointer, x5          // Save FDT pointer
+
+       ldr_l   x4, kimage_vaddr                // Save the offset between
+       sub     x4, x4, x0                      // the kernel virtual and
+       str_l   x4, kimage_voffset, x5          // physical mappings
+
        // Clear BSS
        adr_l   x0, __bss_start
        mov     x1, xzr
@@ -432,12 +440,6 @@ __primary_switched:
        mov     x4, sp
        and     x4, x4, #~(THREAD_SIZE - 1)
        msr     sp_el0, x4                      // Save thread_info
-       str_l   x21, __fdt_pointer, x5          // Save FDT pointer
-
-       ldr_l   x4, kimage_vaddr                // Save the offset between
-       sub     x4, x4, x24                     // the kernel virtual and
-       str_l   x4, kimage_voffset, x5          // physical mappings
-
        mov     x29, #0
 #ifdef CONFIG_KASAN
        bl      kasan_early_init
@@ -794,6 +796,7 @@ __primary_switch:
        bl      __relocate_kernel
 #ifdef CONFIG_RANDOMIZE_BASE
        ldr     x8, =__primary_switched
+       adrp    x0, __PHYS_OFFSET
        blr     x8
 
        /*
@@ -818,5 +821,6 @@ __primary_switch:
 #endif
 #endif
        ldr     x8, =__primary_switched
+       adrp    x0, __PHYS_OFFSET
        br      x8
 ENDPROC(__primary_switch)