arm64: switch_to: calculate cpu context pointer using separate register

Commit 0c8c0f03e3a2 ("x86/fpu, sched: Dynamically allocate 'struct fpu'")
moved the thread_struct to the bottom of task_struct. As a result, the
offset is now too large to be used in an immediate add on arm64 with
some kernel configs:

arch/arm64/kernel/entry.S: Assembler messages:
arch/arm64/kernel/entry.S:588: Error: immediate out of range
arch/arm64/kernel/entry.S:597: Error: immediate out of range

This patch calculates the offset using an additional register instead of
an immediate offset.

Fixes: 0c8c0f03e3a2 ("x86/fpu, sched: Dynamically allocate 'struct fpu'")
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f860bfd..e163518 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -585,7 +585,8 @@ ENDPROC(el0_irq)
  *
  */
 ENTRY(cpu_switch_to)
-       add     x8, x0, #THREAD_CPU_CONTEXT
+       mov     x10, #THREAD_CPU_CONTEXT
+       add     x8, x0, x10
        mov     x9, sp
        stp     x19, x20, [x8], #16             // store callee-saved registers
        stp     x21, x22, [x8], #16
@@ -594,7 +595,7 @@ ENTRY(cpu_switch_to)
        stp     x27, x28, [x8], #16
        stp     x29, x9, [x8], #16
        str     lr, [x8]
-       add     x8, x1, #THREAD_CPU_CONTEXT
+       add     x8, x1, x10
        ldp     x19, x20, [x8], #16             // restore callee-saved registers
        ldp     x21, x22, [x8], #16
        ldp     x23, x24, [x8], #16