arm64: smp: unify task and sp setup

Once we enable the MMU, we have to initialize:

* SP_EL0 to point at the active task
* SP to point at the active task's stack
* SCS_SP to point at the active task's shadow stack

For all tasks (including init_task), this information can be derived
from the task's task_struct.

Let's unify __primary_switched and __secondary_switched to consistently
acquire this information from the relevant task_struct. At the same
time, let's fold this together with initializing a task's final frame.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Suzuki Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20210520115031.18509-6-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 9be95e11367d6f823c72d74110063d1116d96a35..e83b2899dce5b2d21bf5746fb776674e8c024c1d 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -395,15 +395,24 @@ SYM_FUNC_START_LOCAL(__create_page_tables)
 SYM_FUNC_END(__create_page_tables)
 
        /*
+        * Initialize CPU registers with task-specific and cpu-specific context.
+        *
         * Create a final frame record at task_pt_regs(current)->stackframe, so
         * that the unwinder can identify the final frame record of any task by
         * its location in the task stack. We reserve the entire pt_regs space
         * for consistency with user tasks and kthreads.
         */
-       .macro setup_final_frame
+       .macro  init_cpu_task tsk, tmp
+       msr     sp_el0, \tsk
+
+       ldr     \tmp, [\tsk, #TSK_STACK]
+       add     sp, \tmp, #THREAD_SIZE
        sub     sp, sp, #PT_REGS_SIZE
+
        stp     xzr, xzr, [sp, #S_STACKFRAME]
        add     x29, sp, #S_STACKFRAME
+
+       scs_load \tsk, \tmp
        .endm
 
 /*
@@ -412,22 +421,16 @@ SYM_FUNC_END(__create_page_tables)
  *   x0 = __PHYS_OFFSET
  */
 SYM_FUNC_START_LOCAL(__primary_switched)
-       adrp    x4, init_thread_union
-       add     sp, x4, #THREAD_SIZE
-       adr_l   x5, init_task
-       msr     sp_el0, x5                      // Save thread_info
+       adr_l   x4, init_task
+       init_cpu_task x4, x5
 
        adr_l   x8, vectors                     // load VBAR_EL1 with virtual
        msr     vbar_el1, x8                    // vector table address
        isb
 
-       stp     xzr, x30, [sp, #-16]!
+       stp     x29, x30, [sp, #-16]!
        mov     x29, sp
 
-#ifdef CONFIG_SHADOW_CALL_STACK
-       adr_l   scs_sp, init_shadow_call_stack  // Set shadow call stack
-#endif
-
        str_l   x21, __fdt_pointer, x5          // Save FDT pointer
 
        ldr_l   x4, kimage_vaddr                // Save the offset between
@@ -459,8 +462,7 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 0:
 #endif
        bl      switch_to_vhe                   // Prefer VHE if possible
-       add     sp, sp, #16
-       setup_final_frame
+       ldp     x29, x30, [sp], #16
        bl      start_kernel
        ASM_BUG()
 SYM_FUNC_END(__primary_switched)
@@ -648,12 +650,7 @@ SYM_FUNC_START_LOCAL(__secondary_switched)
        ldr     x2, [x0, #CPU_BOOT_TASK]
        cbz     x2, __secondary_too_slow
 
-       ldr     x1, [x2, #TSK_STACK]
-       add     sp, x1, #THREAD_SIZE
-
-       msr     sp_el0, x2
-       scs_load x2, x3
-       setup_final_frame
+       init_cpu_task x2, x1
 
 #ifdef CONFIG_ARM64_PTR_AUTH
        ptrauth_keys_init_cpu x2, x3, x4, x5