diff options
Diffstat (limited to 'arch/arc/kernel/ctx_sw_asm.S')
| -rw-r--r-- | arch/arc/kernel/ctx_sw_asm.S | 72 |
1 files changed, 39 insertions, 33 deletions
diff --git a/arch/arc/kernel/ctx_sw_asm.S b/arch/arc/kernel/ctx_sw_asm.S index 95cba6265e2b..59d779004e64 100644 --- a/arch/arc/kernel/ctx_sw_asm.S +++ b/arch/arc/kernel/ctx_sw_asm.S @@ -13,48 +13,54 @@ #define KSP_WORD_OFF ((TASK_THREAD + THREAD_KSP) / 4) -;################### Low Level Context Switch ########################## +; IN +; - r0: prev task (also current) +; - r1: next task +; OUT +; - r0: prev task (so r0 not touched) .section .sched.text,"ax",@progbits - .align 4 - .global __switch_to - .type __switch_to, @function -__switch_to: - CFI_STARTPROC - - /* Save regs on kernel mode stack of task */ - st.a blink, [sp, -4] - st.a fp, [sp, -4] +ENTRY_CFI(__switch_to) + + /* save kernel stack frame regs of @prev task */ + push blink + CFI_DEF_CFA_OFFSET 4 + CFI_OFFSET r31, -4 + + push fp + CFI_DEF_CFA_OFFSET 8 + CFI_OFFSET r27, -8 + + mov fp, sp + CFI_DEF_CFA_REGISTER r27 + + /* kernel mode callee regs of @prev */ SAVE_CALLEE_SAVED_KERNEL - /* Save the now KSP in task->thread.ksp */ + /* save final SP to @prev->thread.ksp */ #if KSP_WORD_OFF <= 255 st.as sp, [r0, KSP_WORD_OFF] #else /* Workaround for NR_CPUS=4k as ST.as can only take s9 offset */ - add2 r24, r0, KSP_WORD_OFF - st sp, [r24] + add2 r10, r0, KSP_WORD_OFF + st sp, [r10] #endif - /* - * Return last task in r0 (return reg) - * On ARC, Return reg = First Arg reg = r0. - * Since we already have last task in r0, - * don't need to do anything special to return it - */ - - /* - * switch to new task, contained in r1 - * Temp reg r3 is required to get the ptr to store val - */ - SET_CURR_TASK_ON_CPU r1, r3 - - /* reload SP with kernel mode stack pointer in task->thread.ksp */ - ld.as sp, [r1, KSP_WORD_OFF] - - /* restore the registers */ + /* update @next in _current_task[] and GP register caching it */ + SET_CURR_TASK_ON_CPU r1, r10 + + /* load SP from @next->thread.ksp */ + ld.as sp, [r1, KSP_WORD_OFF] + + /* restore callee regs, stack frame regs of @next */ RESTORE_CALLEE_SAVED_KERNEL - ld.ab fp, [sp, 4] - ld.ab blink, [sp, 4] - j [blink] + pop fp + CFI_RESTORE r27 + CFI_DEF_CFA r28, 4 + + pop blink + CFI_RESTORE r31 + CFI_DEF_CFA_OFFSET 0 + + j [blink] END_CFI(__switch_to) |