xtensa: use abi_* register names in the kernel exit code

Using plain register names is prone to errors when code is changed and
new calls are added between the register load and use. Change plain
register names to abi_* names in the call-heavy part of the kernel exit
code to clearly indicate what's supposed to be preserved and what's not.
Re-align code while at it.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index c85597a..d09f2c3 100644 (file)
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -462,11 +462,11 @@ KABI_W    or      a3, a3, a2
         * exception handler and call the exception handler.
         */
 
-       l32i    abi_arg1, a1, PT_EXCCAUSE       # pass EXCCAUSE
-       rsr     abi_tmp0, excsave1
-       addx4   abi_tmp0, abi_arg1, abi_tmp0
-       l32i    abi_tmp0, abi_tmp0, EXC_TABLE_DEFAULT   # load handler
-       mov     abi_arg0, a1                    # pass stack frame
+       l32i            abi_arg1, a1, PT_EXCCAUSE       # pass EXCCAUSE
+       rsr             abi_tmp0, excsave1
+       addx4           abi_tmp0, abi_arg1, abi_tmp0
+       l32i            abi_tmp0, abi_tmp0, EXC_TABLE_DEFAULT   # load handler
+       mov             abi_arg0, a1                    # pass stack frame
 
        /* Call the second-level handler */
 
@@ -477,23 +477,23 @@ KABI_W    or      a3, a3, a2
 common_exception_return:
 
 #if XTENSA_FAKE_NMI
-       l32i    abi_tmp0, a1, PT_EXCCAUSE
-       movi    abi_tmp1, EXCCAUSE_MAPPED_NMI
-       l32i    abi_saved1, a1, PT_PS
-       beq     abi_tmp0, abi_tmp1, .Lrestore_state
+       l32i            abi_tmp0, a1, PT_EXCCAUSE
+       movi            abi_tmp1, EXCCAUSE_MAPPED_NMI
+       l32i            abi_saved1, a1, PT_PS
+       beq             abi_tmp0, abi_tmp1, .Lrestore_state
 #endif
 .Ltif_loop:
-       irq_save a2, a3
+       irq_save        abi_tmp0, abi_tmp1
 #ifdef CONFIG_TRACE_IRQFLAGS
        abi_call        trace_hardirqs_off
 #endif
 
        /* Jump if we are returning from kernel exceptions. */
 
-       l32i    abi_saved1, a1, PT_PS
-       GET_THREAD_INFO(a2, a1)
-       l32i    a4, a2, TI_FLAGS
-       _bbci.l abi_saved1, PS_UM_BIT, .Lexit_tif_loop_kernel
+       l32i            abi_saved1, a1, PT_PS
+       GET_THREAD_INFO(abi_tmp0, a1)
+       l32i            abi_saved0, abi_tmp0, TI_FLAGS
+       _bbci.l         abi_saved1, PS_UM_BIT, .Lexit_tif_loop_kernel
 
        /* Specific to a user exception exit:
         * We need to check some flags for signal handling and rescheduling,
@@ -502,75 +502,77 @@ common_exception_return:
         * Note that we don't disable interrupts here. 
         */
 
-       _bbsi.l a4, TIF_NEED_RESCHED, .Lresched
-       movi    a2, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL
-       bnone   a4, a2, .Lexit_tif_loop_user
+       _bbsi.l         abi_saved0, TIF_NEED_RESCHED, .Lresched
+       movi            abi_tmp0, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL
+       bnone           abi_saved0, abi_tmp0, .Lexit_tif_loop_user
 
-       l32i    a4, a1, PT_DEPC
-       bgeui   a4, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lrestore_state
+       l32i            abi_tmp0, a1, PT_DEPC
+       bgeui           abi_tmp0, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lrestore_state
 
        /* Call do_signal() */
 
 #ifdef CONFIG_TRACE_IRQFLAGS
        abi_call        trace_hardirqs_on
 #endif
-       rsil    a2, 0
-       mov     abi_arg0, a1
+       rsil            abi_tmp0, 0
+       mov             abi_arg0, a1
        abi_call        do_notify_resume        # int do_notify_resume(struct pt_regs*)
-       j       .Ltif_loop
+       j               .Ltif_loop
 
 .Lresched:
 #ifdef CONFIG_TRACE_IRQFLAGS
        abi_call        trace_hardirqs_on
 #endif
-       rsil    a2, 0
+       rsil            abi_tmp0, 0
        abi_call        schedule        # void schedule (void)
-       j       .Ltif_loop
+       j               .Ltif_loop
 
 .Lexit_tif_loop_kernel:
 #ifdef CONFIG_PREEMPTION
-       _bbci.l a4, TIF_NEED_RESCHED, .Lrestore_state
+       _bbci.l         abi_saved0, TIF_NEED_RESCHED, .Lrestore_state
 
        /* Check current_thread_info->preempt_count */
 
-       l32i    a4, a2, TI_PRE_COUNT
-       bnez    a4, .Lrestore_state
+       l32i            abi_tmp1, abi_tmp0, TI_PRE_COUNT
+       bnez            abi_tmp1, .Lrestore_state
        abi_call        preempt_schedule_irq
 #endif
-       j       .Lrestore_state
+       j               .Lrestore_state
 
 .Lexit_tif_loop_user:
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
-       _bbci.l a4, TIF_DB_DISABLED, 1f
+       _bbci.l         abi_saved0, TIF_DB_DISABLED, 1f
        abi_call        restore_dbreak
 1:
 #endif
 #ifdef CONFIG_DEBUG_TLB_SANITY
-       l32i    a4, a1, PT_DEPC
-       bgeui   a4, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lrestore_state
+       l32i            abi_tmp0, a1, PT_DEPC
+       bgeui           abi_tmp0, VALID_DOUBLE_EXCEPTION_ADDRESS, .Lrestore_state
        abi_call        check_tlb_sanity
 #endif
 
 .Lrestore_state:
 #ifdef CONFIG_TRACE_IRQFLAGS
-       extui   a4, abi_saved1, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
-       bgei    a4, LOCKLEVEL, 1f
+       extui           abi_tmp0, abi_saved1, PS_INTLEVEL_SHIFT, PS_INTLEVEL_WIDTH
+       bgei            abi_tmp0, LOCKLEVEL, 1f
        abi_call        trace_hardirqs_on
 1:
 #endif
-       /* Restore optional registers. */
+       /*
+        * Restore optional registers.
+        * abi_arg* are used as temporary registers here.
+        */
 
-       load_xtregs_opt a1 a2 a4 a5 a6 a7 PT_XTREGS_OPT
+       load_xtregs_opt a1 abi_tmp0 abi_arg0 abi_arg1 abi_arg2 abi_arg3 PT_XTREGS_OPT
 
        /* Restore SCOMPARE1 */
 
 #if XCHAL_HAVE_S32C1I
-       l32i    a2, a1, PT_SCOMPARE1
-       wsr     a2, scompare1
+       l32i            abi_tmp0, a1, PT_SCOMPARE1
+       wsr             abi_tmp0, scompare1
 #endif
-       wsr     abi_saved1, ps          /* disable interrupts */
-
-       _bbci.l abi_saved1, PS_UM_BIT, kernel_exception_exit
+       wsr             abi_saved1, ps          /* disable interrupts */
+       _bbci.l         abi_saved1, PS_UM_BIT, kernel_exception_exit
 
 user_exception_exit: