Merge remote-tracking branch 'device-mapper/for-next'

[karo-tx-linux.git] / arch / arc / kernel / entry-arcv2.S

diff --git a/arch/arc/kernel/entry-arcv2.S b/arch/arc/kernel/entry-arcv2.S
index cbfec79137bf77735fa675d0eb2be57da217ba63..b178302947065660bc4765d86f66276045e29055 100644 (file)
--- a/arch/arc/kernel/entry-arcv2.S
+++ b/arch/arc/kernel/entry-arcv2.S
@@ -211,7 +211,11 @@ debug_marker_syscall:
 ; (since IRQ NOT allowed in DS in ARCv2, this can only happen if orig
 ; entry was via Exception in DS which got preempted in kernel).
 ;
-; IRQ RTIE won't reliably restore DE bit and/or BTA, needs handling
+; IRQ RTIE won't reliably restore DE bit and/or BTA, needs workaround
+;
+; Solution is return from Intr w/o any delay slot quirks into a kernel trampoline
+; and from pure kernel mode return to delay slot which handles DS bit/BTA correctly
+
 .Lintr_ret_to_delay_slot:
 debug_marker_ds:
 
@@ -222,18 +226,23 @@ debug_marker_ds:
        ld      r2, [sp, PT_ret]
        ld      r3, [sp, PT_status32]
 
+       ; STAT32 for Int return created from scratch
+       ; (No delay dlot, disable Further intr in trampoline)
+
        bic     r0, r3, STATUS_U_MASK|STATUS_DE_MASK|STATUS_IE_MASK|STATUS_L_MASK
        st      r0, [sp, PT_status32]
 
        mov     r1, .Lintr_ret_to_delay_slot_2
        st      r1, [sp, PT_ret]
 
+       ; Orig exception PC/STAT32 safekept @orig_r0 and @event stack slots
        st      r2, [sp, 0]
        st      r3, [sp, 4]
 
        b       .Lisr_ret_fast_path
 
 .Lintr_ret_to_delay_slot_2:
+       ; Trampoline to restore orig exception PC/STAT32/BTA/AUX_USER_SP
        sub     sp, sp, SZ_PT_REGS
        st      r9, [sp, -4]
 
@@ -243,11 +252,19 @@ debug_marker_ds:
        ld      r9, [sp, 4]
        sr      r9, [erstatus]
 
+       ; restore AUX_USER_SP if returning to U mode
+       bbit0   r9, STATUS_U_BIT, 1f
+       ld      r9, [sp, PT_sp]
+       sr      r9, [AUX_USER_SP]
+
+1:
        ld      r9, [sp, 8]
        sr      r9, [erbta]
 
        ld      r9, [sp, -4]
        add     sp, sp, SZ_PT_REGS
+
+       ; return from pure kernel mode to delay slot
        rtie
 
 END(ret_from_exception)