ARC: stop using pt_regs->orig_r8

Historically, pt_regs have had orig_r8, an overloaded container for
  (1) backup copy of r8 (syscall number Trap Exceptions)
  (2) additional system state: (syscall/Exception/Interrupt)

There is no point in keeping (1) since syscall number is never clobbered
in-place, in pt_regs, unlike r0 which duals as first syscall arg as well
as syscall return value and in case of syscall restart, the orig arg0
needs restoring (from orig_r0)  after having been updated in-place with
syscall ret value.

This further paves way to convert (2) to contain ECR itself (rather than
current madeup values)

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

1 files changed, 1 insertions, 12 deletions

diff --git a/arch/arc/include/asm/entry.h b/arch/arc/include/asm/entry.h
index 72a7ed4..de01bc8 100644
--- a/arch/arc/include/asm/entry.h
+++ b/arch/arc/include/asm/entry.h
@@ -422,18 +422,7 @@
  * Save scratch regs for sys calls
  *-------------------------------------------------------------*/
 .macro SAVE_ALL_TRAP
-	/*
-	 * Setup pt_regs->orig_r8.
-	 * Encode syscall number (r8) in upper short word of event type (r9)
-	 * N.B. #1: This is already endian safe (see ptrace.h)
-	 *      #2: Only r9 can be used as scratch as it is already clobbered
-	 *          and it's contents are no longer needed by the latter part
-	 *          of exception prologue
-	 */
-	lsl  r9, r8, 16
-	or   r9, r9, orig_r8_IS_SCALL
-
-	SAVE_ALL_EXCEPTION  r9
+	SAVE_ALL_EXCEPTION  orig_r8_IS_SCALL
 .endm
 
 /*--------------------------------------------------------------