ARC: pt_regs update #5: Use real ECR for pt_regs->event vs. synth values

pt_regs->event was set with artificial values to identify the low level
system event (syscall trap / breakpoint trap / exceptions / interrupts)

With r8 saving out of the way, the full word can be used to save real
ECR (Exception Cause Register) which helps idenify the event naturally,
including additional info such as cause code, param.
Only for Interrupts, where ECR is not applicable, do we resort to
synthetic non ECR values.

SAVE_ALL_TRAP/EXCEPTIONS can now be merged as they both use ECR with
different runtime values.

The ptrace helpers now use the sub-fields of ECR to distinguish the
events (e.g. vector 0x25 is trap, param 0 is syscall...)

The following benefits will follow:

(1) This centralizes the location of where ECR is saved and will allow
    the cleanup of task->thread.cause_code ECR placeholder which is set
    in non-uniform way. Then ARC VM code can safely rely on it being
    there for purpose of finer grained VM_EXEC dcache flush (based on
    exec fault: I-TLB Miss)

(2) Further, ECR being passed around from low level handlers as arg can
    be eliminated as it is part of standard reg-file in pt_regs

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

1 files changed, 20 insertions, 16 deletions

diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h
index 7b2de6f7025a..c9938e7a7dbd 100644
--- a/arch/arc/include/asm/ptrace.h
+++ b/arch/arc/include/asm/ptrace.h
@@ -44,15 +44,24 @@ struct pt_regs {
 	long sp;	/* user/kernel sp depending on where we came from  */
 	long orig_r0;
 
-	/*to distinguish bet excp, syscall, irq */
+	/*
+	 * To distinguish bet excp, syscall, irq
+	 * For traps and exceptions, Exception Cause Register.
+	 * 	ECR: <00> <VV> <CC> <PP>
+	 * 	Last word used by Linux for extra state mgmt (syscall-restart)
+	 * For interrupts, use artificial ECR values to note current prio-level
+	 */
 	union {
+		struct {
 #ifdef CONFIG_CPU_BIG_ENDIAN
-		/* so that assembly code is same for LE/BE */
-		unsigned long orig_r8:16, event:16;
+			unsigned long state:8, ecr_vec:8,
+				      ecr_cause:8, ecr_param:8;
 #else
-		unsigned long event:16, orig_r8:16;
+			unsigned long ecr_param:8, ecr_cause:8,
+				      ecr_vec:8, state:8;
 #endif
-		long orig_r8_word;
+		};
+		unsigned long event;
 	};
 
 	long user_r25;
@@ -94,11 +103,13 @@ struct callee_regs {
 /* return 1 if PC in delay slot */
 #define delay_mode(regs) ((regs->status32 & STATUS_DE_MASK) == STATUS_DE_MASK)
 
-#define in_syscall(regs)    (regs->event & orig_r8_IS_SCALL)
-#define in_brkpt_trap(regs) (regs->event & orig_r8_IS_BRKPT)
+#define in_syscall(regs)    ((regs->ecr_vec == ECR_V_TRAP) && !regs->ecr_param)
+#define in_brkpt_trap(regs) ((regs->ecr_vec == ECR_V_TRAP) && regs->ecr_param)
 
-#define syscall_wont_restart(regs) (regs->event |= orig_r8_IS_SCALL_RESTARTED)
-#define syscall_restartable(regs) !(regs->event &  orig_r8_IS_SCALL_RESTARTED)
+#define STATE_SCALL_RESTARTED	0x01
+
+#define syscall_wont_restart(reg) (reg->state |= STATE_SCALL_RESTARTED)
+#define syscall_restartable(reg) !(reg->state &  STATE_SCALL_RESTARTED)
 
 #define current_pt_regs()					\
 ({								\
@@ -115,11 +126,4 @@ static inline long regs_return_value(struct pt_regs *regs)
 
 #endif /* !__ASSEMBLY__ */
 
-#define orig_r8_IS_SCALL		0x0001
-#define orig_r8_IS_SCALL_RESTARTED	0x0002
-#define orig_r8_IS_BRKPT		0x0004
-#define orig_r8_IS_EXCPN		0x0008
-#define orig_r8_IS_IRQ1			0x0010
-#define orig_r8_IS_IRQ2			0x0020
-
 #endif /* __ASM_PTRACE_H */