From 03178616604d5d0806fffd46a547c67f1eac54e5 Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Thu, 30 Jan 2020 19:15:27 +0000
Subject: [PATCH] Remove unused fields from struct pcb.

cpu_switch/throw() and savectx() do not save or restore any values in
these fields which mostly held non-callee-save registers.

makectx() copied these fields from kdb_frame, but they weren't used
except for PC_REGS using pcb_sepc.  Change PC_REGS to use
kdb_frame->tf_sepc directly instead.

Reviewed by:	br
MFC after:	2 weeks
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D23395
---
 sys/riscv/include/db_machdep.h | 2 +-
 sys/riscv/include/pcb.h        | 3 ---
 sys/riscv/riscv/genassym.c     | 2 --
 sys/riscv/riscv/machdep.c      | 3 ---
 4 files changed, 1 insertion(+), 9 deletions(-)

diff --git a/sys/riscv/include/db_machdep.h b/sys/riscv/include/db_machdep.h
index acbfa676c294..9271a2757cb8 100644
--- a/sys/riscv/include/db_machdep.h
+++ b/sys/riscv/include/db_machdep.h
@@ -47,7 +47,7 @@
 typedef vm_offset_t	db_addr_t;
 typedef long		db_expr_t;
 
-#define	PC_REGS()	((db_addr_t)kdb_thrctx->pcb_sepc)
+#define	PC_REGS()	((db_addr_t)kdb_frame->tf_sepc)
 
 #define	BKPT_INST	(0x00100073)
 #define	BKPT_SIZE	(INSN_SIZE)
diff --git a/sys/riscv/include/pcb.h b/sys/riscv/include/pcb.h
index 6cc85198a417..44dd23e970e1 100644
--- a/sys/riscv/include/pcb.h
+++ b/sys/riscv/include/pcb.h
@@ -46,15 +46,12 @@ struct pcb {
 	uint64_t	pcb_sp;		/* Stack pointer */
 	uint64_t	pcb_gp;		/* Global pointer */
 	uint64_t	pcb_tp;		/* Thread pointer */
-	uint64_t	pcb_t[7];	/* Temporary registers */
 	uint64_t	pcb_s[12];	/* Saved registers */
-	uint64_t	pcb_a[8];	/* Argument registers */
 	uint64_t	pcb_x[32][2];	/* Floating point registers */
 	uint64_t	pcb_fcsr;	/* Floating point control reg */
 	uint64_t	pcb_fpflags;	/* Floating point flags */
 #define	PCB_FP_STARTED	0x1
 #define	PCB_FP_USERMASK	0x1
-	uint64_t	pcb_sepc;	/* Supervisor exception pc */
 	vm_offset_t	pcb_onfault;	/* Copyinout fault handler */
 };
 
diff --git a/sys/riscv/riscv/genassym.c b/sys/riscv/riscv/genassym.c
index c0c93e5d785c..d164ef8d3263 100644
--- a/sys/riscv/riscv/genassym.c
+++ b/sys/riscv/riscv/genassym.c
@@ -69,9 +69,7 @@ ASSYM(PCB_RA, offsetof(struct pcb, pcb_ra));
 ASSYM(PCB_SP, offsetof(struct pcb, pcb_sp));
 ASSYM(PCB_GP, offsetof(struct pcb, pcb_gp));
 ASSYM(PCB_TP, offsetof(struct pcb, pcb_tp));
-ASSYM(PCB_T, offsetof(struct pcb, pcb_t));
 ASSYM(PCB_S, offsetof(struct pcb, pcb_s));
-ASSYM(PCB_A, offsetof(struct pcb, pcb_a));
 ASSYM(PCB_X, offsetof(struct pcb, pcb_x));
 ASSYM(PCB_FCSR, offsetof(struct pcb, pcb_fcsr));
 
diff --git a/sys/riscv/riscv/machdep.c b/sys/riscv/riscv/machdep.c
index 2a4ed10b1def..fe546789c62e 100644
--- a/sys/riscv/riscv/machdep.c
+++ b/sys/riscv/riscv/machdep.c
@@ -558,15 +558,12 @@ void
 makectx(struct trapframe *tf, struct pcb *pcb)
 {
 
-	memcpy(pcb->pcb_t, tf->tf_t, sizeof(tf->tf_t));
 	memcpy(pcb->pcb_s, tf->tf_s, sizeof(tf->tf_s));
-	memcpy(pcb->pcb_a, tf->tf_a, sizeof(tf->tf_a));
 
 	pcb->pcb_ra = tf->tf_ra;
 	pcb->pcb_sp = tf->tf_sp;
 	pcb->pcb_gp = tf->tf_gp;
 	pcb->pcb_tp = tf->tf_tp;
-	pcb->pcb_sepc = tf->tf_sepc;
 }
 
 void