os-workshop

commit 78f833375450b7fb59459e1488bae7304c01a8e5
parent 076c950cbce75bd1a65f78262f7bfd9832a5724e
Author: Brian Swetland <swetland@frotz.net>
Date:   Mon,  9 May 2022 11:44:03 -0700

misc/traps: make this demo run again

- use memory info from hw/platform.h
- don't return from fatal exceptions

Diffstat:
M
misc/traps.c
 | 
30
++++++++++++++++--------------

1 file changed, 16 insertions(+), 14 deletions(-)
diff --git a/misc/traps.c b/misc/traps.c
@@ -3,20 +3,20 @@
 
 #include <hw/riscv.h>
 #include <hw/debug.h>
+#include <hw/platform.h>
 
-#define MEMORY_BASE (0x80000000)
-#define MEMORY_SIZE (128*1024*1024)
-#define MEMORY_TOP (MEMORY_BASE + MEMORY_SIZE)
+#define MEMORY_TOP (DRAM_BASE + DRAM_SIZE)
 
-#define SVC_SP (MEMORY_TOP)
-#define USER_SP (MEMORY_TOP - (1024*1024))
+#define SVC_SP (MEMORY_TOP - 8*1024)
+#define USER_SP (MEMORY_TOP - 16*1024)
 
 extern void svc_exception_entry(void);
+void enter_mode_u(uint32_t a0, uint32_t a1, uint32_t user_pc, uint32_t user_sp);
 
 void svc_exception_handler(uint32_t regs[32]) {
 	uint32_t cause = csr_read(CSR_SCAUSE);
 	uint32_t val = csr_read(CSR_STVAL);
-	xprintf("SUPERVISOR EXCEPTION %08x %08x %08x\n",
+	xprintf("\nSUPERVISOR EXCEPTION %08x %08x %08x\n",
 		cause, val, (unsigned) regs);
 
 	xprintf("pc %08x ra %08x sp %08x gp %08x\n",
@@ -25,28 +25,30 @@ void svc_exception_handler(uint32_t regs[32]) {
 		regs[4], regs[5], regs[6], regs[7]);
 	xprintf("fp %08x s1 %08x a0 %08x a1 %08x\n",
 		regs[8], regs[9], regs[10], regs[11]);
-	xprintf("a2 %08x a3 %08x a4 %08x a5 %08x\n",
+	xprintf("a2 %08x a3 %08x a4 %08x a5 %08x\n\n",
 		regs[12], regs[13], regs[14], regs[15]);
 
 	if (cause == EXCn_ECALL_UMODE) {
 		// advance return address to next instr
 		regs[0] += 4;
+		xprintf("RETURNING FROM ECALL\n");
+		return;
 	}
 
-	csr_clr(CSR_SIP, INTb_SVC_SW);	
+	xprintf("HALTED\n");
+	for (;;) ;
 }
 
-void enter_mode_u(uint32_t a0, uint32_t a1, uint32_t user_pc, uint32_t user_sp);
-
 void user_start(uint32_t hartid, uint32_t fdt) {
 	xprintf("Hello, User Mode hartid=%08x fdt=%08x\n", hartid, fdt);
 
-	// illegal write from user mode
-	// csr_write(CSR_MEPC, 0x42);
-
 	// syscall
 	asm volatile ("ecall");
 
+	// illegal write from user mode
+	csr_write(CSR_MEPC, 0x42);
+
+	xprintf("\nSTOP\n");
 	for (;;) ;
 }
 
@@ -57,7 +59,7 @@ void start(uint32_t hartid, uint32_t fdt) {
 	csr_write(CSR_STVEC, (uintptr_t) svc_exception_entry);
 	csr_write(CSR_SSCRATCH, SVC_SP);
 
-	csr_set(CSR_SIE, INTb_SVC_SW);
+	//csr_set(CSR_SIE, INTb_SVC_SW);
 
 	enter_mode_u(hartid, fdt, (uintptr_t)user_start, USER_SP);