Fix a setcr0 bug which was trashing the condition register; some system

calls are now implemented. A few tests more-or-less pass (but crash on
exit).

plat/linuxppc/emu/emu.c

@@ -58,7 +58,7 @@ static bool getcr(uint8_t bit)
 static void setcr(uint8_t bit, bool value)
 {
 	bit = 31 - bit; /* note PowerPC bit numbering */
-	cpu.cr = cpu.cr & (1<<bit) | (value<<bit);
+	cpu.cr = cpu.cr & ~(1<<bit) | (value<<bit);
 }
 
 static void setcr0(bool setcr0, uint32_t value)
@@ -227,9 +227,9 @@ void dump_state(FILE* stream)
 {
 	int i;
 
+	fprintf(stream, "\n");
 	fprintf(stream, "pc=0x%08x lr=0x%08x ctr=0x%08x xer=0x%08x cr=0x%08x\n",
 		cpu.cia, cpu.lr, cpu.ctr, cpu.xer, cpu.cr);
-	fprintf(stream, "insn=0x%08x", read_long(cpu.cia));
 	for (i=0; i<32; i++)
 	{
 		if ((i % 4) == 0)
@@ -237,6 +237,10 @@ void dump_state(FILE* stream)
 		fprintf(stream, "gpr%02d=0x%08x ", i, cpu.gpr[i]);
 	}
 	fprintf(stream, "\n");
+
+	/* This might fail and cause a reentrant trap if cia is invalid, so
+	 * do it last. */
+	fprintf(stream, "insn=0x%08x", read_long(cpu.cia));
 }
 
 void single_step(void)

plat/linuxppc/emu/main.c

@@ -73,7 +73,11 @@ static uint32_t transform_address(uint32_t address)
 
 uint32_t read_long(uint32_t address)
 {
-	return READ_LONG(ram, transform_address(address));
+	uint32_t v = READ_LONG(ram, transform_address(address));
+	#if 0
+	fprintf(stderr, "read 0x%08x: 0x%08x\n", address, v);
+	#endif
+	return v;
 }
 
 
@@ -99,12 +103,45 @@ void write_word(uint32_t address, uint32_t value)
 
 void write_long(uint32_t address, uint32_t value)
 {
+	#if 0
+	fprintf(stderr, "write 0x%08x: 0x%08x\n", address, value);
+	#endif
 	WRITE_LONG(ram, transform_address(address), value);
 }
 
 void system_call(uint8_t trapno)
 {
-	fatal("syscalls unimplemented");
+	cpu.cr &= ~(1<<28); /* reset summary overflow (for success) */
+	switch (cpu.gpr[0])
+	{
+		case 1: /* exit */
+			exit(cpu.gpr[3]);
+
+		case 4: /* write */
+		{
+			int fd = cpu.gpr[3];
+			uint32_t address = cpu.gpr[4];
+			uint32_t len = cpu.gpr[5];
+			void* ptr = ram + transform_address(address);
+			transform_address(address+len); /* bounds check */
+			cpu.gpr[4] = write(fd, ptr, len);
+			if (cpu.gpr[4] == -1)
+				goto error;
+			break;
+		}
+
+		case 126: /* sigprocmask */
+			cpu.gpr[4] = 0;
+			break;
+
+		error:
+			cpu.gpr[3] = errno;
+			cpu.cr |= (1<<28); /* set summary overflow (for failure) */
+			return;
+
+		default:
+			fatal("unimplemented system call %d", cpu.gpr[0]);
+	}
 }
 
 static void load_program(FILE* fd)
@@ -177,7 +214,9 @@ int main(int argc, char* argv[])
 
 	for (;;)
 	{
-		//dump_state(stderr);
+		#if 0
+		dump_state(stderr);
+		#endif
 		single_step();
 	}