powerpc/xmon: add command to dump OPAL msglog

Add the 'do' command to dump the OPAL msglog in xmon.
Signed-off-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
[mpe: Reduce the amount of ifdefery required]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/xmon/xmon.c

@@ -47,6 +47,9 @@
 #include <asm/debug.h>
 #include <asm/hw_breakpoint.h>
 
+#include <asm/opal.h>
+#include <asm/firmware.h>
+
 #ifdef CONFIG_PPC64
 #include <asm/hvcall.h>
 #include <asm/paca.h>
@@ -119,6 +122,16 @@ static void dump(void);
 static void prdump(unsigned long, long);
 static int ppc_inst_dump(unsigned long, long, int);
 static void dump_log_buf(void);
+
+#ifdef CONFIG_PPC_POWERNV
+static void dump_opal_msglog(void);
+#else
+static inline void dump_opal_msglog(void)
+{
+	printf("Machine is not running OPAL firmware.\n");
+}
+#endif
+
 static void backtrace(struct pt_regs *);
 static void excprint(struct pt_regs *);
 static void prregs(struct pt_regs *);
@@ -202,6 +215,10 @@ Commands:\n\
   df	dump float values\n\
   dd	dump double values\n\
   dl    dump the kernel log buffer\n"
+#ifdef CONFIG_PPC_POWERNV
+  "\
+  do    dump the OPAL message log\n"
+#endif
 #ifdef CONFIG_PPC64
   "\
   dp[#]	dump paca for current cpu, or cpu #\n\
@@ -2253,6 +2270,8 @@ dump(void)
 		last_cmd = "di\n";
 	} else if (c == 'l') {
 		dump_log_buf();
+	} else if (c == 'o') {
+		dump_opal_msglog();
 	} else if (c == 'r') {
 		scanhex(&ndump);
 		if (ndump == 0)
@@ -2395,6 +2414,45 @@ dump_log_buf(void)
 	catch_memory_errors = 0;
 }
 
+#ifdef CONFIG_PPC_POWERNV
+static void dump_opal_msglog(void)
+{
+	unsigned char buf[128];
+	ssize_t res;
+	loff_t pos = 0;
+
+	if (!firmware_has_feature(FW_FEATURE_OPAL)) {
+		printf("Machine is not running OPAL firmware.\n");
+		return;
+	}
+
+	if (setjmp(bus_error_jmp) != 0) {
+		printf("Error dumping OPAL msglog!\n");
+		return;
+	}
+
+	catch_memory_errors = 1;
+	sync();
+
+	xmon_start_pagination();
+	while ((res = opal_msglog_copy(buf, pos, sizeof(buf) - 1))) {
+		if (res < 0) {
+			printf("Error dumping OPAL msglog! Error: %zd\n", res);
+			break;
+		}
+		buf[res] = '\0';
+		printf("%s", buf);
+		pos += res;
+	}
+	xmon_end_pagination();
+
+	sync();
+	/* wait a little while to see if we get a machine check */
+	__delay(200);
+	catch_memory_errors = 0;
+}
+#endif
+
 /*
  * Memory operations - move, set, print differences
  */