[RFC PATCH 5/6] xen/riscv: Add early_printk

[Xie Xun <xiexun162534@xxxxxxxxx>]

Signed-off-by: Xie Xun <xiexun162534@xxxxxxxxx>
---
 xen/arch/riscv/Makefile                   |  1 +
 xen/arch/riscv/early_printk.c             | 48 +++++++++++++++++++++++
 xen/arch/riscv/include/asm/early_printk.h | 10 +++++
 3 files changed, 59 insertions(+)
 create mode 100644 xen/arch/riscv/early_printk.c
 create mode 100644 xen/arch/riscv/include/asm/early_printk.h

diff --git a/xen/arch/riscv/Makefile b/xen/arch/riscv/Makefile
index c61349818f..f9abc8401b 100644
--- a/xen/arch/riscv/Makefile
+++ b/xen/arch/riscv/Makefile
@@ -3,6 +3,7 @@ obj-y += lib/
 obj-y   += domctl.o
 obj-y   += domain.o
 obj-y   += delay.o
+obj-y   += early_printk.o
 obj-y   += guestcopy.o
 obj-y   += irq.o
 obj-y   += p2m.o
diff --git a/xen/arch/riscv/early_printk.c b/xen/arch/riscv/early_printk.c
new file mode 100644
index 0000000000..81d69add01
--- /dev/null
+++ b/xen/arch/riscv/early_printk.c
@@ -0,0 +1,48 @@
+/*
+ * RISC-V early printk using SBI
+ *
+ * Copyright (C) 2021 Bobby Eshleman <bobbyeshleman@xxxxxxxxx>
+ */
+#include <asm/sbi.h>
+#include <asm/early_printk.h>
+#include <xen/stdarg.h>
+#include <xen/lib.h>
+
+void _early_puts(const char *s, size_t nr)
+{
+    while ( nr-- > 0 )
+    {
+        if (*s == '\n')
+            sbi_console_putchar('\r');
+        sbi_console_putchar(*s);
+        s++;
+    }
+}
+
+static void vprintk_early(const char *prefix, const char *fmt, va_list args)
+{
+    char buf[128];
+    int sz;
+
+    early_puts(prefix);
+
+    sz = vscnprintf(buf, sizeof(buf), fmt, args);
+
+    if ( sz < 0 ) {
+        early_puts("(XEN) vprintk_early error\n");
+        return;
+    }
+
+    if ( sz == 0 )
+        return;
+
+    _early_puts(buf, sz);
+}
+
+void early_printk(const char *fmt, ...)
+{
+    va_list args;
+    va_start(args, fmt);
+    vprintk_early("(XEN) ", fmt, args);
+    va_end(args);
+}
diff --git a/xen/arch/riscv/include/asm/early_printk.h 
b/xen/arch/riscv/include/asm/early_printk.h
new file mode 100644
index 0000000000..0d9928b333
--- /dev/null
+++ b/xen/arch/riscv/include/asm/early_printk.h
@@ -0,0 +1,10 @@
+#ifndef __EARLY_PRINTK_H__
+#define __EARLY_PRINTK_H__
+
+#include <xen/string.h>
+
+#define early_puts(s) _early_puts((s), strlen((s)))
+void _early_puts(const char *s, size_t nr);
+void early_printk(const char *fmt, ...);
+
+#endif /* __EARLY_PRINTK_H__ */
-- 
2.30.2