From 723428bebe3105ad3c3406e416402d1831b482c4 Mon Sep 17 00:00:00 2001
From: Andrew Lee <alee14498@protonmail.com>
Date: Sun, 15 Aug 2021 00:16:45 -0400
Subject: Inital commit

---
 linux/kernel/printk.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 linux/kernel/printk.c

(limited to 'linux/kernel/printk.c')

diff --git a/linux/kernel/printk.c b/linux/kernel/printk.c
new file mode 100644
index 0000000..7a70dc3
--- /dev/null
+++ b/linux/kernel/printk.c
@@ -0,0 +1,33 @@
+/*
+ * When in kernel-mode, we cannot use printf, as fs is liable to
+ * point to 'interesting' things. Make a printf with fs-saving, and
+ * all is well.
+ */
+#include <stdarg.h>
+#include <stddef.h>
+
+#include <linux/kernel.h>
+
+static char buf[1024];
+
+int printk(const char *fmt, ...)
+{
+	va_list args;
+	int i;
+
+	va_start(args, fmt);
+	i=vsprintf(buf,fmt,args);
+	va_end(args);
+	__asm__("push %%fs\n\t"
+		"push %%ds\n\t"
+		"pop %%fs\n\t"
+		"pushl %0\n\t"
+		"pushl $_buf\n\t"
+		"pushl $0\n\t"
+		"call _tty_write\n\t"
+		"addl $8,%%esp\n\t"
+		"popl %0\n\t"
+		"pop %%fs"
+		::"r" (i):"ax","cx","dx");
+	return i;
+}
-- 
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