linux-kernel - [PATCH] x86, boot: add hex output for debugging

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Message-ID: <20141031162037.GA26233@www.outflux.net>
Date:	Fri, 31 Oct 2014 09:20:37 -0700
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Vivek Goyal <vgoyal@...hat.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Junjie Mao <eternal.n08@...il.com>
Subject: [PATCH] x86, boot: add hex output for debugging

This is useful for reporting various addresses or other values while
debugging early boot.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/x86/boot/compressed/misc.c | 19 +++++++++++++++++++
 arch/x86/boot/compressed/misc.h |  5 +++++
 2 files changed, 24 insertions(+)

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 30dd59a9f0b4..1b105664f720 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -220,6 +220,25 @@ void __putstr(const char *s)
 	outb(0xff & (pos >> 1), vidport+1);
 }
 
+void __puthex(unsigned long value)
+{
+	char alpha[2] = "0";
+	int bits;
+	unsigned char byte;
+
+	__putstr("0x");
+	for (bits = sizeof(value) * 8 - 4; bits >= 0; bits -= 4) {
+		unsigned long digit = (value >> bits) & 0xf;
+
+		if (digit < 0xA)
+			alpha[0] = '0' + digit;
+		else
+			alpha[0] = 'a' + (digit - 0xA);
+
+		__putstr(alpha);
+	}
+}
+
 static void error(char *x)
 {
 	error_putstr("\n\n");
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 24e3e569a13c..6056d339fb17 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -34,16 +34,21 @@ extern memptr free_mem_ptr;
 extern memptr free_mem_end_ptr;
 extern struct boot_params *real_mode;		/* Pointer to real-mode data */
 void __putstr(const char *s);
+void __puthex(unsigned long value);
 #define error_putstr(__x)  __putstr(__x)
+#define error_puthex(__x)  __puthex(__x)
 
 #ifdef CONFIG_X86_VERBOSE_BOOTUP
 
 #define debug_putstr(__x)  __putstr(__x)
+#define debug_puthex(__x)  __puthex(__x)
 
 #else
 
 static inline void debug_putstr(const char *s)
 { }
+static inline void debug_puthex(const char *s)
+{ }
 
 #endif
 
-- 
1.9.1


-- 
Kees Cook
Chrome OS Security
--
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