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

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Date:	Mon, 6 Jul 2015 16:06:20 -0700
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	Josh Triplett <josh@...htriplett.org>,
	Joe Perches <joe@...ches.com>, Yinghai Lu <yinghai@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Vivek Goyal <vgoyal@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Borislav Petkov <bp@...e.de>,
	Junjie Mao <eternal.n08@...il.com>,
	Jiri Kosina <jkosina@...e.cz>, Jan Beulich <JBeulich@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrey Ryabinin <a.ryabinin@...sung.com>
Subject: [PATCH][RESEND] x86, boot: add hex output for debugging

This is useful for reporting various addresses or other values while
debugging early boot, for example, the recent kernel image size vs
kernel run size. For example, when CONFIG_X86_VERBOSE_BOOTUP is set,
this is now visible at boot time:

	early console in setup code
	early console in decompress_kernel
	input_data: 0x0000000001e1526e
	input_len: 0x0000000000732236
	output: 0x0000000001000000
	output_len: 0x0000000001535640
	run_size: 0x00000000021fb000
	KASLR using RDTSC...

Signed-off-by: Kees Cook <keescook@...omium.org>
---
There was some discussion around this patch when I sent it before, but
ultimately, concensus seemed to be that it was fine as-is (e.g. full printf
and macros are over-kill, reduction of print infrastructure is a separate
issue). Thoughts?
---
 arch/x86/boot/compressed/misc.c | 24 ++++++++++++++++++++++++
 arch/x86/boot/compressed/misc.h | 11 +++++++++++
 2 files changed, 35 insertions(+)

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index a107b935e22f..f63797942bb5 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -220,6 +220,23 @@ void __putstr(const char *s)
 	outb(0xff & (pos >> 1), vidport+1);
 }
 
+void __puthex(unsigned long value)
+{
+	char alpha[2] = "0";
+	int bits;
+
+	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");
@@ -399,6 +416,13 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
 	free_mem_ptr     = heap;	/* Heap */
 	free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
 
+	/* Report initial kernel position details. */
+	debug_putaddr(input_data);
+	debug_putaddr(input_len);
+	debug_putaddr(output);
+	debug_putaddr(output_len);
+	debug_putaddr(run_size);
+
 	/*
 	 * The memory hole needed for the kernel is the larger of either
 	 * the entire decompressed kernel plus relocation table, or the
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 805d25ca5f1d..3783dc3e10b3 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -34,16 +34,27 @@ 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)
+#define debug_putaddr(__x) { \
+		debug_putstr(#__x ": 0x"); \
+		debug_puthex((unsigned long)(__x)); \
+		debug_putstr("\n"); \
+	}
 
 #else
 
 static inline void debug_putstr(const char *s)
 { }
+static inline void debug_puthex(const char *s)
+{ }
+#define debug_putaddr(x) /* */
 
 #endif
 
-- 
1.9.1


-- 
Kees Cook
Chrome OS Security
--
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