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

From: Kees Cook
Date: Mon Jul 06 2015 - 19:07:08 EST


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@xxxxxxxxxxxx>
---
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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/