[PATCH 5/5] x86, KASLR: Warn when KASLR is disabled

[Kees Cook]

If KASLR is built in but not available at run-time (either due to the
current conflict with hibernation, command-line request, or e820 parsing
failures), announce the state explicitly. To support this, a new "warn"
function is created, based on the existing "error" function.

Suggested-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 arch/x86/boot/compressed/kaslr.c |  6 +++---
 arch/x86/boot/compressed/misc.c  | 12 +++++++++---
 arch/x86/boot/compressed/misc.h  |  1 +
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 3ad71a0afa24..8741a6d83bfe 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -314,12 +314,12 @@ unsigned char *choose_random_location(unsigned char 
*input,
 
 #ifdef CONFIG_HIBERNATION
        if (!cmdline_find_option_bool("kaslr")) {
-               debug_putstr("KASLR disabled by default...\n");
+               warn("KASLR disabled: 'kaslr' not on cmdline (hibernation 
selected).");
                goto out;
        }
 #else
        if (cmdline_find_option_bool("nokaslr")) {
-               debug_putstr("KASLR disabled by cmdline...\n");
+               warn("KASLR disabled: 'nokaslr' on cmdline.");
                goto out;
        }
 #endif
@@ -333,7 +333,7 @@ unsigned char *choose_random_location(unsigned char *input,
        /* Walk e820 and find a random address. */
        random_addr = find_random_addr(choice, output_size);
        if (!random_addr) {
-               debug_putstr("KASLR could not find suitable E820 region...\n");
+               warn("KASLR disabled: could not find suitable E820 region!");
                goto out;
        }
 
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index eacc855ae08e..c57d785ff955 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -166,11 +166,17 @@ void __puthex(unsigned long value)
        }
 }
 
-static void error(char *x)
+void warn(char *m)
 {
        error_putstr("\n\n");
-       error_putstr(x);
-       error_putstr("\n\n -- System halted");
+       error_putstr(m);
+       error_putstr("\n\n");
+}
+
+static void error(char *m)
+{
+       warn(m);
+       error_putstr(" -- System halted");
 
        while (1)
                asm("hlt");
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 9887e0d4aaeb..e75f6cf9caaf 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -35,6 +35,7 @@ extern memptr free_mem_end_ptr;
 extern struct boot_params *boot_params;
 void __putstr(const char *s);
 void __puthex(unsigned long value);
+void warn(char *m);
 #define error_putstr(__x)  __putstr(__x)
 #define error_puthex(__x)  __puthex(__x)
 
-- 
2.6.3