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Subject[PATCH v6 08/11] x86/KASLR: Clarify purpose of each get_random_long
Date
KASLR will be calling get_random_long() twice, but the debug output
won't distinguishing between them. This patch adds a report on when it
is fetching the physical vs virtual address. With this, once the virtual
offset is separate, the report changes from:

KASLR using RDTSC...
KASLR using RDTSC...

into:

Physical KASLR using RDTSC...
Virtual KASLR using RDTSC...

Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/x86/boot/compressed/kaslr.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 05f564b6c70e..3672c7388e5a 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -72,7 +72,7 @@ static unsigned long get_random_boot(void)
return hash;
}

-static unsigned long get_random_long(void)
+static unsigned long get_random_long(const char *purpose)
{
#ifdef CONFIG_X86_64
const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
@@ -82,7 +82,8 @@ static unsigned long get_random_long(void)
unsigned long raw, random = get_random_boot();
bool use_i8254 = true;

- debug_putstr("KASLR using");
+ debug_putstr(purpose);
+ debug_putstr(" KASLR using");

if (has_cpuflag(X86_FEATURE_RDRAND)) {
debug_putstr(" RDRAND");
@@ -332,7 +333,7 @@ static unsigned long slots_fetch_random(void)
if (slot_max == 0)
return 0;

- return slots[get_random_long() % slot_max];
+ return slots[get_random_long("Physical") % slot_max];
}

static void process_e820_entry(struct e820entry *entry,
@@ -420,7 +421,7 @@ static unsigned long find_random_virt_addr(unsigned long minimum,
slots = (KERNEL_IMAGE_SIZE - minimum - image_size) /
CONFIG_PHYSICAL_ALIGN + 1;

- random_addr = get_random_long() % slots;
+ random_addr = get_random_long("Virtual") % slots;

return random_addr * CONFIG_PHYSICAL_ALIGN + minimum;
}
--
2.6.3
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