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Date: Mon, 9 May 2016 13:22:09 -0700
From: Kees Cook <keescook@...omium.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
Borislav Petkov <bp@...e.de>,
Baoquan He <bhe@...hat.com>,
Yinghai Lu <yinghai@...nel.org>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Borislav Petkov <bp@...en8.de>,
Vivek Goyal <vgoyal@...hat.com>,
Andy Lutomirski <luto@...nel.org>,
lasse.collin@...aani.org,
Andrew Morton <akpm@...ux-foundation.org>,
Dave Young <dyoung@...hat.com>,
kernel-hardening@...ts.openwall.com,
LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH v7 6/9] x86/KASLR: Clarify purpose of each get_random_long()
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@...omium.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 82d00282df3f..c4b1e4b05cb6 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");
@@ -365,7 +366,7 @@ 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,
@@ -453,7 +454,7 @@ 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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