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Message-Id: <1460997735-24785-2-git-send-email-keescook@chromium.org>
Date: Mon, 18 Apr 2016 09:42:10 -0700
From: Kees Cook <keescook@...omium.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: Kees Cook <keescook@...omium.org>, Yinghai Lu <yinghai@...nel.org>,
Baoquan He <bhe@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
"H.J. Lu" <hjl.tools@...il.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Borislav Petkov <bp@...e.de>,
Andy Lutomirski <luto@...nel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 1/6] x86, KASLR: rename aslr.c to kaslr.c
In order to avoid confusion over what this file provides, rename it to
kaslr.c since it is used exclusively for the kernel ASLR, not userspace
ASLR.
Suggested-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
arch/x86/boot/compressed/Makefile | 2 +-
arch/x86/boot/compressed/aslr.c | 339 --------------------------------------
arch/x86/boot/compressed/kaslr.c | 339 ++++++++++++++++++++++++++++++++++++++
arch/x86/boot/compressed/misc.h | 2 +-
4 files changed, 341 insertions(+), 341 deletions(-)
delete mode 100644 arch/x86/boot/compressed/aslr.c
create mode 100644 arch/x86/boot/compressed/kaslr.c
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 8774cb23064f..542c92f5ca4f 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -62,7 +62,7 @@ vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \
$(obj)/piggy.o $(obj)/cpuflags.o
vmlinux-objs-$(CONFIG_EARLY_PRINTK) += $(obj)/early_serial_console.o
-vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/aslr.o
+vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/kaslr.o
$(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone
diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
deleted file mode 100644
index 6a9b96b4624d..000000000000
--- a/arch/x86/boot/compressed/aslr.c
+++ /dev/null
@@ -1,339 +0,0 @@
-#include "misc.h"
-
-#include <asm/msr.h>
-#include <asm/archrandom.h>
-#include <asm/e820.h>
-
-#include <generated/compile.h>
-#include <linux/module.h>
-#include <linux/uts.h>
-#include <linux/utsname.h>
-#include <generated/utsrelease.h>
-
-/* Simplified build-specific string for starting entropy. */
-static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
- LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION;
-
-#define I8254_PORT_CONTROL 0x43
-#define I8254_PORT_COUNTER0 0x40
-#define I8254_CMD_READBACK 0xC0
-#define I8254_SELECT_COUNTER0 0x02
-#define I8254_STATUS_NOTREADY 0x40
-static inline u16 i8254(void)
-{
- u16 status, timer;
-
- do {
- outb(I8254_PORT_CONTROL,
- I8254_CMD_READBACK | I8254_SELECT_COUNTER0);
- status = inb(I8254_PORT_COUNTER0);
- timer = inb(I8254_PORT_COUNTER0);
- timer |= inb(I8254_PORT_COUNTER0) << 8;
- } while (status & I8254_STATUS_NOTREADY);
-
- return timer;
-}
-
-static unsigned long rotate_xor(unsigned long hash, const void *area,
- size_t size)
-{
- size_t i;
- unsigned long *ptr = (unsigned long *)area;
-
- for (i = 0; i < size / sizeof(hash); i++) {
- /* Rotate by odd number of bits and XOR. */
- hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7);
- hash ^= ptr[i];
- }
-
- return hash;
-}
-
-/* Attempt to create a simple but unpredictable starting entropy. */
-static unsigned long get_random_boot(void)
-{
- unsigned long hash = 0;
-
- hash = rotate_xor(hash, build_str, sizeof(build_str));
- hash = rotate_xor(hash, real_mode, sizeof(*real_mode));
-
- return hash;
-}
-
-static unsigned long get_random_long(void)
-{
-#ifdef CONFIG_X86_64
- const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
-#else
- const unsigned long mix_const = 0x3f39e593UL;
-#endif
- unsigned long raw, random = get_random_boot();
- bool use_i8254 = true;
-
- debug_putstr("KASLR using");
-
- if (has_cpuflag(X86_FEATURE_RDRAND)) {
- debug_putstr(" RDRAND");
- if (rdrand_long(&raw)) {
- random ^= raw;
- use_i8254 = false;
- }
- }
-
- if (has_cpuflag(X86_FEATURE_TSC)) {
- debug_putstr(" RDTSC");
- raw = rdtsc();
-
- random ^= raw;
- use_i8254 = false;
- }
-
- if (use_i8254) {
- debug_putstr(" i8254");
- random ^= i8254();
- }
-
- /* Circular multiply for better bit diffusion */
- asm("mul %3"
- : "=a" (random), "=d" (raw)
- : "a" (random), "rm" (mix_const));
- random += raw;
-
- debug_putstr("...\n");
-
- return random;
-}
-
-struct mem_vector {
- unsigned long start;
- unsigned long size;
-};
-
-#define MEM_AVOID_MAX 5
-static struct mem_vector mem_avoid[MEM_AVOID_MAX];
-
-static bool mem_contains(struct mem_vector *region, struct mem_vector *item)
-{
- /* Item at least partially before region. */
- if (item->start < region->start)
- return false;
- /* Item at least partially after region. */
- if (item->start + item->size > region->start + region->size)
- return false;
- return true;
-}
-
-static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
-{
- /* Item one is entirely before item two. */
- if (one->start + one->size <= two->start)
- return false;
- /* Item one is entirely after item two. */
- if (one->start >= two->start + two->size)
- return false;
- return true;
-}
-
-static void mem_avoid_init(unsigned long input, unsigned long input_size,
- unsigned long output, unsigned long output_size)
-{
- u64 initrd_start, initrd_size;
- u64 cmd_line, cmd_line_size;
- unsigned long unsafe, unsafe_len;
- char *ptr;
-
- /*
- * Avoid the region that is unsafe to overlap during
- * decompression (see calculations at top of misc.c).
- */
- unsafe_len = (output_size >> 12) + 32768 + 18;
- unsafe = (unsigned long)input + input_size - unsafe_len;
- mem_avoid[0].start = unsafe;
- mem_avoid[0].size = unsafe_len;
-
- /* Avoid initrd. */
- initrd_start = (u64)real_mode->ext_ramdisk_image << 32;
- initrd_start |= real_mode->hdr.ramdisk_image;
- initrd_size = (u64)real_mode->ext_ramdisk_size << 32;
- initrd_size |= real_mode->hdr.ramdisk_size;
- mem_avoid[1].start = initrd_start;
- mem_avoid[1].size = initrd_size;
-
- /* Avoid kernel command line. */
- cmd_line = (u64)real_mode->ext_cmd_line_ptr << 32;
- cmd_line |= real_mode->hdr.cmd_line_ptr;
- /* Calculate size of cmd_line. */
- ptr = (char *)(unsigned long)cmd_line;
- for (cmd_line_size = 0; ptr[cmd_line_size++]; )
- ;
- mem_avoid[2].start = cmd_line;
- mem_avoid[2].size = cmd_line_size;
-
- /* Avoid heap memory. */
- mem_avoid[3].start = (unsigned long)free_mem_ptr;
- mem_avoid[3].size = BOOT_HEAP_SIZE;
-
- /* Avoid stack memory. */
- mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
- mem_avoid[4].size = BOOT_STACK_SIZE;
-}
-
-/* Does this memory vector overlap a known avoided area? */
-static bool mem_avoid_overlap(struct mem_vector *img)
-{
- int i;
- struct setup_data *ptr;
-
- for (i = 0; i < MEM_AVOID_MAX; i++) {
- if (mem_overlaps(img, &mem_avoid[i]))
- return true;
- }
-
- /* Avoid all entries in the setup_data linked list. */
- ptr = (struct setup_data *)(unsigned long)real_mode->hdr.setup_data;
- while (ptr) {
- struct mem_vector avoid;
-
- avoid.start = (unsigned long)ptr;
- avoid.size = sizeof(*ptr) + ptr->len;
-
- if (mem_overlaps(img, &avoid))
- return true;
-
- ptr = (struct setup_data *)(unsigned long)ptr->next;
- }
-
- return false;
-}
-
-static unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
- CONFIG_PHYSICAL_ALIGN];
-static unsigned long slot_max;
-
-static void slots_append(unsigned long addr)
-{
- /* Overflowing the slots list should be impossible. */
- if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
- CONFIG_PHYSICAL_ALIGN)
- return;
-
- slots[slot_max++] = addr;
-}
-
-static unsigned long slots_fetch_random(void)
-{
- /* Handle case of no slots stored. */
- if (slot_max == 0)
- return 0;
-
- return slots[get_random_long() % slot_max];
-}
-
-static void process_e820_entry(struct e820entry *entry,
- unsigned long minimum,
- unsigned long image_size)
-{
- struct mem_vector region, img;
-
- /* Skip non-RAM entries. */
- if (entry->type != E820_RAM)
- return;
-
- /* Ignore entries entirely above our maximum. */
- if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
- return;
-
- /* Ignore entries entirely below our minimum. */
- if (entry->addr + entry->size < minimum)
- return;
-
- region.start = entry->addr;
- region.size = entry->size;
-
- /* Potentially raise address to minimum location. */
- if (region.start < minimum)
- region.start = minimum;
-
- /* Potentially raise address to meet alignment requirements. */
- region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
-
- /* Did we raise the address above the bounds of this e820 region? */
- if (region.start > entry->addr + entry->size)
- return;
-
- /* Reduce size by any delta from the original address. */
- region.size -= region.start - entry->addr;
-
- /* Reduce maximum size to fit end of image within maximum limit. */
- if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
- region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start;
-
- /* Walk each aligned slot and check for avoided areas. */
- for (img.start = region.start, img.size = image_size ;
- mem_contains(®ion, &img) ;
- img.start += CONFIG_PHYSICAL_ALIGN) {
- if (mem_avoid_overlap(&img))
- continue;
- slots_append(img.start);
- }
-}
-
-static unsigned long find_random_addr(unsigned long minimum,
- unsigned long size)
-{
- int i;
- unsigned long addr;
-
- /* Make sure minimum is aligned. */
- minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
-
- /* Verify potential e820 positions, appending to slots list. */
- for (i = 0; i < real_mode->e820_entries; i++) {
- process_e820_entry(&real_mode->e820_map[i], minimum, size);
- }
-
- return slots_fetch_random();
-}
-
-unsigned char *choose_kernel_location(struct boot_params *boot_params,
- unsigned char *input,
- unsigned long input_size,
- unsigned char *output,
- unsigned long output_size)
-{
- unsigned long choice = (unsigned long)output;
- unsigned long random;
-
-#ifdef CONFIG_HIBERNATION
- if (!cmdline_find_option_bool("kaslr")) {
- debug_putstr("KASLR disabled by default...\n");
- goto out;
- }
-#else
- if (cmdline_find_option_bool("nokaslr")) {
- debug_putstr("KASLR disabled by cmdline...\n");
- goto out;
- }
-#endif
-
- boot_params->hdr.loadflags |= KASLR_FLAG;
-
- /* Record the various known unsafe memory ranges. */
- mem_avoid_init((unsigned long)input, input_size,
- (unsigned long)output, output_size);
-
- /* Walk e820 and find a random address. */
- random = find_random_addr(choice, output_size);
- if (!random) {
- debug_putstr("KASLR could not find suitable E820 region...\n");
- goto out;
- }
-
- /* Always enforce the minimum. */
- if (random < choice)
- goto out;
-
- choice = random;
-out:
- return (unsigned char *)choice;
-}
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
new file mode 100644
index 000000000000..6a9b96b4624d
--- /dev/null
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -0,0 +1,339 @@
+#include "misc.h"
+
+#include <asm/msr.h>
+#include <asm/archrandom.h>
+#include <asm/e820.h>
+
+#include <generated/compile.h>
+#include <linux/module.h>
+#include <linux/uts.h>
+#include <linux/utsname.h>
+#include <generated/utsrelease.h>
+
+/* Simplified build-specific string for starting entropy. */
+static const char build_str[] = UTS_RELEASE " (" LINUX_COMPILE_BY "@"
+ LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION;
+
+#define I8254_PORT_CONTROL 0x43
+#define I8254_PORT_COUNTER0 0x40
+#define I8254_CMD_READBACK 0xC0
+#define I8254_SELECT_COUNTER0 0x02
+#define I8254_STATUS_NOTREADY 0x40
+static inline u16 i8254(void)
+{
+ u16 status, timer;
+
+ do {
+ outb(I8254_PORT_CONTROL,
+ I8254_CMD_READBACK | I8254_SELECT_COUNTER0);
+ status = inb(I8254_PORT_COUNTER0);
+ timer = inb(I8254_PORT_COUNTER0);
+ timer |= inb(I8254_PORT_COUNTER0) << 8;
+ } while (status & I8254_STATUS_NOTREADY);
+
+ return timer;
+}
+
+static unsigned long rotate_xor(unsigned long hash, const void *area,
+ size_t size)
+{
+ size_t i;
+ unsigned long *ptr = (unsigned long *)area;
+
+ for (i = 0; i < size / sizeof(hash); i++) {
+ /* Rotate by odd number of bits and XOR. */
+ hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7);
+ hash ^= ptr[i];
+ }
+
+ return hash;
+}
+
+/* Attempt to create a simple but unpredictable starting entropy. */
+static unsigned long get_random_boot(void)
+{
+ unsigned long hash = 0;
+
+ hash = rotate_xor(hash, build_str, sizeof(build_str));
+ hash = rotate_xor(hash, real_mode, sizeof(*real_mode));
+
+ return hash;
+}
+
+static unsigned long get_random_long(void)
+{
+#ifdef CONFIG_X86_64
+ const unsigned long mix_const = 0x5d6008cbf3848dd3UL;
+#else
+ const unsigned long mix_const = 0x3f39e593UL;
+#endif
+ unsigned long raw, random = get_random_boot();
+ bool use_i8254 = true;
+
+ debug_putstr("KASLR using");
+
+ if (has_cpuflag(X86_FEATURE_RDRAND)) {
+ debug_putstr(" RDRAND");
+ if (rdrand_long(&raw)) {
+ random ^= raw;
+ use_i8254 = false;
+ }
+ }
+
+ if (has_cpuflag(X86_FEATURE_TSC)) {
+ debug_putstr(" RDTSC");
+ raw = rdtsc();
+
+ random ^= raw;
+ use_i8254 = false;
+ }
+
+ if (use_i8254) {
+ debug_putstr(" i8254");
+ random ^= i8254();
+ }
+
+ /* Circular multiply for better bit diffusion */
+ asm("mul %3"
+ : "=a" (random), "=d" (raw)
+ : "a" (random), "rm" (mix_const));
+ random += raw;
+
+ debug_putstr("...\n");
+
+ return random;
+}
+
+struct mem_vector {
+ unsigned long start;
+ unsigned long size;
+};
+
+#define MEM_AVOID_MAX 5
+static struct mem_vector mem_avoid[MEM_AVOID_MAX];
+
+static bool mem_contains(struct mem_vector *region, struct mem_vector *item)
+{
+ /* Item at least partially before region. */
+ if (item->start < region->start)
+ return false;
+ /* Item at least partially after region. */
+ if (item->start + item->size > region->start + region->size)
+ return false;
+ return true;
+}
+
+static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
+{
+ /* Item one is entirely before item two. */
+ if (one->start + one->size <= two->start)
+ return false;
+ /* Item one is entirely after item two. */
+ if (one->start >= two->start + two->size)
+ return false;
+ return true;
+}
+
+static void mem_avoid_init(unsigned long input, unsigned long input_size,
+ unsigned long output, unsigned long output_size)
+{
+ u64 initrd_start, initrd_size;
+ u64 cmd_line, cmd_line_size;
+ unsigned long unsafe, unsafe_len;
+ char *ptr;
+
+ /*
+ * Avoid the region that is unsafe to overlap during
+ * decompression (see calculations at top of misc.c).
+ */
+ unsafe_len = (output_size >> 12) + 32768 + 18;
+ unsafe = (unsigned long)input + input_size - unsafe_len;
+ mem_avoid[0].start = unsafe;
+ mem_avoid[0].size = unsafe_len;
+
+ /* Avoid initrd. */
+ initrd_start = (u64)real_mode->ext_ramdisk_image << 32;
+ initrd_start |= real_mode->hdr.ramdisk_image;
+ initrd_size = (u64)real_mode->ext_ramdisk_size << 32;
+ initrd_size |= real_mode->hdr.ramdisk_size;
+ mem_avoid[1].start = initrd_start;
+ mem_avoid[1].size = initrd_size;
+
+ /* Avoid kernel command line. */
+ cmd_line = (u64)real_mode->ext_cmd_line_ptr << 32;
+ cmd_line |= real_mode->hdr.cmd_line_ptr;
+ /* Calculate size of cmd_line. */
+ ptr = (char *)(unsigned long)cmd_line;
+ for (cmd_line_size = 0; ptr[cmd_line_size++]; )
+ ;
+ mem_avoid[2].start = cmd_line;
+ mem_avoid[2].size = cmd_line_size;
+
+ /* Avoid heap memory. */
+ mem_avoid[3].start = (unsigned long)free_mem_ptr;
+ mem_avoid[3].size = BOOT_HEAP_SIZE;
+
+ /* Avoid stack memory. */
+ mem_avoid[4].start = (unsigned long)free_mem_end_ptr;
+ mem_avoid[4].size = BOOT_STACK_SIZE;
+}
+
+/* Does this memory vector overlap a known avoided area? */
+static bool mem_avoid_overlap(struct mem_vector *img)
+{
+ int i;
+ struct setup_data *ptr;
+
+ for (i = 0; i < MEM_AVOID_MAX; i++) {
+ if (mem_overlaps(img, &mem_avoid[i]))
+ return true;
+ }
+
+ /* Avoid all entries in the setup_data linked list. */
+ ptr = (struct setup_data *)(unsigned long)real_mode->hdr.setup_data;
+ while (ptr) {
+ struct mem_vector avoid;
+
+ avoid.start = (unsigned long)ptr;
+ avoid.size = sizeof(*ptr) + ptr->len;
+
+ if (mem_overlaps(img, &avoid))
+ return true;
+
+ ptr = (struct setup_data *)(unsigned long)ptr->next;
+ }
+
+ return false;
+}
+
+static unsigned long slots[CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
+ CONFIG_PHYSICAL_ALIGN];
+static unsigned long slot_max;
+
+static void slots_append(unsigned long addr)
+{
+ /* Overflowing the slots list should be impossible. */
+ if (slot_max >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET /
+ CONFIG_PHYSICAL_ALIGN)
+ return;
+
+ slots[slot_max++] = addr;
+}
+
+static unsigned long slots_fetch_random(void)
+{
+ /* Handle case of no slots stored. */
+ if (slot_max == 0)
+ return 0;
+
+ return slots[get_random_long() % slot_max];
+}
+
+static void process_e820_entry(struct e820entry *entry,
+ unsigned long minimum,
+ unsigned long image_size)
+{
+ struct mem_vector region, img;
+
+ /* Skip non-RAM entries. */
+ if (entry->type != E820_RAM)
+ return;
+
+ /* Ignore entries entirely above our maximum. */
+ if (entry->addr >= CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
+ return;
+
+ /* Ignore entries entirely below our minimum. */
+ if (entry->addr + entry->size < minimum)
+ return;
+
+ region.start = entry->addr;
+ region.size = entry->size;
+
+ /* Potentially raise address to minimum location. */
+ if (region.start < minimum)
+ region.start = minimum;
+
+ /* Potentially raise address to meet alignment requirements. */
+ region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN);
+
+ /* Did we raise the address above the bounds of this e820 region? */
+ if (region.start > entry->addr + entry->size)
+ return;
+
+ /* Reduce size by any delta from the original address. */
+ region.size -= region.start - entry->addr;
+
+ /* Reduce maximum size to fit end of image within maximum limit. */
+ if (region.start + region.size > CONFIG_RANDOMIZE_BASE_MAX_OFFSET)
+ region.size = CONFIG_RANDOMIZE_BASE_MAX_OFFSET - region.start;
+
+ /* Walk each aligned slot and check for avoided areas. */
+ for (img.start = region.start, img.size = image_size ;
+ mem_contains(®ion, &img) ;
+ img.start += CONFIG_PHYSICAL_ALIGN) {
+ if (mem_avoid_overlap(&img))
+ continue;
+ slots_append(img.start);
+ }
+}
+
+static unsigned long find_random_addr(unsigned long minimum,
+ unsigned long size)
+{
+ int i;
+ unsigned long addr;
+
+ /* Make sure minimum is aligned. */
+ minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
+
+ /* Verify potential e820 positions, appending to slots list. */
+ for (i = 0; i < real_mode->e820_entries; i++) {
+ process_e820_entry(&real_mode->e820_map[i], minimum, size);
+ }
+
+ return slots_fetch_random();
+}
+
+unsigned char *choose_kernel_location(struct boot_params *boot_params,
+ unsigned char *input,
+ unsigned long input_size,
+ unsigned char *output,
+ unsigned long output_size)
+{
+ unsigned long choice = (unsigned long)output;
+ unsigned long random;
+
+#ifdef CONFIG_HIBERNATION
+ if (!cmdline_find_option_bool("kaslr")) {
+ debug_putstr("KASLR disabled by default...\n");
+ goto out;
+ }
+#else
+ if (cmdline_find_option_bool("nokaslr")) {
+ debug_putstr("KASLR disabled by cmdline...\n");
+ goto out;
+ }
+#endif
+
+ boot_params->hdr.loadflags |= KASLR_FLAG;
+
+ /* Record the various known unsafe memory ranges. */
+ mem_avoid_init((unsigned long)input, input_size,
+ (unsigned long)output, output_size);
+
+ /* Walk e820 and find a random address. */
+ random = find_random_addr(choice, output_size);
+ if (!random) {
+ debug_putstr("KASLR could not find suitable E820 region...\n");
+ goto out;
+ }
+
+ /* Always enforce the minimum. */
+ if (random < choice)
+ goto out;
+
+ choice = random;
+out:
+ return (unsigned char *)choice;
+}
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 3783dc3e10b3..a8c4e087e14d 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -66,7 +66,7 @@ int cmdline_find_option_bool(const char *option);
#if CONFIG_RANDOMIZE_BASE
-/* aslr.c */
+/* kaslr.c */
unsigned char *choose_kernel_location(struct boot_params *boot_params,
unsigned char *input,
unsigned long input_size,
--
2.6.3
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