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[PATCH 0/6] x86, boot: clean up KASLR code

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  [PATCH 0/6] x86, boot: clean up KASLR code Kees Cook <keescook@chromium.org> - 2016-04-18 18:50 +0200
    [PATCH 1/6] x86, KASLR: rename aslr.c to kaslr.c Kees Cook <keescook@chromium.org> - 2016-04-18 18:50 +0200
      [tip:x86/boot] x86/KASLR: Rename aslr.c to kaslr.c tip-bot for Kees Cook <tipbot@zytor.com> - 2016-04-19 11:40 +0200
    [PATCH 5/6] x86, KASLR: Clarify purpose of kaslr.c Kees Cook <keescook@chromium.org> - 2016-04-18 18:50 +0200
      [tip:x86/boot] x86/KASLR: Clarify purpose of kaslr.c tip-bot for Kees Cook <tipbot@zytor.com> - 2016-04-19 11:40 +0200
    [PATCH 4/6] x86, boot: Clarify purpose of functions in misc.c Kees Cook <keescook@chromium.org> - 2016-04-18 18:50 +0200
      [tip:x86/boot] x86/boot: Clarify purpose of functions in misc.c tip-bot for Kees Cook <tipbot@zytor.com> - 2016-04-19 11:40 +0200
    [PATCH 6/6] x86, KASLR: Rename "random" to "random_addr" Kees Cook <keescook@chromium.org> - 2016-04-18 18:50 +0200
      [tip:x86/boot] x86/KASLR: Rename "random" to "random_addr" tip-bot for Kees Cook <tipbot@zytor.com> - 2016-04-19 11:40 +0200
    Re: [PATCH 0/6] x86, boot: clean up KASLR code Ingo Molnar <mingo@kernel.org> - 2016-04-19 10:40 +0200

#1381900 — [PATCH 0/6] x86, boot: clean up KASLR code

In order to make improvements to KASLR behavior, it has been suggested
that the code should be cleaned up a bit first. This is the start of
those changes. Since there are no stand-alone bug fixes in the later
patches, I will begin here. First with a rename followed by variable
name changes and comment improvements.

This is the first wave...

-Kees

[toc] | [next] | [standalone]

#1381902 — [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@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.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(&region, &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(&region, &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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#1382327 — [tip:x86/boot] x86/KASLR: Rename aslr.c to kaslr.c

Commit-ID:  9b238748cb6e9fadab0e761f6d30ba311b4ac470
Gitweb:     http://git.kernel.org/tip/9b238748cb6e9fadab0e761f6d30ba311b4ac470
Author:     Kees Cook <keescook@chromium.org>
AuthorDate: Mon, 18 Apr 2016 09:42:10 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 19 Apr 2016 10:30:50 +0200

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@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: H.J. Lu <hjl.tools@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1460997735-24785-2-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/boot/compressed/Makefile            | 2 +-
 arch/x86/boot/compressed/{aslr.c => kaslr.c} | 0
 arch/x86/boot/compressed/misc.h              | 2 +-
 3 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 8774cb2..542c92f 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/kaslr.c
similarity index 100%
rename from arch/x86/boot/compressed/aslr.c
rename to arch/x86/boot/compressed/kaslr.c
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 3783dc3..a8c4e08 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,

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#1381904 — [PATCH 5/6] x86, KASLR: Clarify purpose of kaslr.c

The name "choose_kernel_location" isn't specific enough, and doesn't
describe the primary thing it does: choosing a random location. This
patch renames it to "choose_random_location", and clarifies the what
routines are contained in the kaslr.c source file.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/boot/compressed/kaslr.c | 13 ++++++++++++-
 arch/x86/boot/compressed/misc.c  |  2 +-
 arch/x86/boot/compressed/misc.h  |  4 ++--
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index a51ec841c9b9..9e03190d00ad 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -1,3 +1,14 @@
+/*
+ * kaslr.c
+ *
+ * This contains the routines needed to generate a reasonable level of
+ * entropy to choose a randomized kernel base address offset in support
+ * of Kernel Address Space Layout Randomization (KASLR). Additionally
+ * handles walking the physical memory maps (and tracking memory regions
+ * to avoid) in order to select a physical memory location that can
+ * contain the entire properly aligned running kernel image.
+ *
+ */
 #include "misc.h"
 
 #include <asm/msr.h>
@@ -295,7 +306,7 @@ static unsigned long find_random_addr(unsigned long minimum,
 	return slots_fetch_random();
 }
 
-unsigned char *choose_kernel_location(unsigned char *input,
+unsigned char *choose_random_location(unsigned char *input,
 				      unsigned long input_size,
 				      unsigned char *output,
 				      unsigned long output_size)
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 0d69e809673a..ad8c01ac2885 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -431,7 +431,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 	 * the entire decompressed kernel plus relocation table, or the
 	 * entire decompressed kernel plus .bss and .brk sections.
 	 */
-	output = choose_kernel_location(input_data, input_len, output,
+	output = choose_random_location(input_data, input_len, output,
 					output_len > run_size ? output_len
 							      : run_size);
 
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 1f750a516580..9887e0d4aaeb 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -67,7 +67,7 @@ int cmdline_find_option_bool(const char *option);
 
 #if CONFIG_RANDOMIZE_BASE
 /* kaslr.c */
-unsigned char *choose_kernel_location(unsigned char *input,
+unsigned char *choose_random_location(unsigned char *input,
 				      unsigned long input_size,
 				      unsigned char *output,
 				      unsigned long output_size);
@@ -75,7 +75,7 @@ unsigned char *choose_kernel_location(unsigned char *input,
 bool has_cpuflag(int flag);
 #else
 static inline
-unsigned char *choose_kernel_location(unsigned char *input,
+unsigned char *choose_random_location(unsigned char *input,
 				      unsigned long input_size,
 				      unsigned char *output,
 				      unsigned long output_size)
-- 
2.6.3

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#1382321 — [tip:x86/boot] x86/KASLR: Clarify purpose of kaslr.c

Commit-ID:  7de828dfe607013546ece7ce25aa9839e8f93a66
Gitweb:     http://git.kernel.org/tip/7de828dfe607013546ece7ce25aa9839e8f93a66
Author:     Kees Cook <keescook@chromium.org>
AuthorDate: Mon, 18 Apr 2016 09:42:14 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 19 Apr 2016 10:30:51 +0200

x86/KASLR: Clarify purpose of kaslr.c

The name "choose_kernel_location" isn't specific enough, and doesn't
describe the primary thing it does: choosing a random location. This
patch renames it to "choose_random_location", and clarifies the what
routines are contained in the kaslr.c source file.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: H.J. Lu <hjl.tools@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1460997735-24785-6-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/boot/compressed/kaslr.c | 13 ++++++++++++-
 arch/x86/boot/compressed/misc.c  |  2 +-
 arch/x86/boot/compressed/misc.h  |  4 ++--
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index a51ec84..9e03190 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -1,3 +1,14 @@
+/*
+ * kaslr.c
+ *
+ * This contains the routines needed to generate a reasonable level of
+ * entropy to choose a randomized kernel base address offset in support
+ * of Kernel Address Space Layout Randomization (KASLR). Additionally
+ * handles walking the physical memory maps (and tracking memory regions
+ * to avoid) in order to select a physical memory location that can
+ * contain the entire properly aligned running kernel image.
+ *
+ */
 #include "misc.h"
 
 #include <asm/msr.h>
@@ -295,7 +306,7 @@ static unsigned long find_random_addr(unsigned long minimum,
 	return slots_fetch_random();
 }
 
-unsigned char *choose_kernel_location(unsigned char *input,
+unsigned char *choose_random_location(unsigned char *input,
 				      unsigned long input_size,
 				      unsigned char *output,
 				      unsigned long output_size)
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 0d69e80..ad8c01a 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -431,7 +431,7 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 	 * the entire decompressed kernel plus relocation table, or the
 	 * entire decompressed kernel plus .bss and .brk sections.
 	 */
-	output = choose_kernel_location(input_data, input_len, output,
+	output = choose_random_location(input_data, input_len, output,
 					output_len > run_size ? output_len
 							      : run_size);
 
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 1f750a51..9887e0d 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -67,7 +67,7 @@ int cmdline_find_option_bool(const char *option);
 
 #if CONFIG_RANDOMIZE_BASE
 /* kaslr.c */
-unsigned char *choose_kernel_location(unsigned char *input,
+unsigned char *choose_random_location(unsigned char *input,
 				      unsigned long input_size,
 				      unsigned char *output,
 				      unsigned long output_size);
@@ -75,7 +75,7 @@ unsigned char *choose_kernel_location(unsigned char *input,
 bool has_cpuflag(int flag);
 #else
 static inline
-unsigned char *choose_kernel_location(unsigned char *input,
+unsigned char *choose_random_location(unsigned char *input,
 				      unsigned long input_size,
 				      unsigned char *output,
 				      unsigned long output_size)

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#1381905 — [PATCH 4/6] x86, boot: Clarify purpose of functions in misc.c

The function "decompress_kernel" now performs many more duties, so this
patch renames it to "extract_kernel" and updates callers and comments.
Additionally the file header comment for misc.c is improved to actually
describe what is contained.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/boot/compressed/head_32.S |  8 ++++----
 arch/x86/boot/compressed/head_64.S |  4 ++--
 arch/x86/boot/compressed/misc.c    | 10 ++++++----
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 0256064da8da..26dd9df19a69 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -233,9 +233,9 @@ relocated:
 2:
 
 /*
- * Do the decompression, and jump to the new kernel..
+ * Do the extraction, and jump to the new kernel..
  */
-				/* push arguments for decompress_kernel: */
+				/* push arguments for extract_kernel: */
 	pushl	$z_run_size	/* size of kernel with .bss and .brk */
 	pushl	$z_output_len	/* decompressed length, end of relocs */
 	leal	z_extract_offset_negative(%ebx), %ebp
@@ -246,11 +246,11 @@ relocated:
 	leal	boot_heap(%ebx), %eax
 	pushl	%eax		/* heap area */
 	pushl	%esi		/* real mode pointer */
-	call	decompress_kernel /* returns kernel location in %eax */
+	call	extract_kernel	/* returns kernel location in %eax */
 	addl	$28, %esp
 
 /*
- * Jump to the decompressed kernel.
+ * Jump to the extracted kernel.
  */
 	xorl	%ebx, %ebx
 	jmp	*%eax
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 86558a199139..d43c30ed89ed 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -408,7 +408,7 @@ relocated:
 2:
 	
 /*
- * Do the decompression, and jump to the new kernel..
+ * Do the extraction, and jump to the new kernel..
  */
 	pushq	%rsi			/* Save the real mode argument */
 	movq	$z_run_size, %r9	/* size of kernel with .bss and .brk */
@@ -419,7 +419,7 @@ relocated:
 	movl	$z_input_len, %ecx	/* input_len */
 	movq	%rbp, %r8		/* output target address */
 	movq	$z_output_len, %r9	/* decompressed length, end of relocs */
-	call	decompress_kernel	/* returns kernel location in %rax */
+	call	extract_kernel		/* returns kernel location in %rax */
 	popq	%r9
 	popq	%rsi
 
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 462dfbf7467b..0d69e809673a 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -1,8 +1,10 @@
 /*
  * misc.c
  *
- * This is a collection of several routines from gzip-1.0.3
- * adapted for Linux.
+ * This is a collection of several routines used to extract the kernel
+ * which includes KASLR relocation, decompression, ELF parsing, and
+ * relocation processing. Additionally included are the screen and serial
+ * output functions and related debugging support functions.
  *
  * malloc by Hannu Savolainen 1993 and Matthias Urlichs 1994
  * puts by Nick Holloway 1993, better puts by Martin Mares 1995
@@ -383,7 +385,7 @@ static void parse_elf(void *output)
 	free(phdrs);
 }
 
-asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
+asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 				  unsigned char *input_data,
 				  unsigned long input_len,
 				  unsigned char *output,
@@ -412,7 +414,7 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
 	cols = boot_params->screen_info.orig_video_cols;
 
 	console_init();
-	debug_putstr("early console in decompress_kernel\n");
+	debug_putstr("early console in extract_kernel\n");
 
 	free_mem_ptr     = heap;	/* Heap */
 	free_mem_end_ptr = heap + BOOT_HEAP_SIZE;
-- 
2.6.3

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#1382324 — [tip:x86/boot] x86/boot: Clarify purpose of functions in misc.c

Commit-ID:  c04028813221c2d39a4f368586795ac4466d311c
Gitweb:     http://git.kernel.org/tip/c04028813221c2d39a4f368586795ac4466d311c
Author:     Kees Cook <keescook@chromium.org>
AuthorDate: Mon, 18 Apr 2016 09:42:13 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 19 Apr 2016 10:30:51 +0200

x86/boot: Clarify purpose of functions in misc.c

The function "decompress_kernel" now performs many more duties, so this
patch renames it to "extract_kernel" and updates callers and comments.
Additionally the file header comment for misc.c is improved to actually
describe what is contained.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: H.J. Lu <hjl.tools@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1460997735-24785-5-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/boot/compressed/head_32.S |  8 ++++----
 arch/x86/boot/compressed/head_64.S |  4 ++--
 arch/x86/boot/compressed/misc.c    | 10 ++++++----
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 0256064..26dd9df 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -233,9 +233,9 @@ relocated:
 2:
 
 /*
- * Do the decompression, and jump to the new kernel..
+ * Do the extraction, and jump to the new kernel..
  */
-				/* push arguments for decompress_kernel: */
+				/* push arguments for extract_kernel: */
 	pushl	$z_run_size	/* size of kernel with .bss and .brk */
 	pushl	$z_output_len	/* decompressed length, end of relocs */
 	leal	z_extract_offset_negative(%ebx), %ebp
@@ -246,11 +246,11 @@ relocated:
 	leal	boot_heap(%ebx), %eax
 	pushl	%eax		/* heap area */
 	pushl	%esi		/* real mode pointer */
-	call	decompress_kernel /* returns kernel location in %eax */
+	call	extract_kernel	/* returns kernel location in %eax */
 	addl	$28, %esp
 
 /*
- * Jump to the decompressed kernel.
+ * Jump to the extracted kernel.
  */
 	xorl	%ebx, %ebx
 	jmp	*%eax
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 86558a1..d43c30e 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -408,7 +408,7 @@ relocated:
 2:
 	
 /*
- * Do the decompression, and jump to the new kernel..
+ * Do the extraction, and jump to the new kernel..
  */
 	pushq	%rsi			/* Save the real mode argument */
 	movq	$z_run_size, %r9	/* size of kernel with .bss and .brk */
@@ -419,7 +419,7 @@ relocated:
 	movl	$z_input_len, %ecx	/* input_len */
 	movq	%rbp, %r8		/* output target address */
 	movq	$z_output_len, %r9	/* decompressed length, end of relocs */
-	call	decompress_kernel	/* returns kernel location in %rax */
+	call	extract_kernel		/* returns kernel location in %rax */
 	popq	%r9
 	popq	%rsi
 
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 462dfbf..0d69e80 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -1,8 +1,10 @@
 /*
  * misc.c
  *
- * This is a collection of several routines from gzip-1.0.3
- * adapted for Linux.
+ * This is a collection of several routines used to extract the kernel
+ * which includes KASLR relocation, decompression, ELF parsing, and
+ * relocation processing. Additionally included are the screen and serial
+ * output functions and related debugging support functions.
  *
  * malloc by Hannu Savolainen 1993 and Matthias Urlichs 1994
  * puts by Nick Holloway 1993, better puts by Martin Mares 1995
@@ -383,7 +385,7 @@ static void parse_elf(void *output)
 	free(phdrs);
 }
 
-asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
+asmlinkage __visible void *extract_kernel(void *rmode, memptr heap,
 				  unsigned char *input_data,
 				  unsigned long input_len,
 				  unsigned char *output,
@@ -412,7 +414,7 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap,
 	cols = boot_params->screen_info.orig_video_cols;
 
 	console_init();
-	debug_putstr("early console in decompress_kernel\n");
+	debug_putstr("early console in extract_kernel\n");
 
 	free_mem_ptr     = heap;	/* Heap */
 	free_mem_end_ptr = heap + BOOT_HEAP_SIZE;

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#1381908 — [PATCH 6/6] x86, KASLR: Rename "random" to "random_addr"

The variable "random" is also the name of a libc function. It's better
coding style to avoid overloading such things, so rename it to the more
accurate "random_addr".

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/boot/compressed/kaslr.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 9e03190d00ad..9c29e7885ef0 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -312,7 +312,7 @@ unsigned char *choose_random_location(unsigned char *input,
 				      unsigned long output_size)
 {
 	unsigned long choice = (unsigned long)output;
-	unsigned long random;
+	unsigned long random_addr;
 
 #ifdef CONFIG_HIBERNATION
 	if (!cmdline_find_option_bool("kaslr")) {
@@ -333,17 +333,17 @@ unsigned char *choose_random_location(unsigned char *input,
 		       (unsigned long)output, output_size);
 
 	/* Walk e820 and find a random address. */
-	random = find_random_addr(choice, output_size);
-	if (!random) {
+	random_addr = find_random_addr(choice, output_size);
+	if (!random_addr) {
 		debug_putstr("KASLR could not find suitable E820 region...\n");
 		goto out;
 	}
 
 	/* Always enforce the minimum. */
-	if (random < choice)
+	if (random_addr < choice)
 		goto out;
 
-	choice = random;
+	choice = random_addr;
 out:
 	return (unsigned char *)choice;
 }
-- 
2.6.3

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#1382328 — [tip:x86/boot] x86/KASLR: Rename "random" to "random_addr"

Commit-ID:  9016875df408fc5db6a94a3c5f5f5503c916cf81
Gitweb:     http://git.kernel.org/tip/9016875df408fc5db6a94a3c5f5f5503c916cf81
Author:     Kees Cook <keescook@chromium.org>
AuthorDate: Mon, 18 Apr 2016 09:42:15 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 19 Apr 2016 10:30:51 +0200

x86/KASLR: Rename "random" to "random_addr"

The variable "random" is also the name of a libc function. It's better
coding style to avoid overloading such things, so rename it to the more
accurate "random_addr".

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: H.J. Lu <hjl.tools@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1460997735-24785-7-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/boot/compressed/kaslr.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 9e03190..9c29e78 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -312,7 +312,7 @@ unsigned char *choose_random_location(unsigned char *input,
 				      unsigned long output_size)
 {
 	unsigned long choice = (unsigned long)output;
-	unsigned long random;
+	unsigned long random_addr;
 
 #ifdef CONFIG_HIBERNATION
 	if (!cmdline_find_option_bool("kaslr")) {
@@ -333,17 +333,17 @@ unsigned char *choose_random_location(unsigned char *input,
 		       (unsigned long)output, output_size);
 
 	/* Walk e820 and find a random address. */
-	random = find_random_addr(choice, output_size);
-	if (!random) {
+	random_addr = find_random_addr(choice, output_size);
+	if (!random_addr) {
 		debug_putstr("KASLR could not find suitable E820 region...\n");
 		goto out;
 	}
 
 	/* Always enforce the minimum. */
-	if (random < choice)
+	if (random_addr < choice)
 		goto out;
 
-	choice = random;
+	choice = random_addr;
 out:
 	return (unsigned char *)choice;
 }

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#1382284

* Kees Cook <keescook@chromium.org> wrote:

> In order to make improvements to KASLR behavior, it has been suggested
> that the code should be cleaned up a bit first. This is the start of
> those changes. Since there are no stand-alone bug fixes in the later
> patches, I will begin here. First with a rename followed by variable
> name changes and comment improvements.
> 
> This is the first wave...

Ok, that was a really pleasant series - this is exactly what I hoped to see. I've 
put them into tip:x86/boot (as the changes involve more than just KASLR), based on 
v4.6-rc4.

Thanks,

	Ingo

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