1 files changed, 386 insertions, 0 deletions
diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
new file mode 100644
index 000000000000..ca1cc30c0891
--- /dev/null
+++ b/arch/mips/kernel/relocate.c
@@ -0,0 +1,386 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Support for Kernel relocation at boot time
+ *
+ * Copyright (C) 2015, Imagination Technologies Ltd.
+ * Authors: Matt Redfearn (matt.redfearn@imgtec.com)
+ */
+#include <asm/bootinfo.h>
+#include <asm/cacheflush.h>
+#include <asm/fw/fw.h>
+#include <asm/sections.h>
+#include <asm/setup.h>
+#include <asm/timex.h>
+#include <linux/elf.h>
+#include <linux/kernel.h>
+#include <linux/libfdt.h>
+#include <linux/of_fdt.h>
+#include <linux/sched.h>
+#include <linux/start_kernel.h>
+#include <linux/string.h>
+#include <linux/printk.h>
+
+#define RELOCATED(x) ((void *)((long)x + offset))
+
+extern u32 _relocation_start[];	/* End kernel image / start relocation table */
+extern u32 _relocation_end[];	/* End relocation table */
+
+extern long __start___ex_table;	/* Start exception table */
+extern long __stop___ex_table;	/* End exception table */
+
+static inline u32 __init get_synci_step(void)
+{
+	u32 res;
+
+	__asm__("rdhwr  %0, $1" : "=r" (res));
+
+	return res;
+}
+
+static void __init sync_icache(void *kbase, unsigned long kernel_length)
+{
+	void *kend = kbase + kernel_length;
+	u32 step = get_synci_step();
+
+	do {
+		__asm__ __volatile__(
+			"synci  0(%0)"
+			: /* no output */
+			: "r" (kbase));
+
+		kbase += step;
+	} while (kbase < kend);
+
+	/* Completion barrier */
+	__sync();
+}
+
+static int __init apply_r_mips_64_rel(u32 *loc_orig, u32 *loc_new, long offset)
+{
+	*(u64 *)loc_new += offset;
+
+	return 0;
+}
+
+static int __init apply_r_mips_32_rel(u32 *loc_orig, u32 *loc_new, long offset)
+{
+	*loc_new += offset;
+
+	return 0;
+}
+
+static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
+{
+	unsigned long target_addr = (*loc_orig) & 0x03ffffff;
+
+	if (offset % 4) {
+		pr_err("Dangerous R_MIPS_26 REL relocation\n");
+		return -ENOEXEC;
+	}
+
+	/* Original target address */
+	target_addr <<= 2;
+	target_addr += (unsigned long)loc_orig & ~0x03ffffff;
+
+	/* Get the new target address */
+	target_addr += offset;
+
+	if ((target_addr & 0xf0000000) != ((unsigned long)loc_new & 0xf0000000)) {
+		pr_err("R_MIPS_26 REL relocation overflow\n");
+		return -ENOEXEC;
+	}
+
+	target_addr -= (unsigned long)loc_new & ~0x03ffffff;
+	target_addr >>= 2;
+
+	*loc_new = (*loc_new & ~0x03ffffff) | (target_addr & 0x03ffffff);
+
+	return 0;
+}
+
+
+static int __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new, long offset)
+{
+	unsigned long insn = *loc_orig;
+	unsigned long target = (insn & 0xffff) << 16; /* high 16bits of target */
+
+	target += offset;
+
+	*loc_new = (insn & ~0xffff) | ((target >> 16) & 0xffff);
+	return 0;
+}
+
+static int (*reloc_handlers_rel[]) (u32 *, u32 *, long) __initdata = {
+	[R_MIPS_64]		= apply_r_mips_64_rel,
+	[R_MIPS_32]		= apply_r_mips_32_rel,
+	[R_MIPS_26]		= apply_r_mips_26_rel,
+	[R_MIPS_HI16]		= apply_r_mips_hi16_rel,
+};
+
+int __init do_relocations(void *kbase_old, void *kbase_new, long offset)
+{
+	u32 *r;
+	u32 *loc_orig;
+	u32 *loc_new;
+	int type;
+	int res;
+
+	for (r = _relocation_start; r < _relocation_end; r++) {
+		/* Sentinel for last relocation */
+		if (*r == 0)
+			break;
+
+		type = (*r >> 24) & 0xff;
+		loc_orig = (void *)(kbase_old + ((*r & 0x00ffffff) << 2));
+		loc_new = RELOCATED(loc_orig);
+
+		if (reloc_handlers_rel[type] == NULL) {
+			/* Unsupported relocation */
+			pr_err("Unhandled relocation type %d at 0x%pK\n",
+			       type, loc_orig);
+			return -ENOEXEC;
+		}
+
+		res = reloc_handlers_rel[type](loc_orig, loc_new, offset);
+		if (res)
+			return res;
+	}
+
+	return 0;
+}
+
+/*
+ * The exception table is filled in by the relocs tool after vmlinux is linked.
+ * It must be relocated separately since there will not be any relocation
+ * information for it filled in by the linker.
+ */
+static int __init relocate_exception_table(long offset)
+{
+	unsigned long *etable_start, *etable_end, *e;
+
+	etable_start = RELOCATED(&__start___ex_table);
+	etable_end = RELOCATED(&__stop___ex_table);
+
+	for (e = etable_start; e < etable_end; e++)
+		*e += offset;
+
+	return 0;
+}
+
+#ifdef CONFIG_RANDOMIZE_BASE
+
+static inline __init 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;
+}
+
+static inline __init unsigned long get_random_boot(void)
+{
+	unsigned long entropy = random_get_entropy();
+	unsigned long hash = 0;
+
+	/* Attempt to create a simple but unpredictable starting entropy. */
+	hash = rotate_xor(hash, linux_banner, strlen(linux_banner));
+
+	/* Add in any runtime entropy we can get */
+	hash = rotate_xor(hash, &entropy, sizeof(entropy));
+
+#if defined(CONFIG_USE_OF)
+	/* Get any additional entropy passed in device tree */
+	{
+		int node, len;
+		u64 *prop;
+
+		node = fdt_path_offset(initial_boot_params, "/chosen");
+		if (node >= 0) {
+			prop = fdt_getprop_w(initial_boot_params, node,
+					     "kaslr-seed", &len);
+			if (prop && (len == sizeof(u64)))
+				hash = rotate_xor(hash, prop, sizeof(*prop));
+		}
+	}
+#endif /* CONFIG_USE_OF */
+
+	return hash;
+}
+
+static inline __init bool kaslr_disabled(void)
+{
+	char *str;
+
+#if defined(CONFIG_CMDLINE_BOOL)
+	const char *builtin_cmdline = CONFIG_CMDLINE;
+
+	str = strstr(builtin_cmdline, "nokaslr");
+	if (str == builtin_cmdline ||
+	    (str > builtin_cmdline && *(str - 1) == ' '))
+		return true;
+#endif
+	str = strstr(arcs_cmdline, "nokaslr");
+	if (str == arcs_cmdline || (str > arcs_cmdline && *(str - 1) == ' '))
+		return true;
+
+	return false;
+}
+
+static inline void __init *determine_relocation_address(void)
+{
+	/* Choose a new address for the kernel */
+	unsigned long kernel_length;
+	void *dest = &_text;
+	unsigned long offset;
+
+	if (kaslr_disabled())
+		return dest;
+
+	kernel_length = (long)_end - (long)(&_text);
+
+	offset = get_random_boot() << 16;
+	offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);
+	if (offset < kernel_length)
+		offset += ALIGN(kernel_length, 0xffff);
+
+	return RELOCATED(dest);
+}
+
+#else
+
+static inline void __init *determine_relocation_address(void)
+{
+	/*
+	 * Choose a new address for the kernel
+	 * For now we'll hard code the destination
+	 */
+	return (void *)0xffffffff81000000;
+}
+
+#endif
+
+static inline int __init relocation_addr_valid(void *loc_new)
+{
+	if ((unsigned long)loc_new & 0x0000ffff) {
+		/* Inappropriately aligned new location */
+		return 0;
+	}
+	if ((unsigned long)loc_new < (unsigned long)&_end) {
+		/* New location overlaps original kernel */
+		return 0;
+	}
+	return 1;
+}
+
+void *__init relocate_kernel(void)
+{
+	void *loc_new;
+	unsigned long kernel_length;
+	unsigned long bss_length;
+	long offset = 0;
+	int res = 1;
+	/* Default to original kernel entry point */
+	void *kernel_entry = start_kernel;
+
+	/* Get the command line */
+	fw_init_cmdline();
+#if defined(CONFIG_USE_OF)
+	/* Deal with the device tree */
+	early_init_dt_scan(plat_get_fdt());
+	if (boot_command_line[0]) {
+		/* Boot command line was passed in device tree */
+		strlcpy(arcs_cmdline, boot_command_line, COMMAND_LINE_SIZE);
+	}
+#endif /* CONFIG_USE_OF */
+
+	kernel_length = (long)(&_relocation_start) - (long)(&_text);
+	bss_length = (long)&__bss_stop - (long)&__bss_start;
+
+	loc_new = determine_relocation_address();
+
+	/* Sanity check relocation address */
+	if (relocation_addr_valid(loc_new))
+		offset = (unsigned long)loc_new - (unsigned long)(&_text);
+
+	/* Reset the command line now so we don't end up with a duplicate */
+	arcs_cmdline[0] = '\0';
+
+	if (offset) {
+		/* Copy the kernel to it's new location */
+		memcpy(loc_new, &_text, kernel_length);
+
+		/* Perform relocations on the new kernel */
+		res = do_relocations(&_text, loc_new, offset);
+		if (res < 0)
+			goto out;
+
+		/* Sync the caches ready for execution of new kernel */
+		sync_icache(loc_new, kernel_length);
+
+		res = relocate_exception_table(offset);
+		if (res < 0)
+			goto out;
+
+		/*
+		 * The original .bss has already been cleared, and
+		 * some variables such as command line parameters
+		 * stored to it so make a copy in the new location.
+		 */
+		memcpy(RELOCATED(&__bss_start), &__bss_start, bss_length);
+
+		/* The current thread is now within the relocated image */
+		__current_thread_info = RELOCATED(&init_thread_union);
+
+		/* Return the new kernel's entry point */
+		kernel_entry = RELOCATED(start_kernel);
+	}
+out:
+	return kernel_entry;
+}
+
+/*
+ * Show relocation information on panic.
+ */
+void show_kernel_relocation(const char *level)
+{
+	unsigned long offset;
+
+	offset = __pa_symbol(_text) - __pa_symbol(VMLINUX_LOAD_ADDRESS);
+
+	if (IS_ENABLED(CONFIG_RELOCATABLE) && offset > 0) {
+		printk(level);
+		pr_cont("Kernel relocated by 0x%pK\n", (void *)offset);
+		pr_cont(" .text @ 0x%pK\n", _text);
+		pr_cont(" .data @ 0x%pK\n", _sdata);
+		pr_cont(" .bss  @ 0x%pK\n", __bss_start);
+	}
+}
+
+static int kernel_location_notifier_fn(struct notifier_block *self,
+				       unsigned long v, void *p)
+{
+	show_kernel_relocation(KERN_EMERG);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block kernel_location_notifier = {
+	.notifier_call = kernel_location_notifier_fn
+};
+
+static int __init register_kernel_offset_dumper(void)
+{
+	atomic_notifier_chain_register(&panic_notifier_list,
+				       &kernel_location_notifier);
+	return 0;
+}
+__initcall(register_kernel_offset_dumper);