1 files changed, 242 insertions, 0 deletions
diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
new file mode 100644
index 000000000000..01f94d1e3edf
--- /dev/null
+++ b/arch/loongarch/kernel/relocate.c
@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Support for Kernel relocation at boot time
+ *
+ * Copyright (C) 2023 Loongson Technology Corporation Limited
+ */
+
+#include <linux/elf.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/panic_notifier.h>
+#include <linux/start_kernel.h>
+#include <asm/bootinfo.h>
+#include <asm/early_ioremap.h>
+#include <asm/inst.h>
+#include <asm/sections.h>
+#include <asm/setup.h>
+
+#define RELOCATED(x) ((void *)((long)x + reloc_offset))
+#define RELOCATED_KASLR(x) ((void *)((long)x + random_offset))
+
+static unsigned long reloc_offset;
+
+static inline void __init relocate_relative(void)
+{
+	Elf64_Rela *rela, *rela_end;
+	rela = (Elf64_Rela *)&__rela_dyn_begin;
+	rela_end = (Elf64_Rela *)&__rela_dyn_end;
+
+	for ( ; rela < rela_end; rela++) {
+		Elf64_Addr addr = rela->r_offset;
+		Elf64_Addr relocated_addr = rela->r_addend;
+
+		if (rela->r_info != R_LARCH_RELATIVE)
+			continue;
+
+		if (relocated_addr >= VMLINUX_LOAD_ADDRESS)
+			relocated_addr = (Elf64_Addr)RELOCATED(relocated_addr);
+
+		*(Elf64_Addr *)RELOCATED(addr) = relocated_addr;
+	}
+}
+
+static inline void __init relocate_absolute(long random_offset)
+{
+	void *begin, *end;
+	struct rela_la_abs *p;
+
+	begin = RELOCATED_KASLR(&__la_abs_begin);
+	end   = RELOCATED_KASLR(&__la_abs_end);
+
+	for (p = begin; (void *)p < end; p++) {
+		long v = p->symvalue;
+		uint32_t lu12iw, ori, lu32id, lu52id;
+		union loongarch_instruction *insn = (void *)p - p->offset;
+
+		lu12iw = (v >> 12) & 0xfffff;
+		ori    = v & 0xfff;
+		lu32id = (v >> 32) & 0xfffff;
+		lu52id = v >> 52;
+
+		insn[0].reg1i20_format.immediate = lu12iw;
+		insn[1].reg2i12_format.immediate = ori;
+		insn[2].reg1i20_format.immediate = lu32id;
+		insn[3].reg2i12_format.immediate = lu52id;
+	}
+}
+
+#ifdef CONFIG_RANDOMIZE_BASE
+static inline __init unsigned long rotate_xor(unsigned long hash,
+					      const void *area, size_t size)
+{
+	size_t i, diff;
+	const typeof(hash) *ptr = PTR_ALIGN(area, sizeof(hash));
+
+	diff = (void *)ptr - area;
+	if (size < diff + sizeof(hash))
+		return hash;
+
+	size = ALIGN_DOWN(size - diff, sizeof(hash));
+
+	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 hash = 0;
+	unsigned long entropy = random_get_entropy();
+
+	/* 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));
+
+	return hash;
+}
+
+static inline __init bool kaslr_disabled(void)
+{
+	char *str;
+	const char *builtin_cmdline = CONFIG_CMDLINE;
+
+	str = strstr(builtin_cmdline, "nokaslr");
+	if (str == builtin_cmdline || (str > builtin_cmdline && *(str - 1) == ' '))
+		return true;
+
+	str = strstr(boot_command_line, "nokaslr");
+	if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' '))
+		return true;
+
+	return false;
+}
+
+/* Choose a new address for the kernel */
+static inline void __init *determine_relocation_address(void)
+{
+	unsigned long kernel_length;
+	unsigned long random_offset;
+	void *destination = _text;
+
+	if (kaslr_disabled())
+		return destination;
+
+	kernel_length = (long)_end - (long)_text;
+
+	random_offset = get_random_boot() << 16;
+	random_offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);
+	if (random_offset < kernel_length)
+		random_offset += ALIGN(kernel_length, 0xffff);
+
+	return RELOCATED_KASLR(destination);
+}
+
+static inline int __init relocation_addr_valid(void *location_new)
+{
+	if ((unsigned long)location_new & 0x00000ffff)
+		return 0; /* Inappropriately aligned new location */
+
+	if ((unsigned long)location_new < (unsigned long)_end)
+		return 0; /* New location overlaps original kernel */
+
+	return 1;
+}
+#endif
+
+static inline void __init update_reloc_offset(unsigned long *addr, long random_offset)
+{
+	unsigned long *new_addr = (unsigned long *)RELOCATED_KASLR(addr);
+
+	*new_addr = (unsigned long)reloc_offset;
+}
+
+void * __init relocate_kernel(void)
+{
+	unsigned long kernel_length;
+	unsigned long random_offset = 0;
+	void *location_new = _text; /* Default to original kernel start */
+	void *kernel_entry = start_kernel; /* Default to original kernel entry point */
+	char *cmdline = early_ioremap(fw_arg1, COMMAND_LINE_SIZE); /* Boot command line is passed in fw_arg1 */
+
+	strscpy(boot_command_line, cmdline, COMMAND_LINE_SIZE);
+
+#ifdef CONFIG_RANDOMIZE_BASE
+	location_new = determine_relocation_address();
+
+	/* Sanity check relocation address */
+	if (relocation_addr_valid(location_new))
+		random_offset = (unsigned long)location_new - (unsigned long)(_text);
+#endif
+	reloc_offset = (unsigned long)_text - VMLINUX_LOAD_ADDRESS;
+
+	if (random_offset) {
+		kernel_length = (long)(_end) - (long)(_text);
+
+		/* Copy the kernel to it's new location */
+		memcpy(location_new, _text, kernel_length);
+
+		/* Sync the caches ready for execution of new kernel */
+		__asm__ __volatile__ (
+			"ibar 0 \t\n"
+			"dbar 0 \t\n"
+			::: "memory");
+
+		reloc_offset += random_offset;
+
+		/* Return the new kernel's entry point */
+		kernel_entry = RELOCATED_KASLR(start_kernel);
+
+		/* The current thread is now within the relocated kernel */
+		__current_thread_info = RELOCATED_KASLR(__current_thread_info);
+
+		update_reloc_offset(&reloc_offset, random_offset);
+	}
+
+	if (reloc_offset)
+		relocate_relative();
+
+	relocate_absolute(random_offset);
+
+	return kernel_entry;
+}
+
+/*
+ * Show relocation information on panic.
+ */
+static void show_kernel_relocation(const char *level)
+{
+	if (reloc_offset > 0) {
+		printk(level);
+		pr_cont("Kernel relocated by 0x%lx\n", reloc_offset);
+		pr_cont(" .text @ 0x%px\n", _text);
+		pr_cont(" .data @ 0x%px\n", _sdata);
+		pr_cont(" .bss  @ 0x%px\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;
+}
+
+arch_initcall(register_kernel_offset_dumper);