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LoongArch: Add support for kernel relocation
This config allows to compile kernel as PIE and to relocate it at any virtual address at runtime: this paves the way to KASLR. Runtime relocation is possible since relocation metadata are embedded into the kernel. Signed-off-by: Youling Tang <tangyouling@loongson.cn> Signed-off-by: Xi Ruoyao <xry111@xry111.site> # Use arch_initcall Signed-off-by: Jinyang He <hejinyang@loongson.cn> # Provide la_abs relocation code Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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Youling Tang
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Huacai Chen
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Feb 25, 2023
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,107 @@ | ||
| // SPDX-License-Identifier: GPL-2.0 | ||
| /* | ||
| * Support for Kernel relocation at boot time | ||
| * | ||
| * Copyright (C) 2023 Loongson Technology Corporation Limited | ||
| */ | ||
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| #include <linux/elf.h> | ||
| #include <linux/kernel.h> | ||
| #include <linux/printk.h> | ||
| #include <linux/panic_notifier.h> | ||
| #include <asm/inst.h> | ||
| #include <asm/sections.h> | ||
| #include <asm/setup.h> | ||
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| #define RELOCATED(x) ((void *)((long)x + reloc_offset)) | ||
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| static unsigned long reloc_offset; | ||
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| 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; | ||
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| for ( ; rela < rela_end; rela++) { | ||
| Elf64_Addr addr = rela->r_offset; | ||
| Elf64_Addr relocated_addr = rela->r_addend; | ||
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| if (rela->r_info != R_LARCH_RELATIVE) | ||
| continue; | ||
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| if (relocated_addr >= VMLINUX_LOAD_ADDRESS) | ||
| relocated_addr = (Elf64_Addr)RELOCATED(relocated_addr); | ||
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| *(Elf64_Addr *)RELOCATED(addr) = relocated_addr; | ||
| } | ||
| } | ||
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| static inline void __init relocate_absolute(void) | ||
| { | ||
| void *begin, *end; | ||
| struct rela_la_abs *p; | ||
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| begin = &__la_abs_begin; | ||
| end = &__la_abs_end; | ||
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| 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; | ||
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| lu12iw = (v >> 12) & 0xfffff; | ||
| ori = v & 0xfff; | ||
| lu32id = (v >> 32) & 0xfffff; | ||
| lu52id = v >> 52; | ||
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| insn[0].reg1i20_format.immediate = lu12iw; | ||
| insn[1].reg2i12_format.immediate = ori; | ||
| insn[2].reg1i20_format.immediate = lu32id; | ||
| insn[3].reg2i12_format.immediate = lu52id; | ||
| } | ||
| } | ||
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| void __init relocate_kernel(void) | ||
| { | ||
| reloc_offset = (unsigned long)_text - VMLINUX_LOAD_ADDRESS; | ||
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| if (reloc_offset) | ||
| relocate_relative(); | ||
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| relocate_absolute(); | ||
| } | ||
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| /* | ||
| * 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); | ||
| } | ||
| } | ||
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| static int kernel_location_notifier_fn(struct notifier_block *self, | ||
| unsigned long v, void *p) | ||
| { | ||
| show_kernel_relocation(KERN_EMERG); | ||
| return NOTIFY_DONE; | ||
| } | ||
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| static struct notifier_block kernel_location_notifier = { | ||
| .notifier_call = kernel_location_notifier_fn | ||
| }; | ||
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| static int __init register_kernel_offset_dumper(void) | ||
| { | ||
| atomic_notifier_chain_register(&panic_notifier_list, | ||
| &kernel_location_notifier); | ||
| return 0; | ||
| } | ||
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| arch_initcall(register_kernel_offset_dumper); |
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