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>
This commit is contained in:
Youling Tang
Huacai Chen
parent
396233c650
commit
d8da19fbde
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@ -493,6 +493,14 @@ config PHYSICAL_START
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specified in the "crashkernel=YM@XM" command line boot parameter
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passed to the panic-ed kernel).
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config RELOCATABLE
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bool "Relocatable kernel"
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help
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This builds the kernel as a Position Independent Executable (PIE),
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which retains all relocation metadata required, so as to relocate
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the kernel binary at runtime to a different virtual address from
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its link address.
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config SECCOMP
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bool "Enable seccomp to safely compute untrusted bytecode"
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depends on PROC_FS
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@ -71,6 +71,11 @@ KBUILD_AFLAGS_MODULE += -Wa,-mla-global-with-abs
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KBUILD_CFLAGS_MODULE += -fplt -Wa,-mla-global-with-abs,-mla-local-with-abs
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endif
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ifeq ($(CONFIG_RELOCATABLE),y)
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KBUILD_CFLAGS_KERNEL += -fPIE
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LDFLAGS_vmlinux += -static -pie --no-dynamic-linker -z notext
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endif
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cflags-y += -ffreestanding
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cflags-y += $(call cc-option, -mno-check-zero-division)
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@ -275,7 +275,20 @@
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.endm
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.macro la_abs reg, sym
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#ifndef CONFIG_RELOCATABLE
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la.abs \reg, \sym
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#else
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766:
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lu12i.w \reg, 0
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ori \reg, \reg, 0
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lu32i.d \reg, 0
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lu52i.d \reg, \reg, 0
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.pushsection ".la_abs", "aw", %progbits
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768:
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.dword 768b-766b
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.dword \sym
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.popsection
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#endif
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.endm
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#endif /* _ASM_ASMMACRO_H */
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@ -21,4 +21,20 @@ extern void per_cpu_trap_init(int cpu);
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extern void set_handler(unsigned long offset, void *addr, unsigned long len);
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extern void set_merr_handler(unsigned long offset, void *addr, unsigned long len);
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#ifdef CONFIG_RELOCATABLE
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struct rela_la_abs {
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long offset;
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long symvalue;
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};
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extern long __la_abs_begin;
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extern long __la_abs_end;
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extern long __rela_dyn_begin;
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extern long __rela_dyn_end;
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extern void __init relocate_kernel(void);
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#endif
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#endif /* __SETUP_H */
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@ -41,6 +41,8 @@ obj-$(CONFIG_NUMA) += numa.o
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obj-$(CONFIG_MAGIC_SYSRQ) += sysrq.o
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obj-$(CONFIG_RELOCATABLE) += relocate.o
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obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
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obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
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@ -86,6 +86,10 @@ SYM_CODE_START(kernel_entry) # kernel entry point
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PTR_ADD sp, sp, tp
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set_saved_sp sp, t0, t1
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#ifdef CONFIG_RELOCATABLE
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bl relocate_kernel
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#endif
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bl start_kernel
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ASM_BUG()
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@ -0,0 +1,107 @@
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Support for Kernel relocation at boot time
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*
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* Copyright (C) 2023 Loongson Technology Corporation Limited
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*/
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#include <linux/elf.h>
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#include <linux/kernel.h>
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#include <linux/printk.h>
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#include <linux/panic_notifier.h>
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#include <asm/inst.h>
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#include <asm/sections.h>
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#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)
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{
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Elf64_Rela *rela, *rela_end;
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rela = (Elf64_Rela *)&__rela_dyn_begin;
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rela_end = (Elf64_Rela *)&__rela_dyn_end;
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for ( ; rela < rela_end; rela++) {
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Elf64_Addr addr = rela->r_offset;
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Elf64_Addr relocated_addr = rela->r_addend;
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if (rela->r_info != R_LARCH_RELATIVE)
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continue;
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if (relocated_addr >= VMLINUX_LOAD_ADDRESS)
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relocated_addr = (Elf64_Addr)RELOCATED(relocated_addr);
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*(Elf64_Addr *)RELOCATED(addr) = relocated_addr;
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}
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}
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static inline void __init relocate_absolute(void)
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{
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void *begin, *end;
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struct rela_la_abs *p;
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begin = &__la_abs_begin;
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end = &__la_abs_end;
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for (p = begin; (void *)p < end; p++) {
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long v = p->symvalue;
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uint32_t lu12iw, ori, lu32id, lu52id;
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union loongarch_instruction *insn = (void *)p - p->offset;
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lu12iw = (v >> 12) & 0xfffff;
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ori = v & 0xfff;
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lu32id = (v >> 32) & 0xfffff;
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lu52id = v >> 52;
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insn[0].reg1i20_format.immediate = lu12iw;
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insn[1].reg2i12_format.immediate = ori;
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insn[2].reg1i20_format.immediate = lu32id;
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insn[3].reg2i12_format.immediate = lu52id;
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}
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}
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void __init relocate_kernel(void)
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{
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reloc_offset = (unsigned long)_text - VMLINUX_LOAD_ADDRESS;
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if (reloc_offset)
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relocate_relative();
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relocate_absolute();
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}
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/*
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* Show relocation information on panic.
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*/
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static void show_kernel_relocation(const char *level)
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{
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if (reloc_offset > 0) {
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printk(level);
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pr_cont("Kernel relocated by 0x%lx\n", reloc_offset);
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pr_cont(" .text @ 0x%px\n", _text);
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pr_cont(" .data @ 0x%px\n", _sdata);
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pr_cont(" .bss @ 0x%px\n", __bss_start);
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}
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}
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static int kernel_location_notifier_fn(struct notifier_block *self,
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unsigned long v, void *p)
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{
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show_kernel_relocation(KERN_EMERG);
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return NOTIFY_DONE;
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}
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static struct notifier_block kernel_location_notifier = {
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.notifier_call = kernel_location_notifier_fn
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};
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static int __init register_kernel_offset_dumper(void)
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{
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atomic_notifier_chain_register(&panic_notifier_list,
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&kernel_location_notifier);
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return 0;
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}
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arch_initcall(register_kernel_offset_dumper);
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@ -66,10 +66,21 @@ SECTIONS
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__alt_instructions_end = .;
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}
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#ifdef CONFIG_RELOCATABLE
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. = ALIGN(8);
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.la_abs : AT(ADDR(.la_abs) - LOAD_OFFSET) {
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__la_abs_begin = .;
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*(.la_abs)
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__la_abs_end = .;
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}
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#endif
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.got : ALIGN(16) { *(.got) }
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.plt : ALIGN(16) { *(.plt) }
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.got.plt : ALIGN(16) { *(.got.plt) }
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.data.rel : { *(.data.rel*) }
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. = ALIGN(PECOFF_SEGMENT_ALIGN);
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__init_begin = .;
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__inittext_begin = .;
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@ -93,8 +104,6 @@ SECTIONS
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PERCPU_SECTION(1 << CONFIG_L1_CACHE_SHIFT)
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#endif
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.rela.dyn : ALIGN(8) { *(.rela.dyn) *(.rela*) }
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.init.bss : {
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*(.init.bss)
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}
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@ -107,6 +116,12 @@ SECTIONS
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RO_DATA(4096)
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RW_DATA(1 << CONFIG_L1_CACHE_SHIFT, PAGE_SIZE, THREAD_SIZE)
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.rela.dyn : ALIGN(8) {
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__rela_dyn_begin = .;
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*(.rela.dyn) *(.rela*)
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__rela_dyn_end = .;
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}
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.sdata : {
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*(.sdata)
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}
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@ -133,6 +148,7 @@ SECTIONS
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DISCARDS
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/DISCARD/ : {
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*(.dynamic .dynsym .dynstr .hash .gnu.hash)
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*(.gnu.attributes)
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*(.options)
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*(.eh_frame)
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