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authorYouling Tang <tangyouling@loongson.cn>2023-02-25 10:52:56 +0300
committerHuacai Chen <chenhuacai@loongson.cn>2023-02-25 17:12:16 +0300
commitd8da19fbdedd5852592fbba18a7348e3f09500e6 (patch)
treea6a4a921da97d0b7379e9034532c8267a14b631e /arch/loongarch
parent396233c650084cb957eb6d87dd4abd3e56a7d499 (diff)
downloadlinux-d8da19fbdedd5852592fbba18a7348e3f09500e6.tar.xz
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>
Diffstat (limited to 'arch/loongarch')
-rw-r--r--arch/loongarch/Kconfig8
-rw-r--r--arch/loongarch/Makefile5
-rw-r--r--arch/loongarch/include/asm/asmmacro.h13
-rw-r--r--arch/loongarch/include/asm/setup.h16
-rw-r--r--arch/loongarch/kernel/Makefile2
-rw-r--r--arch/loongarch/kernel/head.S4
-rw-r--r--arch/loongarch/kernel/relocate.c107
-rw-r--r--arch/loongarch/kernel/vmlinux.lds.S20
8 files changed, 173 insertions, 2 deletions
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 0c1c6063cc66..32ab90dd76e5 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -493,6 +493,14 @@ config PHYSICAL_START
specified in the "crashkernel=YM@XM" command line boot parameter
passed to the panic-ed kernel).
+config RELOCATABLE
+ bool "Relocatable kernel"
+ help
+ This builds the kernel as a Position Independent Executable (PIE),
+ which retains all relocation metadata required, so as to relocate
+ the kernel binary at runtime to a different virtual address from
+ its link address.
+
config SECCOMP
bool "Enable seccomp to safely compute untrusted bytecode"
depends on PROC_FS
diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
index 6e1c931a8507..768592998b39 100644
--- a/arch/loongarch/Makefile
+++ b/arch/loongarch/Makefile
@@ -71,6 +71,11 @@ KBUILD_AFLAGS_MODULE += -Wa,-mla-global-with-abs
KBUILD_CFLAGS_MODULE += -fplt -Wa,-mla-global-with-abs,-mla-local-with-abs
endif
+ifeq ($(CONFIG_RELOCATABLE),y)
+KBUILD_CFLAGS_KERNEL += -fPIE
+LDFLAGS_vmlinux += -static -pie --no-dynamic-linker -z notext
+endif
+
cflags-y += -ffreestanding
cflags-y += $(call cc-option, -mno-check-zero-division)
diff --git a/arch/loongarch/include/asm/asmmacro.h b/arch/loongarch/include/asm/asmmacro.h
index cdc9935d5554..c51a1b43acb4 100644
--- a/arch/loongarch/include/asm/asmmacro.h
+++ b/arch/loongarch/include/asm/asmmacro.h
@@ -275,7 +275,20 @@
.endm
.macro la_abs reg, sym
+#ifndef CONFIG_RELOCATABLE
la.abs \reg, \sym
+#else
+ 766:
+ lu12i.w \reg, 0
+ ori \reg, \reg, 0
+ lu32i.d \reg, 0
+ lu52i.d \reg, \reg, 0
+ .pushsection ".la_abs", "aw", %progbits
+ 768:
+ .dword 768b-766b
+ .dword \sym
+ .popsection
+#endif
.endm
#endif /* _ASM_ASMMACRO_H */
diff --git a/arch/loongarch/include/asm/setup.h b/arch/loongarch/include/asm/setup.h
index 72ead58039f3..27d968655b4b 100644
--- a/arch/loongarch/include/asm/setup.h
+++ b/arch/loongarch/include/asm/setup.h
@@ -21,4 +21,20 @@ extern void per_cpu_trap_init(int cpu);
extern void set_handler(unsigned long offset, void *addr, unsigned long len);
extern void set_merr_handler(unsigned long offset, void *addr, unsigned long len);
+#ifdef CONFIG_RELOCATABLE
+
+struct rela_la_abs {
+ long offset;
+ long symvalue;
+};
+
+extern long __la_abs_begin;
+extern long __la_abs_end;
+extern long __rela_dyn_begin;
+extern long __rela_dyn_end;
+
+extern void __init relocate_kernel(void);
+
+#endif
+
#endif /* __SETUP_H */
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index df5dbabfe7a6..94d33dbd4912 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -41,6 +41,8 @@ obj-$(CONFIG_NUMA) += numa.o
obj-$(CONFIG_MAGIC_SYSRQ) += sysrq.o
+obj-$(CONFIG_RELOCATABLE) += relocate.o
+
obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
index d2ac26b5b22b..c5c3ec2b819a 100644
--- a/arch/loongarch/kernel/head.S
+++ b/arch/loongarch/kernel/head.S
@@ -86,6 +86,10 @@ SYM_CODE_START(kernel_entry) # kernel entry point
PTR_ADD sp, sp, tp
set_saved_sp sp, t0, t1
+#ifdef CONFIG_RELOCATABLE
+ bl relocate_kernel
+#endif
+
bl start_kernel
ASM_BUG()
diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
new file mode 100644
index 000000000000..879c40372fba
--- /dev/null
+++ b/arch/loongarch/kernel/relocate.c
@@ -0,0 +1,107 @@
+// 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 <asm/inst.h>
+#include <asm/sections.h>
+#include <asm/setup.h>
+
+#define RELOCATED(x) ((void *)((long)x + reloc_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(void)
+{
+ void *begin, *end;
+ struct rela_la_abs *p;
+
+ begin = &__la_abs_begin;
+ end = &__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;
+ }
+}
+
+void __init relocate_kernel(void)
+{
+ reloc_offset = (unsigned long)_text - VMLINUX_LOAD_ADDRESS;
+
+ if (reloc_offset)
+ relocate_relative();
+
+ relocate_absolute();
+}
+
+/*
+ * 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);
diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vmlinux.lds.S
index 733b16e8d55d..ad2ce1a0908e 100644
--- a/arch/loongarch/kernel/vmlinux.lds.S
+++ b/arch/loongarch/kernel/vmlinux.lds.S
@@ -66,10 +66,21 @@ SECTIONS
__alt_instructions_end = .;
}
+#ifdef CONFIG_RELOCATABLE
+ . = ALIGN(8);
+ .la_abs : AT(ADDR(.la_abs) - LOAD_OFFSET) {
+ __la_abs_begin = .;
+ *(.la_abs)
+ __la_abs_end = .;
+ }
+#endif
+
.got : ALIGN(16) { *(.got) }
.plt : ALIGN(16) { *(.plt) }
.got.plt : ALIGN(16) { *(.got.plt) }
+ .data.rel : { *(.data.rel*) }
+
. = ALIGN(PECOFF_SEGMENT_ALIGN);
__init_begin = .;
__inittext_begin = .;
@@ -93,8 +104,6 @@ SECTIONS
PERCPU_SECTION(1 << CONFIG_L1_CACHE_SHIFT)
#endif
- .rela.dyn : ALIGN(8) { *(.rela.dyn) *(.rela*) }
-
.init.bss : {
*(.init.bss)
}
@@ -107,6 +116,12 @@ SECTIONS
RO_DATA(4096)
RW_DATA(1 << CONFIG_L1_CACHE_SHIFT, PAGE_SIZE, THREAD_SIZE)
+ .rela.dyn : ALIGN(8) {
+ __rela_dyn_begin = .;
+ *(.rela.dyn) *(.rela*)
+ __rela_dyn_end = .;
+ }
+
.sdata : {
*(.sdata)
}
@@ -133,6 +148,7 @@ SECTIONS
DISCARDS
/DISCARD/ : {
+ *(.dynamic .dynsym .dynstr .hash .gnu.hash)
*(.gnu.attributes)
*(.options)
*(.eh_frame)