diff options
| -rw-r--r-- | arch/arm64/Kconfig | 11 | ||||
| -rw-r--r-- | arch/arm64/Makefile | 4 | ||||
| -rw-r--r-- | arch/arm64/include/asm/elf.h | 2 | ||||
| -rw-r--r-- | arch/arm64/kernel/head.S | 32 | ||||
| -rw-r--r-- | arch/arm64/kernel/vmlinux.lds.S | 16 |
5 files changed, 65 insertions, 0 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index c85c29d..fef3dc6 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -787,6 +787,17 @@ config ARM64_MODULE_PLTS select ARM64_MODULE_CMODEL_LARGE select HAVE_MOD_ARCH_SPECIFIC +config RELOCATABLE + bool + help + This builds the kernel as a Position Independent Executable (PIE), + which retains all relocation metadata required to relocate the + kernel binary at runtime to a different virtual address than the + address it was linked at. + Since AArch64 uses the RELA relocation format, this requires a + relocation pass at runtime even if the kernel is loaded at the + same address it was linked at. + endmenu menu "Boot options" diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index a6bba96..6b5508a 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -15,6 +15,10 @@ CPPFLAGS_vmlinux.lds = -DTEXT_OFFSET=$(TEXT_OFFSET) OBJCOPYFLAGS :=-O binary -R .note -R .note.gnu.build-id -R .comment -S GZFLAGS :=-9 +ifneq ($(CONFIG_RELOCATABLE),) +LDFLAGS_vmlinux += -pie +endif + KBUILD_DEFCONFIG := defconfig # Check for binutils support for specific extensions diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h index 435f559..24ed037 100644 --- a/arch/arm64/include/asm/elf.h +++ b/arch/arm64/include/asm/elf.h @@ -77,6 +77,8 @@ #define R_AARCH64_MOVW_PREL_G2_NC 292 #define R_AARCH64_MOVW_PREL_G3 293 +#define R_AARCH64_RELATIVE 1027 + /* * These are used to set parameters in the core dumps. */ diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 4cad8f9..4e69412 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -29,6 +29,7 @@ #include <asm/asm-offsets.h> #include <asm/cache.h> #include <asm/cputype.h> +#include <asm/elf.h> #include <asm/kernel-pgtable.h> #include <asm/memory.h> #include <asm/pgtable-hwdef.h> @@ -432,6 +433,37 @@ __mmap_switched: bl __pi_memset dsb ishst // Make zero page visible to PTW +#ifdef CONFIG_RELOCATABLE + + /* + * Iterate over each entry in the relocation table, and apply the + * relocations in place. + */ + adr_l x8, __dynsym_start // start of symbol table + adr_l x9, __reloc_start // start of reloc table + adr_l x10, __reloc_end // end of reloc table + +0: cmp x9, x10 + b.hs 2f + ldp x11, x12, [x9], #24 + ldr x13, [x9, #-8] + cmp w12, #R_AARCH64_RELATIVE + b.ne 1f + str x13, [x11] + b 0b + +1: cmp w12, #R_AARCH64_ABS64 + b.ne 0b + add x12, x12, x12, lsl #1 // symtab offset: 24x top word + add x12, x8, x12, lsr #(32 - 3) // ... shifted into bottom word + ldr x15, [x12, #8] // Elf64_Sym::st_value + add x15, x13, x15 + str x15, [x11] + b 0b + +2: +#endif + adr_l sp, initial_sp, x4 mov x4, sp and x4, x4, #~(THREAD_SIZE - 1) diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 282e3e6..e3f6cd7 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -87,6 +87,7 @@ SECTIONS EXIT_CALL *(.discard) *(.discard.*) + *(.interp .dynamic) } . = KIMAGE_VADDR + TEXT_OFFSET; @@ -149,6 +150,21 @@ SECTIONS .altinstr_replacement : { *(.altinstr_replacement) } + .rela : ALIGN(8) { + __reloc_start = .; + *(.rela .rela*) + __reloc_end = .; + } + .dynsym : ALIGN(8) { + __dynsym_start = .; + *(.dynsym) + } + .dynstr : { + *(.dynstr) + } + .hash : { + *(.hash) + } . = ALIGN(PAGE_SIZE); __init_end = .; |
