From 805bc0bc238f7209fca5e39c152b0d3c12046ac9 Mon Sep 17 00:00:00 2001 From: Gerald Schaefer Date: Sun, 3 Feb 2019 21:35:45 +0100 Subject: [PATCH] s390/kernel: build a relocatable kernel This patch adds support for building a relocatable kernel with -fPIE. The kernel will be relocated to 0 early in the boot process. Signed-off-by: Gerald Schaefer Reviewed-by: Philipp Rudo Signed-off-by: Martin Schwidefsky --- arch/s390/Kconfig | 13 ++++++ arch/s390/Makefile | 4 ++ arch/s390/boot/Makefile | 1 + arch/s390/boot/compressed/decompressor.h | 3 ++ arch/s390/boot/machine_kexec_reloc.c | 2 + arch/s390/boot/startup.c | 27 ++++++++++++ arch/s390/include/asm/kexec.h | 2 + arch/s390/kernel/Makefile | 2 +- arch/s390/kernel/machine_kexec_file.c | 44 ++------------------ arch/s390/kernel/machine_kexec_reloc.c | 53 ++++++++++++++++++++++++ arch/s390/kernel/vmlinux.lds.S | 15 +++++++ 11 files changed, 124 insertions(+), 42 deletions(-) create mode 100644 arch/s390/boot/machine_kexec_reloc.c create mode 100644 arch/s390/kernel/machine_kexec_reloc.c diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig index 21e851b0a989..4c99e4f5f366 100644 --- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -624,6 +624,19 @@ config EXPOLINE_FULL endchoice +config RELOCATABLE + bool "Build a relocatable kernel" + select MODULE_REL_CRCS if MODVERSIONS + default y + help + This builds a kernel image that retains relocation information + so it can be loaded at an arbitrary address. + The kernel is linked as a position-independent executable (PIE) + and contains dynamic relocations which are processed early in the + bootup process. + The relocations make the kernel image about 15% larger (compressed + 10%), but are discarded at runtime. + endmenu menu "Memory setup" diff --git a/arch/s390/Makefile b/arch/s390/Makefile index 9c079a506325..54b8a12d64e8 100644 --- a/arch/s390/Makefile +++ b/arch/s390/Makefile @@ -16,6 +16,10 @@ KBUILD_AFLAGS_MODULE += -fPIC KBUILD_CFLAGS_MODULE += -fPIC KBUILD_AFLAGS += -m64 KBUILD_CFLAGS += -m64 +ifeq ($(CONFIG_RELOCATABLE),y) +KBUILD_CFLAGS += -fPIE +LDFLAGS_vmlinux := -pie +endif aflags_dwarf := -Wa,-gdwarf-2 KBUILD_AFLAGS_DECOMPRESSOR := -m64 -D__ASSEMBLY__ KBUILD_AFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),$(aflags_dwarf)) diff --git a/arch/s390/boot/Makefile b/arch/s390/boot/Makefile index c1993c57300f..4df43e83363a 100644 --- a/arch/s390/boot/Makefile +++ b/arch/s390/boot/Makefile @@ -32,6 +32,7 @@ obj-y := head.o als.o startup.o mem_detect.o ipl_parm.o ipl_report.o obj-y += string.o ebcdic.o sclp_early_core.o mem.o ipl_vmparm.o cmdline.o obj-y += ctype.o obj-$(CONFIG_PROTECTED_VIRTUALIZATION_GUEST) += uv.o +obj-$(CONFIG_RELOCATABLE) += machine_kexec_reloc.o targets := bzImage startup.a section_cmp.boot.data section_cmp.boot.preserved.data $(obj-y) subdir- := compressed diff --git a/arch/s390/boot/compressed/decompressor.h b/arch/s390/boot/compressed/decompressor.h index 424cf524aac1..c15eb7114d83 100644 --- a/arch/s390/boot/compressed/decompressor.h +++ b/arch/s390/boot/compressed/decompressor.h @@ -19,6 +19,9 @@ struct vmlinux_info { unsigned long bootdata_size; unsigned long bootdata_preserved_off; unsigned long bootdata_preserved_size; + unsigned long dynsym_start; + unsigned long rela_dyn_start; + unsigned long rela_dyn_end; }; extern char _vmlinux_info[]; diff --git a/arch/s390/boot/machine_kexec_reloc.c b/arch/s390/boot/machine_kexec_reloc.c new file mode 100644 index 000000000000..b7a5d0f72097 --- /dev/null +++ b/arch/s390/boot/machine_kexec_reloc.c @@ -0,0 +1,2 @@ +// SPDX-License-Identifier: GPL-2.0 +#include "../kernel/machine_kexec_reloc.c" diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c index 90898976a941..b7d6a76cb5e9 100644 --- a/arch/s390/boot/startup.c +++ b/arch/s390/boot/startup.c @@ -1,6 +1,8 @@ // SPDX-License-Identifier: GPL-2.0 #include +#include #include +#include #include #include #include "compressed/decompressor.h" @@ -47,6 +49,29 @@ static void copy_bootdata(void) memcpy((void *)vmlinux.bootdata_preserved_off, __boot_data_preserved_start, vmlinux.bootdata_preserved_size); } +static void handle_relocs(unsigned long offset) +{ + Elf64_Rela *rela_start, *rela_end, *rela; + int r_type, r_sym, rc; + Elf64_Addr loc, val; + Elf64_Sym *dynsym; + + rela_start = (Elf64_Rela *) vmlinux.rela_dyn_start; + rela_end = (Elf64_Rela *) vmlinux.rela_dyn_end; + dynsym = (Elf64_Sym *) vmlinux.dynsym_start; + for (rela = rela_start; rela < rela_end; rela++) { + loc = rela->r_offset + offset; + val = rela->r_addend + offset; + r_sym = ELF64_R_SYM(rela->r_info); + if (r_sym) + val += dynsym[r_sym].st_value; + r_type = ELF64_R_TYPE(rela->r_info); + rc = arch_kexec_do_relocs(r_type, (void *) loc, val, 0); + if (rc) + error("Unknown relocation type"); + } +} + void startup_kernel(void) { unsigned long safe_addr; @@ -67,5 +92,7 @@ void startup_kernel(void) memmove((void *)vmlinux.default_lma, img, vmlinux.image_size); } copy_bootdata(); + if (IS_ENABLED(CONFIG_RELOCATABLE)) + handle_relocs(0); vmlinux.entry(); } diff --git a/arch/s390/include/asm/kexec.h b/arch/s390/include/asm/kexec.h index 305d3465574f..ea398a05f643 100644 --- a/arch/s390/include/asm/kexec.h +++ b/arch/s390/include/asm/kexec.h @@ -71,6 +71,8 @@ int s390_verify_sig(const char *kernel, unsigned long kernel_len); void *kexec_file_add_components(struct kimage *image, int (*add_kernel)(struct kimage *image, struct s390_load_data *data)); +int arch_kexec_do_relocs(int r_type, void *loc, unsigned long val, + unsigned long addr); extern const struct kexec_file_ops s390_kexec_image_ops; extern const struct kexec_file_ops s390_kexec_elf_ops; diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile index d28acd7ba81e..19425605a83d 100644 --- a/arch/s390/kernel/Makefile +++ b/arch/s390/kernel/Makefile @@ -51,7 +51,7 @@ obj-y += debug.o irq.o ipl.o dis.o diag.o vdso.o early_nobss.o obj-y += sysinfo.o lgr.o os_info.o machine_kexec.o pgm_check.o obj-y += runtime_instr.o cache.o fpu.o dumpstack.o guarded_storage.o sthyi.o obj-y += entry.o reipl.o relocate_kernel.o kdebugfs.o alternative.o -obj-y += nospec-branch.o ipl_vmparm.o +obj-y += nospec-branch.o ipl_vmparm.o machine_kexec_reloc.o extra-y += head64.o vmlinux.lds diff --git a/arch/s390/kernel/machine_kexec_file.c b/arch/s390/kernel/machine_kexec_file.c index 48cab9600ed9..42c23a5c8229 100644 --- a/arch/s390/kernel/machine_kexec_file.c +++ b/arch/s390/kernel/machine_kexec_file.c @@ -290,7 +290,7 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi, const Elf_Shdr *symtab) { Elf_Rela *relas; - int i; + int i, r_type; relas = (void *)pi->ehdr + relsec->sh_offset; @@ -324,46 +324,8 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi, addr = section->sh_addr + relas[i].r_offset; - switch (ELF64_R_TYPE(relas[i].r_info)) { - case R_390_8: /* Direct 8 bit. */ - *(u8 *)loc = val; - break; - case R_390_12: /* Direct 12 bit. */ - *(u16 *)loc &= 0xf000; - *(u16 *)loc |= val & 0xfff; - break; - case R_390_16: /* Direct 16 bit. */ - *(u16 *)loc = val; - break; - case R_390_20: /* Direct 20 bit. */ - *(u32 *)loc &= 0xf00000ff; - *(u32 *)loc |= (val & 0xfff) << 16; /* DL */ - *(u32 *)loc |= (val & 0xff000) >> 4; /* DH */ - break; - case R_390_32: /* Direct 32 bit. */ - *(u32 *)loc = val; - break; - case R_390_64: /* Direct 64 bit. */ - *(u64 *)loc = val; - break; - case R_390_PC16: /* PC relative 16 bit. */ - *(u16 *)loc = (val - addr); - break; - case R_390_PC16DBL: /* PC relative 16 bit shifted by 1. */ - *(u16 *)loc = (val - addr) >> 1; - break; - case R_390_PC32DBL: /* PC relative 32 bit shifted by 1. */ - *(u32 *)loc = (val - addr) >> 1; - break; - case R_390_PC32: /* PC relative 32 bit. */ - *(u32 *)loc = (val - addr); - break; - case R_390_PC64: /* PC relative 64 bit. */ - *(u64 *)loc = (val - addr); - break; - default: - break; - } + r_type = ELF64_R_TYPE(relas[i].r_info); + arch_kexec_do_relocs(r_type, loc, val, addr); } return 0; } diff --git a/arch/s390/kernel/machine_kexec_reloc.c b/arch/s390/kernel/machine_kexec_reloc.c new file mode 100644 index 000000000000..1dded39239f8 --- /dev/null +++ b/arch/s390/kernel/machine_kexec_reloc.c @@ -0,0 +1,53 @@ +// SPDX-License-Identifier: GPL-2.0 +#include + +int arch_kexec_do_relocs(int r_type, void *loc, unsigned long val, + unsigned long addr) +{ + switch (r_type) { + case R_390_NONE: + break; + case R_390_8: /* Direct 8 bit. */ + *(u8 *)loc = val; + break; + case R_390_12: /* Direct 12 bit. */ + *(u16 *)loc &= 0xf000; + *(u16 *)loc |= val & 0xfff; + break; + case R_390_16: /* Direct 16 bit. */ + *(u16 *)loc = val; + break; + case R_390_20: /* Direct 20 bit. */ + *(u32 *)loc &= 0xf00000ff; + *(u32 *)loc |= (val & 0xfff) << 16; /* DL */ + *(u32 *)loc |= (val & 0xff000) >> 4; /* DH */ + break; + case R_390_32: /* Direct 32 bit. */ + *(u32 *)loc = val; + break; + case R_390_64: /* Direct 64 bit. */ + *(u64 *)loc = val; + break; + case R_390_PC16: /* PC relative 16 bit. */ + *(u16 *)loc = (val - addr); + break; + case R_390_PC16DBL: /* PC relative 16 bit shifted by 1. */ + *(u16 *)loc = (val - addr) >> 1; + break; + case R_390_PC32DBL: /* PC relative 32 bit shifted by 1. */ + *(u32 *)loc = (val - addr) >> 1; + break; + case R_390_PC32: /* PC relative 32 bit. */ + *(u32 *)loc = (val - addr); + break; + case R_390_PC64: /* PC relative 64 bit. */ + *(u64 *)loc = (val - addr); + break; + case R_390_RELATIVE: + *(unsigned long *) loc = val; + break; + default: + return 1; + } + return 0; +} diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S index 6ef9c62bb01b..49d55327de0b 100644 --- a/arch/s390/kernel/vmlinux.lds.S +++ b/arch/s390/kernel/vmlinux.lds.S @@ -144,6 +144,18 @@ SECTIONS INIT_DATA_SECTION(0x100) PERCPU_SECTION(0x100) + + .dynsym ALIGN(8) : { + __dynsym_start = .; + *(.dynsym) + __dynsym_end = .; + } + .rela.dyn ALIGN(8) : { + __rela_dyn_start = .; + *(.rela*) + __rela_dyn_end = .; + } + . = ALIGN(PAGE_SIZE); __init_end = .; /* freed after init ends here */ @@ -165,6 +177,9 @@ SECTIONS QUAD(__boot_data_preserved_start) /* bootdata_preserved_off */ QUAD(__boot_data_preserved_end - __boot_data_preserved_start) /* bootdata_preserved_size */ + QUAD(__dynsym_start) /* dynsym_start */ + QUAD(__rela_dyn_start) /* rela_dyn_start */ + QUAD(__rela_dyn_end) /* rela_dyn_end */ } :NONE /* Debugging sections. */