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s390/kernel: build a relocatable kernel

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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 <gerald.schaefer@de.ibm.com>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Gerald Schaefer
2019-02-03 21:35:45 +01:00
committed by Martin Schwidefsky
parent 833b441ec0
commit 805bc0bc23
11 changed files with 124 additions and 42 deletions
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2
arch/s390/kernel/Makefile
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@@ -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

44
arch/s390/kernel/machine_kexec_file.c
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@@ -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;
}

53
arch/s390/kernel/machine_kexec_reloc.c Normal file
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@@ -0,0 +1,53 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/elf.h>
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;
}

15
arch/s390/kernel/vmlinux.lds.S
View File

@@ -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. */