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linux/arch/s390/kernel/module.c
Martin Schwidefsky 57d7f939e7 s390: add no-execute support 
Bit 0x100 of a page table, segment table of region table entry
can be used to disallow code execution for the virtual addresses
associated with the entry.

There is one tricky bit, the system call to return from a signal
is part of the signal frame written to the user stack. With a
non-executable stack this would stop working. To avoid breaking
things the protection fault handler checks the opcode that caused
the fault for 0x0a77 (sys_sigreturn) and 0x0aad (sys_rt_sigreturn)
and injects a system call. This is preferable to the alternative
solution with a stub function in the vdso because it works for
vdso=off and statically linked binaries as well.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2017-02-08 14:13:25 +01:00

435 lines
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/*
* Kernel module help for s390.
*
* S390 version
* Copyright IBM Corp. 2002, 2003
* Author(s): Arnd Bergmann (arndb@de.ibm.com)
* Martin Schwidefsky (schwidefsky@de.ibm.com)
*
* based on i386 version
* Copyright (C) 2001 Rusty Russell.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <linux/module.h>
#include <linux/elf.h>
#include <linux/vmalloc.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/moduleloader.h>
#include <linux/bug.h>
#if 0
#define DEBUGP printk
#else
#define DEBUGP(fmt , ...)
#endif
#define PLT_ENTRY_SIZE 20
void *module_alloc(unsigned long size)
{
if (PAGE_ALIGN(size) > MODULES_LEN)
return NULL;
return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
GFP_KERNEL, PAGE_KERNEL_EXEC,
0, NUMA_NO_NODE,
__builtin_return_address(0));
}
void module_arch_freeing_init(struct module *mod)
{
if (is_livepatch_module(mod) &&
mod->state == MODULE_STATE_LIVE)
return;
vfree(mod->arch.syminfo);
mod->arch.syminfo = NULL;
}
static void check_rela(Elf_Rela *rela, struct module *me)
{
struct mod_arch_syminfo *info;
info = me->arch.syminfo + ELF_R_SYM (rela->r_info);
switch (ELF_R_TYPE (rela->r_info)) {
case R_390_GOT12: /* 12 bit GOT offset. */
case R_390_GOT16: /* 16 bit GOT offset. */
case R_390_GOT20: /* 20 bit GOT offset. */
case R_390_GOT32: /* 32 bit GOT offset. */
case R_390_GOT64: /* 64 bit GOT offset. */
case R_390_GOTENT: /* 32 bit PC rel. to GOT entry shifted by 1. */
case R_390_GOTPLT12: /* 12 bit offset to jump slot. */
case R_390_GOTPLT16: /* 16 bit offset to jump slot. */
case R_390_GOTPLT20: /* 20 bit offset to jump slot. */
case R_390_GOTPLT32: /* 32 bit offset to jump slot. */
case R_390_GOTPLT64: /* 64 bit offset to jump slot. */
case R_390_GOTPLTENT: /* 32 bit rel. offset to jump slot >> 1. */
if (info->got_offset == -1UL) {
info->got_offset = me->arch.got_size;
me->arch.got_size += sizeof(void*);
}
break;
case R_390_PLT16DBL: /* 16 bit PC rel. PLT shifted by 1. */
case R_390_PLT32DBL: /* 32 bit PC rel. PLT shifted by 1. */
case R_390_PLT32: /* 32 bit PC relative PLT address. */
case R_390_PLT64: /* 64 bit PC relative PLT address. */
case R_390_PLTOFF16: /* 16 bit offset from GOT to PLT. */
case R_390_PLTOFF32: /* 32 bit offset from GOT to PLT. */
case R_390_PLTOFF64: /* 16 bit offset from GOT to PLT. */
if (info->plt_offset == -1UL) {
info->plt_offset = me->arch.plt_size;
me->arch.plt_size += PLT_ENTRY_SIZE;
}
break;
case R_390_COPY:
case R_390_GLOB_DAT:
case R_390_JMP_SLOT:
case R_390_RELATIVE:
/* Only needed if we want to support loading of
modules linked with -shared. */
break;
}
}
/*
* Account for GOT and PLT relocations. We can't add sections for
* got and plt but we can increase the core module size.
*/
int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs,
char *secstrings, struct module *me)
{
Elf_Shdr *symtab;
Elf_Sym *symbols;
Elf_Rela *rela;
char *strings;
int nrela, i, j;
/* Find symbol table and string table. */
symtab = NULL;
for (i = 0; i < hdr->e_shnum; i++)
switch (sechdrs[i].sh_type) {
case SHT_SYMTAB:
symtab = sechdrs + i;
break;
}
if (!symtab) {
printk(KERN_ERR "module %s: no symbol table\n", me->name);
return -ENOEXEC;
}
/* Allocate one syminfo structure per symbol. */
me->arch.nsyms = symtab->sh_size / sizeof(Elf_Sym);
me->arch.syminfo = vmalloc(me->arch.nsyms *
sizeof(struct mod_arch_syminfo));
if (!me->arch.syminfo)
return -ENOMEM;
symbols = (void *) hdr + symtab->sh_offset;
strings = (void *) hdr + sechdrs[symtab->sh_link].sh_offset;
for (i = 0; i < me->arch.nsyms; i++) {
if (symbols[i].st_shndx == SHN_UNDEF &&
strcmp(strings + symbols[i].st_name,
"_GLOBAL_OFFSET_TABLE_") == 0)
/* "Define" it as absolute. */
symbols[i].st_shndx = SHN_ABS;
me->arch.syminfo[i].got_offset = -1UL;
me->arch.syminfo[i].plt_offset = -1UL;
me->arch.syminfo[i].got_initialized = 0;
me->arch.syminfo[i].plt_initialized = 0;
}
/* Search for got/plt relocations. */
me->arch.got_size = me->arch.plt_size = 0;
for (i = 0; i < hdr->e_shnum; i++) {
if (sechdrs[i].sh_type != SHT_RELA)
continue;
nrela = sechdrs[i].sh_size / sizeof(Elf_Rela);
rela = (void *) hdr + sechdrs[i].sh_offset;
for (j = 0; j < nrela; j++)
check_rela(rela + j, me);
}
/* Increase core size by size of got & plt and set start
offsets for got and plt. */
me->core_layout.size = ALIGN(me->core_layout.size, 4);
me->arch.got_offset = me->core_layout.size;
me->core_layout.size += me->arch.got_size;
me->arch.plt_offset = me->core_layout.size;
me->core_layout.size += me->arch.plt_size;
return 0;
}
static int apply_rela_bits(Elf_Addr loc, Elf_Addr val,
int sign, int bits, int shift)
{
unsigned long umax;
long min, max;
if (val & ((1UL << shift) - 1))
return -ENOEXEC;
if (sign) {
val = (Elf_Addr)(((long) val) >> shift);
min = -(1L << (bits - 1));
max = (1L << (bits - 1)) - 1;
if ((long) val < min || (long) val > max)
return -ENOEXEC;
} else {
val >>= shift;
umax = ((1UL << (bits - 1)) << 1) - 1;
if ((unsigned long) val > umax)
return -ENOEXEC;
}
if (bits == 8)
*(unsigned char *) loc = val;
else if (bits == 12)
*(unsigned short *) loc = (val & 0xfff) |
(*(unsigned short *) loc & 0xf000);
else if (bits == 16)
*(unsigned short *) loc = val;
else if (bits == 20)
*(unsigned int *) loc = (val & 0xfff) << 16 |
(val & 0xff000) >> 4 |
(*(unsigned int *) loc & 0xf00000ff);
else if (bits == 32)
*(unsigned int *) loc = val;
else if (bits == 64)
*(unsigned long *) loc = val;
return 0;
}
static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,
const char *strtab, struct module *me)
{
struct mod_arch_syminfo *info;
Elf_Addr loc, val;
int r_type, r_sym;
int rc = -ENOEXEC;
/* This is where to make the change */
loc = base + rela->r_offset;
/* This is the symbol it is referring to. Note that all
undefined symbols have been resolved. */
r_sym = ELF_R_SYM(rela->r_info);
r_type = ELF_R_TYPE(rela->r_info);
info = me->arch.syminfo + r_sym;
val = symtab[r_sym].st_value;
switch (r_type) {
case R_390_NONE: /* No relocation. */
rc = 0;
break;
case R_390_8: /* Direct 8 bit. */
case R_390_12: /* Direct 12 bit. */
case R_390_16: /* Direct 16 bit. */
case R_390_20: /* Direct 20 bit. */
case R_390_32: /* Direct 32 bit. */
case R_390_64: /* Direct 64 bit. */
val += rela->r_addend;
if (r_type == R_390_8)
rc = apply_rela_bits(loc, val, 0, 8, 0);
else if (r_type == R_390_12)
rc = apply_rela_bits(loc, val, 0, 12, 0);
else if (r_type == R_390_16)
rc = apply_rela_bits(loc, val, 0, 16, 0);
else if (r_type == R_390_20)
rc = apply_rela_bits(loc, val, 1, 20, 0);
else if (r_type == R_390_32)
rc = apply_rela_bits(loc, val, 0, 32, 0);
else if (r_type == R_390_64)
rc = apply_rela_bits(loc, val, 0, 64, 0);
break;
case R_390_PC16: /* PC relative 16 bit. */
case R_390_PC16DBL: /* PC relative 16 bit shifted by 1. */
case R_390_PC32DBL: /* PC relative 32 bit shifted by 1. */
case R_390_PC32: /* PC relative 32 bit. */
case R_390_PC64: /* PC relative 64 bit. */
val += rela->r_addend - loc;
if (r_type == R_390_PC16)
rc = apply_rela_bits(loc, val, 1, 16, 0);
else if (r_type == R_390_PC16DBL)
rc = apply_rela_bits(loc, val, 1, 16, 1);
else if (r_type == R_390_PC32DBL)
rc = apply_rela_bits(loc, val, 1, 32, 1);
else if (r_type == R_390_PC32)
rc = apply_rela_bits(loc, val, 1, 32, 0);
else if (r_type == R_390_PC64)
rc = apply_rela_bits(loc, val, 1, 64, 0);
break;
case R_390_GOT12: /* 12 bit GOT offset. */
case R_390_GOT16: /* 16 bit GOT offset. */
case R_390_GOT20: /* 20 bit GOT offset. */
case R_390_GOT32: /* 32 bit GOT offset. */
case R_390_GOT64: /* 64 bit GOT offset. */
case R_390_GOTENT: /* 32 bit PC rel. to GOT entry shifted by 1. */
case R_390_GOTPLT12: /* 12 bit offset to jump slot. */
case R_390_GOTPLT20: /* 20 bit offset to jump slot. */
case R_390_GOTPLT16: /* 16 bit offset to jump slot. */
case R_390_GOTPLT32: /* 32 bit offset to jump slot. */
case R_390_GOTPLT64: /* 64 bit offset to jump slot. */
case R_390_GOTPLTENT: /* 32 bit rel. offset to jump slot >> 1. */
if (info->got_initialized == 0) {
Elf_Addr *gotent;
gotent = me->core_layout.base + me->arch.got_offset +
info->got_offset;
*gotent = val;
info->got_initialized = 1;
}
val = info->got_offset + rela->r_addend;
if (r_type == R_390_GOT12 ||
r_type == R_390_GOTPLT12)
rc = apply_rela_bits(loc, val, 0, 12, 0);
else if (r_type == R_390_GOT16 ||
r_type == R_390_GOTPLT16)
rc = apply_rela_bits(loc, val, 0, 16, 0);
else if (r_type == R_390_GOT20 ||
r_type == R_390_GOTPLT20)
rc = apply_rela_bits(loc, val, 1, 20, 0);
else if (r_type == R_390_GOT32 ||
r_type == R_390_GOTPLT32)
rc = apply_rela_bits(loc, val, 0, 32, 0);
else if (r_type == R_390_GOT64 ||
r_type == R_390_GOTPLT64)
rc = apply_rela_bits(loc, val, 0, 64, 0);
else if (r_type == R_390_GOTENT ||
r_type == R_390_GOTPLTENT) {
val += (Elf_Addr) me->core_layout.base - loc;
rc = apply_rela_bits(loc, val, 1, 32, 1);
}
break;
case R_390_PLT16DBL: /* 16 bit PC rel. PLT shifted by 1. */
case R_390_PLT32DBL: /* 32 bit PC rel. PLT shifted by 1. */
case R_390_PLT32: /* 32 bit PC relative PLT address. */
case R_390_PLT64: /* 64 bit PC relative PLT address. */
case R_390_PLTOFF16: /* 16 bit offset from GOT to PLT. */
case R_390_PLTOFF32: /* 32 bit offset from GOT to PLT. */
case R_390_PLTOFF64: /* 16 bit offset from GOT to PLT. */
if (info->plt_initialized == 0) {
unsigned int *ip;
ip = me->core_layout.base + me->arch.plt_offset +
info->plt_offset;
ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */
ip[1] = 0x100a0004;
ip[2] = 0x07f10000;
ip[3] = (unsigned int) (val >> 32);
ip[4] = (unsigned int) val;
info->plt_initialized = 1;
}
if (r_type == R_390_PLTOFF16 ||
r_type == R_390_PLTOFF32 ||
r_type == R_390_PLTOFF64)
val = me->arch.plt_offset - me->arch.got_offset +
info->plt_offset + rela->r_addend;
else {
if (!((r_type == R_390_PLT16DBL &&
val - loc + 0xffffUL < 0x1ffffeUL) ||
(r_type == R_390_PLT32DBL &&
val - loc + 0xffffffffULL < 0x1fffffffeULL)))
val = (Elf_Addr) me->core_layout.base +
me->arch.plt_offset +
info->plt_offset;
val += rela->r_addend - loc;
}
if (r_type == R_390_PLT16DBL)
rc = apply_rela_bits(loc, val, 1, 16, 1);
else if (r_type == R_390_PLTOFF16)
rc = apply_rela_bits(loc, val, 0, 16, 0);
else if (r_type == R_390_PLT32DBL)
rc = apply_rela_bits(loc, val, 1, 32, 1);
else if (r_type == R_390_PLT32 ||
r_type == R_390_PLTOFF32)
rc = apply_rela_bits(loc, val, 0, 32, 0);
else if (r_type == R_390_PLT64 ||
r_type == R_390_PLTOFF64)
rc = apply_rela_bits(loc, val, 0, 64, 0);
break;
case R_390_GOTOFF16: /* 16 bit offset to GOT. */
case R_390_GOTOFF32: /* 32 bit offset to GOT. */
case R_390_GOTOFF64: /* 64 bit offset to GOT. */
val = val + rela->r_addend -
((Elf_Addr) me->core_layout.base + me->arch.got_offset);
if (r_type == R_390_GOTOFF16)
rc = apply_rela_bits(loc, val, 0, 16, 0);
else if (r_type == R_390_GOTOFF32)
rc = apply_rela_bits(loc, val, 0, 32, 0);
else if (r_type == R_390_GOTOFF64)
rc = apply_rela_bits(loc, val, 0, 64, 0);
break;
case R_390_GOTPC: /* 32 bit PC relative offset to GOT. */
case R_390_GOTPCDBL: /* 32 bit PC rel. off. to GOT shifted by 1. */
val = (Elf_Addr) me->core_layout.base + me->arch.got_offset +
rela->r_addend - loc;
if (r_type == R_390_GOTPC)
rc = apply_rela_bits(loc, val, 1, 32, 0);
else if (r_type == R_390_GOTPCDBL)
rc = apply_rela_bits(loc, val, 1, 32, 1);
break;
case R_390_COPY:
case R_390_GLOB_DAT: /* Create GOT entry. */
case R_390_JMP_SLOT: /* Create PLT entry. */
case R_390_RELATIVE: /* Adjust by program base. */
/* Only needed if we want to support loading of
modules linked with -shared. */
return -ENOEXEC;
default:
printk(KERN_ERR "module %s: unknown relocation: %u\n",
me->name, r_type);
return -ENOEXEC;
}
if (rc) {
printk(KERN_ERR "module %s: relocation error for symbol %s "
"(r_type %i, value 0x%lx)\n",
me->name, strtab + symtab[r_sym].st_name,
r_type, (unsigned long) val);
return rc;
}
return 0;
}
int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
unsigned int symindex, unsigned int relsec,
struct module *me)
{
Elf_Addr base;
Elf_Sym *symtab;
Elf_Rela *rela;
unsigned long i, n;
int rc;
DEBUGP("Applying relocate section %u to %u\n",
relsec, sechdrs[relsec].sh_info);
base = sechdrs[sechdrs[relsec].sh_info].sh_addr;
symtab = (Elf_Sym *) sechdrs[symindex].sh_addr;
rela = (Elf_Rela *) sechdrs[relsec].sh_addr;
n = sechdrs[relsec].sh_size / sizeof(Elf_Rela);
for (i = 0; i < n; i++, rela++) {
rc = apply_rela(rela, base, symtab, strtab, me);
if (rc)
return rc;
}
return 0;
}
int module_finalize(const Elf_Ehdr *hdr,
const Elf_Shdr *sechdrs,
struct module *me)
{
jump_label_apply_nops(me);
return 0;
}
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