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linux_dsm_epyc7002/arch/s390/kernel/module.c
Martin Schwidefsky f19fbd5ed6 s390: introduce execute-trampolines for branches 
Add CONFIG_EXPOLINE to enable the use of the new -mindirect-branch= and
-mfunction_return= compiler options to create a kernel fortified against
the specte v2 attack.

With CONFIG_EXPOLINE=y all indirect branches will be issued with an
execute type instruction. For z10 or newer the EXRL instruction will
be used, for older machines the EX instruction. The typical indirect
call

	basr	%r14,%r1

is replaced with a PC relative call to a new thunk

	brasl	%r14,__s390x_indirect_jump_r1

The thunk contains the EXRL/EX instruction to the indirect branch

__s390x_indirect_jump_r1:
	exrl	0,0f
	j	.
0:	br	%r1

The detour via the execute type instruction has a performance impact.
To get rid of the detour the new kernel parameter "nospectre_v2" and
"spectre_v2=[on,off,auto]" can be used. If the parameter is specified
the kernel and module code will be patched at runtime.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2018-02-07 15:57:02 +01:00

480 lines
15 KiB
C
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// SPDX-License-Identifier: GPL-2.0+
/*
* 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.
*/
#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>
#include <asm/alternative.h>
#include <asm/nospec-branch.h>
#include <asm/facility.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;
if (me->arch.plt_size) {
if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_call_disable)
me->arch.plt_size += PLT_ENTRY_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 */
ip[1] = 0x100a0004; /* lg 1,10(1) */
if (IS_ENABLED(CONFIG_EXPOLINE) &&
!nospec_call_disable) {
unsigned int *ij;
ij = me->core_layout.base +
me->arch.plt_offset +
me->arch.plt_size - PLT_ENTRY_SIZE;
ip[2] = 0xa7f40000 + /* j __jump_r1 */
(unsigned int)(u16)
(((unsigned long) ij - 8 -
(unsigned long) ip) / 2);
} else {
ip[2] = 0x07f10000; /* br %r1 */
}
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)
{
const Elf_Shdr *s;
char *secstrings, *secname;
void *aseg;
if (IS_ENABLED(CONFIG_EXPOLINE) &&
!nospec_call_disable && me->arch.plt_size) {
unsigned int *ij;
ij = me->core_layout.base + me->arch.plt_offset +
me->arch.plt_size - PLT_ENTRY_SIZE;
if (test_facility(35)) {
ij[0] = 0xc6000000; /* exrl %r0,.+10 */
ij[1] = 0x0005a7f4; /* j . */
ij[2] = 0x000007f1; /* br %r1 */
} else {
ij[0] = 0x44000000 | (unsigned int)
offsetof(struct lowcore, br_r1_trampoline);
ij[1] = 0xa7f40000; /* j . */
}
}
secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
aseg = (void *) s->sh_addr;
secname = secstrings + s->sh_name;
if (!strcmp(".altinstructions", secname))
/* patch .altinstructions */
apply_alternatives(aseg, aseg + s->sh_size);
if (IS_ENABLED(CONFIG_EXPOLINE) &&
(!strcmp(".nospec_call_table", secname)))
nospec_call_revert(aseg, aseg + s->sh_size);
if (IS_ENABLED(CONFIG_EXPOLINE) &&
(!strcmp(".nospec_return_table", secname)))
nospec_return_revert(aseg, aseg + s->sh_size);
}
jump_label_apply_nops(me);
return 0;
}
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