linux/tools/objtool/special.c
Thomas Gleixner 1ccea77e2a treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 13
Based on 2 normalized pattern(s):

  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 see http www gnu org licenses

  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 [based]
  [from] [clk] [highbank] [c] you should have received a copy of the
  gnu general public license along with this program if not see http
  www gnu org licenses

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 355 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Jilayne Lovejoy <opensource@jilayne.com>
Reviewed-by: Steve Winslow <swinslow@gmail.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190519154041.837383322@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-21 11:28:45 +02:00

200 lines
4.5 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
*/
/*
* This file reads all the special sections which have alternate instructions
* which can be patched in or redirected to at runtime.
*/
#include <stdlib.h>
#include <string.h>
#include "builtin.h"
#include "special.h"
#include "warn.h"
#define EX_ENTRY_SIZE 12
#define EX_ORIG_OFFSET 0
#define EX_NEW_OFFSET 4
#define JUMP_ENTRY_SIZE 16
#define JUMP_ORIG_OFFSET 0
#define JUMP_NEW_OFFSET 4
#define ALT_ENTRY_SIZE 13
#define ALT_ORIG_OFFSET 0
#define ALT_NEW_OFFSET 4
#define ALT_FEATURE_OFFSET 8
#define ALT_ORIG_LEN_OFFSET 10
#define ALT_NEW_LEN_OFFSET 11
#define X86_FEATURE_POPCNT (4*32+23)
#define X86_FEATURE_SMAP (9*32+20)
struct special_entry {
const char *sec;
bool group, jump_or_nop;
unsigned char size, orig, new;
unsigned char orig_len, new_len; /* group only */
unsigned char feature; /* ALTERNATIVE macro CPU feature */
};
struct special_entry entries[] = {
{
.sec = ".altinstructions",
.group = true,
.size = ALT_ENTRY_SIZE,
.orig = ALT_ORIG_OFFSET,
.orig_len = ALT_ORIG_LEN_OFFSET,
.new = ALT_NEW_OFFSET,
.new_len = ALT_NEW_LEN_OFFSET,
.feature = ALT_FEATURE_OFFSET,
},
{
.sec = "__jump_table",
.jump_or_nop = true,
.size = JUMP_ENTRY_SIZE,
.orig = JUMP_ORIG_OFFSET,
.new = JUMP_NEW_OFFSET,
},
{
.sec = "__ex_table",
.size = EX_ENTRY_SIZE,
.orig = EX_ORIG_OFFSET,
.new = EX_NEW_OFFSET,
},
{},
};
static int get_alt_entry(struct elf *elf, struct special_entry *entry,
struct section *sec, int idx,
struct special_alt *alt)
{
struct rela *orig_rela, *new_rela;
unsigned long offset;
offset = idx * entry->size;
alt->group = entry->group;
alt->jump_or_nop = entry->jump_or_nop;
if (alt->group) {
alt->orig_len = *(unsigned char *)(sec->data->d_buf + offset +
entry->orig_len);
alt->new_len = *(unsigned char *)(sec->data->d_buf + offset +
entry->new_len);
}
if (entry->feature) {
unsigned short feature;
feature = *(unsigned short *)(sec->data->d_buf + offset +
entry->feature);
/*
* It has been requested that we don't validate the !POPCNT
* feature path which is a "very very small percentage of
* machines".
*/
if (feature == X86_FEATURE_POPCNT)
alt->skip_orig = true;
/*
* If UACCESS validation is enabled; force that alternative;
* otherwise force it the other way.
*
* What we want to avoid is having both the original and the
* alternative code flow at the same time, in that case we can
* find paths that see the STAC but take the NOP instead of
* CLAC and the other way around.
*/
if (feature == X86_FEATURE_SMAP) {
if (uaccess)
alt->skip_orig = true;
else
alt->skip_alt = true;
}
}
orig_rela = find_rela_by_dest(sec, offset + entry->orig);
if (!orig_rela) {
WARN_FUNC("can't find orig rela", sec, offset + entry->orig);
return -1;
}
if (orig_rela->sym->type != STT_SECTION) {
WARN_FUNC("don't know how to handle non-section rela symbol %s",
sec, offset + entry->orig, orig_rela->sym->name);
return -1;
}
alt->orig_sec = orig_rela->sym->sec;
alt->orig_off = orig_rela->addend;
if (!entry->group || alt->new_len) {
new_rela = find_rela_by_dest(sec, offset + entry->new);
if (!new_rela) {
WARN_FUNC("can't find new rela",
sec, offset + entry->new);
return -1;
}
alt->new_sec = new_rela->sym->sec;
alt->new_off = (unsigned int)new_rela->addend;
/* _ASM_EXTABLE_EX hack */
if (alt->new_off >= 0x7ffffff0)
alt->new_off -= 0x7ffffff0;
}
return 0;
}
/*
* Read all the special sections and create a list of special_alt structs which
* describe all the alternate instructions which can be patched in or
* redirected to at runtime.
*/
int special_get_alts(struct elf *elf, struct list_head *alts)
{
struct special_entry *entry;
struct section *sec;
unsigned int nr_entries;
struct special_alt *alt;
int idx, ret;
INIT_LIST_HEAD(alts);
for (entry = entries; entry->sec; entry++) {
sec = find_section_by_name(elf, entry->sec);
if (!sec)
continue;
if (sec->len % entry->size != 0) {
WARN("%s size not a multiple of %d",
sec->name, entry->size);
return -1;
}
nr_entries = sec->len / entry->size;
for (idx = 0; idx < nr_entries; idx++) {
alt = malloc(sizeof(*alt));
if (!alt) {
WARN("malloc failed");
return -1;
}
memset(alt, 0, sizeof(*alt));
ret = get_alt_entry(elf, entry, sec, idx, alt);
if (ret)
return ret;
list_add_tail(&alt->list, alts);
}
}
return 0;
}