2014-11-14 15:54:08 +00:00
|
|
|
/*
|
|
|
|
* alternative runtime patching
|
|
|
|
* inspired by the x86 version
|
|
|
|
*
|
|
|
|
* Copyright (C) 2014 ARM Ltd.
|
|
|
|
*
|
|
|
|
* This program is free software; you can redistribute it and/or modify
|
|
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
|
|
* published by the Free Software Foundation.
|
|
|
|
*
|
|
|
|
* 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/>.
|
|
|
|
*/
|
|
|
|
|
|
|
|
#define pr_fmt(fmt) "alternatives: " fmt
|
|
|
|
|
|
|
|
#include <linux/init.h>
|
|
|
|
#include <linux/cpu.h>
|
|
|
|
#include <asm/cacheflush.h>
|
|
|
|
#include <asm/alternative.h>
|
|
|
|
#include <asm/cpufeature.h>
|
2015-06-01 09:47:40 +00:00
|
|
|
#include <asm/insn.h>
|
2016-08-24 17:27:28 +00:00
|
|
|
#include <asm/sections.h>
|
2014-11-14 15:54:08 +00:00
|
|
|
#include <linux/stop_machine.h>
|
|
|
|
|
2015-06-01 09:47:40 +00:00
|
|
|
#define __ALT_PTR(a,f) (u32 *)((void *)&(a)->f + (a)->f)
|
|
|
|
#define ALT_ORIG_PTR(a) __ALT_PTR(a, orig_offset)
|
|
|
|
#define ALT_REPL_PTR(a) __ALT_PTR(a, alt_offset)
|
|
|
|
|
2014-11-28 13:40:45 +00:00
|
|
|
struct alt_region {
|
|
|
|
struct alt_instr *begin;
|
|
|
|
struct alt_instr *end;
|
|
|
|
};
|
|
|
|
|
2015-06-01 09:47:40 +00:00
|
|
|
/*
|
|
|
|
* Check if the target PC is within an alternative block.
|
|
|
|
*/
|
|
|
|
static bool branch_insn_requires_update(struct alt_instr *alt, unsigned long pc)
|
|
|
|
{
|
|
|
|
unsigned long replptr;
|
|
|
|
|
|
|
|
if (kernel_text_address(pc))
|
|
|
|
return 1;
|
|
|
|
|
|
|
|
replptr = (unsigned long)ALT_REPL_PTR(alt);
|
|
|
|
if (pc >= replptr && pc <= (replptr + alt->alt_len))
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Branching into *another* alternate sequence is doomed, and
|
|
|
|
* we're not even trying to fix it up.
|
|
|
|
*/
|
|
|
|
BUG();
|
|
|
|
}
|
|
|
|
|
|
|
|
static u32 get_alt_insn(struct alt_instr *alt, u32 *insnptr, u32 *altinsnptr)
|
|
|
|
{
|
|
|
|
u32 insn;
|
|
|
|
|
|
|
|
insn = le32_to_cpu(*altinsnptr);
|
|
|
|
|
|
|
|
if (aarch64_insn_is_branch_imm(insn)) {
|
|
|
|
s32 offset = aarch64_get_branch_offset(insn);
|
|
|
|
unsigned long target;
|
|
|
|
|
|
|
|
target = (unsigned long)altinsnptr + offset;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* If we're branching inside the alternate sequence,
|
|
|
|
* do not rewrite the instruction, as it is already
|
|
|
|
* correct. Otherwise, generate the new instruction.
|
|
|
|
*/
|
|
|
|
if (branch_insn_requires_update(alt, target)) {
|
|
|
|
offset = target - (unsigned long)insnptr;
|
|
|
|
insn = aarch64_set_branch_offset(insn, offset);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
return insn;
|
|
|
|
}
|
|
|
|
|
2015-07-28 18:07:28 +00:00
|
|
|
static void __apply_alternatives(void *alt_region)
|
2014-11-14 15:54:08 +00:00
|
|
|
{
|
|
|
|
struct alt_instr *alt;
|
2014-11-28 13:40:45 +00:00
|
|
|
struct alt_region *region = alt_region;
|
2015-06-01 09:47:40 +00:00
|
|
|
u32 *origptr, *replptr;
|
2014-11-14 15:54:08 +00:00
|
|
|
|
2014-11-28 13:40:45 +00:00
|
|
|
for (alt = region->begin; alt < region->end; alt++) {
|
2015-06-01 09:47:40 +00:00
|
|
|
u32 insn;
|
|
|
|
int i, nr_inst;
|
|
|
|
|
2014-11-14 15:54:08 +00:00
|
|
|
if (!cpus_have_cap(alt->cpufeature))
|
|
|
|
continue;
|
|
|
|
|
2015-03-27 13:09:22 +00:00
|
|
|
BUG_ON(alt->alt_len != alt->orig_len);
|
2014-11-14 15:54:08 +00:00
|
|
|
|
|
|
|
pr_info_once("patching kernel code\n");
|
|
|
|
|
2015-06-01 09:47:40 +00:00
|
|
|
origptr = ALT_ORIG_PTR(alt);
|
|
|
|
replptr = ALT_REPL_PTR(alt);
|
|
|
|
nr_inst = alt->alt_len / sizeof(insn);
|
|
|
|
|
|
|
|
for (i = 0; i < nr_inst; i++) {
|
|
|
|
insn = get_alt_insn(alt, origptr + i, replptr + i);
|
|
|
|
*(origptr + i) = cpu_to_le32(insn);
|
|
|
|
}
|
|
|
|
|
2014-11-14 15:54:08 +00:00
|
|
|
flush_icache_range((uintptr_t)origptr,
|
2015-06-01 09:47:40 +00:00
|
|
|
(uintptr_t)(origptr + nr_inst));
|
2014-11-14 15:54:08 +00:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2015-07-28 18:07:28 +00:00
|
|
|
/*
|
|
|
|
* We might be patching the stop_machine state machine, so implement a
|
|
|
|
* really simple polling protocol here.
|
|
|
|
*/
|
|
|
|
static int __apply_alternatives_multi_stop(void *unused)
|
2014-11-14 15:54:08 +00:00
|
|
|
{
|
2015-07-28 18:07:28 +00:00
|
|
|
static int patched = 0;
|
2014-11-28 13:40:45 +00:00
|
|
|
struct alt_region region = {
|
2016-08-24 17:27:28 +00:00
|
|
|
.begin = (struct alt_instr *)__alt_instructions,
|
|
|
|
.end = (struct alt_instr *)__alt_instructions_end,
|
2014-11-28 13:40:45 +00:00
|
|
|
};
|
|
|
|
|
2015-07-28 18:07:28 +00:00
|
|
|
/* We always have a CPU 0 at this point (__init) */
|
|
|
|
if (smp_processor_id()) {
|
|
|
|
while (!READ_ONCE(patched))
|
|
|
|
cpu_relax();
|
2015-08-04 17:52:09 +00:00
|
|
|
isb();
|
2015-07-28 18:07:28 +00:00
|
|
|
} else {
|
|
|
|
BUG_ON(patched);
|
|
|
|
__apply_alternatives(®ion);
|
|
|
|
/* Barriers provided by the cache flushing */
|
|
|
|
WRITE_ONCE(patched, 1);
|
|
|
|
}
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
void __init apply_alternatives_all(void)
|
|
|
|
{
|
2014-11-14 15:54:08 +00:00
|
|
|
/* better not try code patching on a live SMP system */
|
2015-07-28 18:07:28 +00:00
|
|
|
stop_machine(__apply_alternatives_multi_stop, NULL, cpu_online_mask);
|
2014-11-28 13:40:45 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
void apply_alternatives(void *start, size_t length)
|
|
|
|
{
|
|
|
|
struct alt_region region = {
|
|
|
|
.begin = start,
|
|
|
|
.end = start + length,
|
|
|
|
};
|
|
|
|
|
|
|
|
__apply_alternatives(®ion);
|
2014-11-14 15:54:08 +00:00
|
|
|
}
|