xref: /openbmc/linux/arch/s390/kernel/alternative.c (revision e6ed91fd)

// SPDX-License-Identifier: GPL-2.0
#include <linux/module.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <asm/text-patching.h>
#include <asm/alternative.h>
#include <asm/facility.h>
#include <asm/nospec-branch.h>

static int __initdata_or_module alt_instr_disabled;

static int __init disable_alternative_instructions(char *str)
{
	alt_instr_disabled = 1;
	return 0;
}

early_param("noaltinstr", disable_alternative_instructions);

static void __init_or_module __apply_alternatives(struct alt_instr *start,
						  struct alt_instr *end)
{
	struct alt_instr *a;
	u8 *instr, *replacement;

	/*
	 * The scan order should be from start to end. A later scanned
	 * alternative code can overwrite previously scanned alternative code.
	 */
	for (a = start; a < end; a++) {
		instr = (u8 *)&a->instr_offset + a->instr_offset;
		replacement = (u8 *)&a->repl_offset + a->repl_offset;

		if (!__test_facility(a->facility, alt_stfle_fac_list))
			continue;

		if (unlikely(a->instrlen % 2)) {
			WARN_ONCE(1, "cpu alternatives instructions length is "
				     "odd, skipping patching\n");
			continue;
		}

		s390_kernel_write(instr, replacement, a->instrlen);
	}
}

void __init_or_module apply_alternatives(struct alt_instr *start,
					 struct alt_instr *end)
{
	if (!alt_instr_disabled)
		__apply_alternatives(start, end);
}

extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
void __init apply_alternative_instructions(void)
{
	apply_alternatives(__alt_instructions, __alt_instructions_end);
}

static void do_sync_core(void *info)
{
	sync_core();
}

void text_poke_sync(void)
{
	on_each_cpu(do_sync_core, NULL, 1);
}

void text_poke_sync_lock(void)
{
	cpus_read_lock();
	text_poke_sync();
	cpus_read_unlock();
}