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Commit 05d25ce7 authored by Patrick Daly's avatar Patrick Daly Committed by Gerrit - the friendly Code Review server
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scm-mpu: Add additional memory protection options 



Add support for a scm call to protect a contiguous physical address range.
Add a config option to use this api to protect the kernel text section.
Otherwise, the user may specify the region through module parameters.

Change-Id: Ie751ec72deb1a1692093559fe8c6784e8bf912a2
Signed-off-by: default avatarPatrick Daly <pdaly@codeaurora.org>
parent e32562d8

Documentation/arm/msm/scm-mpu.txt

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Introduction

============



The scm-mpu driver allows enabling xpu protection of arbitrary physical memory

addresses as a debug mechanism.



Software description

====================



Several methods of controlling this feature are provided.



* CONFIG_KERNEL_TEXT_MPU_PROT - Enables protection of the kernel code and

read-only sections by default.



* kernel command line

scm_mpu.mpu_start=0x0

scm_mpu.mpu_size=0x1000



* /sys/module/scm_mpu/parameters

echo 0x0 > mpu_start

echo 0x1000 > mpu_size

echo 0x11 > mpu_enable



The sysfs interface may also be used to unlock previously defined regions.

echo 0x0 > mpu_start

echo 0x1000 > mpu_size

echo 0x10 > mpu_enable



Limitations

===========

The number of distinct regions allowed is limited by available resources.



No provisions are made for "carving out" or otherwise removing xpu protected

regions from the linux memory map.



XPU protection currently uses 4K alignment.

drivers/soc/qcom/Kconfig

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@@ -635,6 +635,14 @@ config QCOM_NPA_DUMP 
	help

	  Read the NPA dump from RPM memory through debugfs.



config KERNEL_TEXT_MPU_PROT

	bool "Enable xpu protection of kernel r/o sections"

	help

	  Enables xpu protection of kernel code and read-only data

	  sections early in boot. Read access is permitted to

	  all masters; Write access is only permited to the

	  secure world.



source "drivers/soc/qcom/memshare/Kconfig"



endif # ARCH_MSM

drivers/soc/qcom/Makefile

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@@ -39,7 +39,7 @@ obj-$(CONFIG_MSM_QMI_INTERFACE) += qmi_interface.o 


obj-$(CONFIG_MSM_CACHE_DUMP) += cache_dump.o

obj-$(CONFIG_MSM_CPUSS_DUMP) += cpuss_dump.o

obj-$(CONFIG_MSM_SCM) += scm.o scm-boot.o

obj-$(CONFIG_MSM_SCM) += scm.o scm-boot.o scm-mpu.o



obj-$(CONFIG_MSM_SMD) += smd.o smd_debug.o smd_private.o smd_init_dt.o smsm_debug.o

obj-$(CONFIG_MSM_SMEM) += smem.o smem_debug.o

drivers/soc/qcom/scm-mpu.c

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/* Copyright (c) 2015, The Linux Foundation. All rights reserved.

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 and

 * only 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.

 */



#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/module.h>

#include <soc/qcom/scm.h>

#include <linux/mm.h>



#include <asm/sections.h>



#define TZ_PROTECT_MEMORY 0x1



/* filesystem parameters */

#define MPU_MAGIC_LOCK 0x11

#define MPU_MAGIC_UNLOCK 0x10



static ulong mpu_start;

static ulong mpu_size;

static u32 mpu_enable;



module_param(mpu_start, ulong, 0644);

module_param(mpu_size, ulong, 0644);



static void mem_prot_region(u64 start, u64 size, bool lock);

static int set_enabled(const char *val, const struct kernel_param *kp)

{

	int ret = 0;

	ret = param_set_int(val, kp);



	if (mpu_enable == MPU_MAGIC_LOCK)

		mem_prot_region(mpu_start, mpu_size, true);

	else if (mpu_enable == MPU_MAGIC_UNLOCK)

		mem_prot_region(mpu_start, mpu_size, false);

	return ret;

}



static struct kernel_param_ops mpu_ops = {

	.set = set_enabled,

	.get = param_get_int,

};

module_param_cb(mpu_enable, &mpu_ops, &mpu_enable, 0644);



static void mem_prot_region(u64 start, u64 size, bool lock)

{

	int ret;

	struct scm_desc desc = {0};



	desc.arginfo = SCM_ARGS(5);

	desc.args[0] = PAGE_ALIGN(start);

	desc.args[1] = PAGE_ALIGN(size);

	/*

	 * Permissions:  Write:         Read

	 * 0x1           TZ             Anyone

	 * 0x2           TZ             Tz, APPS

	 * 0x3           TZ             Tz

	 */

	desc.args[2] = 0x1;

	desc.args[3] = lock;

	desc.args[4] = 0;



	if (!is_scm_armv8())

		ret = -EINVAL;

	else

		ret = scm_call2(SCM_SIP_FNID(SCM_SVC_MP, TZ_PROTECT_MEMORY),

				&desc);

	if (ret != 0)

		pr_err("Failed to %s region %llx - %llx\n",

			lock ? "protect" : "unlock", start, start + size);

}



#ifdef CONFIG_KERNEL_TEXT_MPU_PROT

static int __init mem_prot_init(void)

{

	phys_addr_t phys = virt_to_phys(_stext);

	mem_prot_region((u64)phys, (u64)(_etext - _stext), true);

	return 0;

}

late_initcall(mem_prot_init);

#else

static int __init mem_prot_init(void)

{

	if (mpu_start && mpu_size)

		mem_prot_region(mpu_start, mpu_size, true);

	return 0;

}

late_initcall(mem_prot_init);

#endif