arm-trusted-firmware/plat/arm/common/arm_bl31_setup.c
Petre-Ionut Tudor 60e8f3cfd5 Read-only xlat tables for BL31 memory
This patch introduces a build flag which allows the xlat tables
to be mapped in a read-only region within BL31 memory. It makes it
much harder for someone who has acquired the ability to write to
arbitrary secure memory addresses to gain control of the
translation tables.

The memory attributes of the descriptors describing the tables
themselves are changed to read-only secure data. This change
happens at the end of BL31 runtime setup. Until this point, the
tables have read-write permissions. This gives a window of
opportunity for changes to be made to the tables with the MMU on
(e.g. reclaiming init code). No changes can be made to the tables
with the MMU turned on from this point onwards. This change is also
enabled for sp_min and tspd.

To make all this possible, the base table was moved to .rodata. The
penalty we pay is that now .rodata must be aligned to the size of
the base table (512B alignment). Still, this is better than putting
the base table with the higher level tables in the xlat_table
section, as that would cost us a full 4KB page.

Changing the tables from read-write to read-only cannot be done with
the MMU on, as the break-before-make sequence would invalidate the
descriptor which resolves the level 3 page table where that very
descriptor is located. This would make the translation required for
writing the changes impossible, generating an MMU fault.

The caches are also flushed.

Signed-off-by: Petre-Ionut Tudor <petre-ionut.tudor@arm.com>
Change-Id: Ibe5de307e6dc94c67d6186139ac3973516430466
2020-02-24 16:52:56 +00:00

334 lines
9.5 KiB
C

/*
* Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <assert.h>
#include <arch.h>
#include <arch_helpers.h>
#include <common/bl_common.h>
#include <common/debug.h>
#include <drivers/console.h>
#include <lib/debugfs.h>
#include <lib/extensions/ras.h>
#include <lib/mmio.h>
#include <lib/xlat_tables/xlat_tables_compat.h>
#include <plat/arm/common/plat_arm.h>
#include <plat/common/platform.h>
#include <platform_def.h>
/*
* Placeholder variables for copying the arguments that have been passed to
* BL31 from BL2.
*/
static entry_point_info_t bl32_image_ep_info;
static entry_point_info_t bl33_image_ep_info;
#if !RESET_TO_BL31
/*
* Check that BL31_BASE is above ARM_TB_FW_CONFIG_LIMIT. The reserved page
* is required for SOC_FW_CONFIG/TOS_FW_CONFIG passed from BL2.
*/
CASSERT(BL31_BASE >= ARM_TB_FW_CONFIG_LIMIT, assert_bl31_base_overflows);
#endif
/* Weak definitions may be overridden in specific ARM standard platform */
#pragma weak bl31_early_platform_setup2
#pragma weak bl31_platform_setup
#pragma weak bl31_plat_arch_setup
#pragma weak bl31_plat_get_next_image_ep_info
#define MAP_BL31_TOTAL MAP_REGION_FLAT( \
BL31_START, \
BL31_END - BL31_START, \
MT_MEMORY | MT_RW | MT_SECURE)
#if RECLAIM_INIT_CODE
IMPORT_SYM(unsigned long, __INIT_CODE_START__, BL_INIT_CODE_BASE);
IMPORT_SYM(unsigned long, __INIT_CODE_END__, BL_INIT_CODE_END);
#define MAP_BL_INIT_CODE MAP_REGION_FLAT( \
BL_INIT_CODE_BASE, \
BL_INIT_CODE_END \
- BL_INIT_CODE_BASE, \
MT_CODE | MT_SECURE)
#endif
#if SEPARATE_NOBITS_REGION
#define MAP_BL31_NOBITS MAP_REGION_FLAT( \
BL31_NOBITS_BASE, \
BL31_NOBITS_LIMIT \
- BL31_NOBITS_BASE, \
MT_MEMORY | MT_RW | MT_SECURE)
#endif
/*******************************************************************************
* Return a pointer to the 'entry_point_info' structure of the next image for the
* security state specified. BL33 corresponds to the non-secure image type
* while BL32 corresponds to the secure image type. A NULL pointer is returned
* if the image does not exist.
******************************************************************************/
struct entry_point_info *bl31_plat_get_next_image_ep_info(uint32_t type)
{
entry_point_info_t *next_image_info;
assert(sec_state_is_valid(type));
next_image_info = (type == NON_SECURE)
? &bl33_image_ep_info : &bl32_image_ep_info;
/*
* None of the images on the ARM development platforms can have 0x0
* as the entrypoint
*/
if (next_image_info->pc)
return next_image_info;
else
return NULL;
}
/*******************************************************************************
* Perform any BL31 early platform setup common to ARM standard platforms.
* Here is an opportunity to copy parameters passed by the calling EL (S-EL1
* in BL2 & EL3 in BL1) before they are lost (potentially). This needs to be
* done before the MMU is initialized so that the memory layout can be used
* while creating page tables. BL2 has flushed this information to memory, so
* we are guaranteed to pick up good data.
******************************************************************************/
void __init arm_bl31_early_platform_setup(void *from_bl2, uintptr_t soc_fw_config,
uintptr_t hw_config, void *plat_params_from_bl2)
{
/* Initialize the console to provide early debug support */
arm_console_boot_init();
#if RESET_TO_BL31
/* There are no parameters from BL2 if BL31 is a reset vector */
assert(from_bl2 == NULL);
assert(plat_params_from_bl2 == NULL);
# ifdef BL32_BASE
/* Populate entry point information for BL32 */
SET_PARAM_HEAD(&bl32_image_ep_info,
PARAM_EP,
VERSION_1,
0);
SET_SECURITY_STATE(bl32_image_ep_info.h.attr, SECURE);
bl32_image_ep_info.pc = BL32_BASE;
bl32_image_ep_info.spsr = arm_get_spsr_for_bl32_entry();
# endif /* BL32_BASE */
/* Populate entry point information for BL33 */
SET_PARAM_HEAD(&bl33_image_ep_info,
PARAM_EP,
VERSION_1,
0);
/*
* Tell BL31 where the non-trusted software image
* is located and the entry state information
*/
bl33_image_ep_info.pc = plat_get_ns_image_entrypoint();
bl33_image_ep_info.spsr = arm_get_spsr_for_bl33_entry();
SET_SECURITY_STATE(bl33_image_ep_info.h.attr, NON_SECURE);
# if ARM_LINUX_KERNEL_AS_BL33
/*
* According to the file ``Documentation/arm64/booting.txt`` of the
* Linux kernel tree, Linux expects the physical address of the device
* tree blob (DTB) in x0, while x1-x3 are reserved for future use and
* must be 0.
*/
bl33_image_ep_info.args.arg0 = (u_register_t)ARM_PRELOADED_DTB_BASE;
bl33_image_ep_info.args.arg1 = 0U;
bl33_image_ep_info.args.arg2 = 0U;
bl33_image_ep_info.args.arg3 = 0U;
# endif
#else /* RESET_TO_BL31 */
/*
* In debug builds, we pass a special value in 'plat_params_from_bl2'
* to verify platform parameters from BL2 to BL31.
* In release builds, it's not used.
*/
assert(((unsigned long long)plat_params_from_bl2) ==
ARM_BL31_PLAT_PARAM_VAL);
/*
* Check params passed from BL2 should not be NULL,
*/
bl_params_t *params_from_bl2 = (bl_params_t *)from_bl2;
assert(params_from_bl2 != NULL);
assert(params_from_bl2->h.type == PARAM_BL_PARAMS);
assert(params_from_bl2->h.version >= VERSION_2);
bl_params_node_t *bl_params = params_from_bl2->head;
/*
* Copy BL33 and BL32 (if present), entry point information.
* They are stored in Secure RAM, in BL2's address space.
*/
while (bl_params != NULL) {
if (bl_params->image_id == BL32_IMAGE_ID)
bl32_image_ep_info = *bl_params->ep_info;
if (bl_params->image_id == BL33_IMAGE_ID)
bl33_image_ep_info = *bl_params->ep_info;
bl_params = bl_params->next_params_info;
}
if (bl33_image_ep_info.pc == 0U)
panic();
#endif /* RESET_TO_BL31 */
}
void bl31_early_platform_setup2(u_register_t arg0, u_register_t arg1,
u_register_t arg2, u_register_t arg3)
{
arm_bl31_early_platform_setup((void *)arg0, arg1, arg2, (void *)arg3);
/*
* Initialize Interconnect for this cluster during cold boot.
* No need for locks as no other CPU is active.
*/
plat_arm_interconnect_init();
/*
* Enable Interconnect coherency for the primary CPU's cluster.
* Earlier bootloader stages might already do this (e.g. Trusted
* Firmware's BL1 does it) but we can't assume so. There is no harm in
* executing this code twice anyway.
* Platform specific PSCI code will enable coherency for other
* clusters.
*/
plat_arm_interconnect_enter_coherency();
}
/*******************************************************************************
* Perform any BL31 platform setup common to ARM standard platforms
******************************************************************************/
void arm_bl31_platform_setup(void)
{
/* Initialize the GIC driver, cpu and distributor interfaces */
plat_arm_gic_driver_init();
plat_arm_gic_init();
#if RESET_TO_BL31
/*
* Do initial security configuration to allow DRAM/device access
* (if earlier BL has not already done so).
*/
plat_arm_security_setup();
#if defined(PLAT_ARM_MEM_PROT_ADDR)
arm_nor_psci_do_dyn_mem_protect();
#endif /* PLAT_ARM_MEM_PROT_ADDR */
#endif /* RESET_TO_BL31 */
/* Enable and initialize the System level generic timer */
mmio_write_32(ARM_SYS_CNTCTL_BASE + CNTCR_OFF,
CNTCR_FCREQ(0U) | CNTCR_EN);
/* Allow access to the System counter timer module */
arm_configure_sys_timer();
/* Initialize power controller before setting up topology */
plat_arm_pwrc_setup();
#if RAS_EXTENSION
ras_init();
#endif
#if USE_DEBUGFS
debugfs_init();
#endif /* USE_DEBUGFS */
}
/*******************************************************************************
* Perform any BL31 platform runtime setup prior to BL31 exit common to ARM
* standard platforms
* Perform BL31 platform setup
******************************************************************************/
void arm_bl31_plat_runtime_setup(void)
{
console_switch_state(CONSOLE_FLAG_RUNTIME);
/* Initialize the runtime console */
arm_console_runtime_init();
#if RECLAIM_INIT_CODE
arm_free_init_memory();
#endif
#if PLAT_RO_XLAT_TABLES
arm_xlat_make_tables_readonly();
#endif
}
#if RECLAIM_INIT_CODE
/*
* Zero out and make RW memory used to store image boot time code so it can
* be reclaimed during runtime
*/
void arm_free_init_memory(void)
{
int ret = xlat_change_mem_attributes(BL_INIT_CODE_BASE,
BL_INIT_CODE_END - BL_INIT_CODE_BASE,
MT_RW_DATA);
if (ret != 0) {
ERROR("Could not reclaim initialization code");
panic();
}
}
#endif
void __init bl31_platform_setup(void)
{
arm_bl31_platform_setup();
}
void bl31_plat_runtime_setup(void)
{
arm_bl31_plat_runtime_setup();
}
/*******************************************************************************
* Perform the very early platform specific architectural setup shared between
* ARM standard platforms. This only does basic initialization. Later
* architectural setup (bl31_arch_setup()) does not do anything platform
* specific.
******************************************************************************/
void __init arm_bl31_plat_arch_setup(void)
{
const mmap_region_t bl_regions[] = {
MAP_BL31_TOTAL,
#if RECLAIM_INIT_CODE
MAP_BL_INIT_CODE,
#endif
#if SEPARATE_NOBITS_REGION
MAP_BL31_NOBITS,
#endif
ARM_MAP_BL_RO,
#if USE_ROMLIB
ARM_MAP_ROMLIB_CODE,
ARM_MAP_ROMLIB_DATA,
#endif
#if USE_COHERENT_MEM
ARM_MAP_BL_COHERENT_RAM,
#endif
{0}
};
setup_page_tables(bl_regions, plat_arm_get_mmap());
enable_mmu_el3(0);
arm_setup_romlib();
}
void __init bl31_plat_arch_setup(void)
{
arm_bl31_plat_arch_setup();
}