arm-trusted-firmware/lib/aarch64/cache_helpers.S
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

209 lines
5.7 KiB
ArmAsm

/*
* Copyright (c) 2013-2020, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <arch.h>
#include <asm_macros.S>
.globl flush_dcache_range
.globl clean_dcache_range
.globl inv_dcache_range
.globl dcsw_op_louis
.globl dcsw_op_all
.globl dcsw_op_level1
.globl dcsw_op_level2
.globl dcsw_op_level3
/*
* This macro can be used for implementing various data cache operations `op`
*/
.macro do_dcache_maintenance_by_mva op
/* Exit early if size is zero */
cbz x1, exit_loop_\op
dcache_line_size x2, x3
add x1, x0, x1
sub x3, x2, #1
bic x0, x0, x3
loop_\op:
dc \op, x0
add x0, x0, x2
cmp x0, x1
b.lo loop_\op
dsb sy
exit_loop_\op:
ret
.endm
/* ------------------------------------------
* Clean+Invalidate from base address till
* size. 'x0' = addr, 'x1' = size
* ------------------------------------------
*/
func flush_dcache_range
do_dcache_maintenance_by_mva civac
endfunc flush_dcache_range
/* ------------------------------------------
* Clean from base address till size.
* 'x0' = addr, 'x1' = size
* ------------------------------------------
*/
func clean_dcache_range
do_dcache_maintenance_by_mva cvac
endfunc clean_dcache_range
/* ------------------------------------------
* Invalidate from base address till
* size. 'x0' = addr, 'x1' = size
* ------------------------------------------
*/
func inv_dcache_range
do_dcache_maintenance_by_mva ivac
endfunc inv_dcache_range
/* ---------------------------------------------------------------
* Data cache operations by set/way to the level specified
*
* The main function, do_dcsw_op requires:
* x0: The operation type (0-2), as defined in arch.h
* x3: The last cache level to operate on
* x9: clidr_el1
* x10: The cache level to begin operation from
* and will carry out the operation on each data cache from level 0
* to the level in x3 in sequence
*
* The dcsw_op macro sets up the x3 and x9 parameters based on
* clidr_el1 cache information before invoking the main function
* ---------------------------------------------------------------
*/
.macro dcsw_op shift, fw, ls
mrs x9, clidr_el1
ubfx x3, x9, \shift, \fw
lsl x3, x3, \ls
mov x10, xzr
b do_dcsw_op
.endm
func do_dcsw_op
cbz x3, exit
adr x14, dcsw_loop_table // compute inner loop address
add x14, x14, x0, lsl #5 // inner loop is 8x32-bit instructions
#if ENABLE_BTI
add x14, x14, x0, lsl #2 // inner loop is + "bti j" instruction
#endif
mov x0, x9
mov w8, #1
loop1:
add x2, x10, x10, lsr #1 // work out 3x current cache level
lsr x1, x0, x2 // extract cache type bits from clidr
and x1, x1, #7 // mask the bits for current cache only
cmp x1, #2 // see what cache we have at this level
b.lo level_done // nothing to do if no cache or icache
msr csselr_el1, x10 // select current cache level in csselr
isb // isb to sych the new cssr&csidr
mrs x1, ccsidr_el1 // read the new ccsidr
and x2, x1, #7 // extract the length of the cache lines
add x2, x2, #4 // add 4 (line length offset)
ubfx x4, x1, #3, #10 // maximum way number
clz w5, w4 // bit position of way size increment
lsl w9, w4, w5 // w9 = aligned max way number
lsl w16, w8, w5 // w16 = way number loop decrement
orr w9, w10, w9 // w9 = combine way and cache number
ubfx w6, w1, #13, #15 // w6 = max set number
lsl w17, w8, w2 // w17 = set number loop decrement
dsb sy // barrier before we start this level
br x14 // jump to DC operation specific loop
.macro dcsw_loop _op
#if ENABLE_BTI
bti j
#endif
loop2_\_op:
lsl w7, w6, w2 // w7 = aligned max set number
loop3_\_op:
orr w11, w9, w7 // combine cache, way and set number
dc \_op, x11
subs w7, w7, w17 // decrement set number
b.hs loop3_\_op
subs x9, x9, x16 // decrement way number
b.hs loop2_\_op
b level_done
.endm
level_done:
add x10, x10, #2 // increment cache number
cmp x3, x10
b.hi loop1
msr csselr_el1, xzr // select cache level 0 in csselr
dsb sy // barrier to complete final cache operation
isb
exit:
ret
endfunc do_dcsw_op
dcsw_loop_table:
dcsw_loop isw
dcsw_loop cisw
dcsw_loop csw
func dcsw_op_louis
dcsw_op #LOUIS_SHIFT, #CLIDR_FIELD_WIDTH, #LEVEL_SHIFT
endfunc dcsw_op_louis
func dcsw_op_all
dcsw_op #LOC_SHIFT, #CLIDR_FIELD_WIDTH, #LEVEL_SHIFT
endfunc dcsw_op_all
/* ---------------------------------------------------------------
* Helper macro for data cache operations by set/way for the
* level specified
* ---------------------------------------------------------------
*/
.macro dcsw_op_level level
mrs x9, clidr_el1
mov x3, \level
sub x10, x3, #2
b do_dcsw_op
.endm
/* ---------------------------------------------------------------
* Data cache operations by set/way for level 1 cache
*
* The main function, do_dcsw_op requires:
* x0: The operation type (0-2), as defined in arch.h
* ---------------------------------------------------------------
*/
func dcsw_op_level1
dcsw_op_level #(1 << LEVEL_SHIFT)
endfunc dcsw_op_level1
/* ---------------------------------------------------------------
* Data cache operations by set/way for level 2 cache
*
* The main function, do_dcsw_op requires:
* x0: The operation type (0-2), as defined in arch.h
* ---------------------------------------------------------------
*/
func dcsw_op_level2
dcsw_op_level #(2 << LEVEL_SHIFT)
endfunc dcsw_op_level2
/* ---------------------------------------------------------------
* Data cache operations by set/way for level 3 cache
*
* The main function, do_dcsw_op requires:
* x0: The operation type (0-2), as defined in arch.h
* ---------------------------------------------------------------
*/
func dcsw_op_level3
dcsw_op_level #(3 << LEVEL_SHIFT)
endfunc dcsw_op_level3