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/*
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* Copyright (c) 2013-2017, ARM Limited and Contributors. All rights reserved.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include <platform_def.h>
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OUTPUT_FORMAT(PLATFORM_LINKER_FORMAT)
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OUTPUT_ARCH(PLATFORM_LINKER_ARCH)
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ENTRY(bl31_entrypoint)
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MEMORY {
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RAM (rwx): ORIGIN = BL31_BASE, LENGTH = BL31_LIMIT - BL31_BASE
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}
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#ifdef PLAT_EXTRA_LD_SCRIPT
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#include <plat.ld.S>
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#endif
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SECTIONS
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{
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. = BL31_BASE;
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ASSERT(. == ALIGN(4096),
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"BL31_BASE address is not aligned on a page boundary.")
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Introduce SEPARATE_CODE_AND_RODATA build flag
At the moment, all BL images share a similar memory layout: they start
with their code section, followed by their read-only data section.
The two sections are contiguous in memory. Therefore, the end of the
code section and the beginning of the read-only data one might share
a memory page. This forces both to be mapped with the same memory
attributes. As the code needs to be executable, this means that the
read-only data stored on the same memory page as the code are
executable as well. This could potentially be exploited as part of
a security attack.
This patch introduces a new build flag called
SEPARATE_CODE_AND_RODATA, which isolates the code and read-only data
on separate memory pages. This in turn allows independent control of
the access permissions for the code and read-only data.
This has an impact on memory footprint, as padding bytes need to be
introduced between the code and read-only data to ensure the
segragation of the two. To limit the memory cost, the memory layout
of the read-only section has been changed in this case.
- When SEPARATE_CODE_AND_RODATA=0, the layout is unchanged, i.e.
the read-only section still looks like this (padding omitted):
| ... |
+-------------------+
| Exception vectors |
+-------------------+
| Read-only data |
+-------------------+
| Code |
+-------------------+ BLx_BASE
In this case, the linker script provides the limits of the whole
read-only section.
- When SEPARATE_CODE_AND_RODATA=1, the exception vectors and
read-only data are swapped, such that the code and exception
vectors are contiguous, followed by the read-only data. This
gives the following new layout (padding omitted):
| ... |
+-------------------+
| Read-only data |
+-------------------+
| Exception vectors |
+-------------------+
| Code |
+-------------------+ BLx_BASE
In this case, the linker script now exports 2 sets of addresses
instead: the limits of the code and the limits of the read-only
data. Refer to the Firmware Design guide for more details. This
provides platform code with a finer-grained view of the image
layout and allows it to map these 2 regions with the appropriate
access permissions.
Note that SEPARATE_CODE_AND_RODATA applies to all BL images.
Change-Id: I936cf80164f6b66b6ad52b8edacadc532c935a49
8 years ago
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#if SEPARATE_CODE_AND_RODATA
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.text . : {
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__TEXT_START__ = .;
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*bl31_entrypoint.o(.text*)
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*(.text*)
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*(.vectors)
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. = NEXT(4096);
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__TEXT_END__ = .;
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} >RAM
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.rodata . : {
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__RODATA_START__ = .;
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*(.rodata*)
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/* Ensure 8-byte alignment for descriptors and ensure inclusion */
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. = ALIGN(8);
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__RT_SVC_DESCS_START__ = .;
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KEEP(*(rt_svc_descs))
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__RT_SVC_DESCS_END__ = .;
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#if ENABLE_PMF
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/* Ensure 8-byte alignment for descriptors and ensure inclusion */
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. = ALIGN(8);
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__PMF_SVC_DESCS_START__ = .;
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KEEP(*(pmf_svc_descs))
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__PMF_SVC_DESCS_END__ = .;
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#endif /* ENABLE_PMF */
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/*
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* Ensure 8-byte alignment for cpu_ops so that its fields are also
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* aligned. Also ensure cpu_ops inclusion.
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*/
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. = ALIGN(8);
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__CPU_OPS_START__ = .;
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KEEP(*(cpu_ops))
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__CPU_OPS_END__ = .;
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/* Place pubsub sections for events */
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. = ALIGN(8);
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#include <pubsub_events.h>
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Introduce SEPARATE_CODE_AND_RODATA build flag
At the moment, all BL images share a similar memory layout: they start
with their code section, followed by their read-only data section.
The two sections are contiguous in memory. Therefore, the end of the
code section and the beginning of the read-only data one might share
a memory page. This forces both to be mapped with the same memory
attributes. As the code needs to be executable, this means that the
read-only data stored on the same memory page as the code are
executable as well. This could potentially be exploited as part of
a security attack.
This patch introduces a new build flag called
SEPARATE_CODE_AND_RODATA, which isolates the code and read-only data
on separate memory pages. This in turn allows independent control of
the access permissions for the code and read-only data.
This has an impact on memory footprint, as padding bytes need to be
introduced between the code and read-only data to ensure the
segragation of the two. To limit the memory cost, the memory layout
of the read-only section has been changed in this case.
- When SEPARATE_CODE_AND_RODATA=0, the layout is unchanged, i.e.
the read-only section still looks like this (padding omitted):
| ... |
+-------------------+
| Exception vectors |
+-------------------+
| Read-only data |
+-------------------+
| Code |
+-------------------+ BLx_BASE
In this case, the linker script provides the limits of the whole
read-only section.
- When SEPARATE_CODE_AND_RODATA=1, the exception vectors and
read-only data are swapped, such that the code and exception
vectors are contiguous, followed by the read-only data. This
gives the following new layout (padding omitted):
| ... |
+-------------------+
| Read-only data |
+-------------------+
| Exception vectors |
+-------------------+
| Code |
+-------------------+ BLx_BASE
In this case, the linker script now exports 2 sets of addresses
instead: the limits of the code and the limits of the read-only
data. Refer to the Firmware Design guide for more details. This
provides platform code with a finer-grained view of the image
layout and allows it to map these 2 regions with the appropriate
access permissions.
Note that SEPARATE_CODE_AND_RODATA applies to all BL images.
Change-Id: I936cf80164f6b66b6ad52b8edacadc532c935a49
8 years ago
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. = NEXT(4096);
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__RODATA_END__ = .;
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} >RAM
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#else
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ro . : {
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__RO_START__ = .;
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*bl31_entrypoint.o(.text*)
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*(.text*)
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*(.rodata*)
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/* Ensure 8-byte alignment for descriptors and ensure inclusion */
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. = ALIGN(8);
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__RT_SVC_DESCS_START__ = .;
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KEEP(*(rt_svc_descs))
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__RT_SVC_DESCS_END__ = .;
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#if ENABLE_PMF
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/* Ensure 8-byte alignment for descriptors and ensure inclusion */
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. = ALIGN(8);
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__PMF_SVC_DESCS_START__ = .;
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KEEP(*(pmf_svc_descs))
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__PMF_SVC_DESCS_END__ = .;
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#endif /* ENABLE_PMF */
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/*
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* Ensure 8-byte alignment for cpu_ops so that its fields are also
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* aligned. Also ensure cpu_ops inclusion.
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*/
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. = ALIGN(8);
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__CPU_OPS_START__ = .;
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KEEP(*(cpu_ops))
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__CPU_OPS_END__ = .;
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/* Place pubsub sections for events */
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. = ALIGN(8);
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#include <pubsub_events.h>
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*(.vectors)
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__RO_END_UNALIGNED__ = .;
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/*
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* Memory page(s) mapped to this section will be marked as read-only,
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* executable. No RW data from the next section must creep in.
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* Ensure the rest of the current memory page is unused.
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*/
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. = NEXT(4096);
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__RO_END__ = .;
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} >RAM
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Introduce SEPARATE_CODE_AND_RODATA build flag
At the moment, all BL images share a similar memory layout: they start
with their code section, followed by their read-only data section.
The two sections are contiguous in memory. Therefore, the end of the
code section and the beginning of the read-only data one might share
a memory page. This forces both to be mapped with the same memory
attributes. As the code needs to be executable, this means that the
read-only data stored on the same memory page as the code are
executable as well. This could potentially be exploited as part of
a security attack.
This patch introduces a new build flag called
SEPARATE_CODE_AND_RODATA, which isolates the code and read-only data
on separate memory pages. This in turn allows independent control of
the access permissions for the code and read-only data.
This has an impact on memory footprint, as padding bytes need to be
introduced between the code and read-only data to ensure the
segragation of the two. To limit the memory cost, the memory layout
of the read-only section has been changed in this case.
- When SEPARATE_CODE_AND_RODATA=0, the layout is unchanged, i.e.
the read-only section still looks like this (padding omitted):
| ... |
+-------------------+
| Exception vectors |
+-------------------+
| Read-only data |
+-------------------+
| Code |
+-------------------+ BLx_BASE
In this case, the linker script provides the limits of the whole
read-only section.
- When SEPARATE_CODE_AND_RODATA=1, the exception vectors and
read-only data are swapped, such that the code and exception
vectors are contiguous, followed by the read-only data. This
gives the following new layout (padding omitted):
| ... |
+-------------------+
| Read-only data |
+-------------------+
| Exception vectors |
+-------------------+
| Code |
+-------------------+ BLx_BASE
In this case, the linker script now exports 2 sets of addresses
instead: the limits of the code and the limits of the read-only
data. Refer to the Firmware Design guide for more details. This
provides platform code with a finer-grained view of the image
layout and allows it to map these 2 regions with the appropriate
access permissions.
Note that SEPARATE_CODE_AND_RODATA applies to all BL images.
Change-Id: I936cf80164f6b66b6ad52b8edacadc532c935a49
8 years ago
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#endif
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ASSERT(__CPU_OPS_END__ > __CPU_OPS_START__,
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"cpu_ops not defined for this platform.")
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/*
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* Define a linker symbol to mark start of the RW memory area for this
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* image.
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*/
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__RW_START__ = . ;
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/*
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* .data must be placed at a lower address than the stacks if the stack
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* protector is enabled. Alternatively, the .data.stack_protector_canary
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* section can be placed independently of the main .data section.
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*/
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.data . : {
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__DATA_START__ = .;
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*(.data*)
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__DATA_END__ = .;
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} >RAM
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#ifdef BL31_PROGBITS_LIMIT
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ASSERT(. <= BL31_PROGBITS_LIMIT, "BL31 progbits has exceeded its limit.")
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#endif
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stacks (NOLOAD) : {
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__STACKS_START__ = .;
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*(tzfw_normal_stacks)
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__STACKS_END__ = .;
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} >RAM
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/*
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* The .bss section gets initialised to 0 at runtime.
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* Its base address should be 16-byte aligned for better performance of the
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* zero-initialization code.
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*/
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.bss (NOLOAD) : ALIGN(16) {
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__BSS_START__ = .;
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*(.bss*)
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*(COMMON)
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#if !USE_COHERENT_MEM
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/*
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* Bakery locks are stored in normal .bss memory
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*
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* Each lock's data is spread across multiple cache lines, one per CPU,
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* but multiple locks can share the same cache line.
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* The compiler will allocate enough memory for one CPU's bakery locks,
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* the remaining cache lines are allocated by the linker script
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*/
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. = ALIGN(CACHE_WRITEBACK_GRANULE);
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__BAKERY_LOCK_START__ = .;
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*(bakery_lock)
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. = ALIGN(CACHE_WRITEBACK_GRANULE);
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__PERCPU_BAKERY_LOCK_SIZE__ = ABSOLUTE(. - __BAKERY_LOCK_START__);
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. = . + (__PERCPU_BAKERY_LOCK_SIZE__ * (PLATFORM_CORE_COUNT - 1));
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__BAKERY_LOCK_END__ = .;
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#ifdef PLAT_PERCPU_BAKERY_LOCK_SIZE
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ASSERT(__PERCPU_BAKERY_LOCK_SIZE__ == PLAT_PERCPU_BAKERY_LOCK_SIZE,
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"PLAT_PERCPU_BAKERY_LOCK_SIZE does not match bakery lock requirements");
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#endif
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#endif
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#if ENABLE_PMF
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/*
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* Time-stamps are stored in normal .bss memory
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*
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* The compiler will allocate enough memory for one CPU's time-stamps,
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* the remaining memory for other CPU's is allocated by the
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* linker script
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*/
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. = ALIGN(CACHE_WRITEBACK_GRANULE);
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__PMF_TIMESTAMP_START__ = .;
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KEEP(*(pmf_timestamp_array))
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. = ALIGN(CACHE_WRITEBACK_GRANULE);
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__PMF_PERCPU_TIMESTAMP_END__ = .;
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__PERCPU_TIMESTAMP_SIZE__ = ABSOLUTE(. - __PMF_TIMESTAMP_START__);
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. = . + (__PERCPU_TIMESTAMP_SIZE__ * (PLATFORM_CORE_COUNT - 1));
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__PMF_TIMESTAMP_END__ = .;
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#endif /* ENABLE_PMF */
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__BSS_END__ = .;
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} >RAM
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/*
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* The xlat_table section is for full, aligned page tables (4K).
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* Removing them from .bss avoids forcing 4K alignment on
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* the .bss section and eliminates the unecessary zero init
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*/
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xlat_table (NOLOAD) : {
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*(xlat_table)
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} >RAM
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#if USE_COHERENT_MEM
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/*
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* The base address of the coherent memory section must be page-aligned (4K)
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* to guarantee that the coherent data are stored on their own pages and
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* are not mixed with normal data. This is required to set up the correct
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* memory attributes for the coherent data page tables.
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*/
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coherent_ram (NOLOAD) : ALIGN(4096) {
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__COHERENT_RAM_START__ = .;
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/*
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* Bakery locks are stored in coherent memory
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*
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* Each lock's data is contiguous and fully allocated by the compiler
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*/
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*(bakery_lock)
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*(tzfw_coherent_mem)
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__COHERENT_RAM_END_UNALIGNED__ = .;
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/*
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* Memory page(s) mapped to this section will be marked
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* as device memory. No other unexpected data must creep in.
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* Ensure the rest of the current memory page is unused.
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*/
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. = NEXT(4096);
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__COHERENT_RAM_END__ = .;
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} >RAM
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#endif
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/*
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* Define a linker symbol to mark end of the RW memory area for this
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* image.
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*/
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__RW_END__ = .;
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__BL31_END__ = .;
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__BSS_SIZE__ = SIZEOF(.bss);
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#if USE_COHERENT_MEM
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__COHERENT_RAM_UNALIGNED_SIZE__ =
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__COHERENT_RAM_END_UNALIGNED__ - __COHERENT_RAM_START__;
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#endif
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ASSERT(. <= BL31_LIMIT, "BL31 image has exceeded its limit.")
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}
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