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This patch removes default platform implementations of sp_min
platform APIs from plat/common/aarch32/plat_common.c. The APIs
are now implemented in `plat_sp_min_common.c` file within the
same folder.
The ARM platform layer had a weak definition of sp_min_platform_setup2()
which conflicted with the weak definition in the common file. Hence this
patch fixes that by introducing a `plat_arm_` version of the API thus
allowing individual boards within ARM platforms to override it if they
wish to.
Fixes ARM-software/tf-issues#559
Change-Id: I11a74ecae8191878ccc7ea03f12bdd5ae88faba5
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
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Clarify comments in xlat tables lib and fixes related to the TLB
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When the MMU is enabled and the translation tables are mapped, data
read/writes to the translation tables are made using the attributes
specified in the translation tables themselves. However, the MMU
performs table walks with the attributes specified in TCR_ELx. They are
completely independent, so special care has to be taken to make sure
that they are the same.
This has to be done manually because it is not practical to have a test
in the code. Such a test would need to know the virtual memory region
that contains the translation tables and check that for all of the
tables the attributes match the ones in TCR_ELx. As the tables may not
even be mapped at all, this isn't a test that can be made generic.
The flags used by enable_mmu_xxx() have been moved to the same header
where the functions are.
Also, some comments in the linker scripts related to the translation
tables have been fixed.
Change-Id: I1754768bffdae75f53561b1c4a5baf043b45a304
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
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This patch introduces a new BL handover interface. It essentially allows
passing 4 arguments between the different BL stages. Effort has been made
so as to be compatible with the previous handover interface. The previous
blx_early_platform_setup() platform API is now deprecated and the new
blx_early_platform_setup2() variant is introduced. The weak compatiblity
implementation for the new API is done in the `plat_bl_common.c` file.
Some of the new arguments in the new API will be reserved for generic
code use when dynamic configuration support is implemented. Otherwise
the other registers are available for platform use.
Change-Id: Ifddfe2ea8e32497fe1beb565cac155ad9d50d404
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
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support to boot OP-TEE on AArch32/Armv7+example with Cortex-A15/Qemu
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AArch32 only platforms can boot the OP-TEE secure firmware as
a BL32 secure payload. Such configuration can be defined through
AARCH32_SP=optee.
The source files can rely on AARCH32_SP_OPTEE to condition
OP-TEE boot specific instruction sequences.
OP-TEE does not expect ARM Trusted Firmware formatted structure
as boot argument. Load sequence is expected to have already loaded
to OP-TEE boot arguments into the bl32 entrypoint info structure.
Last, AArch32 platform can only boot AArch32 OP-TEE images.
Change-Id: Ic28eec5004315fc9111051add6bb1a1d607fc815
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
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Change-Id: Id6dfe885a63561b1d2649521bd020367b96ae1af
Signed-off-by: Joel Hutton <joel.hutton@arm.com>
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This patch introduces two workarounds for ARMv7 systems. The
workarounds need to be applied prior to any `branch` instruction in
secure world. This is achieved using a custom vector table where each
entry is an `add sp, sp, #1` instruction.
On entry to monitor mode, once the sequence of `ADD` instructions is
executed, the branch target buffer (BTB) is invalidated. The bottom
bits of `SP` are then used to decode the exception entry type.
A side effect of this change is that the exception vectors are
installed before the CPU specific reset function. This is now
consistent with how it is done on AArch64.
Note, on AArch32 systems, the exception vectors are typically tightly
integrated with the secure payload (e.g. the Trusted OS). This
workaround will need porting to each secure payload that requires it.
The patch to modify the AArch32 per-cpu vbar to the corresponding
workaround vector table according to the CPU type will be done in a
later patch.
Change-Id: I5786872497d359e496ebe0757e8017fa98f753fa
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
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Replace magic numbers in linkerscripts by PAGE_SIZE
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This patch fixes a couple of issues for AArch32 builds on ARM reference
platforms :
1. The arm_def.h previously defined the same BL32_BASE value for AArch64 and
AArch32 build. Since BL31 is not present in AArch32 mode, this meant that
the BL31 memory is empty when built for AArch32. Hence this patch allocates
BL32 to the memory region occupied by BL31 for AArch32 builds.
As a side-effect of this change, the ARM_TSP_RAM_LOCATION macro cannot
be used to control the load address of BL32 in AArch32 mode which was
never the intention of the macro anyway.
2. A static assert is added to sp_min linker script to check that the progbits
are within the bounds expected when overlaid with other images.
3. Fix specifying `SPD` when building Juno for AArch32 mode. Due to the quirks
involved when building Juno for AArch32 mode, the build option SPD needed to
specifed. This patch corrects this and also updates the documentation in the
user-guide.
4. Exclude BL31 from the build and FIP when building Juno for AArch32 mode. As
a result the previous assumption that BL31 must be always present is removed
and the certificates for BL31 is only generated if `NEED_BL31` is defined.
Change-Id: I1c39bbc0abd2be8fbe9f2dea2e9cb4e3e3e436a8
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
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When defining different sections in linker scripts it is needed to align
them to multiples of the page size. In most linker scripts this is done
by aligning to the hardcoded value 4096 instead of PAGE_SIZE.
This may be confusing when taking a look at all the codebase, as 4096
is used in some parts that aren't meant to be a multiple of the page
size.
Change-Id: I36c6f461c7782437a58d13d37ec8b822a1663ec1
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
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The `ENABLE_AMU` build option can be used to enable the
architecturally defined AMU counters. At present, there is no support
for the auxiliary counter group.
Change-Id: Ifc7532ef836f83e629f2a146739ab61e75c4abc8
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
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Clear exclusive monitor on SMC and FIQ entry for ARMv7 cores.
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
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This light-weight framework enables some EL3 components to publish
events which other EL3 components can subscribe to. Publisher can
optionally pass opaque data for subscribers. The order in which
subscribers are called is not defined.
Firmware design updated.
Change-Id: I24a3a70b2b1dedcb1f73cf48313818aebf75ebb6
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
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Currently TF does not initialise the PMCR_EL0 register in
the secure context or save/restore the register.
In particular, the DP field may not be set to one to prohibit
cycle counting in the secure state, even though event counting
generally is prohibited via the default setting of MDCR_EL3.SMPE
to 0.
This patch initialises PMCR_EL0.DP to one in the secure state
to prohibit cycle counting and also initialises other fields
that have an architectually UNKNOWN reset value.
Additionally, PMCR_EL0 is added to the list of registers that are
saved and restored during a world switch.
Similar changes are made for PMCR for the AArch32 execution state.
NOTE: secure world code at lower ELs that assume other values in PMCR_EL0
will be impacted.
Change-Id: Iae40e8c0a196d74053accf97063ebc257b4d2f3a
Signed-off-by: David Cunado <david.cunado@arm.com>
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When ARM TF executes in AArch32 state, the NS version of SCTLR
is not being set during warmboot flow. This results in secondary
CPUs entering the Non-secure world with the default reset value
in SCTLR.
This patch explicitly sets the value of the NS version of SCTLR
during the warmboot flow rather than relying on the h/w.
Change-Id: I86bf52b6294baae0a5bd8af0cd0358cc4f55c416
Signed-off-by: David Cunado <david.cunado@arm.com>
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Fix x30 reporting for unhandled exceptions
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Add new alignment parameter to func assembler macro
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Some error paths that lead to a crash dump will overwrite the value in
the x30 register by calling functions with the no_ret macro, which
resolves to a BL instruction. This is not very useful and not what the
reader would expect, since a crash dump should usually show all
registers in the state they were in when the exception happened. This
patch replaces the offending function calls with a B instruction to
preserve the value in x30.
Change-Id: I2a3636f2943f79bab0cd911f89d070012e697c2a
Signed-off-by: Julius Werner <jwerner@chromium.org>
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Assembler programmers are used to being able to define functions with a
specific aligment with a pattern like this:
.align X
myfunction:
However, this pattern is subtly broken when instead of a direct label
like 'myfunction:', you use the 'func myfunction' macro that's standard
in Trusted Firmware. Since the func macro declares a new section for the
function, the .align directive written above it actually applies to the
*previous* section in the assembly file, and the function it was
supposed to apply to is linked with default alignment.
An extreme case can be seen in Rockchip's plat_helpers.S which contains
this code:
[...]
endfunc plat_crash_console_putc
.align 16
func platform_cpu_warmboot
[...]
This assembles into the following plat_helpers.o:
Sections:
Idx Name Size [...] Algn
9 .text.plat_crash_console_putc 00010000 [...] 2**16
10 .text.platform_cpu_warmboot 00000080 [...] 2**3
As can be seen, the *previous* function actually got the alignment
constraint, and it is also 64KB big even though it contains only two
instructions, because the .align directive at the end of its section
forces the assembler to insert a giant sled of NOPs. The function we
actually wanted to align has the default constraint. This code only
works at all because the linker just happens to put the two functions
right behind each other when linking the final image, and since the end
of plat_crash_console_putc is aligned the start of platform_cpu_warmboot
will also be. But it still wastes almost 64KB of image space
unnecessarily, and it will break under certain circumstances (e.g. if
the plat_crash_console_putc function becomes unused and its section gets
garbage-collected out).
There's no real way to fix this with the existing func macro. Code like
func myfunc
.align X
happens to do the right thing, but is still not really correct code
(because the function label is inserted before the .align directive, so
the assembler is technically allowed to insert padding at the beginning
of the function which would then get executed as instructions if the
function was called). Therefore, this patch adds a new parameter with a
default value to the func macro that allows overriding its alignment.
Also fix up all existing instances of this dangerous antipattern.
Change-Id: I5696a07e2fde896f21e0e83644c95b7b6ac79a10
Signed-off-by: Julius Werner <jwerner@chromium.org>
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Add support for a minimal secure interrupt service in sp_min for
the AArch32 implementation. Hard code that only FIQs are handled.
Introduce bolean build directive SP_MIN_WITH_SECURE_FIQ to enable
FIQ handling from SP_MIN.
Configure SCR[FIQ] and SCR[FW] from generic code for both cold and
warm boots to handle FIQ in secure state from monitor.
Since SP_MIN architecture, FIQ are always trapped when system executes
in non secure state. Hence discard relay of the secure/non-secure
state in the FIQ handler.
Change-Id: I1f7d1dc7b21f6f90011b7f3fcd921e455592f5e7
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
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Minor build fixes
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Fully initialise essential control registers
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security_state is either 0 or 1. Prevent sign conversion potential
error (setting -Werror=sign-conversion results in a build error).
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
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This patch updates the el3_arch_init_common macro so that it fully
initialises essential control registers rather then relying on hardware
to set the reset values.
The context management functions are also updated to fully initialise
the appropriate control registers when initialising the non-secure and
secure context structures and when preparing to leave EL3 for a lower
EL.
This gives better alignement with the ARM ARM which states that software
must initialise RES0 and RES1 fields with 0 / 1.
This patch also corrects the following typos:
"NASCR definitions" -> "NSACR definitions"
Change-Id: Ia8940b8351dc27bc09e2138b011e249655041cfc
Signed-off-by: David Cunado <david.cunado@arm.com>
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Flush the console so the errata report is printed correctly
before exit to normal world.
Change-Id: Idd6b5199b5fb8bda9d16a7b5c6426cdda7c73167
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
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On ARM platforms before exiting from SP_MIN ensure that
the default console is switched to the runtime serial port.
Change-Id: I0ca0d42cc47e345d56179eac16aa3d6712767c9b
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
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The current SMC context data structure `smc_ctx_t` and related helpers are
optimized for case when SMC call does not result in world switch. This was
the case for SP_MIN and BL1 cold boot flow. But the firmware update usecase
requires world switch as a result of SMC and the current SMC context helpers
were not helping very much in this regard. Therefore this patch does the
following changes to improve this:
1. Add monitor stack pointer, `spmon` to `smc_ctx_t`
The C Runtime stack pointer in monitor mode, `sp_mon` is added to the
SMC context, and the `smc_ctx_t` pointer is cached in `sp_mon` prior
to exit from Monitor mode. This makes is easier to retrieve the
context when the next SMC call happens. As a result of this change,
the SMC context helpers no longer depend on the stack to save and
restore the register.
This aligns it with the context save and restore mechanism in AArch64.
2. Add SCR in `smc_ctx_t`
Adding the SCR register to `smc_ctx_t` makes it easier to manage this
register state when switching between non secure and secure world as a
result of an SMC call.
Change-Id: I5e12a7056107c1701b457b8f7363fdbf892230bf
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>
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Use SPDX license identifiers
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To make software license auditing simpler, use SPDX[0] license
identifiers instead of duplicating the license text in every file.
NOTE: Files that have been imported by FreeBSD have not been modified.
[0]: https://spdx.org/
Change-Id: I80a00e1f641b8cc075ca5a95b10607ed9ed8761a
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>
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Since Issue B (November 2016) of the SMC Calling Convention document
standard SMC calls are renamed to yielding SMC calls to help avoid
confusion with the standard service SMC range, which remains unchanged.
http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf
This patch adds a new define for yielding SMC call type and deprecates
the current standard SMC call type. The tsp is migrated to use this new
terminology and, additionally, the documentation and code comments are
updated to use this new terminology.
Change-Id: I0d7cc0224667ee6c050af976745f18c55906a793
Signed-off-by: David Cunado <david.cunado@arm.com>
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This patch introduces a build option to enable D-cache early on the CPU
after warm boot. This is applicable for platforms which do not require
interconnect programming to enable cache coherency (eg: single cluster
platforms). If this option is enabled, then warm boot path enables
D-caches immediately after enabling MMU.
Fixes ARM-Software/tf-issues#456
Change-Id: I44c8787d116d7217837ced3bcf0b1d3441c8d80e
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
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Introduce new build option ENABLE_STACK_PROTECTOR. It enables
compilation of all BL images with one of the GCC -fstack-protector-*
options.
A new platform function plat_get_stack_protector_canary() is introduced.
It returns a value that is used to initialize the canary for stack
corruption detection. Returning a random value will prevent an attacker
from predicting the value and greatly increase the effectiveness of the
protection.
A message is printed at the ERROR level when a stack corruption is
detected.
To be effective, the global data must be stored at an address
lower than the base of the stacks. Failure to do so would allow an
attacker to overwrite the canary as part of an attack which would void
the protection.
FVP implementation of plat_get_stack_protector_canary is weak as
there is no real source of entropy on the FVP. It therefore relies on a
timer's value, which could be predictable.
Change-Id: Icaaee96392733b721fa7c86a81d03660d3c1bc06
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
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Patches for platforms with hardware-assisted coherency
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The files affected by this patch don't really depend on `xlat_tables.h`.
By changing the included file it becomes easier to switch between the
two versions of the translation tables library.
Change-Id: Idae9171c490e0865cb55883b19eaf942457c4ccc
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
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At present, warm-booted CPUs keep their caches disabled when enabling
MMU, and remains so until they enter coherency later.
On systems with hardware-assisted coherency, for which
HW_ASSISTED_COHERENCY build flag would be enabled, warm-booted CPUs can
have both caches and MMU enabled at once.
Change-Id: Icb0adb026e01aecf34beadf49c88faa9dd368327
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
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Replace all use of memset by zeromem when zeroing moderately-sized
structure by applying the following transformation:
memset(x, 0, sizeof(x)) => zeromem(x, sizeof(x))
As the Trusted Firmware is compiled with -ffreestanding, it forbids the
compiler from using __builtin_memset and forces it to generate calls to
the slow memset implementation. Zeromem is a near drop in replacement
for this use case, with a more efficient implementation on both AArch32
and AArch64.
Change-Id: Ia7f3a90e888b96d056881be09f0b4d65b41aa79e
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
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Introduce zeromem_dczva function on AArch64 that can handle unaligned
addresses and make use of DC ZVA instruction to zero a whole block at a
time. This zeroing takes place directly in the cache to speed it up
without doing external memory access.
Remove the zeromem16 function on AArch64 and replace it with an alias to
zeromem. This zeromem16 function is now deprecated.
Remove the 16-bytes alignment constraint on __BSS_START__ in
firmware-design.md as it is now not mandatory anymore (it used to comply
with zeromem16 requirements).
Change the 16-bytes alignment constraints in SP min's linker script to a
8-bytes alignment constraint as the AArch32 zeromem implementation is now
more efficient on 8-bytes aligned addresses.
Introduce zero_normalmem and zeromem helpers in platform agnostic header
that are implemented this way:
* AArch32:
* zero_normalmem: zero using usual data access
* zeromem: alias for zero_normalmem
* AArch64:
* zero_normalmem: zero normal memory using DC ZVA instruction
(needs MMU enabled)
* zeromem: zero using usual data access
Usage guidelines: in most cases, zero_normalmem should be preferred.
There are 2 scenarios where zeromem (or memset) must be used instead:
* Code that must run with MMU disabled (which means all memory is
considered device memory for data accesses).
* Code that fills device memory with null bytes.
Optionally, the following rule can be applied if performance is
important:
* Code zeroing small areas (few bytes) that are not secrets should use
memset to take advantage of compiler optimizations.
Note: Code zeroing security-related critical information should use
zero_normalmem/zeromem instead of memset to avoid removal by
compilers' optimizations in some cases or misbehaving versions of GCC.
Fixes ARM-software/tf-issues#408
Change-Id: Iafd9663fc1070413c3e1904e54091cf60effaa82
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
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Standard SMC requests that are handled in the secure-world by the Secure
Payload can be preempted by interrupts that must be handled in the
normal world. When the TSP is preempted the secure context is stored and
control is passed to the normal world to handle the non-secure
interrupt. Once completed the preempted secure context is restored. When
restoring the preempted context, the dispatcher assumes that the TSP
preempted context is still stored as the SECURE context by the context
management library.
However, PSCI power management operations causes synchronous entry into
TSP. This overwrites the preempted SECURE context in the context
management library. When restoring back the SECURE context, the Secure
Payload crashes because this context is not the preempted context
anymore.
This patch avoids corruption of the preempted SECURE context by aborting
any preempted SMC during PSCI power management calls. The
abort_std_smc_entry hook of the TSP is called when aborting the SMC
request.
It also exposes this feature as a FAST SMC callable from normal world to
abort preempted SMC with FID TSP_FID_ABORT.
Change-Id: I7a70347e9293f47d87b5de20484b4ffefb56b770
Signed-off-by: Douglas Raillard <douglas.raillard@arm.com>
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AArch32: Fix the stack alignment issue
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The AArch32 Procedure call Standard mandates that the stack must be aligned
to 8 byte boundary at external interfaces. This patch does the required
changes.
This problem was detected when a crash was encountered in
`psci_print_power_domain_map()` while printing 64 bit values. Aligning
the stack to 8 byte boundary resolved the problem.
Fixes ARM-Software/tf-issues#437
Change-Id: I517bd8203601bb88e9311bd36d477fb7b3efb292
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
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There are many instances in ARM Trusted Firmware where control is
transferred to functions from which return isn't expected. Such jumps
are made using 'bl' instruction to provide the callee with the location
from which it was jumped to. Additionally, debuggers infer the caller by
examining where 'lr' register points to. If a 'bl' of the nature
described above falls at the end of an assembly function, 'lr' will be
left pointing to a location outside of the function range. This misleads
the debugger back trace.
This patch defines a 'no_ret' macro to be used when jumping to functions
from which return isn't expected. The macro ensures to use 'bl'
instruction for the jump, and also, for debug builds, places a 'nop'
instruction immediately thereafter (unless instructed otherwise) so as
to leave 'lr' pointing within the function range.
Change-Id: Ib34c69fc09197cfd57bc06e147cc8252910e01b0
Co-authored-by: Douglas Raillard <douglas.raillard@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>
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This patch moves the invocation of `psci_setup()` from BL31 and SP_MIN
into `std_svc_setup()` as part of ARM Standard Service initialization.
This allows us to consolidate ARM Standard Service initializations which
will be added to in the future. A new function `get_arm_std_svc_args()`
is introduced to get arguments corresponding to each standard service.
This function must be implemented by the EL3 Runtime Firmware and both
SP_MIN and BL31 implement it.
Change-Id: I38e1b644f797fa4089b20574bd4a10f0419de184
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This patch introduces a `psci_lib_args_t` structure which must be
passed into `psci_setup()` which is then used to initialize the PSCI
library. The `psci_lib_args_t` is a versioned structure so as to enable
compatibility checks during library initialization. Both BL31 and SP_MIN
are modified to use the new structure.
SP_MIN is also modified to add version string and build message as part
of its cold boot log just like the other BLs in Trusted Firmware.
NOTE: Please be aware that this patch modifies the prototype of
`psci_setup()`, which breaks compatibility with EL3 Runtime Firmware
(excluding BL31 and SP_MIN) integrated with the PSCI Library.
Change-Id: Ic3761db0b790760a7ad664d8a437c72ea5edbcd6
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This patch adds support in SP_MIN to receive generic and
platform specific arguments from BL2.
The new signature is as following:
void sp_min_early_platform_setup(void *from_bl2,
void *plat_params_from_bl2);
ARM platforms have been modified to use this support.
Note: Platforms may break if using old signature.
Default value for RESET_TO_SP_MIN is changed to 0.
Change-Id: I008d4b09fd3803c7b6231587ebf02a047bdba8d0
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This patch uses the `el3_entrypoint_common` macro to initialize
CPU registers, in SP_MIN entrypoint.s file, in both cold and warm
boot path. It also adds conditional compilation, in cold and warm
boot entry path, based on RESET_TO_SP_MIN.
Change-Id: Id493ca840dc7b9e26948dc78ee928e9fdb76b9e4
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This patch adds a minimal AArch32 secure payload SP_MIN. It relies on PSCI
library to initialize the normal world context. It runs in Monitor mode
and uses the runtime service framework to handle SMCs. It is added as
a BL32 component in the Trusted Firmware source tree.
Change-Id: Icc04fa6b242025a769c1f6c7022fde19459c43e9
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This patch moves the assembly exclusive lock library code
`spinlock.S` into architecture specific folder `aarch64`.
A stub file which includes the file from new location is
retained at the original location for compatibility. The BL
makefiles are also modified to include the file from the new
location.
Change-Id: Ide0b601b79c439e390c3a017d93220a66be73543
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In debug builds, the TSP prints its image base address and size.
The base address displayed corresponds to the start address of the
read-only section, as defined in the linker script.
This patch changes this to use the BL32_BASE address instead, which is
the same address as __RO_START__ at the moment but has the advantage
to be independent of the linker symbols defined in the linker script
as well as the layout and order of the sections.
Change-Id: I032d8d50df712c014cbbcaa84a9615796ec902cc
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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
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