Commit graph

4576 commits

Author SHA1 Message Date
Daniel Leung
7605619c1e x86: userspace: page in stack before starting user thread
If generic section is not present at boot, the thread stack
may not be in physical memory. Unconditionally page in the stack
instead of relying on page fault to speed up a little bit
on starting the thread.

Also, this prevents a double fault during thread setup when
setting up stack permission in z_x86_userspace_enter().

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
2021-08-26 21:16:22 -04:00
Daniel Leung
ea0f9474f7 x86: gen_mmu: don't force extra map argument to be base 16
When converting the address and size arguments for extra mappings,
the script assumes they are always base 16. This is not always
the case. So let Python's own int() decides how to interpret
the values as it supports "0x" prefix also.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
2021-08-26 21:16:22 -04:00
Daniel Leung
c11ad59ed6 x86: mmu: don't mark generic sections as present if desired
With demand paging, it is possible for data pages to not be
present in physical memory. The gen_mmu.py script is updated
so that, if so desired, the generic sections are marked
non-present so the paging mechanism can bring them in
if needed.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
2021-08-26 21:16:22 -04:00
Daniel Leung
30e5968d34 x86: don't clear BSS if not in physical memory at boot
If the BSS section is not present in physical memory at boot,
do not zero the section, or else page faults would occur.
The zeroing of BSS will be done once the paging mechanism
has been initialized.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
2021-08-26 21:16:22 -04:00
Daniel Leung
2dfae4a0f7 kernel: demand_paging: allow reserving page frames
This adds the kconfig to allow reserving a number of page frames
which do not count towards free memory. This is to ensure that
there are enough page frames available for paging code and data.
Or else, it would be possible to exhaust all page frames via
anonymous memory mappings.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
2021-08-26 21:16:22 -04:00
Jim Shu
073cfa9cdf arch: riscv: introduce global pointer relative addressing support
Enable RISC-V GP relative addressing by linker relaxation to reduce
the code size. It optimizes addressing of globals in small data section
(.sdata).

The gp initialization at program start needs each SoC support. Also,
if RISC-V SoC has custom linker script, SoC should provide
__global_pointer$ symbol in it's linker script.

Signed-off-by: Jim Shu <cwshu@andestech.com>
2021-08-20 18:53:23 -04:00
Manuel Argüelles
9ff6282089 arch: arm64: invalidate TLBs after ptables swap
This prevent the new thread to attempt accessing cached ptable entries
which are no longer valid.

Signed-off-by: Manuel Argüelles <manuel.arguelles@coredumplabs.com>
2021-08-20 06:26:05 -04:00
Maureen Helm
9b6122d5ac arch: riscv: Increase default CONFIG_TEST_EXTRA_STACKSIZE for 32-bit
Increases the default CONFIG_TEST_EXTRA_STACKSIZE for the 32-bit RISC-V
architecture. This fixes the portability.posix.fs test on the
qemu_riscv32 platform.

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>
2021-08-18 20:54:46 -04:00
Jim Shu
97fa203330 Revert "arch: riscv: added support for custom initialization of gp register"
This reverts commit 7b09d031fa. Because
context save of GP register is removed, we don't need to initialize GP
at thread init. GP will be a constant value so that it could only be
initialized at program start.

Signed-off-by: Jim Shu <cwshu@andestech.com>
2021-08-18 05:18:55 -04:00
Jim Shu
e3fe63a221 arch: riscv: remove unneeded context switch to gp register
RISC-V global pointer (GP) register is neither caller nor callee
register, and it's a constant value in the single ELF file. Thus, we
don't need to save/restore GP at ISR enter/exit. Remove it to optimize
context switch performance.

Signed-off-by: Jim Shu <cwshu@andestech.com>
2021-08-18 05:18:55 -04:00
Jim Shu
e1c7333dc7 arch: riscv: fix typo of context switch macro
Fix typo of LOAD_CALLER/CALLEE macros.

Signed-off-by: Jim Shu <cwshu@andestech.com>
2021-08-18 05:18:55 -04:00
Phil Erwin
78ba3ddbc5 arch: arm: mpu: Put a lock around MPU buffer validate
Related to github #22290.  Getting interrupt during mpu buffer validate
is corrupting index register.  Fix applied to ARC is to disable
interrupts during the buffer validate operation.

Signed-off-by: Phil Erwin <phil.erwin@lexmark.com>
2021-08-17 06:06:33 -04:00
Bradley Bolen
046f93627c arch: arm: cortex_r: Support nested exception detection
Cortex-A/R does not have hardware supported nested interrupts, but it is
easily emulatable using the nesting level stored in the kernel
structure.

Signed-off-by: Bradley Bolen <bbolen@lexmark.com>
2021-08-17 06:06:33 -04:00
Bradley Bolen
1e153b5091 arch: arm: cortex_r: Add support for recoverable data abort
Add functionality based on Cortex-M that enables recovery from a data
abort using zephyr's exception recovery framework.  If there is a
registered z_exc_handle for a function, then use its fixup address if
that function aborts.

Signed-off-by: Bradley Bolen <bbolen@lexmark.com>
2021-08-17 06:06:33 -04:00
Bradley Bolen
ff1a5e7858 arch: arm: cortex_r: Add ARCH_EXCEPT macro
With the addition of userspace support, Cortex-R needs to use SVC calls
to handle oops exceptions.  Add that support by defining ARCH_EXCEPT to
do a svc call.

Signed-off-by: Bradley Bolen <bbolen@lexmark.com>
2021-08-17 06:06:33 -04:00
Bradley Bolen
65dcab81d0 arch: arm: cortex_r: Do not use user stack in svc/isr modes
The user thread cannot be trusted so do not use the stack pointer it
passes in.  Use the thread's privilege stack when in privileged modes to
make sure a user thread does not trick the svc/isr handlers into writing
to memory it should not.

Signed-off-by: Bradley Bolen <bbolen@lexmark.com>
2021-08-17 06:06:33 -04:00
Phil Erwin
e0bed3b989 arch: arm: cortex_r: Add MPU and USERSPACE support
Use Cortex-M code as a basis for adding MPU support for the Cortex-R.

Signed-off-by: Phil Erwin <phil.erwin@lexmark.com>
2021-08-17 06:06:33 -04:00
Daniel Leung
7862724c50 arm64: smp: arm64_smp_init to be done at PRE_KERNEL_2
The arm64_smp_init() is the same initialization level
and priority as the GICv3 interrupt controller. This means
that arm64_smp_init() can be called before the interrupt
controller driver has been initialized if linker decides
to put the driver init entry later. This would result in
faults when arm64_smp_init() is trying to connect interrupts.
So move arm64_smp_init() to PRE_KERNEL_2 instead. SMP
initialization is called later in the boot process so
this should not affect SMP operations.

This is in preparation of making interrupt controller
drivers to be build as static library. The linking order
is going to change which will result in this being
initialized before the interrupt contoller driver.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
2021-08-17 06:06:03 -04:00
Stephanos Ioannidis
6df8f7e435 arch: arm: cortex_m: Add ARMv8.1-M MVE configs
This commit adds the ARMv8.1-M M-Profile Vector Extension (MVE)
configurations as well as the compiler flags to enable it.

The M-Profile Vector Extension consists of the MVE-I and MVE-F
instruction sets which are integer and floating-point vector
instruction sets, respectively.

The MVE-I instruction set is a superset of the ARM DSP instruction
set (ARMv7E-M) and therefore depends on ARMV8_M_DSP, and the MVE-F
instruction set is a superset of the ARM MVE-I instruction set and
therefore depends on ARMV8_1_M_MVEI.

The SoCs that implement the MVE instruction set should select the
following configurations:

  select ARMV8_M_DSP
  select ARMV8_1_M_MVEI
  select ARMV8_1_M_MVEF (if floating-point MVE is supported)

The GCC compiler flags for the MVE instruction set are specified
through the `-mcpu` flag.

In case of the Cortex-M55 (the only supported processor type for
ARMv8.1-M at the time of writing), the `-mcpu=cortex-m55` flag, by
default, enables all the supported extensions which are DSP, MVE-I and
MVE-F.

The extensions that are not supported can be specified by appending
`+no(ext)` to the `-mcpu=cortex-m55` flag:

  -mcpu=cortex-m55           Cortex-M55 with DSP + MVE-I + MVE-F
  -mcpu=cortex-m55+nomve.fp  Cortex-M55 with DSP + MVE-I
  -mcpu=cortex-m55+nomve     Cortex-M55 with DSP
  -mcpu=cortex-m55+nodsp     Cortex-M55 without any extensions

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
2021-08-14 20:29:57 -04:00
Evgeniy Paltsev
44e53eeacf ARC: MWDT: fix SMP build for MWDT toolchain
Metaware assembler doesn't accept '@' symbol in the beginning
of symbol name like GNU does.

Drop excessive '@' for _curr_cpu symbol.

Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>
2021-08-10 07:36:25 -04:00
Evgeniy Paltsev
7ca190c20f ARC: 64BIT: Kconfig increase stacks sizes for 64bit platforms
Increase default stacks sizes for 64bit platforms where it is
required.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>
2021-08-07 20:36:23 -04:00
Evgeniy Paltsev
5ed232b62c ARC: ARCv3 64: adopt ARC SMP code for ARCv3 64 bit
Rewrite ARC SMP code with ASM-compat macros so it can be
used for ARCv3 64 bit.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>
2021-08-07 20:36:23 -04:00
Daniel Leung
c661765f1d arm: cortex-m: setup TLS pointer before switching to main
The TLS global pointer is only set during context switch.
So for the first switch to main thread, the TLS pointer
is NULL which would cause access violation when trying
to access any thread local variables in main thread.
Fix it by setting it before going into main thread.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
2021-07-30 20:16:47 -04:00
Ioannis Glaropoulos
ca5623d288 arm: swap: cleanup an #ifdef statement in swap routine
Cleanup an #ifdef statement in swap_helper.S; use
ARMV6_M_ARMV8_M_BASELINE instead of listing all
Cortex-M baseline implementation variants. This
fixes an issue with Cortex-M23 whose Kconfig
define was not included in the original list.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
f795672743 arm: cortex-m: enhance information dump during HardFault escalation
When inside an escalated HardFault, we would like to get
more information about the reason for this escalation. We
first check if the reason for thise escalation is an SVC,
which occurs within a priority level that does not allow
it to trigger (e.g. fault or another SVC). If this is true
we set the error reason according to the provided argument.

Only when this is not a synchronous SVC that caused the HF,
do we check the other reasons for HF escalation (e.g. a BF
inside a previous BF).

We also add a case for a debug event, to complete going through
the available flags in HFSR.

Finally we ASSERT if we cannot find the reason for the escalation.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
7930829826 arm: cortex-m: move synchronous SVC assessment in a separate function
Move the assessment of a synchronous SVC error into a
separate function. This commit does not introduce any
behavioral changes.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
a8d6c14d30 arm: cortex-m: clean up some more hard-coded constants in swap_helper
Clean up a few more hard-coded constants
in swap_helper.S and replace them with
CMSIS-like defines in cpu.h. No behavioral
changes in this commit.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
03c4bcd920 arm: use BASEPRI_MAX instead of BASEPRI to mask interrupts
When locking interrupt in a critical session, it is
safer to do MSR BASEPRI_MAX instead of BASEPRI. The
rationale is that when writing to BASEPRI_MAX, the
writing is conditional, and is only applied if the
change is to a higher priority level. This commit
replaces BASEPRI with BASEPRI_MAX in operations that
aim to lock some specific interrupts:
- irq_lock()
- masking out PendSV
So, for example, it is not possible to actually
unmask any interrupts by doing an irq_lock operation.
The commit does not introduce behavioral changes.
However, it makes irq_lock() more robust against
future changes to the IRQ locking mechanism.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
7156183985 arm: fix the VTOR alignment requirement for Baseline Cortex-M
Baseline Cortex-M requires VTOR to be aligned on 64-word
boundary. That is because bit-7 of VTOR is also RAZ/WI.
The commit updates the vector table section alignment for
Baseline Cortex-M to reflect the implementation constraint.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
ebcd5de596 arm: cortex_a_r: rename z_platform_init to z_arm_platform_init
Platform specific initialization during early boot
has been a feature supported only by Cortex-M; the
Kconfig symbol is define in arch/arm Kconfig space.
We rename the z_platform_init() function to
z_arm_platform_init(), to indicate more clearly that
this is an internal, private ARM-only API.

This commit does not introduce behavioral changes.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
1706b4dfaa arm: rename z_platform_init to z_arm_platform_init
Platform specific initialization during early boot
has been a feature supported only by Cortex-M; the
Kconfig symbol is defined in arch/arm Kconfig space.
We rename the z_platform_init() function to
z_arm_platform_init(), to indicate more clearly that
this is an internal, private ARM-only API.

This commit does not introduce behavioral changes.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
70984a1587 arm: set DebugMonitor IRQ unconditionally during initialization
If the DebugMonitor extension is implemented by the core,
the interrupt may be pended and become active, even if it
is not enabled. Set the priority level of DebugMonitor upon
system initialization to the intended value unconditionally
so we do not end up in undefined behavior, if the exception
is accidentally pended. Since the priority level is set at
init, we can remove resetting the priority in DWT driver
initialization.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
6981b84550 arm: ensure SysTick IRQ level is set unconditionally
When the SoC implements SysTick, but the system
does not use it as the driver for system timing
we still need to set its interrupt level. This
is because the SysTick IRQ is always enabled,
so we must ensure the interrupt priority is set
to a level lower than the kernel interrupts (for
the assert mechanism to work properly) in case
the SysTick interrupt is accidentaly raised.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
28a59f67b9 arm: route PendSV to spurious IRQ handler if it is unused
If the PendSV interrupt is not used by Zephyr (this is
the case when we build with single-thread support) we
route the interrupt to z_arm_exc_spurious, instead of
assigning 0 to the vector table entry. This is because
the interrupt is always enabled and always exists, so
it is safer to always get the proper error report, in
case we accidentally pend the PendSV, for any reason.

We also add a comment in the PendSV priority setting,
explaining why it has to be assigned a priority level
even if it is not used.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Ioannis Glaropoulos
41d3d38aec arm: aarch32: sort the source files lists alphabetically
Re-organize the library sources list so the files
are sorted alphabetically.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
2021-07-28 21:08:18 -04:00
Bradley Bolen
379bb70728 arch: aarch32: cortex_m/r: Add arch exception helper
Create z_arm_preempted_thread_in_user_mode to abstract the
implementation differences between Cortex-M and R to determine if an
exception came from userspace.

Signed-off-by: Bradley Bolen <bbolen@lexmark.com>
2021-07-28 21:08:09 -04:00
Bradley Bolen
50a6dafdc5 arch: aarch32: cortex_m/r: Add arch helper function
Create z_arm_thread_is_user_mode to abstract the implementation
differences between Cortex-M and R to determine if the current thread is
in user or kernel mode.

Signed-off-by: Bradley Bolen <bbolen@lexmark.com>
2021-07-28 21:08:09 -04:00
Chen Peng1
fbe13b7bc2 cmake: oneApi: add oneApi support on windows.
add .S file extension suffix into CMAKE_ASM_SOURCE_FILE_EXTENSIONS,
because clang from OneApi can't recongnize them as asm files on
windows, then they won't be added into build system.

Signed-off-by: Chen Peng1 <peng1.chen@intel.com>
2021-07-27 07:20:12 -04:00
Dong Wang
a6800cefb1 x86/cache: fix issues in arch dcache flush function
Correct the wrong operand of clflush instruction. The old operand
points to a location inside stack and doesn't work. The new one
works well by taking linux kernel code as reference.

End address instead of size should get round up

Add Kconfig option to disable the usage of mfence intruction for
SoC that has clfulsh but no mfence supported.

Signed-off-by: Dong Wang <dong.d.wang@intel.com>
2021-07-23 16:22:07 -04:00
Martin Åberg
a1d1a5f547 SPARC: Keep interrupts disabled during kernel init
This commit avoids enabling interrupts during Zephyr init.

Details:
Interrupts will be enabled only when the first thread starts or if
arch_irq_unlock() is called before that.

The logic is now:
1. Enable traps, disable interrupts globally
2. Initialize bss
3. Call _PrepC

Use in-place memset() to avoid register window overflow and underflow
traps. That is perhaps not the common scenario, but could happen with
memset() implementation which contains SAVE instructions on a system
with few register windows.

The second, and more important, item this commit addresses is that it
increases the processor interrupt level (priority) to highest. That
is, it enters _PrepC with all maskable interrupts levels disabled.

This fixes some cases where interrupts could be taken after
z_clock_driver_init() while the system was still initializing. That
seem to have occurred when clearing large thread stacks.

The third thing is that we now start out with current window pointer
0 (PSR.CWP=0) instead of 1. It has no practical implication except
for preparing for possible future support for systems with only
two windows.

Signed-off-by: Martin Åberg <martin.aberg@gaisler.com>
2021-07-22 10:25:53 -04:00
Dominik Ermel
86a1252556 arch/Kconfig: Remove stray tab from USERSPACE help
Commit removes stray tab from help.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>
2021-07-15 22:58:28 +03:00
Dylan Hung
b61ea62b6f arch: give the choice "Cache type" a name
Give the choice a name so that the soc/board developers can change the
default selection in their Kconfig.*.

For example:
choice CACHE_TYPE
	default HAS_EXTERNAL_CACHE
endchoice

There was a similar issue had beed discussed:
https://github.com/zephyrproject-rtos/zephyr/issues/6948

Signed-off-by: Dylan Hung <dylan_hung@aspeedtech.com>
Change-Id: I07c3e78a5243b30912f8e44fa3181fa163016318
2021-07-14 10:54:59 +03:00
Huifeng Zhang
0eab654b13 arch: arm64: select SCHED_IPI_SUPPORTED for Armv8_R
Armv8_R supports IPI

Signed-off-by: Huifeng Zhang <Huifeng.Zhang@arm.com>
2021-07-13 09:30:29 -04:00
Huifeng Zhang
c34960bc87 arch: arm64: Unify the initialization of MMU and MPU
Because MMU and MPU should not be enabled together and they provide
the same functionalities.

Signed-off-by: Huifeng Zhang <Huifeng.Zhang@arm.com>
2021-07-13 09:30:29 -04:00
Felipe Neves
7b09d031fa arch: riscv: added support for custom initialization of gp register
Plus added implementation for esp32c3 SoC.

Signed-off-by: Felipe Neves <ryukokki.felipe@gmail.com>
Signed-off-by: Felipe Neves <felipe.neves@espressif.com>
2021-07-07 20:58:50 -04:00
Evgeniy Paltsev
fbc9fbf92f ARC: save/restore accumulator registers on all ARCv2 HS CPUs by default
Accumulator registers (ACCL, ACCH) are used on HS CPUs not only
in case of FPU usage but also in case of MPY usage. We enable MPY
for all ARCv2 HS in commit
18a24c3f6 ARC: gcc-m-cpu: use -mcpu=archs as a default for ARCv2 HS
but we didn't enable accumulator registers management.

Let's enable accumulator registers save/restore on all ARCv2 HS CPUs
by default.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>
2021-07-06 15:17:26 -05:00
Watson Zeng
c6fcdc24ac arch: arc: update ARConnect ICD select mask when new cpu come online
The ARConnect Inter-core Debug Unit (ICD) provides additional
debug assist features in multi-core scenarios. It's useful to halt
other cores when one core is halted.

Before we program ICD in master core(core 0) initial stage, add
all cores to mask. so we need to make sure other slave cores have
launched and in running mode before we enable ICD in master core.

If we launch master core first, then launch slave cores by master
core conditionally, in this scenario, it's not OK.

Let's update arc connect debug (ARConnect ICD) select mask
when new slave core come online by slave core self, instead of
use hardcoded select mask.

Signed-off-by: Watson Zeng <zhiwei@synopsys.com>
2021-07-06 15:10:39 -05:00
Maksim Masalski
466c5d9dea arch: x86: core: remove order eval of 'z_x86_check_stack_bounds' args
The code depends on the order of evaluation 'z_x86_check_stack_bounds'
function arguments.
The solution is to assign these values to variables and then pass
them in.
The fix would be to make 2 local variables, assign them the values
of _df_esf.esp and .cs, and then call the function with those 2 local
variables as arguments.
Found as a coding guideline violation (MISRA R13.2) by static
coding scanning tool.

Change "int reason" to "unsigned reason" like in other functions.

Signed-off-by: Maksim Masalski <maksim.masalski@intel.com>
2021-06-23 07:10:18 -04:00
Maksim Masalski
cbfd33f2ec arch: add comments to empty default case, add default LOG_ERR
According to the Zephyr Coding Guideline all switch statements
shall be well-formed.
Add a comment to the empty default case.
Add a LOG_ERR to the default case.

Found as a coding guideline violation (MISRA R16.1) by static
coding scanning tool.

Signed-off-by: Maksim Masalski <maksim.masalski@intel.com>
2021-06-22 08:23:43 -04:00
Andy Ross
b651aa9f7d arch/x86/zefi: Fix entry-nop hack for EFI entry
commit 5e9c583c24 ("arch/x86_64: Terrible, awful hackery to
bootstrap entry") introduced a terrible trick which begins execution
at the bottom of .locore with a jump, which then gets replaced with
NOP instructions for the benefit of 16 bit real mode startup of the
other CPUs later on.

But I forgot that EFI enters in 64 bit code natively, and so never
hits that path.  And moving it to the 64 bit setup code doesn't work,
because at that point when we are NOT loaded from EFI, we already have
the Zephyr page tables in place that disallow writes to .locore.

So do it in the EFI loader, which while sort of a weird place, has the
benefit of being in C instead of assembly.

Really all this code needs to go away.  A proper x86 entry
architecture would enter somewhere in the main blob, and .locore
should be a tiny stub we copy in at runtime.

Fixes #36107

Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
2021-06-14 08:22:34 -04:00