The includes for the address-space-ID allocator and the translation table are
usually specific to the CPU in use. Therefore these includes can be moved from
their current location in the board header to the CPU headers. This reduces the
number of decisions a board maintainer has to make if the CPU model he's aiming
for is already available.
This can probably also be applied for other includes in the board headers but I
intentionally leave it for a future commit as I don't have the time to do it
all now.
Ref #4217
For base-hw Core, we used to add quite some hardware-specific include paths
to 'INC_DIR'. Generic code used to include, for instance, '<cpu.h>' and
'<translation_table.h>' using these implicit path resolutions. This commit
removes hardware-specific include paths except for
1) the '<board.h>' include paths (e.g., 'src/core/board/pbxa9'),
2) most architecture-specific include paths (e.g., 'src/core/spec/arm_v7'),
3) include paths that reflect usage of virtualization or ARM Trustzone
(e.g., 'src/core/spec/arm/virtualization').
The first category is kept because, in contrast to the former "spec"-mechanism,
the board variable used for this type of resolution is not deprecated and the
board headers are meant to be the front end of hardware-specific headers
towards generic code which is why they must be available generically via
'<board.h>'.
The second category is kept because it was suggested by other maintainers that
simple arch-dependent headers (like for the declaration of a CPU state) should
not imply the inclusion of the whole '<board.h>' and because the architecture
is given also without the former "spec"-mechanism through the type of the build
directory. I think this is questionable but am fine with it.
The third category is kept because the whole way of saying whether
virtualization resp. ARM Trustzone is used is done in an out-dated manner and
changing it now would blow up this commit a lot and exceed the time that I'm
willing to spend. This category should be subject to a future issue.
Ref #4217
The 'src/core/board/<board>/board.h' header is thought as front end of
hardware-specific headers of a given board towards the generic base-hw Core
code. Therefore it leads to problems (circular includes) if the board.h header
is included from within another hardware-specific header.
If hardware-specific headers access declarations from namespace Board in a
definition, the definition should be moved to a compilation unit that may
include board.h. If hardware-specific headers access declarations from board.h
in a declaration, they should either use the primary declaration from the
original header or, if the declaration must be selected according to the board,
another board-specific header should be introduced to reflect this abstraction.
This is applied by this commit for the current state of base-hw.
Ref #4217
It is not necessary to have a class, an object, and a generic header for the
perfomance counter. The kernel merely enables the counter using cpu registers
('msr' instructions, no MMIO) on arm_v6 and arm_v7 only. Therefore this commit
makes the header arm-specific and replaces class and global static object with
a function for enabling the counter.
Fixes#4217
Let the kernel's driver for the global IRQ controller be a member of the one
Kernel::Main object instead of having it as static variables in the drivers for
the local IRQ controllers. Note that this commit spares out renaming 'Pic' to
'Local_interrupt_controller' which would be more sensible now with the new
'Global_interrupt_controller' class. Furthermore, on ARM boards the commit
doesn't move 'Distributer' stuff to the new global IRQ controller class as they
don't have real data members (only MMIO) and can be instanciated for each CPU
anew. However, the right way would be to instanciate them only once in Main as
well.
Ref #4217
The unmanaged-singleton approach was used in this context only because of the
alignment requirement of the Core main-UTCB. This, however can also be achieved
with the new 'Aligned' utility, allowing the UTCB to be a member of the Core
main-thread object.
Ref #4217
It's sufficient to access the boot info only on kernel initialization time.
Therfore, it can remain completely hidden to the rest of the kernel inside
kernel/main.cc in the initialization function.
Ref #4217
This commit introduces the Kernel::Main class that replaces the former way of
initializing the kernel (former 'kernel_init' function) and calling the C++
kernel entry handler (former 'kernel' function). These two are now
'Main::initialize_and_handle_kernel_entry' and 'Main::handle_kernel_entry'.
Also reading the execution time of the idle threads was already moved to
'Main'. The one static Main instance is meant to successivly replace all the
global static objects of the base-hw kernel with data members of the Main
instance making the data model of the kernel much more comprehensible. The
instance and most of its interface are hidden in kernel/main.cc. There are only
rare cases where parts of the Main interface must be accessible from the
outside. This should be done in the most specific way possible (see main.h)
and, if possible, without handing out references to Main data members or the
Main instance itself.
Ref #4217
Normally, the board header can be found for each supported board under
'src/core/board/<BOARD>/board.h'. This was not the case for the board 'pc'
that was located under 'src/core/spec/x86_64/board.h'. The commit fixes this.
Ref #4217
The class name Core_thread in Kernel for the object of the first thread of
core is too generic as there can be an arbitrary number of threads in core
besides this one. Furthermore, creating a core thread has its own syscall
'new_core_thread' that isn't related in any way to Core_thread. Therefore
this commit introduces the more specific name Core_main_thread as replacement
for Core_thread.
Ref #4217
The function was only still used for reading the execution time of idle threads
of CPUs. Certainly, it is technically fine and more performant to read these
values directly from the kernel objects without doing a syscall. However,
calling cpu_pool() for it provides read and write access to a lot more than
only the execution time values. The interface via which Core directly reads
state of the kernel should be as narrow and specific as possible.
Perspectively, we want to get rid of the cpu_pool() accessor anyway. Therefore
this commit introduces Kernel::read_idle_thread_execution_time(cpu_idx) as
replacement. The function is implemented in kernel code and called by Core in
platform.cc.
Ref #4217
Apparently, there is no need for exposing the data members of Trace_source, so,
we sould better make them private before someone gets the impression that they
are meant to be accessed directly.
Ref #4217
Core used to read the kernel-reserved IRQs from the timer objects in the
kernel's CPU objects and the PIC class (inter-processor IRQ). Besides not
being "good style" to access a kernel object in Core, this becomes a problem
when trying to prevent CPU pool from being accessed via global functions.
As a solution, this commit extends the boot info to also carry an array of all
kernel-reserved IRQs.
Ref #4217
For the constructor of Kernel_object<T> there are two variants. One for the
case that it is called from Core where the kernel object (type T) must be
created via a syscall and one when it is called from within the kernel and the
kernel object can be created directly. Selecting one of these variants was done
using a bool argument to the constructor. However, this implies that the
constructor of Kernel_object<T> and that of T have the same signature in the
variadic arguments, even in the syscall case, although technically it would
then not be necessary.
This becomes a problem as soon as kernel objects created by Core shall receive
additional arguments from the kernel, for instance a reference to the global
CPU pool, and therefore stands in the way when wanting to get rid of global
statics in the kernel. Therefore, this commit introduces two constructors that
are selected through enum arguments:
! Kernel_object(Called_from_kernel, ...);
! Kernel_object(Called_from_core, ...);
Ref #4217
Introduce two new cache maintainance functions:
* cache_clean_invalidate_data
* cache_invalidate_data
used to flush or invalidate data-cache lines.
Both functions are typically empty, accept for the ARM architecture.
The commit provides implementations for the base-hw kernel, and Fiasco.OC.
Fixes#4207
Report via platform_info the capabilities of the kernel, e.g. ACPI and MSI.
With the commit the try-catch pattern on IRQ session creation by the platform
driver is avoided.
Issue #4016
This patch unifies the core-internal 'Mapping' type across all base
platforms.
As one minor downside on seL4, the diagnostic error messages when
observing faults other than page faults no longer print the faulting
thread and PD names.
Issue #2243
- Enable the "platform-level interrupt controller" PLIC on base-hw
- The RISC-V specification offers only a register description, but no
layout for the register set. This implies the layout is platform
dependent, and therefore, implemented separately for Qemu
issue #4042
With this patch, the board/<name>/arch property file can have multiple
lines where each line denotes an instruction-set architecture supported
for the board.
Issue #4019Fixes#4034
Simplify calculation of Timer::_duration, the old implementation caused
the time running backwards sometimes. This makes
'nic_router_dhcp_*' and 'event_filter' run scripts succeed.
issue #4021
Do not link base and core libraries into on large relocatable .o file,
which is linked later to core - causing long link times. Create an
independent library archive out of the base and core libraries that can
be linked faster.
issue #4027
This patch simplifies the packaging of the base-hw kernel for a given
board, in particular when the board support is hosted as an external
repository such as genode-world. Regardless of where the board-support
is hosted, the content.mk file becomes as simple as:
include $(GENODE_DIR)/repos/base-hw/recipes/src/base-hw_content.inc
The board name is automatically inferred from the path of the src
recipe. The architecture is determined from board/<name>/arch files,
following the pattern of the image_link_address. The attempt to build a
base-hw-<board> binary archive for the wrong architecture is now
gracefully handled by skipping all targets (using the REQUIRES
mechanism).
Besides the improved convenience, the patch results in depot archives
that are much closer tailored to the actual board by omitting files for
architectures that are not used by the board. E.g., the src/base-hw-pc
archive does not contain any ARM-related content.
The patch also restores the package builds for core/bootstrap object
files as a follow-up fix of "base: remove SPEC variables of boards",
which happened to left 'BOARD' undefined in the src archives.
Fixes#4019
- remove Spike/BBL support in favour of Qemu (>=4.2.1)
- add 'riscv_qemu' board, remove 'spike' board'
- update to privileged ISA v1.10 (from v1.9.1)
- use direct system calls for privileged core threads (they call into
the kernel and don't use mode changing system calls, i.e. 'ecall',
semantics)
- use 'OpenSBI' semtantics for SBI calls (to machine mode) instead of
BBL
issue #4012
Improve consistency with the other base repositories, in particular
- Indentation of class initializers
- Vertical whitespace around control-flow statements
- Preferably place control-flow statements (return, break, continue) at
beginning of a line
- Placing the opening brace of a namespace at the end of line
- Placing the opening brace of a class at a new line
- Removing superfluous braces around single statements
- Two empty lines between methods/functions in implementation files
This patch moves the bootstrap-link-address information from the
tool/run/boot_dir/hw file to board-specific property files that can be
accessed by using the board as key. This eliminates the need to
customize boot_dir/hw when hosting board-support in an external
repository.
Fixes#3998
The _crt0_start_stack label points to a memory location containing the
size of the bootstrap stack. On AArch64 this should be an 8 byte value,
but the code only only defines half of those using asm .long statement.
The other half is expected to be 0, which is true when using GNU as.
This is not the case when using clang's integrated as however. Since
_crt0_stack_size is defined inside .text section clang uses 0xd503201f
value (aarch64 nop instruction) to fill the extra 4 bytes.
Fix this minor incompatibility by explicitly defining both halfs of
this 8 byte quantity.
Fixes#3987
Avoid use of REP_DIR in *.mk files to simplify the use of these files as
templates for a board hosted in a separate repository.
Use REP_INC_DIR for searching headers, thereby considering headers
hosted in an external repository.
Issue #3168
* Remove SPEC declarations from mk/spec
* Remove all board-specific REQUIRE declaratiions left
* Replace [have_spec <board>] run-script declarations with have_board where necessary
* Remove addition of BOARD variable to SPECS in toplevel Makefile
* Move board-specific directories in base-hw out of specs
In case of arm_v7a Kernel::call64 the syscall will use both r0 and r1 as
output registers. Unfortunately the inline asm does not reflect this and
only r0 is explicitly specified as output. GCC manages to produce output
which we'd like to see. Clang on the other hand takes adventage of the fact
r1 should not be touched by swi and produces fewer instructions which do
what the code describes, but not what we actually want.
Basically the code which we want and is generated by GCC is:
svc 0
mov r2, r0
mov r0, r1
mov r1, r2
bx lr
Clang on the other hand generates correct assembly given the code, but
incorrect given what the function is supposed to do:
svc 0
mov r1, r0
mov r0, #0
bx lr
Both GCC and clang generate the same, expected assembly output when r1
is marked as output register from the inline asm swi call.
Fixes#3951
Right now the code marks specific instance of this function as noreturn.
It then tries to initialize it using a value that has the same type,
except for the noreturn part. GCC does not care, but clang complains this
technically assigns the value of entry from incompatible pointer type.
Fix this by defining Entry function as no return.
Issue #3938
The lambda function passed to Board::Vm_page_table_array does not
actually use "this" for anything. GCC does not warn about this, but
clang does. Remove the extra capture to make clang happy.
Issue #3938
GCC doesn't care, but clang complains if [[fallthrough]] is not followed
by a semicolon. Existing code is also not consitent in this regard. Lets
just fix it to make clang happy.
Issue #3938
* Introduce hypervisor-stack per CPU
* Introduce host world context per CPU
* Mark EL2 translation table memory as inner shareable
* The VMID is not bound to a single VCPU, but to the Vm_session as a whole
* Set affinity of the VCPU accordingly
* Add VMPIDR to VM state
Ref #3926
Instead of calling core to run/pause a VCPU, go directly to the kernel.
Apart from the performance win, it would otherwise involve a more complex
protocol, when a VCPU on another core has to be removed from the scheduler.
Core's entrypoint handling those request runs on the boot-cpu only.
Ref #3926
To enable the interaction of a VMM with the kernel directly,
a hidden RPC gets introduced. It allows a kernel-specific
base-library implementation of the Vm_session::Client to request
a kernel-specific capability to address a VCPU, e.g., to
run/stop it.
Ref #3926
* get rid of alarm abstraction
* get rid of Timeout::Time type
* get rid of pointer arguments
* get rid of _discard_timeout indirection
* get rid of 65th bit in stored time values
* get rid of Timeout_scheduler interface
* get rid of uninitialized deadlines
* get rid of default arguments
* get rid of Timeout::_periodic
* get rid of Timeout::Raw
* use list abstraction
* only one interface for timeout handlers
* rework locking scheme to be smp safe
* move all method definitions to CC file
* name mutexes more accurate
* fix when & how to set time-source timeout
* fix deadlocks
Fixes#3884
Adjust the base-* platforms to acknowledge new thread location solely if
migration is supported and succeeded. Otherwise the wrong thread
locations are observed via the trace session and utilization time calculation
get wrong.
Issue #3842
By now, the enumeration of peripheral interrupts on Raspberry Pi 1 was
different in between base-hw kernel and Fiasco.OC. Therefore, hacks were
needed in every driver to request the correct interrupt number dependent
on the kernel. Before reproducing the same in the platform driver for rpi,
we can more easily use the same enumeration with base-hw.
Ref #3864
To access the ARM Trusted Firmware from the platform driver
fill the new `managing_system` call of the PD session with life resp.
do a SMC call on behalf of the client.
Fix#3816
- base/cancelable_lock.h becomes base/lock.h
- all members become private within base/lock.h
- solely Mutex and Blockade are friends to use base/lock.h
Fixes#3819
This patch largely reverts the commit "base: lay groundwork for
base-linux caps change" because the use of 'epoll' instead of 'select'
alleviated the need to allocate large FD sets, which motivated the
introduction of the 'Native_context' hook.
Related to issue #3581
Older ARM processors like ARMv6, or Cortex A8 need to write back changes
of the page-tables to physical ram because the MMU does not use the cache.
This naturally needs to be done not only when adding a mapping,
but on removal too.
Fix#3715
This patch adds support for booting base-hw kernel on qemu-arm virt
machines. The arm_virt machine has 2GB of RAM, 2 Cortex A15 cores and
uses GICv2 interrupt controller. The arm_64_virt machine also has 2GB of
RAM, but has 4 Cortex A53 cores and uses GICv3. Both machines use PSCI
to boot additional CPU cores.
Fixes#3673
So far this only exposes two functions allowing the code to turn on
additional CPUs. There is much more functionality defined by PSCI spec
but so far its not needed by Genode.
Fixes#3672
This is a follow-up fix for commit 202333c881.
It checks for the diagnostic registers being already setup correctly.
Otherwise on platforms with secure firmware, like Pandaboard it will stuck.
Ref #3639
This patch reflects the Out_of_caps exception from core to the client,
in addition to the already covered Out_of_ram exception. It thereby
eliminates a potential abort in core, which I observed with the
tool_chain_auto.run script:
Kernel: RPC upgrade_cap_slab
Error: Uncaught exception of type 'Genode::Quota_guard<Genode::Cap_quota>::Limit_exceeded'
Warning: abort called - thread: entrypoint
In addition to propagating the exception, the patch add the client-side
exception-handling code to the base library.
Fixes#3703
This commit fixes the following issues regarding cache maintainance
under ARM:
* read out I-, and D-cache line size at runtime and use the correct one
* remove 'update_data_region' call from unprivileged syscalls
* rename 'update_instr_region' syscall to 'cache_coherent_region' to
reflect what it doing, namely make I-, and D-cache coherent
* restrict 'cache_coherent_region' syscall to one page at a time
* lookup the region given in a 'cache_coherent_region' syscall in the
page-table of the PD to prevent machine exceptions in the kernel
* only clean D-cache lines, do not invalidate them when pages where
added on Cortex-A8 and ARMv6 (MMU sees phys. memory here)
* remove unused code relicts of cache maintainance
In addition it introduces per architecture memory clearance functions
used by core, when preparing new dataspaces. Thereby, it optimizes:
* on ARMv7 using per-word assignments
* on ARMv8 using cacheline zeroing
* on x86_64 using 'rept stosq' assembler instruction
Fix#3685
The mutex class is more restrictive in usage compared to
Genode::Lock.
- At initialiation time it is ever unlocked.
- No thread is permitted to lock twice. Warn about it
in case it happens.
- Only the lock onwer is permitted to unlock the mutex.
Warn about it and don't unlock the mutex in case it happens.
Issue #3612
In preparation of ipc receive, by now a bunch of capabilities got
allocated to be ready iin case of capability receiption. After that
unuse slots were freed again. This overhead of senseless (de-)allocations
is replaced in this commit by just restock capability slots that got
used by the last receive.
Fix#3640
Error return codes are used with non-const functions in the signaling modules.
This would have been impractical for the in-place translation of the module to
Ada in the context of the Spunky project. Besides, it is easy to get rid of
them and it makes the execution flow more clear.
Ref #3308
Besides reducing the use of pointers in base-hw, this prepares for the in-place
translation of the signaling module to Ada in the context of the Spunky
project.
Ref #3308
This prevents the use of Kernel::Object as base class for the specific kernel
objects and instead makes it a member of the kernel objects. Besides
simplifying inheritance hierarchies in base-hw, this prepares for the in-place
translation of the signaling module (and others) to Ada in the context of the
Spunky project.
Ref #3308
Besides simplifying the execution flow in the signaling module, this prepares
for the in-place translation of the signaling module to Ada in the context of
the Spunky project.
Ref #3308
This prevents the use of C++ features in the public method interface of the
synchronous-IPC module that would be impractical for the in-place
translation of the module into Ada in the context of the Spunky project.
* Get rid of thread accessor.
* Get rid of non-const functions with return values.
* Get rid of pointer return-values.
Ref #3308
Besides simplifying inheritance hierarchies in base-hw, this prepares for the
in-place translation of the synchronous-IPC module to Ada in the context of the
Spunky project.
Ref #3308
This is a simplication of the asyncronous-IPC module of the base-hw kernel.
Besides structuring the code in a cleaner way, it prepares for the in-place
translation of the module into Ada in the context of the Spunky project.
* Get rid of virtual methods in Ipc_node.
* Move all stuff related to protection domains, capabilities, and UTCBs to
the Thread class. this code might later be moved to a dedicated module, but
for now it's just fine to have it done by the thread module.
Ref #3308
Moved code waking up processors for Cortex A53 before changing privilege
level because sending events to higher privilege levels is not allowed.
Fixed enable_mmu for Cortex A53 to properly return cpu id.
Fixed starting code for secondary cores to properly initialize stacks.
Added code to wake up secondary cores on rpi3.
Ref #3573
We cannot count on the correct initialization of the diagnostic register
of the secondary cores. But the boot core gets initialized by the bootchain,
so we can copy over those values.
Fix#3639
Whether an SoC has the multiprocessing extensions can be read out
from the identification registers, and does not need to be specified
in each board header.
Ref #3445
In the past, the core-only privileged syscall `update_pd` was used only
to invalidate the TLB after removal of page-table entries.
By now, the whole TLB at least for one protection domain got invalidated,
but in preparation for optimization and upcomingARM v8 support,
it is necessary to deliver the virtual memory region that needs to get
invalidated. Moreover, the name of the call shall represent explicitely
that it is used to invalidate the TLB.
Ref #3405
On x86 the CPU count is determined through ACPI's MADT by counting the
local APICs reported there. Some platforms report more APICs
than there are actual CPUs. These might be physically disabled CPUs.
Therefore, a check if the LAPIC is actually physically enabled in
hardware fixes this issue.
Thanks to Alex Boettcher
fixes#3376
Fix initial stack pointer alignment for x86_64 in crt0.s startup code of
bootstrap. SysV ABI states that upon function entry (rsp + 8) % 16 = 0.
There, we have to align the stack to 16 bytes before all 'call'
instruction not 8. Otherwise FPU (GP) exception might be raised later on
because of unaligned FPU accesses.
issue #3365
Since gcc 8.3.0 generates SSE instructions into kernel code, the
kernel itself may raise FPU exceptions and/or corrupt user level FPU
contexts thereby. Both things are not feasible, and therefore, lazy FPU
switching becomes a no go for base-hw because we cannot avoid FPU
instructions because of the entanglement of base-hw, base, and the tool
chain (libgcc_eh.a).
issue #3365
Also disable TS (task switch) flag in cr0 during kernel initialization,
so FPU faults are not raised. This became necessary since GCC lately
aggressively generates FPU instructions at arbitrary places and also at
early kernel-bootstrapping stages.
fixes#3365
Components like kernel, core, and bootstrap that are built for a
specific board need to reside inside the same architectural dependent
build directory. For instance there are sel4, foc, and hw kernel builds
for imx6q_sabrelite and imx7d_sabre, which have to reside inside the same
arm_v7 build directory.
This commit names those components explicitely, and adapts the run-tool to it.
Fix#3316
This enforces the use of unsigned 64-bit values for time in the duration type,
the timeout framework, the timer session, the userland timer-drivers, and the
alarm framework on all platforms. The commit also adapts the code that uses
these tools accross all basic repositories (base, base-*, os. gems, libports,
ports, dde_*) to use unsigned 64-bit values for time as well as far as this
does not imply profound modifications.
Fixes#3208
Instead of using `cps` instruction, use an exception return
instruction to switch from `hyp` mode to `svc` mode.
Otherwise it causes unpredicted behaviour on ARM.
Fix#3284
Track the dataspaces used by attach and add handling of flushing VM space
when dataspace gets destroyed (not triggered via the vm_session interface).
Issue #3111
Triggering of an invalidated signal seems to be no real exception,
but something that occurs regularily. Therefore, the kernel warning
is of no use to developers anymore.
Ref #3277
As far as possible remove usage of warning/error/log in the kernel,
otherwise the kernel context might try to take a lock hold by a core
thread, which results in a syscall to block.
Fix#3277
* Introduces pending_signal syscall to check for new signals for the
calling thread without blocking
* Implements pending_signal in the base-library specific for hw to use the
new syscall
Fix#3217
* Introduce 64-bit tick counter
* Let the timer always count when possible, also if it already fired
* Simplify the kernel syscall API to have one current time call,
which returns the elapsed microseconds since boot
In commit "hw: improve cross-cpu synchronization" the implicit safe
initialization of the global kernel lock gets unsafe.
It is a static object, which is protected by the cxx library regarding
its initialization. But our cxx library uses a Genode::semaphore in
the contention case of object construction, which implicitly leads
to kernel syscalls for blocking the corresponding thread. This behaviour
is unacceptable for the kernel code.
Therefore, this fix guards the initialization of the kernel code with
a simple static boolean value explicitely.
Ref #3042
Ref #3043
This commit removes APIs that were previously marked as deprecated. This
change has the following implications:
- The use of the global 'env()' accessor is not possible anymore.
- Boolean accessor methods are no longer prefixed with 'is_'. E.g.,
instead of 'is_valid()', use 'valid()'.
- The last traces of 'Ram_session' are gone now. The 'Env::ram()'
accessor returns the 'Ram_allocator' interface, which is a subset of
the 'Pd_session' interface.
- All connection constructors need the 'Env' as argument.
- The 'Reporter' constructor needs an 'Env' argument now because the
reporter creates a report connection.
- The old overload 'Child_policy::resolve_session_request' that returned
a 'Service' does not exist anymore.
- The base/printf.h header has been removed, use base/log.h instead.
- The old notion of 'Signal_dispatcher' is gone. Use 'Signal_handler'.
- Transitional headers like os/server.h, cap_session/,
volatile_object.h, os/attached*_dataspace.h, signal_rpc_dispatcher.h
have been removed.
- The distinction between 'Thread_state' and 'Thread_state_base' does
not exist anymore.
- The header cpu_thread/capability.h along with the type definition of
'Cpu_thread_capability' has been removed. Use the type
'Thread_capability' define in cpu_session/cpu_session.h instead.
- Several XML utilities (i.e., at os/include/decorator) could be removed
because their functionality is nowadays covered by util/xml_node.h.
- The 'os/ram_session_guard.h' has been removed.
Use 'Constrained_ram_allocator' provided by base/ram_allocator.h instead.
Issue #1987
