Advice on architectures with multiple address spaces

Hi lldb developers,

I've been researching using lldb + gdbserver stub that is based on Harvard architecture with multiple address spaces (one program, multiple data). The commonly adopted approach is that everything is mapped to a single "virtual" address space. The stub reads/writes from/to the right memory based on the "virtual" addresses. But I'd like to use real addresses with address space id instead. So, I've started looking at what has to be changed.

I've enhanced read/write commands (e.g. memory read --as <id> ...) and RSP protocol (new packet) so that the stub can read/write properly. That wasn't that complicated.

Now I've hit an issue with expressions (LLVMUserExpression.cpp) and local variables (DWARFExpressions.cpp). There is a lot of memory read/write functions that take just an address argument. Is the only way to go to patch all these calls? Has anybody solved it differently?

Thanks for any advice.

Hi lldb developers,

I've been researching using lldb + gdbserver stub that is based on Harvard architecture with multiple address spaces (one program, multiple data). The commonly adopted approach is that everything is mapped to a single "virtual" address space. The stub reads/writes from/to the right memory based on the "virtual" addresses. But I'd like to use real addresses with address space id instead. So, I've started looking at what has to be changed.

I've enhanced read/write commands (e.g. memory read --as <id> ...) and RSP protocol (new packet) so that the stub can read/write properly. That wasn't that complicated.

It might be nice to add a new RSP protocol packet that asks for the address space names/values:

qGetAddressSpaces

which would return something like:

1:text;2:data1,3:data2

or it would return not supported. If we get a valid return value from qGetAddressSpaces, then it enables the use of the new packet you added above. Else it defaults to using the old memory read functions.

Now I've hit an issue with expressions (LLVMUserExpression.cpp) and local variables (DWARFExpressions.cpp). There is a lot of memory read/write functions that take just an address argument. Is the only way to go to patch all these calls? Has anybody solved it differently?

My quick take is that any APIs that take just a lldb::addr_t would need to take something like:

struct SpaceAddress {
  static constexpr uint32_t kNoSpace = 0;
  lldb::addr_t addr;
  uint32_t space;
};

We would need a default value for "space" (feel free to rename) that indicates the default address space as most of our architectures would not need this support. If we added a constructor like:

SpaceAddress(lldb::addr_t a) : addr(a), space(kNoSpace) {}

Then all usages of the APIs that used to take just a "lldb::addr_t" would implicitly call this constructor and continue to act as needed. Then we would need to allow lldb_private::Address objects to resolve to a SpaceAddress:

  SpaceAddress lldb_private::Address::GetSpaceAddress(Target *target) const;

Since each lldb_private::Address has a section and each section knows its address space. Then the tricky part is finding all locations in the expression parser and converting those to track and use SpaceAddress. We would probably need to modify the allocate memory packets in the RSP protocol to be able to allocate memory in any address space as well.

I didn't spend much time think about correct names above, so feel free to suggest alternate naming.

Best advice:
- make things "just work" to keep changes to a minimum and allowing lldb::addr_t to implicitly convert to a SpaceAddress easily
- when modifying RSP, make sure to check for existence of new feature before enabling it
- query for address space names so when we dump SpaceAddress we can show something that means something to the user. This means we would need to query the address space names from the current lldb_private::Process for display.

Submitting might go easier if we break it down into chunks:
1 - add SpaceAddress and modify all needed APIs to use it
2 - add ProcessGDBRemote changes that enable this support

It will be great to support this as a first class citizen within LLDB. You might ask the Hexagon folks if they have done anything in case they already support this is some shape or form.

Greg Clayton

Hi lldb developers,

I've been researching using lldb + gdbserver stub that is based on Harvard architecture with multiple address spaces (one program, multiple data). The commonly adopted approach is that everything is mapped to a single "virtual" address space. The stub reads/writes from/to the right memory based on the "virtual" addresses. But I'd like to use real addresses with address space id instead. So, I've started looking at what has to be changed.

I've enhanced read/write commands (e.g. memory read --as <id> ...) and RSP protocol (new packet) so that the stub can read/write properly. That wasn't that complicated.

It might be nice to add a new RSP protocol packet that asks for the address space names/values:

qGetAddressSpaces

which would return something like:

1:text;2:data1,3:data2

or it would return not supported. If we get a valid return value from qGetAddressSpaces, then it enables the use of the new packet you added above. Else it defaults to using the old memory read functions.

Now I've hit an issue with expressions (LLVMUserExpression.cpp) and local variables (DWARFExpressions.cpp). There is a lot of memory read/write functions that take just an address argument. Is the only way to go to patch all these calls? Has anybody solved it differently?

My quick take is that any APIs that take just a lldb::addr_t would need to take something like:

struct SpaceAddress {
static constexpr uint32_t kNoSpace = 0;
lldb::addr_t addr;
uint32_t space;
};

I'm curious why you are suggesting another kind of address, rather than adding this functionality to Address? When you actually go to resolve an Address in a target with a process you should have everything you need to know to give it the proper space. Then fixing the expression evaluator (and anything else that needs fixing) would be a matter of consistently using Address rather than lldb::addr_t. That seems general goodness, since converting to an lldb::addr_t loses information.

Jim

Hi lldb developers,

I’ve been researching using lldb + gdbserver stub that is based on Harvard architecture with multiple address spaces (one program, multiple data). The commonly adopted approach is that everything is mapped to a single “virtual” address space. The stub reads/writes from/to the right memory based on the “virtual” addresses. But I’d like to use real addresses with address space id instead. So, I’ve started looking at what has to be changed.

I’ve enhanced read/write commands (e.g. memory read --as …) and RSP protocol (new packet) so that the stub can read/write properly. That wasn’t that complicated.

It might be nice to add a new RSP protocol packet that asks for the address space names/values:

qGetAddressSpaces

which would return something like:

1:text;2:data1,3:data2

or it would return not supported. If we get a valid return value from qGetAddressSpaces, then it enables the use of the new packet you added above. Else it defaults to using the old memory read functions.

Now I’ve hit an issue with expressions (LLVMUserExpression.cpp) and local variables (DWARFExpressions.cpp). There is a lot of memory read/write functions that take just an address argument. Is the only way to go to patch all these calls? Has anybody solved it differently?

My quick take is that any APIs that take just a lldb::addr_t would need to take something like:

struct SpaceAddress {
static constexpr uint32_t kNoSpace = 0;
lldb::addr_t addr;
uint32_t space;
};

I’m curious why you are suggesting another kind of address, rather than adding this functionality to Address? When you actually go to resolve an Address in a target with a process you should have everything you need to know to give it the proper space. Then fixing the expression evaluator (and anything else that needs fixing) would be a matter of consistently using Address rather than lldb::addr_t. That seems general goodness, since converting to an lldb::addr_t loses information.

If we accept lldb_private::Address in all APIs that take a lldb::addr_t currently, then we need to always be able to get to the target in case we need to add code to resolve the address everywhere. I am thinking of SpaceAddress as an augmented lldb::addr_t instead of a section + offset style address. Also, there will be addresses in the code and data that do not exist in actual sections. Not saying that you couldn’t use lldb_private::Address. I am open to suggestions though. So your though it remove all API that take lldb::addr_t and use lldb_private::Address everywhere all the time?

Hi lldb developers,

I've been researching using lldb + gdbserver stub that is based on Harvard architecture with multiple address spaces (one program, multiple data). The commonly adopted approach is that everything is mapped to a single "virtual" address space. The stub reads/writes from/to the right memory based on the "virtual" addresses. But I'd like to use real addresses with address space id instead. So, I've started looking at what has to be changed.

I've enhanced read/write commands (e.g. memory read --as <id> ...) and RSP protocol (new packet) so that the stub can read/write properly. That wasn't that complicated.

It might be nice to add a new RSP protocol packet that asks for the address space names/values:

qGetAddressSpaces

which would return something like:

1:text;2:data1,3:data2

or it would return not supported. If we get a valid return value from qGetAddressSpaces, then it enables the use of the new packet you added above. Else it defaults to using the old memory read functions.

Now I've hit an issue with expressions (LLVMUserExpression.cpp) and local variables (DWARFExpressions.cpp). There is a lot of memory read/write functions that take just an address argument. Is the only way to go to patch all these calls? Has anybody solved it differently?

My quick take is that any APIs that take just a lldb::addr_t would need to take something like:

struct SpaceAddress {
static constexpr uint32_t kNoSpace = 0;
lldb::addr_t addr;
uint32_t space;
};

I'm curious why you are suggesting another kind of address, rather than adding this functionality to Address? When you actually go to resolve an Address in a target with a process you should have everything you need to know to give it the proper space. Then fixing the expression evaluator (and anything else that needs fixing) would be a matter of consistently using Address rather than lldb::addr_t. That seems general goodness, since converting to an lldb::addr_t loses information.

If we accept lldb_private::Address in all APIs that take a lldb::addr_t currently, then we need to always be able to get to the target in case we need to add code to resolve the address everywhere. I am thinking of SpaceAddress as an augmented lldb::addr_t instead of a section + offset style address. Also, there will be addresses in the code and data that do not exist in actual sections. Not saying that you couldn't use lldb_private::Address. I am open to suggestions though. So your though it remove all API that take lldb::addr_t and use lldb_private::Address everywhere all the time?

It has always bugged me that we have these two ways of specifying addresses. Are there many/any places that have to resolve an Address to a real address in a process that don't have a Target readily available? That would surprise me. I would much rather centralize on one way than adding a third.

Jim

Hexagon has a single address space, so we don't need to do anything like this.

When I worked on Motorola 56xxx DSPs we had memory spaces, but we didn't use RSP. We had our own protocol that used a struct for addreses, with the space (an enum, defined per supported core) and a uint32_t (later 2 of them) for the address.

Ted

Hi lldb developers,

I've been researching using lldb + gdbserver stub that is based on Harvard architecture with multiple address spaces (one program, multiple data). The commonly adopted approach is that everything is mapped to a single "virtual" address space. The stub reads/writes from/to the right memory based on the "virtual" addresses. But I'd like to use real addresses with address space id instead. So, I've started looking at what has to be changed.

I've enhanced read/write commands (e.g. memory read --as <id> ...) and RSP protocol (new packet) so that the stub can read/write properly. That wasn't that complicated.

It might be nice to add a new RSP protocol packet that asks for the address space names/values:

qGetAddressSpaces

which would return something like:

1:text;2:data1,3:data2

or it would return not supported. If we get a valid return value from qGetAddressSpaces, then it enables the use of the new packet you added above. Else it defaults to using the old memory read functions.

Sounds good to me. I would return more information though. For instance, you can have a code address space where a 32bit byte is used and data address space where an 8bit byte is used. Some support for this is already in LLDB, although it's not tied to address spaces, but to an architecture.

Now I've hit an issue with expressions (LLVMUserExpression.cpp) and local variables (DWARFExpressions.cpp). There is a lot of memory read/write functions that take just an address argument. Is the only way to go to patch all these calls? Has anybody solved it differently?

My quick take is that any APIs that take just a lldb::addr_t would need to take something like:

struct SpaceAddress {
static constexpr uint32_t kNoSpace = 0;
lldb::addr_t addr;
uint32_t space;
};

I'm curious why you are suggesting another kind of address, rather than adding this functionality to Address? When you actually go to resolve an Address in a target with a process you should have everything you need to know to give it the proper space. Then fixing the expression evaluator (and anything else that needs fixing) would be a matter of consistently using Address rather than lldb::addr_t. That seems general goodness, since converting to an lldb::addr_t loses information.

If we accept lldb_private::Address in all APIs that take a lldb::addr_t currently, then we need to always be able to get to the target in case we need to add code to resolve the address everywhere. I am thinking of SpaceAddress as an augmented lldb::addr_t instead of a section + offset style address. Also, there will be addresses in the code and data that do not exist in actual sections. Not saying that you couldn't use lldb_private::Address. I am open to suggestions though. So your though it remove all API that take lldb::addr_t and use lldb_private::Address everywhere all the time?

It has always bugged me that we have these two ways of specifying addresses. Are there many/any places that have to resolve an Address to a real address in a process that don't have a Target readily available? That would surprise me. I would much rather centralize on one way than adding a third.

Jim

I'd like to remove more ways of describing the same thing, so going with the Address() sounds better. Having said that, there are about 4k instances of lldb::addr_t in LLDB code base. Where to begin/how to split the work? :-)...

Maybe Kalimba developers can help here. Kalimba has crazy memory map...:slight_smile:

Hi lldb developers,

I've been researching using lldb + gdbserver stub that is based on Harvard architecture with multiple address spaces (one program, multiple data). The commonly adopted approach is that everything is mapped to a single "virtual" address space. The stub reads/writes from/to the right memory based on the "virtual" addresses. But I'd like to use real addresses with address space id instead. So, I've started looking at what has to be changed.

I've enhanced read/write commands (e.g. memory read --as <id> ...) and RSP protocol (new packet) so that the stub can read/write properly. That wasn't that complicated.

It might be nice to add a new RSP protocol packet that asks for the address space names/values:

qGetAddressSpaces

which would return something like:

1:text;2:data1,3:data2

or it would return not supported. If we get a valid return value from qGetAddressSpaces, then it enables the use of the new packet you added above. Else it defaults to using the old memory read functions.

Now I've hit an issue with expressions (LLVMUserExpression.cpp) and local variables (DWARFExpressions.cpp). There is a lot of memory read/write functions that take just an address argument. Is the only way to go to patch all these calls? Has anybody solved it differently?

My quick take is that any APIs that take just a lldb::addr_t would need to take something like:

struct SpaceAddress {
static constexpr uint32_t kNoSpace = 0;
lldb::addr_t addr;
uint32_t space;
};

I'm curious why you are suggesting another kind of address, rather than adding this functionality to Address? When you actually go to resolve an Address in a target with a process you should have everything you need to know to give it the proper space. Then fixing the expression evaluator (and anything else that needs fixing) would be a matter of consistently using Address rather than lldb::addr_t. That seems general goodness, since converting to an lldb::addr_t loses information.

If we accept lldb_private::Address in all APIs that take a lldb::addr_t currently, then we need to always be able to get to the target in case we need to add code to resolve the address everywhere. I am thinking of SpaceAddress as an augmented lldb::addr_t instead of a section + offset style address. Also, there will be addresses in the code and data that do not exist in actual sections. Not saying that you couldn't use lldb_private::Address. I am open to suggestions though. So your though it remove all API that take lldb::addr_t and use lldb_private::Address everywhere all the time?

It has always bugged me that we have these two ways of specifying addresses. Are there many/any places that have to resolve an Address to a real address in a process that don't have a Target readily available? That would surprise me. I would much rather centralize on one way than adding a third.

Jim

So, does it make sense to start with lldb::addr_t replacement? In other words, replace all instances of lldb::addr_t with Address. It'd be the first step and first patch towards to the ability to extend it in the future, right?

Zdenek

The Address class may be suitable for the higher layers of lldb, but I
don't think the it can ever be a blanket replacement for lldb::addr_t. It
has way too much smartness built-in. We use addr_t in a lot of places that
don't/shouldn't care about Targets, ExecutionContexts or Sections. All of
lldb-server is one of those places, but this is also true for any low-level
operation which only wants to work with real (virtual) addresses in the
process address space.

On the other hand, replacing addr_t with a lighweight struct which is just
adds some sort of an address space identifier seems like a useful thing,
and would go a long way towards bringing Harward architecture support to
lldb-server. (Note that we would still need an addr_t or something of that
form to name the type of the "address" member of the struct, but pretty
much all of the apis that currently take addr_t, could that the new struct
instead).

>
>>
>>
>>
>>>
>>>
>>>
>>>>
>>>>
>>>>
>>>>>
>>>>> Hi lldb developers,
>>>>>
>>>>> I've been researching using lldb + gdbserver stub that is based on

Harvard architecture with multiple address spaces (one program, multiple
data). The commonly adopted approach is that everything is mapped to a
single "virtual" address space. The stub reads/writes from/to the right
memory based on the "virtual" addresses. But I'd like to use real addresses
with address space id instead. So, I've started looking at what has to be
changed.

>>>>>
>>>>> I've enhanced read/write commands (e.g. memory read --as <id> ...)

and RSP protocol (new packet) so that the stub can read/write properly.
That wasn't that complicated.

>>>> It might be nice to add a new RSP protocol packet that asks for the

address space names/values:

>>>>
>>>> qGetAddressSpaces
>>>>
>>>> which would return something like:
>>>>
>>>> 1:text;2:data1,3:data2
>>>>
>>>> or it would return not supported. If we get a valid return value

from qGetAddressSpaces, then it enables the use of the new packet you added
above. Else it defaults to using the old memory read functions.

>>>>
>>>>
>>>>> Now I've hit an issue with expressions (LLVMUserExpression.cpp) and

local variables (DWARFExpressions.cpp). There is a lot of memory read/write
functions that take just an address argument. Is the only way to go to
patch all these calls? Has anybody solved it differently?

>>>> My quick take is that any APIs that take just a lldb::addr_t would

need to take something like:

>>>>
>>>> struct SpaceAddress {
>>>> static constexpr uint32_t kNoSpace = 0;
>>>> lldb::addr_t addr;
>>>> uint32_t space;
>>>> };
>>>>
>>> I'm curious why you are suggesting another kind of address, rather

than adding this functionality to Address? When you actually go to resolve
an Address in a target with a process you should have everything you need
to know to give it the proper space. Then fixing the expression evaluator
(and anything else that needs fixing) would be a matter of consistently
using Address rather than lldb::addr_t. That seems general goodness, since
converting to an lldb::addr_t loses information.

>> If we accept lldb_private::Address in all APIs that take a

lldb::addr_t currently, then we need to always be able to get to the target
in case we need to add code to resolve the address everywhere. I am
thinking of SpaceAddress as an augmented lldb::addr_t instead of a section
+ offset style address. Also, there will be addresses in the code and data
that do not exist in actual sections. Not saying that you couldn't use
lldb_private::Address. I am open to suggestions though. So your though it
remove all API that take lldb::addr_t and use lldb_private::Address
everywhere all the time?

> It has always bugged me that we have these two ways of specifying

addresses. Are there many/any places that have to resolve an Address to a
real address in a process that don't have a Target readily available? That
would surprise me. I would much rather centralize on one way than adding a
third.

>
> Jim

So, does it make sense to start with lldb::addr_t replacement? In other
words, replace all instances of lldb::addr_t with Address. It'd be the
first step and first patch towards to the ability to extend it in the
future, right?

Zdenek

>
>
>>> Jim
>>>
>>>
>>>> We would need a default value for "space" (feel free to rename) that

indicates the default address space as most of our architectures would not
need this support. If we added a constructor like:

>>>>
>>>> SpaceAddress(lldb::addr_t a) : addr(a), space(kNoSpace) {}
>>>>
>>>> Then all usages of the APIs that used to take just a "lldb::addr_t"

would implicitly call this constructor and continue to act as needed. Then
we would need to allow lldb_private::Address objects to resolve to a
SpaceAddress:

>>>>
>>>> SpaceAddress lldb_private::Address::GetSpaceAddress(Target *target)

const;

>>>>
>>>> Since each lldb_private::Address has a section and each section

knows its address space. Then the tricky part is finding all locations in
the expression parser and converting those to track and use SpaceAddress.
We would probably need to modify the allocate memory packets in the RSP
protocol to be able to allocate memory in any address space as well.

>>>>
>>>> I didn't spend much time think about correct names above, so feel

free to suggest alternate naming.

>>>>
>>>> Best advice:
>>>> - make things "just work" to keep changes to a minimum and allowing

lldb::addr_t to implicitly convert to a SpaceAddress easily

>>>> - when modifying RSP, make sure to check for existence of new

feature before enabling it

>>>> - query for address space names so when we dump SpaceAddress we can

show something that means something to the user. This means we would need
to query the address space names from the current lldb_private::Process for
display.

>>>>
>>>> Submitting might go easier if we break it down into chunks:
>>>> 1 - add SpaceAddress and modify all needed APIs to use it
>>>> 2 - add ProcessGDBRemote changes that enable this support
>>>>
>>>> It will be great to support this as a first class citizen within

LLDB. You might ask the Hexagon folks if they have done anything in case
they already support this is some shape or form.

Greg, Jim, what's your opinion here?

What about having the class Address (pretty much as it is right now) and the

struct AddressBase {
lldb::addr_t m_address;
lldb::as_t m_address_space;
...
}

Another question is, which classes/code should use Address, AddressBase, and addr_t. Do you have any idea here?

Zdenek

Just a small update. I did create the class AddressBase. Class Address inherits from it. When I compare it with my first implementation, it's cleaner than the additional argument in API. I also implemented all operators to the class AddressBase, so it behaves like addr_t if you're not interested in the address space.

I thought that I'd rename the class AddressBase to addr_t and see what would happen, but then I realized that LLDB has python support and I'm not sure how this works with classes, so, any advice here?

Btw. I still don't have a clear answer to my question below...

Zdenek

As an FYI - this is another way of looking at Address spaces.. I like the word “Route” to the memory space, i think it defines the problem better.

All Armv8 chips effectively have - multiple address available to the debugger

For instance, a JTAG debugger halts an ARMV8 cpu core, and the core halts in user space - the question is what are the various address spaces a developer might want to dump memory for:

A) The current user space view of memory - to print a user space variable.

B) The current Kernel (OS) view of memory - perhaps to print data structure in kernel space

C) At the hypervisor level which is the core’s view of physical memory - perhaps the developer wants to examine a data structure or variable in the hypervisor.

D) The ARM dap - has 3 (sometime 4) memory bus interfaces. They are typically:

Dap Port 0 - is typically the main system bus, often the same as the CPU’s connection to the main system bus but not exactly

ie: CPU access to a multi-media bus, via a dedicated connection/address range, in contrast the main system bus has a different connection/route to the multimedia memory

Dap Port 1 - commonly provides access to various Coresight items for most of the cores.

Dap Port 2 - Varies - it could be an embedded Jtag controller - say with an ARM9 or other JTAG only interface)

Dap Port 3 - Varies - But often there are a few CORTEX M series CPUs - and I believe each M3 on the target must have its own dedicated DAP interface.

Assume for a moment, each of these address spaces have a name, there is the default, then there needs to be various override methods

Being able to some how specify these different “access routes” is helpful when debugging hardware at the bare metal level.

In the above, I’m not talking about looking at a complex variable (that would be really nice, ie: cast a memory address to a fancy type)

When debugging a SYSTEM - this becomes very important. Minimally being able to have a “memory window” that can specify the route is helpful - for example

  Dump Memory at : HyperVisor address 0x12345678
  Dump Memory at: Kernel address 0x45678901234
  Dump Memory using the system bus interface

Across multiple cores - you have

1) Some very common routes - ie: “In the current context” vrs “Kernel context”
These should have commonly defined names.

2) Some platforms may need to add their own “platform defined” items (ie: various armv8 routes would be semi-common)

3) Some VERY specific routes or methods that are developer defined - For example when accessing memory via the DAP MEM_AP, there are special bits in the control register (controlling security and/or cache control). Maybe the developer needs to set those a special way when performing the memory access when using this “route”

The lauterbach jtag debugger can do the above now (it is an address prefix)
The ARM debugger (If I remember correctly) can also do this somewhere in its script language.

But tools like GDB and LLDB can not

Because tools like GDB and LLDB have a scripting language (ie: Python) - being able to write a script in that scripting language and be able to specify the ROUTE is important.

For example, a script that writes to a bunch of hardware locations via the MEMAP (or possibly via different CPU) - to enable a feature so that you can run test/validation code

Examples include write to a hardware register to turn a CLOCK on, or disable/enable a security protection bit so that you can view/write to the memory location.

-Duane.

You can conceptually take this a step further. I used to work at Freescale, and supported SoCs with multiple heterogeneous cores. I provided memory spaces that let the user access these memory views:

- DCSR (debug memory, a separate bus) through the SoC
- CCSR (memory mapped config registers) through the SoC
- cache coherent physical access through the SoC
- uncached physical access through the SoC
- virtual access through a given core (PPC or StarCore)
- cache coherent physical access through a given core
- uncached physical access through a given core

I also provided a cache view which would allow the user to read/modify data and tag/status of the L1i, L1d, L2 and L3 caches.

Basically, let the user access memory (whether it was RAM, memory mapped registers, or something else) any way he or she wants. What the core sees, what the SoC sees, cacheable, uncached (so, in the backing store), or what's in the caches.

Once you have memory space support, you can make arbitrary spaces that show you whatever you want.

cache view

Debugging cache problems is always fun, being able to do this is very helpful.

You can conceptually take this a step further.

This is exactly my point, these would be in a “target specific” range of prefix names

When specifying an address, there should be some set of “common names” that all CPUs use

For example: default:0x12345, phys:0x12345, or user:0x12345, kern:0x12345, hype:0x12345 -

for default (ie: current cpu mode/configuration, used when route is not specified)

and memory spaces like physical, user, kernel, hypervisor

In Ted’s example case

Ie: DSCR:0x12345 → Translates to DSCR at address 0x12345

Where as ARM cores might have their own set of special names

Field the route value needs two field– Major = (at least 16bits, ie: cpu core) and Minor (16bits) core specific.

Also need to reserve a range for “non-core” like accesses known only by the debug agent/server/hardware interface, the user might want to say: Name: “FOO” means - access_route(X), with configuration value: (some 32bit integer) that is unknown at the debugger level, but know/understood at the lower level.

Otherwise the permutations are endless