diff mbox series

[RFC,v7,08/21] um: add nommu mode for UML library mode

Message ID ac5a99db869705b284307dea21b37068ee5ae7d2.1601960644.git.thehajime@gmail.com
State Not Applicable
Headers show
Series [RFC,v7,01/21] um: split build in kernel and host parts | expand

Commit Message

Hajime Tazaki Oct. 6, 2020, 9:44 a.m. UTC
This patch introduces the nommu operation with UML code so that host
interface can be shrineked for broader environments support.

The nommu mode is implemneted as SUBARCH of arch/um, which places at
arch/um/nommu. This SUBARCH defines mode-specific code of memory
management as well as thread implementation, along with the uapi headers
to be exported to users.

The headers we introduce in this patch are simple wrappers to the
asm-generic headers or stubs for things we don't support, such as
ptrace, DMA, signals, ELF handling and low level processor operations.

nommu mode shares most of arch/um code (irq, thread_info, process
scheduling) but implements its own facilities, which are memory
management (nommu), thread primitives (struct arch_thread), system call
interface, and console.

The outlook of updated directory structure is as follows:

   arch/um
   |-- configs         (untouched)
   |-- drivers         unuse stdio_console.c for !MMU
   |-- include
   |   |-- asm         updated with !CONFIG_MMU
   |   |-- linux       (untouched)
   |   `-- shared      updated with new functions
   |       `-- skas    (untouched)
   |   `-- uapi        added for upai header installation
   |-- kernel          updated to integrate with !MMU
   |   `-- skas        (untouched, don't use for !MMU)
   |-- nommu           SUBARCH dir (internally =um/nommu)
   |   |-- include
   |   |   |-- asm     headers for subarch specific info
   |   |   `-- uapi    headers for user-visible APIs
   |   `-- um
   |       `-- shared  headers for subarch specific info
   `-- scripts         added a script for header installation

Signed-off-by: Hajime Tazaki <thehajime@gmail.com>
Signed-off-by: Octavian Purdila <tavi.purdila@gmail.com>
---
 arch/um/nommu/Makefile                        |   1 +
 arch/um/nommu/Makefile.um                     |  22 ++++
 arch/um/nommu/include/asm/Kbuild              |   6 +
 arch/um/nommu/include/asm/archparam.h         |   1 +
 arch/um/nommu/include/asm/atomic.h            |  11 ++
 arch/um/nommu/include/asm/atomic64.h          | 114 ++++++++++++++++++
 arch/um/nommu/include/asm/bitsperlong.h       |  12 ++
 arch/um/nommu/include/asm/byteorder.h         |   7 ++
 arch/um/nommu/include/asm/cpu.h               |  13 ++
 arch/um/nommu/include/asm/elf.h               |  15 +++
 arch/um/nommu/include/asm/mm_context.h        |   8 ++
 arch/um/nommu/include/asm/processor.h         |  46 +++++++
 arch/um/nommu/include/asm/ptrace.h            |  21 ++++
 arch/um/nommu/include/asm/sched.h             |  23 ++++
 arch/um/nommu/include/asm/segment.h           |   9 ++
 arch/um/nommu/include/uapi/asm/Kbuild         |   6 +
 arch/um/nommu/include/uapi/asm/bitsperlong.h  |  11 ++
 arch/um/nommu/include/uapi/asm/byteorder.h    |  11 ++
 arch/um/nommu/include/uapi/asm/sigcontext.h   |  12 ++
 arch/um/nommu/um/delay.c                      |  31 +++++
 arch/um/nommu/um/shared/sysdep/archsetjmp.h   |  13 ++
 arch/um/nommu/um/shared/sysdep/faultinfo.h    |   8 ++
 .../nommu/um/shared/sysdep/kernel-offsets.h   |  12 ++
 arch/um/nommu/um/shared/sysdep/mcontext.h     |   9 ++
 arch/um/nommu/um/shared/sysdep/ptrace.h       |  42 +++++++
 arch/um/nommu/um/shared/sysdep/ptrace_user.h  |   7 ++
 arch/um/nommu/um/unimplemented.c              |  70 +++++++++++
 arch/um/nommu/um/user_constants.h             |  13 ++
 28 files changed, 554 insertions(+)
 create mode 100644 arch/um/nommu/Makefile
 create mode 100644 arch/um/nommu/Makefile.um
 create mode 100644 arch/um/nommu/include/asm/Kbuild
 create mode 100644 arch/um/nommu/include/asm/archparam.h
 create mode 100644 arch/um/nommu/include/asm/atomic.h
 create mode 100644 arch/um/nommu/include/asm/atomic64.h
 create mode 100644 arch/um/nommu/include/asm/bitsperlong.h
 create mode 100644 arch/um/nommu/include/asm/byteorder.h
 create mode 100644 arch/um/nommu/include/asm/cpu.h
 create mode 100644 arch/um/nommu/include/asm/elf.h
 create mode 100644 arch/um/nommu/include/asm/mm_context.h
 create mode 100644 arch/um/nommu/include/asm/processor.h
 create mode 100644 arch/um/nommu/include/asm/ptrace.h
 create mode 100644 arch/um/nommu/include/asm/sched.h
 create mode 100644 arch/um/nommu/include/asm/segment.h
 create mode 100644 arch/um/nommu/include/uapi/asm/Kbuild
 create mode 100644 arch/um/nommu/include/uapi/asm/bitsperlong.h
 create mode 100644 arch/um/nommu/include/uapi/asm/byteorder.h
 create mode 100644 arch/um/nommu/include/uapi/asm/sigcontext.h
 create mode 100644 arch/um/nommu/um/delay.c
 create mode 100644 arch/um/nommu/um/shared/sysdep/archsetjmp.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/faultinfo.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/kernel-offsets.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/mcontext.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/ptrace.h
 create mode 100644 arch/um/nommu/um/shared/sysdep/ptrace_user.h
 create mode 100644 arch/um/nommu/um/unimplemented.c
 create mode 100644 arch/um/nommu/um/user_constants.h

Comments

Johannes Berg Oct. 7, 2020, 3:44 p.m. UTC | #1
On Tue, 2020-10-06 at 18:44 +0900, Hajime Tazaki wrote:
> This patch introduces the nommu operation with UML code so that host
> interface can be shrineked for broader environments support.

shrunk

> The nommu mode is implemneted as SUBARCH of arch/um, which places at

implemented

> arch/um/nommu. This SUBARCH defines mode-specific code of memory
> management as well as thread implementation, along with the uapi headers
> to be exported to users.
> 
> The headers we introduce in this patch are simple wrappers to the
> asm-generic headers or stubs for things we don't support, such as
> ptrace, DMA, signals, ELF handling and low level processor operations.
> 
> nommu mode shares most of arch/um code (irq, thread_info, process
> scheduling) but implements its own facilities, which are memory
> management (nommu), thread primitives (struct arch_thread), system call
> interface, and console.
> 
> The outlook of updated directory structure is as follows:
> 
>    arch/um
>    |-- configs         (untouched)
>    |-- drivers         unuse stdio_console.c for !MMU
>    |-- include
>    |   |-- asm         updated with !CONFIG_MMU
>    |   |-- linux       (untouched)
>    |   `-- shared      updated with new functions
>    |       `-- skas    (untouched)
>    |   `-- uapi        added for upai header installation
>    |-- kernel          updated to integrate with !MMU
>    |   `-- skas        (untouched, don't use for !MMU)
>    |-- nommu           SUBARCH dir (internally =um/nommu)
>    |   |-- include
>    |   |   |-- asm     headers for subarch specific info
>    |   |   `-- uapi    headers for user-visible APIs
>    |   `-- um
>    |       `-- shared  headers for subarch specific info
>    `-- scripts         added a script for header installation

That seems awkward. Might be nice now for "as little changes as
possible", but eventually it seems it would be better to separate that
out into arch/um/{common,nommu,mmu}/ or something like that?

Or perhaps something like

	arch/um/{common,lkl,full}

or something? Not sure I like 'full' though. 'vm'? Hmm.

(also, scripts/ doesn't exist in this patch?)

> +++ b/arch/um/nommu/Makefile
> @@ -0,0 +1 @@
> +#

hmm? maybe add a comment why an empty makefile is needed.

> diff --git a/arch/um/nommu/Makefile.um b/arch/um/nommu/Makefile.um
> new file mode 100644
> index 000000000000..3808462d8283
> --- /dev/null
> +++ b/arch/um/nommu/Makefile.um

[...]

> +ifeq ($(shell uname -s), Linux)
> +NPROC=$(shell nproc)
> +else # e.g., FreeBSD
> +NPROC=$(shell sysctl -n hw.ncpu)
> +endif

That seems very inappropriate here.

> +
> +um_headers_install: $(objtree)/$(HOST_DIR)/include/generated/uapi/asm/syscall_defs.h headers
> +# if syscall_defs.h is newer than generated headers (autoconf.h)
> +	$(Q)if [ ! -r $(objtree)/tools/um/include/lkl/autoconf.h ] || \
> +	  [ $< -nt $(objtree)/tools/um/include/lkl/autoconf.h ]; then \
> +		$(srctree)/$(ARCH_DIR)/scripts/headers_install.py \
> +			$(subst -j,-j$(NPROC),$(findstring -j,$(MAKEFLAGS))) \

Yeah ... just don't.

> +++ b/arch/um/nommu/include/asm/atomic.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __UM_NOMMU_ATOMIC_H
> +#define __UM_NOMMU_ATOMIC_H
> +
> +#include <asm-generic/atomic.h>
> +
> +#ifndef CONFIG_GENERIC_ATOMIC64
> +#include "atomic64.h"
> +#endif /* !CONFIG_GENERIC_ATOMIC64 */
> +
> +#endif
> diff --git a/arch/um/nommu/include/asm/atomic64.h b/arch/um/nommu/include/asm/atomic64.h
> new file mode 100644
> index 000000000000..949360dea7af
> --- /dev/null
> +++ b/arch/um/nommu/include/asm/atomic64.h

That doesn't make sense to me, you can control CONFIG_GENERIC_ATOMIC64
to be on, and don't need the ifdef and this file?

> diff --git a/arch/um/nommu/include/asm/bitsperlong.h b/arch/um/nommu/include/asm/bitsperlong.h
> new file mode 100644
> index 000000000000..a150cee41e75
> --- /dev/null
> +++ b/arch/um/nommu/include/asm/bitsperlong.h
> @@ -0,0 +1,12 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __UM_NOMMU_BITSPERLONG_H
> +#define __UM_NOMMU_BITSPERLONG_H
> +
> +#include <uapi/asm/bitsperlong.h>
> +
> +#define BITS_PER_LONG __BITS_PER_LONG
> +
> +#define BITS_PER_LONG_LONG 64
> +
> +#endif

That's very similar to the contents of include/asm-
generic/bitsperlong.h, add comments why it's needed?

> diff --git a/arch/um/nommu/include/asm/byteorder.h b/arch/um/nommu/include/asm/byteorder.h
> new file mode 100644
> index 000000000000..920a5fd26cad
> --- /dev/null
> +++ b/arch/um/nommu/include/asm/byteorder.h
> @@ -0,0 +1,7 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __UM_NOMMU_BYTEORDER_H
> +#define __UM_NOMMU_BYTEORDER_H
> +
> +#include <uapi/asm/byteorder.h>
> +
> +#endif

Not sure why this file even exists, it doesn't for any other arch
(except for h8300 which seems odd).

> diff --git a/arch/um/nommu/include/asm/elf.h b/arch/um/nommu/include/asm/elf.h
> new file mode 100644
> index 000000000000..edcf63edeed1
> --- /dev/null
> +++ b/arch/um/nommu/include/asm/elf.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __UM_NOMMU_ELF_H
> +#define __UM_NOMMU_ELF_H
> +
> +#define elf_check_arch(x) 0

Please add a comment ...

> +#ifdef CONFIG_64BIT
> +#define ELF_CLASS ELFCLASS64
> +#else
> +#define ELF_CLASS ELFCLASS32
> +#endif
> +
> +#define elf_gregset_t long
> +#define elf_fpregset_t double

Also here.

> +#ifndef __UM_NOMMU_SCHED_H
> +#define __UM_NOMMU_SCHED_H
> +
> +#include <linux/sched.h>
> +#include <uapi/asm/host_ops.h>
> +
> +static inline void thread_sched_jb(void)
> +{
> +	if (test_ti_thread_flag(current_thread_info(), TIF_HOST_THREAD)) {
> +		set_ti_thread_flag(current_thread_info(), TIF_SCHED_JB);
> +		set_current_state(TASK_UNINTERRUPTIBLE);
> +		lkl_ops->jmp_buf_set(&current_thread_info()->task->thread.arch.sched_jb,
> +				     schedule);
> +	} else {
> +		lkl_bug("%s can be used only for host task", __func__);
> +	}
> +}

What's "thread_sched_jb"? Doesn't really seem to exist? Neither does
"TIF_SCHED_JB", at least in my kernel?

Looks like that's added by a later patch, should probably then add this
file also only later so it's actually consistent and one can review all
the pieces together.

> +++ b/arch/um/nommu/include/uapi/asm/Kbuild
> @@ -0,0 +1,6 @@
> +# UAPI Header export list
> +
> +generated-y += syscall_defs.h
> +
> +# no generated-y since we need special user headers handling
> +# see arch/um/script/headers_install.py

Also doesn't exist yet.

> +++ b/arch/um/nommu/um/delay.c

why the double um/ path?

> +/* skas/process.c */
> +void halt_skas(void)
> +{}

nit: missing blank line after this

> +int is_skas_winch(int pid, int fd, void *data)
> +{
> +	return 0;
> +}
> +void reboot_skas(void)
> +{}
> +
> +int __init start_uml(void)
> +{
> +	return 0;
> +}

That seems odd?

Might be better to have an own os.h, or split that into os-uml.h and
os-lkl.h or so?

johannes
Hajime Tazaki Oct. 9, 2020, 3:38 a.m. UTC | #2
Hello Johannes,

On Thu, 08 Oct 2020 00:44:12 +0900,
Johannes Berg wrote:
> 
> On Tue, 2020-10-06 at 18:44 +0900, Hajime Tazaki wrote:
> > This patch introduces the nommu operation with UML code so that host
> > interface can be shrineked for broader environments support.
> 
> shrunk
> 
> > The nommu mode is implemneted as SUBARCH of arch/um, which places at
> 
> implemented

thanks; will fix both in the next round.

> > arch/um/nommu. This SUBARCH defines mode-specific code of memory
> > management as well as thread implementation, along with the uapi headers
> > to be exported to users.
> > 
> > The headers we introduce in this patch are simple wrappers to the
> > asm-generic headers or stubs for things we don't support, such as
> > ptrace, DMA, signals, ELF handling and low level processor operations.
> > 
> > nommu mode shares most of arch/um code (irq, thread_info, process
> > scheduling) but implements its own facilities, which are memory
> > management (nommu), thread primitives (struct arch_thread), system call
> > interface, and console.
> > 
> > The outlook of updated directory structure is as follows:
> > 
> >    arch/um
> >    |-- configs         (untouched)
> >    |-- drivers         unuse stdio_console.c for !MMU
> >    |-- include
> >    |   |-- asm         updated with !CONFIG_MMU
> >    |   |-- linux       (untouched)
> >    |   `-- shared      updated with new functions
> >    |       `-- skas    (untouched)
> >    |   `-- uapi        added for upai header installation
> >    |-- kernel          updated to integrate with !MMU
> >    |   `-- skas        (untouched, don't use for !MMU)
> >    |-- nommu           SUBARCH dir (internally =um/nommu)
> >    |   |-- include
> >    |   |   |-- asm     headers for subarch specific info
> >    |   |   `-- uapi    headers for user-visible APIs
> >    |   `-- um
> >    |       `-- shared  headers for subarch specific info
> >    `-- scripts         added a script for header installation
> 
> That seems awkward. Might be nice now for "as little changes as
> possible", but eventually it seems it would be better to separate that
> out into arch/um/{common,nommu,mmu}/ or something like that?
> 
> Or perhaps something like
> 
> 	arch/um/{common,lkl,full}
> 
> or something? Not sure I like 'full' though. 'vm'? Hmm.

(I will leave this to the other thread if any)

> (also, scripts/ doesn't exist in this patch?)
> 
> > +++ b/arch/um/nommu/Makefile
> > @@ -0,0 +1 @@
> > +#
> 
> hmm? maybe add a comment why an empty makefile is needed.

Thanks, we will.

> > diff --git a/arch/um/nommu/Makefile.um b/arch/um/nommu/Makefile.um
> > new file mode 100644
> > index 000000000000..3808462d8283
> > --- /dev/null
> > +++ b/arch/um/nommu/Makefile.um
> 
> [...]
> 
> > +ifeq ($(shell uname -s), Linux)
> > +NPROC=$(shell nproc)
> > +else # e.g., FreeBSD
> > +NPROC=$(shell sysctl -n hw.ncpu)
> > +endif
> 
> That seems very inappropriate here.

Will cut the FreeBSD part.

> > +
> > +um_headers_install: $(objtree)/$(HOST_DIR)/include/generated/uapi/asm/syscall_defs.h headers
> > +# if syscall_defs.h is newer than generated headers (autoconf.h)
> > +	$(Q)if [ ! -r $(objtree)/tools/um/include/lkl/autoconf.h ] || \
> > +	  [ $< -nt $(objtree)/tools/um/include/lkl/autoconf.h ]; then \
> > +		$(srctree)/$(ARCH_DIR)/scripts/headers_install.py \
> > +			$(subst -j,-j$(NPROC),$(findstring -j,$(MAKEFLAGS))) \
> 
> Yeah ... just don't.

Will clean up this part.

> > +++ b/arch/um/nommu/include/asm/atomic.h
> > @@ -0,0 +1,11 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef __UM_NOMMU_ATOMIC_H
> > +#define __UM_NOMMU_ATOMIC_H
> > +
> > +#include <asm-generic/atomic.h>
> > +
> > +#ifndef CONFIG_GENERIC_ATOMIC64
> > +#include "atomic64.h"
> > +#endif /* !CONFIG_GENERIC_ATOMIC64 */
> > +
> > +#endif
> > diff --git a/arch/um/nommu/include/asm/atomic64.h b/arch/um/nommu/include/asm/atomic64.h
> > new file mode 100644
> > index 000000000000..949360dea7af
> > --- /dev/null
> > +++ b/arch/um/nommu/include/asm/atomic64.h
> 
> That doesn't make sense to me, you can control CONFIG_GENERIC_ATOMIC64
> to be on, and don't need the ifdef and this file?

We were suggested to not use GENERIC_ATOMIC64 on 64bit build during
our v3 patchset.  So we actually control CONFIG_GENERIC_ATOMIC64 to be
on only when !64BIT, and thus need atomic64.h for the 64BIT build.

https://lwn.net/ml/linux-arch/20200205093454.GG14879@hirez.programming.kicks-ass.net/

> > diff --git a/arch/um/nommu/include/asm/bitsperlong.h b/arch/um/nommu/include/asm/bitsperlong.h
> > new file mode 100644
> > index 000000000000..a150cee41e75
> > --- /dev/null
> > +++ b/arch/um/nommu/include/asm/bitsperlong.h
> > @@ -0,0 +1,12 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef __UM_NOMMU_BITSPERLONG_H
> > +#define __UM_NOMMU_BITSPERLONG_H
> > +
> > +#include <uapi/asm/bitsperlong.h>
> > +
> > +#define BITS_PER_LONG __BITS_PER_LONG
> > +
> > +#define BITS_PER_LONG_LONG 64
> > +
> > +#endif
> 
> That's very similar to the contents of include/asm-
> generic/bitsperlong.h, add comments why it's needed?

thanks, it seems that this is unnecessary now.  will fix them.

> > diff --git a/arch/um/nommu/include/asm/byteorder.h b/arch/um/nommu/include/asm/byteorder.h
> > new file mode 100644
> > index 000000000000..920a5fd26cad
> > --- /dev/null
> > +++ b/arch/um/nommu/include/asm/byteorder.h
> > @@ -0,0 +1,7 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef __UM_NOMMU_BYTEORDER_H
> > +#define __UM_NOMMU_BYTEORDER_H
> > +
> > +#include <uapi/asm/byteorder.h>
> > +
> > +#endif
> 
> Not sure why this file even exists, it doesn't for any other arch
> (except for h8300 which seems odd).

You're right.  We will remove this.

> > diff --git a/arch/um/nommu/include/asm/elf.h b/arch/um/nommu/include/asm/elf.h
> > new file mode 100644
> > index 000000000000..edcf63edeed1
> > --- /dev/null
> > +++ b/arch/um/nommu/include/asm/elf.h
> > @@ -0,0 +1,15 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +#ifndef __UM_NOMMU_ELF_H
> > +#define __UM_NOMMU_ELF_H
> > +
> > +#define elf_check_arch(x) 0
> 
> Please add a comment ...
>
> > +#ifdef CONFIG_64BIT
> > +#define ELF_CLASS ELFCLASS64
> > +#else
> > +#define ELF_CLASS ELFCLASS32
> > +#endif
> > +
> > +#define elf_gregset_t long
> > +#define elf_fpregset_t double
> 
> Also here.

thanks, will add the comments.

> > +#ifndef __UM_NOMMU_SCHED_H
> > +#define __UM_NOMMU_SCHED_H
> > +
> > +#include <linux/sched.h>
> > +#include <uapi/asm/host_ops.h>
> > +
> > +static inline void thread_sched_jb(void)
> > +{
> > +	if (test_ti_thread_flag(current_thread_info(), TIF_HOST_THREAD)) {
> > +		set_ti_thread_flag(current_thread_info(), TIF_SCHED_JB);
> > +		set_current_state(TASK_UNINTERRUPTIBLE);
> > +		lkl_ops->jmp_buf_set(&current_thread_info()->task->thread.arch.sched_jb,
> > +				     schedule);
> > +	} else {
> > +		lkl_bug("%s can be used only for host task", __func__);
> > +	}
> > +}
> 
> What's "thread_sched_jb"? Doesn't really seem to exist? Neither does
> "TIF_SCHED_JB", at least in my kernel?
> 
> Looks like that's added by a later patch, should probably then add this
> file also only later so it's actually consistent and one can review all
> the pieces together.

I understand. I will move this file to the later patch (11/21).

> > +++ b/arch/um/nommu/include/uapi/asm/Kbuild
> > @@ -0,0 +1,6 @@
> > +# UAPI Header export list
> > +
> > +generated-y += syscall_defs.h
> > +
> > +# no generated-y since we need special user headers handling
> > +# see arch/um/script/headers_install.py
> 
> Also doesn't exist yet.

The message is incorrect since uapi header infra has changed.
This also applies to the comment in arch/um/nommu/include/asm/Kbuild.

Will fix both in the next round.

> > +++ b/arch/um/nommu/um/delay.c
> 
> why the double um/ path?

This is because now in arch/um/Makefile,

 - SUBARCH := um/nommu
 - HEADER_ARCH := $(SUBARCH)
 - HOST_DIR := arch/$(HEADER_ARCH)
 - core-y += $(HOST_DIR)/um

the last line expands as arch/um/nommu/um.

> > +/* skas/process.c */
> > +void halt_skas(void)
> > +{}
> 
> nit: missing blank line after this

will fix this and other parts of the whole patchset.

> > +int is_skas_winch(int pid, int fd, void *data)
> > +{
> > +	return 0;
> > +}
> > +void reboot_skas(void)
> > +{}
> > +
> > +int __init start_uml(void)
> > +{
> > +	return 0;
> > +}
> 
> That seems odd?
> 
> Might be better to have an own os.h, or split that into os-uml.h and
> os-lkl.h or so?

Okay, we will think about this.

-- Hajime
Johannes Berg Oct. 9, 2020, 4:06 p.m. UTC | #3
On Fri, 2020-10-09 at 12:38 +0900, Hajime Tazaki wrote:
> 
> > > +++ b/arch/um/nommu/Makefile.um
> > 
> > [...]
> > 
> > > +ifeq ($(shell uname -s), Linux)
> > > +NPROC=$(shell nproc)
> > > +else # e.g., FreeBSD
> > > +NPROC=$(shell sysctl -n hw.ncpu)
> > > +endif
> > 
> > That seems very inappropriate here.
> 
> Will cut the FreeBSD part.

But even the NPROC and -j flag mangling seems ... awful?

> > > --- /dev/null
> > > +++ b/arch/um/nommu/include/asm/atomic64.h
> > 
> > That doesn't make sense to me, you can control CONFIG_GENERIC_ATOMIC64
> > to be on, and don't need the ifdef and this file?
> 
> We were suggested to not use GENERIC_ATOMIC64 on 64bit build during
> our v3 patchset.  So we actually control CONFIG_GENERIC_ATOMIC64 to be
> on only when !64BIT, and thus need atomic64.h for the 64BIT build.
> 
> https://lwn.net/ml/linux-arch/20200205093454.GG14879@hirez.programming.kicks-ass.net/

Well, yeah, but your architecture _is_ a piece of crap in needing
atomic64 emulation? :-)

How about just using the real atomic64 implementation like UML normally
does? I mean, falling back to the actual underlying CPU. Or even gcc
intrinsics?

You've basically re-implemented CONFIG_GENERIC_ATOMIC64, so perhaps
you've hidden it from PeterZ's view now because you're no longer
touching the real generic atomic64 (which is for 32-bit machines), but
that doesn't actually make this any *better*. Arguably *worse* since
you've just copied it ...

> > > +++ b/arch/um/nommu/um/delay.c
> > 
> > why the double um/ path?
> 
> This is because now in arch/um/Makefile,
> 
>  - SUBARCH := um/nommu
>  - HEADER_ARCH := $(SUBARCH)
>  - HOST_DIR := arch/$(HEADER_ARCH)
>  - core-y += $(HOST_DIR)/um
> 
> the last line expands as arch/um/nommu/um.

But is there a reason for it? Couldn't it be changed?

Anyway, we're still debating the whole build system and layout so not
much point in going into the details now ...

johannes
Hajime Tazaki Oct. 20, 2020, 8:44 a.m. UTC | #4
Hello,

sorry for the late response.

On Sat, 10 Oct 2020 01:06:03 +0900,
Johannes Berg wrote:
> 
> On Fri, 2020-10-09 at 12:38 +0900, Hajime Tazaki wrote:
> > 
> > > > +++ b/arch/um/nommu/Makefile.um
> > > 
> > > [...]
> > > 
> > > > +ifeq ($(shell uname -s), Linux)
> > > > +NPROC=$(shell nproc)
> > > > +else # e.g., FreeBSD
> > > > +NPROC=$(shell sysctl -n hw.ncpu)
> > > > +endif
> > > 
> > > That seems very inappropriate here.
> > 
> > Will cut the FreeBSD part.
> 
> But even the NPROC and -j flag mangling seems ... awful?

Okay, we won't use the -j flag at this place.

> > > > --- /dev/null
> > > > +++ b/arch/um/nommu/include/asm/atomic64.h
> > > 
> > > That doesn't make sense to me, you can control CONFIG_GENERIC_ATOMIC64
> > > to be on, and don't need the ifdef and this file?
> > 
> > We were suggested to not use GENERIC_ATOMIC64 on 64bit build during
> > our v3 patchset.  So we actually control CONFIG_GENERIC_ATOMIC64 to be
> > on only when !64BIT, and thus need atomic64.h for the 64BIT build.
> > 
> > https://lwn.net/ml/linux-arch/20200205093454.GG14879@hirez.programming.kicks-ass.net/
> 
> Well, yeah, but your architecture _is_ a piece of crap in needing
> atomic64 emulation? :-)
> 
> How about just using the real atomic64 implementation like UML normally
> does? I mean, falling back to the actual underlying CPU. Or even gcc
> intrinsics?
> 
> You've basically re-implemented CONFIG_GENERIC_ATOMIC64, so perhaps
> you've hidden it from PeterZ's view now because you're no longer
> touching the real generic atomic64 (which is for 32-bit machines), but
> that doesn't actually make this any *better*. Arguably *worse* since
> you've just copied it ...

We're trying to reimplement atomic64 ops with gcc builtins.

We're now trying to address all of comments we got, and will get here
back once we have done.

-- Hajime
diff mbox series

Patch

diff --git a/arch/um/nommu/Makefile b/arch/um/nommu/Makefile
new file mode 100644
index 000000000000..792d6005489e
--- /dev/null
+++ b/arch/um/nommu/Makefile
@@ -0,0 +1 @@ 
+#
diff --git a/arch/um/nommu/Makefile.um b/arch/um/nommu/Makefile.um
new file mode 100644
index 000000000000..3808462d8283
--- /dev/null
+++ b/arch/um/nommu/Makefile.um
@@ -0,0 +1,22 @@ 
+KBUILD_CFLAGS += -fno-builtin -fPIC
+ELF_FORMAT=$(shell $(LD) -r -print-output-format)
+
+ifeq ($(shell uname -s), Linux)
+NPROC=$(shell nproc)
+else # e.g., FreeBSD
+NPROC=$(shell sysctl -n hw.ncpu)
+endif
+
+um_headers_install: $(objtree)/$(HOST_DIR)/include/generated/uapi/asm/syscall_defs.h headers
+# if syscall_defs.h is newer than generated headers (autoconf.h)
+	$(Q)if [ ! -r $(objtree)/tools/um/include/lkl/autoconf.h ] || \
+	  [ $< -nt $(objtree)/tools/um/include/lkl/autoconf.h ]; then \
+		$(srctree)/$(ARCH_DIR)/scripts/headers_install.py \
+			$(subst -j,-j$(NPROC),$(findstring -j,$(MAKEFLAGS))) \
+			$(INSTALL_PATH)/include ; \
+	fi
+
+$(objtree)/$(HOST_DIR)/include/generated/uapi/asm/syscall_defs.h: vmlinux
+	$(Q)$(OBJCOPY) -j .syscall_defs -O binary --set-section-flags .syscall_defs=alloc $< $@
+	$(Q) export tmpfile=$(shell mktemp); \
+	sed 's/\x0//g' $@ > $$tmpfile; mv $$tmpfile $@ ; rm -f $$tmpfile
diff --git a/arch/um/nommu/include/asm/Kbuild b/arch/um/nommu/include/asm/Kbuild
new file mode 100644
index 000000000000..2532e1a0a0d1
--- /dev/null
+++ b/arch/um/nommu/include/asm/Kbuild
@@ -0,0 +1,6 @@ 
+generic-y += cmpxchg.h
+generic-y += local64.h
+generic-y += seccomp.h
+generic-y += string.h
+generic-y += syscall.h
+generic-y += user.h
diff --git a/arch/um/nommu/include/asm/archparam.h b/arch/um/nommu/include/asm/archparam.h
new file mode 100644
index 000000000000..ea32a7d3cf1b
--- /dev/null
+++ b/arch/um/nommu/include/asm/archparam.h
@@ -0,0 +1 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
diff --git a/arch/um/nommu/include/asm/atomic.h b/arch/um/nommu/include/asm/atomic.h
new file mode 100644
index 000000000000..63e2e16bda92
--- /dev/null
+++ b/arch/um/nommu/include/asm/atomic.h
@@ -0,0 +1,11 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_ATOMIC_H
+#define __UM_NOMMU_ATOMIC_H
+
+#include <asm-generic/atomic.h>
+
+#ifndef CONFIG_GENERIC_ATOMIC64
+#include "atomic64.h"
+#endif /* !CONFIG_GENERIC_ATOMIC64 */
+
+#endif
diff --git a/arch/um/nommu/include/asm/atomic64.h b/arch/um/nommu/include/asm/atomic64.h
new file mode 100644
index 000000000000..949360dea7af
--- /dev/null
+++ b/arch/um/nommu/include/asm/atomic64.h
@@ -0,0 +1,114 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_ATOMIC64_H
+#define __UM_NOMMU_ATOMIC64_H
+
+#include <linux/types.h>
+
+#ifdef CONFIG_SMP
+#error "SMP is not supported on this platform"
+#else
+#define ATOMIC64_OP(op, c_op)					\
+	static inline void atomic64_##op(s64 i, atomic64_t *v)	\
+	{							\
+		unsigned long flags;				\
+								\
+		raw_local_irq_save(flags);			\
+		v->counter = v->counter c_op i;			\
+		raw_local_irq_restore(flags);			\
+	}
+
+#define ATOMIC64_OP_RETURN(op, c_op)					\
+	static inline s64 atomic64_##op##_return(s64 i, atomic64_t *v)	\
+	{								\
+		unsigned long flags;					\
+		s64 ret;						\
+									\
+		raw_local_irq_save(flags);				\
+		ret = (v->counter = v->counter c_op i);			\
+		raw_local_irq_restore(flags);				\
+									\
+		return ret;						\
+	}
+
+#define ATOMIC64_FETCH_OP(op, c_op)					\
+	static inline s64 atomic64_fetch_##op(s64 i, atomic64_t *v)	\
+	{								\
+		unsigned long flags;					\
+		s64 ret;						\
+									\
+		raw_local_irq_save(flags);				\
+		ret = v->counter;					\
+		v->counter = v->counter c_op i;				\
+		raw_local_irq_restore(flags);				\
+									\
+		return ret;						\
+	}
+#endif /* CONFIG_SMP */
+
+#ifndef atomic64_add_return
+ATOMIC64_OP_RETURN(add, +)
+#endif
+
+#ifndef atomic64_sub_return
+	ATOMIC64_OP_RETURN(sub, -)
+#endif
+
+#ifndef atomic64_fetch_add
+	ATOMIC64_FETCH_OP(add, +)
+#endif
+
+#ifndef atomic64_fetch_sub
+	ATOMIC64_FETCH_OP(sub, -)
+#endif
+
+#ifndef atomic64_fetch_and
+	ATOMIC64_FETCH_OP(and, &)
+#endif
+
+#ifndef atomic64_fetch_or
+	ATOMIC64_FETCH_OP(or, |)
+#endif
+
+#ifndef atomic64_fetch_xor
+	ATOMIC64_FETCH_OP(xor, ^)
+#endif
+
+#ifndef atomic64_and
+	ATOMIC64_OP(and, &)
+#endif
+
+#ifndef atomic64_or
+	ATOMIC64_OP(or, |)
+#endif
+
+#ifndef atomic64_xor
+	ATOMIC64_OP(xor, ^)
+#endif
+
+#undef ATOMIC64_FETCH_OP
+#undef ATOMIC64_OP_RETURN
+#undef ATOMIC64_OP
+
+
+#define ATOMIC64_INIT(i)       { (i) }
+
+	static inline void atomic64_add(s64 i, atomic64_t *v)
+{
+	atomic64_add_return(i, v);
+}
+
+static inline void atomic64_sub(s64 i, atomic64_t *v)
+{
+	atomic64_sub_return(i, v);
+}
+
+#ifndef atomic64_read
+#define atomic64_read(v)       READ_ONCE((v)->counter)
+#endif
+
+#define atomic64_set(v, i) WRITE_ONCE(((v)->counter), (i))
+
+#define atomic64_xchg(ptr, v)          (xchg(&(ptr)->counter, (v)))
+#define atomic64_cmpxchg(v, old, new)  (cmpxchg(&((v)->counter), (old), (new)))
+
+#endif /* __LKL_ATOMIC64_H */
diff --git a/arch/um/nommu/include/asm/bitsperlong.h b/arch/um/nommu/include/asm/bitsperlong.h
new file mode 100644
index 000000000000..a150cee41e75
--- /dev/null
+++ b/arch/um/nommu/include/asm/bitsperlong.h
@@ -0,0 +1,12 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_BITSPERLONG_H
+#define __UM_NOMMU_BITSPERLONG_H
+
+#include <uapi/asm/bitsperlong.h>
+
+#define BITS_PER_LONG __BITS_PER_LONG
+
+#define BITS_PER_LONG_LONG 64
+
+#endif
+
diff --git a/arch/um/nommu/include/asm/byteorder.h b/arch/um/nommu/include/asm/byteorder.h
new file mode 100644
index 000000000000..920a5fd26cad
--- /dev/null
+++ b/arch/um/nommu/include/asm/byteorder.h
@@ -0,0 +1,7 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_BYTEORDER_H
+#define __UM_NOMMU_BYTEORDER_H
+
+#include <uapi/asm/byteorder.h>
+
+#endif
diff --git a/arch/um/nommu/include/asm/cpu.h b/arch/um/nommu/include/asm/cpu.h
new file mode 100644
index 000000000000..c101c078ef21
--- /dev/null
+++ b/arch/um/nommu/include/asm/cpu.h
@@ -0,0 +1,13 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_CPU_H
+#define __UM_NOMMU_CPU_H
+
+int lkl_cpu_get(void);
+void lkl_cpu_put(void);
+int lkl_cpu_try_run_irq(int irq);
+int lkl_cpu_init(void);
+void lkl_cpu_wait_shutdown(void);
+void lkl_cpu_change_owner(lkl_thread_t owner);
+void lkl_cpu_set_irqs_pending(void);
+
+#endif
diff --git a/arch/um/nommu/include/asm/elf.h b/arch/um/nommu/include/asm/elf.h
new file mode 100644
index 000000000000..edcf63edeed1
--- /dev/null
+++ b/arch/um/nommu/include/asm/elf.h
@@ -0,0 +1,15 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_ELF_H
+#define __UM_NOMMU_ELF_H
+
+#define elf_check_arch(x) 0
+
+#ifdef CONFIG_64BIT
+#define ELF_CLASS ELFCLASS64
+#else
+#define ELF_CLASS ELFCLASS32
+#endif
+
+#define elf_gregset_t long
+#define elf_fpregset_t double
+#endif
diff --git a/arch/um/nommu/include/asm/mm_context.h b/arch/um/nommu/include/asm/mm_context.h
new file mode 100644
index 000000000000..a2e53984aabd
--- /dev/null
+++ b/arch/um/nommu/include/asm/mm_context.h
@@ -0,0 +1,8 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_MM_CONTEXT_H
+#define __UM_NOMMU_MM_CONTEXT_H
+
+struct uml_arch_mm_context {
+};
+
+#endif
diff --git a/arch/um/nommu/include/asm/processor.h b/arch/um/nommu/include/asm/processor.h
new file mode 100644
index 000000000000..3e8ba870caaf
--- /dev/null
+++ b/arch/um/nommu/include/asm/processor.h
@@ -0,0 +1,46 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_PROCESSOR_H
+#define __UM_NOMMU_PROCESSOR_H
+
+#include <asm/host_ops.h>
+
+struct arch_thread {
+	struct lkl_sem *sched_sem;
+	bool dead;
+	lkl_thread_t tid;
+	struct lkl_jmp_buf sched_jb;
+	unsigned long stackend;
+};
+
+#include <asm/ptrace-generic.h>
+#include <asm/processor-generic.h>
+
+#define INIT_ARCH_THREAD {}
+#define task_pt_regs(tsk) (struct pt_regs *)(NULL)
+
+static inline void cpu_relax(void)
+{
+	unsigned long flags;
+
+	/* since this is usually called in a tight loop waiting for some
+	 * external condition (e.g. jiffies) lets run interrupts now to allow
+	 * the external condition to propagate
+	 */
+	local_irq_save(flags);
+	local_irq_restore(flags);
+}
+
+#define KSTK_EIP(tsk)	(0)
+#define KSTK_ESP(tsk)	(0)
+
+static inline void trap_init(void)
+{
+}
+
+static inline void arch_copy_thread(struct arch_thread *from,
+				    struct arch_thread *to)
+{
+	panic("unimplemented %s: fork isn't supported yet", __func__);
+}
+
+#endif
diff --git a/arch/um/nommu/include/asm/ptrace.h b/arch/um/nommu/include/asm/ptrace.h
new file mode 100644
index 000000000000..b214410e9825
--- /dev/null
+++ b/arch/um/nommu/include/asm/ptrace.h
@@ -0,0 +1,21 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_PTRACE_H
+#define __UM_NOMMU_PTRACE_H
+
+#include <linux/errno.h>
+
+static int reg_dummy __attribute__((unused));
+
+#define PT_REGS_ORIG_SYSCALL(r) (reg_dummy)
+#define PT_REGS_SYSCALL_RET(r) (reg_dummy)
+#define PT_REGS_SET_SYSCALL_RETURN(r, res) (reg_dummy = (res))
+#define REGS_SP(r) (reg_dummy)
+
+#define user_mode(regs) 0
+#define kernel_mode(regs) 1
+#define profile_pc(regs) 0
+#define user_stack_pointer(regs) 0
+
+extern void new_thread_handler(void);
+
+#endif
diff --git a/arch/um/nommu/include/asm/sched.h b/arch/um/nommu/include/asm/sched.h
new file mode 100644
index 000000000000..a4496f482633
--- /dev/null
+++ b/arch/um/nommu/include/asm/sched.h
@@ -0,0 +1,23 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_SCHED_H
+#define __UM_NOMMU_SCHED_H
+
+#include <linux/sched.h>
+#include <uapi/asm/host_ops.h>
+
+static inline void thread_sched_jb(void)
+{
+	if (test_ti_thread_flag(current_thread_info(), TIF_HOST_THREAD)) {
+		set_ti_thread_flag(current_thread_info(), TIF_SCHED_JB);
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		lkl_ops->jmp_buf_set(&current_thread_info()->task->thread.arch.sched_jb,
+				     schedule);
+	} else {
+		lkl_bug("%s can be used only for host task", __func__);
+	}
+}
+
+void switch_to_host_task(struct task_struct *);
+int host_task_stub(void *unused);
+
+#endif
diff --git a/arch/um/nommu/include/asm/segment.h b/arch/um/nommu/include/asm/segment.h
new file mode 100644
index 000000000000..5608da95cb60
--- /dev/null
+++ b/arch/um/nommu/include/asm/segment.h
@@ -0,0 +1,9 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_SEGMENT_H
+#define __UM_NOMMU_SEGMENT_H
+
+typedef struct {
+	unsigned long seg;
+} mm_segment_t;
+
+#endif /* _ASM_LKL_SEGMENT_H */
diff --git a/arch/um/nommu/include/uapi/asm/Kbuild b/arch/um/nommu/include/uapi/asm/Kbuild
new file mode 100644
index 000000000000..0d55c408dac2
--- /dev/null
+++ b/arch/um/nommu/include/uapi/asm/Kbuild
@@ -0,0 +1,6 @@ 
+# UAPI Header export list
+
+generated-y += syscall_defs.h
+
+# no generated-y since we need special user headers handling
+# see arch/um/script/headers_install.py
diff --git a/arch/um/nommu/include/uapi/asm/bitsperlong.h b/arch/um/nommu/include/uapi/asm/bitsperlong.h
new file mode 100644
index 000000000000..852566ac2e52
--- /dev/null
+++ b/arch/um/nommu/include/uapi/asm/bitsperlong.h
@@ -0,0 +1,11 @@ 
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __UM_NOMMU_UAPI_BITSPERLONG_H
+#define __UM_NOMMU_UAPI_BITSPERLONG_H
+
+#ifdef CONFIG_64BIT
+#define __BITS_PER_LONG 64
+#else
+#define __BITS_PER_LONG 32
+#endif
+
+#endif
diff --git a/arch/um/nommu/include/uapi/asm/byteorder.h b/arch/um/nommu/include/uapi/asm/byteorder.h
new file mode 100644
index 000000000000..e7ad11a751cf
--- /dev/null
+++ b/arch/um/nommu/include/uapi/asm/byteorder.h
@@ -0,0 +1,11 @@ 
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __UM_NOMMU_UAPI_BYTEORDER_H
+#define __UM_NOMMU_UAPI_BYTEORDER_H
+
+#if defined(CONFIG_BIG_ENDIAN)
+#include <linux/byteorder/big_endian.h>
+#else
+#include <linux/byteorder/little_endian.h>
+#endif
+
+#endif
diff --git a/arch/um/nommu/include/uapi/asm/sigcontext.h b/arch/um/nommu/include/uapi/asm/sigcontext.h
new file mode 100644
index 000000000000..b934ae7f5550
--- /dev/null
+++ b/arch/um/nommu/include/uapi/asm/sigcontext.h
@@ -0,0 +1,12 @@ 
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __UM_NOMMU_UAPI_SIGCONTEXT_H
+#define __UM_NOMMU_UAPI_SIGCONTEXT_H
+
+#include <asm/ptrace-generic.h>
+
+struct sigcontext {
+	struct pt_regs regs;
+	unsigned long oldmask;
+};
+
+#endif
diff --git a/arch/um/nommu/um/delay.c b/arch/um/nommu/um/delay.c
new file mode 100644
index 000000000000..58a366d9b5f0
--- /dev/null
+++ b/arch/um/nommu/um/delay.c
@@ -0,0 +1,31 @@ 
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/jiffies.h>
+#include <linux/delay.h>
+#include <os.h>
+
+void __ndelay(unsigned long nsecs)
+{
+	long long start = os_nsecs();
+
+	while (os_nsecs() < start + nsecs)
+		;
+}
+
+void __udelay(unsigned long usecs)
+{
+	__ndelay(usecs * NSEC_PER_USEC);
+}
+
+void __const_udelay(unsigned long xloops)
+{
+	__udelay(xloops / 0x10c7ul);
+}
+
+void __delay(unsigned long loops)
+{
+	__ndelay(loops / 5);
+}
+
+void calibrate_delay(void)
+{
+}
diff --git a/arch/um/nommu/um/shared/sysdep/archsetjmp.h b/arch/um/nommu/um/shared/sysdep/archsetjmp.h
new file mode 100644
index 000000000000..4a5c10d7521b
--- /dev/null
+++ b/arch/um/nommu/um/shared/sysdep/archsetjmp.h
@@ -0,0 +1,13 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARCH_UM_SETJMP_H
+#define __ARCH_UM_SETJMP_H
+
+struct __jmp_buf {
+	unsigned long __dummy;
+};
+#define JB_IP __dummy
+#define JB_SP __dummy
+
+typedef struct __jmp_buf jmp_buf[1];
+
+#endif /* __ARCH_UM_SETJMP_H */
diff --git a/arch/um/nommu/um/shared/sysdep/faultinfo.h b/arch/um/nommu/um/shared/sysdep/faultinfo.h
new file mode 100644
index 000000000000..49210742212d
--- /dev/null
+++ b/arch/um/nommu/um/shared/sysdep/faultinfo.h
@@ -0,0 +1,8 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARCH_UM_FAULTINFO_H
+#define __ARCH_UM_FAULTINFO_H
+
+struct faultinfo {
+};
+
+#endif /* __ARCH_UM_FAULTINFO_H */
diff --git a/arch/um/nommu/um/shared/sysdep/kernel-offsets.h b/arch/um/nommu/um/shared/sysdep/kernel-offsets.h
new file mode 100644
index 000000000000..a004bffb7b8d
--- /dev/null
+++ b/arch/um/nommu/um/shared/sysdep/kernel-offsets.h
@@ -0,0 +1,12 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/stddef.h>
+#include <linux/sched.h>
+#include <linux/elf.h>
+#include <linux/crypto.h>
+#include <linux/kbuild.h>
+#include <asm/mman.h>
+
+void foo(void)
+{
+#include <common-offsets.h>
+}
diff --git a/arch/um/nommu/um/shared/sysdep/mcontext.h b/arch/um/nommu/um/shared/sysdep/mcontext.h
new file mode 100644
index 000000000000..b734012a74da
--- /dev/null
+++ b/arch/um/nommu/um/shared/sysdep/mcontext.h
@@ -0,0 +1,9 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARCH_UM_MCONTEXT_H
+#define __ARCH_UM_MCONTEXT_H
+
+extern void get_regs_from_mc(struct uml_pt_regs *regs, mcontext_t *mc);
+
+#define GET_FAULTINFO_FROM_MC(fi, mc) (fi = fi)
+
+#endif /* __ARCH_UM_MCONTEXT_H */
diff --git a/arch/um/nommu/um/shared/sysdep/ptrace.h b/arch/um/nommu/um/shared/sysdep/ptrace.h
new file mode 100644
index 000000000000..bfdfb520a21d
--- /dev/null
+++ b/arch/um/nommu/um/shared/sysdep/ptrace.h
@@ -0,0 +1,42 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARCH_UM_PTRACE_H
+#define __ARCH_UM_PTRACE_H
+
+#include <generated/user_constants.h>
+#include <linux/errno.h>
+
+struct task_struct;
+
+#define UPT_SYSCALL_NR(r) ((r)->syscall)
+#define UPT_RESTART_SYSCALL(r) ((r)->syscall--) /* XXX */
+
+#define UPT_SP(r) 0
+#define UPT_IP(r) 0
+#define EMPTY_UML_PT_REGS { }
+
+#define MAX_REG_OFFSET (UM_FRAME_SIZE)
+#define MAX_REG_NR ((MAX_REG_OFFSET) / sizeof(unsigned long))
+
+/* unused */
+struct uml_pt_regs {
+	unsigned long gp[1];
+	unsigned long fp[1];
+	long faultinfo;
+	long syscall;
+	int is_user;
+};
+
+extern void arch_init_registers(int pid);
+
+static inline long arch_ptrace(struct task_struct *child,
+			       long request, unsigned long addr,
+			       unsigned long data)
+{
+	return -EINVAL;
+}
+
+static inline void ptrace_disable(struct task_struct *child) {}
+static inline void user_enable_single_step(struct task_struct *child) {}
+static inline void user_disable_single_step(struct task_struct *child) {}
+
+#endif /* __ARCH_UM_PTRACE_H */
diff --git a/arch/um/nommu/um/shared/sysdep/ptrace_user.h b/arch/um/nommu/um/shared/sysdep/ptrace_user.h
new file mode 100644
index 000000000000..86d5cb20fb9f
--- /dev/null
+++ b/arch/um/nommu/um/shared/sysdep/ptrace_user.h
@@ -0,0 +1,7 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARCH_UM_PTRACE_USER_H
+#define __ARCH_UM_PTRACE_USER_H
+
+#define FP_SIZE 1
+
+#endif
diff --git a/arch/um/nommu/um/unimplemented.c b/arch/um/nommu/um/unimplemented.c
new file mode 100644
index 000000000000..fe33e02e39e5
--- /dev/null
+++ b/arch/um/nommu/um/unimplemented.c
@@ -0,0 +1,70 @@ 
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/signal.h>
+#include <sysdep/ptrace.h>
+#include <asm/ptrace.h>
+
+/* physmem.c  */
+unsigned long high_physmem;
+
+/* x86/um/setjmp*.S  */
+void kernel_longjmp(void)
+{}
+void kernel_setjmp(void)
+{}
+
+/* trap.c */
+void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
+{}
+void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
+{}
+void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
+{}
+void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
+{}
+
+/* tlb.c */
+void flush_tlb_kernel_vm(void)
+{}
+void force_flush_all(void)
+{}
+
+/* skas/process.c */
+void halt_skas(void)
+{}
+int is_skas_winch(int pid, int fd, void *data)
+{
+	return 0;
+}
+void reboot_skas(void)
+{}
+
+int __init start_uml(void)
+{
+	return 0;
+}
+
+/* exec.c */
+void flush_thread(void)
+{}
+
+/* x86/ptrace_64.c */
+int is_syscall(unsigned long addr)
+{
+	return 0;
+}
+
+
+/* x86/sysrq.c */
+void show_regs(struct pt_regs *regs)
+{}
+
+/* x86/signal.c */
+int setup_signal_stack_si(unsigned long stack_top, struct ksignal *ksig,
+			  struct pt_regs *regs, sigset_t *mask)
+{
+	return 0;
+}
+
+/* x86/bugs.c */
+void arch_check_bugs(void)
+{}
diff --git a/arch/um/nommu/um/user_constants.h b/arch/um/nommu/um/user_constants.h
new file mode 100644
index 000000000000..2245d3d24120
--- /dev/null
+++ b/arch/um/nommu/um/user_constants.h
@@ -0,0 +1,13 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __UM_NOMMU_USER_CONSTANTS_H
+#define __UM_NOMMU_USER_CONSTANTS_H
+
+/* XXX: put dummy values */
+#define UM_FRAME_SIZE 4
+#define HOST_FP_SIZE 1
+#define HOST_IP 1
+#define HOST_SP 2
+#define HOST_BP 3
+#define UM_NR_CPUS 1
+
+#endif