Re: [RFC v5 01/21] um: split build in kernel and host parts

[Anton Ivanov <anton.ivanov@cambridgegreys.com>]

On 02/07/2020 15:06, Hajime Tazaki wrote:
> From: Octavian Purdila <tavi@cs.pub.ro>
> 
> This patch splits the UML build in two parts: a kernel part that
> generates a relocatable object (linux.o) and a host build part that
> links the relocatable object into an executable.
> 
> This allows us to simplify the linker script since we can now remove
> the host bits (e.g. .rel sections). It also gives us greater
> flexibility since it will be much easier to support other
> architectures and OSes if we use the standard linker script.
> 
> The host build part has been implemented in tools/um so that we can
> reuse the available host build infrastructure.
> 
> The patch also changes the UML build invocation, if before
> 
>   $ make ARCH=um defconfig
>   $ make ARCH=um
> 
> was generating the executable now this only generates the relocatable
> object.
> 
> To fully build UML use:
> 
>   $ make -C tools/um
> 
> which will generate tools/lkl/linux as the UML executable. To
> statically compiled UML use:
> 
>   $ make -C tools/lkl UML_STATIC=y
> 
> Signed-off-by: Octavian Purdila <tavi@cs.pub.ro>
> Signed-off-by: Hajime Tazaki <thehajime@gmail.com>
> ---
>   arch/um/Kconfig                  |  12 +--
>   arch/um/Makefile                 |  14 ++-
>   arch/um/include/asm/common.lds.S |  99 ------------------
>   arch/um/kernel/dyn.lds.S         | 171 -------------------------------
>   arch/um/kernel/uml.lds.S         | 115 ---------------------
>   arch/um/kernel/vmlinux.lds.S     |  91 ++++++++++++++--
>   scripts/link-vmlinux.sh          |  42 +++-----
>   tools/um/Makefile                |  72 +++++++++++++
>   tools/um/Targets                 |   4 +
>   tools/um/uml/Build               |   0
>   10 files changed, 184 insertions(+), 436 deletions(-)
>   delete mode 100644 arch/um/include/asm/common.lds.S
>   delete mode 100644 arch/um/kernel/dyn.lds.S
>   delete mode 100644 arch/um/kernel/uml.lds.S
>   create mode 100644 tools/um/Makefile
>   create mode 100644 tools/um/Targets
>   create mode 100644 tools/um/uml/Build
> 
> diff --git a/arch/um/Kconfig b/arch/um/Kconfig
> index 96ab7026b037..a0a9fd3ab96c 100644
> --- a/arch/um/Kconfig
> +++ b/arch/um/Kconfig
> @@ -20,6 +20,7 @@ config UML
>   	select GENERIC_CLOCKEVENTS
>   	select HAVE_GCC_PLUGINS
>   	select TTY # Needed for line.c
> +	select MODULE_REL_CRCS if MODVERSIONS
>   
>   config MMU
>   	bool
> @@ -79,17 +80,6 @@ config STATIC_LINK
>   	  NOTE: This option is incompatible with some networking features which
>   	  depend on features that require being dynamically loaded (like NSS).
>   
> -config LD_SCRIPT_STATIC
> -	bool
> -	default y
> -	depends on STATIC_LINK
> -
> -config LD_SCRIPT_DYN
> -	bool
> -	default y
> -	depends on !LD_SCRIPT_STATIC
> -	select MODULE_REL_CRCS if MODVERSIONS
> -
>   config HOSTFS
>   	tristate "Host filesystem"
>   	help
> diff --git a/arch/um/Makefile b/arch/um/Makefile
> index 275f5ffdf6f0..c952ddefcc1c 100644
> --- a/arch/um/Makefile
> +++ b/arch/um/Makefile
> @@ -95,14 +95,20 @@ KBUILD_CPPFLAGS += -I$(srctree)/$(HOST_DIR)/include \
>   KERNEL_DEFINES = $(strip -Derrno=kernel_errno -Dsigprocmask=kernel_sigprocmask \
>   			 -Dmktime=kernel_mktime $(ARCH_KERNEL_DEFINES))
>   KBUILD_CFLAGS += $(KERNEL_DEFINES)
> +LDFLAGS_vmlinux += -r
>   
> -PHONY += linux
> +PHONY += linux.o
>   
> -all: linux
> +all: linux.o
>   
> -linux: vmlinux
> +linux.o: vmlinux
>   	@echo '  LINK $@'
> -	$(Q)ln -f $< $@
> +	$(Q)$(OBJCOPY) -R .eh_frame $< $@
> +
> +install: linux.o
> +	@echo "  INSTALL $(INSTALL_PATH)/lib/$<"
> +	@mkdir -p $(INSTALL_PATH)/lib/
> +	@cp $< $(INSTALL_PATH)/lib/
>   
>   define archhelp
>     echo '* linux		- Binary kernel image (./linux) - for backward'
> diff --git a/arch/um/include/asm/common.lds.S b/arch/um/include/asm/common.lds.S
> deleted file mode 100644
> index eca6c452a41b..000000000000
> --- a/arch/um/include/asm/common.lds.S
> +++ /dev/null
> @@ -1,99 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0 */
> -#include <asm-generic/vmlinux.lds.h>
> -
> -  .fini      : { *(.fini)    } =0x9090
> -  _etext = .;
> -  PROVIDE (etext = .);
> -
> -  . = ALIGN(4096);
> -  _sdata = .;
> -  PROVIDE (sdata = .);
> -
> -  RO_DATA(4096)
> -
> -  .unprotected : { *(.unprotected) }
> -  . = ALIGN(4096);
> -  PROVIDE (_unprotected_end = .);
> -
> -  . = ALIGN(4096);
> -  EXCEPTION_TABLE(0)
> -
> -  BUG_TABLE
> -
> -  .uml.setup.init : {
> -	__uml_setup_start = .;
> -	*(.uml.setup.init)
> -	__uml_setup_end = .;
> -  }
> -	
> -  .uml.help.init : {
> -	__uml_help_start = .;
> -	*(.uml.help.init)
> -	__uml_help_end = .;
> -  }
> -	
> -  .uml.postsetup.init : {
> -	__uml_postsetup_start = .;
> -	*(.uml.postsetup.init)
> -	__uml_postsetup_end = .;
> -  }
> -	
> -  .init.setup : {
> -	INIT_SETUP(0)
> -  }
> -
> -  PERCPU_SECTION(32)
> -	
> -  .initcall.init : {
> -	INIT_CALLS
> -  }
> -
> -  .con_initcall.init : {
> -	CON_INITCALL
> -  }
> -
> -  .exitcall : {
> -	__exitcall_begin = .;
> -	*(.exitcall.exit)
> -	__exitcall_end = .;
> -  }
> -
> -  .uml.exitcall : {
> -	__uml_exitcall_begin = .;
> -	*(.uml.exitcall.exit)
> -	__uml_exitcall_end = .;
> -  }
> -
> -  . = ALIGN(4);
> -  .altinstructions : {
> -	__alt_instructions = .;
> -	*(.altinstructions)
> -	__alt_instructions_end = .;
> -  }
> -  .altinstr_replacement : { *(.altinstr_replacement) }
> -  /* .exit.text is discard at runtime, not link time, to deal with references
> -     from .altinstructions and .eh_frame */
> -  .exit.text : { EXIT_TEXT }
> -  .exit.data : { *(.exit.data) }
> -
> -  .preinit_array : {
> -	__preinit_array_start = .;
> -	*(.preinit_array)
> -	__preinit_array_end = .;
> -  }
> -  .init_array : {
> -	__init_array_start = .;
> -	*(.init_array)
> -	__init_array_end = .;
> -  }
> -  .fini_array : {
> -	__fini_array_start = .;
> -	*(.fini_array)
> -	__fini_array_end = .;
> -  }
> -
> -   . = ALIGN(4096);
> -  .init.ramfs : {
> -	INIT_RAM_FS
> -  }
> -
> diff --git a/arch/um/kernel/dyn.lds.S b/arch/um/kernel/dyn.lds.S
> deleted file mode 100644
> index f5001481010c..000000000000
> --- a/arch/um/kernel/dyn.lds.S
> +++ /dev/null
> @@ -1,171 +0,0 @@
> -#include <asm/vmlinux.lds.h>
> -#include <asm/page.h>
> -
> -OUTPUT_FORMAT(ELF_FORMAT)
> -OUTPUT_ARCH(ELF_ARCH)
> -ENTRY(_start)
> -jiffies = jiffies_64;
> -
> -SECTIONS
> -{
> -  PROVIDE (__executable_start = START);
> -  . = START + SIZEOF_HEADERS;
> -  .interp         : { *(.interp) }
> -  __binary_start = .;
> -  . = ALIGN(4096);		/* Init code and data */
> -  _text = .;
> -  INIT_TEXT_SECTION(PAGE_SIZE)
> -
> -  . = ALIGN(PAGE_SIZE);
> -
> -  /* Read-only sections, merged into text segment: */
> -  .hash           : { *(.hash) }
> -  .gnu.hash       : { *(.gnu.hash) }
> -  .dynsym         : { *(.dynsym) }
> -  .dynstr         : { *(.dynstr) }
> -  .gnu.version    : { *(.gnu.version) }
> -  .gnu.version_d  : { *(.gnu.version_d) }
> -  .gnu.version_r  : { *(.gnu.version_r) }
> -  .rel.init       : { *(.rel.init) }
> -  .rela.init      : { *(.rela.init) }
> -  .rel.text       : { *(.rel.text .rel.text.* .rel.gnu.linkonce.t.*) }
> -  .rela.text      : { *(.rela.text .rela.text.* .rela.gnu.linkonce.t.*) }
> -  .rel.fini       : { *(.rel.fini) }
> -  .rela.fini      : { *(.rela.fini) }
> -  .rel.rodata     : { *(.rel.rodata .rel.rodata.* .rel.gnu.linkonce.r.*) }
> -  .rela.rodata    : { *(.rela.rodata .rela.rodata.* .rela.gnu.linkonce.r.*) }
> -  .rel.data       : { *(.rel.data .rel.data.* .rel.gnu.linkonce.d.*) }
> -  .rela.data      : { *(.rela.data .rela.data.* .rela.gnu.linkonce.d.*) }
> -  .rel.tdata	  : { *(.rel.tdata .rel.tdata.* .rel.gnu.linkonce.td.*) }
> -  .rela.tdata	  : { *(.rela.tdata .rela.tdata.* .rela.gnu.linkonce.td.*) }
> -  .rel.tbss	  : { *(.rel.tbss .rel.tbss.* .rel.gnu.linkonce.tb.*) }
> -  .rela.tbss	  : { *(.rela.tbss .rela.tbss.* .rela.gnu.linkonce.tb.*) }
> -  .rel.ctors      : { *(.rel.ctors) }
> -  .rela.ctors     : { *(.rela.ctors) }
> -  .rel.dtors      : { *(.rel.dtors) }
> -  .rela.dtors     : { *(.rela.dtors) }
> -  .rel.got        : { *(.rel.got) }
> -  .rela.got       : { *(.rela.got) }
> -  .rel.bss        : { *(.rel.bss .rel.bss.* .rel.gnu.linkonce.b.*) }
> -  .rela.bss       : { *(.rela.bss .rela.bss.* .rela.gnu.linkonce.b.*) }
> -  .rel.plt : {
> -	*(.rel.plt)
> -	PROVIDE_HIDDEN(__rel_iplt_start = .);
> -	*(.rel.iplt)
> -	PROVIDE_HIDDEN(__rel_iplt_end = .);
> -  }
> -  .rela.plt : {
> -	*(.rela.plt)
> -	PROVIDE_HIDDEN(__rela_iplt_start = .);
> -	*(.rela.iplt)
> -	PROVIDE_HIDDEN(__rela_iplt_end = .);
> -  }
> -  .init           : {
> -    KEEP (*(.init))
> -  } =0x90909090
> -  .plt            : { *(.plt) }
> -  .text           : {
> -    _stext = .;
> -    TEXT_TEXT
> -    SCHED_TEXT
> -    CPUIDLE_TEXT
> -    LOCK_TEXT
> -    IRQENTRY_TEXT
> -    SOFTIRQENTRY_TEXT
> -    *(.fixup)
> -    *(.stub .text.* .gnu.linkonce.t.*)
> -    /* .gnu.warning sections are handled specially by elf32.em.  */
> -    *(.gnu.warning)
> -
> -    . = ALIGN(PAGE_SIZE);
> -  } =0x90909090
> -  . = ALIGN(PAGE_SIZE);
> -  .syscall_stub : {
> -	__syscall_stub_start = .;
> -	*(.__syscall_stub*)
> -	__syscall_stub_end = .;
> -  }
> -  .fini           : {
> -    KEEP (*(.fini))
> -  } =0x90909090
> -
> -  .kstrtab : { *(.kstrtab) }
> -
> -  #include <asm/common.lds.S>
> -
> -  __init_begin = .;
> -  init.data : { INIT_DATA }
> -  __init_end = .;
> -
> -  /* Ensure the __preinit_array_start label is properly aligned.  We
> -     could instead move the label definition inside the section, but
> -     the linker would then create the section even if it turns out to
> -     be empty, which isn't pretty.  */
> -  . = ALIGN(32 / 8);
> -  .preinit_array     : { *(.preinit_array) }
> -  .init_array     : { *(.init_array) }
> -  .fini_array     : { *(.fini_array) }
> -  .data           : {
> -    INIT_TASK_DATA(KERNEL_STACK_SIZE)
> -    . = ALIGN(KERNEL_STACK_SIZE);
> -    *(.data..init_irqstack)
> -    DATA_DATA
> -    *(.data.* .gnu.linkonce.d.*)
> -    SORT(CONSTRUCTORS)
> -  }
> -  .data1          : { *(.data1) }
> -  .tdata	  : { *(.tdata .tdata.* .gnu.linkonce.td.*) }
> -  .tbss		  : { *(.tbss .tbss.* .gnu.linkonce.tb.*) *(.tcommon) }
> -  .eh_frame       : { KEEP (*(.eh_frame)) }
> -  .gcc_except_table   : { *(.gcc_except_table) }
> -  .dynamic        : { *(.dynamic) }
> -  .ctors          : {
> -    /* gcc uses crtbegin.o to find the start of
> -       the constructors, so we make sure it is
> -       first.  Because this is a wildcard, it
> -       doesn't matter if the user does not
> -       actually link against crtbegin.o; the
> -       linker won't look for a file to match a
> -       wildcard.  The wildcard also means that it
> -       doesn't matter which directory crtbegin.o
> -       is in.  */
> -    KEEP (*crtbegin.o(.ctors))
> -    /* We don't want to include the .ctor section from
> -       from the crtend.o file until after the sorted ctors.
> -       The .ctor section from the crtend file contains the
> -       end of ctors marker and it must be last */
> -    KEEP (*(EXCLUDE_FILE (*crtend.o ) .ctors))
> -    KEEP (*(SORT(.ctors.*)))
> -    KEEP (*(.ctors))
> -  }
> -  .dtors          : {
> -    KEEP (*crtbegin.o(.dtors))
> -    KEEP (*(EXCLUDE_FILE (*crtend.o ) .dtors))
> -    KEEP (*(SORT(.dtors.*)))
> -    KEEP (*(.dtors))
> -  }
> -  .jcr            : { KEEP (*(.jcr)) }
> -  .got            : { *(.got.plt) *(.got) }
> -  _edata = .;
> -  PROVIDE (edata = .);
> -  .bss            : {
> -   __bss_start = .;
> -   *(.dynbss)
> -   *(.bss .bss.* .gnu.linkonce.b.*)
> -   *(COMMON)
> -   /* Align here to ensure that the .bss section occupies space up to
> -      _end.  Align after .bss to ensure correct alignment even if the
> -      .bss section disappears because there are no input sections.  */
> -   . = ALIGN(32 / 8);
> -  . = ALIGN(32 / 8);
> -  }
> -   __bss_stop = .;
> -  _end = .;
> -  PROVIDE (end = .);
> -
> -  STABS_DEBUG
> -
> -  DWARF_DEBUG
> -
> -  DISCARDS
> -}
> diff --git a/arch/um/kernel/uml.lds.S b/arch/um/kernel/uml.lds.S
> deleted file mode 100644
> index 3b6dab3d4501..000000000000
> --- a/arch/um/kernel/uml.lds.S
> +++ /dev/null
> @@ -1,115 +0,0 @@
> -/* SPDX-License-Identifier: GPL-2.0 */
> -#include <asm/vmlinux.lds.h>
> -#include <asm/page.h>
> -
> -OUTPUT_FORMAT(ELF_FORMAT)
> -OUTPUT_ARCH(ELF_ARCH)
> -ENTRY(_start)
> -jiffies = jiffies_64;
> -
> -SECTIONS
> -{
> -  /* This must contain the right address - not quite the default ELF one.*/
> -  PROVIDE (__executable_start = START);
> -  /* Static binaries stick stuff here, like the sigreturn trampoline,
> -   * invisibly to objdump.  So, just make __binary_start equal to the very
> -   * beginning of the executable, and if there are unmapped pages after this,
> -   * they are forever unusable.
> -   */
> -  __binary_start = START;
> -
> -  . = START + SIZEOF_HEADERS;
> -  . = ALIGN(PAGE_SIZE);
> -
> -  _text = .;
> -  INIT_TEXT_SECTION(0)
> -
> -  .text      :
> -  {
> -    _stext = .;
> -    TEXT_TEXT
> -    SCHED_TEXT
> -    CPUIDLE_TEXT
> -    LOCK_TEXT
> -    IRQENTRY_TEXT
> -    SOFTIRQENTRY_TEXT
> -    *(.fixup)
> -    /* .gnu.warning sections are handled specially by elf32.em.  */
> -    *(.gnu.warning)
> -    *(.gnu.linkonce.t*)
> -  }
> -
> -  . = ALIGN(PAGE_SIZE);
> -  .syscall_stub : {
> -	__syscall_stub_start = .;
> -	*(.__syscall_stub*)
> -	__syscall_stub_end = .;
> -  }
> -
> -  /*
> -   * These are needed even in a static link, even if they wind up being empty.
> -   * Newer glibc needs these __rel{,a}_iplt_{start,end} symbols.
> -   */
> -  .rel.plt : {
> -	*(.rel.plt)
> -	PROVIDE_HIDDEN(__rel_iplt_start = .);
> -	*(.rel.iplt)
> -	PROVIDE_HIDDEN(__rel_iplt_end = .);
> -  }
> -  .rela.plt : {
> -	*(.rela.plt)
> -	PROVIDE_HIDDEN(__rela_iplt_start = .);
> -	*(.rela.iplt)
> -	PROVIDE_HIDDEN(__rela_iplt_end = .);
> -  }
> -
> -  #include <asm/common.lds.S>
> -
> -  __init_begin = .;
> -  init.data : { INIT_DATA }
> -  __init_end = .;
> -
> -  .data    :
> -  {
> -    INIT_TASK_DATA(KERNEL_STACK_SIZE)
> -    . = ALIGN(KERNEL_STACK_SIZE);
> -    *(.data..init_irqstack)
> -    DATA_DATA
> -    *(.gnu.linkonce.d*)
> -    CONSTRUCTORS
> -  }
> -  .data1   : { *(.data1) }
> -  .ctors         :
> -  {
> -    *(.ctors)
> -  }
> -  .dtors         :
> -  {
> -    *(.dtors)
> -  }
> -
> -  .got           : { *(.got.plt) *(.got) }
> -  .dynamic       : { *(.dynamic) }
> -  .tdata	  : { *(.tdata .tdata.* .gnu.linkonce.td.*) }
> -  .tbss		  : { *(.tbss .tbss.* .gnu.linkonce.tb.*) *(.tcommon) }
> -  /* We want the small data sections together, so single-instruction offsets
> -     can access them all, and initialized data all before uninitialized, so
> -     we can shorten the on-disk segment size.  */
> -  .sdata     : { *(.sdata) }
> -  _edata  =  .;
> -  PROVIDE (edata = .);
> -  . = ALIGN(PAGE_SIZE);
> -  __bss_start = .;
> -  PROVIDE(_bss_start = .);
> -  SBSS(0)
> -  BSS(0)
> -   __bss_stop = .;
> -  _end = .;
> -  PROVIDE (end = .);
> -
> -  STABS_DEBUG
> -
> -  DWARF_DEBUG
> -
> -  DISCARDS
> -}
> diff --git a/arch/um/kernel/vmlinux.lds.S b/arch/um/kernel/vmlinux.lds.S
> index 16e49bfa2b42..aaedd66772fa 100644
> --- a/arch/um/kernel/vmlinux.lds.S
> +++ b/arch/um/kernel/vmlinux.lds.S
> @@ -1,8 +1,87 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#include <asm/vmlinux.lds.h>
> +#include <asm/thread_info.h>
> +#include <asm/page.h>
> +#include <asm/thread_info.h>
> +#include <asm/cache.h>
> +#include <linux/export.h>
>   
> -KERNEL_STACK_SIZE = 4096 * (1 << CONFIG_KERNEL_STACK_ORDER);
> +OUTPUT_FORMAT(ELF_FORMAT)
> +jiffies = jiffies_64;
>   
> -#ifdef CONFIG_LD_SCRIPT_STATIC
> -#include "uml.lds.S"
> -#else
> -#include "dyn.lds.S"
> -#endif
> +
> +SECTIONS
> +{
> +	__init_begin = . ;
> +	HEAD_TEXT_SECTION
> +	INIT_TEXT_SECTION(PAGE_SIZE)
> +	INIT_DATA_SECTION(16)
> +	PERCPU_SECTION(L1_CACHE_BYTES)
> +	__init_end = . ;
> +
> +	_stext = . ;
> +	_text = . ;
> +	.text : ALIGN(THREAD_SIZE)
> +	{
> +		__binary_start = . ;
> +		TEXT_TEXT
> +		SCHED_TEXT
> +		LOCK_TEXT
> +		CPUIDLE_TEXT
> +		IRQENTRY_TEXT
> +		SOFTIRQENTRY_TEXT
> +	}
> +	_etext = . ;
> +
> +	.syscall_stub : ALIGN(PAGE_SIZE)
> +	{
> +		__syscall_stub_start = .;
> +		*(.__syscall_stub*)
> +		__syscall_stub_end = .;
> +	}
> +
> +	_sdata = . ;
> +	RO_DATA(PAGE_SIZE)
> +	RW_DATA(L1_CACHE_BYTES, PAGE_SIZE, THREAD_SIZE)
> +	.data : ALIGN(THREAD_SIZE)  { }
> +
> +	EXCEPTION_TABLE(16)
> +
> +	.uml.init_irqstack : ALIGN(THREAD_SIZE) {
> +		*(.data..init_irqstack)
> +	}
> +
> +	.uml.setup.init : ALIGN(8) {
> +		__uml_setup_start = .;
> +		*(.uml.setup.init)
> +		__uml_setup_end = .;
> +	}
> +
> +	.uml.help.init : ALIGN(8)  {
> +		__uml_help_start = .;
> +		*(.uml.help.init)
> +		__uml_help_end = .;
> +	}
> +
> +	.uml.postsetup.init : ALIGN(8) {
> +		__uml_postsetup_start = .;
> +		*(.uml.postsetup.init)
> +		__uml_postsetup_end = .;
> +	}
> +
> +	.uml.exitcall : ALIGN(8) {
> +		__uml_exitcall_begin = .;
> +		*(.uml.exitcall.exit)
> +		__uml_exitcall_end = .;
> +	}
> +	_edata = . ;
> +
> +	BSS_SECTION(0, 0, 0)
> +	_end = . ;
> +
> +	STABS_DEBUG
> +
> +	DWARF_DEBUG
> +
> +	DISCARDS
> +}
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index d09ab4afbda4..0bbb626ace81 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -75,36 +75,18 @@ vmlinux_link()
>   		strip_debug=-Wl,--strip-debug
>   	fi
>   
> -	if [ "${SRCARCH}" != "um" ]; then
> -		objects="--whole-archive			\
> -			${KBUILD_VMLINUX_OBJS}			\
> -			--no-whole-archive			\
> -			--start-group				\
> -			${KBUILD_VMLINUX_LIBS}			\
> -			--end-group				\
> -			${@}"
> -
> -		${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}	\
> -			${strip_debug#-Wl,}			\
> -			-o ${output}				\
> -			-T ${lds} ${objects}
> -	else
> -		objects="-Wl,--whole-archive			\
> -			${KBUILD_VMLINUX_OBJS}			\
> -			-Wl,--no-whole-archive			\
> -			-Wl,--start-group			\
> -			${KBUILD_VMLINUX_LIBS}			\
> -			-Wl,--end-group				\
> -			${@}"
> -
> -		${CC} ${CFLAGS_vmlinux}				\
> -			${strip_debug}				\
> -			-o ${output}				\
> -			-Wl,-T,${lds}				\
> -			${objects}				\
> -			-lutil -lrt -lpthread
> -		rm -f linux
> -	fi
> +	objects="--whole-archive			\
> +		${KBUILD_VMLINUX_OBJS}			\
> +		--no-whole-archive			\
> +		--start-group				\
> +		${KBUILD_VMLINUX_LIBS}			\
> +		--end-group				\
> +		${@}"
> +
> +	${LD} ${KBUILD_LDFLAGS} ${LDFLAGS_vmlinux}	\
> +		${strip_debug#-Wl,}			\
> +		-o ${output}				\
> +		-T ${lds} ${objects}
>   }
>   
>   # generate .BTF typeinfo from DWARF debuginfo
> diff --git a/tools/um/Makefile b/tools/um/Makefile
> new file mode 100644
> index 000000000000..a63466ef7ef5
> --- /dev/null
> +++ b/tools/um/Makefile
> @@ -0,0 +1,72 @@
> +# Do not use make's built-in rules
> +# (this improves performance and avoids hard-to-debug behaviour);
> +# also do not print "Entering directory..." messages from make
> +.SUFFIXES:
> +MAKEFLAGS += -r --no-print-directory
> +
> +KCONFIG?=defconfig
> +
> +ifneq ($(silent),1)
> +  ifneq ($(V),1)
> +	QUIET_AUTOCONF       = @echo '  AUTOCONF '$@;
> +	Q = @
> +  endif
> +endif
> +
> +PREFIX   := /usr
> +
> +ifeq (,$(srctree))
> +  srctree := $(patsubst %/,%,$(dir $(shell pwd)))
> +  srctree := $(patsubst %/,%,$(dir $(srctree)))
> +endif
> +export srctree
> +
> +-include ../scripts/Makefile.include
> +
> +# OUTPUT fixup should be *after* include ../scripts/Makefile.include
> +ifneq ($(OUTPUT),)
> +  OUTPUT := $(OUTPUT)/tools/um/
> +else
> +  OUTPUT := $(CURDIR)/
> +endif
> +export OUTPUT
> +export objtree := $(OUTPUT)/../..
> +
> +
> +all:
> +
> +export CFLAGS += -I$(OUTPUT)/include -Iinclude -Wall -g -O2 -Wextra -fPIC \
> +	 -Wno-unused-parameter \
> +	 -Wno-missing-field-initializers -fno-strict-aliasing
> +
> +-include Targets
> +
> +TARGETS := $(progs-y:%=$(OUTPUT)%)
> +TARGETS += $(libs-y:%=$(OUTPUT)%)
> +all: $(TARGETS)
> +
> +# rule to build linux.o
> +$(OUTPUT)lib/linux.o:
> +	$(Q)CFLAGS= $(MAKE) -C ../.. ARCH=um $(KOPT) $(KCONFIG)
> +	$(Q)CFLAGS= $(MAKE) -C ../.. ARCH=um $(KOPT) install INSTALL_PATH=$(OUTPUT)
> +
> +$(OUTPUT)liblinux.a: $(OUTPUT)lib/linux.o $(OUTPUT)uml/liblinux-in.o
> +	$(QUIET_AR)$(AR) -rc $@ $^
> +
> +# rule to link programs
> +$(OUTPUT)%: $(OUTPUT)%-in.o $(OUTPUT)liblinux.a
> +	$(QUIET_LINK)$(CC) $(LDFLAGS) $(LDFLAGS_$(notdir $*)-y) -o $@ $^ $(LDLIBS) $(LDLIBS_$(notdir $*)-y)
> +
> +$(OUTPUT)%-in.o: FORCE
> +	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=$(patsubst %/,%,$(dir $*)) obj=$(notdir $*)
> +
> +clean:
> +	$(call QUIET_CLEAN, objects)find $(OUTPUT) -name '*.o' -delete -o -name '\.*.cmd'\
> +	 -delete -o -name '\.*.d' -delete
> +	$(call QUIET_CLEAN, liblinux.a)$(RM) $(OUTPUT)/liblinux.a
> +	$(call QUIET_CLEAN, $(TARGETS))$(RM) $(TARGETS)
> +
> +FORCE: ;
> +.PHONY: all clean FORCE
> +.IGNORE: clean
> +.NOTPARALLEL : lib/linux.o
> diff --git a/tools/um/Targets b/tools/um/Targets
> new file mode 100644
> index 000000000000..a4711f1ef422
> --- /dev/null
> +++ b/tools/um/Targets
> @@ -0,0 +1,4 @@
> +progs-y += uml/linux
> +LDLIBS_linux-y := -lrt -lpthread -lutil
> +LDFLAGS_linux-y := -no-pie -Wl,--wrap,malloc -Wl,--wrap,free -Wl,--wrap,calloc
> +LDFLAGS_linux-$(UML_STATIC) += -static
> diff --git a/tools/um/uml/Build b/tools/um/uml/Build
> new file mode 100644
> index 000000000000..e69de29bb2d1
> 

Hi Hajime, hi Octavian,

I am going to have a bit more time to look at UML now. Can you rebase/update the patch versus the latest kernel so I can look at it.

It does not apply at present.

Thanks in advance,

-- 
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/