[uclibc-ng-devel] Re: [PATCH] elf: support ELF binaries in noMMU

Hi Greg,

THis breaks static building of target alpha:

/home/wbx/embedded-test/openadk/toolchain_qemu-alpha_uclibc-ng/usr/bin/alpha-openadk-linux-uclibc-gcc -c libc/misc/auxvt/getauxval.c -o libc/misc/auxvt/getauxval.os -Wall -Wstrict-prototypes -Wstrict-aliasing -Wp
In file included from ./ldso/include/ldso.h:189,
                 from libc/misc/auxvt/getauxval.c:21:
./ldso/include/dl-defs.h:76:10: fatal error: dl-sysdep.h: No such file or directory
   76 | #include <dl-sysdep.h>
      |          ^~~~~~~~~~~~~
compilation terminated.
gmake[6]: *** [Makerules:372: libc/misc/auxvt/getauxval.os] Error 1

I think it is this part of the patch:

Any idea?

best regards
 Waldemar

Greg Ungerer wrote,

> The Linux kernels ELF-FDPIC binfmt program loader can support loading and
> running conventional ELF format binaries on noMMU kernels when compiled
> appropriately. That is when they are constant displacement binaries such
> as generated using the -pie compile option.
> 
> Add a configure option to allow selecting ELF binary support in noMMU
> mode configurations on architectures that support this. The main
> requirement is to generate the ldso run-time loader to perform relocation
> at load time. These configurations do not support shared libraries, so
> there is no need to generate a full shared library, only the static
> version is required.
> 
> The use of ELF format binaries does mean a slightly simpler toolchain
> generation (does not require a -uclinux- for some architectures) and does
> not require an extra tool like elf2flt.
> 
> This initial support targets M68K, ARM and RISC-V architectures. No kernel
> changes are required, the required support for this is already in mainline
> kernels (certainly as of linux-6.6).
> 
> Note that for the M68K and ARM architectures that the initialized
> registers and stack layout at process startup is slightly different for
> the flat format loader and the ELF/ELF-FDPIC loaders. So we need some
> changes to the startup code (crt1.S) for them.
> 
> I have not done extensive testing outside of M68K, ARM and RISC-V.
> I had to make changes to a couple of the dl-startup.h architecture files
> to get them to build for this noMMU case. I did not dig down too deep on
> the reasons, but they still seem ok for the MMU case as well.
> 
> Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
> ---
>  Makerules                      |  3 +++
>  Rules.mak                      |  2 ++
>  extra/Configs/Config.in        |  9 +++++++--
>  extra/Configs/Config.in.arch   |  8 ++++++++
>  ldso/include/dl-defs.h         |  2 --
>  ldso/include/ldso.h            |  2 +-
>  ldso/ldso/arm/dl-startup.h     |  2 ++
>  ldso/ldso/m68k/dl-startup.h    |  3 +++
>  ldso/ldso/m68k/dl-sysdep.h     |  2 ++
>  ldso/ldso/riscv64/dl-startup.h |  2 ++
>  libc/sysdeps/linux/arm/crt1.S  |  2 +-
>  libc/sysdeps/linux/m68k/crt1.S | 10 +++++++---
>  12 files changed, 38 insertions(+), 9 deletions(-)
> 
> diff --git a/Makerules b/Makerules
> index 845d81897..1a7443c39 100644
> --- a/Makerules
> +++ b/Makerules
> @@ -22,6 +22,9 @@ ifeq ($(UCLIBC_FORMAT_SHARED_FLAT),y)
>  libs: $(lib-gdb-y)
>  endif
>  libs: $(lib-a-y)
> +ifeq ($(HAVE_LDSO),y)
> +$(lib-a-y): | $(ldso)
> +endif
>  endif
>  objs: all_objs
>  $(lib-so-y) $(lib-a-y): | $(top_builddir)lib
> diff --git a/Rules.mak b/Rules.mak
> index 5b9154b72..2aacee521 100644
> --- a/Rules.mak
> +++ b/Rules.mak
> @@ -167,6 +167,8 @@ endif
>  
>  ifneq ($(HAVE_SHARED),y)
>  libc :=
> +endif
> +ifneq ($(HAVE_LDSO),y)
>  interp :=
>  ldso :=
>  endif
> diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in
> index 287db13d2..18748d54b 100644
> --- a/extra/Configs/Config.in
> +++ b/extra/Configs/Config.in
> @@ -333,8 +333,9 @@ config STATIC_PIE
>  	bool "Add support for Static Position Independent Executables (PIE)"
>  	default n
>  	depends on DOPIC && !UCLIBC_FORMAT_FDPIC_ELF && \
> -		(TARGET_arm || TARGET_i386 || TARGET_x86_64 || TARGET_aarch64 || \
> -		 TARGET_mips || TARGET_xtensa || TARGET_powerpc)
> +		(TARGET_aarch64 || TARGET_arm || TARGET_i386 || \
> +		 TARGET_m68k || TARGET_mips || TARGET_powerpc || \
> +		 TARGET_riscv64 || TARGET_x86_64 || TARGET_xtensa)
>  
>  config ARCH_HAS_NO_SHARED
>  	bool
> @@ -346,9 +347,13 @@ config ARCH_HAS_NO_LDSO
>  config ARCH_HAS_UCONTEXT
>  	bool
>  
> +config HAVE_LDSO
> +	bool
> +
>  config HAVE_SHARED
>  	bool "Enable shared libraries"
>  	depends on !ARCH_HAS_NO_SHARED
> +	select HAVE_LDSO
>  	default y
>  	help
>  	  If you wish to build uClibc with support for shared libraries then
> diff --git a/extra/Configs/Config.in.arch b/extra/Configs/Config.in.arch
> index 91b639493..4bcf3ff3f 100644
> --- a/extra/Configs/Config.in.arch
> +++ b/extra/Configs/Config.in.arch
> @@ -10,6 +10,14 @@
>  if !ARCH_USE_MMU
>  choice
>  	prompt "Target File Format"
> +config UCLIBC_FORMAT_ELF
> +	bool "ELF (using ELF_FDPIC loader)"
> +	depends on !ARCH_USE_MMU && (TARGET_arm || TARGET_m68k || \
> +				     TARGET_riscv64)
> +	select DOPIC
> +	select STATIC_PIE
> +	select ARCH_HAS_NO_SHARED
> +	select HAVE_LDSO
>  config UCLIBC_FORMAT_FDPIC_ELF
>  	bool "FDPIC ELF"
>  	depends on !ARCH_USE_MMU && (TARGET_bfin || TARGET_frv || TARGET_arm)
> diff --git a/ldso/include/dl-defs.h b/ldso/include/dl-defs.h
> index daa6685cb..e404f17ec 100644
> --- a/ldso/include/dl-defs.h
> +++ b/ldso/include/dl-defs.h
> @@ -72,10 +72,8 @@ typedef struct {
>  #endif
>  
>  #ifdef _LIBC
> -#ifndef __ARCH_HAS_NO_SHARED__
>  /* arch specific defines */
>  #include <dl-sysdep.h>
> -#endif
>  #ifdef __TARGET_c6x__
>  #include <dl-sysdep.h>
>  #endif
> diff --git a/ldso/include/ldso.h b/ldso/include/ldso.h
> index 8d9d057a0..80d5d5dd5 100755
> --- a/ldso/include/ldso.h
> +++ b/ldso/include/ldso.h
> @@ -48,7 +48,7 @@
>  /* Pull in the MIN macro */
>  #include <sys/param.h>
>  /* Pull in the ldso syscalls and string functions */
> -#ifndef __ARCH_HAS_NO_SHARED__
> +#if !defined(__ARCH_HAS_NO_SHARED__) || !defined(__ARCH_HAS_NO_LDSO__)
>  #include <dl-syscall.h>
>  #include <dl-string.h>
>  /* Now the ldso specific headers */
> diff --git a/ldso/ldso/arm/dl-startup.h b/ldso/ldso/arm/dl-startup.h
> index cacd461e1..d00e7b053 100644
> --- a/ldso/ldso/arm/dl-startup.h
> +++ b/ldso/ldso/arm/dl-startup.h
> @@ -301,3 +301,5 @@ int raise(int sig)
>    _dl_exit(1);
>  }
>  #endif /* __FDPIC__ */
> +
> +#define DL_UPDATE_LOADADDR_HDR(LOADADDR, ADDR, PHDR)
> diff --git a/ldso/ldso/m68k/dl-startup.h b/ldso/ldso/m68k/dl-startup.h
> index dfece443f..9c3285e27 100644
> --- a/ldso/ldso/m68k/dl-startup.h
> +++ b/ldso/ldso/m68k/dl-startup.h
> @@ -55,6 +55,9 @@ _dl_start_user:\n\
>   * do something a little more subtle here.  */
>  #define GET_ARGV(ARGVP, ARGS) ARGVP = (((unsigned long *) ARGS) + 1)
>  
> +/* We can't call functions earlier in the dl startup process */
> +#define NO_FUNCS_BEFORE_BOOTSTRAP
> +
>  /* Handle relocation of the symbols in the dynamic loader. */
>  static __always_inline
>  void PERFORM_BOOTSTRAP_RELOC(ELF_RELOC *rpnt, unsigned long *reloc_addr,
> diff --git a/ldso/ldso/m68k/dl-sysdep.h b/ldso/ldso/m68k/dl-sysdep.h
> index 21937b259..5d2d7a097 100644
> --- a/ldso/ldso/m68k/dl-sysdep.h
> +++ b/ldso/ldso/m68k/dl-sysdep.h
> @@ -83,3 +83,5 @@ elf_machine_relative (Elf32_Addr load_off, const Elf32_Addr rel_addr,
>  		*reloc_addr = load_off + rpnt->r_addend;
>  	} while (--relative_count);
>  }
> +
> +#define DL_UPDATE_LOADADDR_HDR(LOADADDR, ADDR, PHDR)
> diff --git a/ldso/ldso/riscv64/dl-startup.h b/ldso/ldso/riscv64/dl-startup.h
> index dabe1bebd..82e525e66 100644
> --- a/ldso/ldso/riscv64/dl-startup.h
> +++ b/ldso/ldso/riscv64/dl-startup.h
> @@ -88,3 +88,5 @@ void PERFORM_BOOTSTRAP_RELOC(ELF_RELOC *rpnt, ElfW(Addr) *reloc_addr,
>  			_dl_exit(1);
>  	}
>  }
> +
> +#define DL_UPDATE_LOADADDR_HDR(LOADADDR, ADDR, PHDR)
> diff --git a/libc/sysdeps/linux/arm/crt1.S b/libc/sysdeps/linux/arm/crt1.S
> index fade1d25c..799f11080 100644
> --- a/libc/sysdeps/linux/arm/crt1.S
> +++ b/libc/sysdeps/linux/arm/crt1.S
> @@ -245,7 +245,7 @@ _start:
>  	mov fp, #0
>  	mov lr, #0
>  
> -#ifdef __ARCH_USE_MMU__
> +#if defined(__ARCH_USE_MMU__) || defined(__UCLIBC_FORMAT_ELF__)
>  #ifdef L_rcrt1
>  	/* We don't need to save a1 since no dynamic linker should have run */
>  	ldr a1, .L_GOT          /* Get value at .L_GOT + 0  (offset to GOT)*/
> diff --git a/libc/sysdeps/linux/m68k/crt1.S b/libc/sysdeps/linux/m68k/crt1.S
> index 815a6076f..e7292682b 100644
> --- a/libc/sysdeps/linux/m68k/crt1.S
> +++ b/libc/sysdeps/linux/m68k/crt1.S
> @@ -78,9 +78,13 @@ _start:
>  	sub.l %fp, %fp
>  
>  #if !defined __ARCH_USE_MMU__ && defined __PIC__
> +#ifdef UCLIBC_FORMAT_ELF
> +	move.l #_GLOBAL_OFFSET_TABLE_, %a5
> +#else
>  	/* Set up the global pointer.  The GOT is at the beginning of the
>  	   data segment, whose address is in %d5.  */
>  	move.l %d5,%a5
> +#endif
>  	.equ have_current_got, 1
>  #endif
>  	
> @@ -92,11 +96,11 @@ _start:
>  	   arguments for `main': argc, argv.  envp will be determined
>  	   later in __libc_start_main.  */
>  	move.l (%sp)+, %d0	/* Pop the argument count.  */
> -#ifndef __ARCH_USE_MMU__
> -	move.l (%sp)+, %a0
> -#else
> +#if defined(__ARCH_USE_MMU__) || defined(__UCLIBC_FORMAT_ELF__)
>  	move.l %sp, %a0		/* The argument vector starts just at the
>  				   current stack top.  */
> +#else
> +	move.l (%sp)+, %a0
>  #endif
>  
>  	/* Provide the highest stack address to the user code (for stacks
> -- 
> 2.25.1
> 
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