arm: Enable static-pie support (BZ 34098)

  It requires proper gcc support [1], and without proper compiler support
the arm configure disable static-pie support.

The start.S requires some adjustment to avoid loading main from
the GOT.

Checked on arm-linux-gnueabihf with and without the gcc patch applied.

[1] https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598610.html
---
 NEWS                     |  3 +++
 sysdeps/arm/configure    | 52 ++++++++++++++++++++++++++++++++++++++++
 sysdeps/arm/configure.ac | 29 ++++++++++++++++++++++
 sysdeps/arm/start.S      | 16 +++++++++++++
 4 files changed, 100 insertions(+)
  

On Fri, Apr 24, 2026 at 10:49:23AM -0300, Adhemerval Zanella wrote:
> It requires proper gcc support [1], and without proper compiler support
> the arm configure disable static-pie support.
> 
> The start.S requires some adjustment to avoid loading main from
> the GOT.
> 
> Checked on arm-linux-gnueabihf with and without the gcc patch applied.

Could you share how you tested it? Perhaps it makes sense to add a test
that is supposed to link successfully as a static PIE?

The patch seems OK but I struggle to test it properly.

> 
> [1] https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598610.html
> ---
>  NEWS                     |  3 +++
>  sysdeps/arm/configure    | 52 ++++++++++++++++++++++++++++++++++++++++
>  sysdeps/arm/configure.ac | 29 ++++++++++++++++++++++
>  sysdeps/arm/start.S      | 16 +++++++++++++
>  4 files changed, 100 insertions(+)
> 
> diff --git a/NEWS b/NEWS
> index eac9322161..6a45bb06ff 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -18,6 +18,9 @@ Major new features:
>  
>  * New locale added: hrx_BR (Hunsrik language spoken in Brazil).
>  
> +* Static PIE is ow support for arm-*-linux-gnueabi.  It requires toolchain
Nit: s/ow support/now supported/g

> +  support to correctly set the expected linker options.
> +
>  Deprecated and removed features, and other changes affecting compatibility:
>  
>  * Although malloc and related functions currently return pointers
> diff --git a/sysdeps/arm/configure b/sysdeps/arm/configure
> index 935e022c74..b964c3917a 100644
> --- a/sysdeps/arm/configure
> +++ b/sysdeps/arm/configure
>
> ...
>

OK

> diff --git a/sysdeps/arm/configure.ac b/sysdeps/arm/configure.ac
> index cd00ddc9d9..0c4f0f0de8 100644
> --- a/sysdeps/arm/configure.ac
> +++ b/sysdeps/arm/configure.ac
> @@ -1,6 +1,35 @@
>  GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
>  # Local configure fragment for sysdeps/arm.
>  
> +dnl Test if the foolchain supports static PIE, the -static-pie should not only
> +dnl be accepted, but also generate a ET_DYN without a INTERP entry.
> +AC_CACHE_CHECK([if compiler support static PIE],
> +libc_cv_static_pie_on_arm, [
> +cat > conftest.S <<\EOF
> +.text
> +.global _start
> +.type _start,#function
> +_start:
> +
> +.data
> +.align 2
> +ptr:
> +  /* This shoul produce an R_ARM_RELATIVE.  */
> +  .word _start
> +EOF
> +
> +  libc_cv_static_pie_on_arm=no
> +  if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -static-pie -nostdlib -fPIE -o conftest conftest.S]) \
> +     && AC_TRY_COMMAND([LC_ALL=C $READELF -Wr conftest | grep -q R_ARM_RELATIVE]) \
> +     && ! AC_TRY_COMMAND([LC_ALL=C $READELF -Wl conftest | grep -q INTERP])
> +  then
> +    libc_cv_static_pie_on_arm=yes
> +  fi
> +  rm -rf conftest* ])
> +if test "$libc_cv_static_pie_on_arm" = yes; then
> +  AC_DEFINE(SUPPORT_STATIC_PIE)
> +fi
> +

OK

> diff --git a/sysdeps/arm/start.S b/sysdeps/arm/start.S
> index a7e62b3934..68e032ef4d 100644
> --- a/sysdeps/arm/start.S
> +++ b/sysdeps/arm/start.S
> @@ -90,6 +90,7 @@ _start:
>  	push { a1 }
>  
>  #ifdef PIC
> +# ifdef SHARED
>  	ldr sl, .L_GOT
>  	adr a4, .L_GOT
>  	add sl, sl, a4
> @@ -103,6 +104,16 @@ _start:
>  	/* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
>  	/* Let the libc call main and exit with its return code.  */
>  	bl __libc_start_main(PLT)
> +# else
> +	ldr a1, .L_main_rel	/* Load the relative offset of main. */
> +	adr a4, .L_main_rel	/* Load the actual runtime address of the label. */
> +	add a1, a4, a1		/* Add them together to get the absolute address. */
> +
> +	mov a4, #0		/* Used to be init. */
> +	push { a4 }		/* Used to be fini. */
> +
> +	bl __libc_start_main
> +# endif

Nit: add /* # ifdef SHARED */ after 'endif'

>  #else
>  
>  	mov a4, #0		/* Used to init.  */
> @@ -119,9 +130,14 @@ _start:
>  
>  #ifdef PIC
>  	.align 2
> +# ifdef SHARED
>  .L_GOT:
>  	.word _GLOBAL_OFFSET_TABLE_ - .L_GOT
>  	.word main(GOT)
> +# else
> +.L_main_rel:
> +	.word main - .L_main_rel
> +# endif

OK

Cheers,
Yury
  

On 29/04/26 07:00, Yury Khrustalev wrote:
> On Fri, Apr 24, 2026 at 10:49:23AM -0300, Adhemerval Zanella wrote:
>> It requires proper gcc support [1], and without proper compiler support
>> the arm configure disable static-pie support.
>>
>> The start.S requires some adjustment to avoid loading main from
>> the GOT.
>>
>> Checked on arm-linux-gnueabihf with and without the gcc patch applied.
> 
> Could you share how you tested it? Perhaps it makes sense to add a test
> that is supposed to link successfully as a static PIE?

The easiest way to check the static-pie is to bootstrap a toolchain with 
the gcc patch, otherwise you will need to hack glibc testing to pass the
same flags when -static-pie is used.

The new configure.ac piece checks whether compiler does support it, similar
on how it was done recently for loongarch and riscv. If static-pie is
properly support (i.e, if compiler driver issues the linker with correct
flags and generates a ET_DYN without PT_INTERP with the expect RELATIVE
relocation), all static binaries will be built as static-pie and it will
fail to load without the start.S fix. 

> 
> The patch seems OK but I struggle to test it properly.
> 
>>
>> [1] https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598610.html
>> ---
>>  NEWS                     |  3 +++
>>  sysdeps/arm/configure    | 52 ++++++++++++++++++++++++++++++++++++++++
>>  sysdeps/arm/configure.ac | 29 ++++++++++++++++++++++
>>  sysdeps/arm/start.S      | 16 +++++++++++++
>>  4 files changed, 100 insertions(+)
>>
>> diff --git a/NEWS b/NEWS
>> index eac9322161..6a45bb06ff 100644
>> --- a/NEWS
>> +++ b/NEWS
>> @@ -18,6 +18,9 @@ Major new features:
>>  
>>  * New locale added: hrx_BR (Hunsrik language spoken in Brazil).
>>  
>> +* Static PIE is ow support for arm-*-linux-gnueabi.  It requires toolchain
> Nit: s/ow support/now supported/g
> 
>> +  support to correctly set the expected linker options.
>> +
>>  Deprecated and removed features, and other changes affecting compatibility:
>>  
>>  * Although malloc and related functions currently return pointers
>> diff --git a/sysdeps/arm/configure b/sysdeps/arm/configure
>> index 935e022c74..b964c3917a 100644
>> --- a/sysdeps/arm/configure
>> +++ b/sysdeps/arm/configure
>>
>> ...
>>
> 
> OK
> 
>> diff --git a/sysdeps/arm/configure.ac b/sysdeps/arm/configure.ac
>> index cd00ddc9d9..0c4f0f0de8 100644
>> --- a/sysdeps/arm/configure.ac
>> +++ b/sysdeps/arm/configure.ac
>> @@ -1,6 +1,35 @@
>>  GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
>>  # Local configure fragment for sysdeps/arm.
>>  
>> +dnl Test if the foolchain supports static PIE, the -static-pie should not only
>> +dnl be accepted, but also generate a ET_DYN without a INTERP entry.
>> +AC_CACHE_CHECK([if compiler support static PIE],
>> +libc_cv_static_pie_on_arm, [
>> +cat > conftest.S <<\EOF
>> +.text
>> +.global _start
>> +.type _start,#function
>> +_start:
>> +
>> +.data
>> +.align 2
>> +ptr:
>> +  /* This shoul produce an R_ARM_RELATIVE.  */
>> +  .word _start
>> +EOF
>> +
>> +  libc_cv_static_pie_on_arm=no
>> +  if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -static-pie -nostdlib -fPIE -o conftest conftest.S]) \
>> +     && AC_TRY_COMMAND([LC_ALL=C $READELF -Wr conftest | grep -q R_ARM_RELATIVE]) \
>> +     && ! AC_TRY_COMMAND([LC_ALL=C $READELF -Wl conftest | grep -q INTERP])
>> +  then
>> +    libc_cv_static_pie_on_arm=yes
>> +  fi
>> +  rm -rf conftest* ])
>> +if test "$libc_cv_static_pie_on_arm" = yes; then
>> +  AC_DEFINE(SUPPORT_STATIC_PIE)
>> +fi
>> +
> 
> OK
> 
>> diff --git a/sysdeps/arm/start.S b/sysdeps/arm/start.S
>> index a7e62b3934..68e032ef4d 100644
>> --- a/sysdeps/arm/start.S
>> +++ b/sysdeps/arm/start.S
>> @@ -90,6 +90,7 @@ _start:
>>  	push { a1 }
>>  
>>  #ifdef PIC
>> +# ifdef SHARED
>>  	ldr sl, .L_GOT
>>  	adr a4, .L_GOT
>>  	add sl, sl, a4
>> @@ -103,6 +104,16 @@ _start:
>>  	/* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
>>  	/* Let the libc call main and exit with its return code.  */
>>  	bl __libc_start_main(PLT)
>> +# else
>> +	ldr a1, .L_main_rel	/* Load the relative offset of main. */
>> +	adr a4, .L_main_rel	/* Load the actual runtime address of the label. */
>> +	add a1, a4, a1		/* Add them together to get the absolute address. */
>> +
>> +	mov a4, #0		/* Used to be init. */
>> +	push { a4 }		/* Used to be fini. */
>> +
>> +	bl __libc_start_main
>> +# endif
> 
> Nit: add /* # ifdef SHARED */ after 'endif'
> 
>>  #else
>>  
>>  	mov a4, #0		/* Used to init.  */
>> @@ -119,9 +130,14 @@ _start:
>>  
>>  #ifdef PIC
>>  	.align 2
>> +# ifdef SHARED
>>  .L_GOT:
>>  	.word _GLOBAL_OFFSET_TABLE_ - .L_GOT
>>  	.word main(GOT)
>> +# else
>> +.L_main_rel:
>> +	.word main - .L_main_rel
>> +# endif
> 
> OK
> 
> Cheers,
> Yury
>
  

> From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
> Sent: Wednesday, April 29, 2026 21:36
> To: Yury Khrustalev <yury.khrustalev@arm.com>
> Cc: libc-alpha@sourceware.org <libc-alpha@sourceware.org>; 정재윤/Task Leader/SW Platform(연)선행Platform개발실 Lightweight System Task <jaeyoon.jung@lge.com>; Sam James <sam@gentoo.org>
> Subject: Re: [PATCH] arm: Enable static-pie support (BZ 34098)
>  
> 
> 
> On 29/04/26 07:00, Yury Khrustalev wrote:
> > On Fri, Apr 24, 2026 at 10:49:23AM -0300, Adhemerval Zanella wrote:
> >> It requires proper gcc support [1], and without proper compiler support
> >> the arm configure disable static-pie support.
> >>
> >> The start.S requires some adjustment to avoid loading main from
> >> the GOT.
> >>
> >> Checked on arm-linux-gnueabihf with and without the gcc patch applied.
> >
> > Could you share how you tested it? Perhaps it makes sense to add a test
> > that is supposed to link successfully as a static PIE?
> 
> The easiest way to check the static-pie is to bootstrap a toolchain with
> the gcc patch, otherwise you will need to hack glibc testing to pass the
> same flags when -static-pie is used.
> 

In my case, I verified it in my Yocto build system with two patches applied
to the corresponding recipes in oe-core. The test result was successful as
shared in https://sourceware.org/bugzilla/show_bug.cgi?id=34098.
I'm also considering to send those patches to oe-core once this patch gets
accepted and merged.


Best regards,
---
Jaeyoon Jung
Software Platform Lab. / Corporate R&D / LG Electronics Inc.
  

On Wed, Apr 29, 2026 at 01:01:19PM +0000, Jaeyoon Jung wrote:
> > From:�Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
> > Sent:�Wednesday, April 29, 2026 21:36
> > To:�Yury Khrustalev <yury.khrustalev@arm.com>
> > Cc:�libc-alpha@sourceware.org <libc-alpha@sourceware.org>; Jaeyoon Jung <jaeyoon.jung@lge.com>; Sam James <sam@gentoo.org>
> > Subject:�Re: [PATCH] arm: Enable static-pie support (BZ 34098)
> > �
> > 
> > 
> > On 29/04/26 07:00, Yury Khrustalev wrote:
> > > On Fri, Apr 24, 2026 at 10:49:23AM -0300, Adhemerval Zanella wrote:
> > >> It requires proper gcc support [1], and without proper compiler support
> > >> the arm configure disable static-pie support.
> > >>
> > >> The start.S requires some adjustment to avoid loading main from
> > >> the GOT.
> > >>
> > >> Checked on arm-linux-gnueabihf with and without the gcc patch applied.
> > >
> > > Could you share how you tested it? Perhaps it makes sense to add a test
> > > that is supposed to link successfully as a static PIE?
> > 
> > The easiest way to check the static-pie is to bootstrap a toolchain with
> > the gcc patch, otherwise you will need to hack glibc testing to pass the
> > same flags when -static-pie is used.
> > 
> 
> In my case, I verified it in my Yocto build system with two patches applied
> to the corresponding recipes in oe-core. The test result was successful as
> shared in https://sourceware.org/bugzilla/show_bug.cgi?id=34098.
> I'm also considering to send those patches to oe-core once this patch gets
> accepted and merged.
> 
>

Thanks both!

In this case, LGTM Reviewed-by: Yury Khrustalev <yury.khrustalev@arm.com>

Adhemerval, feel free to push after fixing the two minor things I raised
in my previous email.

Thanks,
Yury
  

Adhemerval Zanella <adhemerval.zanella@linaro.org> writes:

> It requires proper gcc support [1], and without proper compiler support
> the arm configure disable static-pie support.
>
> The start.S requires some adjustment to avoid loading main from
> the GOT.
>
> Checked on arm-linux-gnueabihf with and without the gcc patch applied.
>
> [1] https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598610.html

Thanks. I'll handle the GCC side soon.

Reviewed-by: Sam James <sam@gentoo.org>

> ---
>  NEWS                     |  3 +++
>  sysdeps/arm/configure    | 52 ++++++++++++++++++++++++++++++++++++++++
>  sysdeps/arm/configure.ac | 29 ++++++++++++++++++++++
>  sysdeps/arm/start.S      | 16 +++++++++++++
>  4 files changed, 100 insertions(+)
>
> diff --git a/NEWS b/NEWS
> index eac9322161..6a45bb06ff 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -18,6 +18,9 @@ Major new features:
>  
>  * New locale added: hrx_BR (Hunsrik language spoken in Brazil).
>  
> +* Static PIE is ow support for arm-*-linux-gnueabi.  It requires
> toolchain

now supported

> +  support to correctly set the expected linker options.
> +
>  Deprecated and removed features, and other changes affecting compatibility:
>  
>  * Although malloc and related functions currently return pointers
> diff --git a/sysdeps/arm/configure b/sysdeps/arm/configure
> index 935e022c74..b964c3917a 100644
> --- a/sysdeps/arm/configure
> +++ b/sysdeps/arm/configure
> @@ -1,6 +1,58 @@
>  # This file is generated from configure.ac by Autoconf.  DO NOT EDIT!
>   # Local configure fragment for sysdeps/arm.
>  
> +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if compiler support static PIE" >&5
> +printf %s "checking if compiler support static PIE... " >&6; }
> +if test ${libc_cv_static_pie_on_arm+y}
> +then :
> +  printf %s "(cached) " >&6
> +else case e in #(
> +  e)
> +cat > conftest.S <<\EOF
> +.text
> +.global _start
> +.type _start,#function
> +_start:
> +
> +.data
> +.align 2
> +ptr:
> +  /* This shoul produce an R_ARM_RELATIVE.  */
> +  .word _start
> +EOF
> +
> +  libc_cv_static_pie_on_arm=no
> +  if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -static-pie -nostdlib -fPIE -o conftest conftest.S'
> +  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> +  (eval $ac_try) 2>&5
> +  ac_status=$?
> +  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> +  test $ac_status = 0; }; } \
> +     && { ac_try='LC_ALL=C $READELF -Wr conftest | grep -q R_ARM_RELATIVE'
> +  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> +  (eval $ac_try) 2>&5
> +  ac_status=$?
> +  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> +  test $ac_status = 0; }; } \
> +     && ! { ac_try='LC_ALL=C $READELF -Wl conftest | grep -q INTERP'
> +  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> +  (eval $ac_try) 2>&5
> +  ac_status=$?
> +  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> +  test $ac_status = 0; }; }
> +  then
> +    libc_cv_static_pie_on_arm=yes
> +  fi
> +  rm -rf conftest*  ;;
> +esac
> +fi
> +{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_static_pie_on_arm" >&5
> +printf "%s\n" "$libc_cv_static_pie_on_arm" >&6; }
> +if test "$libc_cv_static_pie_on_arm" = yes; then
> +  printf "%s\n" "#define SUPPORT_STATIC_PIE 1" >>confdefs.h
> +
> +fi
> +
>  # We check to see if the compiler and flags are
>  # selecting the hard-float ABI and if they are then
>  # we set libc_cv_arm_pcs_vfp to yes which causes
> diff --git a/sysdeps/arm/configure.ac b/sysdeps/arm/configure.ac
> index cd00ddc9d9..0c4f0f0de8 100644
> --- a/sysdeps/arm/configure.ac
> +++ b/sysdeps/arm/configure.ac
> @@ -1,6 +1,35 @@
>  GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
>  # Local configure fragment for sysdeps/arm.
>  
> +dnl Test if the foolchain supports static PIE, the -static-pie should not only
> +dnl be accepted, but also generate a ET_DYN without a INTERP entry.
> +AC_CACHE_CHECK([if compiler support static PIE],
> +libc_cv_static_pie_on_arm, [
> +cat > conftest.S <<\EOF
> +.text
> +.global _start
> +.type _start,#function
> +_start:
> +
> +.data
> +.align 2
> +ptr:
> +  /* This shoul produce an R_ARM_RELATIVE.  */

should

> +  .word _start
> +EOF
> +
> +  libc_cv_static_pie_on_arm=no
> +  if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS -static-pie -nostdlib -fPIE -o conftest conftest.S]) \
> +     && AC_TRY_COMMAND([LC_ALL=C $READELF -Wr conftest | grep -q R_ARM_RELATIVE]) \
> +     && ! AC_TRY_COMMAND([LC_ALL=C $READELF -Wl conftest | grep -q INTERP])
> +  then
> +    libc_cv_static_pie_on_arm=yes
> +  fi
> +  rm -rf conftest* ])
> +if test "$libc_cv_static_pie_on_arm" = yes; then
> +  AC_DEFINE(SUPPORT_STATIC_PIE)
> +fi
> +
>  # We check to see if the compiler and flags are
>  # selecting the hard-float ABI and if they are then
>  # we set libc_cv_arm_pcs_vfp to yes which causes
> diff --git a/sysdeps/arm/start.S b/sysdeps/arm/start.S
> index a7e62b3934..68e032ef4d 100644
> --- a/sysdeps/arm/start.S
> +++ b/sysdeps/arm/start.S
> @@ -90,6 +90,7 @@ _start:
>  	push { a1 }
>  
>  #ifdef PIC
> +# ifdef SHARED
>  	ldr sl, .L_GOT
>  	adr a4, .L_GOT
>  	add sl, sl, a4
> @@ -103,6 +104,16 @@ _start:
>  	/* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
>  	/* Let the libc call main and exit with its return code.  */
>  	bl __libc_start_main(PLT)
> +# else
> +	ldr a1, .L_main_rel	/* Load the relative offset of main. */
> +	adr a4, .L_main_rel	/* Load the actual runtime address of the label. */
> +	add a1, a4, a1		/* Add them together to get the absolute address. */
> +
> +	mov a4, #0		/* Used to be init. */
> +	push { a4 }		/* Used to be fini. */
> +
> +	bl __libc_start_main
> +# endif
>  #else
>  
>  	mov a4, #0		/* Used to init.  */
> @@ -119,9 +130,14 @@ _start:
>  
>  #ifdef PIC
>  	.align 2
> +# ifdef SHARED
>  .L_GOT:
>  	.word _GLOBAL_OFFSET_TABLE_ - .L_GOT
>  	.word main(GOT)
> +# else
> +.L_main_rel:
> +	.word main - .L_main_rel
> +# endif
>  #endif
>  
>         .cantunwind