Re: 答复: [PATCH] aarch64: fix elf_machine_dynamic compile error [BZ #29835]

[Szabolcs Nagy via Libc-alpha <libc-alpha@sourceware.org>]

The 12/07/2022 08:34, linzhuorong wrote:
> disable-default-pie compile out different results
> 
> The problem is why --enable-static-pie works in 7.3.0, but compiles error in 10.3.0?

-static-pie support was added in gcc 8 so this likely works with
gcc 7 because the configure option is just ignored then (and the
static linked executables are not PIE)

there can be linker issues causing gcc 10 to fail so the binutils
version matters too, not just the gcc version. (on aarch64 you
need at least version 2.30)

the compiler target seems to be arm-linux-gnueabi which is not aarch64,
so an aarch64 patch won't fix the issue.


> 
> Error log:
> /home/XXXX/workspace/compiler/gcc/build/arm-linux-glibc/arm_linux_glibc_build_dir/arm-linux-glibc/lib/gcc/arm-linux-gnueabi/10.3.0/../../../../arm-linux-gnueabi/bin/ld: /home/XXXX/workspace/compiler/gcc/build/arm-linux-glibc/arm_linux_glibc_build_dir/obj/build-glibc/libc.a(dl-reloc-static-pie.o): in function elf_machine_rel': /home/XXXX/workspace/compiler/gcc/open_source/arm-linux-glibc-build_src/glibc-2.34/elf/../sysdeps/arm/dl-machine.h:440: undefined reference to _DYNAMIC'
> /home/XXXX/workspace/compiler/gcc/build/arm-linux-glibc/arm_linux_glibc_build_dir/arm-linux-glibc/lib/gcc/arm-linux-gnueabi/10.3.0/../../../../arm-linux-gnueabi/bin/ld: /home/XXXX/workspace/compiler/gcc/open_source/arm-linux-glibc-build_src/glibc-2.34/elf/../sysdeps/arm/dl-machine.h:440: undefined reference to _DYNAMIC'
> 
> 
> -----邮件原件-----
> 发件人: Szabolcs Nagy <szabolcs.nagy@arm.com> 
> 发送时间: 2022年12月5日 22:55
> 收件人: linzhuorong <linzhuorong@huawei.com>
> 抄送: libc-alpha@sourceware.org; Nixiaoming <nixiaoming@huawei.com>; xiaojiangfeng <xiaojiangfeng@huawei.com>; douzhaolei <douzhaolei@huawei.com>; Wangbing(wangbing,RTOS/Poincare Lab) <wangbing6@huawei.com>; wangfangpeng (A) <wangfangpeng1@huawei.com>; Liuyang (Young,C) <young.liuyang@huawei.com>
> 主题: Re: [PATCH] aarch64: fix elf_machine_dynamic compile error [BZ #29835]
> 
> The 12/02/2022 11:59, linzhuorong via Libc-alpha wrote:
> > elf_machine_dynamic compile error when compiling glibc with 
> > --enable-static-pie option turned on, static executables do not have 
> > symbol _DYNAMIC
> 
> glibc no longer has --enable-static-pie, instead it has --disable-default-pie .
> 
> static pie should have _DYNAMIC symbol since it has dynamic relocations (relative relocs), what is the binutils version?
> 
> maybe glibc should disable default pie if old binutils is detected.
> 
> > 
> > Fixes: bca0f5cbc9257c13322b99e55235c4f21ba0bd82("aarch64: Make 
> > elf_machine_{load_address,dynamic} robust [BZ #28203]")
> > 
> > Signed-off-by linzhuorong <linzhuorong@huawei.com>
> > ---
> >  sysdeps/aarch64/dl-machine.h | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/sysdeps/aarch64/dl-machine.h 
> > b/sysdeps/aarch64/dl-machine.h index ae8b14425a..49b1d1ea0e 100644
> > --- a/sysdeps/aarch64/dl-machine.h
> > +++ b/sysdeps/aarch64/dl-machine.h
> > @@ -53,8 +53,9 @@ elf_machine_load_address (void)  static inline 
> > ElfW(Addr) __attribute__ ((unused))  elf_machine_dynamic (void)  {
> > -  extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
> > -  return (ElfW(Addr)) _DYNAMIC - elf_machine_load_address ();
> > +  /* Declaring this hidden ensures that a PC-relative reference is 
> > + uesed.  */  extern const ElfW(Addr) _GLOBAL_OFFSET_TABLE_[] 
> > + attribute_hidden;  return _GLOBAL_OFFSET_TABLE_[0];
> >  }
> >  
> >  /* Set up the loaded object described by L so its unrelocated PLT
> > --
> > 2.12.3
> >