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

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

The 12/07/2022 12:52, linzhuorong wrote:
> The version of binutils is 2.38
> Use gcc 7.3.0 just for testing, if there is no --static-pie, it may give ignore, I found only i386, arm, aarch64, loongarch use _DYNAMIC way to get, other are use GOT，
> what if I only fix arm? 

what is the issue you want to fix?

so far we haven't seen any.

you just misconfigure the glibc build.

> 
> -----邮件原件-----
> 发件人: Szabolcs Nagy <szabolcs.nagy@arm.com> 
> 发送时间: 2022年12月7日 17:14
> 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: 答复: [PATCH] aarch64: fix elf_machine_dynamic compile error [BZ #29835]
> 
> 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
> > >