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

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

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?

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
>