Re: [PATCH v2] ld.so: Initialize bootstrap_map.l_ld_readonly [BZ #28340]

[Carlos O'Donell <carlos@redhat.com>]

On 9/28/21 11:47, H.J. Lu via Libc-alpha wrote:
> 1. Define DL_RO_DYN_SECTION to initalize bootstrap_map.l_ld_readonly
> before calling elf_get_dynamic_info to get dynamic info in bootstrap_map,
> 2. Define a single
> 
> static inline bool
> dl_relocate_ld (const struct link_map *l)
> {
>   /* Don't relocate dynamic section if it is readonly  */
>   return !(l->l_ld_readonly || DL_RO_DYN_SECTION);
> }
> 
> This updates BZ #28340 fix.

Please post v3 with update for Adhemveral's change.

I'm reviewing this right now with the obvious merge conflict fix.

> ---
>  elf/rtld.c                       |  1 +
>  sysdeps/generic/dl-relocate-ld.h | 11 ++---------
>  sysdeps/generic/ldsodefs.h       | 10 ++++++++++
>  sysdeps/mips/dl-relocate-ld.h    | 11 ++---------
>  sysdeps/riscv/dl-relocate-ld.h   | 11 ++---------
>  5 files changed, 17 insertions(+), 27 deletions(-)
> 
> diff --git a/elf/rtld.c b/elf/rtld.c
> index 8d2bba3d43..83adf1c5f5 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -547,6 +547,7 @@ _dl_start (void *arg)
>  
>    /* Read our own dynamic section and fill in the info array.  */
>    bootstrap_map.l_ld = (void *) bootstrap_map.l_addr + elf_machine_dynamic ();
> +  bootstrap_map.l_ld_readonly = DL_RO_DYN_SECTION;

This conflicts with Adhemerval's recent change to elf_get_dynamic_info.

Could you please update this patch?

>    elf_get_dynamic_info (&bootstrap_map);

I'm testing the obvious merge conflict fix.

>  
>  #if NO_TLS_OFFSET != 0
> diff --git a/sysdeps/generic/dl-relocate-ld.h b/sysdeps/generic/dl-relocate-ld.h
> index 5fae206db9..cfb86c2d6a 100644
> --- a/sysdeps/generic/dl-relocate-ld.h
> +++ b/sysdeps/generic/dl-relocate-ld.h
> @@ -19,14 +19,7 @@
>  #ifndef _DL_RELOCATE_LD_H
>  #define _DL_RELOCATE_LD_H
>  
> -/* Return true if dynamic section in the shared library L should be
> -   relocated.  */
> -
> -static inline bool
> -dl_relocate_ld (const struct link_map *l)
> -{
> -  /* Don't relocate dynamic section if it is readonly  */
> -  return !l->l_ld_readonly;
> -}
> +/* The dynamic section is writable.  */
> +#define DL_RO_DYN_SECTION 0
>  
>  #endif /* _DL_RELOCATE_LD_H */
> diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
> index d49529da0d..668383ab80 100644
> --- a/sysdeps/generic/ldsodefs.h
> +++ b/sysdeps/generic/ldsodefs.h
> @@ -69,6 +69,16 @@ __BEGIN_DECLS
>     `ElfW(TYPE)' is used in place of `Elf32_TYPE' or `Elf64_TYPE'.  */
>  #define ELFW(type)	_ElfW (ELF, __ELF_NATIVE_CLASS, type)
>  
> +/* Return true if dynamic section in the shared library L should be
> +   relocated.  */
> +
> +static inline bool
> +dl_relocate_ld (const struct link_map *l)
> +{
> +  /* Don't relocate dynamic section if it is readonly  */
> +  return !(l->l_ld_readonly || DL_RO_DYN_SECTION);
> +}
> +
>  /* All references to the value of l_info[DT_PLTGOT],
>    l_info[DT_STRTAB], l_info[DT_SYMTAB], l_info[DT_RELA],
>    l_info[DT_REL], l_info[DT_JMPREL], and l_info[VERSYMIDX (DT_VERSYM)]
> diff --git a/sysdeps/mips/dl-relocate-ld.h b/sysdeps/mips/dl-relocate-ld.h
> index 0c18d9a567..376ad75dd1 100644
> --- a/sysdeps/mips/dl-relocate-ld.h
> +++ b/sysdeps/mips/dl-relocate-ld.h
> @@ -19,14 +19,7 @@
>  #ifndef _DL_RELOCATE_LD_H
>  #define _DL_RELOCATE_LD_H
>  
> -/* Return true if dynamic section in the shared library L should be
> -   relocated.  */
> -
> -static inline bool
> -dl_relocate_ld (const struct link_map *l)
> -{
> -  /* Never relocate dynamic section.  */
> -  return false;
> -}
> +/* The dynamic section is readonly.  */
> +#define DL_RO_DYN_SECTION 1
>  
>  #endif /* _DL_RELOCATE_LD_H */
> diff --git a/sysdeps/riscv/dl-relocate-ld.h b/sysdeps/riscv/dl-relocate-ld.h
> index 10327454b1..2ab2b8ac6c 100644
> --- a/sysdeps/riscv/dl-relocate-ld.h
> +++ b/sysdeps/riscv/dl-relocate-ld.h
> @@ -19,14 +19,7 @@
>  #ifndef _DL_RELOCATE_LD_H
>  #define _DL_RELOCATE_LD_H
>  
> -/* Return true if dynamic section in the shared library L should be
> -   relocated.  */
> -
> -static inline bool
> -dl_relocate_ld (const struct link_map *l)
> -{
> -  /* Never relocate dynamic section for ABI compatibility.  */
> -  return false;
> -}
> +/* The dynamic section is readonly for ABI compatibility.  */
> +#define DL_RO_DYN_SECTION 1
>  
>  #endif /* _DL_RELOCATE_LD_H */
> 


-- 
Cheers,
Carlos.