[PATCH] rtld: Add new hook to initialize dp register on hppa

[H.J. Lu]

On Fri, Feb 11, 2022 at 9:30 AM John David Anglin <dave.anglin@bell.net> wrote:
>
> The test elf/tst-audit2 fails on hppa with a segmentation fault in the
> long branch stub used to call malloc from calloc.  This occur because
> the test is not a PIC executable and calloc is called from the dynamic
> linker before the dp register is initialized in _dl_start_user.
>
> The fix is to add a new hook, ELF_MACHINE_AFTER_RTLD_RELOC, in dl_main
> to allow initialization of the dp register just after relocation is
> completed.
>
> Okay?
>
> Dave
> ---
>
> diff --git a/elf/rtld.c b/elf/rtld.c
> index 19e328f89e..fcea41cb86 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -2333,6 +2333,10 @@ dl_main (const ElfW(Phdr) *phdr,
>    /* Make sure no new search directories have been added.  */
>    assert (GLRO(dl_init_all_dirs) == GL(dl_all_dirs));
>
> +#ifdef ELF_MACHINE_AFTER_RTLD_RELOC
> +  ELF_MACHINE_AFTER_RTLD_RELOC (main_map);
> +#endif

We should avoid macro  Please use an inline function instead.

>    if (rtld_multiple_ref)
>      {
>        /* There was an explicit ref to the dynamic linker as a shared lib.
> diff --git a/sysdeps/hppa/dl-machine.h b/sysdeps/hppa/dl-machine.h
> index da4d57d2e4..74a81dc1f7 100644
> --- a/sysdeps/hppa/dl-machine.h
> +++ b/sysdeps/hppa/dl-machine.h
> @@ -70,6 +70,18 @@ __hppa_init_bootstrap_fdesc_table (struct link_map *map)
>    map->l_mach.fptr_table = boot_table;
>  }
>
> +/* Set up dp for any non-PIC lib functions that may be called.  */
> +static inline void
> +set_dp (struct link_map *map)
> +{
> +  register Elf32_Addr dp asm ("%r27");
> +  dp = D_PTR (map, l_info[DT_PLTGOT]);
> +  asm volatile ("" : : "r" (dp));
> +}
> +
> +#define ELF_MACHINE_AFTER_RTLD_RELOC(map)                      \
> +       set_dp (map);
> +
>  #define ELF_MACHINE_BEFORE_RTLD_RELOC(map, dynamic_info)       \
>         __hppa_init_bootstrap_fdesc_table (map);                \
>         _dl_fptr_init();
> @@ -338,16 +350,6 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
>     its return value is the user program's entry point.  */
>
>  #define RTLD_START \
> -/* Set up dp for any non-PIC lib constructors that may be called.  */  \
> -static struct link_map * __attribute__((used))                         \
> -set_dp (struct link_map *map)                                          \
> -{                                                                      \
> -  register Elf32_Addr dp asm ("%r27");                                 \
> -  dp = D_PTR (map, l_info[DT_PLTGOT]);                                 \
> -  asm volatile ("" : : "r" (dp));                                      \
> -  return map;                                                          \
> -}                                                                      \
> -                                                                       \
>  asm (                                                                  \
>  "      .text\n"                                                        \
>  "      .globl _start\n"                                                \
> @@ -447,14 +449,11 @@ asm (                                                                     \
>  "      stw     %r24,-44(%sp)\n"                                        \
>                                                                         \
>  ".Lnofix:\n"                                                           \
> +       /* Call _dl_init(main_map, argc, argv, envp). */                \
>  "      addil   LT'_rtld_local,%r19\n"                                  \
>  "      ldw     RT'_rtld_local(%r1),%r26\n"                             \
> -"      bl      set_dp, %r2\n"                                          \
>  "      ldw     0(%r26),%r26\n"                                         \
>                                                                         \
> -       /* Call _dl_init(_dl_loaded, argc, argv, envp). */              \
> -"      copy    %r28,%r26\n"                                            \
> -                                                                       \
>         /* envp = argv + argc + 1 */                                    \
>  "      sh2add  %r25,%r24,%r23\n"                                       \
>  "      bl      _dl_init,%r2\n"                                         \
>


-- 
H.J.