Re: [PATCH] elf: Add <dl-r_debug.h>

[Xi Ruoyao <xry111@mengyan1223.wang>]

On Sat, 2022-01-29 at 11:41 -0800, H.J. Lu wrote:
> On Sat, Jan 29, 2022 at 06:04:12AM +0800, Xi Ruoyao wrote:
> > On Fri, 2022-01-28 at 13:22 -0800, H.J. Lu wrote:
> > 
> > > You should drop pldd in filename and also handle tst-dlmopen4.c
> > > in the same header file.
> > 
> > v3: pldd and tst-dlmopen4 change revised as a new patch series.
> 
> Can you try this patch instead?

It looks a lot better than mine :).

Tested on mips64 (N64 ABI) and x86_64, result good.

> H.J.
> ---
> Add <dl-r_debug.h> to get the adddress of the r_debug structure after
> relocation and its offset before relocation from the PT_DYNAMIC
> segment
> to support DT_DEBUG, DT_MIPS_RLD_MAP_REL and DT_MIPS_RLD_MAP.
> 
> Co-developed-by: Xi Ruoyao <xry111@mengyan1223.wang>
> ---
>  elf/pldd-xx.c                | 34 +++++++++++--------
>  elf/tst-dlmopen4.c           | 15 +++------
>  sysdeps/generic/dl-r_debug.h | 36 ++++++++++++++++++++
>  sysdeps/mips/dl-r_debug.h    | 64
> ++++++++++++++++++++++++++++++++++++
>  4 files changed, 124 insertions(+), 25 deletions(-)
>  create mode 100644 sysdeps/generic/dl-r_debug.h
>  create mode 100644 sysdeps/mips/dl-r_debug.h
> 
> diff --git a/elf/pldd-xx.c b/elf/pldd-xx.c
> index 1cdfb49c53..30513b423f 100644
> --- a/elf/pldd-xx.c
> +++ b/elf/pldd-xx.c
> @@ -22,6 +22,8 @@
>  #define EW_(e, w, t) EW__(e, w, _##t)
>  #define EW__(e, w, t) e##w##t
>  
> +#include <dl-r_debug.h>
> +
>  struct E(link_map)
>  {
>    EW(Addr) l_addr;
> @@ -126,21 +128,25 @@ E(find_maps) (const char *exe, int memfd, pid_t
> pid, void *auxv,
>             != p[i].p_filesz)
>           error (EXIT_FAILURE, 0, gettext ("cannot read dynamic
> section"));
>  
> -       /* Search for the DT_DEBUG entry.  */
> +       /* Search for the struct r_debug.  */
>         for (unsigned int j = 0; j < p[i].p_filesz / sizeof (EW(Dyn));
> ++j)
> -         if (dyn[j].d_tag == DT_DEBUG && dyn[j].d_un.d_ptr != 0)
> -           {
> -             struct E(r_debug) r;
> -             if (pread (memfd, &r, sizeof (r), dyn[j].d_un.d_ptr)
> -                 != sizeof (r))
> -               error (EXIT_FAILURE, 0, gettext ("cannot read
> r_debug"));
> -
> -             if (r.r_map != 0)
> -               {
> -                 list = r.r_map;
> -                 break;
> -               }
> -           }
> +         {
> +           EW(Addr) off = offset + p[i].p_vaddr + sizeof (EW(Dyn)) *
> j;
> +           off = E(r_debug_offset) (&dyn[j], memfd, off);
> +           if (off != 0)
> +             {
> +               struct E(r_debug) r;
> +               if (pread (memfd, &r, sizeof (r), off)
> +                   != sizeof (r))
> +                 error (EXIT_FAILURE, 0, gettext ("cannot read
> r_debug"));
> +
> +               if (r.r_map != 0)
> +                 {
> +                   list = r.r_map;
> +                   break;
> +                 }
> +             }
> +         }
>  
>         free (dyn);
>         break;
> diff --git a/elf/tst-dlmopen4.c b/elf/tst-dlmopen4.c
> index d8bcf7e9d5..8456f89053 100644
> --- a/elf/tst-dlmopen4.c
> +++ b/elf/tst-dlmopen4.c
> @@ -25,16 +25,9 @@
>  #include <support/check.h>
>  #include <support/test-driver.h>
>  
> -#ifndef ELF_MACHINE_GET_R_DEBUG
> -# define ELF_MACHINE_GET_R_DEBUG(d) \
> -    (__extension__ ({                                          \
> -      struct r_debug_extended *debug;                          \
> -      if ((d)->d_tag == DT_DEBUG)                              \
> -       debug = (struct r_debug_extended *) (d)->d_un.d_ptr;    \
> -      else                                                     \
> -       debug = NULL;                                           \
> -      debug; }))
> -#endif
> +#define E(x) x
> +#define EW(x) ElfW(x)
> +#include <dl-r_debug.h>
>  
>  static int
>  do_test (void)
> @@ -44,7 +37,7 @@ do_test (void)
>  
>    for (d = _DYNAMIC; d->d_tag != DT_NULL; ++d)
>      {
> -      debug = ELF_MACHINE_GET_R_DEBUG (d);
> +      debug = (struct r_debug_extended *) r_debug_address (d);
>        if (debug != NULL)
>         break;
>      }
> diff --git a/sysdeps/generic/dl-r_debug.h b/sysdeps/generic/dl-
> r_debug.h
> new file mode 100644
> index 0000000000..e3edeb4f06
> --- /dev/null
> +++ b/sysdeps/generic/dl-r_debug.h
> @@ -0,0 +1,36 @@
> +/* Function to access r_debug structure.  Generic version.
> +   Copyright (C) 2022 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be
> useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +/* Return the address of the struct r_debug after relocation.  */
> +
> +static inline EW(Addr)
> +E(r_debug_address) (EW(Dyn) *d)
> +{
> +  if (d->d_tag == DT_DEBUG)
> +    return (EW(Addr)) d->d_un.d_ptr;
> +
> +  return 0;
> +}
> +
> +/* Return the offset of the struct r_debug before relocation.  */
> +
> +static inline EW(Addr)
> +E(r_debug_offset) (EW(Dyn) *d, int fd, EW(Addr) offset)
> +{
> +  return E(r_debug_address) (d);
> +}
> diff --git a/sysdeps/mips/dl-r_debug.h b/sysdeps/mips/dl-r_debug.h
> new file mode 100644
> index 0000000000..edd83d46fd
> --- /dev/null
> +++ b/sysdeps/mips/dl-r_debug.h
> @@ -0,0 +1,64 @@
> +/* Function to access r_debug structure.  MIPS specific version.
> +   Copyright (C) 2022 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be
> useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#ifdef EW_
> +/* Return the offset of the struct r_debug before relocation.  */
> +
> +static inline EW(Addr)
> +E(r_debug_offset) (EW(Dyn) *d, int fd, EW(Addr) offset)
> +{
> +  switch (d->d_tag)
> +    {
> +    case DT_MIPS_RLD_MAP_REL:
> +      offset += d->d_un.d_val;
> +      break;
> +    case DT_MIPS_RLD_MAP:
> +      offset = d->d_un.d_ptr;
> +      break;
> +    default:
> +      return 0;
> +    }
> +
> +  if (pread (fd, &offset, sizeof (offset), offset) != sizeof
> (offset))
> +    return 0;
> +
> +  return offset;
> +}
> +#else
> +/* Return the address of the struct r_debug after relocation.  */
> +
> +static inline EW(Addr)
> +E(r_debug_address) (EW(Dyn) *d)
> +{
> +  EW(Addr) ptr;
> +
> +  switch (d->d_tag)
> +    {
> +    case DT_MIPS_RLD_MAP_REL:
> +      ptr = ((EW(Addr)) d) + d->d_un.d_val;
> +      break;
> +    case DT_MIPS_RLD_MAP:
> +      ptr = d->d_un.d_ptr;
> +      break;
> +    default:
> +      return 0;
> +    }
> +
> +  return *(EW(Addr) *) ptr;
> +}
> +#endif

-- 
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University