[PATCH] mips: pldd: support DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL

[PATCH] mips: pldd: support DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL

[Xi Ruoyao]

MIPS uses DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL for accessing r_debug,
instead of DT_DEBUG.
---
 elf/pldd-xx.c | 67 ++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 53 insertions(+), 14 deletions(-)

diff --git a/elf/pldd-xx.c b/elf/pldd-xx.c
index 1cdfb49c53..ec397f00e5 100644
--- a/elf/pldd-xx.c
+++ b/elf/pldd-xx.c
@@ -22,6 +22,12 @@
 #define EW_(e, w, t) EW__(e, w, _##t)
 #define EW__(e, w, t) e##w##t
 
+#if CLASS == 32
+typedef Elf32_Word E(val_type);
+#else
+typedef Elf64_Xword E(val_type);
+#endif
+
 struct E(link_map)
 {
   EW(Addr) l_addr;
@@ -70,6 +76,35 @@ _Static_assert (offsetof (struct r_debug, r_map)
 		== offsetof (struct E(r_debug), r_map), "r_map");
 #endif
 
+static EW(Addr)
+E(r_debug_offset) (EW(Dyn) *d, int memfd, EW(Addr) d_addr)
+{
+#ifdef __mips__
+  EW(Addr) ptr;
+
+  switch (d->d_tag)
+    {
+    case DT_MIPS_RLD_MAP_REL:
+      ptr = d_addr + d->d_un.d_val;
+      break;
+    case DT_MIPS_RLD_MAP:
+      ptr = d->d_un.d_ptr;
+      break;
+    default:
+      return 0;
+    }
+
+    if (pread (memfd, &ptr, sizeof (ptr), ptr) != sizeof (ptr))
+      return 0;
+
+    return ptr;
+#else
+  if (d->d_tag == DT_DEBUG)
+    return (off_t) d->d_un.d_ptr;
+
+  return 0;
+#endif
+}
 
 static int
 
@@ -126,21 +161,25 @@ 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 r_debug struct.  */
 	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) d_addr = offset + p[i].p_vaddr + sizeof (EW(Dyn)) * j;
+	    EW(Addr) off = E(r_debug_offset)(&dyn[j], memfd, d_addr);
+	    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;
-- 
2.35.0

Re: [PATCH] mips: pldd: support DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL

[H.J. Lu]

On Fri, Jan 28, 2022 at 10:57 AM Xi Ruoyao via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> MIPS uses DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL for accessing r_debug,
> instead of DT_DEBUG.
> ---
>  elf/pldd-xx.c | 67 ++++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 53 insertions(+), 14 deletions(-)
>
> diff --git a/elf/pldd-xx.c b/elf/pldd-xx.c
> index 1cdfb49c53..ec397f00e5 100644
> --- a/elf/pldd-xx.c
> +++ b/elf/pldd-xx.c
> @@ -22,6 +22,12 @@
>  #define EW_(e, w, t) EW__(e, w, _##t)
>  #define EW__(e, w, t) e##w##t
>
> +#if CLASS == 32
> +typedef Elf32_Word E(val_type);
> +#else
> +typedef Elf64_Xword E(val_type);
> +#endif
> +
>  struct E(link_map)
>  {
>    EW(Addr) l_addr;
> @@ -70,6 +76,35 @@ _Static_assert (offsetof (struct r_debug, r_map)
>                 == offsetof (struct E(r_debug), r_map), "r_map");
>  #endif
>
> +static EW(Addr)
> +E(r_debug_offset) (EW(Dyn) *d, int memfd, EW(Addr) d_addr)
> +{
> +#ifdef __mips__
> +  EW(Addr) ptr;
> +
> +  switch (d->d_tag)
> +    {
> +    case DT_MIPS_RLD_MAP_REL:
> +      ptr = d_addr + d->d_un.d_val;
> +      break;
> +    case DT_MIPS_RLD_MAP:
> +      ptr = d->d_un.d_ptr;
> +      break;
> +    default:
> +      return 0;
> +    }
> +
> +    if (pread (memfd, &ptr, sizeof (ptr), ptr) != sizeof (ptr))
> +      return 0;
> +
> +    return ptr;
> +#else
> +  if (d->d_tag == DT_DEBUG)
> +    return (off_t) d->d_un.d_ptr;
> +
> +  return 0;
> +#endif
> +}
>
>  static int
>
> @@ -126,21 +161,25 @@ 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 r_debug struct.  */
>         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) d_addr = offset + p[i].p_vaddr + sizeof (EW(Dyn)) * j;
> +           EW(Addr) off = E(r_debug_offset)(&dyn[j], memfd, d_addr);
> +           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;
> --
> 2.35.0
>
>

I think a header file to access r_debug works better.  MIPS can provide
one to override the generic header file.

-- 
H.J.

Re: [PATCH] mips: pldd: support DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL

[Adhemerval Zanella]

On 28/01/2022 17:45, H.J. Lu via Libc-alpha wrote:
> On Fri, Jan 28, 2022 at 10:57 AM Xi Ruoyao via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
>>
>> MIPS uses DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL for accessing r_debug,
>> instead of DT_DEBUG.
>> ---
>>  elf/pldd-xx.c | 67 ++++++++++++++++++++++++++++++++++++++++-----------
>>  1 file changed, 53 insertions(+), 14 deletions(-)
>>
>> diff --git a/elf/pldd-xx.c b/elf/pldd-xx.c
>> index 1cdfb49c53..ec397f00e5 100644
>> --- a/elf/pldd-xx.c
>> +++ b/elf/pldd-xx.c
>> @@ -22,6 +22,12 @@
>>  #define EW_(e, w, t) EW__(e, w, _##t)
>>  #define EW__(e, w, t) e##w##t
>>
>> +#if CLASS == 32
>> +typedef Elf32_Word E(val_type);
>> +#else
>> +typedef Elf64_Xword E(val_type);
>> +#endif
>> +
>>  struct E(link_map)
>>  {
>>    EW(Addr) l_addr;
>> @@ -70,6 +76,35 @@ _Static_assert (offsetof (struct r_debug, r_map)
>>                 == offsetof (struct E(r_debug), r_map), "r_map");
>>  #endif
>>
>> +static EW(Addr)
>> +E(r_debug_offset) (EW(Dyn) *d, int memfd, EW(Addr) d_addr)
>> +{
>> +#ifdef __mips__
>> +  EW(Addr) ptr;
>> +
>> +  switch (d->d_tag)
>> +    {
>> +    case DT_MIPS_RLD_MAP_REL:
>> +      ptr = d_addr + d->d_un.d_val;
>> +      break;
>> +    case DT_MIPS_RLD_MAP:
>> +      ptr = d->d_un.d_ptr;
>> +      break;
>> +    default:
>> +      return 0;
>> +    }
>> +
>> +    if (pread (memfd, &ptr, sizeof (ptr), ptr) != sizeof (ptr))
>> +      return 0;
>> +
>> +    return ptr;
>> +#else
>> +  if (d->d_tag == DT_DEBUG)
>> +    return (off_t) d->d_un.d_ptr;
>> +
>> +  return 0;
>> +#endif
>> +}
>>
>>  static int
>>
>> @@ -126,21 +161,25 @@ 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 r_debug struct.  */
>>         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) d_addr = offset + p[i].p_vaddr + sizeof (EW(Dyn)) * j;
>> +           EW(Addr) off = E(r_debug_offset)(&dyn[j], memfd, d_addr);
>> +           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;
>> --
>> 2.35.0
>>
>>
> 
> I think a header file to access r_debug works better.  MIPS can provide
> one to override the generic header file.
> 

Agreed, I think we should avoid arch specific defines (__mips__) on generic
code.

Re: [PATCH] mips: pldd: support DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL

[Carlos O'Donell]

On 1/28/22 15:48, Adhemerval Zanella via Libc-alpha wrote:
> 
> 
> On 28/01/2022 17:45, H.J. Lu via Libc-alpha wrote:
>> On Fri, Jan 28, 2022 at 10:57 AM Xi Ruoyao via Libc-alpha
>> <libc-alpha@sourceware.org> wrote:
>>>
>>> MIPS uses DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL for accessing r_debug,
>>> instead of DT_DEBUG.
>>> ---
>>>  elf/pldd-xx.c | 67 ++++++++++++++++++++++++++++++++++++++++-----------
>>>  1 file changed, 53 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/elf/pldd-xx.c b/elf/pldd-xx.c
>>> index 1cdfb49c53..ec397f00e5 100644
>>> --- a/elf/pldd-xx.c
>>> +++ b/elf/pldd-xx.c
>>> @@ -22,6 +22,12 @@
>>>  #define EW_(e, w, t) EW__(e, w, _##t)
>>>  #define EW__(e, w, t) e##w##t
>>>
>>> +#if CLASS == 32
>>> +typedef Elf32_Word E(val_type);
>>> +#else
>>> +typedef Elf64_Xword E(val_type);
>>> +#endif
>>> +
>>>  struct E(link_map)
>>>  {
>>>    EW(Addr) l_addr;
>>> @@ -70,6 +76,35 @@ _Static_assert (offsetof (struct r_debug, r_map)
>>>                 == offsetof (struct E(r_debug), r_map), "r_map");
>>>  #endif
>>>
>>> +static EW(Addr)
>>> +E(r_debug_offset) (EW(Dyn) *d, int memfd, EW(Addr) d_addr)
>>> +{
>>> +#ifdef __mips__
>>> +  EW(Addr) ptr;
>>> +
>>> +  switch (d->d_tag)
>>> +    {
>>> +    case DT_MIPS_RLD_MAP_REL:
>>> +      ptr = d_addr + d->d_un.d_val;
>>> +      break;
>>> +    case DT_MIPS_RLD_MAP:
>>> +      ptr = d->d_un.d_ptr;
>>> +      break;
>>> +    default:
>>> +      return 0;
>>> +    }
>>> +
>>> +    if (pread (memfd, &ptr, sizeof (ptr), ptr) != sizeof (ptr))
>>> +      return 0;
>>> +
>>> +    return ptr;
>>> +#else
>>> +  if (d->d_tag == DT_DEBUG)
>>> +    return (off_t) d->d_un.d_ptr;
>>> +
>>> +  return 0;
>>> +#endif
>>> +}
>>>
>>>  static int
>>>
>>> @@ -126,21 +161,25 @@ 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 r_debug struct.  */
>>>         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) d_addr = offset + p[i].p_vaddr + sizeof (EW(Dyn)) * j;
>>> +           EW(Addr) off = E(r_debug_offset)(&dyn[j], memfd, d_addr);
>>> +           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;
>>> --
>>> 2.35.0
>>>
>>>
>>
>> I think a header file to access r_debug works better.  MIPS can provide
>> one to override the generic header file.
>>
> 
> Agreed, I think we should avoid arch specific defines (__mips__) on generic
> code.
 
Ah! I see, the objection if about arch-defines in tests. Yes, lets clean that up.

-- 
Cheers,
Carlos.

[PATCH v2] mips: pldd: support DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL

[Xi Ruoyao]

[v2: remove useless typedef, seperate E(r_debug_offset) into a header.]

MIPS uses DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL for accessing r_debug,
instead of DT_DEBUG.

Signed-off-by: Xi Ruoyao <xry111@mengyan1223.wang>
---
 elf/pldd-xx.c                     | 34 +++++++++++++++-----------
 sysdeps/generic/elf-pldd-rdebug.h | 26 ++++++++++++++++++++
 sysdeps/mips/elf-pldd-rdebug.h    | 40 +++++++++++++++++++++++++++++++
 3 files changed, 86 insertions(+), 14 deletions(-)
 create mode 100644 sysdeps/generic/elf-pldd-rdebug.h
 create mode 100644 sysdeps/mips/elf-pldd-rdebug.h

diff --git a/elf/pldd-xx.c b/elf/pldd-xx.c
index 1cdfb49c53..368528371d 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 <elf-pldd-rdebug.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 r_debug struct.  */
 	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) d_addr = offset + p[i].p_vaddr + sizeof (EW(Dyn)) * j;
+	    EW(Addr) off = E(r_debug_offset)(&dyn[j], memfd, d_addr);
+	    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/sysdeps/generic/elf-pldd-rdebug.h b/sysdeps/generic/elf-pldd-rdebug.h
new file mode 100644
index 0000000000..6df651cd55
--- /dev/null
+++ b/sysdeps/generic/elf-pldd-rdebug.h
@@ -0,0 +1,26 @@
+/* Function to access r_debug structure for pldd.
+   Copyright (C) 2020-2022 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/>.  */
+
+static EW(Addr)
+E(r_debug_offset) (EW(Dyn) *d, int, EW(Addr))
+{
+  if (d->d_tag == DT_DEBUG)
+    return (EW(Addr)) d->d_un.d_ptr;
+
+  return 0;
+}
diff --git a/sysdeps/mips/elf-pldd-rdebug.h b/sysdeps/mips/elf-pldd-rdebug.h
new file mode 100644
index 0000000000..89a20c191a
--- /dev/null
+++ b/sysdeps/mips/elf-pldd-rdebug.h
@@ -0,0 +1,40 @@
+/* Function to access r_debug structure for pldd, MIPS specific version.
+   Copyright (C) 2020-2022 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/>.  */
+
+static EW(Addr)
+E(r_debug_offset) (EW(Dyn) *d, int memfd, EW(Addr) d_addr)
+{
+  EW(Addr) ptr;
+
+  switch (d->d_tag)
+    {
+    case DT_MIPS_RLD_MAP_REL:
+      ptr = d_addr + d->d_un.d_val;
+      break;
+    case DT_MIPS_RLD_MAP:
+      ptr = d->d_un.d_ptr;
+      break;
+    default:
+      return 0;
+    }
+
+    if (pread (memfd, &ptr, sizeof (ptr), ptr) != sizeof (ptr))
+      return 0;
+
+    return ptr;
+}
-- 
2.35.0

Re: [PATCH v2] mips: pldd: support DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL

[H.J. Lu]

On Fri, Jan 28, 2022 at 1:17 PM Xi Ruoyao <xry111@mengyan1223.wang> wrote:
>
> [v2: remove useless typedef, seperate E(r_debug_offset) into a header.]
>
> MIPS uses DT_MIPS_RLD_MAP and DT_MIPS_RLD_MAP_REL for accessing r_debug,
> instead of DT_DEBUG.
>
> Signed-off-by: Xi Ruoyao <xry111@mengyan1223.wang>
> ---
>  elf/pldd-xx.c                     | 34 +++++++++++++++-----------
>  sysdeps/generic/elf-pldd-rdebug.h | 26 ++++++++++++++++++++
>  sysdeps/mips/elf-pldd-rdebug.h    | 40 +++++++++++++++++++++++++++++++
>  3 files changed, 86 insertions(+), 14 deletions(-)
>  create mode 100644 sysdeps/generic/elf-pldd-rdebug.h
>  create mode 100644 sysdeps/mips/elf-pldd-rdebug.h
>
> diff --git a/elf/pldd-xx.c b/elf/pldd-xx.c
> index 1cdfb49c53..368528371d 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 <elf-pldd-rdebug.h>

You should drop pldd in filename and also handle tst-dlmopen4.c
in the same header file.

> +
>  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 r_debug struct.  */
>         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) d_addr = offset + p[i].p_vaddr + sizeof (EW(Dyn)) * j;
> +           EW(Addr) off = E(r_debug_offset)(&dyn[j], memfd, d_addr);
> +           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/sysdeps/generic/elf-pldd-rdebug.h b/sysdeps/generic/elf-pldd-rdebug.h
> new file mode 100644
> index 0000000000..6df651cd55
> --- /dev/null
> +++ b/sysdeps/generic/elf-pldd-rdebug.h
> @@ -0,0 +1,26 @@
> +/* Function to access r_debug structure for pldd.
> +   Copyright (C) 2020-2022 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/>.  */
> +
> +static EW(Addr)
> +E(r_debug_offset) (EW(Dyn) *d, int, EW(Addr))
> +{
> +  if (d->d_tag == DT_DEBUG)
> +    return (EW(Addr)) d->d_un.d_ptr;
> +
> +  return 0;
> +}
> diff --git a/sysdeps/mips/elf-pldd-rdebug.h b/sysdeps/mips/elf-pldd-rdebug.h
> new file mode 100644
> index 0000000000..89a20c191a
> --- /dev/null
> +++ b/sysdeps/mips/elf-pldd-rdebug.h
> @@ -0,0 +1,40 @@
> +/* Function to access r_debug structure for pldd, MIPS specific version.
> +   Copyright (C) 2020-2022 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/>.  */
> +
> +static EW(Addr)
> +E(r_debug_offset) (EW(Dyn) *d, int memfd, EW(Addr) d_addr)
> +{
> +  EW(Addr) ptr;
> +
> +  switch (d->d_tag)
> +    {
> +    case DT_MIPS_RLD_MAP_REL:
> +      ptr = d_addr + d->d_un.d_val;
> +      break;
> +    case DT_MIPS_RLD_MAP:
> +      ptr = d->d_un.d_ptr;
> +      break;
> +    default:
> +      return 0;
> +    }
> +
> +    if (pread (memfd, &ptr, sizeof (ptr), ptr) != sizeof (ptr))
> +      return 0;
> +
> +    return ptr;
> +}
> --
> 2.35.0
>
>


-- 
H.J.

[PATCH v3 0/3] mips: add target-specific r_debug offset

[Xi Ruoyao]

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

[PATCH v3 1/3] add sysdeps/{generic,mips}/elfxx-r_debug.h

[Xi Ruoyao]

Some targets (notably, MIPS) have target-specific way to get the address
of r_debug instead of the normal DT_DEBUG.  Add a header wrapping the
difference.
---
 sysdeps/generic/elfxx-r_debug.h | 26 ++++++++++++++++++
 sysdeps/mips/elfxx-r_debug.h    | 48 +++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+)
 create mode 100644 sysdeps/generic/elfxx-r_debug.h
 create mode 100644 sysdeps/mips/elfxx-r_debug.h

diff --git a/sysdeps/generic/elfxx-r_debug.h b/sysdeps/generic/elfxx-
r_debug.h
new file mode 100644
index 0000000000..7083c95e36
--- /dev/null
+++ b/sysdeps/generic/elfxx-r_debug.h
@@ -0,0 +1,26 @@
+/* Function to access r_debug structure.
+   Copyright (C) 2020-2022 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/>.  */
+
+static EW(Addr)
+E(r_debug_offset) (EW(Dyn) *d, int, EW(Addr))
+{
+  if (d->d_tag == DT_DEBUG)
+    return (EW(Addr)) d->d_un.d_ptr;
+
+  return 0;
+}
diff --git a/sysdeps/mips/elfxx-r_debug.h b/sysdeps/mips/elfxx-r_debug.h
new file mode 100644
index 0000000000..a13d069c35
--- /dev/null
+++ b/sysdeps/mips/elfxx-r_debug.h
@@ -0,0 +1,48 @@
+/* Function to access r_debug structure, MIPS specific version.
+   Copyright (C) 2020-2022 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/>.  */
+
+static EW(Addr)
+E(r_debug_offset) (EW(Dyn) *d, int memfd, EW(Addr) d_addr)
+{
+  EW(Addr) ptr;
+
+#ifdef R_DEBUG_IN_PROCESS
+  d_addr = (EW(Addr)) d;
+#endif
+
+  switch (d->d_tag)
+    {
+    case DT_MIPS_RLD_MAP_REL:
+      ptr = d_addr + d->d_un.d_val;
+      break;
+    case DT_MIPS_RLD_MAP:
+      ptr = d->d_un.d_ptr;
+      break;
+    default:
+      return 0;
+    }
+
+#ifdef R_DEBUG_IN_PROCESS
+  ptr = *(EW(Addr) *) ptr;
+#else
+  if (pread (memfd, &ptr, sizeof (ptr), ptr) != sizeof (ptr))
+    return 0;
+#endif
+
+  return ptr;
+}
-- 
2.35.0

[PATCH v3 3/3] elf: tst-dlmopen4: use target specific r_debug_offset function

[Xi Ruoyao]

Fix the test failure on MIPS.
---
 elf/tst-dlmopen4.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/elf/tst-dlmopen4.c b/elf/tst-dlmopen4.c
index d8bcf7e9d5..28e052f199 100644
--- a/elf/tst-dlmopen4.c
+++ b/elf/tst-dlmopen4.c
@@ -25,16 +25,10 @@
 #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)
+#define R_DEBUG_IN_PROCESS
+#include <elfxx-r_debug.h>
 
 static int
 do_test (void)
@@ -44,7 +38,7 @@ 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_offset (d, 0, 0);
       if (debug != NULL)
 	break;
     }
-- 
2.35.0

[PATCH v3 2/3] pldd: use target-specific r_debug_offset function

[Xi Ruoyao]

It allows pldd to work on MIPS.
---
 elf/pldd-xx.c | 34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/elf/pldd-xx.c b/elf/pldd-xx.c
index 1cdfb49c53..5560afe049 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 <elfxx-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 r_debug struct.  */
 	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) d_addr = offset + p[i].p_vaddr + sizeof (EW(Dyn)) * j;
+	    EW(Addr) off = E(r_debug_offset)(&dyn[j], memfd, d_addr);
+	    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;
-- 
2.35.0

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

[H.J. Lu]

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?

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
-- 
2.34.1

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

[Xi Ruoyao]

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