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Re: PING^1: [PATCH 1/2] Mark ld.so internal mmap functions hidden in ld.so
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Wed, 6 Jan 2016 16:34:15 -0200
- Subject: Re: PING^1: [PATCH 1/2] Mark ld.so internal mmap functions hidden in ld.so
- Authentication-results: sourceware.org; auth=none
- References: <CAMe9rOrx6tSCzMvGeoidvFSsHEUwB_5bWy1mQPT9bVxvsbvdeQ at mail dot gmail dot com>
Checking of the dissassemble ld.so for i686 I see no PLT stub
being generated for mmap or it being called through it:
$ objdump -d elf/ld.so
[...]
5cdc: 89 04 24 mov %eax,(%esp)
5cdf: e8 fc 49 01 00 call 1a6e0 <__mmap>
[...]
Also regarding mmap I see that generated assembly generated is
not different without the patch. I do see that for the part 02
of the patch for the __libc_{open,close} with the patch a
call to __x86.get_pc_thunk.bx is removed (which is the intention
of the patch).
Am I missing something here?
On 14-12-2015 12:10, H.J. Lu wrote:
> Ping.
>
> On Mon, Dec 7, 2015 at 11:00 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> Since ld.so internal mmap functions are only used internally in ld.so,
>> they can be made hidden. Don't hide __mmap on Hurd, since __mmap in
>> ld.so will be preempted by the one in libc.so after bootstrap.
>>
>> [BZ #19122]
>> * include/sys/mman.h [IS_IN (rtld)]: Include <dl-mman.h>.
>> * sysdeps/generic/dl-mman.h: New file.
>> * sysdeps/mach/hurd/dl-mman.h: Likewise.
>> ---
>> include/sys/mman.h | 4 ++++
>> sysdeps/generic/dl-mman.h | 22 ++++++++++++++++++++++
>> sysdeps/mach/hurd/dl-mman.h | 23 +++++++++++++++++++++++
>> 3 files changed, 49 insertions(+)
>> create mode 100644 sysdeps/generic/dl-mman.h
>> create mode 100644 sysdeps/mach/hurd/dl-mman.h
>>
>> diff --git a/include/sys/mman.h b/include/sys/mman.h
>> index fd125ec..7026f69 100644
>> --- a/include/sys/mman.h
>> +++ b/include/sys/mman.h
>> @@ -16,6 +16,10 @@ libc_hidden_proto (__madvise)
>> /* This one is Linux specific. */
>> extern void *__mremap (void *__addr, size_t __old_len,
>> size_t __new_len, int __flags, ...);
>> +
>> +# if IS_IN (rtld)
>> +# include <dl-mman.h>
>> +# endif
>> #endif
>>
>> #endif
>> diff --git a/sysdeps/generic/dl-mman.h b/sysdeps/generic/dl-mman.h
>> new file mode 100644
>> index 0000000..9087218
>> --- /dev/null
>> +++ b/sysdeps/generic/dl-mman.h
>> @@ -0,0 +1,22 @@
>> +/* Functions with hidden attribute internal to ld.so, which are declared
>> + in include/sys/mman.h. Generic version.
>> + Copyright (C) 2015 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
>> + <http://www.gnu.org/licenses/>. */
>> +
>> +extern __typeof (__mmap) __mmap attribute_hidden;
>> +extern __typeof (__mprotect) __mprotect attribute_hidden;
>> +extern __typeof (__munmap) __munmap attribute_hidden;
>> diff --git a/sysdeps/mach/hurd/dl-mman.h b/sysdeps/mach/hurd/dl-mman.h
>> new file mode 100644
>> index 0000000..f9d7996
>> --- /dev/null
>> +++ b/sysdeps/mach/hurd/dl-mman.h
>> @@ -0,0 +1,23 @@
>> +/* Functions with hidden attribute internal to ld.so, which are declared
>> + in include/sys/mman.h. Hurd version.
>> + Copyright (C) 2015 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
>> + <http://www.gnu.org/licenses/>. */
>> +
>> +/* Can't hide __mmap on Hurd, since __mmap in ld.so will be preempted by
>> + the one in libc.so after bootstrap. */
>> +extern __typeof (__mprotect) __mprotect attribute_hidden;
>> +extern __typeof (__munmap) __munmap attribute_hidden;
>> --
>> 2.5.0
>>
>
>
>