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Linux: Consolidate auxiliary vector parsing

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And optimize it slightly.

The large switch statement in _dl_sysdep_start can be replaced with
a large array.  This reduces source code and binary size.  On
i686-linux-gnu:

Before:

   text	   data	    bss	    dec	    hex	filename
   7791	     12	      0	   7803	   1e7b	elf/dl-sysdep.os

After:

   text	   data	    bss	    dec	    hex	filename
   7135	     12	      0	   7147	   1beb	elf/dl-sysdep.os

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Florian Weimer
2022-02-03 10:58:59 +01:00
parent f19fc997a5
commit 8c8510ab27
6 changed files with 107 additions and 181 deletions
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61
sysdeps/unix/sysv/linux/dl-parse_auxv.h Normal file
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/* Parse the Linux auxiliary vector.
Copyright (C) 1995-2022 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/>. */
#include <elf.h>
#include <entry.h>
#include <fpu_control.h>
#include <ldsodefs.h>
#include <link.h>
typedef ElfW(Addr) dl_parse_auxv_t[AT_MINSIGSTKSZ + 1];
/* Copy the auxiliary vector into AUX_VALUES and set up GLRO
variables. */
static inline
void _dl_parse_auxv (ElfW(auxv_t) *av, dl_parse_auxv_t auxv_values)
{
auxv_values[AT_ENTRY] = (ElfW(Addr)) ENTRY_POINT;
auxv_values[AT_PAGESZ] = EXEC_PAGESIZE;
auxv_values[AT_FPUCW] = _FPU_DEFAULT;
/* NB: Default to a constant CONSTANT_MINSIGSTKSZ. */
_Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ),
"CONSTANT_MINSIGSTKSZ is constant");
auxv_values[AT_MINSIGSTKSZ] = CONSTANT_MINSIGSTKSZ;
for (; av->a_type != AT_NULL; av++)
if (av->a_type <= AT_MINSIGSTKSZ)
auxv_values[av->a_type] = av->a_un.a_val;
GLRO(dl_pagesize) = auxv_values[AT_PAGESZ];
__libc_enable_secure = auxv_values[AT_SECURE];
GLRO(dl_platform) = (void *) auxv_values[AT_PLATFORM];
GLRO(dl_hwcap) = auxv_values[AT_HWCAP];
GLRO(dl_hwcap2) = auxv_values[AT_HWCAP2];
GLRO(dl_clktck) = auxv_values[AT_CLKTCK];
GLRO(dl_fpu_control) = auxv_values[AT_FPUCW];
_dl_random = (void *) auxv_values[AT_RANDOM];
GLRO(dl_minsigstacksize) = auxv_values[AT_MINSIGSTKSZ];
GLRO(dl_sysinfo_dso) = (void *) auxv_values[AT_SYSINFO_EHDR];
#ifdef NEED_DL_SYSINFO
if (GLRO(dl_sysinfo_dso) != NULL)
GLRO(dl_sysinfo) = auxv_values[AT_SYSINFO];
#endif
DL_PLATFORM_AUXV
}