From 8c8510ab2790039e58995ef3a22309582413d3ff Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Thu, 3 Feb 2022 10:58:59 +0100 Subject: [PATCH] Linux: Consolidate auxiliary vector parsing 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 --- elf/dl-support.c | 80 +------------ sysdeps/unix/sysv/linux/alpha/dl-auxv.h | 18 +-- sysdeps/unix/sysv/linux/dl-parse_auxv.h | 61 ++++++++++ sysdeps/unix/sysv/linux/dl-sysdep.c | 111 ++++++------------- sysdeps/unix/sysv/linux/powerpc/dl-auxv.h | 14 +-- sysdeps/unix/sysv/linux/powerpc/dl-support.c | 4 + 6 files changed, 107 insertions(+), 181 deletions(-) create mode 100644 sysdeps/unix/sysv/linux/dl-parse_auxv.h create mode 100644 sysdeps/unix/sysv/linux/powerpc/dl-support.c diff --git a/elf/dl-support.c b/elf/dl-support.c index fb64765537..0fff62064a 100644 --- a/elf/dl-support.c +++ b/elf/dl-support.c @@ -241,93 +241,21 @@ __rtld_lock_define_initialized_recursive (, _dl_load_tls_lock) #ifdef HAVE_AUX_VECTOR +#include + int _dl_clktck; void _dl_aux_init (ElfW(auxv_t) *av) { - int seen = 0; - uid_t uid = 0; - gid_t gid = 0; - #ifdef NEED_DL_SYSINFO /* NB: Avoid RELATIVE relocation in static PIE. */ GL(dl_sysinfo) = DL_SYSINFO_DEFAULT; #endif _dl_auxv = av; - for (; av->a_type != AT_NULL; ++av) - switch (av->a_type) - { - case AT_PAGESZ: - if (av->a_un.a_val != 0) - GLRO(dl_pagesize) = av->a_un.a_val; - break; - case AT_CLKTCK: - GLRO(dl_clktck) = av->a_un.a_val; - break; - case AT_PHDR: - GL(dl_phdr) = (const void *) av->a_un.a_val; - break; - case AT_PHNUM: - GL(dl_phnum) = av->a_un.a_val; - break; - case AT_PLATFORM: - GLRO(dl_platform) = (void *) av->a_un.a_val; - break; - case AT_HWCAP: - GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val; - break; - case AT_HWCAP2: - GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val; - break; - case AT_FPUCW: - GLRO(dl_fpu_control) = av->a_un.a_val; - break; -#ifdef NEED_DL_SYSINFO - case AT_SYSINFO: - GL(dl_sysinfo) = av->a_un.a_val; - break; -#endif -#ifdef NEED_DL_SYSINFO_DSO - case AT_SYSINFO_EHDR: - GL(dl_sysinfo_dso) = (void *) av->a_un.a_val; - break; -#endif - case AT_UID: - uid ^= av->a_un.a_val; - seen |= 1; - break; - case AT_EUID: - uid ^= av->a_un.a_val; - seen |= 2; - break; - case AT_GID: - gid ^= av->a_un.a_val; - seen |= 4; - break; - case AT_EGID: - gid ^= av->a_un.a_val; - seen |= 8; - break; - case AT_SECURE: - seen = -1; - __libc_enable_secure = av->a_un.a_val; - __libc_enable_secure_decided = 1; - break; - case AT_RANDOM: - _dl_random = (void *) av->a_un.a_val; - break; - case AT_MINSIGSTKSZ: - _dl_minsigstacksize = av->a_un.a_val; - break; - DL_PLATFORM_AUXV - } - if (seen == 0xf) - { - __libc_enable_secure = uid != 0 || gid != 0; - __libc_enable_secure_decided = 1; - } + dl_parse_auxv_t auxv_values = { 0, }; + _dl_parse_auxv (av, auxv_values); } #endif diff --git a/sysdeps/unix/sysv/linux/alpha/dl-auxv.h b/sysdeps/unix/sysv/linux/alpha/dl-auxv.h index 81d90da095..fcec743239 100644 --- a/sysdeps/unix/sysv/linux/alpha/dl-auxv.h +++ b/sysdeps/unix/sysv/linux/alpha/dl-auxv.h @@ -20,16 +20,8 @@ extern long __libc_alpha_cache_shape[4]; -#define DL_PLATFORM_AUXV \ - case AT_L1I_CACHESHAPE: \ - __libc_alpha_cache_shape[0] = av->a_un.a_val; \ - break; \ - case AT_L1D_CACHESHAPE: \ - __libc_alpha_cache_shape[1] = av->a_un.a_val; \ - break; \ - case AT_L2_CACHESHAPE: \ - __libc_alpha_cache_shape[2] = av->a_un.a_val; \ - break; \ - case AT_L3_CACHESHAPE: \ - __libc_alpha_cache_shape[3] = av->a_un.a_val; \ - break; +#define DL_PLATFORM_AUXV \ + __libc_alpha_cache_shape[0] = auxv_values[AT_L1I_CACHESHAPE]; \ + __libc_alpha_cache_shape[1] = auxv_values[AT_L1D_CACHESHAPE]; \ + __libc_alpha_cache_shape[2] = auxv_values[AT_L2_CACHESHAPE]; \ + __libc_alpha_cache_shape[3] = auxv_values[AT_L3_CACHESHAPE]; diff --git a/sysdeps/unix/sysv/linux/dl-parse_auxv.h b/sysdeps/unix/sysv/linux/dl-parse_auxv.h new file mode 100644 index 0000000000..b3d82f6994 --- /dev/null +++ b/sysdeps/unix/sysv/linux/dl-parse_auxv.h @@ -0,0 +1,61 @@ +/* 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 + . */ + +#include +#include +#include +#include +#include + +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 +} diff --git a/sysdeps/unix/sysv/linux/dl-sysdep.c b/sysdeps/unix/sysv/linux/dl-sysdep.c index 2bda76b820..71cf1968b5 100644 --- a/sysdeps/unix/sysv/linux/dl-sysdep.c +++ b/sysdeps/unix/sysv/linux/dl-sysdep.c @@ -21,13 +21,12 @@ #include #include #include +#include #include #include #include -#include #include #include -#include #include #include #include @@ -63,24 +62,24 @@ void *_dl_random attribute_relro = NULL; # define DL_STACK_END(cookie) ((void *) (cookie)) #endif -ElfW(Addr) -_dl_sysdep_start (void **start_argptr, - void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum, - ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv)) +/* Arguments passed to dl_main. */ +struct dl_main_arguments { - const ElfW(Phdr) *phdr = NULL; - ElfW(Word) phnum = 0; + const ElfW(Phdr) *phdr; + ElfW(Word) phnum; ElfW(Addr) user_entry; - ElfW(auxv_t) *av; -#ifdef NEED_DL_SYSINFO - uintptr_t new_sysinfo = 0; -#endif +}; - __libc_stack_end = DL_STACK_END (start_argptr); +/* Separate function, so that dl_main can be called without the large + array on the stack. */ +static void +_dl_sysdep_parse_arguments (void **start_argptr, + struct dl_main_arguments *args) +{ _dl_argc = (intptr_t) *start_argptr; _dl_argv = (char **) (start_argptr + 1); /* Necessary aliasing violation. */ _environ = _dl_argv + _dl_argc + 1; - for (char **tmp = _environ + 1; ; ++tmp) + for (char **tmp = _environ; ; ++tmp) if (*tmp == NULL) { /* Another necessary aliasing violation. */ @@ -88,75 +87,26 @@ _dl_sysdep_start (void **start_argptr, break; } - user_entry = (ElfW(Addr)) ENTRY_POINT; - GLRO(dl_platform) = NULL; /* Default to nothing known about the platform. */ + dl_parse_auxv_t auxv_values = { 0, }; + _dl_parse_auxv (GLRO(dl_auxv), auxv_values); - /* NB: Default to a constant CONSTANT_MINSIGSTKSZ. */ - _Static_assert (__builtin_constant_p (CONSTANT_MINSIGSTKSZ), - "CONSTANT_MINSIGSTKSZ is constant"); - GLRO(dl_minsigstacksize) = CONSTANT_MINSIGSTKSZ; + args->phdr = (const ElfW(Phdr) *) auxv_values[AT_PHDR]; + args->phnum = auxv_values[AT_PHNUM]; + args->user_entry = auxv_values[AT_ENTRY]; +} - for (av = GLRO(dl_auxv); av->a_type != AT_NULL; av++) - switch (av->a_type) - { - case AT_PHDR: - phdr = (void *) av->a_un.a_val; - break; - case AT_PHNUM: - phnum = av->a_un.a_val; - break; - case AT_PAGESZ: - GLRO(dl_pagesize) = av->a_un.a_val; - break; - case AT_ENTRY: - user_entry = av->a_un.a_val; - break; - case AT_SECURE: - __libc_enable_secure = av->a_un.a_val; - break; - case AT_PLATFORM: - GLRO(dl_platform) = (void *) av->a_un.a_val; - break; - case AT_HWCAP: - GLRO(dl_hwcap) = (unsigned long int) av->a_un.a_val; - break; - case AT_HWCAP2: - GLRO(dl_hwcap2) = (unsigned long int) av->a_un.a_val; - break; - case AT_CLKTCK: - GLRO(dl_clktck) = av->a_un.a_val; - break; - case AT_FPUCW: - GLRO(dl_fpu_control) = av->a_un.a_val; - break; -#ifdef NEED_DL_SYSINFO - case AT_SYSINFO: - new_sysinfo = av->a_un.a_val; - break; -#endif - case AT_SYSINFO_EHDR: - GLRO(dl_sysinfo_dso) = (void *) av->a_un.a_val; - break; - case AT_RANDOM: - _dl_random = (void *) av->a_un.a_val; - break; - case AT_MINSIGSTKSZ: - GLRO(dl_minsigstacksize) = av->a_un.a_val; - break; - DL_PLATFORM_AUXV - } +ElfW(Addr) +_dl_sysdep_start (void **start_argptr, + void (*dl_main) (const ElfW(Phdr) *phdr, ElfW(Word) phnum, + ElfW(Addr) *user_entry, ElfW(auxv_t) *auxv)) +{ + __libc_stack_end = DL_STACK_END (start_argptr); + + struct dl_main_arguments dl_main_args; + _dl_sysdep_parse_arguments (start_argptr, &dl_main_args); dl_hwcap_check (); -#ifdef NEED_DL_SYSINFO - if (new_sysinfo != 0) - { - /* Only set the sysinfo value if we also have the vsyscall DSO. */ - if (GLRO(dl_sysinfo_dso) != 0) - GLRO(dl_sysinfo) = new_sysinfo; - } -#endif - __tunables_init (_environ); /* Initialize DSO sorting algorithm after tunables. */ @@ -187,8 +137,9 @@ _dl_sysdep_start (void **start_argptr, if (__builtin_expect (__libc_enable_secure, 0)) __libc_check_standard_fds (); - (*dl_main) (phdr, phnum, &user_entry, GLRO(dl_auxv)); - return user_entry; + (*dl_main) (dl_main_args.phdr, dl_main_args.phnum, + &dl_main_args.user_entry, GLRO(dl_auxv)); + return dl_main_args.user_entry; } void diff --git a/sysdeps/unix/sysv/linux/powerpc/dl-auxv.h b/sysdeps/unix/sysv/linux/powerpc/dl-auxv.h index 594371940a..ce2281cf11 100644 --- a/sysdeps/unix/sysv/linux/powerpc/dl-auxv.h +++ b/sysdeps/unix/sysv/linux/powerpc/dl-auxv.h @@ -16,15 +16,5 @@ License along with the GNU C Library; if not, see . */ -#include - -#if IS_IN (libc) && !defined SHARED -int GLRO(dl_cache_line_size); -#endif - -/* Scan the Aux Vector for the "Data Cache Block Size" entry and assign it - to dl_cache_line_size. */ -#define DL_PLATFORM_AUXV \ - case AT_DCACHEBSIZE: \ - GLRO(dl_cache_line_size) = av->a_un.a_val; \ - break; +#define DL_PLATFORM_AUXV \ + GLRO(dl_cache_line_size) = auxv_values[AT_DCACHEBSIZE]; diff --git a/sysdeps/unix/sysv/linux/powerpc/dl-support.c b/sysdeps/unix/sysv/linux/powerpc/dl-support.c new file mode 100644 index 0000000000..abe68a7049 --- /dev/null +++ b/sysdeps/unix/sysv/linux/powerpc/dl-support.c @@ -0,0 +1,4 @@ +#include + +/* Populated from the auxiliary vector. */ +int _dl_cache_line_size;