Ping. I need a review of this glibc patch from a RISC-V architecture maintainer:
<https://sourceware.org/ml/libc-alpha/2019-09/msg00506.html> I believe this is another artifact needlessly copied over from the MIPS port of glibc, but this one we can fix easily. Thanks, Florian * Florian Weimer: > _dl_var_init is used to patch the read-only data section after > relocation. Several architectures use this to update > GLRO(page_size) with the correct value for the static dlopen case, > where _rtld_global_ro has not been initialized by the dynamic > loader. > > RISC-V does not need this. The RISC-V Instruction Set Manual, > Volume II: Privileged Architecture, Document Version > 20190608-Priv-MSU-Ratified says this: > > After much deliberation, we have settled on a conventional > page size of 4 KiB for both RV32 and RV64. We expect this > decision to ease the porting of low-level runtime software > and device drivers. The TLB reach problem is ameliorated by > transparent superpage support in modern operating systems > [2]. Additionally, multi-level TLB hierarchies are quite > inexpensive relative to the multi-level cache hierarchies > whose address space they map. > > [2] Juan Navarro, Sitaram Iyer, Peter Druschel, and > Alan Cox. Practical, transparent operating system support > for superpages. SIGOPS Oper. Syst. Rev., 36(SI):89–104, > December 2002. > > This means that the initialization of > _rtld_global_ro._dl_page_size in elf/rtld.c with EXEC_PAGESIZE > is sufficient for RISC-V. > > 2019-09-30 Florian Weimer <fwei...@redhat.com> > > riscv: Remove support for variable page sizes. > * sysdeps/unix/sysv/linux/riscv/Makefile [$(subdir) == elf] > (sysdep_routines): Do not add dl-static. > * sysdeps/unix/sysv/linux/riscv/dl-static.c: Remove file. > * sysdeps/unix/sysv/linux/riscv/ldsodefs.h: Likewise. > > diff --git a/sysdeps/unix/sysv/linux/riscv/Makefile > b/sysdeps/unix/sysv/linux/riscv/Makefile > index b47858769f..b7ad31885c 100644 > --- a/sysdeps/unix/sysv/linux/riscv/Makefile > +++ b/sysdeps/unix/sysv/linux/riscv/Makefile > @@ -1,9 +1,5 @@ > ifeq ($(subdir),elf) > sysdep_routines += dl-vdso > -ifeq ($(build-shared),yes) > -# This is needed for DSO loading from static binaries. > -sysdep-dl-routines += dl-static > -endif > endif > > ifeq ($(subdir),misc) > diff --git a/sysdeps/unix/sysv/linux/riscv/dl-static.c > b/sysdeps/unix/sysv/linux/riscv/dl-static.c > deleted file mode 100644 > index e52612a267..0000000000 > --- a/sysdeps/unix/sysv/linux/riscv/dl-static.c > +++ /dev/null > @@ -1,84 +0,0 @@ > -/* Variable initialization. RISC-V version > - Copyright (C) 2001-2019 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 <ldsodefs.h> > - > -#ifdef SHARED > - > -void > -_dl_var_init (void *array[]) > -{ > - /* It has to match "variables" below. */ > - enum > - { > - DL_PAGESIZE = 0 > - }; > - > - GLRO(dl_pagesize) = *((size_t *) array[DL_PAGESIZE]); > -} > - > -#else > - > -static void *variables[] = > -{ > - &GLRO(dl_pagesize) > -}; > - > -static void > -_dl_unprotect_relro (struct link_map *l) > -{ > - ElfW(Addr) start = ((l->l_addr + l->l_relro_addr) > - & ~(GLRO(dl_pagesize) - 1)); > - ElfW(Addr) end = ((l->l_addr + l->l_relro_addr + l->l_relro_size) > - & ~(GLRO(dl_pagesize) - 1)); > - > - if (start != end) > - __mprotect ((void *) start, end - start, PROT_READ | PROT_WRITE); > -} > - > -void > -_dl_static_init (struct link_map *l) > -{ > - struct link_map *rtld_map = l; > - struct r_scope_elem **scope; > - const ElfW(Sym) *ref = NULL; > - lookup_t loadbase; > - void (*f) (void *[]); > - size_t i; > - > - loadbase = _dl_lookup_symbol_x ("_dl_var_init", l, &ref, l->l_local_scope, > - NULL, 0, 1, NULL); > - > - for (scope = l->l_local_scope; *scope != NULL; scope++) > - for (i = 0; i < (*scope)->r_nlist; i++) > - if ((*scope)->r_list[i] == loadbase) > - { > - rtld_map = (*scope)->r_list[i]; > - break; > - } > - > - if (ref != NULL) > - { > - f = (void (*) (void *[])) DL_SYMBOL_ADDRESS (loadbase, ref); > - _dl_unprotect_relro (rtld_map); > - f (variables); > - _dl_protect_relro (rtld_map); > - } > -} > - > -#endif > diff --git a/sysdeps/unix/sysv/linux/riscv/ldsodefs.h > b/sysdeps/unix/sysv/linux/riscv/ldsodefs.h > deleted file mode 100644 > index a46e676752..0000000000 > --- a/sysdeps/unix/sysv/linux/riscv/ldsodefs.h > +++ /dev/null > @@ -1,32 +0,0 @@ > -/* RISC-V dynamic linker data structures for loaded ELF shared objects. > - Copyright (C) 2001-2019 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/>. */ > - > -#ifndef _LDSODEFS_H > - > -/* Get the real definitions. */ > -#include_next <ldsodefs.h> > - > -/* Now define our stuff. */ > - > -/* We need special support to initialize DSO loaded for statically linked > - binaries. */ > -extern void _dl_static_init (struct link_map *map); > -#undef DL_STATIC_INIT > -#define DL_STATIC_INIT(map) _dl_static_init (map) > - > -#endif /* ldsodefs.h */