LGTM; I believe you are right on both counts that this was borrowed from MIPS and that we do not need this for RISC-V.
On Mon, Oct 7, 2019 at 5:21 PM Florian Weimer <fwei...@redhat.com> wrote: > 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 */ >
