[PATCH] riscv: Remove support for variable page sizes

[Florian Weimer <fweimer at redhat dot com>]

[NB: I could use some help with testing here.]

_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  <fweimer@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 */