RISC-V: Linux ABI

Linux-specific code that is required for maintaining ABI compatibility.
This doesn't contain the actual system call interface, that is split out
in order to avoid having a patch that's too big.

2018-01-29  Palmer Dabbelt  <palmer@sifive.com>

        * sysdeps/riscv/nptl/pthread-offsets.h: New file.
        * sysdeps/riscv/nptl/pthreaddef.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/bits/fcntl.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/bits/mman.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/bits/sigcontext.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/dl-cache.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/flush-icache.c: Likewise.
        * sysdeps/unix/sysv/linux/riscv/getcontext.S: Likewise.
        * sysdeps/unix/sysv/linux/riscv/init-first.c: Likewise.
        * sysdeps/unix/sysv/linux/riscv/libc-vdso.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/makecontext.c: Likewise.
        * sysdeps/unix/sysv/linux/riscv/readelflib.c: Likewise.
        * sysdeps/unix/sysv/linux/riscv/register-dump.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/setcontext.S: Likewise.
        * sysdeps/unix/sysv/linux/riscv/sigcontextinfo.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/swapcontext.S: Likewise.
        * sysdeps/unix/sysv/linux/riscv/sys/cachectl.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/sys/procfs.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/sys/ucontext.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/sys/user.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/ucontext-macros.h: Likewise.
        * sysdeps/unix/sysv/linux/riscv/ucontext_i.sym: Likewise.

sysdeps/unix/sysv/linux/riscv/readelflib.c

@@ -0,0 +1,96 @@
+/* Support for reading ELF files.
+   Copyright (C) 1999-2018 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
+   <http://www.gnu.org/licenses/>.  */
+
+
+int process_elf32_file (const char *file_name, const char *lib, int *flag,
+			unsigned int *osversion, char **soname,
+			void *file_contents, size_t file_length);
+int process_elf64_file (const char *file_name, const char *lib, int *flag,
+			unsigned int *osversion, char **soname,
+			void *file_contents, size_t file_length);
+
+/* The ELF flags supported by our current glibc port:
+   - EF_RISCV_FLOAT_ABI: We support the soft and double ABIs.
+   - EF_RISCV_RVC: While the Linux ABI mandates the presence of the C
+     extension, we can still support libraries compiled without that extension
+     so we just ignore this flag.
+   - EF_RISCV_RVE: glibc (and Linux) don't support RV32E based systems.
+   - EF_RISCV_TSO: The TSO extension isn't supported, as doing so would require
+     some mechanism to ensure that the TSO extension is enabled which doesn't
+     currently exist.  */
+#define SUPPORTED_ELF_FLAGS (EF_RISCV_FLOAT_ABI | EF_RISCV_RVC)
+
+/* Returns 0 if everything is ok, != 0 in case of error.  */
+int
+process_elf_file (const char *file_name, const char *lib, int *flag,
+		  unsigned int *osversion, char **soname, void *file_contents,
+		  size_t file_length)
+{
+  ElfW(Ehdr) *elf_header = (ElfW(Ehdr) *) file_contents;
+  Elf32_Ehdr *elf32_header = (Elf32_Ehdr *) elf_header;
+  int ret;
+  long flags;
+
+  /* RISC-V libraries are always libc.so.6+.  */
+  *flag = FLAG_ELF_LIBC6;
+
+  if (elf_header->e_ident [EI_CLASS] == ELFCLASS32)
+    {
+      ret = process_elf32_file (file_name, lib, flag, osversion, soname,
+				file_contents, file_length);
+      flags = elf32_header->e_flags;
+    }
+  else
+    {
+      ret = process_elf64_file (file_name, lib, flag, osversion, soname,
+				file_contents, file_length);
+      flags = elf32_header->e_flags;
+    }
+
+  /* RISC-V linkers encode the floating point ABI as part of the ELF headers.  */
+  switch (flags & EF_RISCV_FLOAT_ABI)
+    {
+      case EF_RISCV_FLOAT_ABI_SOFT:
+        *flag |= FLAG_RISCV_FLOAT_ABI_SOFT;
+	break;
+      case EF_RISCV_FLOAT_ABI_DOUBLE:
+        *flag |= FLAG_RISCV_FLOAT_ABI_DOUBLE;
+	break;
+      default:
+        return 1;
+    }
+
+  /* If there are any other ELF flags set then glibc doesn't support this
+     library.  */
+  if (flags & ~SUPPORTED_ELF_FLAGS)
+    return 1;
+
+  return ret;
+}
+
+#undef __ELF_NATIVE_CLASS
+#undef process_elf_file
+#define process_elf_file process_elf32_file
+#define __ELF_NATIVE_CLASS 32
+#include "elf/readelflib.c"
+
+#undef __ELF_NATIVE_CLASS
+#undef process_elf_file
+#define process_elf_file process_elf64_file
+#define __ELF_NATIVE_CLASS 64
+#include "elf/readelflib.c"