RISC-V: ABI Implementation

This patch contains code that needs to directly know about the RISC-V
ABI, which is specified in a work-in-progress psABI document:

  https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md

This is meant to contain all the RISC-V code that needs to explicitly
name registers or manage in-memory structure layout.  This does not
contain any of the Linux-specific code.

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

        * sysdeps/riscv/__longjmp.S: New file.
        * sysdeps/riscv/backtrace.c: Likewise.
        * sysdeps/riscv/bits/endian.h: Likewise.
        * sysdeps/riscv/bits/setjmp.h: Likewise.
        * sysdeps/riscv/bits/wordsize.h: Likewise.
        * sysdeps/riscv/bsd-_setjmp.c: Likewise.
        * sysdeps/riscv/bsd-setjmp.c: Likewise.
        * sysdeps/riscv/dl-trampoline.S: Likewise.
        * sysdeps/riscv/gccframe.h: Likewise.
        * sysdeps/riscv/jmpbuf-offsets.h: Likewise.
        * sysdeps/riscv/jmpbuf-unwind.h: Likewise.
        * sysdeps/riscv/machine-gmon.h: Likewise.
        * sysdeps/riscv/memusage.h: Likewise.
        * sysdeps/riscv/setjmp.S: Likewise.
        * sysdeps/riscv/sys/asm.h: Likewise.
        * sysdeps/riscv/tls-macros.h: Likewise.

1 files changed, 323 insertions, 0 deletions

diff --git a/sysdeps/riscv/dl-machine.h b/sysdeps/riscv/dl-machine.h
new file mode 100644
index 0000000000..9e3c2925f0
--- /dev/null
+++ b/sysdeps/riscv/dl-machine.h
@@ -0,0 +1,323 @@
+/* Machine-dependent ELF dynamic relocation inline functions.  RISC-V version.
+   Copyright (C) 2011-2018 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/>.  */
+
+#ifndef dl_machine_h
+#define dl_machine_h
+
+#define ELF_MACHINE_NAME "RISC-V"
+
+#include <entry.h>
+#include <elf/elf.h>
+#include <sys/asm.h>
+#include <dl-tls.h>
+
+#ifndef _RTLD_PROLOGUE
+# define _RTLD_PROLOGUE(entry)						\
+	".globl\t" __STRING (entry) "\n\t"				\
+	".type\t" __STRING (entry) ", @function\n"			\
+	__STRING (entry) ":\n\t"
+#endif
+
+#ifndef _RTLD_EPILOGUE
+# define _RTLD_EPILOGUE(entry)						\
+	".size\t" __STRING (entry) ", . - " __STRING (entry) "\n\t"
+#endif
+
+#define ELF_MACHINE_JMP_SLOT R_RISCV_JUMP_SLOT
+
+#define elf_machine_type_class(type)				\
+  ((ELF_RTYPE_CLASS_PLT * ((type) == ELF_MACHINE_JMP_SLOT	\
+     || (__WORDSIZE == 32 && (type) == R_RISCV_TLS_DTPREL32)	\
+     || (__WORDSIZE == 32 && (type) == R_RISCV_TLS_DTPMOD32)	\
+     || (__WORDSIZE == 32 && (type) == R_RISCV_TLS_TPREL32)	\
+     || (__WORDSIZE == 64 && (type) == R_RISCV_TLS_DTPREL64)	\
+     || (__WORDSIZE == 64 && (type) == R_RISCV_TLS_DTPMOD64)	\
+     || (__WORDSIZE == 64 && (type) == R_RISCV_TLS_TPREL64)))	\
+   | (ELF_RTYPE_CLASS_COPY * ((type) == R_RISCV_COPY)))
+
+#define ELF_MACHINE_NO_REL 1
+#define ELF_MACHINE_NO_RELA 0
+
+/* Return nonzero iff ELF header is compatible with the running host.  */
+static inline int __attribute_used__
+elf_machine_matches_host (const ElfW(Ehdr) *ehdr)
+{
+  /* We can only run RISC-V binaries.  */
+  if (ehdr->e_machine != EM_RISCV)
+    return 0;
+
+  /* Ensure the library's floating-point ABI matches that of the running
+     system.  For now we don't support mixing XLEN, so there's no need (or way)
+     to check it matches.  */
+#ifdef __riscv_float_abi_double
+  if ((ehdr->e_flags & EF_RISCV_FLOAT_ABI) != EF_RISCV_FLOAT_ABI_DOUBLE)
+    return 0;
+#else
+  if ((ehdr->e_flags & EF_RISCV_FLOAT_ABI) != EF_RISCV_FLOAT_ABI_SOFT)
+    return 0;
+#endif
+
+  return 1;
+}
+
+/* Return the link-time address of _DYNAMIC.  */
+static inline ElfW(Addr)
+elf_machine_dynamic (void)
+{
+  extern ElfW(Addr) _GLOBAL_OFFSET_TABLE_ __attribute__ ((visibility ("hidden")));
+  return _GLOBAL_OFFSET_TABLE_;
+}
+
+#define STRINGXP(X) __STRING (X)
+#define STRINGXV(X) STRINGV_ (X)
+#define STRINGV_(...) # __VA_ARGS__
+
+/* Return the run-time load address of the shared object.  */
+static inline ElfW(Addr)
+elf_machine_load_address (void)
+{
+  ElfW(Addr) load_addr;
+  asm ("lla %0, _DYNAMIC" : "=r" (load_addr));
+  return load_addr - elf_machine_dynamic ();
+}
+
+/* Initial entry point code for the dynamic linker.
+   The C function `_dl_start' is the real entry point;
+   its return value is the user program's entry point.  */
+
+#define RTLD_START asm (\
+	".text\n\
+	" _RTLD_PROLOGUE (ENTRY_POINT) "\
+	mv a0, sp\n\
+	jal _dl_start\n\
+	# Stash user entry point in s0.\n\
+	mv s0, a0\n\
+	# See if we were run as a command with the executable file\n\
+	# name as an extra leading argument.\n\
+	lw a0, _dl_skip_args\n\
+	# Load the original argument count.\n\
+	" STRINGXP (REG_L) " a1, 0(sp)\n\
+	# Subtract _dl_skip_args from it.\n\
+	sub a1, a1, a0\n\
+	# Adjust the stack pointer to skip _dl_skip_args words.\n\
+	sll a0, a0, " STRINGXP (PTRLOG) "\n\
+	add sp, sp, a0\n\
+	# Save back the modified argument count.\n\
+	" STRINGXP (REG_S) " a1, 0(sp)\n\
+	# Call _dl_init (struct link_map *main_map, int argc, char **argv, char **env) \n\
+	" STRINGXP (REG_L) " a0, _rtld_local\n\
+	add a2, sp, " STRINGXP (SZREG) "\n\
+	sll a3, a1, " STRINGXP (PTRLOG) "\n\
+	add a3, a3, a2\n\
+	add a3, a3, " STRINGXP (SZREG) "\n\
+	# Call the function to run the initializers.\n\
+	jal _dl_init\n\
+	# Pass our finalizer function to _start.\n\
+	lla a0, _dl_fini\n\
+	# Jump to the user entry point.\n\
+	jr s0\n\
+	" _RTLD_EPILOGUE (ENTRY_POINT) "\
+	.previous" \
+);
+
+/* Names of the architecture-specific auditing callback functions.  */
+#define ARCH_LA_PLTENTER riscv_gnu_pltenter
+#define ARCH_LA_PLTEXIT riscv_gnu_pltexit
+
+/* Bias .got.plt entry by the offset requested by the PLT header.  */
+#define elf_machine_plt_value(map, reloc, value) (value)
+
+static inline ElfW(Addr)
+elf_machine_fixup_plt (struct link_map *map, lookup_t t,
+		       const ElfW(Sym) *refsym, const ElfW(Sym) *sym,
+		       const ElfW(Rela) *reloc,
+		       ElfW(Addr) *reloc_addr, ElfW(Addr) value)
+{
+  return *reloc_addr = value;
+}
+
+#endif /* !dl_machine_h */
+
+#ifdef RESOLVE_MAP
+
+/* Perform a relocation described by R_INFO at the location pointed to
+   by RELOC_ADDR.  SYM is the relocation symbol specified by R_INFO and
+   MAP is the object containing the reloc.  */
+
+auto inline void
+__attribute__ ((always_inline))
+elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
+		  const ElfW(Sym) *sym, const struct r_found_version *version,
+		  void *const reloc_addr, int skip_ifunc)
+{
+  ElfW(Addr) r_info = reloc->r_info;
+  const unsigned long int r_type = ELFW (R_TYPE) (r_info);
+  ElfW(Addr) *addr_field = (ElfW(Addr) *) reloc_addr;
+  const ElfW(Sym) *const __attribute__ ((unused)) refsym = sym;
+  struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
+  ElfW(Addr) value = 0;
+  if (sym_map != NULL)
+    value = sym_map->l_addr + sym->st_value + reloc->r_addend;
+
+  switch (r_type)
+    {
+#ifndef RTLD_BOOTSTRAP
+    case __WORDSIZE == 64 ? R_RISCV_TLS_DTPMOD64 : R_RISCV_TLS_DTPMOD32:
+      if (sym_map)
+	*addr_field = sym_map->l_tls_modid;
+      break;
+
+    case __WORDSIZE == 64 ? R_RISCV_TLS_DTPREL64 : R_RISCV_TLS_DTPREL32:
+      if (sym != NULL)
+	*addr_field = TLS_DTPREL_VALUE (sym) + reloc->r_addend;
+      break;
+
+    case __WORDSIZE == 64 ? R_RISCV_TLS_TPREL64 : R_RISCV_TLS_TPREL32:
+      if (sym != NULL)
+	{
+	  CHECK_STATIC_TLS (map, sym_map);
+	  *addr_field = TLS_TPREL_VALUE (sym_map, sym) + reloc->r_addend;
+	}
+      break;
+
+    case R_RISCV_COPY:
+      {
+	if (__glibc_unlikely (sym == NULL))
+	  /* This can happen in trace mode if an object could not be
+	     found.  */
+	  break;
+
+	/* Handle TLS copy relocations.  */
+	if (__glibc_unlikely (ELFW (ST_TYPE) (sym->st_info) == STT_TLS))
+	  {
+	    /* There's nothing to do if the symbol is in .tbss.  */
+	    if (__glibc_likely (sym->st_value >= sym_map->l_tls_initimage_size))
+	      break;
+	    value += (ElfW(Addr)) sym_map->l_tls_initimage - sym_map->l_addr;
+	  }
+
+	size_t size = sym->st_size;
+	if (__glibc_unlikely (sym->st_size != refsym->st_size))
+	  {
+	    const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
+	    if (sym->st_size > refsym->st_size)
+	      size = refsym->st_size;
+	    if (sym->st_size > refsym->st_size || GLRO(dl_verbose))
+	      _dl_error_printf ("\
+  %s: Symbol `%s' has different size in shared object, consider re-linking\n",
+				rtld_progname ?: "<program name unknown>",
+				strtab + refsym->st_name);
+	  }
+
+	memcpy (reloc_addr, (void *)value, size);
+	break;
+      }
+#endif
+
+#if !defined RTLD_BOOTSTRAP || !defined HAVE_Z_COMBRELOC
+    case R_RISCV_RELATIVE:
+      {
+# if !defined RTLD_BOOTSTRAP && !defined HAVE_Z_COMBRELOC
+	/* This is defined in rtld.c, but nowhere in the static libc.a;
+	   make the reference weak so static programs can still link.
+	   This declaration cannot be done when compiling rtld.c
+	   (i.e. #ifdef RTLD_BOOTSTRAP) because rtld.c contains the
+	   common defn for _dl_rtld_map, which is incompatible with a
+	   weak decl in the same file.  */
+#  ifndef SHARED
+	weak_extern (GL(dl_rtld_map));
+#  endif
+	if (map != &GL(dl_rtld_map)) /* Already done in rtld itself.  */
+# endif
+	  *addr_field = map->l_addr + reloc->r_addend;
+      break;
+    }
+#endif
+
+    case R_RISCV_JUMP_SLOT:
+    case __WORDSIZE == 64 ? R_RISCV_64 : R_RISCV_32:
+      *addr_field = value;
+      break;
+
+    case R_RISCV_NONE:
+      break;
+
+    default:
+      _dl_reloc_bad_type (map, r_type, 0);
+      break;
+    }
+}
+
+auto inline void
+__attribute__ ((always_inline))
+elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
+			  void *const reloc_addr)
+{
+  *(ElfW(Addr) *) reloc_addr = l_addr + reloc->r_addend;
+}
+
+auto inline void
+__attribute__ ((always_inline))
+elf_machine_lazy_rel (struct link_map *map, ElfW(Addr) l_addr,
+		      const ElfW(Rela) *reloc, int skip_ifunc)
+{
+  ElfW(Addr) *const reloc_addr = (void *) (l_addr + reloc->r_offset);
+  const unsigned int r_type = ELFW (R_TYPE) (reloc->r_info);
+
+  /* Check for unexpected PLT reloc type.  */
+  if (__glibc_likely (r_type == R_RISCV_JUMP_SLOT))
+    {
+      if (__glibc_unlikely (map->l_mach.plt == 0))
+	{
+	  if (l_addr)
+	    *reloc_addr += l_addr;
+	}
+      else
+	*reloc_addr = map->l_mach.plt;
+    }
+  else
+    _dl_reloc_bad_type (map, r_type, 1);
+}
+
+/* Set up the loaded object described by L so its stub function
+   will jump to the on-demand fixup code __dl_runtime_resolve.  */
+
+auto inline int
+__attribute__ ((always_inline))
+elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
+{
+#ifndef RTLD_BOOTSTRAP
+  /* If using PLTs, fill in the first two entries of .got.plt.  */
+  if (l->l_info[DT_JMPREL])
+    {
+      extern void _dl_runtime_resolve (void) __attribute__ ((visibility ("hidden")));
+      ElfW(Addr) *gotplt = (ElfW(Addr) *) D_PTR (l, l_info[DT_PLTGOT]);
+      /* If a library is prelinked but we have to relocate anyway,
+	 we have to be able to undo the prelinking of .got.plt.
+	 The prelinker saved the address of .plt for us here.  */
+      if (gotplt[1])
+	l->l_mach.plt = gotplt[1] + l->l_addr;
+      gotplt[0] = (ElfW(Addr)) &_dl_runtime_resolve;
+      gotplt[1] = (ElfW(Addr)) l;
+    }
+#endif
+
+  return lazy;
+}
+
+#endif /* RESOLVE_MAP */