ARC: startup and dynamic linking code

Code for C runtime startup and dynamic loading including PLT layout.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 344 insertions, 0 deletions

diff --git a/sysdeps/arc/dl-machine.h b/sysdeps/arc/dl-machine.h
new file mode 100644
index 0000000000..e47f19905f
--- /dev/null
+++ b/sysdeps/arc/dl-machine.h
@@ -0,0 +1,344 @@
+/* Machine-dependent ELF dynamic relocation inline functions.  ARC version.
+   Copyright (C) 2020 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 dl_machine_h
+#define dl_machine_h
+
+#define ELF_MACHINE_NAME "arc"
+
+#include <entry.h>
+
+#ifndef ENTRY_POINT
+# error ENTRY_POINT needs to be defined for ARC
+#endif
+
+#include <string.h>
+#include <link.h>
+#include <dl-tls.h>
+
+/* Dynamic Linking ABI for ARCv2 ISA.
+
+                        PLT
+          --------------------------------	<---- DT_PLTGOT
+          |  ld r11, [pcl, off-to-GOT[1] |  0
+          |                              |  4
+   plt0   |  ld r10, [pcl, off-to-GOT[2] |  8
+          |                              | 12
+          |  j [r10]                     | 16
+          --------------------------------
+          |    Base address of GOT       | 20
+          --------------------------------
+          |  ld r12, [pcl, off-to-GOT[3] | 24
+   plt1   |                              |
+          |  j.d    [r12]                | 32
+          |  mov    r12, pcl             | 36
+          --------------------------------
+          |                              | 40
+          ~                              ~
+          ~                              ~
+          |                              |
+          --------------------------------
+
+               .got
+          --------------
+          |    [0]     |
+          |    ...     |  Runtime address for data symbols
+          |    [n]     |
+          --------------
+
+            .got.plt
+          --------------
+          |    [0]     |  Build address of .dynamic
+          --------------
+          |    [1]     |  Module info - setup by ld.so
+          --------------
+          |    [2]     |  resolver entry point
+          --------------
+          |    [3]     |
+          |    ...     |  Runtime address for function symbols
+          |    [f]     |
+          --------------
+
+   For ARCompact, the PLT is 12 bytes due to short instructions
+
+          --------------------------------
+          |  ld r12, [pcl, off-to-GOT[3] | 24   (12 bytes each)
+   plt1   |                              |
+          |  j_s.d  [r12]                | 32
+          |  mov_s  r12, pcl             | 34
+          --------------------------------
+          |                              | 36  */
+
+/* Return nonzero iff ELF header is compatible with the running host.  */
+static inline int
+elf_machine_matches_host (const Elf32_Ehdr *ehdr)
+{
+  return (ehdr->e_machine == EM_ARCV2		 /* ARC HS.  */
+	  || ehdr->e_machine == EM_ARC_COMPACT); /* ARC 700.  */
+}
+
+/* Get build time address of .dynamic as setup in GOT[0]
+   This is called very early in _dl_start so it has not been relocated to
+   runtime value.  */
+static inline ElfW(Addr)
+elf_machine_dynamic (void)
+{
+  extern const ElfW(Addr) _GLOBAL_OFFSET_TABLE_[] attribute_hidden;
+  return _GLOBAL_OFFSET_TABLE_[0];
+}
+
+
+/* Return the run-time load address of the shared object.  */
+static inline ElfW(Addr)
+elf_machine_load_address (void)
+{
+  ElfW(Addr) build_addr, run_addr;
+
+  /* For build address, below generates
+     ld  r0, [pcl, _GLOBAL_OFFSET_TABLE_@pcl].  */
+  build_addr = elf_machine_dynamic ();
+  __asm__ ("add %0, pcl, _DYNAMIC@pcl	\n" : "=r" (run_addr));
+
+  return run_addr - build_addr;
+}
+
+/* Set up the loaded object described by L so its unrelocated PLT
+   entries will jump to the on-demand fixup code in dl-runtime.c.  */
+
+static inline int
+__attribute__ ((always_inline))
+elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
+{
+  extern void _dl_runtime_resolve (Elf32_Word);
+
+  if (l->l_info[DT_JMPREL] && lazy)
+    {
+      /* On ARC DT_PLTGOT point to .plt whose 5th word (after the PLT header)
+         contains the address of .got.  */
+      ElfW(Addr) *plt_base = (ElfW(Addr) *) D_PTR (l, l_info[DT_PLTGOT]);
+      ElfW(Addr) *got = (ElfW(Addr) *) (plt_base[5] + l->l_addr);
+
+      got[1] = (ElfW(Addr)) l;	/* Identify this shared object.  */
+
+      /* This function will get called to fix up the GOT entry indicated by
+	 the offset on the stack, and then jump to the resolved address.  */
+      got[2] = (ElfW(Addr)) &_dl_runtime_resolve;
+    }
+
+  return lazy;
+}
+
+/* What this code does:
+    -ldso starts execution here when kernel returns from execve
+    -calls into generic ldso entry point _dl_start
+    -optionally adjusts argc for executable if exec passed as cmd
+    -calls into app main with address of finaliser.  */
+
+#define RTLD_START asm ("\
+.text									\n\
+.globl __start								\n\
+.type __start, @function						\n\
+__start:								\n\
+	/* (1). bootstrap ld.so.  */					\n\
+	bl.d    _dl_start                                       	\n\
+	mov_s   r0, sp  /* pass ptr to aux vector tbl.    */    	\n\
+	mov r13, r0	/* safekeep app elf entry point.  */		\n\
+									\n\
+	/* (2). If ldso ran with executable as arg.       */		\n\
+	/*      skip the extra args calc by dl_start.     */		\n\
+	ld_s    r1, [sp]       /* orig argc.  */			\n\
+	ld      r12, [pcl, _dl_skip_args@pcl]                   	\n\
+	breq	r12, 0, 1f						\n\
+									\n\
+	add2    sp, sp, r12 /* discard argv entries from stack.  */	\n\
+	sub_s   r1, r1, r12 /* adjusted argc on stack.  */      	\n\
+	st_s    r1, [sp]                                        	\n\
+	add	r2, sp, 4						\n\
+	/* intermediate LD for ST emcoding limitations.  */		\n\
+	ld	r3, [pcl, _dl_argv@gotpc]    				\n\
+	st	r2, [r3]						\n\
+1:									\n\
+	/* (3). call preinit stuff.  */					\n\
+	ld	r0, [pcl, _rtld_local@pcl]				\n\
+	add	r2, sp, 4	; argv					\n\
+	add2	r3, r2, r1						\n\
+	add	r3, r3, 4	; env					\n\
+	bl	_dl_init@plt						\n\
+									\n\
+	/* (4) call app elf entry point.  */				\n\
+	add     r0, pcl, _dl_fini@pcl					\n\
+	j	[r13]							\n\
+									\n\
+	.size  __start,.-__start                               		\n\
+	.previous                                               	\n\
+");
+
+/* ELF_RTYPE_CLASS_PLT iff TYPE describes relocation of a PLT entry, so
+   PLT entries should not be allowed to define the value.
+   ELF_RTYPE_CLASS_NOCOPY iff TYPE should not be allowed to resolve to one
+   of the main executable's symbols, as for a COPY reloc.  */
+#define elf_machine_type_class(type)				\
+  ((((type) == R_ARC_JUMP_SLOT					\
+     || (type) == R_ARC_TLS_DTPMOD				\
+     || (type) == R_ARC_TLS_DTPOFF				\
+     || (type) == R_ARC_TLS_TPOFF) * ELF_RTYPE_CLASS_PLT)	\
+   | (((type) == R_ARC_COPY) * ELF_RTYPE_CLASS_COPY))
+
+/* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
+#define ELF_MACHINE_JMP_SLOT  R_ARC_JUMP_SLOT
+
+/* ARC uses Elf32_Rela relocations.  */
+#define ELF_MACHINE_NO_REL 1
+#define ELF_MACHINE_NO_RELA 0
+
+/* Fixup a PLT entry to bounce directly to the function at 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 Elf32_Rela *reloc,
+		       ElfW(Addr) *reloc_addr, ElfW(Addr) value)
+{
+  return *reloc_addr = value;
+}
+
+/* Return the final value of a plt relocation.  */
+static inline ElfW(Addr)
+elf_machine_plt_value (struct link_map *map, const Elf32_Rela *reloc,
+                       ElfW(Addr) value)
+{
+  return value;
+}
+
+/* Names of the architecture-specific auditing callback functions.  */
+#define ARCH_LA_PLTENTER arc_gnu_pltenter
+#define ARCH_LA_PLTEXIT arc_gnu_pltexit
+
+#endif /* dl_machine_h */
+
+#ifdef RESOLVE_MAP
+
+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_arg, int skip_ifunc)
+{
+  ElfW(Addr) *const reloc_addr = reloc_addr_arg;
+  const unsigned int r_type = ELF32_R_TYPE (reloc->r_info);
+
+  if (__glibc_unlikely (r_type == R_ARC_RELATIVE))
+    *reloc_addr += map->l_addr;
+  else if (__glibc_unlikely (r_type == R_ARC_NONE))
+    return;
+  else
+    {
+      const ElfW(Sym) *const refsym = sym;
+      struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
+      ElfW(Addr) value = SYMBOL_ADDRESS (sym_map, sym, true);
+
+      switch (r_type)
+        {
+        case R_ARC_COPY:
+          if (__glibc_unlikely (sym == NULL))
+            /* This can happen in trace mode if an object could not be
+               found.  */
+            break;
+
+          size_t size = sym->st_size;
+          if (__glibc_unlikely (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_arg, (void *) value, size);
+          break;
+
+        case R_ARC_GLOB_DAT:
+        case R_ARC_JUMP_SLOT:
+            *reloc_addr = value;
+          break;
+
+        case R_ARC_TLS_DTPMOD:
+          if (sym_map != NULL)
+            /* Get the information from the link map returned by the
+               resolv function.  */
+            *reloc_addr = sym_map->l_tls_modid;
+          break;
+
+        case R_ARC_TLS_DTPOFF:
+          if (sym != NULL)
+            /* Offset set by the linker in the GOT entry would be overwritten
+               by dynamic loader instead of added to the symbol location.
+               Other target have the same approach on DTPOFF relocs.  */
+            *reloc_addr += sym->st_value;
+          break;
+
+        case R_ARC_TLS_TPOFF:
+          if (sym != NULL)
+            {
+              CHECK_STATIC_TLS (map, sym_map);
+              *reloc_addr = sym_map->l_tls_offset + sym->st_value + reloc->r_addend;
+            }
+          break;
+
+        case R_ARC_32:
+          *reloc_addr += value + reloc->r_addend;
+          break;
+
+        case R_ARC_PC32:
+          *reloc_addr += value + reloc->r_addend - (unsigned long int) reloc_addr;
+          break;
+
+        default:
+          _dl_reloc_bad_type (map, r_type, 0);
+          break;
+        }
+    }
+}
+
+inline void
+__attribute__ ((always_inline))
+elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc,
+                           void *const reloc_addr_arg)
+{
+  ElfW(Addr) *const reloc_addr = reloc_addr_arg;
+  *reloc_addr += l_addr;
+}
+
+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);
+
+  if (ELF32_R_TYPE (reloc->r_info) == R_ARC_JUMP_SLOT)
+    *reloc_addr += l_addr;
+  else
+    _dl_reloc_bad_type (map, ELF32_R_TYPE (reloc->r_info), 1);
+}
+
+#endif /* RESOLVE_MAP */