simple ELF loader

diff --git a/loader/loader.c b/loader/loader.c
new file mode 100644 (file)
index 0000000..6a829ff
--- /dev/null
+++ b/loader/loader.c
@@ -0,0 +1,156 @@
+// vim:shiftwidth=2:expandtab
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <elf.h>
+#include <sys/mman.h>
+
+#define CHECK_(val, fail_operator, expect, err_msg) \
+  if (val fail_operator expect) { \
+    fprintf(stderr, err_msg ", exiting (%d)\n", (int)(long)val); \
+    return 1; \
+  }
+
+#define CHECK_EQ(val, expect, err_msg) \
+  CHECK_(val, !=, expect, err_msg)
+
+#define CHECK_NE(val, expect, err_msg) \
+  CHECK_(val, ==, expect, err_msg)
+
+#define HDR_CHECK_EQ(field, expect, err_msg) \
+  CHECK_(hdr.field, !=, expect, err_msg)
+
+#define HDR_CHECK_NE(field, expect, err_msg) \
+  CHECK_(hdr.field, ==, expect, err_msg)
+
+#define FAIL_PERROR(msg) { \
+  perror(msg); \
+  return 1; \
+}
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof(x[0]))
+
+typedef struct {
+  unsigned long start;
+  unsigned long end;
+} maps_range;
+
+static int is_range_used(maps_range *maps, int map_cnt, unsigned long start, unsigned long end)
+{
+  int i;
+  for (i = 0; i < map_cnt; i++) {
+    if (maps[i].end <= start)
+      continue;
+    if (end <= maps[i].start)
+      continue;
+
+    return i + 1;
+  }
+
+  return 0;
+}
+
+extern char **environ;
+extern void do_entry(Elf32_Addr entry, void *stack_frame, int stack_frame_size, void *exitf);
+
+int main(int argc, char *argv[])
+{
+  Elf32_Ehdr hdr;
+  Elf32_Phdr *phdr;
+  FILE *fi;
+  maps_range maps[16];
+  int map_cnt;
+  int i, ret;
+  long stack_frame[5];
+
+  if (argc != 2) {
+    fprintf(stderr, "usage: %s <program>\n", argv[0]);
+    return 1;
+  }
+
+  fi = fopen("/proc/self/maps", "r");
+  CHECK_NE(fi, NULL, "fopen maps");
+
+  for (i = 0; i < ARRAY_SIZE(maps); i++) {
+    ret = fscanf(fi, "%lx-%lx %*s %*s %*s %*s %*s\n", &maps[i].start, &maps[i].end);
+    if (ret == 0)
+      break;
+    CHECK_EQ(ret, 2, "maps parse error");
+  }
+  fclose(fi);
+  map_cnt = i;
+  CHECK_NE(map_cnt, 0, "no maps");
+  CHECK_NE(map_cnt, ARRAY_SIZE(maps), "too many maps");
+
+  fi = fopen(argv[1], "rb");
+  if (fi == NULL)
+    FAIL_PERROR("fopen");
+
+  if (fread(&hdr, 1, sizeof(hdr), fi) != sizeof(hdr))
+    FAIL_PERROR("too small or");
+
+  if (memcmp(hdr.e_ident, ELFMAG "\x01\x01", SELFMAG + 2) != 0) {
+    fprintf(stderr, "not 32bit LE ELF?\n");
+    return 1;
+  }
+
+  HDR_CHECK_EQ(e_type, ET_EXEC, "not executable");
+//  HDR_CHECK_EQ(e_machine, EM_ARM, "not ARM");
+  HDR_CHECK_EQ(e_phentsize, sizeof(Elf32_Phdr), "bad PH entry size");
+  HDR_CHECK_NE(e_phnum, 0, "no PH entries");
+
+  phdr = malloc(hdr.e_phnum * hdr.e_phentsize);
+  CHECK_NE(phdr, NULL, "OOM");
+
+  if (fread(phdr, hdr.e_phentsize, hdr.e_phnum, fi) != hdr.e_phnum)
+    FAIL_PERROR("too small or");
+
+  for (i = 0; i < hdr.e_phnum; i++) {
+    Elf32_Addr end_addr = phdr[i].p_vaddr + phdr[i].p_memsz;
+    Elf32_Addr align;
+    void *ptr, *map_ptr;
+
+    if (phdr[i].p_type == PT_NOTE)
+      continue;
+    if (phdr[i].p_type != PT_LOAD) {
+      fprintf(stderr, "skipping section %d\n", phdr[i].p_type);
+      continue;
+    }
+
+    ret = is_range_used(maps, map_cnt, phdr[i].p_vaddr, end_addr);
+    if (ret) {
+      fprintf(stderr, "segment %d (%08x-%08x) hits %08lx-%08lx in maps\n",
+        i, phdr[i].p_vaddr, end_addr, maps[ret - 1].start, maps[ret - 1].end);
+      return 1;
+    }
+
+    printf("load %d %08x-%08x from %08x\n", phdr[i].p_type,
+      phdr[i].p_vaddr, end_addr, phdr[i].p_offset);
+
+    align = phdr[i].p_vaddr & 0xfff;
+    map_ptr = (void *)(phdr[i].p_vaddr - align);
+    ptr = mmap(map_ptr, phdr[i].p_memsz + align, PROT_READ|PROT_WRITE|PROT_EXEC,
+      MAP_FIXED|MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+    if (ptr == MAP_FAILED || ptr != map_ptr)
+      FAIL_PERROR("mmap");
+
+    if (phdr[i].p_filesz > 0) {
+      if (fseek(fi, phdr[i].p_offset, SEEK_SET) != 0)
+        FAIL_PERROR("fseek");
+      if (fread((char *)ptr + align, 1, phdr[i].p_filesz, fi) != phdr[i].p_filesz)
+        FAIL_PERROR("too small or");
+    }
+  }
+
+  stack_frame[0] = 1; // argc
+  stack_frame[1] = (long)argv[1];
+  stack_frame[2] = 0;
+  stack_frame[3] = (long)environ;
+  stack_frame[4] = 0;
+
+  printf("entering %08x\n", hdr.e_entry);
+  do_entry(hdr.e_entry, stack_frame, 5, NULL);
+
+  return 0;
+}
+

diff --git a/loader/loader_arm.s b/loader/loader_arm.s
new file mode 100644 (file)
index 0000000..eec1c75
--- /dev/null
+++ b/loader/loader_arm.s
@@ -0,0 +1,17 @@
+.text
+
+/* void do_entry(Elf32_Addr entry, void *stack_frame, int stack_frame_size, void *exitf); */
+
+.globl do_entry
+do_entry:
+    sub   sp, sp, r2, lsl #2
+    mov   r4, sp
+    mov   r5, r0
+0:
+    ldr   r0, [r1], #4
+    subs  r2, r2, #1
+    str   r0, [r4], #4
+    bgt   0b
+
+    mov   r0, r3
+    bx    r5

diff --git a/loader/loader_ia32.s b/loader/loader_ia32.s
new file mode 100644 (file)
index 0000000..8284491
--- /dev/null
+++ b/loader/loader_ia32.s
@@ -0,0 +1,26 @@
+.text
+
+/* void do_entry(Elf32_Addr entry, void *stack_frame, int stack_frame_size, void *exitf); */
+
+.globl do_entry
+do_entry:
+       movl    4(%esp), %ebx
+       movl    8(%esp), %esi
+       movl    12(%esp), %eax
+       movl    16(%esp), %edx
+
+       movl    %eax, %ecx
+       shll    $2, %ecx
+       subl    %ecx, %esp
+
+       /* copy stack frame */
+       movl    %esp, %edi
+0:
+       movl    (%esi), %ecx
+       movl    %ecx, (%edi)
+       addl    $4, %esi
+       addl    $4, %edi
+       subl    $1, %eax
+       jg      0b
+
+       jmp     *%ebx

diff --git a/loader/script_arm.lds b/loader/script_arm.lds
new file mode 100644 (file)
index 0000000..fdc6921
--- /dev/null
+++ b/loader/script_arm.lds
@@ -0,0 +1,194 @@
+/* Script for -z combreloc: combine and sort reloc sections */
+OUTPUT_FORMAT("elf32-littlearm")
+OUTPUT_ARCH(arm)
+ENTRY(_start)
+SEARCH_DIR("=/usr/local/lib"); SEARCH_DIR("=/lib"); SEARCH_DIR("=/usr/lib");
+SECTIONS
+{
+  mybase = 0x70000000; /* 0x00008000 */
+  /* Read-only sections, merged into text segment: */
+  PROVIDE (__executable_start = mybase);
+  . = mybase + SIZEOF_HEADERS;
+  .interp         : { *(.interp) }
+  .hash           : { *(.hash) }
+  .dynsym         : { *(.dynsym) }
+  .dynstr         : { *(.dynstr) }
+  .gnu.version    : { *(.gnu.version) }
+  .gnu.version_d  : { *(.gnu.version_d) }
+  .gnu.version_r  : { *(.gnu.version_r) }
+  .rel.dyn        :
+    {
+      *(.rel.init)
+      *(.rel.text .rel.text.* .rel.gnu.linkonce.t.*)
+      *(.rel.fini)
+      *(.rel.rodata .rel.rodata.* .rel.gnu.linkonce.r.*)
+      *(.rel.data.rel.ro*)
+      *(.rel.data .rel.data.* .rel.gnu.linkonce.d.*)
+      *(.rel.tdata .rel.tdata.* .rel.gnu.linkonce.td.*)
+      *(.rel.tbss .rel.tbss.* .rel.gnu.linkonce.tb.*)
+      *(.rel.ctors)
+      *(.rel.dtors)
+      *(.rel.got)
+      *(.rel.bss .rel.bss.* .rel.gnu.linkonce.b.*)
+    }
+  .rela.dyn       :
+    {
+      *(.rela.init)
+      *(.rela.text .rela.text.* .rela.gnu.linkonce.t.*)
+      *(.rela.fini)
+      *(.rela.rodata .rela.rodata.* .rela.gnu.linkonce.r.*)
+      *(.rela.data .rela.data.* .rela.gnu.linkonce.d.*)
+      *(.rela.tdata .rela.tdata.* .rela.gnu.linkonce.td.*)
+      *(.rela.tbss .rela.tbss.* .rela.gnu.linkonce.tb.*)
+      *(.rela.ctors)
+      *(.rela.dtors)
+      *(.rela.got)
+      *(.rela.bss .rela.bss.* .rela.gnu.linkonce.b.*)
+    }
+  .rel.plt        : { *(.rel.plt) }
+  .rela.plt       : { *(.rela.plt) }
+  .init           :
+  {
+    KEEP (*(.init))
+  } =0
+  .plt            : { *(.plt) }
+  .text           :
+  {
+    *(.text .stub .text.* .gnu.linkonce.t.*)
+    KEEP (*(.text.*personality*))
+    /* .gnu.warning sections are handled specially by elf32.em.  */
+    *(.gnu.warning)
+    *(.glue_7t) *(.glue_7)
+  } =0
+  .fini           :
+  {
+    KEEP (*(.fini))
+  } =0
+  PROVIDE (__etext = .);
+  PROVIDE (_etext = .);
+  PROVIDE (etext = .);
+  .rodata         : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
+  .rodata1        : { *(.rodata1) }
+  .eh_frame_hdr : { *(.eh_frame_hdr) }
+  .eh_frame       : ONLY_IF_RO { KEEP (*(.eh_frame)) }
+  .gcc_except_table   : ONLY_IF_RO { KEEP (*(.gcc_except_table)) *(.gcc_except_table.*) }
+  /* Adjust the address for the data segment.  We want to adjust up to
+     the same address within the page on the next page up.  */
+  . = ALIGN (0x8000) - ((0x8000 - .) & (0x8000 - 1)); . = DATA_SEGMENT_ALIGN (0x8000, 0x1000);
+  /* Exception handling  */
+  .eh_frame       : ONLY_IF_RW { KEEP (*(.eh_frame)) }
+  .gcc_except_table   : ONLY_IF_RW { KEEP (*(.gcc_except_table)) *(.gcc_except_table.*) }
+  /* Thread Local Storage sections  */
+  .tdata         : { *(.tdata .tdata.* .gnu.linkonce.td.*) }
+  .tbss                  : { *(.tbss .tbss.* .gnu.linkonce.tb.*) *(.tcommon) }
+  /* Ensure the __preinit_array_start label is properly aligned.  We
+     could instead move the label definition inside the section, but
+     the linker would then create the section even if it turns out to
+     be empty, which isn't pretty.  */
+  . = ALIGN(32 / 8);
+  PROVIDE (__preinit_array_start = .);
+  .preinit_array     : { KEEP (*(.preinit_array)) }
+  PROVIDE (__preinit_array_end = .);
+  PROVIDE (__init_array_start = .);
+  .init_array     : { KEEP (*(.init_array)) }
+  PROVIDE (__init_array_end = .);
+  PROVIDE (__fini_array_start = .);
+  .fini_array     : { KEEP (*(.fini_array)) }
+  PROVIDE (__fini_array_end = .);
+  .ctors          :
+  {
+    /* gcc uses crtbegin.o to find the start of
+       the constructors, so we make sure it is
+       first.  Because this is a wildcard, it
+       doesn't matter if the user does not
+       actually link against crtbegin.o; the
+       linker won't look for a file to match a
+       wildcard.  The wildcard also means that it
+       doesn't matter which directory crtbegin.o
+       is in.  */
+    KEEP (*crtbegin*.o(.ctors))
+    /* We don't want to include the .ctor section from
+       from the crtend.o file until after the sorted ctors.
+       The .ctor section from the crtend file contains the
+       end of ctors marker and it must be last */
+    KEEP (*(EXCLUDE_FILE (*crtend*.o ) .ctors))
+    KEEP (*(SORT(.ctors.*)))
+    KEEP (*(.ctors))
+  }
+  .dtors          :
+  {
+    KEEP (*crtbegin*.o(.dtors))
+    KEEP (*(EXCLUDE_FILE (*crtend*.o ) .dtors))
+    KEEP (*(SORT(.dtors.*)))
+    KEEP (*(.dtors))
+  }
+  .jcr            : { KEEP (*(.jcr)) }
+  .data.rel.ro : { *(.data.rel.ro.local) *(.data.rel.ro*) }
+  .dynamic        : { *(.dynamic) }
+  . = DATA_SEGMENT_RELRO_END (0, .);
+  .got            : { *(.got.plt) *(.got) }
+  .data           :
+  {
+    __data_start = . ;
+    *(.data .data.* .gnu.linkonce.d.*)
+    KEEP (*(.gnu.linkonce.d.*personality*))
+    SORT(CONSTRUCTORS)
+  }
+  .data1          : { *(.data1) }
+  _edata = .;
+  PROVIDE (edata = .);
+  __bss_start = .;
+  __bss_start__ = .;
+  .bss            :
+  {
+   *(.dynbss)
+   *(.bss .bss.* .gnu.linkonce.b.*)
+   *(COMMON)
+   /* Align here to ensure that the .bss section occupies space up to
+      _end.  Align after .bss to ensure correct alignment even if the
+      .bss section disappears because there are no input sections.  */
+   . = ALIGN(32 / 8);
+  }
+  . = ALIGN(32 / 8);
+  _end = .;
+  _bss_end__ = . ; __bss_end__ = . ; __end__ = . ;
+  PROVIDE (end = .);
+  . = DATA_SEGMENT_END (.);
+  /* Stabs debugging sections.  */
+  .stab          0 : { *(.stab) }
+  .stabstr       0 : { *(.stabstr) }
+  .stab.excl     0 : { *(.stab.excl) }
+  .stab.exclstr  0 : { *(.stab.exclstr) }
+  .stab.index    0 : { *(.stab.index) }
+  .stab.indexstr 0 : { *(.stab.indexstr) }
+  .comment       0 : { *(.comment) }
+  /* DWARF debug sections.
+     Symbols in the DWARF debugging sections are relative to the beginning
+     of the section so we begin them at 0.  */
+  /* DWARF 1 */
+  .debug          0 : { *(.debug) }
+  .line           0 : { *(.line) }
+  /* GNU DWARF 1 extensions */
+  .debug_srcinfo  0 : { *(.debug_srcinfo) }
+  .debug_sfnames  0 : { *(.debug_sfnames) }
+  /* DWARF 1.1 and DWARF 2 */
+  .debug_aranges  0 : { *(.debug_aranges) }
+  .debug_pubnames 0 : { *(.debug_pubnames) }
+  /* DWARF 2 */
+  .debug_info     0 : { *(.debug_info .gnu.linkonce.wi.*) }
+  .debug_abbrev   0 : { *(.debug_abbrev) }
+  .debug_line     0 : { *(.debug_line) }
+  .debug_frame    0 : { *(.debug_frame) }
+  .debug_str      0 : { *(.debug_str) }
+  .debug_loc      0 : { *(.debug_loc) }
+  .debug_macinfo  0 : { *(.debug_macinfo) }
+  /* SGI/MIPS DWARF 2 extensions */
+  .debug_weaknames 0 : { *(.debug_weaknames) }
+  .debug_funcnames 0 : { *(.debug_funcnames) }
+  .debug_typenames 0 : { *(.debug_typenames) }
+  .debug_varnames  0 : { *(.debug_varnames) }
+  .note.gnu.arm.ident 0 : { KEEP (*(.note.gnu.arm.ident)) }
+  /DISCARD/ : { *(.note.GNU-stack) }
+}
+
+

diff --git a/loader/script_ia32.lds b/loader/script_ia32.lds
new file mode 100644 (file)
index 0000000..4573e5a
--- /dev/null
+++ b/loader/script_ia32.lds
@@ -0,0 +1,195 @@
+/* Script for -z combreloc: combine and sort reloc sections */
+OUTPUT_FORMAT("elf32-i386")
+OUTPUT_ARCH(i386)
+ENTRY(_start)
+SEARCH_DIR("/usr/local/lib32"); SEARCH_DIR("/lib32"); SEARCH_DIR("/usr/lib32");
+SECTIONS
+{
+  mybase = 0x70000000; /* 0x08048000 */
+  /* Read-only sections, merged into text segment: */
+  PROVIDE (__executable_start = SEGMENT_START("text-segment", mybase));
+  . = SEGMENT_START("text-segment", mybase) + SIZEOF_HEADERS;
+  .interp         : { *(.interp) }
+  .note.gnu.build-id : { *(.note.gnu.build-id) }
+  .hash           : { *(.hash) }
+  .gnu.hash       : { *(.gnu.hash) }
+  .dynsym         : { *(.dynsym) }
+  .dynstr         : { *(.dynstr) }
+  .gnu.version    : { *(.gnu.version) }
+  .gnu.version_d  : { *(.gnu.version_d) }
+  .gnu.version_r  : { *(.gnu.version_r) }
+  .rel.dyn        :
+    {
+      *(.rel.init)
+      *(.rel.text .rel.text.* .rel.gnu.linkonce.t.*)
+      *(.rel.fini)
+      *(.rel.rodata .rel.rodata.* .rel.gnu.linkonce.r.*)
+      *(.rel.data.rel.ro* .rel.gnu.linkonce.d.rel.ro.*)
+      *(.rel.data .rel.data.* .rel.gnu.linkonce.d.*)
+      *(.rel.tdata .rel.tdata.* .rel.gnu.linkonce.td.*)
+      *(.rel.tbss .rel.tbss.* .rel.gnu.linkonce.tb.*)
+      *(.rel.ctors)
+      *(.rel.dtors)
+      *(.rel.got)
+      *(.rel.bss .rel.bss.* .rel.gnu.linkonce.b.*)
+      *(.rel.ifunc)
+    }
+  .rel.plt        :
+    {
+      *(.rel.plt)
+      PROVIDE_HIDDEN (__rel_iplt_start = .);
+      *(.rel.iplt)
+      PROVIDE_HIDDEN (__rel_iplt_end = .);
+    }
+  .init           :
+  {
+    KEEP (*(.init))
+  } =0x90909090
+  .plt            : { *(.plt) *(.iplt) }
+  .text           :
+  {
+    *(.text.unlikely .text.*_unlikely)
+    *(.text .stub .text.* .gnu.linkonce.t.*)
+    /* .gnu.warning sections are handled specially by elf32.em.  */
+    *(.gnu.warning)
+  } =0x90909090
+  .fini           :
+  {
+    KEEP (*(.fini))
+  } =0x90909090
+  PROVIDE (__etext = .);
+  PROVIDE (_etext = .);
+  PROVIDE (etext = .);
+  .rodata         : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
+  .rodata1        : { *(.rodata1) }
+  .eh_frame_hdr : { *(.eh_frame_hdr) }
+  .eh_frame       : ONLY_IF_RO { KEEP (*(.eh_frame)) }
+  .gcc_except_table   : ONLY_IF_RO { *(.gcc_except_table .gcc_except_table.*) }
+  /* Adjust the address for the data segment.  We want to adjust up to
+     the same address within the page on the next page up.  */
+  . = ALIGN (CONSTANT (MAXPAGESIZE)) - ((CONSTANT (MAXPAGESIZE) - .) & (CONSTANT (MAXPAGESIZE) - 1)); . = DATA_SEGMENT_ALIGN (CONSTANT (MAXPAGESIZE), CONSTANT (COMMONPAGESIZE));
+  /* Exception handling  */
+  .eh_frame       : ONLY_IF_RW { KEEP (*(.eh_frame)) }
+  .gcc_except_table   : ONLY_IF_RW { *(.gcc_except_table .gcc_except_table.*) }
+  /* Thread Local Storage sections  */
+  .tdata         : { *(.tdata .tdata.* .gnu.linkonce.td.*) }
+  .tbss                  : { *(.tbss .tbss.* .gnu.linkonce.tb.*) *(.tcommon) }
+  .preinit_array     :
+  {
+    PROVIDE_HIDDEN (__preinit_array_start = .);
+    KEEP (*(.preinit_array))
+    PROVIDE_HIDDEN (__preinit_array_end = .);
+  }
+  .init_array     :
+  {
+     PROVIDE_HIDDEN (__init_array_start = .);
+     KEEP (*(SORT(.init_array.*)))
+     KEEP (*(.init_array))
+     PROVIDE_HIDDEN (__init_array_end = .);
+  }
+  .fini_array     :
+  {
+    PROVIDE_HIDDEN (__fini_array_start = .);
+    KEEP (*(.fini_array))
+    KEEP (*(SORT(.fini_array.*)))
+    PROVIDE_HIDDEN (__fini_array_end = .);
+  }
+  .ctors          :
+  {
+    /* gcc uses crtbegin.o to find the start of
+       the constructors, so we make sure it is
+       first.  Because this is a wildcard, it
+       doesn't matter if the user does not
+       actually link against crtbegin.o; the
+       linker won't look for a file to match a
+       wildcard.  The wildcard also means that it
+       doesn't matter which directory crtbegin.o
+       is in.  */
+    KEEP (*crtbegin.o(.ctors))
+    KEEP (*crtbegin?.o(.ctors))
+    /* We don't want to include the .ctor section from
+       the crtend.o file until after the sorted ctors.
+       The .ctor section from the crtend file contains the
+       end of ctors marker and it must be last */
+    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
+    KEEP (*(SORT(.ctors.*)))
+    KEEP (*(.ctors))
+  }
+  .dtors          :
+  {
+    KEEP (*crtbegin.o(.dtors))
+    KEEP (*crtbegin?.o(.dtors))
+    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
+    KEEP (*(SORT(.dtors.*)))
+    KEEP (*(.dtors))
+  }
+  .jcr            : { KEEP (*(.jcr)) }
+  .data.rel.ro : { *(.data.rel.ro.local* .gnu.linkonce.d.rel.ro.local.*) *(.data.rel.ro* .gnu.linkonce.d.rel.ro.*) }
+  .dynamic        : { *(.dynamic) }
+  .got            : { *(.got) *(.igot) }
+  . = DATA_SEGMENT_RELRO_END (12, .);
+  .got.plt        : { *(.got.plt)  *(.igot.plt) }
+  .data           :
+  {
+    *(.data .data.* .gnu.linkonce.d.*)
+    SORT(CONSTRUCTORS)
+  }
+  .data1          : { *(.data1) }
+  _edata = .; PROVIDE (edata = .);
+  __bss_start = .;
+  .bss            :
+  {
+   *(.dynbss)
+   *(.bss .bss.* .gnu.linkonce.b.*)
+   *(COMMON)
+   /* Align here to ensure that the .bss section occupies space up to
+      _end.  Align after .bss to ensure correct alignment even if the
+      .bss section disappears because there are no input sections.
+      FIXME: Why do we need it? When there is no .bss section, we don't
+      pad the .data section.  */
+   . = ALIGN(. != 0 ? 32 / 8 : 1);
+  }
+  . = ALIGN(32 / 8);
+  . = ALIGN(32 / 8);
+  _end = .; PROVIDE (end = .);
+  . = DATA_SEGMENT_END (.);
+  /* Stabs debugging sections.  */
+  .stab          0 : { *(.stab) }
+  .stabstr       0 : { *(.stabstr) }
+  .stab.excl     0 : { *(.stab.excl) }
+  .stab.exclstr  0 : { *(.stab.exclstr) }
+  .stab.index    0 : { *(.stab.index) }
+  .stab.indexstr 0 : { *(.stab.indexstr) }
+  .comment       0 : { *(.comment) }
+  /* DWARF debug sections.
+     Symbols in the DWARF debugging sections are relative to the beginning
+     of the section so we begin them at 0.  */
+  /* DWARF 1 */
+  .debug          0 : { *(.debug) }
+  .line           0 : { *(.line) }
+  /* GNU DWARF 1 extensions */
+  .debug_srcinfo  0 : { *(.debug_srcinfo) }
+  .debug_sfnames  0 : { *(.debug_sfnames) }
+  /* DWARF 1.1 and DWARF 2 */
+  .debug_aranges  0 : { *(.debug_aranges) }
+  .debug_pubnames 0 : { *(.debug_pubnames) }
+  /* DWARF 2 */
+  .debug_info     0 : { *(.debug_info .gnu.linkonce.wi.*) }
+  .debug_abbrev   0 : { *(.debug_abbrev) }
+  .debug_line     0 : { *(.debug_line) }
+  .debug_frame    0 : { *(.debug_frame) }
+  .debug_str      0 : { *(.debug_str) }
+  .debug_loc      0 : { *(.debug_loc) }
+  .debug_macinfo  0 : { *(.debug_macinfo) }
+  /* SGI/MIPS DWARF 2 extensions */
+  .debug_weaknames 0 : { *(.debug_weaknames) }
+  .debug_funcnames 0 : { *(.debug_funcnames) }
+  .debug_typenames 0 : { *(.debug_typenames) }
+  .debug_varnames  0 : { *(.debug_varnames) }
+  /* DWARF 3 */
+  .debug_pubtypes 0 : { *(.debug_pubtypes) }
+  .debug_ranges   0 : { *(.debug_ranges) }
+  .gnu.attributes 0 : { KEEP (*(.gnu.attributes)) }
+  /DISCARD/ : { *(.note.GNU-stack) *(.gnu_debuglink) *(.gnu.lto_*) }
+}
+