exynos4412—連接腳本複習

在u-boot下，定義變量， 

編譯，編譯完後  使用arm-linux-nm arm    沒有去頭的二進制可執行文件

　　都在BSS段，均爲初始化。

打印以後會出算隨機值。

　　目前還處於uboot階段，若是在根文件系統的話，加載器把二進制可執行文件加載到內存，並將BSS段清零。    放在BSS段的變量所對應的空間，在二進制可執行文件中不佔空間。放在Data段才分配空間。

ld --help  

　　

默認連接腳本：arm-linux-ld -verbose

  1 GNU ld (GNU Binutils) 2.20.1.20100303
  2   Supported emulations:
  3    armelf_linux_eabi
  4    armelfb_linux_eabi
  5 using internal linker script:
  6 ==================================================
  7 /* Script for -z combreloc: combine and sort reloc sections */
  8 OUTPUT_FORMAT("elf32-littlearm", "elf32-bigarm",
  9           "elf32-littlearm")　　　　//小端存儲的arm
 10 OUTPUT_ARCH(arm)
 11 ENTRY(_start)
 12 SEARCH_DIR("=/usr/local/lib"); SEARCH_DIR("=/lib"); SEARCH_DIR("=/usr/lib");
 13 SECTIONS
 14 {
 15   /* Read-only sections, merged into text segment: */
 16   PROVIDE (__executable_start = SEGMENT_START("text-segment", 0x00008000)); . = SEGMENT_START("text-segment", 0x00008000) + SIZEOF_HEADERS;
 17   .interp         : { *(.interp) }
 18   .note.gnu.build-id : { *(.note.gnu.build-id) }
 19   .hash           : { *(.hash) }
 20   .gnu.hash       : { *(.gnu.hash) }
 21   .dynsym         : { *(.dynsym) }
 22   .dynstr         : { *(.dynstr) }
 23   .gnu.version    : { *(.gnu.version) }
 24   .gnu.version_d  : { *(.gnu.version_d) }
 25   .gnu.version_r  : { *(.gnu.version_r) }
 26   .rel.dyn        :
 27     {
 28       *(.rel.init)
 29       *(.rel.text .rel.text.* .rel.gnu.linkonce.t.*)
 30       *(.rel.fini)
 31       *(.rel.rodata .rel.rodata.* .rel.gnu.linkonce.r.*)
 32       *(.rel.data.rel.ro* .rel.gnu.linkonce.d.rel.ro.*)
 33       *(.rel.data .rel.data.* .rel.gnu.linkonce.d.*)
 34       *(.rel.tdata .rel.tdata.* .rel.gnu.linkonce.td.*)
 35       *(.rel.tbss .rel.tbss.* .rel.gnu.linkonce.tb.*)
 36       *(.rel.ctors)
 37       *(.rel.dtors)
 38       *(.rel.got)
 39       *(.rel.bss .rel.bss.* .rel.gnu.linkonce.b.*)
 40       PROVIDE_HIDDEN (__rel_iplt_start = .);
 41       *(.rel.iplt)
 42       PROVIDE_HIDDEN (__rel_iplt_end = .);
 43       PROVIDE_HIDDEN (__rela_iplt_start = .);
 44       PROVIDE_HIDDEN (__rela_iplt_end = .);
 45     }
 46   .rela.dyn       :
 47     {
 48       *(.rela.init)
 49       *(.rela.text .rela.text.* .rela.gnu.linkonce.t.*)
 50       *(.rela.fini)
 51       *(.rela.rodata .rela.rodata.* .rela.gnu.linkonce.r.*)
 52       *(.rela.data .rela.data.* .rela.gnu.linkonce.d.*)
 53       *(.rela.tdata .rela.tdata.* .rela.gnu.linkonce.td.*)
 54       *(.rela.tbss .rela.tbss.* .rela.gnu.linkonce.tb.*)
 55       *(.rela.ctors)
 56       *(.rela.dtors)
 57       *(.rela.got)
 58       *(.rela.bss .rela.bss.* .rela.gnu.linkonce.b.*)
 59       PROVIDE_HIDDEN (__rel_iplt_start = .);
 60       PROVIDE_HIDDEN (__rel_iplt_end = .);
 61       PROVIDE_HIDDEN (__rela_iplt_start = .);
 62       *(.rela.iplt)
 63       PROVIDE_HIDDEN (__rela_iplt_end = .);
 64     }
 65   .rel.plt        :
 66     {
 67       *(.rel.plt)
 68     }
 69   .rela.plt       :
 70     {
 71       *(.rela.plt)
 72     }
 73   .init           :
 74   {
 75     KEEP (*(.init))
 76   } =0
 77   .plt            : { *(.plt) }
 78   .iplt           : { *(.iplt) }
 79   .text           :
 80   {
 81     *(.text.unlikely .text.*_unlikely)
 82     *(.text .stub .text.* .gnu.linkonce.t.*)
 83     /* .gnu.warning sections are handled specially by elf32.em.  */
 84     *(.gnu.warning)
 85     *(.glue_7t) *(.glue_7) *(.vfp11_veneer) *(.v4_bx)
 86   } =0
 87   .fini           :
 88   {
 89     KEEP (*(.fini))
 90   } =0
 91   PROVIDE (__etext = .);
 92   PROVIDE (_etext = .);
 93   PROVIDE (etext = .);
 94   .rodata         : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
 95   .rodata1        : { *(.rodata1) }
 96   .ARM.extab   : { *(.ARM.extab* .gnu.linkonce.armextab.*) }
 97    __exidx_start = .;
 98   .ARM.exidx   : { *(.ARM.exidx* .gnu.linkonce.armexidx.*) }
 99    __exidx_end = .;
100   .eh_frame_hdr : { *(.eh_frame_hdr) }
101   .eh_frame       : ONLY_IF_RO { KEEP (*(.eh_frame)) }
102   .gcc_except_table   : ONLY_IF_RO { *(.gcc_except_table .gcc_except_table.*) }
103   /* Adjust the address for the data segment.  We want to adjust up to
104      the same address within the page on the next page up.  */
105   . = ALIGN (CONSTANT (MAXPAGESIZE)) - ((CONSTANT (MAXPAGESIZE) - .) & (CONSTANT (MAXPAGESIZE) - 1)); . = DATA_SEGMENT_ALIGN (CONSTANT (MAXPAGESIZE), CONSTANT (COMMONPAGESIZE));
106   /* Exception handling  */
107   .eh_frame       : ONLY_IF_RW { KEEP (*(.eh_frame)) }
108   .gcc_except_table   : ONLY_IF_RW { *(.gcc_except_table .gcc_except_table.*) }
109   /* Thread Local Storage sections  */
110   .tdata      : { *(.tdata .tdata.* .gnu.linkonce.td.*) }
111   .tbss          : { *(.tbss .tbss.* .gnu.linkonce.tb.*) *(.tcommon) }
112   .preinit_array     :
113   {
114     PROVIDE_HIDDEN (__preinit_array_start = .);
115     KEEP (*(.preinit_array))
116     PROVIDE_HIDDEN (__preinit_array_end = .);
117   }
118   .init_array     :
119   {
120      PROVIDE_HIDDEN (__init_array_start = .);
121      KEEP (*(SORT(.init_array.*)))
122      KEEP (*(.init_array))
123      PROVIDE_HIDDEN (__init_array_end = .);
124   }
125   .fini_array     :
126   {
127     PROVIDE_HIDDEN (__fini_array_start = .);
128     KEEP (*(.fini_array))
129     KEEP (*(SORT(.fini_array.*)))
130     PROVIDE_HIDDEN (__fini_array_end = .);
131   }
132   .ctors          :
133   {
134     /* gcc uses crtbegin.o to find the start of
135        the constructors, so we make sure it is
136        first.  Because this is a wildcard, it
137        doesn't matter if the user does not
138        actually link against crtbegin.o; the
139        linker won't look for a file to match a
140        wildcard.  The wildcard also means that it
141        doesn't matter which directory crtbegin.o
142        is in.  */
143     KEEP (*crtbegin.o(.ctors))
144     KEEP (*crtbegin?.o(.ctors))
145     /* We don't want to include the .ctor section from
146        the crtend.o file until after the sorted ctors.
147        The .ctor section from the crtend file contains the
148        end of ctors marker and it must be last */
149     KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
150     KEEP (*(SORT(.ctors.*)))
151     KEEP (*(.ctors))
152   }
153   .dtors          :
154   {
155     KEEP (*crtbegin.o(.dtors))
156     KEEP (*crtbegin?.o(.dtors))
157     KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
158     KEEP (*(SORT(.dtors.*)))
159     KEEP (*(.dtors))
160   }
161   .jcr            : { KEEP (*(.jcr)) }
162   .data.rel.ro : { *(.data.rel.ro.local* .gnu.linkonce.d.rel.ro.local.*) *(.data.rel.ro* .gnu.linkonce.d.rel.ro.*) }
163   .dynamic        : { *(.dynamic) }
164   . = DATA_SEGMENT_RELRO_END (0, .);
165   .got            : { *(.got.plt) *(.igot.plt) *(.got) *(.igot) }
166   .data           :
167   {
168     PROVIDE (__data_start = .);
169     *(.data .data.* .gnu.linkonce.d.*)
170     SORT(CONSTRUCTORS)
171   }
172   .data1          : { *(.data1) }
173   _edata = .; PROVIDE (edata = .);
174   __bss_start = .;
175   __bss_start__ = .;
176   .bss            :　　　　　　　　//找到了
177   {
178    *(.dynbss)
179    *(.bss .bss.* .gnu.linkonce.b.*)
180    *(COMMON)
181    /* Align here to ensure that the .bss section occupies space up to
182       _end.  Align after .bss to ensure correct alignment even if the
183       .bss section disappears because there are no input sections.
184       FIXME: Why do we need it? When there is no .bss section, we don't
185       pad the .data section.  */
186    . = ALIGN(. != 0 ? 32 / 8 : 1);
187   }
188   _bss_end__ = . ; __bss_end__ = . ;
189   . = ALIGN(32 / 8);
190   . = ALIGN(32 / 8);
191   __end__ = . ;
192   _end = .; PROVIDE (end = .);
193   . = DATA_SEGMENT_END (.);
194   /* Stabs debugging sections.  */
195   .stab          0 : { *(.stab) }
196   .stabstr       0 : { *(.stabstr) }
197   .stab.excl     0 : { *(.stab.excl) }
198   .stab.exclstr  0 : { *(.stab.exclstr) }
199   .stab.index    0 : { *(.stab.index) }
200   .stab.indexstr 0 : { *(.stab.indexstr) }
201   .comment       0 : { *(.comment) }
202   /* DWARF debug sections.
203      Symbols in the DWARF debugging sections are relative to the beginning
204      of the section so we begin them at 0.  */
205   /* DWARF 1 */
206   .debug          0 : { *(.debug) }
207   .line           0 : { *(.line) }
208   /* GNU DWARF 1 extensions */
209   .debug_srcinfo  0 : { *(.debug_srcinfo) }
210   .debug_sfnames  0 : { *(.debug_sfnames) }
211   /* DWARF 1.1 and DWARF 2 */
212   .debug_aranges  0 : { *(.debug_aranges) }
213   .debug_pubnames 0 : { *(.debug_pubnames) }
214   /* DWARF 2 */
215   .debug_info     0 : { *(.debug_info .gnu.linkonce.wi.*) }
216   .debug_abbrev   0 : { *(.debug_abbrev) }
217   .debug_line     0 : { *(.debug_line) }
218   .debug_frame    0 : { *(.debug_frame) }
219   .debug_str      0 : { *(.debug_str) }
220   .debug_loc      0 : { *(.debug_loc) }
221   .debug_macinfo  0 : { *(.debug_macinfo) }
222   /* SGI/MIPS DWARF 2 extensions */
223   .debug_weaknames 0 : { *(.debug_weaknames) }
224   .debug_funcnames 0 : { *(.debug_funcnames) }
225   .debug_typenames 0 : { *(.debug_typenames) }
226   .debug_varnames  0 : { *(.debug_varnames) }
227   /* DWARF 3 */
228   .debug_pubtypes 0 : { *(.debug_pubtypes) }
229   .debug_ranges   0 : { *(.debug_ranges) }
230   .gnu.attributes 0 : { KEEP (*(.gnu.attributes)) }
231   .note.gnu.arm.ident 0 : { KEEP (*(.note.gnu.arm.ident)) }
232   /DISCARD/ : { *(.note.GNU-stack) *(.gnu_debuglink) *(.gnu.lto_*) }
233 }
234 
235 
236 ==================================================

　　如今不使用默認的BSS段，使用本身寫的BSS段。

OUTPUT_FORMAT("elf32-littlearm", "elf32-bigarm",
          "elf32-littlearm")
OUTPUT_ARCH(arm)
ENTRY(_start)
SECTIONS
{
    . = 0x50000000;

    .text : {
        start.o 
        *(.text)
    }
    . = ALIGN(4);

    laomi_data_start = .;
    .laomi : {
        *(.laomi)
    }
    laomi_data_end = .;

    .data : {
        *(.data)
    }
    . = ALIGN(4);
    
    _bss_start = .;
    .bss : {
        *(.bss)
    }
    . = ALIGN(4);
    _bss_end = .;
}

ld.lds

 1 #include <led.h>
 2 #include <key.h>
 3 #include <lib.h>
 4 #include <uart.h>
 5 #include <backlight.h>
 6 #include <lcd.h>
 7 #include <mmu.h>
 8 
 9 u32 *T = (void *)0x60000000;
10 
11 int var0;
12 int var1 = 0;
13 
14 int data = 9527;
15 
16 int glb0 __attribute__ ((unused, section(".jason")))= 7788;
17 int glb1 __attribute__ ((unused, section(".jason")))= 8877;
18 int glb2 __attribute__ ((unused, section(".jason")))= 8866;
19 int glb3 __attribute__ ((unused, section(".jason")))= 8899;
20 
21 extern int jason_data_start;
22 extern int jason_data_end;
23 
24 void entry(void)
25 {
26     int *p = &jason_data_start;
27 
28     while (p < &jason_data_end) {
29         printf("*p = %d\n", *p);
30         p++;
31     }
32 }

entry.c

 1 .PHONE:clean
 2 
 3 TARGET        := arm
 4 BIN          := $(TARGET).bin    
 5 LDADD        := 0x50000000
 6 ASM        := start.o
 7 OBJS        := entry.o lib.o mmu.o
 8 CROSS_COMPILE    := arm-linux-
 9 CC        := $(CROSS_COMPILE)gcc
10 LD        := $(CROSS_COMPILE)ld
11 OBJCOPY        := $(CROSS_COMPILE)objcopy
12 NM        := $(CROSS_COMPILE)nm
13 OBJDUMP        := $(CROSS_COMPILE)objdump
14 
15 all:$(TARGET)
16     $(OBJCOPY) -O binary $< $(BIN)
17 $(TARGET):$(ASM) $(OBJS)
18     $(LD) $(ASM) $(OBJS) -Tld.lds -o $@
19 
20 %.o:%.S
21     $(CC) -c $^
22 %.o:%.c
23     $(CC) -c $^ -Iinclude -Wall -fno-builtin
24 
25 clean:
26     rm -f *.o $(BIN) $(TARGET)
27 
28 
29     

Makefile

而且指定連接腳本，拿到結果