Union + int within assembly and C Language

Just talk about one question:

_ Switch_data in head_common.s:

. Long init_thread_union + thread_start_sp

Init_thread_union cannot be redirected using ctags, and there is no init_thread_union in the Link script. Using grep search, we found that this is the name of the federated variable in arch/Unicore/kernel/init_task.c3 (no jump, there is no link to the script, that is, the Assembly file of the file is not like the C file, the header file needs to be included, and the extern external declaration is added ). So we added a constant value to the variable name of the consortium in C in head_common.s. This is because the name of a consortium variable in C is treated as a label, just like the label in the Assembly file. Therefore, a constant value can be added to the name of a consortium variable in C. I wrote a very small test (the program has no meaning, in the form !!!) :

Sramboot. s file:

1 # include "regdef. H"

2. Set noreorder

3. Text

4. globl start

5 start:

6. Set noat

7 la at, Value

8 LW A1, 4 ()

9 Jal my_add

10 NOP

11 add A2, A0, A1

12 SW A2, 8 ()

 

Call. s file:

1 # include "regdef. H"

2 /*

3 extern Union thread_union init_thread_union;

4 */

5. Set noreorder

6. Text

7. globl my_add, Value

8 my_add:

9 Add A1, A1, 3

10 Jal start_kernel

11 J Ra

12 add A1, A1, 4

13. Data

14 value:

15. Word 10, 20, 0

16. Long init_thread_union + 8

 

Union. c file:

1 # DEFINE _ init_task_data _ attribute _ (_ Section _ (". Data. init_task ")))

2 struct thread_info

3 {

4 int ID;

5 Int time;

6 };

7 Union thread_union

8 {

9 struct thread_info;

10 unsigned long stack [16];

11 };

12

13 Union thread_union init_thread_union _ init_task_data =

14 {

15 {. ID = 9,. Time = 8 ,},

16 };

17 void start_kernel (void)

18 {

19 while (1 );

20}

 

Makefile

1 cross_compile = mipsel-Linux-

2 cc = $ (cross_compile) GCC

3 As = $ (cross_compile)

4 LD = $ (cross_compile) LD

5 objdump = $ (cross_compile) objdump

6 objcopy = $ (cross_compile) objcopy

7 textbase = #-ttext

8 Database =

9 ldflags = $ (textbase) $ (database)-t my. LD

10

11 test. Bin: test.exe

12 $ (objcopy)-O binary test.exe test. Bin

13

14 test.exe: Union. O call. O sramboot. o

15 $ (LD) sramboot. O call. o union. o $ (ldflags)-O test.exe

16 $ (objdump)-D test.exe> test. Dump

17

18 sramboot. O: sramboot. s

19 $ (CC)-E sramboot. S-O sramboot. s

20 $ (AS) sramboot. S-O sramboot. o

21 @ rM sramboot. s

22

23 call. O: Call. s

24 $ (CC)-E call. S-O call. s

25 $ (AS) Call. S-O call. o

26 @ rM call. s

27 Union. O: Union. c

28 $ (CC)-C Union. C-o union. o

29 clean:

30 @ rM *. O *. EXE *. Bin *. Dump

 

My. LD link script file:

1output_format ("elf32-tradlittlemips", "elf32-tradbigmips", "elf32-tradlittlemips ")

2 output_arch (MIPs)

3 entry (start)

4 sections

5 {

6. = 0;

7. init:

8 {

9 sramboot. o

10}

11

12. Text:

13 {

14 * (. Text)

15}

16. Data:

17 {

18. = align (32 );

19 * (. Data. init_task );

20. = align (16 );

21 * (. Data)

22}

23. BSS:

24 {

25 * (. BSS)

26}

27}

 

Test. Sh Native Binary disassembly script:

1 #! /Bin/sh

2 mipsel-Linux-objdump-D-m mips-B Binary-el-m no-aliases-z test. Bin> my. Dump

 

Run the test. dump file generated by make:

1

2 test.exe: File Format elf32-tradlittlemips

3

4 disassembly of section. init:

5

6 00000000 <Start>:

7 0: 3c010000 lui at, 0x0

8 4: 242100c0 addiu at, at, 192

9 8: 8c250004 LW A1, 4 ()

10 C: 0c000010 Jal 40 <my_add>

11 10: 00000000 NOP

12 14: 00853020 add A2, A0, A1

13 18: ac260008 SW A2, 8 ()

14 1c: 00000000 NOP

15 20: 90000072 lbu zero, 114 (zero)

16...

17 disassembly of section. Text:

18

19 00000040 <my_add>:

20 40: 20a50003 addi A1, A1, 3

21 44: 0c000014 Jal 50 <start_kernel>

22 48: 03e00008 Jr Ra

23 4c: 20a50004 addi A1, A1, 4

24

25 00000050 <start_kernel>:

26 50: 27bdfff8 addiu sp, SP,-8

27 54: afbe0000 SW S8, 0 (SP)

28 58: 03a0f021 move S8, SP

29 5C: 1000 ffff B 5C <start_kernel + 0xc>

30 60: 00000000 NOP

31...

32 disassembly of section. Data:

33

34 00000070 <init_thread_union-0x10>:

35...

36

37 00000080 <init_thread_union>:

38 80: 00000009 jalr zero, zero

39 84: 00000008 Jr zero

40 88: 00000000 NOP

41...

42

43 1000000c0 <value>:

44 C0: 0000000a 0xa

45 C4: 00000014 0x14

46 C8: 00000000 NOP

47 CC: 00000088 0x88

48 disassembly of section. PDR:

49

50 00000000 <. PDR>:

51 0: 00000050 0x50

52 4: 40000000 mfc0 zero, $0

53 8: fffffff8 0xfffffff8

54...

55 14: 00000008 Jr zero

56 18: 0000001e 0x1e

57 1c: 0000001f 0x1f

58 disassembly of section. Comment:

59

60 00000000 <. Comment>:

61 0: 43434700 C0 0x1434700

62 4: 4728203a C1 0x128203a

63 8: 2029554e addi T1, AT, 21838

64 C: 2e312e34 sltiu S1, S1, 11828

65 10: Address 0x0000000000000010 is out of bounds.

 

Execute the my. dump file generated by test. sh:

1

2 test. Bin: File Format binary

3

4 disassembly of section. Data:

5

6 0000000000000000 <. Data>:

7 0: 3c010000 lui at, 0x0

8 4: 242100c0 addiu at, at, 192

9 8: 8c250004 LW A1, 4 ()

10 C: 0c000010 Jal 0x40

11 10: 00000000 sll zero, zero, 0x0

12 14: 00853020 add A2, A0, A1

13 18: ac260008 SW A2, 8 ()

14 1c: 00000000 sll zero, zero, 0x0

15 20: 90000072 lbu zero, 114 (zero)

16 24: 00000000 sll zero, zero, 0x0

17 28: 00000000 sll zero, zero, 0x0

18 2C: 00000000 sll zero, zero, 0x0

19 30: 00000000 sll zero, zero, 0x0

20 34: 00000000 sll zero, zero, 0x0

21 38: 00000000 sll zero, zero, 0x0

22 3C: 00000000 sll zero, zero, 0x0

23 40: 20a50003 addi A1, A1, 3

24 44: 0c000014 Jal 0x50

25 48: 03e00008 Jr Ra

26 4c: 20a50004 addi A1, A1, 4

27 50: 27bdfff8 addiu sp, SP,-8

28 54: afbe0000 SW S8, 0 (SP)

29 58: 03a0f021 Addu S8, SP, zero

30 5C: 1000 FFFF beqz zero, 0x5c

31 60: 00000000 sll zero, zero, 0x0

32 64: 00000000 sll zero, zero, 0x0

33 68: 00000000 sll zero, zero, 0x0

34 6C: 00000000 sll zero, zero, 0x0

35 70: 00000000 sll zero, zero, 0x0

36 74: 00000000 sll zero, zero, 0x0

37 78: 00000000 sll zero, zero, 0x0

38 7c: 00000000 sll zero, zero, 0x0

39 80: 00000009 jalr zero, zero

40 84: 00000008 Jr zero

41 88: 00000000 sll zero, zero, 0x0

42 8c: 00000000 sll zero, zero, 0x0

43 90: 00000000 sll zero, zero, 0x0

44 94: 00000000 sll zero, zero, 0x0

45 98: 00000000 sll zero, zero, 0x0

46 9C: 00000000 sll zero, zero, 0x0

47 A0: 00000000 sll zero, zero, 0x0

48 A4: 00000000 sll zero, zero, 0x0

49 A8: 00000000 sll zero, zero, 0x0

50 AC: 00000000 sll zero, zero, 0x0

51 B0: 00000000 sll zero, zero, 0x0

52 B4: 00000000 sll zero, zero, 0x0

53 B8: 00000000 sll zero, zero, 0x0

54 BC: 00000000 sll zero, zero, 0x0

55 C0: 0000000a 0xa

56 C4: 00000014 dsllv zero, zero, zero

57 C8: 00000000 sll zero, zero, 0x0

58 CC: 00000088 0x88