source: trunk/libs/newlib/src/libgloss/sparc/libsys/libsys-crt0.S @ 656

Last change on this file since 656 was 444, checked in by satin@…, 6 years ago

add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc

File size: 3.1 KB
Line 
1! C run time start off
2
3! This file supports:
4!
5! - both 32bit pointer and 64bit pointer environments (at compile time)
6! - an imposed stack bias (of 2047) (at run time)
7! - medium/low and medium/anywhere code models (at run time)
8
9! Initial stack setup:
10!
11!    bottom of stack (higher memory address)
12!       ...
13!       text of environment strings
14!       text of argument strings
15!       envp[envc] = 0 (4/8 bytes)
16!       ...
17!       env[0] (4/8 bytes)
18!       argv[argc] = 0 (4/8 bytes)
19!       ...
20!       argv[0] (4/8 bytes)
21!       argc (4/8 bytes)
22!       register save area (64 bits by 16 registers = 128 bytes)
23!       top of stack (%sp)
24
25! Stack Bias:
26!
27! It is the responsibility of the o/s to set this up.
28! We handle both a 0 and 2047 value for the stack bias.
29
30! Medium/Anywhere code model support:
31!
32! In this model %g4 points to the start of the data segment.
33! The text segment can go anywhere, but %g4 points to the *data* segment.
34! It is up to the compiler/linker to get this right.
35!
36! Since this model is statically linked the start of the data segment
37! is known at link time.  Eg:
38!
39!       sethi   %hh(data_start), %g1
40!       sethi   %lm(data_start), %g4
41!       or      %g1, %hm(data_start), %g1
42!       or      %g4, %lo(data_start), %g4
43!       sllx    %g1, 32, %g1
44!       or      %g4, %g1, %g4
45!
46! FIXME: For now we just assume 0.
47
48! FIXME: if %g1 contains a non-zero value, atexit() should be invoked
49! with this value.
50
51#include "syscallasm.h"
52
53#ifndef TARGET_PTR_SIZE
54#define TARGET_PTR_SIZE 32
55#endif
56
57        TEXT_SECTION
58        ALIGN (4)
59        GLOBAL (ASM_PRIVATE_SYMBOL (start))
60ASM_PRIVATE_SYMBOL (start):
61        clr     %fp
62
63! We use %g4 even if the code model is Medium/Low (simplifies the code).
64
65        clr     %g4                     ! Medium/Anywhere base reg
66
67! If there is a stack bias in effect, account for it in %g5.  Then always
68! add %g5 to stack references below.  This way the code can be used with
69! or without an imposed bias.
70
71        andcc   %sp, 1, %g5
72        bnz,a   .LHaveBias
73        mov     2047, %g5
74.LHaveBias:
75        add     %sp, %g5, %sp
76
77#if TARGET_PTR_SIZE == 32
78        ! FIXME: We apparently assume here that there is no reserved word.
79        ! This is probably correct, but try to verify it.
80        ld      [%sp + 0x80], %o0       ! argc
81        add     %sp, 0x84, %o1          ! argv
82        add     %o0, 1, %o2
83        sll     %o2, 2, %o2
84#else /* TARGET_PTR_SIZE == 64 */
85        ld      [%sp + 0x8c], %o0       ! argc.lo
86        add     %sp, 0x90, %o1          ! argv
87        add     %o0, 1, %o2
88        sll     %o2, 3, %o2
89#endif
90        add     %o1, %o2, %o2           ! envp
91        sethi   %hi (ASM_SYMBOL (environ)), %o3
92        or      %o3, %lo (ASM_SYMBOL (environ)), %o3
93#if TARGET_PTR_SIZE == 32
94        st      %o2, [%o3 + %g4]
95#else /* TARGET_PTR_SIZE == 64 */
96        stx     %o2, [%o3 + %g4]
97#endif
98
99! Restore any stack bias before we call main() ...
100
101        sub     %sp, %g5, %sp
102
103        GLOBAL (ASM_SYMBOL (main))
104        call    ASM_SYMBOL (main)
105
106! FIXME: Not sure if this is needed anymore.
107#if TARGET_PTR_SIZE == 32
108        sub     %sp, 0x20, %sp          ! room to push args
109#else /* TARGET_PTR_SIZE == 64 */
110        sub     %sp, 0x30, %sp          ! room to push args
111#endif
112
113        GLOBAL (ASM_SYMBOL (exit))
114        call    ASM_SYMBOL (exit)
115        nop
116
117        GLOBAL (ASM_SYMBOL (_exit))
118        call    ASM_SYMBOL (_exit)
119        nop
120
121        set     SYS_exit, %g1
122        ta      SYSCALL_TRAP            ! in case user redefines __exit
123
124! If all the above methods fail to terminate the program, try an illegal insn.
125! If that does not work, the o/s is hosed more than we are.
126
127        WORD (0)
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