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crt0.S @ 597

Last change on this file since 597 was 444, checked in by satin@…, 6 years ago
add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc
File size: 13.2 KB

Line
1	#include "newlib.h"
2	#include "arm.h"
3	#include "swi.h"
4
5	/* ANSI concatenation macros. */
6	#define CONCAT(a, b) CONCAT2(a, b)
7	#define CONCAT2(a, b) a ## b
8
9	#ifdef __USER_LABEL_PREFIX__
10	#define FUNCTION( name ) CONCAT (__USER_LABEL_PREFIX__, name)
11	#else
12	#error __USER_LABEL_PREFIX is not defined
13	#endif
14
15	#ifdef HAVE_INITFINI_ARRAY
16	#define _init __libc_init_array
17	#define _fini __libc_fini_array
18	#endif
19
20	#if defined(__ARM_EABI__) && defined(__thumb__) && !defined(__thumb2__)
21	/* For Thumb1 we need to force the architecture to be sure that we get the
22	correct attributes on the object file; otherwise the assembler will get
23	confused and mark the object as being v6T2. */
24	#if defined(__ARM_ARCH_4T__)
25	.arch armv4t
26	#elif defined(__ARM_ARCH_5T__) \|\| defined(__ARM_ARCH_5TE__)
27	/* Nothing in this object requires higher than v5. */
28	.arch armv5t
29	#elif defined(__ARM_ARCH_6__) \|\| defined(__ARM_ARCH_6J__) \
30	\|\| defined(__ARM_ARCH_6K__) \|\| defined(__ARM_ARCH_6Z__) \
31	\|\| defined(__ARM_ARCH_6ZK__)
32	/* Nothing in this object requires higher than v6. */
33	.arch armv6
34	#elif defined(__ARM_ARCH_6M__)
35	#ifdef ARM_RDP_MONITOR
36	/* Object file uses SVC, so mark as v6s-m. */
37	.arch armv6s-m
38	#else
39	.arch armv6-m
40	#endif
41	#endif
42	#endif
43
44	/* .text is used instead of .section .text so it works with arm-aout too. */
45	.text
46	.syntax unified
47	#ifdef PREFER_THUMB
48	.thumb
49	.macro FUNC_START name
50	.global \name
51	.thumb_func
52	\name:
53	.endm
54	#else
55	.code 32
56	.macro FUNC_START name
57	.global \name
58	\name:
59	.endm
60	#endif
61
62	.macro indirect_call reg
63	#ifdef HAVE_CALL_INDIRECT
64	blx \reg
65	#else
66	mov lr, pc
67	mov pc, \reg
68	#endif
69	.endm
70
71	.align 0
72
73	FUNC_START _mainCRTStartup
74	FUNC_START _start
75	#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
76	/* Annotation for EABI unwinding tables. */
77	.fnstart
78	#endif
79
80	/* __ARM_ARCH_PROFILE is defined from GCC 4.8 onwards, however __ARM_ARCH_7A
81	has been defined since 4.2 onwards, which is when v7-a support was added
82	and hence 'A' profile support was added in the compiler. Allow for this
83	file to be built with older compilers. We only call this for A profile
84	cores. */
85	#if defined (__ARM_ARCH_7A__) \|\| (__ARM_ARCH_PROFILE == 'A')
86	/* The init hook does not use the stack and is called before the stack has been set up. */
87	#ifdef ARM_RDI_MONITOR
88	bl _rdimon_hw_init_hook
89	.weak FUNCTION (_rdimon_hw_init_hook)
90	#endif
91	#endif
92
93	/* Start by setting up a stack */
94	#ifdef ARM_RDP_MONITOR
95	/* Issue Demon SWI to read stack info */
96	swi SWI_GetEnv /* Returns command line in r0 */
97	mov sp,r1 /* and the highest memory address in r1 */
98
99	/* stack limit is at end of data */
100	/* allow slop for stack overflow handling and small frames */
101	#ifdef THUMB1_ONLY
102	ldr r0, .LC2
103	adds r0, #128
104	adds r0, #128
105	mov sl, r0
106	#else
107	ldr sl, .LC2
108	add sl, sl, #256
109	#endif
110	#else
111	#ifdef ARM_RDI_MONITOR
112	/* Issue Angel SWI to read stack info */
113	movs r0, #AngelSWI_Reason_HeapInfo
114	adr r1, .LC0 /* point at ptr to 4 words to receive data */
115	#ifdef THUMB_VXM
116	bkpt AngelSWI
117	#elif defined(__thumb2__)
118	/* We are in thumb mode for startup on armv7 architectures. */
119	AngelSWIAsm AngelSWI
120	#else
121	/* We are always in ARM mode for startup on pre armv7 archs. */
122	AngelSWIAsm AngelSWI_ARM
123	#endif
124	ldr r0, .LC0 /* point at values read */
125
126	/* Set __heap_limit. */
127	ldr r1, [r0, #4]
128	cmp r1, #0
129	beq .LC33
130	ldr r2, =__heap_limit
131	str r1, [r2]
132	.LC33:
133	ldr r1, [r0, #0]
134	cmp r1, #0
135	bne .LC32
136	/* If the heap base value [r0, #0] is 0 then the heap base is actually
137	at the end of program data (i.e. __end__). See:
138	http://infocenter.arm.com/help/topic/com.arm.doc.dui0471-/Bacbefaa.html
139	for more information. */
140	ldr r1, .LC31
141	str r1, [r0, #0]
142	.LC32:
143	ldr r1, [r0, #8]
144	ldr r2, [r0, #12]
145	/* We skip setting sp/sl if 0 returned from semihosting.
146	- According to semihosting docs, if 0 returned from semihosting,
147	the system was unable to calculate the real value, so it's ok
148	to skip setting sp/sl to 0 here.
149	- Considering M-profile processors, We might want to initialize
150	sp by the first entry of vector table and return 0 to SYS_HEAPINFO
151	semihosting call, which will be skipped here. */
152	cmp r1, #0
153	beq .LC26
154	mov sp, r1
155	.LC26:
156	cmp r2, #0
157	beq .LC27
158	/* allow slop for stack overflow handling and small frames */
159	#ifdef THUMB1_ONLY
160	adds r2, #128
161	adds r2, #128
162	mov sl, r2
163	#else
164	add sl, r2, #256
165	#endif
166	.LC27:
167	#else
168	/* Set up the stack pointer to a fixed value */
169	/* Changes by toralf:
170	- Allow linker script to provide stack via __stack symbol - see
171	defintion of .Lstack
172	- Provide "hooks" that may be used by the application to add
173	custom init code - see .Lhwinit and .Lswinit
174	- Go through all execution modes and set up stack for each of them.
175	Loosely based on init.s from ARM/Motorola example code.
176	Note: Mode switch via CPSR is not allowed once in non-privileged
177	mode, so we take care not to enter "User" to set up its sp,
178	and also skip most operations if already in that mode. */
179
180	ldr r3, .Lstack
181	cmp r3, #0
182	#ifdef __thumb2__
183	it eq
184	#endif
185	#ifdef THUMB1_ONLY
186	bne .LC28
187	ldr r3, .LC0
188	.LC28:
189	#else
190	ldreq r3, .LC0
191	#endif
192	/* Note: This 'mov' is essential when starting in User, and ensures we
193	always get some sp value for the initial mode, even if we
194	have somehow missed it below (in which case it gets the same
195	value as FIQ - not ideal, but better than nothing.) */
196	mov sp, r3
197	#ifdef PREFER_THUMB
198	/* XXX Fill in stack assignments for interrupt modes. */
199	#else
200	mrs r2, CPSR
201	tst r2, #0x0F /* Test mode bits - in User of all are 0 */
202	beq .LC23 /* "eq" means r2 AND #0x0F is 0 */
203	msr CPSR_c, #0xD1 /* FIRQ mode, interrupts disabled */
204	mov sp, r3
205	sub sl, sp, #0x1000 /* This mode also has its own sl (see below) */
206
207	mov r3, sl
208	msr CPSR_c, #0xD7 /* Abort mode, interrupts disabled */
209	mov sp, r3
210	sub r3, r3, #0x1000
211
212	msr CPSR_c, #0xDB /* Undefined mode, interrupts disabled */
213	mov sp, r3
214	sub r3, r3, #0x1000
215
216	msr CPSR_c, #0xD2 /* IRQ mode, interrupts disabled */
217	mov sp, r3
218	sub r3, r3, #0x2000
219
220	msr CPSR_c, #0xD3 /* Supervisory mode, interrupts disabled */
221
222	mov sp, r3
223	sub r3, r3, #0x8000 /* Min size 32k */
224	bic r3, r3, #0x00FF /* Align with current 64k block */
225	bic r3, r3, #0xFF00
226
227	str r3, [r3, #-4] /* Move value into user mode sp without */
228	ldmdb r3, {sp}^ /* changing modes, via '^' form of ldm */
229	orr r2, r2, #0xC0 /* Back to original mode, presumably SVC, */
230	msr CPSR_c, r2 /* with FIQ/IRQ disable bits forced to 1 */
231	#endif
232	.LC23:
233	/* Setup a default stack-limit in-case the code has been
234	compiled with "-mapcs-stack-check". Hard-wiring this value
235	is not ideal, since there is currently no support for
236	checking that the heap and stack have not collided, or that
237	this default 64k is enough for the program being executed.
238	However, it ensures that this simple crt0 world will not
239	immediately cause an overflow event: */
240	#ifdef THUMB1_ONLY
241	movs r2, #64
242	lsls r2, r2, #10
243	subs r2, r3, r2
244	mov sl, r2
245	#else
246	sub sl, r3, #64 << 10 /* Still assumes 256bytes below sl */
247	#endif
248	#endif
249	#endif
250	/* Zero the memory in the .bss section. */
251	movs a2, #0 /* Second arg: fill value */
252	mov fp, a2 /* Null frame pointer */
253	mov r7, a2 /* Null frame pointer for Thumb */
254
255	ldr a1, .LC1 /* First arg: start of memory block */
256	ldr a3, .LC2
257	subs a3, a3, a1 /* Third arg: length of block */
258
259
260	#if __thumb__ && !defined(PREFER_THUMB)
261	/* Enter Thumb mode.... */
262	add a4, pc, #1 /* Get the address of the Thumb block */
263	bx a4 /* Go there and start Thumb decoding */
264
265	.code 16
266	.global __change_mode
267	.thumb_func
268	__change_mode:
269	#endif
270
271	bl FUNCTION (memset)
272	#if !defined (ARM_RDP_MONITOR) && !defined (ARM_RDI_MONITOR)
273	/* Changes by toralf: Taken from libgloss/m68k/crt0.S
274	* initialize target specific stuff. Only execute these
275	* functions it they exist.
276	*/
277	ldr r3, .Lhwinit
278	cmp r3, #0
279	beq .LC24
280	indirect_call r3
281	.LC24:
282	ldr r3, .Lswinit
283	cmp r3, #0
284	beq .LC25
285	indirect_call r3
286
287	.LC25:
288	movs r0, #0 /* no arguments */
289	movs r1, #0 /* no argv either */
290	#else
291	/* Need to set up standard file handles */
292	bl FUNCTION (initialise_monitor_handles)
293
294	#ifdef ARM_RDP_MONITOR
295	swi SWI_GetEnv /* sets r0 to point to the command line */
296	movs r1, r0
297	#else
298	movs r0, #AngelSWI_Reason_GetCmdLine
299	ldr r1, .LC30 /* Space for command line */
300	AngelSWIAsm AngelSWI
301	ldr r1, .LC30
302	ldr r1, [r1]
303	#endif
304	/* Parse string at r1 */
305	movs r0, #0 /* count of arguments so far */
306	/* Push a NULL argument onto the end of the list. */
307	#ifdef __thumb__
308	push {r0}
309	#else
310	stmfd sp!, {r0}
311	#endif
312	.LC10:
313	/* Skip leading blanks */
314	#ifdef __thumb__
315	ldrb r3, [r1]
316	adds r1, #1
317	#else
318	ldrb r3, [r1], #1
319	#endif
320	cmp r3, #0
321	beq .LC12
322	cmp r3, #' '
323	beq .LC10
324
325	/* See whether we are scanning a string */
326	cmp r3, #'"'
327	#ifdef __thumb__
328	beq .LC20
329	cmp r3, #'\''
330	bne .LC21
331	.LC20:
332	movs r2, r3
333	b .LC22
334
335	.LC21:
336	movs r2, #' ' /* terminator type */
337	subs r1, r1, #1 /* adjust back to point at start char */
338	.LC22:
339	#else
340	cmpne r3, #'\''
341	moveq r2, r3
342	movne r2, #' ' /* terminator type */
343	subne r1, r1, #1 /* adjust back to point at start char */
344	#endif
345
346	/* Stack a pointer to the current argument */
347	#ifdef __thumb__
348	push {r1}
349	#else
350	stmfd sp!, {r1}
351	#endif
352	adds r0, r0, #1
353	.LC11:
354	#ifdef __thumb__
355	ldrb r3, [r1]
356	adds r1, #1
357	#else
358	ldrb r3, [r1], #1
359	#endif
360	cmp r3, #0
361	beq .LC12
362	cmp r2, r3 /* reached terminator? */
363	bne .LC11
364	movs r2, #0
365	subs r3, r1, #1
366	strb r2, [r3] /* terminate the arg string */
367	b .LC10
368
369	.LC12:
370	mov r1, sp /* point at stacked arg pointers */
371	/* We've now got the stacked args in order reverse the */
372	#ifdef __thumb__
373	movs r2, r0
374	lsls r2, #2
375	add r2, sp
376	mov r3, sp
377	.LC15: cmp r2, r3
378	bls .LC14
379	subs r2, #4
380	ldr r4, [r2]
381	ldr r5, [r3]
382	str r5, [r2]
383	str r4, [r3]
384	adds r3, #4
385	b .LC15
386	.LC14:
387	/* Ensure doubleword stack alignment. */
388	mov r4, sp
389	movs r5, #7
390	bics r4, r5
391	mov sp, r4
392	#else
393	add r2, sp, r0, LSL #2 /* End of args */
394	mov r3, sp /* Start of args */
395	.LC13: cmp r2, r3
396	ldrhi r4,[r2, #-4] /* Reverse ends of list */
397	ldrhi r5, [r3]
398	strhi r5, [r2, #-4]!
399	strhi r4, [r3], #4
400	bhi .LC13
401	/* Ensure doubleword stack alignment. */
402	bic sp, sp, #7
403	#endif
404	#endif
405
406	#ifdef __USES_INITFINI__
407	/* Some arm/elf targets use the .init and .fini sections
408	to create constructors and destructors, and for these
409	targets we need to call the _init function and arrange
410	for _fini to be called at program exit. */
411	movs r4, r0
412	movs r5, r1
413	#ifdef _LITE_EXIT
414	/* Make reference to atexit weak to avoid unconditionally pulling in
415	support code. Refer to comments in __atexit.c for more details. */
416	.weak FUNCTION(atexit)
417	ldr r0, .Latexit
418	cmp r0, #0
419	beq .Lweak_atexit
420	#endif
421	ldr r0, .Lfini
422	bl FUNCTION (atexit)
423	.Lweak_atexit:
424	bl FUNCTION (_init)
425	movs r0, r4
426	movs r1, r5
427	#endif
428	bl FUNCTION (main)
429
430	bl FUNCTION (exit) /* Should not return. */
431
432	#if __thumb__ && !defined(PREFER_THUMB)
433	/* Come out of Thumb mode. This code should be redundant. */
434
435	mov a4, pc
436	bx a4
437
438	.code 32
439	.global change_back
440	change_back:
441	/* Halt the execution. This code should never be executed. */
442	/* With no debug monitor, this probably aborts (eventually).
443	With a Demon debug monitor, this halts cleanly.
444	With an Angel debug monitor, this will report 'Unknown SWI'. */
445	swi SWI_Exit
446	#endif
447
448	/* For Thumb, constants must be after the code since only
449	positive offsets are supported for PC relative addresses. */
450
451	.align 0
452	.LC0:
453	#ifdef ARM_RDI_MONITOR
454	.word HeapBase
455	#else
456	#ifndef ARM_RDP_MONITOR
457	/* Changes by toralf: Provide alternative "stack" variable whose value
458	may be defined externally; .Lstack will be used instead of .LC0 if
459	it points to a non-0 value. Also set up references to "hooks" that
460	may be used by the application to provide additional init code. */
461
462	#ifdef __pe__
463	.word 0x800000
464	#else
465	.word 0x80000 /* Top of RAM on the PIE board. */
466	#endif
467	.Lstack:
468	.word __stack
469	.Lhwinit:
470	.word FUNCTION (hardware_init_hook)
471	.Lswinit:
472	.word FUNCTION (software_init_hook)
473
474	/* Set up defaults for the above variables in the form of weak symbols
475	- so that application will link correctly, and get value 0 in
476	runtime (meaning "ignore setting") for the variables, when the user
477	does not provide the symbols. (The linker uses a weak symbol if,
478	and only if, a normal version of the same symbol isn't provided
479	e.g. by a linker script or another object file.) */
480
481	.weak __stack
482	.weak FUNCTION (hardware_init_hook)
483	.weak FUNCTION (software_init_hook)
484	#endif
485
486	#endif
487	#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
488	/* Protect against unhandled exceptions. */
489	.cantunwind
490	.fnend
491	#endif
492	.LC1:
493	.word __bss_start__
494	.LC2:
495	.word __bss_end__
496	#ifdef __USES_INITFINI__
497	#ifdef _LITE_EXIT
498	.Latexit:
499	.word FUNCTION(atexit)
500
501	/* Weak reference _fini in case of lite exit. */
502	.weak FUNCTION(_fini)
503	#endif
504	.Lfini:
505	.word FUNCTION(_fini)
506	#endif
507	#ifdef ARM_RDI_MONITOR
508	.LC30:
509	.word AngelSWIArgs
510	.LC31:
511	.word __end__
512
513	/* Workspace for Angel calls. */
514	.data
515	/* Data returned by monitor SWI. */
516	.global __stack_base__
517	HeapBase: .word 0
518	HeapLimit: .word 0
519	__stack_base__: .word 0
520	StackLimit: .word 0
521	CommandLine: .space 256,0 /* Maximum length of 255 chars handled. */
522	AngelSWIArgs:
523	.word CommandLine
524	.word 255
525	#endif
526
527	#ifdef __pe__
528	.section .idata$3
529	.long 0,0,0,0,0,0,0,0
530	#endif

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