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newlib/libgloss/arm/crt0.S
Jeff Johnston 50e970d1b1 2011-12-13 Richard Earnshaw <rearnsha@arm.com> 
Thomas Klein  <th.r.klein@web.de>

        * arm/crt0.S: Manually set the target architecture
        when compiling for Thumb1 on EABI targets.
        Avoid v6-only Thumb-1 MOV instruction.
2011-12-13 22:45:12 +00:00

493 lines
12 KiB
ArmAsm
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#include "newlib.h"
#include "arm.h"
#include "swi.h"
/* ANSI concatenation macros. */
#define CONCAT(a, b) CONCAT2(a, b)
#define CONCAT2(a, b) a ## b
#ifdef __USER_LABEL_PREFIX__
#define FUNCTION( name ) CONCAT (__USER_LABEL_PREFIX__, name)
#else
#error __USER_LABEL_PREFIX is not defined
#endif
#ifdef HAVE_INITFINI_ARRAY
#define _init __libc_init_array
#define _fini __libc_fini_array
#endif
#if defined(__ARM_EABI__) && defined(__thumb__) && !defined(__thumb2__)
/* For Thumb1 we need to force the architecture to be sure that we get the
correct attributes on the object file; otherwise the assembler will get
confused and mark the object as being v6T2. */
#if defined(__ARM_ARCH_4T__)
.arch armv4t
#elif defined(__ARM_ARCH_5T__) || defined(__ARM_ARCH_5TE__)
/* Nothing in this object requires higher than v5. */
.arch armv5t
#elif defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) \
|| defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_6Z__) \
|| defined(__ARM_ARCH_6ZK__)
/* Nothing in this object requires higher than v6. */
.arch armv6
#elif defined(__ARM_ARCH_6M__)
#ifdef ARM_RDP_MONITOR
/* Object file uses SVC, so mark as v6s-m. */
.arch armv6s-m
#else
.arch armv6-m
#endif
#endif
#endif
/* .text is used instead of .section .text so it works with arm-aout too. */
.text
.syntax unified
#ifdef THUMB_V7_V6M
.thumb
.macro FUNC_START name
.global \name
.thumb_func
\name:
.endm
#else
.code 32
.macro FUNC_START name
.global \name
\name:
.endm
#endif
.macro indirect_call reg
#ifdef HAVE_CALL_INDIRECT
blx \reg
#else
mov lr, pc
mov pc, \reg
#endif
.endm
.align 0
FUNC_START _mainCRTStartup
FUNC_START _start
FUNC_START start
#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
/* Annotation for EABI unwinding tables. */
.fnstart
#endif
/* Start by setting up a stack */
#ifdef ARM_RDP_MONITOR
/* Issue Demon SWI to read stack info */
swi SWI_GetEnv /* Returns command line in r0 */
mov sp,r1 /* and the highest memory address in r1 */
/* stack limit is at end of data */
/* allow slop for stack overflow handling and small frames */
#ifdef __ARM_ARCH_6M__
ldr r0, .LC2
adds r0, #128
adds r0, #128
mov sl, r0
#else
ldr sl, .LC2
add sl, sl, #256
#endif
#else
#ifdef ARM_RDI_MONITOR
/* Issue Angel SWI to read stack info */
movs r0, #AngelSWI_Reason_HeapInfo
adr r1, .LC0 /* point at ptr to 4 words to receive data */
#ifdef THUMB_V7M_V6M
bkpt AngelSWI
#elif defined(__thumb2__)
/* We are in thumb mode for startup on armv7 architectures. */
AngelSWIAsm AngelSWI
#else
/* We are always in ARM mode for startup on pre armv7 archs. */
AngelSWIAsm AngelSWI_ARM
#endif
ldr r0, .LC0 /* point at values read */
ldr r1, [r0, #0]
cmp r1, #0
bne .LC32
/* If the heap base value [r0, #0] is 0 then the heap base is actually
at the end of program data (i.e. __end__). See:
http://infocenter.arm.com/help/topic/com.arm.doc.dui0471-/Bacbefaa.html
for more information. */
ldr r1, .LC31
str r1, [r0, #0]
.LC32:
ldr r1, [r0, #8]
ldr r2, [r0, #12]
/* We skip setting sp/sl if 0 returned from semihosting.
- According to semihosting docs, if 0 returned from semihosting,
the system was unable to calculate the real value, so it's ok
to skip setting sp/sl to 0 here.
- Considering M-profile processors, We might want to initialize
sp by the first entry of vector table and return 0 to SYS_HEAPINFO
semihosting call, which will be skipped here. */
cmp r1, #0
beq .LC26
mov sp, r1
.LC26:
cmp r2, #0
beq .LC27
/* allow slop for stack overflow handling and small frames */
#ifdef __ARM_ARCH_6M__
adds r2, #128
adds r2, #128
mov sl, r2
#else
add sl, r2, #256
#endif
.LC27:
#else
/* Set up the stack pointer to a fixed value */
/* Changes by toralf:
- Allow linker script to provide stack via __stack symbol - see
defintion of .Lstack
- Provide "hooks" that may be used by the application to add
custom init code - see .Lhwinit and .Lswinit
- Go through all execution modes and set up stack for each of them.
Loosely based on init.s from ARM/Motorola example code.
Note: Mode switch via CPSR is not allowed once in non-privileged
mode, so we take care not to enter "User" to set up its sp,
and also skip most operations if already in that mode. */
ldr r3, .Lstack
cmp r3, #0
#ifdef __thumb2__
it eq
#endif
#ifdef __ARM_ARCH_6M__
bne .LC28
ldr r3, .LC0
.LC28:
#else
ldreq r3, .LC0
#endif
/* Note: This 'mov' is essential when starting in User, and ensures we
always get *some* sp value for the initial mode, even if we
have somehow missed it below (in which case it gets the same
value as FIQ - not ideal, but better than nothing.) */
mov sp, r3
#ifdef THUMB_V7_V6M
/* XXX Fill in stack assignments for interrupt modes. */
#else
mrs r2, CPSR
tst r2, #0x0F /* Test mode bits - in User of all are 0 */
beq .LC23 /* "eq" means r2 AND #0x0F is 0 */
msr CPSR_c, #0xD1 /* FIRQ mode, interrupts disabled */
mov sp, r3
sub sl, sp, #0x1000 /* This mode also has its own sl (see below) */
mov r3, sl
msr CPSR_c, #0xD7 /* Abort mode, interrupts disabled */
mov sp, r3
sub r3, r3, #0x1000
msr CPSR_c, #0xDB /* Undefined mode, interrupts disabled */
mov sp, r3
sub r3, r3, #0x1000
msr CPSR_c, #0xD2 /* IRQ mode, interrupts disabled */
mov sp, r3
sub r3, r3, #0x2000
msr CPSR_c, #0xD3 /* Supervisory mode, interrupts disabled */
mov sp, r3
sub r3, r3, #0x8000 /* Min size 32k */
bic r3, r3, #0x00FF /* Align with current 64k block */
bic r3, r3, #0xFF00
str r3, [r3, #-4] /* Move value into user mode sp without */
ldmdb r3, {sp}^ /* changing modes, via '^' form of ldm */
orr r2, r2, #0xC0 /* Back to original mode, presumably SVC, */
msr CPSR_c, r2 /* with FIQ/IRQ disable bits forced to 1 */
#endif
.LC23:
/* Setup a default stack-limit in-case the code has been
compiled with "-mapcs-stack-check". Hard-wiring this value
is not ideal, since there is currently no support for
checking that the heap and stack have not collided, or that
this default 64k is enough for the program being executed.
However, it ensures that this simple crt0 world will not
immediately cause an overflow event: */
#ifdef __ARM_ARCH_6M__
movs r2, #64
lsls r2, r2, #10
subs r2, r3, r2
mov sl, r2
#else
sub sl, r3, #64 << 10 /* Still assumes 256bytes below sl */
#endif
#endif
#endif
/* Zero the memory in the .bss section. */
movs a2, #0 /* Second arg: fill value */
mov fp, a2 /* Null frame pointer */
mov r7, a2 /* Null frame pointer for Thumb */
ldr a1, .LC1 /* First arg: start of memory block */
ldr a3, .LC2
subs a3, a3, a1 /* Third arg: length of block */
#if defined(__thumb__) && !defined(THUMB_V7_V6M)
/* Enter Thumb mode.... */
add a4, pc, #1 /* Get the address of the Thumb block */
bx a4 /* Go there and start Thumb decoding */
.code 16
.global __change_mode
.thumb_func
__change_mode:
#endif
bl FUNCTION (memset)
#if !defined (ARM_RDP_MONITOR) && !defined (ARM_RDI_MONITOR)
/* Changes by toralf: Taken from libgloss/m68k/crt0.S
* initialize target specific stuff. Only execute these
* functions it they exist.
*/
ldr r3, .Lhwinit
cmp r3, #0
beq .LC24
indirect_call r3
.LC24:
ldr r3, .Lswinit
cmp r3, #0
beq .LC25
indirect_call r3
.LC25:
movs r0, #0 /* no arguments */
movs r1, #0 /* no argv either */
#else
/* Need to set up standard file handles */
bl FUNCTION (initialise_monitor_handles)
#ifdef ARM_RDP_MONITOR
swi SWI_GetEnv /* sets r0 to point to the command line */
movs r1, r0
#else
movs r0, #AngelSWI_Reason_GetCmdLine
adr r1, .LC30 /* Space for command line */
AngelSWIAsm AngelSWI
ldr r1, .LC30
#endif
/* Parse string at r1 */
movs r0, #0 /* count of arguments so far */
/* Push a NULL argument onto the end of the list. */
#ifdef __thumb__
push {r0}
#else
stmfd sp!, {r0}
#endif
.LC10:
/* Skip leading blanks */
#ifdef __thumb__
ldrb r3, [r1]
adds r1, #1
#else
ldrb r3, [r1], #1
#endif
cmp r3, #0
beq .LC12
cmp r3, #' '
beq .LC10
/* See whether we are scanning a string */
cmp r3, #'"'
#ifdef __thumb__
beq .LC20
cmp r3, #'\''
bne .LC21
.LC20:
movs r2, r3
b .LC22
.LC21:
movs r2, #' ' /* terminator type */
subs r1, r1, #1 /* adjust back to point at start char */
.LC22:
#else
cmpne r3, #'\''
moveq r2, r3
movne r2, #' ' /* terminator type */
subne r1, r1, #1 /* adjust back to point at start char */
#endif
/* Stack a pointer to the current argument */
#ifdef __thumb__
push {r1}
#else
stmfd sp!, {r1}
#endif
adds r0, r0, #1
.LC11:
#ifdef __thumb__
ldrb r3, [r1]
adds r1, #1
#else
ldrb r3, [r1], #1
#endif
cmp r3, #0
beq .LC12
cmp r2, r3 /* reached terminator? */
bne .LC11
movs r2, #0
subs r3, r1, #1
strb r2, [r3] /* terminate the arg string */
b .LC10
.LC12:
mov r1, sp /* point at stacked arg pointers */
/* We've now got the stacked args in order reverse the */
#ifdef __thumb__
movs r2, r0
lsls r2, #2
add r2, sp
mov r3, sp
.LC15: cmp r2, r3
bls .LC14
subs r2, #4
ldr r4, [r2]
ldr r5, [r3]
str r5, [r2]
str r4, [r3]
adds r3, #4
b .LC15
.LC14:
/* Ensure doubleword stack alignment. */
mov r4, sp
movs r5, #7
bics r4, r5
mov sp, r4
#else
add r2, sp, r0, LSL #2 /* End of args */
mov r3, sp /* Start of args */
.LC13: cmp r2, r3
ldrhi r4,[r2, #-4] /* Reverse ends of list */
ldrhi r5, [r3]
strhi r5, [r2, #-4]!
strhi r4, [r3], #4
bhi .LC13
/* Ensure doubleword stack alignment. */
bic sp, sp, #7
#endif
#endif
#ifdef __USES_INITFINI__
/* Some arm/elf targets use the .init and .fini sections
to create constructors and destructors, and for these
targets we need to call the _init function and arrange
for _fini to be called at program exit. */
movs r4, r0
movs r5, r1
ldr r0, .Lfini
bl FUNCTION (atexit)
bl FUNCTION (_init)
movs r0, r4
movs r1, r5
#endif
bl FUNCTION (main)
bl FUNCTION (exit) /* Should not return. */
#if defined(__thumb__) && !defined(THUMB_V7_V6M)
/* Come out of Thumb mode. This code should be redundant. */
mov a4, pc
bx a4
.code 32
.global change_back
change_back:
/* Halt the execution. This code should never be executed. */
/* With no debug monitor, this probably aborts (eventually).
With a Demon debug monitor, this halts cleanly.
With an Angel debug monitor, this will report 'Unknown SWI'. */
swi SWI_Exit
#endif
/* For Thumb, constants must be after the code since only
positive offsets are supported for PC relative addresses. */
.align 0
.LC0:
#ifdef ARM_RDI_MONITOR
.word HeapBase
#else
#ifndef ARM_RDP_MONITOR
/* Changes by toralf: Provide alternative "stack" variable whose value
may be defined externally; .Lstack will be used instead of .LC0 if
it points to a non-0 value. Also set up references to "hooks" that
may be used by the application to provide additional init code. */
#ifdef __pe__
.word 0x800000
#else
.word 0x80000 /* Top of RAM on the PIE board. */
#endif
.Lstack:
.word __stack
.Lhwinit:
.word FUNCTION (hardware_init_hook)
.Lswinit:
.word FUNCTION (software_init_hook)
/* Set up defaults for the above variables in the form of weak symbols
- so that application will link correctly, and get value 0 in
runtime (meaning "ignore setting") for the variables, when the user
does not provide the symbols. (The linker uses a weak symbol if,
and only if, a normal version of the same symbol isn't provided
e.g. by a linker script or another object file.) */
.weak __stack
.weak FUNCTION (hardware_init_hook)
.weak FUNCTION (software_init_hook)
#endif
#endif
#if defined(__ELF__) && !defined(__USING_SJLJ_EXCEPTIONS__)
/* Protect against unhandled exceptions. */
.cantunwind
.fnend
#endif
.LC1:
.word __bss_start__
.LC2:
.word __bss_end__
#ifdef __USES_INITFINI__
.Lfini:
.word FUNCTION(_fini)
#endif
#ifdef ARM_RDI_MONITOR
.LC30:
.word CommandLine
.word 255
.LC31:
.word __end__
/* Workspace for Angel calls. */
.data
/* Data returned by monitor SWI. */
.global __stack_base__
HeapBase: .word 0
HeapLimit: .word 0
__stack_base__: .word 0
StackLimit: .word 0
CommandLine: .space 256,0 /* Maximum length of 255 chars handled. */
#endif
#ifdef __pe__
.section .idata$3
.long 0,0,0,0,0,0,0,0
#endif
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