libgloss: msp430: split up crt0.S source

The build system compiles crt0.S many times to produce independent
object files by defining different -DLxxx symbols for each.  This
complicates the build, and has led to some bugs in the source and
build (see the previous cleanup commits in here).  The crt_bss.S
file has also been duplicated with crt0.S leading to confusion as
to which one is the "real" one.  The only reason to keep them in
one file is to make management of the section numbers when calling
START_CRT_FUNC a little easier, but that seems trivial to check
with a quick grep across all the files.

Considering how complicated the build is now, and the bugs we've
had as a result, split the crt0.S file up into multiple source
files so we don't have to compile it multiple times.  This will
also simplify merging it into the top-level Makefile.
This commit is contained in:
Mike Frysinger 2023-12-26 22:01:30 -05:00
parent 2b0fd70308
commit f5c40e04e5
14 changed files with 499 additions and 212 deletions

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@ -78,8 +78,6 @@ NOSYS_OBJS = ciosyscalls.o \
unlink.o \
sbrk.o
# Each crt_*.o is built from crt0.S using -DL*. crt0.o is built from
# crt0.s with -DL0 via the default rule below.
CRT_OBJS = \
crt_bss.o \
crt_high_bss.o \
@ -98,12 +96,9 @@ CRT_OBJS = \
all: $(CRT) $(SIM_BSP) $(LIB_NOSYS) $(LIB_CRT) copy_scripts_to_objdir
crt_%.o : crt0.S
$(CC) -DL$* -Wa,-gdwarf2 -Wa,-I$(srcdir) $(CFLAGS_FOR_TARGET) $(INCLUDES) $(CFLAGS) -c $< -o $@
# Override .S.o rule to pass assembler debugging flags
.S.o:
$(CC) -DL0 -Wa,-gdwarf2 -Wa,-I$(srcdir) $(CFLAGS_FOR_TARGET) $(INCLUDES) $(CFLAGS) -c $<
$(CC) -Wa,-gdwarf2 -Wa,-I$(srcdir) $(CFLAGS_FOR_TARGET) $(INCLUDES) $(CFLAGS) -c $<
$(SIM_BSP): $(SIM_OBJS)
$(AR) $(ARFLAGS) $@ $?

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@ -13,13 +13,6 @@
#include "memmodel.h"
;; The linker links all .crt_* sections in asciibetical order at the
;; same place. So, the four digits in .crt_NNNN_xxx name created by
;; the START_CRT_FUNC macro determine the link order, so, keep them
;; in sequential order here. The first two digits are set here, the
;; second two allow users to insert code between code fragments here.
#if L0
.section ".resetvec", "a"
__msp430_resetvec_hook:
.word __crt0_start
@ -56,9 +49,8 @@ START_CRT_FUNC 0000 start
mov_ #__stack, R1
END_CRT_FUNC start
#endif
;; The CRT functions below will only be present in the final linked
;; The CRT functions will only be present in the final linked
;; executable if the assembler decides they are needed. The assembler will
;; only define the symbol necessary to prevent them being garbage collected
;; by the linker if the file being assembled has a specific section,
@ -67,185 +59,3 @@ END_CRT_FUNC start
;; if it detects that main() has an epilogue. For example, if main() has a
;; while(1) loop at the end, GCC will not generate an epilogue (since it won't
;; return) and __crt0_call_exit won't be included.
#if Lbss
;; This function is responsible for initializing the contents of the
;; .bss section.
START_CRT_FUNC 0100 init_bss
mov_ #__bssstart, R12
clr.w R13
mov_ #__bsssize, R14
#ifdef __MSP430X_LARGE__
clr.w R15 ; We assume that __bsssize is never > 64K
#endif
call_ #memset
END_CRT_FUNC init_bss
#endif /* Lbss */
#ifdef __MSP430X_LARGE__
#if Lhigh_bss
;; This function is responsible for initializing the contents of the
;; .upper.bss section.
START_CRT_FUNC 0200 init_highbss
mov_ #__high_bssstart, R12
mov.w #0, R13
mov_ #__high_bsssize, R14
;; If __high_bsssize is zero then skip the call to memset.
;; This can happen if all of the bss data was placed into .either.bss.
cmp.w #0, R14
jeq 1f
call_ #memset
1:
END_CRT_FUNC init_highbss
#endif /* Lhigh_bss */
#endif /* __MSP430X_LARGE__ */
#if Lmovedata
;; This function is responsible for copying the
;; contents of the .data section from its load address (in ROM) to
;; its run-time address (in RAM).
START_CRT_FUNC 0300 movedata
mov_ #__datastart, R12
mov_ #__romdatastart, R13
;; memmove and memcpy do not currently work when src == dst
cmp_ R12, R13
jeq 1f
mov_ #__romdatacopysize, R14
call_ #memmove
1:
END_CRT_FUNC movedata
#endif /* Lmovedata */
#ifdef __MSP430X_LARGE__
#if Lmove_highdata
;; This function is responsible for making sure that the
;; contents of the .upper.data section have their correct startup values.
;; If a copy of the .upper.data section is stored in ROM then this means
;; copying the contents into HIFRAM. If a copy of .upper.data is stored in a
;; shadow section in HIFRAM then this means copying from the shadow section
;; into the real section.
START_CRT_FUNC 0400 move_highdata
;; __rom_highdatacopysize may be zero. Test this first because
;; its value may come from the weak definitions above and we do
;; not want to access the memory at address 0 pointed to by the
;; weak definition of __upper_data_init.
mov.w #__rom_highdatacopysize, R14
cmp.w #0, R14
jeq 3f
/* Test our status word. */
cmpx.w #0, &__upper_data_init
jeq 1f
/* Status word is non-zero - copy from shadow into upper. */
mov_ #__high_datastart, R12
mov_ #__rom_highdatastart, R13
jmp 2f
1: /* Status word is zero. Copy from upper to shadow and change status word. */
movx.w #1, &__upper_data_init
mov_ #__rom_highdatastart, R12
mov_ #__high_datastart, R13
2: ;; __rom_highdatacopysize may be zero. memmove should cope.
mov.w #__rom_highdatacopysize, R14
call_ #memmove
3:
END_CRT_FUNC move_highdata
#endif /* Lmove_highdata */
#endif /* __MSP430X_LARGE__ */
#if Lrun_preinit_array
;; This function is responsible for setting up the arguments
;; required for __crt0_run_array, to run the functions in .preinit_array.
START_CRT_FUNC 0500 run_preinit_array
mov_ #__preinit_array_start, R4
mov_ #__preinit_array_end, R5
mov_ #PTRsz, R6
call_ #__crt0_run_array
END_CRT_FUNC run_preinit_array
#endif /* Lrun_preinit_array */
#if Lrun_init_array
;; This function is responsible for setting up the arguments
;; required for __crt0_run_array, to run the functions in .init_array.
START_CRT_FUNC 0600 run_init_array
mov_ #__init_array_start, R4
mov_ #__init_array_end, R5
mov_ #PTRsz, R6
call_ #__crt0_run_array
END_CRT_FUNC run_init_array
#endif /* Lrun_init_array */
#if Lmain
;; This function is always included and calls main().
START_CRT_FUNC 0800 call_main
clr.w R12 ; Set argc == 0
call_ #main
END_CRT_FUNC call_main
#endif /* Lmain */
#if Lcallexit
;; This function is responsible for calling exit once main has finished.
START_CRT_FUNC 0900 call_exit
call_ #_exit
END_CRT_FUNC call_exit
#endif /* Lcallexit */
;----------------------------------------
#if Lrun_fini_array
;; This function is responsible for setting up the arguments
;; required for __crt0_run_array, to run the functions in .fini_array.
START_CRT_FUNC 1000 run_fini_array
mov_ #__fini_array_start, R4
mov_ #__fini_array_end, R5
mov_ #-PTRsz, R6
call_ #__crt0_run_array
END_CRT_FUNC run_fini_array
#endif /* Lrun_fini_array */
#if Lrun_array
;; Note - this section is only included in the startup code of the application
;; if it is needed by one of the above run_*_array functions.
START_CRT_FUNC 1100 run_array
cmp_ R4, R5
jeq _msp430_run_done
mov_ @R4, R7
add_ R6, R4
call_ R7
br_ #__crt0_run_array
END_CRT_FUNC run_array
_msp430_run_done:
ret_
#endif /* Lrun_array */

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@ -1,4 +1,4 @@
/* Copyright (c) 2012-2013 Red Hat Incorporated.
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
@ -30,15 +30,17 @@
#include "memmodel.h"
.section ".crt_bss", "ax", @progbits
;; This function is responsible for initializing the contents of the
;; .bss section.
.global __crt0_init_bss
__crt0_init_bss:
START_CRT_FUNC 0100 init_bss
mov_ #__bssstart, R12
clr.w R13
mov.w #__bsssize, R14
mov_ #__bsssize, R14
#ifdef __MSP430X_LARGE__
clr.w R15 ; We assume that __bsssize is never > 64M
clr.w R15 ; We assume that __bsssize is never > 64K
#endif
call_ #memset
END_CRT_FUNC init_bss

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@ -0,0 +1,39 @@
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
The name of Red Hat Incorporated may not be used to endorse
or promote products derived from this software without specific
prior written permission.
This software is provided by the copyright holders and contributors
"AS IS" and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall Red Hat
incorporated be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage. */
#include "memmodel.h"
;; This function is responsible for calling exit once main has finished.
START_CRT_FUNC 0900 call_exit
call_ #_exit
END_CRT_FUNC call_exit

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@ -0,0 +1,51 @@
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
The name of Red Hat Incorporated may not be used to endorse
or promote products derived from this software without specific
prior written permission.
This software is provided by the copyright holders and contributors
"AS IS" and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall Red Hat
incorporated be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage. */
#ifdef __MSP430X_LARGE__
#include "memmodel.h"
;; This function is responsible for initializing the contents of the
;; .upper.bss section.
START_CRT_FUNC 0200 init_highbss
mov_ #__high_bssstart, R12
mov.w #0, R13
mov_ #__high_bsssize, R14
;; If __high_bsssize is zero then skip the call to memset.
;; This can happen if all of the bss data was placed into .either.bss.
cmp.w #0, R14
jeq 1f
call_ #memset
1:
END_CRT_FUNC init_highbss
#endif /* __MSP430X_LARGE__ */

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@ -0,0 +1,46 @@
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
The name of Red Hat Incorporated may not be used to endorse
or promote products derived from this software without specific
prior written permission.
This software is provided by the copyright holders and contributors
"AS IS" and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall Red Hat
incorporated be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage. */
#include "memmodel.h"
;; This function is responsible for initializing the contents of the
;; .bss section.
START_CRT_FUNC 0100 init_bss
mov_ #__bssstart, R12
clr.w R13
mov_ #__bsssize, R14
#ifdef __MSP430X_LARGE__
clr.w R15 ; We assume that __bsssize is never > 64K
#endif
call_ #memset
END_CRT_FUNC init_bss

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@ -0,0 +1,40 @@
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
The name of Red Hat Incorporated may not be used to endorse
or promote products derived from this software without specific
prior written permission.
This software is provided by the copyright holders and contributors
"AS IS" and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall Red Hat
incorporated be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage. */
#include "memmodel.h"
;; This function is always included and calls main().
START_CRT_FUNC 0800 call_main
clr.w R12 ; Set argc == 0
call_ #main
END_CRT_FUNC call_main

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@ -0,0 +1,71 @@
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
The name of Red Hat Incorporated may not be used to endorse
or promote products derived from this software without specific
prior written permission.
This software is provided by the copyright holders and contributors
"AS IS" and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall Red Hat
incorporated be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage. */
#ifdef __MSP430X_LARGE__
#include "memmodel.h"
;; This function is responsible for making sure that the
;; contents of the .upper.data section have their correct startup values.
;; If a copy of the .upper.data section is stored in ROM then this means
;; copying the contents into HIFRAM. If a copy of .upper.data is stored in a
;; shadow section in HIFRAM then this means copying from the shadow section
;; into the real section.
START_CRT_FUNC 0400 move_highdata
;; __rom_highdatacopysize may be zero. Test this first because
;; its value may come from the weak definitions above and we do
;; not want to access the memory at address 0 pointed to by the
;; weak definition of __upper_data_init.
mov.w #__rom_highdatacopysize, R14
cmp.w #0, R14
jeq 3f
/* Test our status word. */
cmpx.w #0, &__upper_data_init
jeq 1f
/* Status word is non-zero - copy from shadow into upper. */
mov_ #__high_datastart, R12
mov_ #__rom_highdatastart, R13
jmp 2f
1: /* Status word is zero. Copy from upper to shadow and change status word. */
movx.w #1, &__upper_data_init
mov_ #__rom_highdatastart, R12
mov_ #__high_datastart, R13
2: ;; __rom_highdatacopysize may be zero. memmove should cope.
mov.w #__rom_highdatacopysize, R14
call_ #memmove
3:
END_CRT_FUNC move_highdata
#endif /* __MSP430X_LARGE__ */

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@ -0,0 +1,50 @@
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
The name of Red Hat Incorporated may not be used to endorse
or promote products derived from this software without specific
prior written permission.
This software is provided by the copyright holders and contributors
"AS IS" and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall Red Hat
incorporated be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage. */
#include "memmodel.h"
;; This function is responsible for copying the
;; contents of the .data section from its load address (in ROM) to
;; its run-time address (in RAM).
START_CRT_FUNC 0300 movedata
mov_ #__datastart, R12
mov_ #__romdatastart, R13
;; memmove and memcpy do not currently work when src == dst
cmp_ R12, R13
jeq 1f
mov_ #__romdatacopysize, R14
call_ #memmove
1:
END_CRT_FUNC movedata

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@ -0,0 +1,48 @@
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
The name of Red Hat Incorporated may not be used to endorse
or promote products derived from this software without specific
prior written permission.
This software is provided by the copyright holders and contributors
"AS IS" and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall Red Hat
incorporated be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage. */
#include "memmodel.h"
;; Note - this section is only included in the startup code of the application
;; if it is needed by one of the above run_*_array functions.
START_CRT_FUNC 1100 run_array
cmp_ R4, R5
jeq _msp430_run_done
mov_ @R4, R7
add_ R6, R4
call_ R7
br_ #__crt0_run_array
END_CRT_FUNC run_array
_msp430_run_done:
ret_

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@ -0,0 +1,43 @@
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
The name of Red Hat Incorporated may not be used to endorse
or promote products derived from this software without specific
prior written permission.
This software is provided by the copyright holders and contributors
"AS IS" and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall Red Hat
incorporated be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage. */
#include "memmodel.h"
;; This function is responsible for setting up the arguments
;; required for __crt0_run_array, to run the functions in .fini_array.
START_CRT_FUNC 1000 run_fini_array
mov_ #__fini_array_start, R4
mov_ #__fini_array_end, R5
mov_ #-PTRsz, R6
call_ #__crt0_run_array
END_CRT_FUNC run_fini_array

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@ -0,0 +1,43 @@
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
The name of Red Hat Incorporated may not be used to endorse
or promote products derived from this software without specific
prior written permission.
This software is provided by the copyright holders and contributors
"AS IS" and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall Red Hat
incorporated be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage. */
#include "memmodel.h"
;; This function is responsible for setting up the arguments
;; required for __crt0_run_array, to run the functions in .init_array.
START_CRT_FUNC 0600 run_init_array
mov_ #__init_array_start, R4
mov_ #__init_array_end, R5
mov_ #PTRsz, R6
call_ #__crt0_run_array
END_CRT_FUNC run_init_array

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@ -0,0 +1,43 @@
/* Copyright (c) 2012-2015 Red Hat Incorporated.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
The name of Red Hat Incorporated may not be used to endorse
or promote products derived from this software without specific
prior written permission.
This software is provided by the copyright holders and contributors
"AS IS" and any express or implied warranties, including, but not
limited to, the implied warranties of merchantability and fitness for
a particular purpose are disclaimed. In no event shall Red Hat
incorporated be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage. */
#include "memmodel.h"
;; This function is responsible for setting up the arguments
;; required for __crt0_run_array, to run the functions in .preinit_array.
START_CRT_FUNC 0500 run_preinit_array
mov_ #__preinit_array_start, R4
mov_ #__preinit_array_end, R5
mov_ #PTRsz, R6
call_ #__crt0_run_array
END_CRT_FUNC run_preinit_array

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@ -40,10 +40,16 @@
#endif
/* Start a function in its own named and numbered section, so that it
can be subject to linker garbage collection. The numbers are used
to enforce link-time ordering of the sections. Note - the construction
of the symbol names is critical - they need to match the unresolved
symbol references created by the compiler and assembler. */
can be subject to linker garbage collection.
The linker links all .crt_* sections in asciibetical order at the same place.
So, the four digits in .crt_NNNN_xxx name are used to enforce link-time
ordering of the sections. Make sure to keep them in sequential order. The
first two digits are set in the files, the second two allow users to insert
code between our standard code fragments.
Note - the construction of the symbol names is critical - they need to match
the unresolved symbol references created by the compiler and assembler. */
.macro START_CRT_FUNC number name
.section .crt_\number\name,"ax",@progbits
.global __crt0_\name