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osd-contiki/cpu/cc2538/startup-gcc.c
Benoît Thébaudeau afe5d0403d cc2538: Build without the Contiki target library 
The GNU linker ld searches and processes libraries and object files in
the order they are specified. Library files are archive files whose
members are object files. The linker handles an archive file by scanning
through it for members that define symbols that have so far been
referenced but not defined. But an ordinary object file is linked in the
usual fashion.

The C library is implicitly linked after all object files and libraries
specified on the command line.

Because of that, if the C library depends on the Contiki target library,
e.g. for the implementation of system calls, then these dependencies are
not linked, which results in undefined references. Actually, the Contiki
target library also needs the C library, hence a circular dependency
between these libraries, which means that explicitly adding -lc anywhere
on the command line can not help. The only solution in that case is to
pass these libraries to ld between --start-group and --end-group.
Archives grouped in this way are searched repeatedly by the linker until
no new undefined references are created.

This archive grouping option has a significant performance cost for the
linking stage. Moreover, having to use it and to pass -lc explicitly on
the command line is unusual, which is disturbing and more complicated
for users needing the C library to depend on the Contiki target library.
The same would be true for circular dependencies between the Contiki
target library and any other library.

Another issue with the Contiki target library is that it may alter the
apparent behavior of the weak vs. strong symbols, because of the way ld
handles archives, which may make it discard archive object files
containing strong versions of referenced symbols:
 - If a symbol has a weak and a strong version in this library, both
   inside the same object file, then the linker uses the strong
   definition.
 - If a weak symbol in this library has a strong counterpart in an
   object file outside, then the linker uses the strong definition.
 - If a strong symbol in this library is inside an object file
   containing other referenced symbols, and has a weak counterpart
   anywhere, then the linker uses the strong definition.
 - If a strong symbol in this library is the only symbol referenced in
   its object file, and has a weak counterpart in an object file
   outside, then the linker uses the strong definition if this library
   is linked first, and the weak one otherwise.
 - If a strong symbol in this library is the only symbol referenced in
   its object file, and has a weak counterpart in another object file in
   this library, then the linker uses the definition from the first of
   these objects added when creating this archive.
 - If a symbol has a weak and a strong version, one in this library, and
   the other in another library, then the rules are the same as if both
   were in the Contiki target library.

The existence of cases where the linker uses a weak symbol despite the
presence of its strong counterpart in the sources compiled then passed
to the linker is very error-prone, all the more this behavior depends on
the order the object and archive files are passed on the command lines,
which may just result from the order of source files in lists where it
apparently does not matter. Such cases would be needed in the future,
e.g. to define weak default implementations of some system calls that
can be overridden by platform-specific implementations, both ending up
in the Contiki target library. There was already such a case used to
define the UART and USB ISRs as weak aliases of default_handler(),
relying on this implicit unusual behavior to keep default_handler() if
the UART or USB driver was unused, which was dangerous.

Since the Contiki target library was only used as an intermediate file
during the build, the current commit fixes these issues by simply
directly using the object files instead of building an intermediate
archive from them.

The CONTIKI_OBJECTFILES make variable would be incomplete if it were
used as a simple prerequisite in the %.elf rule in Makefile.cc2538,
because other object files are added to it after this rule. That's why
.SECONDEXPANSION is used to defer its expansion. Another solution would
have been to split Makefile.cc2538, with the variable assignments kept
in it, and the rule definitions moved to Makefile.customrules-cc2538,
but this would have required to add Makefile.customrules-<target> files
to all CC2538 platforms, only to include Makefile.customrules-cc2538.
The solution used here is much simpler.

Because the UART and USB ISRs were weak aliases of default_handler(),
this change would imply that these ISRs would always be used by the
linker instead of default_handler(), even if their drivers were
configured as unused with UART_CONF_ENABLE and USB_SERIAL_CONF_ENABLE,
which would be wrong. This commit fixes this issue by removing these
weak aliases and putting either these ISRs or default_handler() in the
vector table, depending on the configuration. Weak aliases are elegant,
but Contiki's build system does not currently allow to automatically
build or not source files depending on the configuration, so keeping
these weak aliases would have required to add #if constructs somewhere
in the source code, which would have broken their elegance and made them
pointless.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau.dev@gmail.com>
2015-06-05 21:55:51 +02:00

331 lines
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/*
* Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
*
*
* 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.
*
* Neither the name of Texas Instruments Incorporated nor the names of
* its contributors may 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 THE COPYRIGHT
* OWNER OR CONTRIBUTORS 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.
*/
/**
* \addtogroup cc2538
* @{
*
* \file
* Startup code for the cc2538 chip, to be used when building with gcc
*/
#include "contiki.h"
#include "reg.h"
#include "flash-cca.h"
#include "sys-ctrl.h"
#include "rom-util.h"
#include <stdint.h>
/*---------------------------------------------------------------------------*/
extern int main(void);
/*---------------------------------------------------------------------------*/
/* System handlers provided here */
void reset_handler(void);
void nmi_handler(void);
void default_handler(void);
/* System Handler and ISR prototypes implemented elsewhere */
void clock_isr(void); /* SysTick Handler */
void gpio_port_a_isr(void);
void gpio_port_b_isr(void);
void gpio_port_c_isr(void);
void gpio_port_d_isr(void);
void rtimer_isr(void);
void cc2538_rf_rx_tx_isr(void);
void cc2538_rf_err_isr(void);
void udma_isr(void);
void udma_err_isr(void);
void crypto_isr(void);
/* Link in the USB ISR only if USB is enabled */
#if USB_SERIAL_CONF_ENABLE
void usb_isr(void);
#else
#define usb_isr default_handler
#endif
/* Likewise for the UART[01] ISRs */
#if UART_CONF_ENABLE
void uart0_isr(void);
void uart1_isr(void);
#else /* UART_CONF_ENABLE */
#define uart0_isr default_handler
#define uart1_isr default_handler
#endif /* UART_CONF_ENABLE */
/* Boot Loader Backdoor selection */
#if FLASH_CCA_CONF_BOOTLDR_BACKDOOR
/* Backdoor enabled */
#if FLASH_CCA_CONF_BOOTLDR_BACKDOOR_ACTIVE_HIGH
#define FLASH_CCA_BOOTLDR_CFG_ACTIVE_LEVEL FLASH_CCA_BOOTLDR_CFG_ACTIVE_HIGH
#else
#define FLASH_CCA_BOOTLDR_CFG_ACTIVE_LEVEL 0
#endif
#if ((FLASH_CCA_CONF_BOOTLDR_BACKDOOR_PORT_A_PIN < 0) || (FLASH_CCA_CONF_BOOTLDR_BACKDOOR_PORT_A_PIN > 7))
#error Invalid boot loader backdoor pin. Please set FLASH_CCA_CONF_BOOTLDR_BACKDOOR_PORT_A_PIN between 0 and 7 (indicating PA0 - PA7).
#endif
#define FLASH_CCA_BOOTLDR_CFG (FLASH_CCA_BOOTLDR_CFG_ENABLE \
| FLASH_CCA_BOOTLDR_CFG_ACTIVE_LEVEL \
| (FLASH_CCA_CONF_BOOTLDR_BACKDOOR_PORT_A_PIN << FLASH_CCA_BOOTLDR_CFG_PORT_A_PIN_S))
#else
#define FLASH_CCA_BOOTLDR_CFG FLASH_CCA_BOOTLDR_CFG_DISABLE
#endif
/*---------------------------------------------------------------------------*/
/* Allocate stack space */
static unsigned long stack[512] __attribute__ ((section(".stack")));
/*---------------------------------------------------------------------------*/
/* Linker construct indicating .text section location */
extern uint8_t _text[0];
/*---------------------------------------------------------------------------*/
__attribute__ ((section(".flashcca"), used))
const flash_cca_lock_page_t __cca = {
FLASH_CCA_BOOTLDR_CFG, /* Boot loader backdoor configuration */
FLASH_CCA_IMAGE_VALID, /* Image valid */
&_text, /* Vector table located at the start of .text */
/* Unlock all pages and debug */
{ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }
};
/*---------------------------------------------------------------------------*/
__attribute__ ((section(".vectors"), used))
void(*const vectors[])(void) =
{
(void (*)(void))((unsigned long)stack + sizeof(stack)), /* Stack pointer */
reset_handler, /* Reset handler */
nmi_handler, /* The NMI handler */
default_handler, /* The hard fault handler */
default_handler, /* 4 The MPU fault handler */
default_handler, /* 5 The bus fault handler */
default_handler, /* 6 The usage fault handler */
0, /* 7 Reserved */
0, /* 8 Reserved */
0, /* 9 Reserved */
0, /* 10 Reserved */
default_handler, /* 11 SVCall handler */
default_handler, /* 12 Debug monitor handler */
0, /* 13 Reserved */
default_handler, /* 14 The PendSV handler */
clock_isr, /* 15 The SysTick handler */
gpio_port_a_isr, /* 16 GPIO Port A */
gpio_port_b_isr, /* 17 GPIO Port B */
gpio_port_c_isr, /* 18 GPIO Port C */
gpio_port_d_isr, /* 19 GPIO Port D */
0, /* 20 none */
uart0_isr, /* 21 UART0 Rx and Tx */
uart1_isr, /* 22 UART1 Rx and Tx */
default_handler, /* 23 SSI0 Rx and Tx */
default_handler, /* 24 I2C Master and Slave */
0, /* 25 Reserved */
0, /* 26 Reserved */
0, /* 27 Reserved */
0, /* 28 Reserved */
0, /* 29 Reserved */
default_handler, /* 30 ADC Sequence 0 */
0, /* 31 Reserved */
0, /* 32 Reserved */
0, /* 33 Reserved */
default_handler, /* 34 Watchdog timer, timer 0 */
default_handler, /* 35 Timer 0 subtimer A */
default_handler, /* 36 Timer 0 subtimer B */
default_handler, /* 37 Timer 1 subtimer A */
default_handler, /* 38 Timer 1 subtimer B */
default_handler, /* 39 Timer 2 subtimer A */
default_handler, /* 40 Timer 2 subtimer B */
default_handler, /* 41 Analog Comparator 0 */
default_handler, /* 42 RFCore Rx/Tx (Alternate) */
default_handler, /* 43 RFCore Error (Alternate) */
default_handler, /* 44 System Control */
default_handler, /* 45 FLASH Control */
default_handler, /* 46 AES (Alternate) */
default_handler, /* 47 PKA (Alternate) */
default_handler, /* 48 SM Timer (Alternate) */
default_handler, /* 49 MacTimer (Alternate) */
default_handler, /* 50 SSI1 Rx and Tx */
default_handler, /* 51 Timer 3 subtimer A */
default_handler, /* 52 Timer 3 subtimer B */
0, /* 53 Reserved */
0, /* 54 Reserved */
0, /* 55 Reserved */
0, /* 56 Reserved */
0, /* 57 Reserved */
0, /* 58 Reserved */
0, /* 59 Reserved */
0, /* 60 Reserved */
0, /* 61 Reserved */
udma_isr, /* 62 uDMA */
udma_err_isr, /* 63 uDMA Error */
0, /* 64 64-155 are not in use */
0, /* 65 */
0, /* 66 */
0, /* 67 */
0, /* 68 */
0, /* 69 */
0, /* 70 */
0, /* 71 */
0, /* 72 */
0, /* 73 */
0, /* 74 */
0, /* 75 */
0, /* 76 */
0, /* 77 */
0, /* 78 */
0, /* 79 */
0, /* 80 */
0, /* 81 */
0, /* 82 */
0, /* 83 */
0, /* 84 */
0, /* 85 */
0, /* 86 */
0, /* 87 */
0, /* 88 */
0, /* 89 */
0, /* 90 */
0, /* 91 */
0, /* 92 */
0, /* 93 */
0, /* 94 */
0, /* 95 */
0, /* 96 */
0, /* 97 */
0, /* 98 */
0, /* 99 */
0, /* 100 */
0, /* 101 */
0, /* 102 */
0, /* 103 */
0, /* 104 */
0, /* 105 */
0, /* 106 */
0, /* 107 */
0, /* 108 */
0, /* 109 */
0, /* 110 */
0, /* 111 */
0, /* 112 */
0, /* 113 */
0, /* 114 */
0, /* 115 */
0, /* 116 */
0, /* 117 */
0, /* 118 */
0, /* 119 */
0, /* 120 */
0, /* 121 */
0, /* 122 */
0, /* 123 */
0, /* 124 */
0, /* 125 */
0, /* 126 */
0, /* 127 */
0, /* 128 */
0, /* 129 */
0, /* 130 */
0, /* 131 */
0, /* 132 */
0, /* 133 */
0, /* 134 */
0, /* 135 */
0, /* 136 */
0, /* 137 */
0, /* 138 */
0, /* 139 */
0, /* 140 */
0, /* 141 */
0, /* 142 */
0, /* 143 */
0, /* 144 */
0, /* 145 */
0, /* 146 */
0, /* 147 */
0, /* 148 */
0, /* 149 */
0, /* 150 */
0, /* 151 */
0, /* 152 */
0, /* 153 */
0, /* 154 */
0, /* 155 */
usb_isr, /* 156 USB */
cc2538_rf_rx_tx_isr, /* 157 RFCORE RX/TX */
cc2538_rf_err_isr, /* 158 RFCORE Error */
crypto_isr, /* 159 AES */
default_handler, /* 160 PKA */
rtimer_isr, /* 161 SM Timer */
default_handler, /* 162 MACTimer */
};
/*---------------------------------------------------------------------------*/
/* Linker constructs indicating .data and .bss segment locations */
extern uint8_t _ldata;
extern uint8_t _data;
extern uint8_t _edata;
extern uint8_t _bss;
extern uint8_t _ebss;
/*---------------------------------------------------------------------------*/
/* Weak interrupt handlers. */
void
nmi_handler(void)
{
reset_handler();
while(1);
}
/*---------------------------------------------------------------------------*/
void
default_handler(void)
{
while(1);
}
/*---------------------------------------------------------------------------*/
void
reset_handler(void)
{
REG(SYS_CTRL_EMUOVR) = 0xFF;
/* Copy the data segment initializers from flash to SRAM. */
rom_util_memcpy(&_data, &_ldata, &_edata - &_data);
/* Zero-fill the bss segment. */
rom_util_memset(&_bss, 0, &_ebss - &_bss);
/* call the application's entry point. */
main();
/* End here if main () returns */
while(1);
}
/*---------------------------------------------------------------------------*/
/** @} */
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