gcc - Libffi 可以为 Cortex-M3 构建吗？

Question

我正在尝试使用 GCC 为 Cortex-M3 处理器构建外部函数接口(interface)库。根据http://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html :

-mthumb
Generate code for the Thumb instruction set. The default is to use the 32-bit ARM instruction set. This option automatically enables either 16-bit Thumb-1 or mixed 16/32-bit Thumb-2 instructions based on the -mcpu=name and -march=name options. This option is not passed to the assembler. If you want to force assembler files to be interpreted as Thumb code, either add a `.thumb' directive to the source or pass the -mthumb option directly to the assembler by prefixing it with -Wa.

我已经尝试将各种不同的参数传递给汇编程序，但似乎无法弄清楚。典型输出如下:

Building file: ../source/ffi/sysv.S
Invoking: GCC Assembler
arm-bare_newlib_cortex_m3_nommu-eabi-gcc -Wa,-mthumb-interwork -I"/home/neil/m3projects/robovero/firmware/include" -o"source/ffi/sysv.o" "../source/ffi/sysv.S"
../source/ffi/sysv.S: Assembler messages:
../source/ffi/sysv.S:145: Error: selected processor does not support ARM opcodes
../source/ffi/sysv.S:147: Error: attempt to use an ARM instruction on a Thumb-only processor -- `stmfd sp!,{r0-r3,fp,lr}'
...

我可以在不成为汇编专家的情况下在 Cortex-M3 上使用 libffi 吗？

可能值得注意的是，当我直接调用 arm-bare_newlib_cortex_m3_nommu-eabi-as 时，我得到了不同的错误。

Answer 1

我修改了sysV.S如下，错误是“.arm”指令引起的，使用cortex-m3时，应该注释掉。

#ifdef __ARM_ARCH_7M__ /* cortex-m3 */
#undef __THUMB_INTERWORK__
#endif

#if __ARM_ARCH__ >= 5
# define call_reg(x)    blx x
#elif defined (__ARM_ARCH_4T__)
# define call_reg(x)    mov lr, pc ; bx x
# if defined(__thumb__) || defined(__THUMB_INTERWORK__)
#  define __INTERWORKING__
# endif
#else
# define call_reg(x)    mov lr, pc ; mov    pc, x
#endif

/* Conditionally compile unwinder directives.  */
#ifdef __ARM_EABI__
#define UNWIND
#else
#define UNWIND @
#endif  


#if defined(__thumb__) && !defined(__THUMB_INTERWORK__)
.macro  ARM_FUNC_START name
    .text
    .align 0
    .thumb
    .thumb_func
#ifdef __APPLE__
    ENTRY($0)
#else
    ENTRY(\name)
#endif
#ifndef __ARM_ARCH_7M__ /* not cortex-m3 */
    bx  pc
    nop
    .arm
#endif
    UNWIND .fnstart
/* A hook to tell gdb that we've switched to ARM mode.  Also used to call
   directly from other local arm routines.  */
#ifdef __APPLE__
_L__$0:
#else
_L__\name:
#endif
.endm