LPC23XX的程序移植.doc

关于LPC24XX的程序移植
        近来单片机升级了，一下子进入32位时代，有点措手不及！还好，网络互相的现代，工程师不必从头开始，充分利用网络资源，加快开发进程。由于以前一直使用KEIL开发51单片机，使用方便，便于调试仿真。值得庆幸的是现在ARM型单片机也可以在KEIL中调试。可是网上大部分ARM实例是基于ADS的。直接移植过来就会一警告和错误。
  为了加快开发进程，还是选择移植借鉴部分实用例程。具体解决问题方法如下：
新推出的KEIL版开发工具RVMDK与老版ADS在工具架构组成上有以下不同：ARM编译器版本、调试器、软件仿真、以及调试单元。
   出现如下提示：
USBdma.h(128): warning:  #1-D: last line of file ends without a newline
compiling USBDriver.c...
USBHAL.h(40): warning:  #1-D: last line of file ends without a newline
USBdma.h(128): warning:  #1-D: last line of file ends without a newline
提示："文件结束了但没有空行"这个警告, 这是由RVMDK编译器产生的警告，所有程序文件最后一行必须有空行，也可不去理它。在提示处按一下回车就行了。
   Startup.s(214): warning: A1608W: MOV pc,<rn> instruction used, but BX <rn> is preferred
Startup.s(258): warning: A1608W: MOV pc,<rn> instruction used, but BX <rn> is preferred
由于编译器版本的变化，对应的编译选项也有所变化。将options for target中asm标签页里面的Eenable ARM/Thumb interworking复选框去掉，就不产生这样的告警信息啦，不过不知道这样做会影响什么！
也可以根据提示改为BX跳转。如果您的程序中存在ARM/Thumb指令相互调用的情况，那么使用BX指令能够返回到正确的处理器状态。而使用MOV指令则不能实现处理器状态的切换。所以keil编译器建议您使用BX指令。例如把MOV  PC, LR 改为BX  LR  。
fio_release.axf: Error: L6238E: startup.o(vectors) contains invalid call from '~PRES8' function to 'REQ8' function FIQ_Exception.
fio_release.axf: Error: L6238E: startup.o(vectors) contains invalid call from '~PRES8' function to 'REQ8' function TargetResetInit.
这是由于对目标文件进行链接时，ARM工具的连接器会严格检查各个文件（objects），判断它们是否复合ARM体系结构的ABI表准。由于RVCT与ADS编译链接工具所遵循的ARM ABI不同，所以将ADS的遗留工程直接移植到RVMDK并进行连接时，用户可能会遇到错误或者警告：新工具的ABI要求在函数调用时，系统必须保证堆栈指针8byte对齐，即每次进栈或者出栈的寄存器数目必须为偶数。这是为了能够更加高效的使用STM与LDR指令对“double”或者“long long”类型的数据进行访问。而老的ARM开发工具ADS并没有考虑到新的ARM内核架构，其ABI对于堆栈的操作仅仅要求4byte对齐。所以当用户将在ADS中编译连接成功的工程代码移植到RVMDK上，或者将老的、ADS遗留的目标文件、库文件在新工具RVMDK中进行连接时，RVMDK的连接器就会报出以上的错误。
解决方法如下：
在每个汇编文件的开头，添加“PRESERVE8”指令。

    AREA    vectors,CODE,READONLY之前加   PRESERVE8。

如下：
         AREA    vectors,CODE,READONLY       
         改为：
   PRESERVE8
  AREA    vectors,CODE,READONLY
检查汇编源码中的指令，确保堆栈操作指令是8byte对其的。ADS的遗留代码一次性将5个寄存器压栈，由于ARM的指令寄存器宽度为32位，即4byte，显然5个寄存器入栈之后，堆栈指针不能够满足64位，8byte对齐。为了解决这种情况，我们可以将另外一个并不需要压栈的寄存器，R12，同时压栈，这样当6个32位寄存器进栈之后，堆栈就能满足64位对齐了。
如： STMFD   SP!, {R0-R3, LR}改为：STMFD   SP!, {R0-R3, R12,LR}
好了通过以简单的更改，程序通过了。由于接触时间太短，分享的只是解决方法，详细部分还不太清楚。希望共同讨论！

Linker Error: L6238E: foo.o(.text) contains invalid call from '~PRES8' function to 'REQ8'
默认分类 2008-07-11 14:42:21 阅读86 评论0   字号：大中小 订阅
Linker Error: L6238E: foo.o(.text) contains invalid call from '~PRES8' function to 'REQ8' function foobar
Applies to: Assembler, Linker, RealView Developer Kit (RVDK) for OKI , RealView Developer Suite (RVDS) 2.0, RealView Developer Suite (RVDS) 2.1, RealView Developer Suite (RVDS) 2.2, RealView Development Suite (RVDS) 3.0, RealView Development Suite (RVDS) 3.1
This RVDS/RVCT linker error is given where a stack alignment conflict is detected in object code. The "ABI for the ARM Architecture" demands that code maintains 8-byte stack alignment at its interfaces. This allows efficient use of LDRD and STRD instructions (in ARM Architecture 5TE and later) to access 8-byte-aligned "double" and "long long" data types.
Symbols like '~PRES8' and 'REQ8' are "Build Attributes" of the objects.
· PRES8 means the object PREServes 8-byte alignment of the stack.
· ~PRES8 means the object does NOT preserve 8-byte alignment of the stack (~ meaning NOT).
· REQ8 means the object REQuires 8-byte alignment of the stack.
This link error typically occurs in two cases:
· where assembler code (that does not preserve 8-byte stack alignment) calls compiled C/C++ code (that requires 8-byte stack alignment), and
· when attempting to link legacy SDT/ADS objects with RVCT 2.x objects. Legacy SDT/ADS objects that do not have these attributes are treated as '~PRES8', even if they do actually happen to preserve 8-byte alignment.
For example:
Error: L6238E: foo.o(.text) contains invalid call from '~PRES8' function to 'REQ8' function foobar
This means that there is a function in the object foo.o (in the section named .text) that does not preserve 8-byte stack alignment, but which is trying to call function foobar that requires 8-byte stack alignment.
A similar warning that may be encountered, where the address of an external symbol is being referred to, is:
Warning: L6306W: '~PRES8' section foo.o(.text) should not use the address of 'REQ8' function foobar
Solutions
There are two possible approaches to dealing with this issue:
1) If you have access to all your source code and are allowed to rebuild it
In this case you should rebuild all your objects/libraries using the latest version of the compilation tools. Note that if you have any assembler files, you will need to:
i) check that all instructions preserve 8-byte stack alignment, and if necessary, correct them.
e.g. change:
STMFD sp!, {r0-r3, lr} ; push an odd number of registers
to:
STMFD sp!, {r0-r3, r12, lr} ; push an even number of registers
and:
ii) add the PRESERVE8 directive to the top of each assembler file.
e.g. change:
AREA Init, CODE, READONLY
to:
PRESERVE8
AREA Init, CODE, READONLY
(the PRES8 attribute applies to the whole object, not just the code section).
2) If you cannot rebuild all of your source code
If you have any legacy objects/libraries that cannot be rebuilt, either because you do not have the source code, or because the old objects must not be rebuilt (e.g. for qualification/certification reasons), then you must inspect the legacy objects to check whether they preserve 8-byte alignment or not. Use "fromelf -c" to disassemble the object code. C/C++ code compiled with ADS 1.1 or later will normally preserve 8-byte alignment, but assembled code will not.
If your objects do indeed preserve 8-byte alignment, then the linker error L6238E can be suppressed with the use of "--diag_suppress 6238" on the linker command line. By using this, you are effectively saying "I guarantee that these objects are PRES8". The linker warning L6306W is suppressible with "--diag_suppress 6306".
If you are linking with legacy objects/libraries then you should also read the information on the option "--apcs /adsabi" in the FAQ entry "Are legacy ADS objects/libraries compatible with RVCT 2.0 ?".