問題原因：我所使用的 tool chain arm-2009q3，預設會假設 target 為 armv5te架構
解決方法：
1. 先登入 Target 端 console，確認 cpu info
1 # cat /proc/cpuinfo2 Processor : ARMv6-compatible processor rev 5 (v6l)
3 BogoMIPS : 526.25
4 Features : swp half fastmult edsp java
5 CPU implementer : 0x41
6 CPU architecture: 6TEJ
7 CPU variant : 0x1
8 CPU part : 0xb36
9 CPU revision : 5
10
11 Hardware : Coconut12 Revision : 13ec301113 Serial : 0000000000000000
2. 確認目前 arm-none-linux-gnueabi-gcc 的預設架構
1 $ arm-none-linux-gnueabi-gcc -Q --help=target
2 The following options are target specific:
3 -falign-arrays [disabled]
4 -mabi=
5 -mabort-on-noreturn [disabled]
6 -mapcs [disabled]
7 -mapcs-float [disabled]
8 -mapcs-frame [disabled]
9 -mapcs-reentrant [disabled]
10 -mapcs-stack-check [disabled]
11 -march= armv5te
12 -marm [enabled]
13 -mbig-endian [disabled]
14 -mcallee-super-interworking [disabled]
15 -mcaller-super-interworking [disabled]
16 -mcirrus-fix-invalid-insns [disabled]
17 -mcpu=
18 -mfix-cortex-m3-ldrd [enabled]
19 -mfix-janus-2cc [disabled]
20 -mfloat-abi=
21 -mfp16-format=
22 -mfp=
23 -mfpe [disabled]
24 -mfpe=
25 -mfpu=
26 -mglibc [enabled]
27 -mhard-float [disabled]
28 -mlittle-endian [enabled]
29 -mlong-calls [disabled]
30 -mlow-irq-latency [disabled]
31 -mmarvell-div [disabled]
32 -mpic-register=
33 -mpoke-function-name [disabled]
34 -msched-prolog [enabled]
35 -msingle-pic-base [disabled]
36 -msoft-float [disabled]
37 -mstructure-size-boundary=
38 -mthumb [disabled]
39 -mthumb-interwork [enabled]
40 -mtp=
41 -mtpcs-frame [disabled]
42 -mtpcs-leaf-frame [disabled]
43 -mtune=
44 -muclibc [disabled]
45 -mvectorize-with-neon-quad [disabled]
46 -mword-relocations [disabled]
47 -mwords-little-endian [disabled]
很明顯，若使用預設值 armv5te進行編譯，則 arm 架構不符。3. 如何確認現在正在使用的 gdbserver 其適用的arm架構呢?
$arm-none-linux-gnueabi-readelf -A ./gdbserver
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "5TE"
Tag_CPU_arch: v5TE
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-1
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align8_needed: Yes
Tag_ABI_align8_preserved: Yes, except leaf SP
Tag_ABI_enum_size: int
4 因此在重新編譯 gdbserver 時應該要指定 armv6，舉例如下：
~/gdb/gdb-7.9/gdb/gdbserver$./configure --build=i686-pc-linux-gnu --host=arm-none-linux-gnueabi --target=arm-none-linux-gnueabi CROSS_COMPILE=arm-none-linux-gnueabi- CFLAGS='-g -O2 -march=armv6 -mtune=arm1136j-s'
編譯方式可參考此篇 。是否正確編譯成功，可透過 readelf 來檢視，如下：
&arm-none-linux-gnueabi-readelf -A ./gdbserver
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "6"
Tag_CPU_arch: v6
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-1
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align8_needed: Yes
Tag_ABI_align8_preserved: Yes, except leaf SP
Tag_ABI_enum_size: int
主要是編譯成機器語言時，可能會使用不同的instruction set或call convention，可能造成執行時的錯誤。其中差異可以參考此篇討論。6. 編譯 gdb
編譯方式如下
$./configure --target=arm-none-linux-gnueabi
$ make
不過這樣編譯出來的 gdb，在進行遠端除錯時，會出現以下錯誤訊息
"warning: Can not parse XML target description; XML support was disabled at compile time"
手動安裝 expat，重新編譯gdb便可解決，步驟如下：
可從此處下載原始碼 http://sourceforge.net/projects/expat/files/latest/download
$ tar zxvf expat-2.1.0.tar.gz
$ cd expat-2.1.0
$ ./configure
$ make;make install
另外支援 python script 會方便許多，因此我個人偏好使用下列這個編譯方式
$ sudo apt-get install python2.7-dev
$./configure --target=arm-none-linux-gnueabi --with-expat --with-python
$ make
註：若編譯的是 gdb-7.1，其 python 支援的功能是有限制的
http://stackoverflow.com/questions/8986589/how-to-get-output-from-gdb-execute-in-pythongdb-gdb-7-1
7. 若不使用 gdbserver，要直接編譯一個在 target system 執行的 gdb，需要先編譯 termcap，可參考下列設定
Build termcap
./configure --build=i686-pc-linux-gnu --host=arm-linux-gnueabihf --target=arm-linux-gnueabihf CROSS_COMPILE=arm-linux-gnueabihf- --prefix=/home/albert/tools/termcap
Build gdb
./configure --build=i686-pc-linux-gnu --host=arm-none-linux-gnueabi --target=arm-none-linux-gnueabi CROSS_COMPILE=arm-none-linux-gnueabi- CFLAGS='-g -O2 -I/home/albert/tools/termcap/include' LDFLAGS='-static -L/home/albert/tools/termcap/lib' CPPFLAGS='-I/home/albert/tools/termcap/include'
Reference:
http://ftp.gnu.org/gnu/gdb/
https://gcc.gnu.org/onlinedocs/gcc/ARM-Options.html
https://lists.debian.org/debian-arm/2011/11/msg00043.html
http://blog.csdn.net/a_ran/article/details/38404483
http://www.360doc.com/content/12/0312/23/532901_193884753.shtml
http://www.360doc.com/content/12/0312/23/532901_193884753.shtml
http://stackoverflow.com/questions/4381102/differences-between-arm-architectures-from-a-c-programmers-perspective
http://www.it.uom.gr/teaching/gcc_manuals/onlinedocs/gdb_35.html
http://lists.gnu.org/archive/html/bug-gnu-emacs/2001-11/msg00579.html
