自己编译Android gdbserver（解决运行 gdbserver时 Segmentation fault 问题）
一、引言
使用Android 预装 gdbserver 调试 动态库时出现，Segmentation fault错误。不得不使用现有编译链重新编译一份gdbserver。多谢Android - How-to Rebuild gdbserver这篇文章，参考这篇文章我的解决过程如下。
这里要强调一点：下面编译sysroot时sysroot的目标路径，和编译gdbserver时指定的sysroot路径，一定要使用[绝对路径]。我编译过程中，曾因未使用绝对路径浪费不少精力。
二、开发环境
Ubuntu 11.04
编译通过的Android 2.3 源码
三、解决过程
1、因已经有了Android 2.3源码，省去下载源码并编译的漫长过程。
#设置Android源码目录为环境变量：$ANDROID_SRC
simba@simba-Vostro-3400:~$ export ANDROID_SRC=/home/simba/neptune/android_2.3
2、下载gdb源码，并打补丁
simba@simba-Vostro-3400:~$ mkdir gdb_build
simba@simba-Vostro-3400:~/neptune/gdb_src$ git clone https://android.googlesource.com/toolchain/gdb.git
#坐等下载完毕，然后...
#将以下保存成.patch文件
diff --git a/gdb-7.1.x/gdb/gdbserver/Makefile.in b/gdb-7.1.x/gdb/gdbserver/Makefile.in
index 5bf82e2..488bfb6 100644
--- a/gdb-7.1.x/gdb/gdbserver/Makefile.in
+++ b/gdb-7.1.x/gdb/gdbserver/Makefile.in
@@ -176,13 +176,13 @@ clean-info:
gdbserver$(EXEEXT): $(OBS) ${ADD_DEPS} ${CDEPS}
rm -f gdbserver$(EXEEXT)
- ${CC-LD} $(INTERNAL_CFLAGS) $(INTERNAL_LDFLAGS) -o gdbserver$(EXEEXT) $(OBS) \
- $(GDBSERVER_LIBS) $(XM_CLIBS)
+ ${CC-LD} $(INTERNAL_CFLAGS) -o gdbserver$(EXEEXT) $(OBS) \
+ $(GDBSERVER_LIBS) $(XM_CLIBS) $(INTERNAL_LDFLAGS)
gdbreplay$(EXEEXT): $(GDBREPLAY_OBS)
rm -f gdbreplay$(EXEEXT)
- ${CC-LD} $(INTERNAL_CFLAGS) $(INTERNAL_LDFLAGS) -o gdbreplay$(EXEEXT) $(GDBREPLAY_OBS) \
- $(XM_CLIBS)
+ ${CC-LD} $(INTERNAL_CFLAGS) -o gdbreplay$(EXEEXT) $(GDBREPLAY_OBS) \
+ $(XM_CLIBS) $(INTERNAL_LDFLAGS)
# Put the proper machine-specific files first, so M-. on a machine
# specific routine gets the one for the correct machine.
diff --git a/gdb-7.1.x/gdb/gdbserver/linux-arm-low.c b/gdb-7.1.x/gdb/gdbserver/linux-arm-low.c
index 54668f8..7a78cce 100644
--- a/gdb-7.1.x/gdb/gdbserver/linux-arm-low.c
+++ b/gdb-7.1.x/gdb/gdbserver/linux-arm-low.c
@@ -43,10 +43,7 @@ void init_registers_arm_with_neon (void);
# define PTRACE_SETWMMXREGS 19
#endif
-#ifndef PTRACE_GETVFPREGS
-# define PTRACE_GETVFPREGS 27
# define PTRACE_SETVFPREGS 28
-#endif
static unsigned long arm_hwcap;
#打补丁
simba@simba-Vostro-3400:~/gdb_build$ cd gdb/
simba@simba-Vostro-3400:~/gdb_build/gdb$ patch -p1 <./gdb_patch.patch
3、下载build源码
simba@simba-Vostro-3400:~/gdb_build$ git clone https://android.googlesource.com/toolchain/build.git#坐等下载完毕，然后...
#注意此处sysroot的目标目录一定要使用绝对路径，否则sysroot不能正常生成，之后编译gdbserver时会报错。
4.修改编译脚本
#备份并修改build-gdbserver.sh
simba@simba-Vostro-3400:~/gdb_build$ gedit $ANDROID_SRC/ndk/build/tools/build-gdbserver.sh
#以下红字部分为添加内容，目的是注释掉部分代码
<<NOT_NEEDED
# Remove libthread_db to ensure we use exactly the one we want.
rm -f $BUILD_SYSROOT/usr/lib/libthread_db*
rm -f $BUILD_SYSROOT/usr/include/thread_db.h
if [ "$NOTHREADS" != "yes" ] ; then
# We're going to rebuild libthread_db.o from its source
# that is under sources/android/libthread_db and place its header
# and object file into the build sysroot.
LIBTHREAD_DB_DIR=$ANDROID_NDK_ROOT/sources/android/libthread_db/gdb-$GDB_VERSION
if [ ! -d "$LIBTHREAD_DB_DIR" ] ; then
dump "ERROR: Missing directory: $LIBTHREAD_DB_DIR"
exit 1
fi
# Small trick, to avoid calling ar, we store the single object file
# with an .a suffix. The linker will handle that seamlessly.
run cp $LIBTHREAD_DB_DIR/thread_db.h $BUILD_SYSROOT/usr/include/
run $TOOLCHAIN_PREFIX-gcc --sysroot=$BUILD_SYSROOT -o $BUILD_SYSROOT/usr/lib/libthread_db.a -c $LIBTHREAD_DB_DIR/libthread_db.c
if [ $? != 0 ] ; then
dump "ERROR: Could not compile libthread_db.c!"
exit 1
fi
fi
NOT_NEEDED
get_toolchain_install ()
{
echo "$1/toolchains/$TOOLCHAIN/prebuilt/$HOST_TAG"
}
修改为：
get_toolchain_install ()
{
echo "$1/prebuilt/$HOST_TAG/toolchain/$TOOLCHAIN"
}