奢�2 (DSO) '

僥 5 � 5斬饇� �) 僥� 霤�.

9 �� 晴�� 賅� � � � 晦� 唸賅嵿��4 �� 闡 httpd � � � 賅闡 � � 賅 httpd � 摯� 鷏� 奢�2Dynamic Shared Objects, DSO)� 闡 � DSO 賅 �� 闡 � 闡 � 剪, Apache Extension Tool (apxs) �) $ 闡 � 6�

僥 DSO 賅 �)� 寡唳 � �

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�( 賅	�( '/th>
`mod_so`	`LoadModule`

9 �, � 闡 � �< mod_so.c� 賅 9 賅 �4�4晦 DSO� ' 賅 core� � � DSO� � 賅� �� 元� 賅 9 賅 � 僥 � configure --enable-module=shared � �) DSO� 闡 � 賅 mod_foo.so � DSO� 闡 � apache2.conf � mod_so LoadModule 跪4 �) � � � � 賅 �4�

9 賅(� �� 賅)� �) DSO � � 衙晦 apxs (APache eXtenSion)� � ' 嵿�� 嵿�� 9 虜� � DSO� �) 賅闡 � �) � � 9� � configure make install 9 C �� , DSO � 闡 � 晦 � 闡 � �� ; � apxs 嵿�� 晦斜 apxs� �) �) 9 寡牯� 虜� DSO ' � 闡 � � �; � 唳 �� 9 賅 � 闡 �

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Apache 2.2 DSO 晦� 穠 �5 �4

寡牯� 9 賅闡 � � � 唳 � � mod_foo.c� DSO mod_foo.so�:

$ ./configure --prefix=/path/to/install --enable-foo=shared $ make install
��  9 賅闡 � � � 唳 � � mod_foo.c� DSO mod_foo.so�:

$ ./configure --add-module=module_type:/path/to/3rdparty/mod_foo.c --enable-foo=shared $ make install
奢賅 $ �) 晦/em> 9� 掘1 唳

$ ./configure --enable-so $ make install
��  9 賅闡 � � � 唳 apxs� �) 9 虜� � mod_foo.c� DSO mod_foo.so�:

$ cd /path/to/3rdparty $ apxs -c mod_foo.c $ apxs -i -a -n foo mod_foo.la

賅唳 � 奢賅闡 �� apache2.conf LoadModule � �) 9� � 賅 �4�4 �

寡唳'

� 奢�2/em> (DSO) ��dynamic linking/loading)�� = 褻衙 � $ � 嵿�� 輿奢 �4�4 �' 晦�

爾 �' 寞� �4� � 嵿�� ld.so� � 嵿�� 4�4 唳0 , 元� � $ 嵿�� dlopen()/dlsym() � �� (loader) � � � �$ �) ' �4�4 唳0

羅' 唳 DSO� 爾 奢<4鼽�(shared libraries) � DSO �4鼽�� 鷏ㄧ�, � libfoo.so libfoo.so.1.2 � � �' �� 皞� /usr/lib) �, 闡 � �; 跪4 -lfoo� 輿 � 摯� 偽� �� ' � �4鼽� � � 霤褻�, 嵿�� ; � -R� ' ' 唳, 唳 LD_LIBRARY_PATH� ' 唳 � /usr/lib �� libfoo.so� 瓊斜鼽� � 嵿�� (' 跤瓊(unresolved)) 牯�(symbol) DSO 瓊

DSO 爾 � 嵿�� 牯� 瓊� 僥 (DSO� �,)� � = �4鼽��) 瓊晦炳� �� 牯� 瓊晦� �� 嵿�� ' DSO 牯� 瓊 � (� ld.so� 鷏� = 賅 � 嵿�� 裙 � = �) 奢 � �4鼽� =� � �4�4 � � �4鼽� =� 賅嵿�� $犒 � � libc.so � � �4鼽� �� 僥 � 奢 �

�' 唳 DSO� 爾 奢�2shared objects) � DSO /em>�� 鷏� , (�9 � foo.so��) � � � �� 爾嵿� 2 葬 9� � 嵿�� 偽�' � 嵿�� dlopen() �) DSO� 輿奢 ' �4�, � � 嵿�� DSO 牯� 瓊 � � � � 摯� � � � �4� DSO �4鼽�(� 襄, libc.so 賅牯�) DSO (' 跤瓊) 牯� 瓊斜 DSO �9 2� � 嵿�� 裙�� 牯� �

DSO API� �) 晦4 �'彰 � 嵿�� dlsym()� DSO � 牯� 瓊, � �) 晦 � �(dispatch) /em> � 元� �� 嵿�� ) 賅內� ' 瓊< � 掘褻 � 嵿�� 嵿�� ' �4�4 (斜曏薷�� ' �) � � 晦獄嵿�� 晦� � 晦唳 �� 4�

� DSO 掘褻� �$� 爾4�, 5 �� ' 嵿�� 晦 DSO� �) DSO� � 嵿�� 牯� 瓊 �4 ? DSO� � 嵿�� 牯� "� 瓊 �" (�4鼽� �) 嵿�� 賅艇�) �4鼽� � �� 賅 � ''� $' � 僥4 �� 牯�(global symbol) 爾 �$ � export)' 晦僥 DSO� �) DSO� �) � $ 嵿�� 元� 褔�� 賅牯� �$ � � � � � 輿敦憀t

奢<4鼽� DSO 寞 � 9� 敢漡� �羹� 奢剪賅 "� �4鼽�� ) �� 嵿�� 嵿�� 晦奢冕� �) '

1998 � $ �� 晦� � 晦 DSO 掘褻� �) �( � � (XS 掘褻 DynaLoader 賅 �) ) Perl 5, Netscape Server /em>� 僭 9 � 晦� � 晦賅 � �) � � 賅 9 �,晦� 偽嵿� �� 跡 �) 斬寞� �) 晦僥 1.3 �� 斜 9 � $ 賅 �4�4 DSO� �) � �'!

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� DSO� �) � ��

� � 煦$ 闡 � configure � apache2.conf LoadModule �) � $ 唸 �� 9 �彰元� �($ �� SSL �, 5 �� 晦�� [mod_perl, PHP3] /em>)� �
� � �� 賅 �) � � 5 晦 � � 9 � � � �� PHP3, mod_perl, mod_fastcgi /em> 6� � �� 
DSO apxs� �'� 9 虜� � � apxs -i apache2ctl restart 跪4� �� 賅 � � $ 9 � � � � 9 賅 ��

DSO ��

嵿�� 輿奢 =� � �4�4 晦� '' �羹� � 僥賅 � DSO� �)
�� 牯� 瓊< � 僥 � 20% �
� 9董(position independent code, PIC) 僥輿'(absolute addressing)爾 � 輿'(relative addressing) 犒! �� 晦 �� 5%
DSO 賅元� DSO晦 �4鼽�(ld -lfoo) 裙 � 晦僥 (� � ELF晦 � ''� a.out晦 � 爾晦� '' 賅 "� 賅 DSO� �) 元� �� DSO � 闡 � 賅 9 �,婁 9 �, �) C �4鼽�(libc) 元� / �4鼽�, 9董� � �4鼽� 蘋4(libfoo.a) 牯�� ) 元� =� �) 元� 9 �, 斜霤褻', dlopen()� ' =� �4�,

奢 �2 (DSO) '

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奢�2 (DSO) '