Question

使用不可重定位的汇编程序代码链接从来没有问题直到gcc 6.2.0。我不知道盯着这个的确切版本，但是使用gcc 5.4.0（及以下版本），这有效：

$ gcc -o httpget ../obj/httpget.o ../../../lib/libribs2_ssl.a -lssl -lcrypto

然而，使用gcc 6.2.0：

$ gcc -o httpget ../obj/httpget.o ../../../lib/libribs2_ssl.a -lssl -lcrypto
/usr/bin/ld: ../../../lib/libribs2_ssl.a(context_asm.o): relocation R_X86_64_32S against symbol `current_ctx' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Nonrepresentable section on output
collect2: error: ld returned 1 exit status

尝试强制静态链接会产生另一个问题：

$ gcc -static -o httpget ../obj/httpget.o ../../../lib/libribs2_ssl.a -lssl -lcrypto -ldl
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libcrypto.a(dso_dlfcn.o): In function `dlfcn_globallookup':
(.text+0x11): warning: Using 'dlopen' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
../obj/httpget.o: In function `main':
/home/nir/ribs2/examples/httpget/src/httpget.c:194: warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking

使用gethostbyname（）时程序会出现段错误（但不是这样）

尝试混合静态和动态也不起作用。

$ gcc -o httpget -Wl,-Bstatic ../obj/httpget.o ../../../lib/libribs2_ssl.a -Wl,-Bdynamic -lssl -lcrypto
/usr/bin/ld: ../../../lib/libribs2_ssl.a(context_asm.o): relocation R_X86_64_32S against symbol `current_ctx' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Nonrepresentable section on output
collect2: error: ld returned 1 exit status

有什么想法吗？链接到项目：https://github.com/niryeffet/ribs2

Answer 1

感谢来自@Jester的提示：向LDFLAGS添加-no-pie（不是-fno-PIE）解决了这个问题。

gcc -no-pie -o httpget ../obj/httpget.o ../../../lib/libribs2_ssl.a -lssl -lcrypto

此更改也适用于gcc 5.4。似乎默认情况已经改变。

<强>更新

这解释了它。来自https://wiki.ubuntu.com/SecurityTeam/PIE

在Ubuntu 16.10中，作为额外的编译器强化措施，我们已经完成了默认情况下，在amd64和ppc64le上启用PIE和立即绑定。这极大地提高了ASLR在这些平台上的有效性。

gcc 6.2.0是否正在尝试创建共享对象？

1 个答案: