使独立卷曲导致段错误

Question

我想为具有非常旧的libc版本的嵌入式系统构建一个独立版本的`curl而没有任何库依赖(甚至是libc).

从当前的curl github,我使用以下命令配置编译:

./configure --disable-shared --enable-static-nss --prefix=/tmp/curl LDFLAGS='-static -static-libgcc -Wl,-Bstatic -lc' LIBS='-lc -lssl -lcrypto -lz -ldl'
[...]
curl version:     7.50.2-DEV
  Host setup:       x86_64-pc-linux-gnu
  Install prefix:   /tmp/curl
  Compiler:         gcc
  SSL support:      enabled (OpenSSL)
  SSH support:      no      (--with-libssh2)
  zlib support:     enabled
  GSS-API support:  no      (--with-gssapi)
  TLS-SRP support:  enabled
  resolver:         default (--enable-ares / --enable-threaded-resolver)
  IPv6 support:     enabled
  Unix sockets support: enabled
  IDN support:      no      (--with-{libidn,winidn})
  Build libcurl:    Shared=no, Static=yes
  Built-in manual:  enabled
  --libcurl option: enabled (--disable-libcurl-option)
  Verbose errors:   enabled (--disable-verbose)
  SSPI support:     no      (--enable-sspi)
  ca cert bundle:   /etc/ssl/certs/ca-certificates.crt
  ca cert path:     no
  ca fallback:      no
  LDAP support:     no      (--enable-ldap / --with-ldap-lib / --with-lber-lib)
  LDAPS support:    no      (--enable-ldaps)
  RTSP support:     enabled
  RTMP support:     no      (--with-librtmp)
  metalink support: no      (--with-libmetalink)
  PSL support:      no      (libpsl not found)
  HTTP2 support:    disabled (--with-nghttp2)
  Protocols:        DICT FILE FTP FTPS GOPHER HTTP HTTPS IMAP IMAPS POP3 POP3S RTSP SMB SMBS SMTP SMTPS TELNET TFTP

然后在make阶段期间,我收到以下警告:

curl-tool_homedir.o: In function `homedir':
tool_homedir.c:(.text+0x60): warning: Using 'getpwuid' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
../lib/.libs/libcurl.a(libcurl_la-netrc.o): In function `Curl_parsenetrc':
netrc.c:(.text+0x3c3): warning: Using 'getpwuid_r' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
../lib/.libs/libcurl.a(libcurl_la-curl_addrinfo.o): In function `Curl_getaddrinfo_ex':
curl_addrinfo.c:(.text+0x73): warning: Using 'getaddrinfo' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
/usr/lib/gcc/x86_64-linux-gnu/5/../../../x86_64-linux-gnu/libcrypto.a(fips.o): In function `verify_checksums':
(.text+0x4e6): warning: Using 'dlopen' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking

我可以继续执行make install以获得最终的二进制文件.

二进制没有依赖:

$ ldd /tmp/curl/bin/curl
    not a dynamic executable
$ nm /tmp/curl/bin/curl | grep " U "
$ 

但二进制文件根本不起作用:

$ /tmp/curl/bin/curl -version
Segmentation fault (core dumped)

你对根本原因有什么想法吗？

编辑1: GDB输出:

(gdb) run
Starting program: /tmp/curl/bin/curl 

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()

编辑2:

$ nm /tmp/curl/bin/curl | grep getpwuid
0000000000655770 T getpwuid
00000000006558f0 T __getpwuid_r
00000000006558f0 W getpwuid_r
00000000006558f0 T __new_getpwuid_r
0000000000663cf0 T __nscd_getpwuid_r

也许问题来自W:

W符号是一个弱符号,未被特别标记为弱对象符号.当弱定义符号与正常定义的符号链接时,使用正常定义的符号而没有错误.当链接弱未定义符号且未定义符号时,弱符号的值变为零而没有错误.

编辑3: 如果我删除SSL链接我得到了相同的警告,getpwuid但二进制文件正在工作:

./configure --disable-shared --enable-static-nss --prefix=/tmp/curl LDFLAGS='-static -static-libgcc -Wl,-Bstatic,-lc'

ldd /tmp/curl/bin/curl
    not a dynamic executable
 /tmp/curl/bin/curl --version
curl 7.50.2-DEV (x86_64-pc-linux-gnu) libcurl/7.50.2-DEV zlib/1.2.8
Protocols: dict file ftp gopher http imap pop3 rtsp smtp telnet tftp 
Features: IPv6 Largefile libz UnixSockets 

 nm /tmp/curl/bin/curl | grep getpwuid
00000000004f52d0 T getpwuid
00000000004f5450 T __getpwuid_r
00000000004f5450 W getpwuid_r
00000000004f5450 T __new_getpwuid_r
0000000000502cd0 T __nscd_getpwuid_r

但我需要为HTTPS支持添加SSL,因此问题仍然存在.

编辑4: 问题与此直接相关nss.奇怪的一点是,./configure --prefix=/tmp/curl --disable-shared --enable-static-nss LDFLAGS='-static -static-libgcc -Wl,-Bstatic' LIBS='-ls'生成一个可以工作的独立可执行文件但没有SSL.该nss问题是由于SSL连接.

Answer 1

拉入 openssl https://www.openssl.org/的源开发版本并重新编译它以进行静态链接（以“.a”而不是“.so”结尾）。然后重建curl，链接到您构建的openssl静态库。

您知道 libssl 给您带来了问题，但它可能不是唯一的库。当您找到下一个给您带来问题的库时，请对其执行相同的操作：拉入源开发版本并重建它以进行静态链接。