[20211013]阅读ldd源代码跟踪.txt

[20211013]阅读ldd源代码跟踪.txt --//前几天才发现ldd是bash shell脚本,我看了一下源代码,感觉最后的执行有点怪,做一个记录. $ file $(which ldd) /usr/bin/ldd: Bourne shell script text executable $ cp /u01/app/oracle/product/11.2.0.4/dbhome_1/bin/lsnrctl . $ bash -x ldd lsnrctl Program=bash LineNo=8 :|bash -x ldd lsnrctl Program=ldd LineNo=27 /usr/bin/ldd:|TEXTDOMAIN=libc Program=ldd LineNo=28 /usr/bin/ldd:|TEXTDOMAINDIR=/usr/share/locale Program=ldd LineNo=30 /usr/bin/ldd:|RTLDLIST='/lib/ld-linux.so.2 /lib64/ld-linux-x86-64.so.2' Program=ldd LineNo=31 /usr/bin/ldd:|warn= Program=ldd LineNo=32 /usr/bin/ldd:|bind_now= Program=ldd LineNo=33 /usr/bin/ldd:|verbose= Program=ldd LineNo=35 /usr/bin/ldd:|test 1 -gt 0 Program=ldd LineNo=36 /usr/bin/ldd:|case "$1" in Program=ldd LineNo=92 /usr/bin/ldd:|break Program=ldd LineNo=103 /usr/bin/ldd:|add_env='LD_TRACE_LOADED_OBJECTS=1 LD_WARN= LD_BIND_NOW=' Program=ldd LineNo=104 /usr/bin/ldd:|add_env='LD_TRACE_LOADED_OBJECTS=1 LD_WARN= LD_BIND_NOW= LD_LIBRARY_VERSION=$verify_out' Program=ldd LineNo=105 /usr/bin/ldd:|add_env='LD_TRACE_LOADED_OBJECTS=1 LD_WARN= LD_BIND_NOW= LD_LIBRARY_VERSION=$verify_out LD_VERBOSE=' Program=ldd LineNo=106 /usr/bin/ldd:|test '' = yes Program=ldd LineNo=114 /usr/bin/ldd:|set -o pipefail Program=ldd LineNo=124 /usr/bin/ldd:|case $# in Program=ldd LineNo=131 /usr/bin/ldd:|single_file=t Program=ldd LineNo=138 /usr/bin/ldd:|result=0 Program=ldd LineNo=139 /usr/bin/ldd:|for file in '"$@"' Program=ldd LineNo=141 /usr/bin/ldd:|test t = t Program=ldd LineNo=142 /usr/bin/ldd:|case $file in Program=ldd LineNo=145 /usr/bin/ldd:|file=./lsnrctl Program=ldd LineNo=148 /usr/bin/ldd:|test '!' -e ./lsnrctl Program=ldd LineNo=151 /usr/bin/ldd:|test '!' -f ./lsnrctl Program=ldd LineNo=154 /usr/bin/ldd:|test -r ./lsnrctl Program=ldd LineNo=155 /usr/bin/ldd:|test -x ./lsnrctl Program=ldd LineNo=157 /usr/bin/ldd:|RTLD= Program=ldd LineNo=158 /usr/bin/ldd:|ret=1 Program=ldd LineNo=159 /usr/bin/ldd:|for rtld in '${RTLDLIST}' Program=ldd LineNo=160 /usr/bin/ldd:|test -x /lib/ld-linux.so.2 PProgram=ldd LineNo=161 /usr/bin/ldd:|/lib/ld-linux.so.2 --verify ./lsnrctl Program=ldd LineNo=161 /usr/bin/ldd:|verify_out= Program=ldd LineNo=162 /usr/bin/ldd:|ret=1 Program=ldd LineNo=163 /usr/bin/ldd:|case $ret in Program=ldd LineNo=159 /usr/bin/ldd:|for rtld in '${RTLDLIST}' Program=ldd LineNo=160 /usr/bin/ldd:|test -x /lib64/ld-linux-x86-64.so.2 PProgram=ldd LineNo=161 /usr/bin/ldd:|/lib64/ld-linux-x86-64.so.2 --verify ./lsnrctl Program=ldd LineNo=161 /usr/bin/ldd:|verify_out= Program=ldd LineNo=162 /usr/bin/ldd:|ret=0 Program=ldd LineNo=163 /usr/bin/ldd:|case $ret in Program=ldd LineNo=164 /usr/bin/ldd:|RTLD=/lib64/ld-linux-x86-64.so.2 Program=ldd LineNo=164 /usr/bin/ldd:|break Program=ldd LineNo=168 /usr/bin/ldd:|case $ret in Program=ldd LineNo=177 /usr/bin/ldd:|try_trace /lib64/ld-linux-x86-64.so.2 ./lsnrctl Program=ldd LineNo=116 /usr/bin/ldd:try_trace|eval LD_TRACE_LOADED_OBJECTS=1 LD_WARN= LD_BIND_NOW= 'LD_LIBRARY_VERSION=$verify_out' LD_VERBOSE= '"$@"' Program=ldd LineNo=116 /usr/bin/ldd:try_trace|cat PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|LD_TRACE_LOADED_OBJECTS=1 PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|LD_WARN= PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|LD_BIND_NOW= PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|LD_LIBRARY_VERSION= PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|LD_VERBOSE= PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|/lib64/ld-linux-x86-64.so.2 ./lsnrctl         linux-vdso.so.1 =>  (0x00007ffffd5e0000)         libclntsh.so.11.1 => /u01/app/oracle/product/11.2.0.4/dbhome_1/lib/libclntsh.so.11.1 (0x00007fe81c758000)         libnnz11.so => /u01/app/oracle/product/11.2.0.4/dbhome_1/lib/libnnz11.so (0x00007fe81c38a000)         libdl.so.2 => /lib64/libdl.so.2 (0x0000003799800000)         libm.so.6 => /lib64/libm.so.6 (0x00000032cac00000)         libpthread.so.0 => /lib64/libpthread.so.0 (0x000000379a000000)         libnsl.so.1 => /lib64/libnsl.so.1 (0x000000379c400000)         libc.so.6 => /lib64/libc.so.6 (0x0000003799000000)         libaio.so.1 => /usr/lib64/libaio.so.1 (0x00007fe81c187000)         /lib64/ld-linux-x86-64.so.2 (0x0000003798c00000) Program=ldd LineNo=190 /usr/bin/ldd:|exit 0 --//注意看最后几行 Program=ldd LineNo=116 /usr/bin/ldd:try_trace|eval LD_TRACE_LOADED_OBJECTS=1 LD_WARN= LD_BIND_NOW= 'LD_LIBRARY_VERSION=$verify_out' LD_VERBOSE= '"$@"' Program=ldd LineNo=116 /usr/bin/ldd:try_trace|cat PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|LD_TRACE_LOADED_OBJECTS=1 PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|LD_WARN= PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|LD_BIND_NOW= PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|LD_LIBRARY_VERSION= PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|LD_VERBOSE= PProgram=ldd LineNo=116 /usr/bin/ldd:try_trace|/lib64/ld-linux-x86-64.so.2 ./lsnrctl --//感觉执行的是内容是: eval LD_TRACE_LOADED_OBJECTS=1 LD_WARN= LD_BIND_NOW= LD_LIBRARY_VERSION= LD_VERBOSE= /lib64/ld-linux-x86-64.so.2 ./lsnrctl --//如果仔细看可以发现开始检查参数,给一下参数LD开头的赋值,然后执行如下: eval LD_TRACE_LOADED_OBJECTS=1 LD_WARN= LD_BIND_NOW= LD_LIBRARY_VERSION= LD_VERBOSE= /lib64/ld-linux-x86-64.so.2 ./lsnrctl --//手工执行如下: $ eval LD_TRACE_LOADED_OBJECTS=1 LD_WARN= LD_BIND_NOW= LD_LIBRARY_VERSION= LD_VERBOSE= /lib64/ld-linux-x86-64.so.2 ./lsnrctl         linux-vdso.so.1 =>  (0x00007fff2097b000)         libclntsh.so.11.1 => /u01/app/oracle/product/11.2.0.4/dbhome_1/lib/libclntsh.so.11.1 (0x00007f88c2549000)         libnnz11.so => /u01/app/oracle/product/11.2.0.4/dbhome_1/lib/libnnz11.so (0x00007f88c217b000)         libdl.so.2 => /lib64/libdl.so.2 (0x0000003799800000)         libm.so.6 => /lib64/libm.so.6 (0x00000032cac00000)         libpthread.so.0 => /lib64/libpthread.so.0 (0x000000379a000000)         libnsl.so.1 => /lib64/libnsl.so.1 (0x000000379c400000)         libc.so.6 => /lib64/libc.so.6 (0x0000003799000000)         libaio.so.1 => /usr/lib64/libaio.so.1 (0x00007f88c1f78000)         /lib64/ld-linux-x86-64.so.2 (0x0000003798c00000) --//如果单独执行如下,直接执行程序: $ /lib64/ld-linux-x86-64.so.2 ./lsnrctl LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 13-OCT-2021 15:23:45 Copyright (c) 1991, 2013, Oracle.  All rights reserved. Welcome to LSNRCTL, type "help" for information. LSNRCTL> $ eval  /lib64/ld-linux-x86-64.so.2 ./lsnrctl LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 13-OCT-2021 15:24:48 Copyright (c) 1991, 2013, Oracle.  All rights reserved. Welcome to LSNRCTL, type "help" for information. LSNRCTL> --//只要设置LD_TRACE_LOADED_OBJECTS的环境变量就可以执行,不需要赋值. $ eval LD_TRACE_LOADED_OBJECTS=  /lib64/ld-linux-x86-64.so.2 ./lsnrctl         linux-vdso.so.1 =>  (0x00007fffb93c1000)         libclntsh.so.11.1 => /u01/app/oracle/product/11.2.0.4/dbhome_1/lib/libclntsh.so.11.1 (0x00007f427e229000)         libnnz11.so => /u01/app/oracle/product/11.2.0.4/dbhome_1/lib/libnnz11.so (0x00007f427de5b000)         libdl.so.2 => /lib64/libdl.so.2 (0x0000003799800000)         libm.so.6 => /lib64/libm.so.6 (0x00000032cac00000)         libpthread.so.0 => /lib64/libpthread.so.0 (0x000000379a000000)         libnsl.so.1 => /lib64/libnsl.so.1 (0x000000379c400000)         libc.so.6 => /lib64/libc.so.6 (0x0000003799000000)         libaio.so.1 => /usr/lib64/libaio.so.1 (0x00007f427dc58000)         /lib64/ld-linux-x86-64.so.2 (0x0000003798c00000) $ export LD_TRACE_LOADED_OBJECTS= $ /lib64/ld-linux-x86-64.so.2 ./lsnrctl         linux-vdso.so.1 =>  (0x00007fff2829c000)         libclntsh.so.11.1 => /u01/app/oracle/product/11.2.0.4/dbhome_1/lib/libclntsh.so.11.1 (0x00007f360edb5000)         libnnz11.so => /u01/app/oracle/product/11.2.0.4/dbhome_1/lib/libnnz11.so (0x00007f360e9e7000)         libdl.so.2 => /lib64/libdl.so.2 (0x0000003799800000)         libm.so.6 => /lib64/libm.so.6 (0x00000032cac00000)         libpthread.so.0 => /lib64/libpthread.so.0 (0x000000379a000000)         libnsl.so.1 => /lib64/libnsl.so.1 (0x000000379c400000)         libc.so.6 => /lib64/libc.so.6 (0x0000003799000000)         libaio.so.1 => /usr/lib64/libaio.so.1 (0x00007f360e7e4000)         /lib64/ld-linux-x86-64.so.2 (0x0000003798c00000) $ unset LD_TRACE_LOADED_OBJECTS $ /lib64/ld-linux-x86-64.so.2 ./lsnrctl LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 13-OCT-2021 15:29:31 Copyright (c) 1991, 2013, Oracle.  All rights reserved. Welcome to LSNRCTL, type "help" for information. LSNRCTL> $ LD_TRACE_LOADED_OBJECTS=1 $ /lib64/ld-linux-x86-64.so.2 ./lsnrctl LSNRCTL for Linux: Version 11.2.0.4.0 - Production on 13-OCT-2021 15:29:55 Copyright (c) 1991, 2013, Oracle.  All rights reserved. Welcome to LSNRCTL, type "help" for information. LSNRCTL>