I’m having a senior moment. I have a program, one of the things it does is call
gettimeofday(), I compiled with –fPIC then I put into a shared library which I
built using gcc –shared. When a program that is linked against this shared
library runs and invokes the program in question it craps out calling
gettimeofday() branching somewhere unexpected (i.e. Not within libc.so which is
what I would have expected).
I’ve verified that the code generated is correct:
lgr %r1,%r11
aghi %r1,168
lgr %r2,%r1
lghi %r3,0
brasl %r14,gettimeofday@PLT
lg %r1,168(%r11)
Used readelf on the objet to see what it thinks about that symbol:
00000000012a 062900000013 R_390_PC32DBL 0000000000000000 gettimeofday + 2
000000003736 062900000013 R_390_PC32DBL 0000000000000000 gettimeofday + 2
1577: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND gettimeofday
Used it again on the shared library:
00000000c572 005c00000013 R_390_PC32DBL 0000000000000000 gettimeofday + 2
00000000fb7e 005c00000013 R_390_PC32DBL 0000000000000000 gettimeofday + 2
92: 0000000000000000 0 FUNC GLOBAL DEFAULT UND
gettimeofday@GLIBC_2.2 (2)
442: 0000000000000000 0 FUNC GLOBAL DEFAULT UND
gettimeofday@@GLIBC_2.2
Verified that programs from other shared libraries are successfully calling
gettimeofday(). Yet, I die horribly:
#0 0x000003ff800038ac in ?? ()
#1 0x000003fffd6e7576 in waitForAccept (ctl=0xbc3b9300) at lineUtil.c:248
#2 0x00000000800067a6 in lineTaskV4 (arg=0xbc3b9300) at lineTaskV4.c:230
#3 0x0000004b5fa292c0 in start_thread () from /lib64/libpthread.so.0
#4 0x0000004b5f9730b2 in thread_start () from /lib64/libc.so.6
According to the process map the address it’s branching to is not in the map.
All I can think of is that I created the shared library incorrectly:
gcc –g –fPIC –o lineUtil.o lineUtil.c
:
gcc –shared –o libxxx.so lineUtil.o ...
Anyone spot my stupidity (restrict your answers to the case in hand).
Neale
----------------------------------------------------------------------
For LINUX-390 subscribe / signoff / archive access instructions,
send email to [email protected] with the message: INFO LINUX-390 or visit
http://www.marist.edu/htbin/wlvindex?LINUX-390
----------------------------------------------------------------------
For more information on Linux on System z, visit
http://wiki.linuxvm.org/
