How to map function address to function in *.so files

Try giving the offset to addr2line, along with the section name. Like this:

addr2line -j .text -e libtst.so 0x26887

Edit: By the way, if it wasn't clear, the 0x26887 comes from what you provided:

0xb77dc887(fun2 addr+offset)-0xb77b6000 (lib starting addr) = 0x26887 (result)

I've had a look at files backtrace.c and backtracesyms.c files in glibc source code (git://sourceware.org/git/glibc.git, commit 2482ae433a4249495859343ae1fba408300f2c2e).

Assuming I haven't misread/misunderstood things: backtrace() itself looks like it will only give you symbol addresses as they are at runtime, which I think means you need the library load address as it was from pmap or similar. However, backtrace_symbols() recalculates things so that the addresses are relative to the shared library ELF, and not the process at runtime, which is really convenient. It means you don't need information from pmap.

So, if you've compiled with -g (or with -rdynamic), then you're in luck. You should be able to do the following:

$ # get the address in the ELF so using objdump or nm$ nm libtst.so | grep myfunc0000073c T myfunc5$ # get the (hex) address after adding the offset $ # from the start of the symbol (as provided by backtrace_syms())$ python -c 'print hex(0x0000073c+0x2b)'0x767$ # use addr2line to get the line information, assuming any is available            addr2line -e libtst.so 0x767

Or, using gdb:

$ gdb libtst.so(gdb) info address myfuncSymbol "myfunc" is at 0x073c in a file compiled without debugging. # (Faked output)(gdb) info line *(0x073c+0x2b)Line 27 of "foo.cpp" starts at address 0x767 <myfunc()+21> and ends at 0x769 <something>. # (Faked output)

Also, if you've stripped the library, but stashed off debug symbols for later use, then you'll likely only have ELF offsets printed out by backtrace_syms() and no symbol names (so not quite the case in the original question): In this instance, using gdb is arguably more convenient than using other command line tools. Assuming you've done this, you'll need to invoke gdb like so (for example):

$ gdb -s debug/libtst.debug -e libtst.so

And then go through a similar sequence as above, using 'info line' and 'info address' depending on whether you only have ELF symbol offsets, or symbol names plus offsets.

objdump -x --disassemble -l <objfile>

This should dump, among other things, each compiled instruction of machine code with the line of the C file it came from.