[DTrace-devel] changes needed for PIE executables

[David Mc Lean]

When running some tests on a fairly new Ubuntu install, I found a number 
of failures in the usdt tests.

test/unittest/usdt/tst.allargs.sh
test/unittest/usdt/tst.argmap.d
test/unittest/usdt/tst.args-alt.d
test/unittest/usdt/tst.args.d
test/unittest/usdt/tst.badguess.sh
test/unittest/usdt/tst.dlclose2.sh
test/unittest/usdt/tst.eliminate.sh
test/unittest/usdt/tst.enable.d
test/unittest/usdt/tst.enable_and.d
test/unittest/usdt/tst.enable_and_2.d
test/unittest/usdt/tst.enable_or.d
test/unittest/usdt/tst.enable_or_2.d
test/unittest/usdt/tst.enable_return.d
test/unittest/usdt/tst.enable_stmt.d
test/unittest/usdt/tst.enabled.sh
test/unittest/usdt/tst.enabled2.sh
test/unittest/usdt/tst.entryreturn.sh
test/unittest/usdt/tst.fork.sh
test/unittest/usdt/tst.guess32.sh
test/unittest/usdt/tst.multiple.sh
test/unittest/usdt/tst.reeval.sh
test/unittest/usdt/tst.static.sh
test/unittest/usdt/tst.static2.sh
test/unittest/usdt/tst.tailcall.d

Something has changed in this new context (Ubuntu install 19.04) where 
the tests fail.

After some searching and inspection advice from Kris and Nick, the 
problem appears to stem from the executable now being PIE format.

$ readelf -h test/triggers/usdt-tst-args

shows

Type:                              DYN (Shared object file)

So, we have confirmation this is now a PIE file.

versus what we have seen previously:

Type:                              EXEC (Executable file)


The question now is how do we adapt to this new file format when running 
our USDT ?


Here are the full readelf outputs for those who might be interested:

$ readelf -h test/triggers/usdt-tst-args
ELF Header:
   Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
   Class:                             ELF64
   Data:                              2's complement, little endian
   Version:                           1 (current)
   OS/ABI:                            UNIX - System V
   ABI Version:                       0
   Type:                              DYN (Shared object file)
   Machine:                           Advanced Micro Devices X86-64
   Version:                           0x1
   Entry point address:               0x1650
   Start of program headers:          64 (bytes into file)
   Start of section headers:          15704 (bytes into file)
   Flags:                             0x0
   Size of this header:               64 (bytes)
   Size of program headers:           56 (bytes)
   Number of program headers:         11
   Size of section headers:           64 (bytes)
   Number of section headers:         30
   Section header string table index: 29

$ readelf -h test/triggers/usdt-tst-args
ELF Header:
   Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
   Class:                             ELF64
   Data:                              2's complement, little endian
   Version:                           1 (current)
   OS/ABI:                            UNIX - System V
   ABI Version:                       0
   Type:                              EXEC (Executable file)
   Machine:                           Advanced Micro Devices X86-64
   Version:                           0x1
   Entry point address:               0x400b6c
   Start of program headers:          64 (bytes into file)
   Start of section headers:          11512 (bytes into file)
   Flags:                             0x0
   Size of this header:               64 (bytes)
   Size of program headers:           56 (bytes)
   Number of program headers:         9
   Size of section headers:           64 (bytes)
   Number of section headers:         31
   Section header string table index: 30