Date: Tue, 7 Jun 2016 12:09:50 -0700 From: Shrikanth Kamath <shrikanth07@gmail.com> To: freebsd-dtrace@freebsd.org Subject: Problem mapping multiple definitions of a structure coming from different modules Message-ID: <CAEOAkMX7DGzhGbQdLsPfU0fdp8oPHSQJ%2B71%2BbxdG1K=QDMJgkg@mail.gmail.com>
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I have two drivers loaded if_igb.ko and if_em.ko on a machine and both
expose a different definition of struct tx_ring, so if we look at the
CTF sections of both drivers they have the individual definitions of
struct tx_ring.
Now when we run a dtrace probe I see the following error,
#dtrace -n 'fbt::igb_start_locked:entry { printf("%d\n", args[0]->num_desc); } '
dtrace: invalid probe specifier fbt::igb_start_locked:entry {
printf("%d\n", args[0]->num_desc); } : in action list: num_desc is not
a member of struct tx_ring
The problem is definition of struct tx_ring in if_igb.ko does contain
member num_desc but dtrace when it starts reads the symbols from
if_em.ko first and then from if_igb.ko, guess this is what is causing
dtrace to report that num_desc is not part of struct tx_ring.
The order in which it read the symbols from modules
...
libdtrace DEBUG: loaded if_em.ko [.SUNW_ctf] (17182 bytes)
libdtrace DEBUG: loaded if_em.ko [.symtab] (25704 bytes)
libdtrace DEBUG: loaded if_em.ko [.strtab] (25690 bytes)
libdtrace DEBUG: hashed if_em.ko [.symtab] (1058 symbols)
libdtrace DEBUG: sorted if_em.ko [.symtab] (880 symbols)
libdtrace DEBUG: loaded CTF container for if_em.ko (0xc56c80)
libdtrace DEBUG: loaded if_igb.ko [.SUNW_ctf] (17403 bytes)
libdtrace DEBUG: loaded if_igb.ko [.symtab] (22536 bytes)
libdtrace DEBUG: loaded if_igb.ko [.strtab] (22595 bytes)
libdtrace DEBUG: hashed if_igb.ko [.symtab] (926 symbols)
libdtrace DEBUG: sorted if_igb.ko [.symtab] (746 symbols)
...
Is there a way for dtrace to map the definition that we are asking to
the module probes that we use. To put plainly if my probe was from
if_igb then we should try to resolve struct tx_ring from if_igb first.
I am not very familiar but I guess dtrace is handicapped because of
the order in which linker passes these files to it. But yeah should
this be a genuine bug?
--
Shrikanth R K
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