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The nfsd-trace.stp (systemtap-4.0-3.el8.x86_64) started to fail on rhel8 (compared to rhel7). The problem seems to be the kernel debuginfo quality:
=======
8.0 Server x86_64 # stap -P -p4 /usr/share/systemtap/examples/network/nfsd-trace.stp
semantic error: while processing probe module("nfsd").function("nfsd4_read@fs/nfsd/nfs4proc.c:752").call from: nfsd.proc4.read from: nfsd.proc.read from: nfsd.proc.entries from: nfsd.proc.entries
semantic error: failed to retrieve location attribute for 'read' [man error::dwarf]: identifier '$read' at /usr/share/systemtap/tapset/linux/nfsd.stp:570:10
dieoffset: 0x1dae8a from /usr/lib/debug/lib/modules/4.18.0-40.el8.x86_64/kernel/fs/nfsd/nfsd.ko.debug
function: nfsd4_read at fs/nfsd/nfs4proc.c:759:5
source: count = $read->rd_length
^
semantic error: failed to retrieve location attribute for 'read' [man error::dwarf]: identifier '$read' at :570:10
dieoffset: 0x1dae8a from /usr/lib/debug/lib/modules/4.18.0-40.el8.x86_64/kernel/fs/nfsd/nfsd.ko.debug
function: nfsd4_read at fs/nfsd/nfs4proc.c:759:5
source: count = $read->rd_length
^
Pass 2: analysis failed. [man error::pass2]
(1) 8.0 Server x86_64 #
=======
The symbol in question appears to actually be present in the kernel source:
=======
8.0 Server x86_64 # nl -ba /usr/src/debug/kernel-4.18.0-40.el8/linux-4.18.0-40.el8.x86_64/fs/nfsd/nfs4proc.c | sed '751,755!d'
751 static __be32
752 nfsd4_read(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
753 union nfsd4_op_u *u)
754 {
755 struct nfsd4_read *read = &u->read;
8.0 Server x86_64 #
=======
Prologue search doesn't seem to help here.
I believe these guys should actually fix the problem:
commit 4e81610ae8c233d876f378cca8374e34cc2ee0e8
Author: Frank Ch. Eigler <fche>
Date: Fri Oct 19 19:31:31 2018 -0400
nfsd tapset: adapt nfsd.proc4.commit probe to different kernel versions
commit 8bc64034509474bee3fb7996b2a9e74c8bc27281
Author: Frank Ch. Eigler <fche>
Date: Fri Oct 19 17:36:04 2018 -0400
nfsd tapset: adapt nfsd.proc4.read probe to different kernel versions
Here too an if(@defined($u)) is appropriate, just like in the .write case.
The nfsd-trace.stp (systemtap-4.0-3.el8.x86_64) started to fail on rhel8 (compared to rhel7). The problem seems to be the kernel debuginfo quality: ======= 8.0 Server x86_64 # stap -P -p4 /usr/share/systemtap/examples/network/nfsd-trace.stp semantic error: while processing probe module("nfsd").function("nfsd4_read@fs/nfsd/nfs4proc.c:752").call from: nfsd.proc4.read from: nfsd.proc.read from: nfsd.proc.entries from: nfsd.proc.entries semantic error: failed to retrieve location attribute for 'read' [man error::dwarf]: identifier '$read' at /usr/share/systemtap/tapset/linux/nfsd.stp:570:10 dieoffset: 0x1dae8a from /usr/lib/debug/lib/modules/4.18.0-40.el8.x86_64/kernel/fs/nfsd/nfsd.ko.debug function: nfsd4_read at fs/nfsd/nfs4proc.c:759:5 source: count = $read->rd_length ^ semantic error: failed to retrieve location attribute for 'read' [man error::dwarf]: identifier '$read' at :570:10 dieoffset: 0x1dae8a from /usr/lib/debug/lib/modules/4.18.0-40.el8.x86_64/kernel/fs/nfsd/nfsd.ko.debug function: nfsd4_read at fs/nfsd/nfs4proc.c:759:5 source: count = $read->rd_length ^ Pass 2: analysis failed. [man error::pass2] (1) 8.0 Server x86_64 # ======= The symbol in question appears to actually be present in the kernel source: ======= 8.0 Server x86_64 # nl -ba /usr/src/debug/kernel-4.18.0-40.el8/linux-4.18.0-40.el8.x86_64/fs/nfsd/nfs4proc.c | sed '751,755!d' 751 static __be32 752 nfsd4_read(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, 753 union nfsd4_op_u *u) 754 { 755 struct nfsd4_read *read = &u->read; 8.0 Server x86_64 # ======= Prologue search doesn't seem to help here.