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perf test: Fix test trace+probe_vfs_getname.sh on s390

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This test places a kprobe to function getname_flags() in the kernel
which has the following prototype:

  struct filename *getname_flags(const char __user *filename, int flags, int *empty)

The 'filename' argument points to a filename located in user space memory.

Looking at commit 88903c4643 ("tracing/probe: Add ustring type for
user-space string") the kprobe should indicate that user space memory is
accessed.

Output before:

   [root@m35lp76 perf]# ./perf test 66 67
   66: Use vfs_getname probe to get syscall args filenames   : FAILED!
   67: Check open filename arg using perf trace + vfs_getname: FAILED!
   [root@m35lp76 perf]#

Output after:

   [root@m35lp76 perf]# ./perf test 66 67
   66: Use vfs_getname probe to get syscall args filenames   : Ok
   67: Check open filename arg using perf trace + vfs_getname: Ok
   [root@m35lp76 perf]#

Comments from Masami Hiramatsu:

This bug doesn't happen on x86 or other archs on which user address
space and kernel address space is the same. On some arches (ppc64 in
this case?) user address space is partially or completely the same as
kernel address space.

(Yes, they switch the world when running into the kernel) In this case,
we need to use different data access functions for each space.

That is why I introduced the "ustring" type for kprobe events.

As far as I can see, Thomas's patch is sane. Thomas, could you show us
your result on your test environment?

Comments from Thomas Richter:

Test results for s/390 included above.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Link: http://lore.kernel.org/lkml/20200217102111.61137-1-tmricht@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Thomas Richter 2020-02-17 11:21:11 +01:00 committed by Arnaldo Carvalho de Melo
parent 3b573bf318
commit 2bbc835376
1 changed files with 1 additions and 1 deletions
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2
tools/perf/tests/shell/lib/probe_vfs_getname.sh
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@ -14,7 +14,7 @@ add_probe_vfs_getname() {
if [ $had_vfs_getname -eq 1 ] ; then
line=$(perf probe -L getname_flags 2>&1 | egrep 'result.*=.*filename;' | sed -r 's/[[:space:]]+([[:digit:]]+)[[:space:]]+result->uptr.*/\1/')
perf probe -q "vfs_getname=getname_flags:${line} pathname=result->name:string" || \
perf probe $verbose "vfs_getname=getname_flags:${line} pathname=filename:string"
perf probe $verbose "vfs_getname=getname_flags:${line} pathname=filename:ustring"
fi
}