Linus,

[ This is not a merge window pull, I was waiting on a tested-by from the reporter ]

Kprobe events added "ustring" to distinguish reading strings from kernel space or user space. But the creating of the event format file only checks for "string" to display string formats. "ustring" must also be handled.

Please pull the latest trace-v5.5-rc7 tree, which can be found at:

git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git trace-v5.5-rc7

Tag SHA1: 83993af56b45a4c0b34401ee5bdd96c94180d77d Head SHA1: 20279420ae3a8ef4c5d9fedc360a2c37a1dbdf1b

Steven Rostedt (VMware) (1): tracing/kprobes: Have uname use __get_str() in print_fmt

---- kernel/trace/trace_probe.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --------------------------- commit 20279420ae3a8ef4c5d9fedc360a2c37a1dbdf1b Author: Steven Rostedt (VMware) rostedt@goodmis.org Date: Fri Jan 24 10:07:42 2020 -0500

tracing/kprobes: Have uname use __get_str() in print_fmt

Thomas Richter reported:

> Test case 66 'Use vfs_getname probe to get syscall args filenames' > is broken on s390, but works on x86. The test case fails with: > > [root@m35lp76 perf]# perf test -F 66 > 66: Use vfs_getname probe to get syscall args filenames > :Recording open file: > [ perf record: Woken up 1 times to write data ] > [ perf record: Captured and wrote 0.004 MB /tmp/__perf_test.perf.data.TCdYj\ > (20 samples) ] > Looking at perf.data file for vfs_getname records for the file we touched: > FAILED! > [root@m35lp76 perf]#

The root cause was the print_fmt of the kprobe event that referenced the "ustring"

> Setting up the kprobe event using perf command: > > # ./perf probe "vfs_getname=getname_flags:72 pathname=filename:ustring" > > generates this format file: > [root@m35lp76 perf]# cat /sys/kernel/debug/tracing/events/probe/\ > vfs_getname/format > name: vfs_getname > ID: 1172 > format: > field:unsigned short common_type; offset:0; size:2; signed:0; > field:unsigned char common_flags; offset:2; size:1; signed:0; > field:unsigned char common_preempt_count; offset:3; size:1; signed:0; > field:int common_pid; offset:4; size:4; signed:1; > > field:unsigned long __probe_ip; offset:8; size:8; signed:0; > field:__data_loc char[] pathname; offset:16; size:4; signed:1; > > print fmt: "(%lx) pathname="%s"", REC->__probe_ip, REC->pathname

Instead of using "__get_str(pathname)" it referenced it directly.

Link: http://lkml.kernel.org/r/20200124100742.4050c15e@gandalf.local.home

Cc: stable@vger.kernel.org Fixes: 88903c464321 ("tracing/probe: Add ustring type for user-space string") Acked-by: Masami Hiramatsu mhiramat@kernel.org Reported-by: Thomas Richter tmricht@linux.ibm.com Tested-by: Thomas Richter tmricht@linux.ibm.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 9ae87be422f2..ab8b6436d53f 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -876,7 +876,8 @@ static int __set_print_fmt(struct trace_probe *tp, char *buf, int len, for (i = 0; i < tp->nr_args; i++) { parg = tp->args + i; if (parg->count) { - if (strcmp(parg->type->name, "string") == 0) + if ((strcmp(parg->type->name, "string") == 0) || + (strcmp(parg->type->name, "ustring") == 0)) fmt = ", __get_str(%s[%d])"; else fmt = ", REC->%s[%d]"; @@ -884,7 +885,8 @@ static int __set_print_fmt(struct trace_probe *tp, char *buf, int len, pos += snprintf(buf + pos, LEN_OR_ZERO, fmt, parg->name, j); } else { - if (strcmp(parg->type->name, "string") == 0) + if ((strcmp(parg->type->name, "string") == 0) || + (strcmp(parg->type->name, "ustring") == 0)) fmt = ", __get_str(%s)"; else fmt = ", REC->%s";