[PATCH] perf test record+probe_libc_inet_pton: Fix call chain match on powerpc

[Athira Rajeev]

> On 26-Nov-2023, at 12:39 PM, Likhitha Korrapati <likhitha at linux.ibm.com> wrote:
> 
> The perf test "probe libc's inet_pton & backtrace it with ping" fails on
> powerpc as below:
> 
> root at xxx perf]# perf test -v "probe libc's inet_pton & backtrace it with
> ping"
> 85: probe libc's inet_pton & backtrace it with ping                 :
> --- start ---
> test child forked, pid 96028
> ping 96056 [002] 127271.101961: probe_libc:inet_pton: (7fffa1779a60)
> 7fffa1779a60 __GI___inet_pton+0x0
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)
> 7fffa172a73c getaddrinfo+0x121c
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)
> FAIL: expected backtrace entry
> "gaih_inet.*\+0x[[:xdigit:]]+[[:space:]]\(/usr/lib64/glibc-hwcaps/power10/libc.so.6\)$"
> got "7fffa172a73c getaddrinfo+0x121c
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)"
> test child finished with -1
> ---- end ----
> probe libc's inet_pton & backtrace it with ping: FAILED!

Reviewed-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>

Thanks
Athira
> 
> This test installs a probe on libc's inet_pton function, which will use
> uprobes and then uses perf trace on a ping to localhost. It gets 3
> levels deep backtrace and checks whether it is what we expected or not.
> 
> The test started failing from RHEL 9.4 where as it works in previous
> distro version (RHEL 9.2). Test expects gaih_inet function to be part of
> backtrace. But in the glibc version (2.34-86) which is part of distro
> where it fails, this function is missing and hence the test is failing.
> 
> From nm and ping command output we can confirm that gaih_inet function
> is not present in the expected backtrace for glibc version glibc-2.34-86
> 
> [root at xxx perf]# nm /usr/lib64/glibc-hwcaps/power10/libc.so.6 | grep gaih_inet
> 00000000001273e0 t gaih_inet_serv
> 00000000001cd8d8 r gaih_inet_typeproto
> 
> [root at xxx perf]# perf script -i /tmp/perf.data.6E8
> ping  104048 [000] 128582.508976: probe_libc:inet_pton: (7fff83779a60)
>            7fff83779a60 __GI___inet_pton+0x0
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)
>            7fff8372a73c getaddrinfo+0x121c
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)
>               11dc73534 [unknown] (/usr/bin/ping)
>            7fff8362a8c4 __libc_start_call_main+0x84
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)
> 
> FAIL: expected backtrace entry
> "gaih_inet.*\+0x[[:xdigit:]]+[[:space:]]\(/usr/lib64/glibc-hwcaps/power10/libc.so.6\)$"
> got "7fff9d52a73c getaddrinfo+0x121c
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)"
> 
> With version glibc-2.34-60 gaih_inet function is present as part of the
> expected backtrace. So we cannot just remove the gaih_inet function from
> the backtrace.
> 
> [root at xxx perf]# nm /usr/lib64/glibc-hwcaps/power10/libc.so.6 | grep gaih_inet
> 0000000000130490 t gaih_inet.constprop.0
> 000000000012e830 t gaih_inet_serv
> 00000000001d45e4 r gaih_inet_typeproto
> 
> [root at xxx perf]# ./perf script -i /tmp/perf.data.b6S
> ping   67906 [000] 22699.591699: probe_libc:inet_pton_3: (7fffbdd80820)
>            7fffbdd80820 __GI___inet_pton+0x0
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)
>            7fffbdd31160 gaih_inet.constprop.0+0xcd0
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)
>            7fffbdd31c7c getaddrinfo+0x14c
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)
>               1140d3558 [unknown] (/usr/bin/ping)
> 
> This patch solves this issue by doing a conditional skip. If there is a
> gaih_inet function present in the libc then it will be added to the
> expected backtrace else the function will be skipped from being added
> to the expected backtrace.
> 
> Output with the patch
> 
> [root at xxx perf]# ./perf test -v "probe libc's inet_pton & backtrace it
> with ping"
> 83: probe libc's inet_pton & backtrace it with ping                 :
> --- start ---
> test child forked, pid 102662
> ping 102692 [000] 127935.549973: probe_libc:inet_pton: (7fff93379a60)
> 7fff93379a60 __GI___inet_pton+0x0
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)
> 7fff9332a73c getaddrinfo+0x121c
> (/usr/lib64/glibc-hwcaps/power10/libc.so.6)
> 11ef03534 [unknown] (/usr/bin/ping)
> test child finished with 0
> ---- end ----
> probe libc's inet_pton & backtrace it with ping: Ok
> 
> Signed-off-by: Likhitha Korrapati <likhitha at linux.ibm.com>
> Reported-by: Disha Goel <disgoel at linux.ibm.com>
> ---
> tools/perf/tests/shell/record+probe_libc_inet_pton.sh | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/tests/shell/record+probe_libc_inet_pton.sh b/tools/perf/tests/shell/record+probe_libc_inet_pton.sh
> index eebeea6bdc76..72c65570db37 100755
> --- a/tools/perf/tests/shell/record+probe_libc_inet_pton.sh
> +++ b/tools/perf/tests/shell/record+probe_libc_inet_pton.sh
> @@ -45,7 +45,10 @@ trace_libc_inet_pton_backtrace() {
> ;;
> ppc64|ppc64le)
> eventattr='max-stack=4'
> - echo "gaih_inet.*\+0x[[:xdigit:]]+[[:space:]]\($libc\)$" >> $expected
> + # Add gaih_inet to expected backtrace only if it is part of libc.
> + if nm $libc | grep -F -q gaih_inet.; then
> + echo "gaih_inet.*\+0x[[:xdigit:]]+[[:space:]]\($libc\)$" >> $expected
> + fi
> echo "getaddrinfo\+0x[[:xdigit:]]+[[:space:]]\($libc\)$" >> $expected
> echo ".*(\+0x[[:xdigit:]]+|\[unknown\])[[:space:]]\(.*/bin/ping.*\)$" >> $expected
> ;;
> -- 
> 2.39.1
>