Re: [PATCH v5 00/11] perf: Support multiple system call tables in the build

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Fri, Mar 14, 2025 at 02:10:57PM -0300, Arnaldo Carvalho de Melo wrote:
> On Thu, Mar 13, 2025 at 10:45:49PM -0700, Namhyung Kim wrote:
> > On Thu, Mar 13, 2025 at 05:47:27PM -0300, Arnaldo Carvalho de Melo wrote:
> > > On Thu, Mar 13, 2025 at 05:20:09PM -0300, Arnaldo Carvalho de Melo wrote:
> > > > Still building, but noticed this on x86_64:
> > > > 
> > > > 105: perf trace enum augmentation tests                              : FAILED!
> > > > 106: perf trace BTF general tests                                    : FAILED!
> > > > 107: perf trace exit race                                            : Ok
> > > > 108: perf trace record and replay                                    : FAILED!
> > > > 
> > > > 
> > > > The first doesn´t help that much with verbose mode, haven't checked if
> > > > before this series it was failing :-\
> > > > 
> > > > root@x1:~# perf test -vvv 105
> > > > 105: perf trace enum augmentation tests:
> > > > --- start ---
> > > > test child forked, pid 19411
> > > > Checking if vmlinux exists
> > > > Tracing syscall landlock_add_rule
> > > > ---- end(-1) ----
> > > > 105: perf trace enum augmentation tests                              : FAILED!
> > > > root@x1:~#
> > > 
> > > So:
> > > 
> > > root@x1:~# perf trace -e landlock_add_rule perf test -w landlock
> > > root@x1:~# 
> > > 
> > > But:
> > > 
> > > root@x1:~# perf trace perf test -w landlock |& grep landlock_add_rule
> > >     26.120 ( 0.002 ms): perf/19791 landlock_add_rule(ruleset_fd: 11, rule_type: LANDLOCK_RULE_PATH_BENEATH, rule_attr: 0x7ffde75e2680, flags: 45) = -1 EINVAL (Invalid argument)
> > >     26.124 ( 0.001 ms): perf/19791 landlock_add_rule(ruleset_fd: 11, rule_type: LANDLOCK_RULE_NET_PORT, rule_attr: 0x7ffde75e2690, flags: 45) = -1 EINVAL (Invalid argument)
> > > root@x1:~# 
> > > 
> > > -e is having some trouble, when no event is specified, then it works.
> > > 
> > > Something in the changes made to:
> > > 
> > > static int trace__parse_events_option(const struct option *opt, const char *str,
> > >                                       int unset __maybe_unused)
> > 
> > Thanks for the test, I think this should fix it:
> > 
> 
> Well, not really:
> 
> root@number:~# perf trace -e landlock_add_rule perf test -w landlock
> perf: Segmentation fault
> Obtained 10 stack frames.
> perf() [0x5be761]
> perf() [0x5be7f9]
> /lib64/libc.so.6(+0x40fd0) [0x7fe005c4efd0]
> perf() [0x491bc1]
> perf() [0x497090]
> perf() [0x4973ab]
> perf() [0x413483]
> /lib64/libc.so.6(+0x2a088) [0x7fe005c38088]
> /lib64/libc.so.6(__libc_start_main+0x8b) [0x7fe005c3814b]
> perf() [0x413ad5]
> Segmentation fault (core dumped)
> root@number:~#
> 
> Time for me to test another patch from Ian, the one symbolizing the
> above backtrace...
> 
> Worked, but didn't help as much, with gdb:
> 
> (gdb) run trace -e landlock_add_rule perf test -w landlock
> Starting program: /root/bin/perf trace -e landlock_add_rule perf test -w landlock
> 
> This GDB supports auto-downloading debuginfo from the following URLs:
>   <https://debuginfod.fedoraproject.org/>
> Enable debuginfod for this session? (y or [n]) y
> Debuginfod has been enabled.
> To make this setting permanent, add 'set debuginfod enabled on' to .gdbinit.
> Downloading 53.88 K separate debug info for system-supplied DSO at 0x7ffff7fc6000
> Downloading 458.26 K separate debug info for /lib64/libtracefs.so.1                                                                                                                            
> [Thread debugging using libthread_db enabled]                                                                                                                                                  
> Using host libthread_db library "/lib64/libthread_db.so.1".
> [Detaching after fork from child process 39141]
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0x00000000004d0e56 in trace__find_usable_bpf_prog_entry (trace=0x7fffffffa510, sc=0x10fb7b0) at builtin-trace.c:3882
> 3882				bool is_pointer = field->flags & TEP_FIELD_IS_POINTER,
> (gdb) p field
> $1 = (struct tep_format_field *) 0x64656e6769736e75
> (gdb) bt
> #0  0x00000000004d0e56 in trace__find_usable_bpf_prog_entry (trace=0x7fffffffa510, sc=0x10fb7b0) at builtin-trace.c:3882
> #1  0x00000000004cf3de in trace__init_syscalls_bpf_prog_array_maps (trace=0x7fffffffa510, e_machine=62) at builtin-trace.c:4040
> #2  0x00000000004bf626 in trace__run (trace=0x7fffffffa510, argc=4, argv=0x7fffffffde40) at builtin-trace.c:4473
> #3  0x00000000004bb7a9 in cmd_trace (argc=4, argv=0x7fffffffde40) at builtin-trace.c:5741
> #4  0x00000000004d873f in run_builtin (p=0xf83d48 <commands+648>, argc=7, argv=0x7fffffffde40) at perf.c:351
> #5  0x00000000004d7df3 in handle_internal_command (argc=7, argv=0x7fffffffde40) at perf.c:404
> #6  0x00000000004d860f in run_argv (argcp=0x7fffffffdc7c, argv=0x7fffffffdc70) at perf.c:448
> #7  0x00000000004d7a4f in main (argc=7, argv=0x7fffffffde40) at perf.c:556
> (gdb) list -10
> 3867		return NULL;
> 3868	
> 3869	try_to_find_pair:
> 3870		for (int i = 0, num_idx = syscalltbl__num_idx(sc->e_machine); i < num_idx; ++i) {
> 3871			int id = syscalltbl__id_at_idx(sc->e_machine, i);
> 3872			struct syscall *pair = trace__syscall_info(trace, NULL, sc->e_machine, id);
> 3873			struct bpf_program *pair_prog;
> 3874			bool is_candidate = false;
> 3875	
> 3876			if (pair == NULL || pair == sc ||
> (gdb)

Humm

(gdb) p i
$1 = 147
(gdb) p num_idx
$2 = 379
(gdb) p id
$3 = 192
(gdb) p pair
$4 = (struct syscall *) 0x10fe8f0
(gdb) p *pair
$5 = {e_machine = 62, id = 192, tp_format = 0x10f6c00, nr_args = 3, args_size = 48, bpf_prog = {sys_enter = 0x0, sys_exit = 0x0}, is_exit = false, is_open = false, nonexistent = false, 
  use_btf = false, args = 0x10f9480, name = 0x814406 "lgetxattr", fmt = 0x0, arg_fmt = 0x10fa0a0}
(gdb) p sc
$6 = (struct syscall *) 0x10fb7b0
(gdb) p sc->args
$7 = (struct tep_format_field *) 0x64656e6769736e75
(gdb) p *pair
$8 = {e_machine = 62, id = 192, tp_format = 0x10f6c00, nr_args = 3, args_size = 48, bpf_prog = {sys_enter = 0x0, sys_exit = 0x0}, is_exit = false, is_open = false, nonexistent = false, 
  use_btf = false, args = 0x10f9480, name = 0x814406 "lgetxattr", fmt = 0x0, arg_fmt = 0x10fa0a0}
(gdb)

it finds the pair, but then its sc->args has a bogus pointer... I'll see
where this isn't being initialized...

- Arnaldo