Re: [PATCH 01/18] tracing: Add function based events

Jiri Olsa
2018-02-05T08:24:32Z

On Fri, Feb 02, 2018 at 06:04:59PM -0500, Steven Rostedt wrote:

SNIP

> +static int create_function_event(int argc, char **argv)
> +{
> + struct func_event *func_event, *fe;
> + enum func_states state = FUNC_STATE_INIT;
> + char *token;
> + char *ptr;
> + char last;
> + int ret = -EINVAL;
> + int i;
> +
> + func_event = kzalloc(sizeof(*func_event), GFP_KERNEL);
> + if (!func_event)
> + return -ENOMEM;
> +
> + INIT_LIST_HEAD(&func_event->files);
> + func_event->ops.func = func_event_call;
> + func_event->ops.flags = FTRACE_OPS_FL_SAVE_REGS;
> +
> + for (i = 0; i < argc; i++) {
> + ptr = argv[i];
> + last = 0;
> + for (token = next_token(&ptr, &last); token;
> + token = next_token(&ptr, &last)) {
> + state = process_event(func_event, token, state);
> + if (state == FUNC_STATE_ERROR)
> + goto fail;
> + }
> + }
> + if (state != FUNC_STATE_END)
> + goto fail;
> +
> + ret = -EALREADY;
> + list_for_each_entry(fe, &func_events, list) {
> + if (strcmp(fe->func, func_event->func) == 0)
> + goto fail;
> + }
> +
> + ret = ftrace_set_filter(&func_event->ops, func_event->func,
> + strlen(func_event->func), 0);
> + if (ret < 0)
> + goto fail;
> +
> + ret = func_event_create(func_event);
> + if (ret < 0)
> + goto fail;
> +
> + list_add_tail(&func_event->list, &func_events);
> + return 0;

should this be done under 'func_event_mutex' ?

I tried and crashed the system by running 2 scripts with:

echo 'ip_rcv(u64 skb, u64 dev)' > /sys/kernel/debug/tracing/function_events
echo 'SyS_openat(int dfd, string buf, x32 flags, x32 mode)' >> /sys/kernel/debug/tracing/function_events
echo 'SyS_open(x8[32] buf, x32 flags, x32 mode)' >> /sys/kernel/debug/tracing/function_events

jirka

[ 376.727159] general protection fault: 0000 [#1] SMP PTI
[ 376.732992] Modules linked in: intel_rapl sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul igb ghash_clmulni_intel intel_cstate ptp intel_uncore pps_core iTCO_wdt iTCO_vendor_support ipmi_ssif ipmi_si ipmi_devintf ipmi_msghandler shpchp ioatdma cdc_ether usbnet mii intel_rapl_perf i2c_i801 tpm_tis tpm_tis_core dca tpm lpc_ich wmi xfs libcrc32c mgag200 i2c_algo_bit drm_kms_helper ttm crc32c_intel drm megaraid_sas
[ 376.779583] CPU: 9 PID: 1285 Comm: t.sh Not tainted 4.15.0-rc9idle+ #32
[ 376.786956] Hardware name: IBM System x3650 M4 : -[7915E2G]-/00Y7683, BIOS -[VVE124AUS-1.30]- 11/21/2012
[ 376.797545] RIP: 0010:__unregister_trace_event+0xe/0x70
[ 376.803376] RSP: 0018:ffffa643043cbc50 EFLAGS: 00010286
[ 376.809206] RAX: dead000000000100 RBX: ffff91b6340c2480 RCX: ffffffffbf2ebf50
[ 376.817170] RDX: dead000000000200 RSI: ffffffffbf2ed540 RDI: ffff91b6340c2480
[ 376.825135] RBP: ffff91b6340c2460 R08: 0000000000000001 R09: 0000000000000000
[ 376.833099] R10: ffffa643043cbc78 R11: 0000000000000000 R12: ffff91b6340c2400
[ 376.841062] R13: ffff91b6326f8600 R14: dead000000000200 R15: dead000000000100
[ 376.849028] FS: 00007ff3644bcb40(0000) GS:ffff91b63fac0000(0000) knlGS:0000000000000000
[ 376.858058] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 376.864469] CR2: 000055c83b531008 CR3: 00000004736d0003 CR4: 00000000000606e0
[ 376.872433] Call Trace:
[ 376.875168] event_remove+0x72/0x120
[ 376.879159] trace_remove_event_call+0x79/0xd0
[ 376.884117] func_event_open+0xb1/0xd0
[ 376.888302] ? free_func_event+0x70/0x70
[ 376.892673] do_dentry_open+0x1b1/0x2d0
[ 376.896954] path_openat+0x602/0x14e0
[ 376.901041] do_filp_open+0x9b/0x110
[ 376.905032] ? __vfs_write+0x33/0x170
[ 376.909119] ? __check_object_size+0xaf/0x1b0
[ 376.913981] ? do_sys_open+0x1bd/0x250
[ 376.918164] do_sys_open+0x1bd/0x250
[ 376.922156] entry_SYSCALL_64_fastpath+0x20/0x83
[ 376.927299] RIP: 0033:0x7ff363ba01c0
[ 376.931287] RSP: 002b:00007ffdf21e4978 EFLAGS: 00000246
[ 376.931290] Code: e0 d9 2e bf e9 94 aa 6e 00 0f 1f 40 00 48 c7 c7 e0 d9 2e bf e9 54 5c f7 ff 0f 1f 40 00 53 48 8b 07 48 89 fb 48 8b 57 08 48 85 c0 <48> 89 02 74 04 48 89 50 08 48 b8 00 01 00 00 00 00 ad de 48 8d
[ 376.958209] RIP: __unregister_trace_event+0xe/0x70 RSP: ffffa643043cbc50
[ 376.965711] ---[ end trace b3dd6064ee6bc2f4 ]---