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Ftrace startup test and boot-time tracing
Hi Steve, I found that if I enabled the CONFIG_FTRACE_STARTUP_TEST=y and booted the kernel with kprobe-events defined by boot-time tracing, a warning output. [ 59.803496] trace_kprobe: Testing kprobe tracing: [ 59.804258] ------------[ cut here ]------------ [ 59.805682] WARNING: CPU: 3 PID: 1 at kernel/trace/trace_kprobe.c:1987 kprobe_trace_self_tests_ib [ 59.806944] Modules linked in: [ 59.807335] CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.10.0-rc7+ torvalds#172 [ 59.808029] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/204 [ 59.808999] RIP: 0010:kprobe_trace_self_tests_init+0x5f/0x42b [ 59.809696] Code: e8 03 00 00 48 c7 c7 30 8e 07 82 e8 6d 3c 46 ff 48 c7 c6 00 b2 1a 81 48 c7 c7 7 [ 59.812439] RSP: 0018:ffffc90000013e78 EFLAGS: 00010282 [ 59.813038] RAX: 00000000ffffffef RBX: 0000000000000000 RCX: 0000000000049443 [ 59.813780] RDX: 0000000000049403 RSI: 0000000000049403 RDI: 000000000002deb0 [ 59.814589] RBP: ffffc90000013e90 R08: 0000000000000001 R09: 0000000000000001 [ 59.815349] R10: 0000000000000001 R11: 0000000000000000 R12: 00000000ffffffef [ 59.816138] R13: ffff888004613d80 R14: ffffffff82696940 R15: ffff888004429138 [ 59.816877] FS: 0000000000000000(0000) GS:ffff88807dcc0000(0000) knlGS:0000000000000000 [ 59.817772] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 59.818395] CR2: 0000000001a8dd38 CR3: 0000000002222000 CR4: 00000000000006a0 [ 59.819144] Call Trace: [ 59.819469] ? init_kprobe_trace+0x6b/0x6b [ 59.819948] do_one_initcall+0x5f/0x300 [ 59.820392] ? rcu_read_lock_sched_held+0x4f/0x80 [ 59.820916] kernel_init_freeable+0x22a/0x271 [ 59.821416] ? rest_init+0x241/0x241 [ 59.821841] kernel_init+0xe/0x10f [ 59.822251] ret_from_fork+0x22/0x30 [ 59.822683] irq event stamp: 16403349 [ 59.823121] hardirqs last enabled at (16403359): [<ffffffff810db81e>] console_unlock+0x48e/0x580 [ 59.824074] hardirqs last disabled at (16403368): [<ffffffff810db786>] console_unlock+0x3f6/0x580 [ 59.825036] softirqs last enabled at (16403200): [<ffffffff81c0033a>] __do_softirq+0x33a/0x484 [ 59.825982] softirqs last disabled at (16403087): [<ffffffff81a00f02>] asm_call_irq_on_stack+0x10 [ 59.827034] ---[ end trace 200c544775cdfeb3 ]--- [ 59.827635] trace_kprobe: error on probing function entry. This is actually similar issue which you had fixed with commit b6399cc ("tracing/kprobe: Do not run kprobe boot tests if kprobe_event is on cmdline"). Fixing this kprobes warning is easy (see attached below), but I think this has to be fixed widely, because other testcase also changes the boot-time tracing results or may not work correctly with it. There will be the 2 options, one is to change kconfig so that user can not select FTRACE_STARTUP_TEST if BOOTTIME_TRACING=y, another is to provide a flag from trace_boot and all tests checks the flag at runtime. (moreover, that flag will be good to be set from other command-line options) What would you think? Thank you, From 00037083baca07a8705da39852480f6f53a8297c Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu <mhiramat@kernel.org> Date: Mon, 7 Dec 2020 22:53:16 +0900 Subject: [PATCH] tracing/kprobes: Fix to skip kprobe-events startup test if kprobe-events is used commit b6399cc ("tracing/kprobe: Do not run kprobe boot tests if kprobe_event is on cmdline") had fixed the same issue with kprobe-events on kernel cmdline, but boot-time tracing re-introduce similar issue. When the boot-time tracing uses kprobe-events with ftrace startup test, it produced a warning on the kprobe-events startup test because the testcase doesn't expect any kprobe events exists. To mitigate the warning, skip the kprobe-events startup test if any kprobe-event is defined before starting the test. Fixes: 4d65528 ("tracing/boot Add kprobe event support") Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
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