From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> To: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org>, namhyung@kernel.org, Ingo Molnar <mingo@kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org> Subject: Re: Re: [PATCH perf/core 1/2] [BUGFIX] perf-probe: Fix to handle optimized not-inlined but has no instance Date: Sun, 08 Feb 2015 17:37:08 +0900 Message-ID: <54D72034.2060304@hitachi.com> (raw) In-Reply-To: <20150130142135.GA3101@kernel.org> (2015/01/30 23:21), Arnaldo Carvalho de Melo wrote: > Em Fri, Jan 30, 2015 at 06:37:44PM +0900, Masami Hiramatsu escreveu: >> Fix to handle optimized no-inline functions which have >> only function definition but no actual instance at >> that point. To fix this problem, we need to find actual >> instance of the function. >> >> Without this patch: >> ---- >> # perf probe -a __up >> Failed to get entry address of __up. >> Error: Failed to add events. >> # perf probe -L __up >> Specified source line is not found. >> Error: Failed to show lines. >> ---- >> >> With this patch: >> ---- >> # perf probe -a __up >> Added new event: >> probe:__up (on __up) >> >> You can now use it in all perf tools, such as: >> >> perf record -e probe:__up -aR sleep 1 >> >> # perf probe -L __up >> <__up@/home/fedora/ksrc/linux-3/kernel/locking/semaphore.c:0> >> 0 static noinline void __sched __up(struct semaphore *sem) >> { >> struct semaphore_waiter *waiter = list_first_entry(&sem->wait_ >> struct semaphore_waite >> 4 list_del(&waiter->list); >> 5 waiter->up = true; >> 6 wake_up_process(waiter->task); >> 7 } >> ---- > > Since __up here was built in some other way, I looked for another > 'noinline' function to try, and it failed here: > > [root@zoo ~]# perf probe -L vmalloc_fault | head -5 > <vmalloc_fault@/home/git/linux/arch/x86/mm/fault.c:0> > 0 static noinline int vmalloc_fault(unsigned long address) > 1 { > pgd_t *pgd, *pgd_ref; > pud_t *pud, *pud_ref; > [root@zoo ~]# perf probe vmalloc_fault > Added new event: > Failed to write event: Invalid argument > Error: Failed to add events. > > ---->>>>>> APPLY THE PATCH, rebuild and try again: > > [root@zoo ~]# perf probe vmalloc_fault > Added new event: > Failed to write event: Invalid argument > Error: Failed to add events. > [root@zoo ~]# perf probe -v vmalloc_fault > probe-definition(0): vmalloc_fault > symbol:vmalloc_fault file:(null) line:0 offset:0 return:0 lazy:(null) > 0 arguments > Looking at the vmlinux_path (7 entries long) > Using /lib/modules/3.19.0-rc6+/build/vmlinux for symbols > Open Debuginfo file: /lib/modules/3.19.0-rc6+/build/vmlinux > Try to find probe point from debuginfo. > Probe point found: vmalloc_fault+0 > Found 1 probe_trace_events. > Opening /sys/kernel/debug/tracing/kprobe_events write=1 > Added new event: > Writing event: p:probe/vmalloc_fault _text+289600 > Failed to write event: Invalid argument > Error: Failed to add events. Reason: Invalid argument (Code: -22) > [root@zoo ~]# grep -w vmalloc_fault /proc/kallsyms > ffffffff81046b40 t vmalloc_fault > [root@zoo ~]# grep -w _text /proc/kallsyms > ffffffff81000000 T _text > [root@zoo ~]# python > Python 2.7.5 (default, Nov 3 2014, 14:26:24) > [GCC 4.8.3 20140911 (Red Hat 4.8.3-7)] on linux2 > Type "help", "copyright", "credits" or "license" for more information. > >>> 0xffffffff81046b40 - 0xffffffff81000000 > 289600L > >>> > [root@zoo ~]# readelf -s /lib/modules/3.19.0-rc6+/build/vmlinux | egrep -w _text\|vmalloc_fault > 3499: ffffffff81046b40 410 FUNC LOCAL DEFAULT 1 vmalloc_fault > 48873: ffffffff81000000 0 NOTYPE GLOBAL DEFAULT 1 _text > [root@zoo ~]# > > --------------------------------------------------------------------------- > > So perhaps I need a 'noinline' _and_ '__sched', so that I have a "optimized > no-inline functions which have only function definition but no actual instance > at that point"? Ok, actually vmalloc_fault is marked as a nokprobe symbol. $ grep vmalloc_fault -r arch/x86/ arch/x86/mm/fault.c:static noinline int vmalloc_fault(unsigned long address) arch/x86/mm/fault.c:NOKPROBE_SYMBOL(vmalloc_fault); arch/x86/mm/fault.c:static noinline int vmalloc_fault(unsigned long address) arch/x86/mm/fault.c:NOKPROBE_SYMBOL(vmalloc_fault); arch/x86/mm/fault.c: if (vmalloc_fault(address) >= 0) All the symbols which marked by NOKPROBE_SYMBOL macro can not be kprobed. And we now have <debugfs>/kprobes/blacklist special file to get all nokprobe symbols. I'll make another perf-probe patch which looks the blacklist before trying define new events. Thank you, > > Looking for one, will post here after objdump -dS finishes... > > - Arnaldo > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply index Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-01-30 9:37 [PATCH perf/core 0/2] perf-probe: bugfix and update Masami Hiramatsu 2015-01-30 9:37 ` [PATCH perf/core 1/2] [BUGFIX] perf-probe: Fix to handle optimized not-inlined but has no instance Masami Hiramatsu 2015-01-30 14:21 ` Arnaldo Carvalho de Melo 2015-01-30 14:32 ` Arnaldo Carvalho de Melo 2015-02-02 8:41 ` Masami Hiramatsu 2015-02-08 8:37 ` Masami Hiramatsu [this message] 2015-02-11 20:42 ` Arnaldo Carvalho de Melo 2015-02-19 14:31 ` [PATCH perf/core ] perf-probe: Check kprobes blacklist when adding new events Masami Hiramatsu 2015-02-25 21:50 ` Arnaldo Carvalho de Melo 2015-02-28 9:30 ` [tip:perf/core] perf probe: " tip-bot for Masami Hiramatsu 2015-02-18 18:25 ` [tip:perf/core] perf probe: Fix to handle optimized not-inlined functions tip-bot for Masami Hiramatsu 2015-01-30 9:37 ` [PATCH perf/core 2/2] [DOC] perf-probe: Update perf-probe document Masami Hiramatsu 2015-02-18 18:25 ` [tip:perf/core] perf probe: Update man page tip-bot for Masami Hiramatsu
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