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From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Clark Williams <williams@redhat.com>,
	linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
	Milian Wolff <milian.wolff@kdab.com>,
	Arnaldo Carvalho de Melo <acme@redhat.com>
Subject: [PATCH 12/28] perf unwind: Take pgoff into account when reporting elf to libdwfl
Date: Wed, 31 Oct 2018 13:44:52 -0300	[thread overview]
Message-ID: <20181031164508.4784-13-acme@kernel.org> (raw)
In-Reply-To: <20181031164508.4784-1-acme@kernel.org>

From: Milian Wolff <milian.wolff@kdab.com>

libdwfl parses an ELF file itself and creates mappings for the
individual sections. perf on the other hand sees raw mmap events which
represent individual sections. When we encounter an address pointing
into a mapping with pgoff != 0, we must take that into account and
report the file at the non-offset base address.

This fixes unwinding with libdwfl in some cases. E.g. for a file like:

```

using namespace std;

mutex g_mutex;

double worker()
{
    lock_guard<mutex> guard(g_mutex);
    uniform_real_distribution<double> uniform(-1E5, 1E5);
    default_random_engine engine;
    double s = 0;
    for (int i = 0; i < 1000; ++i) {
        s += norm(complex<double>(uniform(engine), uniform(engine)));
    }
    cout << s << endl;
    return s;
}

int main()
{
    vector<std::future<double>> results;
    for (int i = 0; i < 10000; ++i) {
        results.push_back(async(launch::async, worker));
    }
    return 0;
}
```

Compile it with `g++ -g -O2 -lpthread cpp-locking.cpp  -o cpp-locking`,
then record it with `perf record --call-graph dwarf -e
sched:sched_switch`.

When you analyze it with `perf script` and libunwind, you should see:

```
cpp-locking 20038 [005] 54830.236589: sched:sched_switch: prev_comm=cpp-locking prev_pid=20038 prev_prio=120 prev_state=T ==> next_comm=swapper/5 next_pid=0 next_prio=120
        ffffffffb166fec5 __sched_text_start+0x545 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb166fec5 __sched_text_start+0x545 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb1670208 schedule+0x28 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb16737cc rwsem_down_read_failed+0xec (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb1665e04 call_rwsem_down_read_failed+0x14 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb1672a03 down_read+0x13 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb106bd85 __do_page_fault+0x445 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb18015f5 page_fault+0x45 (/lib/modules/4.14.78-1-lts/build/vmlinux)
            7f38e4252591 new_heap+0x101 (/usr/lib/libc-2.28.so)
            7f38e4252d0b arena_get2.part.4+0x2fb (/usr/lib/libc-2.28.so)
            7f38e4255b1c tcache_init.part.6+0xec (/usr/lib/libc-2.28.so)
            7f38e42569e5 __GI___libc_malloc+0x115 (inlined)
            7f38e4241790 __GI__IO_file_doallocate+0x90 (inlined)
            7f38e424fbbf __GI__IO_doallocbuf+0x4f (inlined)
            7f38e424ee47 __GI__IO_file_overflow+0x197 (inlined)
            7f38e424df36 _IO_new_file_xsputn+0x116 (inlined)
            7f38e4242bfb __GI__IO_fwrite+0xdb (inlined)
            7f38e463fa6d std::basic_streambuf<char, std::char_traits<char> >::sputn(char const*, long)+0x1cd (inlined)
            7f38e463fa6d std::ostreambuf_iterator<char, std::char_traits<char> >::_M_put(char const*, long)+0x1cd (inlined)
            7f38e463fa6d std::ostreambuf_iterator<char, std::char_traits<char> > std::__write<char>(std::ostreambuf_iterator<char, std::char_traits<char> >, char const*, int)+0x1cd (inlined)
            7f38e463fa6d std::ostreambuf_iterator<char, std::char_traits<char> > std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_float<double>(std::ostreambuf_iterator<c>
            7f38e464bd70 std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, double) const+0x90 (inl>
            7f38e464bd70 std::ostream& std::ostream::_M_insert<double>(double)+0x90 (/usr/lib/libstdc++.so.6.0.25)
            563b9cb502f7 std::ostream::operator<<(double)+0xb7 (inlined)
            563b9cb502f7 worker()+0xb7 (/ssd/milian/projects/kdab/rnd/hotspot/build/tests/test-clients/cpp-locking/cpp-locking)
            563b9cb506fb double std::__invoke_impl<double, double (*)()>(std::__invoke_other, double (*&&)())+0x2b (inlined)
            563b9cb506fb std::__invoke_result<double (*)()>::type std::__invoke<double (*)()>(double (*&&)())+0x2b (inlined)
            563b9cb506fb decltype (__invoke((_S_declval<0ul>)())) std::thread::_Invoker<std::tuple<double (*)()> >::_M_invoke<0ul>(std::_Index_tuple<0ul>)+0x2b (inlined)
            563b9cb506fb std::thread::_Invoker<std::tuple<double (*)()> >::operator()()+0x2b (inlined)
            563b9cb506fb std::__future_base::_Task_setter<std::unique_ptr<std::__future_base::_Result<double>, std::__future_base::_Result_base::_Deleter>, std::thread::_Invoker<std::tuple<double (*)()> >, dou>
            563b9cb506fb std::_Function_handler<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> (), std::__future_base::_Task_setter<std::unique_ptr<std::__future_>
            563b9cb507e8 std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>::operator()() const+0x28 (inlined)
            563b9cb507e8 std::__future_base::_State_baseV2::_M_do_set(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*)+0x28 (/ssd/milian/>
            7f38e46d24fe __pthread_once_slow+0xbe (/usr/lib/libpthread-2.28.so)
            563b9cb51149 __gthread_once+0xe9 (inlined)
            563b9cb51149 void std::call_once<void (std::__future_base::_State_baseV2::*)(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>*, bool*)>
            563b9cb51149 std::__future_base::_State_baseV2::_M_set_result(std::function<std::unique_ptr<std::__future_base::_Result_base, std::__future_base::_Result_base::_Deleter> ()>, bool)+0xe9 (inlined)
            563b9cb51149 std::__future_base::_Async_state_impl<std::thread::_Invoker<std::tuple<double (*)()> >, double>::_Async_state_impl(std::thread::_Invoker<std::tuple<double (*)()> >&&)::{lambda()#1}::op>
            563b9cb51149 void std::__invoke_impl<void, std::__future_base::_Async_state_impl<std::thread::_Invoker<std::tuple<double (*)()> >, double>::_Async_state_impl(std::thread::_Invoker<std::tuple<double>
            563b9cb51149 std::__invoke_result<std::__future_base::_Async_state_impl<std::thread::_Invoker<std::tuple<double (*)()> >, double>::_Async_state_impl(std::thread::_Invoker<std::tuple<double (*)()> >>
            563b9cb51149 decltype (__invoke((_S_declval<0ul>)())) std::thread::_Invoker<std::tuple<std::__future_base::_Async_state_impl<std::thread::_Invoker<std::tuple<double (*)()> >, double>::_Async_state_>
            563b9cb51149 std::thread::_Invoker<std::tuple<std::__future_base::_Async_state_impl<std::thread::_Invoker<std::tuple<double (*)()> >, double>::_Async_state_impl(std::thread::_Invoker<std::tuple<dou>
            563b9cb51149 std::thread::_State_impl<std::thread::_Invoker<std::tuple<std::__future_base::_Async_state_impl<std::thread::_Invoker<std::tuple<double (*)()> >, double>::_Async_state_impl(std::thread>
            7f38e45f0062 execute_native_thread_routine+0x12 (/usr/lib/libstdc++.so.6.0.25)
            7f38e46caa9c start_thread+0xfc (/usr/lib/libpthread-2.28.so)
            7f38e42ccb22 __GI___clone+0x42 (inlined)
```

Before this patch, using libdwfl, you would see:

```
cpp-locking 20038 [005] 54830.236589: sched:sched_switch: prev_comm=cpp-locking prev_pid=20038 prev_prio=120 prev_state=T ==> next_comm=swapper/5 next_pid=0 next_prio=120
        ffffffffb166fec5 __sched_text_start+0x545 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb166fec5 __sched_text_start+0x545 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb1670208 schedule+0x28 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb16737cc rwsem_down_read_failed+0xec (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb1665e04 call_rwsem_down_read_failed+0x14 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb1672a03 down_read+0x13 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb106bd85 __do_page_fault+0x445 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb18015f5 page_fault+0x45 (/lib/modules/4.14.78-1-lts/build/vmlinux)
            7f38e4252591 new_heap+0x101 (/usr/lib/libc-2.28.so)
        a041161e77950c5c [unknown] ([unknown])
```

With this patch applied, we get a bit further in unwinding:

```
cpp-locking 20038 [005] 54830.236589: sched:sched_switch: prev_comm=cpp-locking prev_pid=20038 prev_prio=120 prev_state=T ==> next_comm=swapper/5 next_pid=0 next_prio=120
        ffffffffb166fec5 __sched_text_start+0x545 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb166fec5 __sched_text_start+0x545 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb1670208 schedule+0x28 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb16737cc rwsem_down_read_failed+0xec (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb1665e04 call_rwsem_down_read_failed+0x14 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb1672a03 down_read+0x13 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb106bd85 __do_page_fault+0x445 (/lib/modules/4.14.78-1-lts/build/vmlinux)
        ffffffffb18015f5 page_fault+0x45 (/lib/modules/4.14.78-1-lts/build/vmlinux)
            7f38e4252591 new_heap+0x101 (/usr/lib/libc-2.28.so)
            7f38e4252d0b arena_get2.part.4+0x2fb (/usr/lib/libc-2.28.so)
            7f38e4255b1c tcache_init.part.6+0xec (/usr/lib/libc-2.28.so)
            7f38e42569e5 __GI___libc_malloc+0x115 (inlined)
            7f38e4241790 __GI__IO_file_doallocate+0x90 (inlined)
            7f38e424fbbf __GI__IO_doallocbuf+0x4f (inlined)
            7f38e424ee47 __GI__IO_file_overflow+0x197 (inlined)
            7f38e424df36 _IO_new_file_xsputn+0x116 (inlined)
            7f38e4242bfb __GI__IO_fwrite+0xdb (inlined)
            7f38e463fa6d std::basic_streambuf<char, std::char_traits<char> >::sputn(char const*, long)+0x1cd (inlined)
            7f38e463fa6d std::ostreambuf_iterator<char, std::char_traits<char> >::_M_put(char const*, long)+0x1cd (inlined)
            7f38e463fa6d std::ostreambuf_iterator<char, std::char_traits<char> > std::__write<char>(std::ostreambuf_iterator<char, std::char_traits<char> >, char const*, int)+0x1cd (inlined)
            7f38e463fa6d std::ostreambuf_iterator<char, std::char_traits<char> > std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_M_insert_float<double>(std::ostreambuf_iterator<c>
            7f38e464bd70 std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, double) const+0x90 (inl>
            7f38e464bd70 std::ostream& std::ostream::_M_insert<double>(double)+0x90 (/usr/lib/libstdc++.so.6.0.25)
            563b9cb502f7 std::ostream::operator<<(double)+0xb7 (inlined)
            563b9cb502f7 worker()+0xb7 (/ssd/milian/projects/kdab/rnd/hotspot/build/tests/test-clients/cpp-locking/cpp-locking)
        6eab825c1ee3e4ff [unknown] ([unknown])
```

Note that the backtrace is still stopping too early, when compared to
the nice results obtained via libunwind. It's unclear so far what the
reason for that is.

Committer note:

Further comment by Milian on the thread started on the Link: tag below:

 ---
The remaining issue is due to a bug in elfutils:

https://sourceware.org/ml/elfutils-devel/2018-q4/msg00089.html

With both patches applied, libunwind and elfutils produce the same output for
the above scenario.
 ---

Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20181029141644.3907-1-milian.wolff@kdab.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/unwind-libdw.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c
index 6f318b15950e..5eff9bfc5758 100644
--- a/tools/perf/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw.c
@@ -45,13 +45,13 @@ static int __report_module(struct addr_location *al, u64 ip,
 		Dwarf_Addr s;
 
 		dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
-		if (s != al->map->start)
+		if (s != al->map->start - al->map->pgoff)
 			mod = 0;
 	}
 
 	if (!mod)
 		mod = dwfl_report_elf(ui->dwfl, dso->short_name,
-				      (dso->symsrc_filename ? dso->symsrc_filename : dso->long_name), -1, al->map->start,
+				      (dso->symsrc_filename ? dso->symsrc_filename : dso->long_name), -1, al->map->start - al->map->pgoff,
 				      false);
 
 	return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
-- 
2.14.4


  parent reply	other threads:[~2018-10-31 16:47 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-31 16:44 [GIT PULL 00/24] perf/urgent improvements and fixes Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 01/28] tools include uapi: Grab a copy of linux/fs.h Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 02/28] perf beauty: Add a generator for MS_ mount/umount's flag constants Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 03/28] perf beauty: Switch from GPL v2.0 to LGPL v2.1 Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 04/28] perf beauty: Introduce strarray__scnprintf_flags() Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 05/28] perf trace beauty: Allow syscalls to mask an argument before considering it Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 06/28] perf trace beauty: Beautify mount/umount's 'flags' argument Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 07/28] perf trace: Consider syscall aliases too Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 08/28] perf trace: Beautify the umount's 'name' argument Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 09/28] perf trace: Beautify mount's first pathname arg Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 10/28] perf top: Allow disabling the overwrite mode Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 11/28] perf top: Do not use overwrite mode by default Arnaldo Carvalho de Melo
2018-10-31 16:44 ` Arnaldo Carvalho de Melo [this message]
2018-10-31 16:44 ` [PATCH 13/28] perf cs-etm: Correct CPU mode for samples Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 14/28] perf callchain: Honour the ordering of PERF_CONTEXT_{USER,KERNEL,etc} Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 15/28] tools include uapi: Update linux/fs.h copy Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 16/28] tools arch uapi: Update asm-generic/unistd.h and arm64 unistd.h copies Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 17/28] tools include uapi: Update asound.h copy Arnaldo Carvalho de Melo
2018-10-31 17:00   ` Takashi Iwai
2018-10-31 17:27     ` Joe Perches
2018-10-31 18:32       ` Takashi Iwai
2018-10-31 19:29       ` Arnaldo Carvalho de Melo
2018-11-01 11:54         ` Takashi Sakamoto
2018-11-01 13:04           ` Arnaldo Carvalho de Melo
2018-11-01 13:57             ` Takashi Sakamoto
2018-10-31 19:28     ` Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 18/28] perf beauty: Add a generator for MAP_ mmap's flag constants Arnaldo Carvalho de Melo
2018-10-31 16:44 ` [PATCH 19/28] perf beauty: Wire up the mmap flags table generator to the Makefile Arnaldo Carvalho de Melo
2018-11-05 15:44   ` Guenter Roeck
2018-11-05 17:11     ` Arnaldo Carvalho de Melo
2018-11-05 18:46       ` Arnaldo Carvalho de Melo
2018-11-05 19:13         ` Arnaldo Carvalho de Melo
2018-11-05 21:18           ` Guenter Roeck
2018-11-06 19:18         ` [tip:perf/urgent] perf beauty: Use SRCARCH, ARCH=x86_64 must map to "x86" to find the headers tip-bot for Arnaldo Carvalho de Melo
2018-10-31 16:45 ` [PATCH 20/28] perf trace beauty: Use the mmap flags table generated from headers Arnaldo Carvalho de Melo
2018-10-31 16:45 ` [PATCH 21/28] tools include uapi: Update linux/mmap.h copy Arnaldo Carvalho de Melo
2018-10-31 16:45 ` [PATCH 22/28] tools headers: Sync the various kvm.h header copies Arnaldo Carvalho de Melo
2018-10-31 16:45 ` [PATCH 23/28] tools headers uapi: Update linux/netlink.h header copy Arnaldo Carvalho de Melo
2018-10-31 16:45 ` [PATCH 24/28] tools headers uapi: Update linux/if_link.h " Arnaldo Carvalho de Melo
2018-10-31 16:45 ` [PATCH 25/28] perf top: Start display thread earlier Arnaldo Carvalho de Melo
2018-10-31 16:45 ` [PATCH 26/28] perf tools: Don't clone maps from parent when synthesizing forks Arnaldo Carvalho de Melo
2018-10-31 16:45 ` [PATCH 27/28] perf intel-pt: Insert callchain context into synthesized callchains Arnaldo Carvalho de Melo
2018-10-31 16:45 ` [PATCH 28/28] perf intel-pt/bts: Calculate cpumode for synthesized samples Arnaldo Carvalho de Melo
2018-10-31 21:56 ` [GIT PULL 00/24] perf/urgent improvements and fixes Ingo Molnar

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