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[GIT PULL 0/3] perf/urgent fixes

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  [GIT PULL 0/3] perf/urgent fixes Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-02-03 18:10 +0100
    [PATCH 3/3] perf probe: Search both .eh_frame and .debug_frame sections for probe location Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-02-03 18:10 +0100
    [PATCH 1/3] perf tools: tracepoint_error() can receive e=NULL, robustify it Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-02-03 18:10 +0100
    [PATCH 2/3] perf tools: Fix thread lifetime related segfaut in intel_pt Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-02-03 18:10 +0100
    Re: [GIT PULL 0/3] perf/urgent fixes Ingo Molnar <mingo@kernel.org> - 2016-02-04 09:00 +0100

#1325691 — [GIT PULL 0/3] perf/urgent fixes

Hi Ingo,

	Please consider pulling,

- Arnaldo

The following changes since commit 28fb8a5b6e233fc384fb27f9f91f811b40ba9cf8:

  Merge tag 'perf-urgent-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/urgent (2016-01-30 09:15:49 +0100)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git tags/perf-urgent-for-mingo

for you to fetch changes up to 270bde1e76f400d81f8d0ab68905a18ee17fa2e8:

  perf probe: Search both .eh_frame and .debug_frame sections for probe location (2016-02-02 13:30:16 -0300)

----------------------------------------------------------------
perf/urgent fixes:

- tracepoint_error() can receive e=NULL, robustify it, fixes a problem noticed
  with a very specific combination: Machine with Intel PT (e.g. Broadwell),
  kernel with no perf_event_attr.context_switch feature (e.g. 4.2) and unreadable
  tracefs (for instance !root users), making the fallback from
  perf_event_attr.context_switch to the sched:sched_switch tracepoint to fail
  reading its info from tracefs, fix it. (Adrian Hunter)

- Fix segfault in intel pt, by making it follow the 'struct thread' lifetime cycle
  checking expectations, noticed for instance, when processing perf.data files with
  Intel PT data using 'perf script' and when exiting 'perf report' (Adrian Hunter)

- Fix CFI usage from .eh_frame and .debug_frame, which sometimes requires that we
  fallback from .eh_frame to .debug_frame in architectures such as PowerPC (Hemant Kumar)

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

----------------------------------------------------------------
Adrian Hunter (2):
      perf tools: tracepoint_error() can receive e=NULL, robustify it
      perf tools: Fix thread lifetime related segfaut in intel_pt

Hemant Kumar (1):
      perf probe: Search both .eh_frame and .debug_frame sections for probe location

 tools/perf/util/intel-pt.c     |  9 ++++++
 tools/perf/util/parse-events.c |  3 ++
 tools/perf/util/probe-finder.c | 62 +++++++++++++++++++++++++-----------------
 tools/perf/util/probe-finder.h |  5 +++-
 4 files changed, 53 insertions(+), 26 deletions(-)

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#1325692 — [PATCH 3/3] perf probe: Search both .eh_frame and .debug_frame sections for probe location

From: Hemant Kumar <hemant@linux.vnet.ibm.com>

'perf probe' through debuginfo__find_probes() in util/probe-finder.c
checks for the functions' frame descriptions in either .eh_frame section
of an ELF or the .debug_frame.

The check is based on whether either one of these sections is present.
Depending on distro, toolchain defaults, architetcutre, build flags,
etc., CFI might be found in either .eh_frame and/or .debug_frame.
Sometimes, it may happen that, .eh_frame, even if present, may not be
complete and may miss some descriptions.

Therefore, to be sure, to find the CFI covering an address we will
always have to investigate both if available.

For e.g., in powerpc, this may happen:
  $ gcc -g bin.c -o bin

  $ objdump --dwarf ./bin
  <1><145>: Abbrev Number: 7 (DW_TAG_subprogram)
     <146> DW_AT_external   : 1
     <146> DW_AT_name       : (indirect string, offset: 0x9e): main
     <14a> DW_AT_decl_file  : 1
     <14b> DW_AT_decl_line  : 39
     <14c> DW_AT_prototyped : 1
     <14c> DW_AT_type       : <0x57>
     <150> DW_AT_low_pc     : 0x100007b8

If the .eh_frame and .debug_frame are checked for the same binary, we
will find that, .eh_frame (although present) doesn't contain a
description for "main" function.

But, .debug_frame has a description:

  000000d8 00000024 00000000 FDE cie=00000000 pc=100007b8..10000838
    DW_CFA_advance_loc: 16 to 100007c8
    DW_CFA_def_cfa_offset: 144
    DW_CFA_offset_extended_sf: r65 at cfa+16
  ...

Due to this (since, perf checks whether .eh_frame is present and goes on
searching for that address inside that frame), perf is unable to process
the probes:

  # perf probe -x ./bin main
    Failed to get call frame on 0x100007b8
    Error: Failed to add events.

To avoid this issue, we need to check both the sections (.eh_frame and
.debug_frame), which is done in this patch.

Note that, we can always force everything into both .eh_frame and
.debug_frame by:

  $ gcc bin.c -fasynchronous-unwind-tables  -fno-dwarf2-cfi-asm -g -o bin

Signed-off-by: Hemant Kumar <hemant@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Mark Wielaard <mjw@redhat.com>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1454426806-13974-1-git-send-email-hemant@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/probe-finder.c | 62 +++++++++++++++++++++++++-----------------
 tools/perf/util/probe-finder.h |  5 +++-
 2 files changed, 41 insertions(+), 26 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 2be10fb27172..4ce5c5e18f48 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -686,8 +686,9 @@ static int call_probe_finder(Dwarf_Die *sc_die, struct probe_finder *pf)
 		pf->fb_ops = NULL;
 #if _ELFUTILS_PREREQ(0, 142)
 	} else if (nops == 1 && pf->fb_ops[0].atom == DW_OP_call_frame_cfa &&
-		   pf->cfi != NULL) {
-		if (dwarf_cfi_addrframe(pf->cfi, pf->addr, &frame) != 0 ||
+		   (pf->cfi_eh != NULL || pf->cfi_dbg != NULL)) {
+		if ((dwarf_cfi_addrframe(pf->cfi_eh, pf->addr, &frame) != 0 &&
+		     (dwarf_cfi_addrframe(pf->cfi_dbg, pf->addr, &frame) != 0)) ||
 		    dwarf_frame_cfa(frame, &pf->fb_ops, &nops) != 0) {
 			pr_warning("Failed to get call frame on 0x%jx\n",
 				   (uintmax_t)pf->addr);
@@ -1015,8 +1016,7 @@ static int pubname_search_cb(Dwarf *dbg, Dwarf_Global *gl, void *data)
 	return DWARF_CB_OK;
 }
 
-/* Find probe points from debuginfo */
-static int debuginfo__find_probes(struct debuginfo *dbg,
+static int debuginfo__find_probe_location(struct debuginfo *dbg,
 				  struct probe_finder *pf)
 {
 	struct perf_probe_point *pp = &pf->pev->point;
@@ -1025,27 +1025,6 @@ static int debuginfo__find_probes(struct debuginfo *dbg,
 	Dwarf_Die *diep;
 	int ret = 0;
 
-#if _ELFUTILS_PREREQ(0, 142)
-	Elf *elf;
-	GElf_Ehdr ehdr;
-	GElf_Shdr shdr;
-
-	/* Get the call frame information from this dwarf */
-	elf = dwarf_getelf(dbg->dbg);
-	if (elf == NULL)
-		return -EINVAL;
-
-	if (gelf_getehdr(elf, &ehdr) == NULL)
-		return -EINVAL;
-
-	if (elf_section_by_name(elf, &ehdr, &shdr, ".eh_frame", NULL) &&
-	    shdr.sh_type == SHT_PROGBITS) {
-		pf->cfi = dwarf_getcfi_elf(elf);
-	} else {
-		pf->cfi = dwarf_getcfi(dbg->dbg);
-	}
-#endif
-
 	off = 0;
 	pf->lcache = intlist__new(NULL);
 	if (!pf->lcache)
@@ -1108,6 +1087,39 @@ found:
 	return ret;
 }
 
+/* Find probe points from debuginfo */
+static int debuginfo__find_probes(struct debuginfo *dbg,
+				  struct probe_finder *pf)
+{
+	int ret = 0;
+
+#if _ELFUTILS_PREREQ(0, 142)
+	Elf *elf;
+	GElf_Ehdr ehdr;
+	GElf_Shdr shdr;
+
+	if (pf->cfi_eh || pf->cfi_dbg)
+		return debuginfo__find_probe_location(dbg, pf);
+
+	/* Get the call frame information from this dwarf */
+	elf = dwarf_getelf(dbg->dbg);
+	if (elf == NULL)
+		return -EINVAL;
+
+	if (gelf_getehdr(elf, &ehdr) == NULL)
+		return -EINVAL;
+
+	if (elf_section_by_name(elf, &ehdr, &shdr, ".eh_frame", NULL) &&
+	    shdr.sh_type == SHT_PROGBITS)
+		pf->cfi_eh = dwarf_getcfi_elf(elf);
+
+	pf->cfi_dbg = dwarf_getcfi(dbg->dbg);
+#endif
+
+	ret = debuginfo__find_probe_location(dbg, pf);
+	return ret;
+}
+
 struct local_vars_finder {
 	struct probe_finder *pf;
 	struct perf_probe_arg *args;
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index bed82716e1b4..0aec7704e395 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -76,7 +76,10 @@ struct probe_finder {
 
 	/* For variable searching */
 #if _ELFUTILS_PREREQ(0, 142)
-	Dwarf_CFI		*cfi;		/* Call Frame Information */
+	/* Call Frame Information from .eh_frame */
+	Dwarf_CFI		*cfi_eh;
+	/* Call Frame Information from .debug_frame */
+	Dwarf_CFI		*cfi_dbg;
 #endif
 	Dwarf_Op		*fb_ops;	/* Frame base attribute */
 	struct perf_probe_arg	*pvar;		/* Current target variable */
-- 
2.5.0

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#1325695 — [PATCH 1/3] perf tools: tracepoint_error() can receive e=NULL, robustify it

See http://www.infradead.org/rpr.html

From: Adrian Hunter <adrian.hunter@intel.com>

Fixes segmentation fault using, for instance:

  (gdb) run record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls
  Starting program: /home/acme/bin/perf record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls
  Missing separate debuginfos, use: dnf debuginfo-install glibc-2.22-7.fc23.x86_64
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib64/libthread_db.so.1".

 Program received signal SIGSEGV, Segmentation fault.
  0 x00000000004b9ea5 in tracepoint_error (e=0x0, err=13, sys=0x19b1370 "sched", name=0x19a5d00 "sched_switch") at util/parse-events.c:410
  (gdb) bt
  #0  0x00000000004b9ea5 in tracepoint_error (e=0x0, err=13, sys=0x19b1370 "sched", name=0x19a5d00 "sched_switch") at util/parse-events.c:410
  #1  0x00000000004b9fc5 in add_tracepoint (list=0x19a5d20, idx=0x7fffffffb8c0, sys_name=0x19b1370 "sched", evt_name=0x19a5d00 "sched_switch", err=0x0, head_config=0x0)
      at util/parse-events.c:433
  #2  0x00000000004ba334 in add_tracepoint_event (list=0x19a5d20, idx=0x7fffffffb8c0, sys_name=0x19b1370 "sched", evt_name=0x19a5d00 "sched_switch", err=0x0, head_config=0x0)
      at util/parse-events.c:498
  #3  0x00000000004bb699 in parse_events_add_tracepoint (list=0x19a5d20, idx=0x7fffffffb8c0, sys=0x19b1370 "sched", event=0x19a5d00 "sched_switch", err=0x0, head_config=0x0)
      at util/parse-events.c:936
  #4  0x00000000004f6eda in parse_events_parse (_data=0x7fffffffb8b0, scanner=0x19a49d0) at util/parse-events.y:391
  #5  0x00000000004bc8e5 in parse_events__scanner (str=0x663ff2 "sched:sched_switch", data=0x7fffffffb8b0, start_token=258) at util/parse-events.c:1361
  #6  0x00000000004bca57 in parse_events (evlist=0x19a5220, str=0x663ff2 "sched:sched_switch", err=0x0) at util/parse-events.c:1401
  #7  0x0000000000518d5f in perf_evlist__can_select_event (evlist=0x19a3b90, str=0x663ff2 "sched:sched_switch") at util/record.c:253
  #8  0x0000000000553c42 in intel_pt_track_switches (evlist=0x19a3b90) at arch/x86/util/intel-pt.c:364
  #9  0x00000000005549d1 in intel_pt_recording_options (itr=0x19a2c40, evlist=0x19a3b90, opts=0x8edf68 <record+232>) at arch/x86/util/intel-pt.c:664
  #10 0x000000000051e076 in auxtrace_record__options (itr=0x19a2c40, evlist=0x19a3b90, opts=0x8edf68 <record+232>) at util/auxtrace.c:539
  #11 0x0000000000433368 in cmd_record (argc=1, argv=0x7fffffffde60, prefix=0x0) at builtin-record.c:1264
  #12 0x000000000049bec2 in run_builtin (p=0x8fa2a8 <commands+168>, argc=5, argv=0x7fffffffde60) at perf.c:390
  #13 0x000000000049c12a in handle_internal_command (argc=5, argv=0x7fffffffde60) at perf.c:451
  #14 0x000000000049c278 in run_argv (argcp=0x7fffffffdcbc, argv=0x7fffffffdcb0) at perf.c:495
  #15 0x000000000049c60a in main (argc=5, argv=0x7fffffffde60) at perf.c:618
(gdb)

Intel PT attempts to find the sched:sched_switch tracepoint but that seg
faults if tracefs is not readable, because the error reporting structure
is null, as errors are not reported when automatically adding
tracepoints.  Fix by checking before using.

Committer note:

This doesn't take place in a kernel that supports
perf_event_attr.context_switch, that is the default way that will be
used for tracking context switches, only in older kernels, like 4.2, in
a machine with Intel PT (e.g. Broadwell) for non-priviledged users.

Further info from a similar patch by Wang:

The error is in tracepoint_error: it assumes the 'e' parameter is valid.

However, there are many situation a parse_event() can be called without
parse_events_error. See result of

  $ grep 'parse_events(.*NULL)' ./tools/perf/ -r'

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Tong Zhang <ztong@vt.edu>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: stable@vger.kernel.org # v4.4+
Fixes: 196581717d85 ("perf tools: Enhance parsing events tracepoint error output")
Link: http://lkml.kernel.org/r/1453809921-24596-2-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/parse-events.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 4f7b0efdde2f..813d9b272c81 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -399,6 +399,9 @@ static void tracepoint_error(struct parse_events_error *e, int err,
 {
 	char help[BUFSIZ];
 
+	if (!e)
+		return;
+
 	/*
 	 * We get error directly from syscall errno ( > 0),
 	 * or from encoded pointer's error ( < 0).
-- 
2.5.0

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#1325700 — [PATCH 2/3] perf tools: Fix thread lifetime related segfaut in intel_pt

See http://www.infradead.org/rpr.html

From: Adrian Hunter <adrian.hunter@intel.com>

intel_pt_process_auxtrace_info() creates a pt->unknown_thread thread
that eventually needs to be freed by the last thread__put() on it, when
its refcount hits zero, which may happen in
intel_pt_process_auxtrace_info() error handling path and triggers the
following segfault, which would happen as well at intel_pt_free, when
tools using this intel_pt codebase frees up resources:

  # perf record -I -e intel_pt/tsc=1,noretcomp=1/u /bin/ls
  0  a  anaconda-ks.cfg  bin   perf.data	perf.data.old  perf-f23-bringup.todo
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.217 MB perf.data ]
  #
  # perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs
  Samples for 'instructions:u' event do not have IREGS attribute set. Cannot print 'iregs' field.
  intel_pt_synth_events: failed to synthesize 'instructions' event type
  Segmentation fault (core dumped)
  #

The problem is: there's a union in 'struct thread' combines a list_head
and a rb_node. The standard life cycle of a thread is: init rb_node in
the constructor, insert it into machine->threads rbtree using rb_node,
move it to machine->dead_threads using list_head, clean in the last
thread__put: list_del_init(&thread->node).

In the above command, it clean a thread before adding it into list,
causes the above segfault.

Since pt->unknown_thread will never live in an rbtree, initialize its
list node so that when list_del_init() is done on it we don't segfault.

After this patch:

  # perf script -F event,comm,pid,tid,time,addr,ip,sym,dso,iregs
  Samples for 'instructions:u' event do not have IREGS attribute set. Cannot print 'iregs' field.
  intel_pt_synth_events: failed to synthesize 'instructions' event type
  0x248 [0x88]: failed to process type: 70
  #

Reported-by: Tong Zhang <ztong@vt.edu>
Reported-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Link: http://lkml.kernel.org/r/1454296865-19749-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/intel-pt.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index 81a2eb77ba7f..05d815851be1 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -2068,6 +2068,15 @@ int intel_pt_process_auxtrace_info(union perf_event *event,
 		err = -ENOMEM;
 		goto err_free_queues;
 	}
+
+	/*
+	 * Since this thread will not be kept in any rbtree not in a
+	 * list, initialize its list node so that at thread__put() the
+	 * current thread lifetime assuption is kept and we don't segfault
+	 * at list_del_init().
+	 */
+	INIT_LIST_HEAD(&pt->unknown_thread->node);
+
 	err = thread__set_comm(pt->unknown_thread, "unknown", 0);
 	if (err)
 		goto err_delete_thread;
-- 
2.5.0

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#1326467

* Arnaldo Carvalho de Melo <acme@kernel.org> wrote:

> Hi Ingo,
> 
> 	Please consider pulling,
> 
> - Arnaldo
> 
> The following changes since commit 28fb8a5b6e233fc384fb27f9f91f811b40ba9cf8:
> 
>   Merge tag 'perf-urgent-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/urgent (2016-01-30 09:15:49 +0100)
> 
> are available in the git repository at:
> 
>   git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git tags/perf-urgent-for-mingo
> 
> for you to fetch changes up to 270bde1e76f400d81f8d0ab68905a18ee17fa2e8:
> 
>   perf probe: Search both .eh_frame and .debug_frame sections for probe location (2016-02-02 13:30:16 -0300)
> 
> ----------------------------------------------------------------
> perf/urgent fixes:
> 
> - tracepoint_error() can receive e=NULL, robustify it, fixes a problem noticed
>   with a very specific combination: Machine with Intel PT (e.g. Broadwell),
>   kernel with no perf_event_attr.context_switch feature (e.g. 4.2) and unreadable
>   tracefs (for instance !root users), making the fallback from
>   perf_event_attr.context_switch to the sched:sched_switch tracepoint to fail
>   reading its info from tracefs, fix it. (Adrian Hunter)
> 
> - Fix segfault in intel pt, by making it follow the 'struct thread' lifetime cycle
>   checking expectations, noticed for instance, when processing perf.data files with
>   Intel PT data using 'perf script' and when exiting 'perf report' (Adrian Hunter)
> 
> - Fix CFI usage from .eh_frame and .debug_frame, which sometimes requires that we
>   fallback from .eh_frame to .debug_frame in architectures such as PowerPC (Hemant Kumar)
> 
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> 
> ----------------------------------------------------------------
> Adrian Hunter (2):
>       perf tools: tracepoint_error() can receive e=NULL, robustify it
>       perf tools: Fix thread lifetime related segfaut in intel_pt
> 
> Hemant Kumar (1):
>       perf probe: Search both .eh_frame and .debug_frame sections for probe location
> 
>  tools/perf/util/intel-pt.c     |  9 ++++++
>  tools/perf/util/parse-events.c |  3 ++
>  tools/perf/util/probe-finder.c | 62 +++++++++++++++++++++++++-----------------
>  tools/perf/util/probe-finder.h |  5 +++-
>  4 files changed, 53 insertions(+), 26 deletions(-)

Pulled, thanks a lot Arnaldo!

	Ingo

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