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perf probe currently errors out if there are any tail calls to probed
functions:
[root@rhel71be]# perf probe do_fork
Failed to find probe point in any functions.
Error: Failed to add events.
Fix this by teaching perf to ignore tail calls.
Without patch:
[root@rhel71be perf]# ./perf probe -v do_fork
probe-definition(0): do_fork symbol:do_fork file:(null) line:0 offset:0
return:0 lazy:(null)
0 arguments
Looking at the vmlinux_path (7 entries long)
symsrc__init: build id mismatch for /boot/vmlinux.
Using /usr/lib/debug/lib/modules/3.10.0-201.el7.ppc64/vmlinux for symbols
Open Debuginfo file:
/usr/lib/debug/lib/modules/3.10.0-201.el7.ppc64/vmlinux
Try to find probe point from debuginfo.
found inline addr: 0xc0000000000bb9b0
Probe point found: do_fork+0
found inline addr: 0xc0000000000bbe20
Probe point found: kernel_thread+48
found inline addr: 0xc0000000000bbe5c
Probe point found: sys_fork+28
found inline addr: 0xc0000000000bbfac
Probe point found: sys_vfork+44
found inline addr: 0xc0000000000bc27c
Failed to find probe point in any functions.
An error occurred in debuginfo analysis (-2).
Error: Failed to add events. Reason: No such file or directory (Code: -2)
With patch:
[root@rhel71be perf]# ./perf probe -v do_fork
probe-definition(0): do_fork symbol:do_fork file:(null) line:0 offset:0
return:0 lazy:(null)
0 arguments
Looking at the vmlinux_path (7 entries long)
symsrc__init: build id mismatch for /boot/vmlinux.
Using /usr/lib/debug/lib/modules/3.10.0-201.el7.ppc64/vmlinux for symbols
Open Debuginfo file:
/usr/lib/debug/lib/modules/3.10.0-201.el7.ppc64/vmlinux
Try to find probe point from debuginfo.
found inline addr: 0xc0000000000bb9b0
Probe point found: do_fork+0
found inline addr: 0xc0000000000bbe20
Probe point found: kernel_thread+48
found inline addr: 0xc0000000000bbe5c
Probe point found: sys_fork+28
found inline addr: 0xc0000000000bbfac
Probe point found: sys_vfork+44
found inline addr: 0xc0000000000bc27c
Ignoring tail call from SyS_clone
Found 4 probe_trace_events.
Opening /sys/kernel/debug/tracing/kprobe_events write=1
No kprobe blacklist support, ignored
Added new events:
Writing event: p:probe/do_fork _text+768432
Failed to write event: Invalid argument
Error: Failed to add events. Reason: Invalid argument (Code: -22)
[Ignore the error about failure to write event - this kernel is missing
a patch to resolve _text properly]
The reason to ignore tail calls is that the address does not belong to
any function frame. In the example above, the address in SyS_clone is
0xc0000000000bc27c, but looking at the debug-info:
<1><830081>: Abbrev Number: 133 (DW_TAG_subprogram)
<830083> DW_AT_external : 1
<830083> DW_AT_name : (indirect string, offset: 0x3cea3): SyS_clone
<830087> DW_AT_decl_file : 7
<830088> DW_AT_decl_line : 1689
<83008a> DW_AT_prototyped : 1
<83008a> DW_AT_type : <0x8110eb>
<83008e> DW_AT_low_pc : 0xc0000000000bc270
<830096> DW_AT_high_pc : 0xc
<83009e> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa)
<8300a0> DW_AT_GNU_all_call_sites: 1
<8300a0> DW_AT_sibling : <0x830178>
<snip>
<3><830147>: Abbrev Number: 125 (DW_TAG_GNU_call_site)
<830148> DW_AT_low_pc : 0xc0000000000bc27c
<830150> DW_AT_GNU_tail_call: 1
<830150> DW_AT_abstract_origin: <0x82e7e1>
The frame ends at 0xc0000000000bc27c. I suppose this is why this
particular call is a "tail" call. FWIW, systemtap seems to ignore these
as well and requires users to explicitly place probes at these call
sites if necessary. I print out the caller so that users know.
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Link: http://lkml.kernel.org/r/1430394151-15928-1-git-send-email-naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
131 lines
4.8 KiB
C
131 lines
4.8 KiB
C
#ifndef _DWARF_AUX_H
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#define _DWARF_AUX_H
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/*
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* dwarf-aux.h : libdw auxiliary interfaces
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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*/
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#include <dwarf.h>
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#include <elfutils/libdw.h>
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#include <elfutils/libdwfl.h>
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#include <elfutils/version.h>
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/* Find the realpath of the target file */
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extern const char *cu_find_realpath(Dwarf_Die *cu_die, const char *fname);
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/* Get DW_AT_comp_dir (should be NULL with older gcc) */
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extern const char *cu_get_comp_dir(Dwarf_Die *cu_die);
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/* Get a line number and file name for given address */
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extern int cu_find_lineinfo(Dwarf_Die *cudie, unsigned long addr,
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const char **fname, int *lineno);
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/* Walk on funcitons at given address */
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extern int cu_walk_functions_at(Dwarf_Die *cu_die, Dwarf_Addr addr,
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int (*callback)(Dwarf_Die *, void *), void *data);
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/* Ensure that this DIE is a subprogram and definition (not declaration) */
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extern bool die_is_func_def(Dwarf_Die *dw_die);
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/* Ensure that this DIE is an instance of a subprogram */
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extern bool die_is_func_instance(Dwarf_Die *dw_die);
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/* Compare diename and tname */
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extern bool die_compare_name(Dwarf_Die *dw_die, const char *tname);
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/* Matching diename with glob pattern */
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extern bool die_match_name(Dwarf_Die *dw_die, const char *glob);
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/* Get callsite line number of inline-function instance */
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extern int die_get_call_lineno(Dwarf_Die *in_die);
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/* Get callsite file name of inlined function instance */
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extern const char *die_get_call_file(Dwarf_Die *in_die);
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/* Get type die */
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extern Dwarf_Die *die_get_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem);
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/* Get a type die, but skip qualifiers and typedef */
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extern Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem);
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/* Check whether the DIE is signed or not */
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extern bool die_is_signed_type(Dwarf_Die *tp_die);
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/* Get data_member_location offset */
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extern int die_get_data_member_location(Dwarf_Die *mb_die, Dwarf_Word *offs);
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/* Return values for die_find_child() callbacks */
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enum {
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DIE_FIND_CB_END = 0, /* End of Search */
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DIE_FIND_CB_CHILD = 1, /* Search only children */
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DIE_FIND_CB_SIBLING = 2, /* Search only siblings */
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DIE_FIND_CB_CONTINUE = 3, /* Search children and siblings */
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};
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/* Search child DIEs */
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extern Dwarf_Die *die_find_child(Dwarf_Die *rt_die,
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int (*callback)(Dwarf_Die *, void *),
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void *data, Dwarf_Die *die_mem);
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/* Search a non-inlined function including given address */
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extern Dwarf_Die *die_find_realfunc(Dwarf_Die *cu_die, Dwarf_Addr addr,
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Dwarf_Die *die_mem);
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/* Search a non-inlined function with tail call at given address */
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Dwarf_Die *die_find_tailfunc(Dwarf_Die *cu_die, Dwarf_Addr addr,
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Dwarf_Die *die_mem);
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/* Search the top inlined function including given address */
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extern Dwarf_Die *die_find_top_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
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Dwarf_Die *die_mem);
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/* Search the deepest inlined function including given address */
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extern Dwarf_Die *die_find_inlinefunc(Dwarf_Die *sp_die, Dwarf_Addr addr,
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Dwarf_Die *die_mem);
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/* Walk on the instances of given DIE */
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extern int die_walk_instances(Dwarf_Die *in_die,
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int (*callback)(Dwarf_Die *, void *), void *data);
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/* Walker on lines (Note: line number will not be sorted) */
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typedef int (* line_walk_callback_t) (const char *fname, int lineno,
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Dwarf_Addr addr, void *data);
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/*
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* Walk on lines inside given DIE. If the DIE is a subprogram, walk only on
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* the lines inside the subprogram, otherwise the DIE must be a CU DIE.
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*/
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extern int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback,
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void *data);
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/* Find a variable called 'name' at given address */
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extern Dwarf_Die *die_find_variable_at(Dwarf_Die *sp_die, const char *name,
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Dwarf_Addr addr, Dwarf_Die *die_mem);
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/* Find a member called 'name' */
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extern Dwarf_Die *die_find_member(Dwarf_Die *st_die, const char *name,
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Dwarf_Die *die_mem);
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/* Get the name of given variable DIE */
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extern int die_get_typename(Dwarf_Die *vr_die, struct strbuf *buf);
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/* Get the name and type of given variable DIE, stored as "type\tname" */
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extern int die_get_varname(Dwarf_Die *vr_die, struct strbuf *buf);
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extern int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_die,
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struct strbuf *buf);
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#endif
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