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349e8d2611
It is not easy for users to get the accurate byte offset or the line
number where a local variable can be probed.
With '--range' option, local variables in the scope of the probe point
are showed with a byte offset range, and can be added according to this
range information.
For example, there are some variables in the function
generic_perform_write():
<generic_perform_write@mm/filemap.c:0>
0 ssize_t generic_perform_write(struct file *file,
1 struct iov_iter *i, loff_t pos)
2 {
3 struct address_space *mapping = file->f_mapping;
4 const struct address_space_operations *a_ops = mapping->a_ops;
...
42 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
&page, &fsdata);
44 if (unlikely(status < 0))
But we fail when we try to probe the variable 'a_ops' at line 42 or 44.
$ perf probe --add 'generic_perform_write:42 a_ops'
Failed to find the location of a_ops at this address.
Perhaps, it has been optimized out.
This is because the source code do not match the assembly, so a variable
may not be available in the source code line where it appears.
After this patch, we can lookup the accurate byte offset range of a
variable, 'INV' indicates that this variable is not valid at the given
point, but available in the scope:
$ perf probe --vars 'generic_perform_write:42' --range
Available variables at generic_perform_write:42
@<generic_perform_write+141>
[INV] ssize_t written @<generic_perform_write+[324-331]>
[INV] struct address_space_operations* a_ops @<generic_perform_write+[55-61,170-176,223-246]>
[VAL] (unknown_type) fsdata @<generic_perform_write+[70-307,346-411]>
[VAL] loff_t pos @<generic_perform_write+[0-286,286-336,346-411]>
[VAL] long int status @<generic_perform_write+[83-342,346-411]>
[VAL] long unsigned int bytes @<generic_perform_write+[122-311,320-338,346-403,403-411]>
[VAL] struct address_space* mapping @<generic_perform_write+[35-344,346-411]>
[VAL] struct iov_iter* i @<generic_perform_write+[0-340,346-411]>
[VAL] struct page* page @<generic_perform_write+[70-307,346-411]>
Then it is more clear for us to add a probe with this variable:
$ perf probe --add 'generic_perform_write+170 a_ops'
Added new event:
probe:generic_perform_write (on generic_perform_write+170 with a_ops)
Signed-off-by: He Kuang <hekuang@huawei.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1431336304-16863-2-git-send-email-hekuang@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
126 lines
4.6 KiB
C
126 lines
4.6 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 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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