Re: [PATCH] perf - probe finder fails to resolve function name toaddress

From: Prashanth Nageshappa
Date: Mon Mar 26 2012 - 05:52:29 EST

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On 03/23/2012 06:22 PM, Masami Hiramatsu wrote:

> Hi,
>
> (2012/03/22 19:23), Prashanth Nageshappa wrote:
>> probe finder fails to resolve valid function names into addresses for
>> functions which have more than one die entries in DWARF info.
>>
>> It is valid for DWARF info to contain more than 1 entries for a given
>> function name, where one entry corresponds to definition which has code
>> address/range attributes and remaining entries (which are only
>> declarations) does not have code address/range attributes.
>> (example: do_fork, sys_write, sys_wait4, sys_sync etc)
>
> Hmm, I'd like to reproduce and see what happened on debuginfo in those cases.
> Could you tell me your environment or actual dwarf dump of those entries as below?
>

$ uname -r
3.1.0-7.fc16.x86_64

$ sudo perf probe do_fork
Failed to get entry address of do_fork.
Error: Failed to add events. (-2)

$ readelf -wi /usr/lib/debug/lib/modules/3.1.0-7.fc16.x86_64/vmlinux | grep do_fork -A 16
<2691f7> DW_AT_name : (indirect string, offset: 0x1b1e0): do_fork
<2691fb> DW_AT_decl_file : 3
<2691fc> DW_AT_decl_line : 2269
<2691fe> DW_AT_prototyped : 1
<2691fe> DW_AT_type : <0x2593d1>
<269202> DW_AT_declaration : 1
<269202> DW_AT_sibling : <0x269225>
<2><269206>: Abbrev Number: 14 (DW_TAG_formal_parameter)
<269207> DW_AT_type : <0x259284>
<2><26920b>: Abbrev Number: 14 (DW_TAG_formal_parameter)
<26920c> DW_AT_type : <0x259284>
<2><269210>: Abbrev Number: 14 (DW_TAG_formal_parameter)
<269211> DW_AT_type : <0x25b2b1>
<2><269215>: Abbrev Number: 14 (DW_TAG_formal_parameter)
<269216> DW_AT_type : <0x259284>
<2><26921a>: Abbrev Number: 14 (DW_TAG_formal_parameter)
<26921b> DW_AT_type : <0x25a1f3>
--
<4015fc> DW_AT_name : (indirect string, offset: 0x266d7): do_fork_idle
<401600> DW_AT_decl_file : 3
<401601> DW_AT_decl_line : 638
<401603> DW_AT_prototyped : 1
<401603> DW_AT_low_pc : 0xffffffff814a32bb
<40160b> DW_AT_high_pc : 0xffffffff814a32dd
<401613> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa)
<401615> DW_AT_GNU_all_call_sites: 1
<401615> DW_AT_sibling : <0x40165b>
<2><401619>: Abbrev Number: 91 (DW_TAG_formal_parameter)
<40161a> DW_AT_name : (indirect string, offset: 0x10f8da): work
<40161e> DW_AT_decl_file : 3
<40161f> DW_AT_decl_line : 638
<401621> DW_AT_type : <0x3f96c9>
<401625> DW_AT_location : 0x7fb55 (location list)
<2><401629>: Abbrev Number: 110 (DW_TAG_variable)
<40162a> DW_AT_name : (indirect string, offset: 0x1109a7): c_idle
--
<679053> DW_AT_name : (indirect string, offset: 0x1b1e0): do_fork
<679057> DW_AT_decl_file : 25
<679058> DW_AT_decl_line : 2269
<67905a> DW_AT_prototyped : 1
<67905a> DW_AT_type : <0x66a9b5>
<67905e> DW_AT_declaration : 1
<67905e> DW_AT_sibling : <0x679081>
<2><679062>: Abbrev Number: 12 (DW_TAG_formal_parameter)
<679063> DW_AT_type : <0x66a872>
<2><679067>: Abbrev Number: 12 (DW_TAG_formal_parameter)
<679068> DW_AT_type : <0x66a872>
<2><67906c>: Abbrev Number: 12 (DW_TAG_formal_parameter)
<67906d> DW_AT_type : <0x66c935>
<2><679071>: Abbrev Number: 12 (DW_TAG_formal_parameter)
<679072> DW_AT_type : <0x66a872>
<2><679076>: Abbrev Number: 12 (DW_TAG_formal_parameter)
<679077> DW_AT_type : <0x66b877>
--
<723f0b> DW_AT_name : (indirect string, offset: 0x1b1e0): do_fork
<723f0f> DW_AT_decl_file : 4
<723f10> DW_AT_decl_line : 1476
<723f12> DW_AT_prototyped : 1
<723f12> DW_AT_type : <0x70caad>
<723f16> DW_AT_low_pc : 0xffffffff81056ee1
<723f1e> DW_AT_high_pc : 0xffffffff81057149
<723f26> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa)
<723f28> DW_AT_GNU_all_call_sites: 1
<723f28> DW_AT_sibling : <0x7244fd>
<2><723f2c>: Abbrev Number: 96 (DW_TAG_formal_parameter)
<723f2d> DW_AT_name : (indirect string, offset: 0x146df): clone_flags
<723f31> DW_AT_decl_file : 4
<723f32> DW_AT_decl_line : 1476
<723f34> DW_AT_type : <0x70ca0d>
<723f38> DW_AT_location : 0x10db3b (location list)
<2><723f3c>: Abbrev Number: 96 (DW_TAG_formal_parameter)
--
<33629b6> DW_AT_name : (indirect string, offset: 0x124058): run_do_fork_test
<33629ba> DW_AT_decl_file : 2
<33629bb> DW_AT_decl_line : 858
<33629bd> DW_AT_prototyped : 1
<33629bd> DW_AT_inline : 1 (inlined)
<1><33629be>: Abbrev Number: 71 (DW_TAG_subprogram)
<33629bf> DW_AT_name : (indirect string, offset: 0x123c3d): run_sys_open_test
<33629c3> DW_AT_decl_file : 2
<33629c4> DW_AT_decl_line : 867
<33629c6> DW_AT_prototyped : 1
<33629c6> DW_AT_inline : 1 (inlined)
<1><33629c7>: Abbrev Number: 64 (DW_TAG_subprogram)
<33629c8> DW_AT_name : (indirect string, offset: 0x123e9e): kgdbts_option_setup
<33629cc> DW_AT_decl_file : 2
<33629cd> DW_AT_decl_line : 985
<33629cf> DW_AT_prototyped : 1
<33629cf> DW_AT_type : <0x335570d>
--
<33651ea> DW_AT_name : (indirect string, offset: 0x12405c): do_fork_test
<33651ee> DW_AT_decl_file : 2
<33651ef> DW_AT_decl_line : 522
<33651f1> DW_AT_type : <0x33651d9>
<33651f5> DW_AT_location : 9 byte block: 3 30 87 a7 81 ff ff ff ff (DW_OP_addr: ffffffff81a78730)
<1><33651ff>: Abbrev Number: 122 (DW_TAG_variable)
<3365200> DW_AT_name : (indirect string, offset: 0x123c41): sys_open_test
<3365204> DW_AT_decl_file : 2
<3365205> DW_AT_decl_line : 540
<3365207> DW_AT_type : <0x33651d9>
<336520b> DW_AT_location : 9 byte block: 3 b0 88 a7 81 ff ff ff ff (DW_OP_addr: ffffffff81a788b0)
<1><3365215>: Abbrev Number: 122 (DW_TAG_variable)
<3365216> DW_AT_name : (indirect string, offset: 0x123b83): hw_breakpoint_test
<336521a> DW_AT_decl_file : 2
<336521b> DW_AT_decl_line : 558
<336521d> DW_AT_type : <0x3365167>
<3365221> DW_AT_location : 9 byte block: 3 30 8a a7 81 ff ff ff ff (DW_OP_addr: ffffffff81a78a30)

> At least we must consider this lazy_line case. If I understand correctly,
> that can also affect find_probe_point_lazy(sp_die, pf);
>
> If I find the different attribute, I'd like to add a checker function and
> filter it out at early step in this function.
>

Based on the above comments I have redone the patch:

If die entries corresponding to declarations appear before definition
entry, probe finder returns error instead of continuing to look further
for a definition entry.

This patch ensures we reach to the die entry corresponding to the
definition and get the function address.

V2: A simpler solution based on Masami's suggestion.

Signed-off-by: Prashanth Nageshappa <prashanth@xxxxxxxxxxxxxxxxxx>
---

tools/perf/util/probe-finder.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 5d73262..fc59df2 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -963,10 +963,11 @@ static int probe_point_search_cb(Dwarf_Die *sp_die, void *data)
struct dwarf_callback_param *param = data;
struct probe_finder *pf = param->data;
struct perf_probe_point *pp = &pf->pev->point;
+ Dwarf_Attribute attr;

/* Check tag and diename */
if (dwarf_tag(sp_die) != DW_TAG_subprogram ||
- !die_compare_name(sp_die, pp->function))
+ !die_compare_name(sp_die, pp->function) || dwarf_attr(sp_die, DW_AT_declaration, &attr))
return DWARF_CB_OK;

/* Check declared file */

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Next message: Viresh Kumar: "[PATCH] rtc/spear: Add Device Tree probing capability"
Previous message: Vinod Koul: "Re: [PATCH linux-next] dmaengine: add context parameter fixups"
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