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    SubjectRe: [PATCH] perf - probe finder fails to resolve function name to address
    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@linux.vnet.ibm.com>
    ---

    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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