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Re: [Patch RFC] Tolerate if nsrcs>1 in iterate_over_srcfile_lines
- From: Jia He <hejianet at gmail dot com>
- To: "Frank Ch. Eigler" <fche at redhat dot com>
- Cc: systemtap at sourceware dot org
- Date: Tue, 18 Jun 2013 08:31:43 +0800
- Subject: Re: [Patch RFC] Tolerate if nsrcs>1 in iterate_over_srcfile_lines
- References: <CAL+6Mkdtb6=0E0GrSk6fWWbO8TxRg51T9orWtYguKs=+ucamUQ at mail dot gmail dot com> <y0m7ghym4jv dot fsf at fche dot csb> <CAL+6Mkf+erf4Av7v5zck-z-uZ9N-AifoJhXMhPLT7LZHqb3VBQ at mail dot gmail dot com>
Hi Frank, Do u agree or disagree with my analysis?
On Fri, Jun 14, 2013 at 10:13 AM, Jia He <hejianet@gmail.com> wrote:
> On Thu, Jun 13, 2013 at 11:08 PM, Frank Ch. Eigler <fche@redhat.com> wrote:
>> Jia He <hejianet@gmail.com> writes:
>>
>>> Now if dwarf_getsrc_file returns by nsrcs>1 in
>>> dwflpp::iterate_over_srcfile_lines,
>>> The loop for (int l = lineno; ; l = l + 1) will not be continued.
>>> But actually it is not correct in some cases.
>>
>> Could you elaborate why you think it is incorrect? Some of the
>> filtering is done deliberately, for example if the compiler debuginfo
>> cannot give an unambiguous starting PC-address for a source-level
>> statement.
> Maybe I don't understand the codes correctly, please correct me if possible.
> the related readelf info for hrtimer.o(ppc64) is as follows:
> #readelf --debug-dump=decodedline hrtimer.o
> ...
> hrtimer.c 1601 0x2040
> hrtimer.c 1605 0x2050
> hrtimer.c 1601 0x2054
> hrtimer.c 1605 0x205c
> hrtimer.c 1601 0x207c
> hrtimer.c 1608 0x20a0
> hrtimer.c 1611 0x20ac
> hrtimer.c 1608 0x20b4
> hrtimer.c 1611 0x20c8
> ...
> the objdump info(ppc64):
> 0000000000002040 <.SyS_nanosleep>:
> 2040: 7c 08 02 a6 mflr r0
> 2044: fb a1 ff e8 std r29,-24(r1)
> 2048: fb e1 ff f8 std r31,-8(r1)
> 204c: 7c 9d 23 78 mr r29,r4
> 2050: 38 a0 00 10 li r5,16
> 2054: f8 01 00 10 std r0,16(r1)
> 2058: f8 21 ff 61 stdu r1,-160(r1)
> 205c: 7c 64 1b 78 mr r4,r3
> 2060: 3b e1 00 70 addi r31,r1,112
> 2064: 7f e3 fb 78 mr r3,r31
> 2068: 48 00 00 01 bl 2068 <.SyS_nanosleep+0x28>
> 206c: 60 00 00 00 nop
> 2070: 38 00 ff f2 li r0,-14
> 2074: 2f a3 00 00 cmpdi cr7,r3,0
> 2078: 41 9e 00 28 beq- cr7,20a0 <.SyS_nanosleep+0x60>
> 207c: 38 21 00 a0 addi r1,r1,160
> 2080: 7c 03 03 78 mr r3,r0
> 2084: e8 01 00 10 ld r0,16(r1)
> 2088: eb a1 ff e8 ld r29,-24(r1)
> 208c: eb e1 ff f8 ld r31,-8(r1)
> 2090: 7c 08 03 a6 mtlr r0
> 2094: 4e 80 00 20 blr
> 2098: 60 00 00 00 nop
> 209c: 60 00 00 00 nop
> 20a0: e8 01 00 70 ld r0,112(r1)
> 20a4: 2f a0 00 00 cmpdi cr7,r0,0
> 20a8: 40 9c 00 0c bge- cr7,20b4 <.SyS_nanosleep+0x74>
> 20ac: 38 00 ff ea li r0,-22
> 20b0: 4b ff ff cc b 207c <.SyS_nanosleep+0x3c>
> 20b4: 3c 00 3b 9a lis r0,15258
> 20b8: e9 21 00 78 ld r9,120(r1)
> 20bc: 60 00 c9 ff ori r0,r0,51711
> 20c0: 7f a9 00 40 cmpld cr7,r9,r0
> 20c4: 41 9d ff e8 bgt+ cr7,20ac <.SyS_nanosleep+0x6c>
> 20c8: 7f e3 fb 78 mr r3,r31
> 20cc: 7f a4 eb 78 mr r4,r29
> 20d0: 38 a0 00 01 li r5,1
> 20d4: 38 c0 00 01 li r6,1
> 20d8: 48 00 00 01 bl 20d8 <.SyS_nanosleep+0x98>
> 20dc: 7c 60 1b 78 mr r0,r3
> 20e0: 4b ff ff 9c b 207c <.SyS_nanosleep+0x3c>
>
> Seems if l=1601 or 1605 or 1608 in the loop for (int l = lineno; ; l = l + 1)
> the nsrcs will return >1 after dwarf_getsrc_file().
> So the old logic will regard it as sth abnormal and will not consider
> it is valid
> and will not insert it to lines_probed. Do u think the old logic is incorrect?
>>
>>> --- systemtap-2.2.1.orig/dwflpp.cxx 2013-05-16 10:30:37.000000000 -0400
>>> +++ systemtap-2.2.1/dwflpp.cxx 2013-06-13 01:59:52.000000000 -0400
>>> @@ -1619,7 +1619,7 @@ dwflpp::iterate_over_srcfile_lines (char
>>> if (line_type == RANGE && lineno > lines[1])
>>> break;
>>> line_probed = lines_probed.insert(lineno);
>>> - if (lineno != l || line_probed.second == false || nsrcs > 1)
>>> + if (lineno != l || line_probed.second == false)
>>> continue;
>>> dwarf_lineaddr (srcsp [0], &line_addr);
>>> if (!function_name_matches(func_pattern) && dwarf_haspc
>>> (function, line_addr) != 1)
>>
>> For example, this change would ignore srcsp[n] for n>0, which would
>> need an explanation about how that could come about and why we can
>> ignore them.
>>
>>
>>> advice << srcfile << ":" << hi_try;
>>> advice << ")";
>>> }
>>> - throw semantic_error (advice.str());
>>> + if (sess.verbose > 0)
>>> + clog<<advice.str();
>>> +// throw semantic_error (advice.str());
>>> }
>>
>> What would be the purpose of this change?
> If it throws the error message, the loop will not be continued and the
> following "l"
> will not be checked.
>>
>>
>>> test result
>>> command:stap -L 'kernel.statement("sys_nanosleep@kernel/hrtimer.c:*")'
>>> in X86_64)
>>> Before this patch:
>>> kernel.statement("sys_nanosleep@kernel/hrtimer.c:1612") $rmtp:struct
>>> timespec* $tu:struct timespec
>>>
>>> After this patch:
>>> kernel.statement("sys_nanosleep@kernel/hrtimer.c:1602") $rqtp:struct
>>> timespec* $rmtp:struct timespec* $tu:struct timespec
>>> kernel.statement("sys_nanosleep@kernel/hrtimer.c:1605") $rqtp:struct
>>> timespec* $rmtp:struct timespec* $tu:struct timespec
>>> kernel.statement("sys_nanosleep@kernel/hrtimer.c:1608") $rmtp:struct
>>> timespec* $tu:struct timespec
>>> kernel.statement("sys_nanosleep@kernel/hrtimer.c:1611") $rmtp:struct
>>> timespec* $tu:struct timespec
>>> kernel.statement("sys_nanosleep@kernel/hrtimer.c:1612") $rmtp:struct
>>> timespec* $tu:struct timespec
>>
>> That looks good, as long as those listed probe points map to proper
>> addresses and give back proper context variables.
>>
>>
>> - FChE