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* [Bug libc/28153] New: [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld
@ 2021-07-28 21:10 i at maskray dot me
2021-07-29 16:50 ` [Bug libc/28153] " hjl.tools at gmail dot com
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: i at maskray dot me @ 2021-07-28 21:10 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28153
Bug ID: 28153
Summary: [test] gmon/tst-gmon-gprof* may have a f3 line when
built with ld.lld
Product: glibc
Version: unspecified
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: libc
Assignee: unassigned at sourceware dot org
Reporter: i at maskray dot me
CC: drepper.fsp at gmail dot com
Target Milestone: ---
Extracted from
https://sourceware.org/pipermail/libc-alpha/2021-July/129450.html
To build LLD 13.0.0:
# https://github.com/llvm/llvm-project/ origin/release/13.x
cmake -H. -Bout/release -G Ninja -DCMAKE_BUILD_TYPE=Release
-DLLVM_ENABLE_PROJECTS='clang;lld'
ninja -C out/release lld
I use
sudo ln -sf out/release/bin/lld /usr/local/bin/ld
to ensure the glibc build system definitely picks ld => lld
(messing around with LDFLAGS=-fuse-ld=lld may work as well)
For gmon/tst-gmon-gprof*, ld.lld linked tst-gmon-gprof has a f3 line, which is
considered a failure by the test. However, having the f3 line appears more
correct to me. I am unclear why ld.bfd tst-gmon-gpro doesn't have f3.
% cat gmon/tst-gmon-gprof.out
--- expected
+++ actual
@@ -1,2 +1,3 @@
f1 2000
f2 1000
+f3 1
FAIL
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* [Bug libc/28153] [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld
2021-07-28 21:10 [Bug libc/28153] New: [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld i at maskray dot me
@ 2021-07-29 16:50 ` hjl.tools at gmail dot com
2021-07-30 4:35 ` i at maskray dot me
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: hjl.tools at gmail dot com @ 2021-07-29 16:50 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28153
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |hjl.tools at gmail dot com
Status|UNCONFIRMED |WAITING
Ever confirmed|0 |1
Last reconfirmed| |2021-07-29
--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
On ld.bfd generated gmon/tst-gmon, gprof shows
ndex % time self children called name
0.00 0.00 1000/2000 f2 [2]
0.00 0.00 1000/2000 f3 [7]
[1] 0.0 0.00 0.00 2000 f1 [1]
-----------------------------------------------
0.00 0.00 1000/1000 f3 [7]
[2] 0.0 0.00 0.00 1000 f2 [2]
0.00 0.00 1000/2000 f1 [1]
-----------------------------------------------
...
Index by function name
[1] f1 [2] f2
Why do you think the output is incorrect?
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* [Bug libc/28153] [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld
2021-07-28 21:10 [Bug libc/28153] New: [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld i at maskray dot me
2021-07-29 16:50 ` [Bug libc/28153] " hjl.tools at gmail dot com
@ 2021-07-30 4:35 ` i at maskray dot me
2021-07-30 22:48 ` hjl.tools at gmail dot com
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: i at maskray dot me @ 2021-07-30 4:35 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28153
--- Comment #2 from Fangrui Song <i at maskray dot me> ---
lld linked gmon/tst-gmon has f3.
% cd ~/Dev/glibc/out/lld
% ./testrun.sh gmon/tst-gmon
% gprof gmon/tst-gmon
...
Call graph (explanation follows)
granularity: each sample hit covers 4 byte(s) no time propagated
index % time self children called name
0.00 0.00 1000/2000 f2 [2]
0.00 0.00 1000/2000 f3 [3]
[1] 0.0 0.00 0.00 2000 f1 [1]
-----------------------------------------------
0.00 0.00 1000/1000 f3 [3]
[2] 0.0 0.00 0.00 1000 f2 [2]
0.00 0.00 1000/2000 f1 [1]
-----------------------------------------------
0.00 0.00 1/1 main [9]
[3] 0.0 0.00 0.00 1 f3 [3]
0.00 0.00 1000/1000 f2 [2]
0.00 0.00 1000/2000 f1 [1]
-----------------------------------------------
...
Index by function name
[1] f1 [2] f2 [3] f3
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* [Bug libc/28153] [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld
2021-07-28 21:10 [Bug libc/28153] New: [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld i at maskray dot me
2021-07-29 16:50 ` [Bug libc/28153] " hjl.tools at gmail dot com
2021-07-30 4:35 ` i at maskray dot me
@ 2021-07-30 22:48 ` hjl.tools at gmail dot com
2021-07-31 4:23 ` hjl.tools at gmail dot com
2021-08-24 14:18 ` hjl.tools at gmail dot com
4 siblings, 0 replies; 6+ messages in thread
From: hjl.tools at gmail dot com @ 2021-07-30 22:48 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28153
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> ---
ld.bfd generates:
0000000000401000 T _init
0000000000401090 T main
00000000004010b0 T _start
00000000004010e0 T __gmon_start__
0000000000401130 t deregister_tm_clones
0000000000401160 t register_tm_clones
00000000004011a0 t __do_global_dtors_aux
00000000004011d0 t frame_dummy
0000000000401250 T atexit
0000000000401264 T _fini
0000000000401271 T etext
ld.lld generates:
0000000000201ba0 T _start
0000000000201bd0 T __gmon_start__
0000000000201c20 t deregister_tm_clones
0000000000201c50 t register_tm_clones
0000000000201c90 t __do_global_dtors_aux
0000000000201cc0 t frame_dummy
0000000000201d40 T main
0000000000201d60 t atexit
0000000000201d74 t _init
0000000000201d90 t _fini
0000000000201e10 T etext
glibc assumes that _start is the lowest address for which we need o keep
profiling records. The newer GCC places main in .text.startup section.
Since _start is in .text section, ld.bfd places main below _start. Put
_start in .text.startup section makes f3 to show up with ld.bfd.
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* [Bug libc/28153] [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld
2021-07-28 21:10 [Bug libc/28153] New: [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld i at maskray dot me
` (2 preceding siblings ...)
2021-07-30 22:48 ` hjl.tools at gmail dot com
@ 2021-07-31 4:23 ` hjl.tools at gmail dot com
2021-08-24 14:18 ` hjl.tools at gmail dot com
4 siblings, 0 replies; 6+ messages in thread
From: hjl.tools at gmail dot com @ 2021-07-31 4:23 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28153
--- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> ---
A patch is posted at
https://sourceware.org/pipermail/libc-alpha/2021-July/129685.html
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* [Bug libc/28153] [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld
2021-07-28 21:10 [Bug libc/28153] New: [test] gmon/tst-gmon-gprof* may have a f3 line when built with ld.lld i at maskray dot me
` (3 preceding siblings ...)
2021-07-31 4:23 ` hjl.tools at gmail dot com
@ 2021-08-24 14:18 ` hjl.tools at gmail dot com
4 siblings, 0 replies; 6+ messages in thread
From: hjl.tools at gmail dot com @ 2021-08-24 14:18 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=28153
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |2.35
Resolution|--- |FIXED
Status|NEW |RESOLVED
Version|unspecified |2.34
--- Comment #5 from H.J. Lu <hjl.tools at gmail dot com> ---
Fixed for glibc 2.35 by
commit 84a7eb1f87c1d01b58ad887a0ab5d87abbc1c772
Author: H.J. Lu <hjl.tools@gmail.com>
Date: Fri Jul 30 19:07:30 2021 -0700
Use __executable_start as the lowest address for profiling [BZ #28153]
Glibc assumes that ENTRY_POINT is the lowest address for which we need
to keep profiling records and BFD linker uses a linker script to place
the input sections.
Starting from GCC 4.6, the main function is placed in .text.startup
section and starting from binutils 2.22, BFD linker with
commit add44f8d5c5c05e08b11e033127a744d61c26aee
Author: Alan Modra <amodra@gmail.com>
Date: Thu Nov 25 03:03:02 2010 +0000
* scripttempl/elf.sc: Group .text.exit, text.startup and
.text.hot
sections.
places .text.startup section before .text section, which leave the main
function out of profiling records.
Starting from binutils 2.15, linker provides __executable_start to mark
the lowest address of the executable. Use __executable_start as the
lowest address to keep the main function in profiling records. This fixes
[BZ #28153].
Tested on Linux/x86-64, Linux/x32 and Linux/i686 as well as with
build-many-glibcs.py.
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