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Use __executable_start as the lowest address for profiling [BZ #28153]

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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.
This commit is contained in:
H.J. Lu 2021-07-30 19:07:30 -07:00
parent 5eb3e2c794
commit 84a7eb1f87
3 changed files with 13 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

10
csu/gmon-start.c
View file

@ -52,6 +52,11 @@ extern char ENTRY_POINT[];
#endif
extern char etext[];
/* Use __executable_start as the lowest address to keep profiling records
if it provided by the linker. */
extern const char executable_start[] asm ("__executable_start")
__attribute__ ((weak, visibility ("hidden")));
#ifndef TEXT_START
# ifdef ENTRY_POINT_DECL
# define TEXT_START ENTRY_POINT
@ -92,7 +97,10 @@ __gmon_start__ (void)
called = 1;
/* Start keeping profiling records. */
__monstartup ((u_long) TEXT_START, (u_long) &etext);
if (&executable_start != NULL)
__monstartup ((u_long) &executable_start, (u_long) &etext);
else
__monstartup ((u_long) TEXT_START, (u_long) &etext);
/* Call _mcleanup before exiting; it will write out gmon.out from the
collected data. */

2
gmon/tst-gmon-gprof.sh
View file

@ -39,12 +39,14 @@ trap cleanup 0
cat > "$expected" <<EOF
f1 2000
f2 1000
f3 1
EOF
# Special version for powerpc with function descriptors.
cat > "$expected_dot" <<EOF
.f1 2000
.f2 1000
.f3 1
EOF
"$GPROF" -C "$program" "$data" \

2
gmon/tst-gmon-static-gprof.sh
View file

@ -39,6 +39,7 @@ trap cleanup 0
cat > "$expected" <<EOF
f1 2000
f2 1000
f3 1
main 1
EOF
@ -46,6 +47,7 @@ EOF
cat > "$expected_dot" <<EOF
.f1 2000
.f2 1000
.f3 1
.main 1
EOF