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From 84a7eb1f87c1d01b58ad887a0ab5d87abbc1c772 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Fri, 30 Jul 2021 19:07:30 -0700
Subject: [PATCH] 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.
---
csu/gmon-start.c | 10 +++++++++-
gmon/tst-gmon-gprof.sh | 2 ++
gmon/tst-gmon-static-gprof.sh | 2 ++
3 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/csu/gmon-start.c b/csu/gmon-start.c
index b343288..344606a 100644
--- a/csu/gmon-start.c
+++ b/csu/gmon-start.c
@@ -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. */
diff --git a/gmon/tst-gmon-gprof.sh b/gmon/tst-gmon-gprof.sh
index 9d37158..dc0be02 100644
--- a/gmon/tst-gmon-gprof.sh
+++ b/gmon/tst-gmon-gprof.sh
@@ -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" "$data" \
diff --git a/gmon/tst-gmon-static-gprof.sh b/gmon/tst-gmon-static-gprof.sh
index 79218df..4cc99c8 100644
--- a/gmon/tst-gmon-static-gprof.sh
+++ b/gmon/tst-gmon-static-gprof.sh
@@ -39,6 +39,7 @@ trap cleanup 0
cat > "$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
--
1.8.3.1
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