diff options
| -rw-r--r-- | NEWS | 1 | ||||
| -rw-r--r-- | elf/dl-tunables.list | 13 | ||||
| -rw-r--r-- | gmon/Makefile | 22 | ||||
| -rw-r--r-- | gmon/gmon.c | 29 | ||||
| -rw-r--r-- | gmon/mcount.c | 5 | ||||
| -rw-r--r-- | gmon/sys/gmon.h | 6 | ||||
| -rw-r--r-- | gmon/tst-mcount-overflow-check.sh | 45 | ||||
| -rw-r--r-- | gmon/tst-mcount-overflow.c | 72 | ||||
| -rw-r--r-- | manual/tunables.texi | 59 |
9 files changed, 245 insertions, 7 deletions
@@ -25,6 +25,7 @@ The following bugs are resolved with this release: [12154] Do not fail DNS resolution for CNAMEs which are not host names [24816] Fix tst-nss-files-hosts-long on single-stack hosts + [27576] gmon: improve mcount overflow handling [28846] CMSG_NXTHDR may trigger -Wstrict-overflow warning [29444] gmon: Fix allocated buffer overflow (bug 29444) [29864] libc: __libc_start_main() should obtain program headers diff --git a/elf/dl-tunables.list b/elf/dl-tunables.list index e6a56b3070..9fa3b484cf 100644 --- a/elf/dl-tunables.list +++ b/elf/dl-tunables.list @@ -169,4 +169,17 @@ glibc { default: 2 } } + + gmon { + minarcs { + type: INT_32 + minval: 50 + default: 50 + } + maxarcs { + type: INT_32 + minval: 50 + default: 1048576 + } + } } diff --git a/gmon/Makefile b/gmon/Makefile index 552b7d7751..58ea34aa7e 100644 --- a/gmon/Makefile +++ b/gmon/Makefile @@ -25,7 +25,7 @@ include ../Makeconfig headers := sys/gmon.h sys/gmon_out.h sys/profil.h routines := gmon mcount profil sprofil prof-freq -tests = tst-sprofil tst-gmon +tests = tst-sprofil tst-gmon tst-mcount-overflow ifeq ($(build-profile),yes) tests += tst-profile-static tests-static += tst-profile-static @@ -56,6 +56,18 @@ ifeq ($(run-built-tests),yes) tests-special += $(objpfx)tst-gmon-gprof.out endif +CFLAGS-tst-mcount-overflow.c := -fno-omit-frame-pointer -pg +tst-mcount-overflow-no-pie = yes +CRT-tst-mcount-overflow := $(csu-objpfx)g$(start-installed-name) +# Intentionally use invalid config where maxarcs<minarcs to check warning is printed +tst-mcount-overflow-ENV := GMON_OUT_PREFIX=$(objpfx)tst-mcount-overflow.data \ + GLIBC_TUNABLES=glibc.gmon.minarcs=51:glibc.gmon.maxarcs=50 +# Send stderr into output file because we make sure expected messages are printed +tst-mcount-overflow-ARGS := 2>&1 1>/dev/null | cat +ifeq ($(run-built-tests),yes) +tests-special += $(objpfx)tst-mcount-overflow-check.out +endif + CFLAGS-tst-gmon-static.c := $(PIE-ccflag) -fno-omit-frame-pointer -pg CRT-tst-gmon-static := $(csu-objpfx)g$(static-start-installed-name) tst-gmon-static-no-pie = yes @@ -103,6 +115,14 @@ $(objpfx)tst-gmon.out: clean-tst-gmon-data clean-tst-gmon-data: rm -f $(objpfx)tst-gmon.data.* +$(objpfx)tst-mcount-overflow.o: clean-tst-mcount-overflow-data +clean-tst-mcount-overflow-data: + rm -f $(objpfx)tst-mcount-overflow.data.* + +$(objpfx)tst-mcount-overflow-check.out: tst-mcount-overflow-check.sh $(objpfx)tst-mcount-overflow.out + $(SHELL) $< $(objpfx)tst-mcount-overflow > $@; \ + $(evaluate-test) + $(objpfx)tst-gmon-gprof.out: tst-gmon-gprof.sh $(objpfx)tst-gmon.out $(SHELL) $< $(GPROF) $(objpfx)tst-gmon $(objpfx)tst-gmon.data.* > $@; \ $(evaluate-test) diff --git a/gmon/gmon.c b/gmon/gmon.c index bf76358d5b..689bf80141 100644 --- a/gmon/gmon.c +++ b/gmon/gmon.c @@ -46,6 +46,11 @@ #include <libc-internal.h> #include <not-cancel.h> +#if HAVE_TUNABLES +# define TUNABLE_NAMESPACE gmon +# include <elf/dl-tunables.h> +#endif + #ifdef PIC # include <link.h> @@ -124,6 +129,22 @@ __monstartup (u_long lowpc, u_long highpc) int o; char *cp; struct gmonparam *p = &_gmonparam; + long int minarcs, maxarcs; + +#if HAVE_TUNABLES + /* Read minarcs/maxarcs tunables. */ + minarcs = TUNABLE_GET (minarcs, int32_t, NULL); + maxarcs = TUNABLE_GET (maxarcs, int32_t, NULL); + if (maxarcs < minarcs) + { + ERR("monstartup: maxarcs < minarcs, setting maxarcs = minarcs\n"); + maxarcs = minarcs; + } +#else + /* No tunables, we use hardcoded defaults */ + minarcs = MINARCS; + maxarcs = MAXARCS; +#endif /* * round lowpc and highpc to multiples of the density we're using @@ -146,10 +167,10 @@ __monstartup (u_long lowpc, u_long highpc) } p->fromssize = ROUNDUP(p->textsize / HASHFRACTION, sizeof(*p->froms)); p->tolimit = p->textsize * ARCDENSITY / 100; - if (p->tolimit < MINARCS) - p->tolimit = MINARCS; - else if (p->tolimit > MAXARCS) - p->tolimit = MAXARCS; + if (p->tolimit < minarcs) + p->tolimit = minarcs; + else if (p->tolimit > maxarcs) + p->tolimit = maxarcs; p->tossize = p->tolimit * sizeof(struct tostruct); cp = calloc (p->kcountsize + p->fromssize + p->tossize, 1); diff --git a/gmon/mcount.c b/gmon/mcount.c index 9d4a1a50fa..f7180fdb83 100644 --- a/gmon/mcount.c +++ b/gmon/mcount.c @@ -41,6 +41,10 @@ static char sccsid[] = "@(#)mcount.c 8.1 (Berkeley) 6/4/93"; #include <atomic.h> +#include <not-cancel.h> +#include <unistd.h> +#define ERR(s) __write_nocancel (STDERR_FILENO, s, sizeof (s) - 1) + /* * mcount is called on entry to each function compiled with the profiling * switch set. _mcount(), which is declared in a machine-dependent way @@ -170,6 +174,7 @@ done: return; overflow: p->state = GMON_PROF_ERROR; + ERR("mcount: call graph buffer size limit exceeded, gmon.out will not be generated\n"); return; } diff --git a/gmon/sys/gmon.h b/gmon/sys/gmon.h index b4cc3b043a..af0582a371 100644 --- a/gmon/sys/gmon.h +++ b/gmon/sys/gmon.h @@ -111,6 +111,8 @@ extern struct __bb *__bb_head; * Always allocate at least this many tostructs. This * hides the inadequacy of the ARCDENSITY heuristic, at least * for small programs. + * + * Value can be overridden at runtime by glibc.gmon.minarcs tunable. */ #define MINARCS 50 @@ -124,8 +126,8 @@ extern struct __bb *__bb_head; * Used to be max representable value of ARCINDEX minus 2, but now * that ARCINDEX is a long, that's too large; we don't really want * to allow a 48 gigabyte table. - * The old value of 1<<16 wasn't high enough in practice for large C++ - * programs; will 1<<20 be adequate for long? FIXME + * + * Value can be overridden at runtime by glibc.gmon.maxarcs tunable. */ #define MAXARCS (1 << 20) diff --git a/gmon/tst-mcount-overflow-check.sh b/gmon/tst-mcount-overflow-check.sh new file mode 100644 index 0000000000..27eb5538fd --- /dev/null +++ b/gmon/tst-mcount-overflow-check.sh @@ -0,0 +1,45 @@ +#!/bin/sh +# Test expected messages generated when mcount overflows +# Copyright (C) 2017-2023 Free Software Foundation, Inc. +# Copyright The GNU Toolchain Authors. +# This file is part of the GNU C Library. + +# The GNU C Library is free software; you can redistribute it and/or +# modify it under the terms of the GNU Lesser General Public +# License as published by the Free Software Foundation; either +# version 2.1 of the License, or (at your option) any later version. + +# The GNU C Library is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +# Lesser General Public License for more details. + +# You should have received a copy of the GNU Lesser General Public +# License along with the GNU C Library; if not, see +# <https://www.gnu.org/licenses/>. + +LC_ALL=C +export LC_ALL +set -e +exec 2>&1 + +program="$1" + +check_msg() { + if ! grep -q "$1" "$program.out"; then + echo "FAIL: expected message not in output: $1" + exit 1 + fi +} + +check_msg 'monstartup: maxarcs < minarcs, setting maxarcs = minarcs' +check_msg 'mcount: call graph buffer size limit exceeded, gmon.out will not be generated' + +for data_file in $1.data.*; do + if [ -f "$data_file" ]; then + echo "FAIL: expected no data files, but found $data_file" + exit 1 + fi +done + +echo PASS diff --git a/gmon/tst-mcount-overflow.c b/gmon/tst-mcount-overflow.c new file mode 100644 index 0000000000..06cc93ef87 --- /dev/null +++ b/gmon/tst-mcount-overflow.c @@ -0,0 +1,72 @@ +/* Test program to trigger mcount overflow in profiling collection. + Copyright (C) 2017-2023 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +/* Program with sufficiently complex, yet pointless, call graph + that it will trigger an mcount overflow, when you set the + minarcs/maxarcs tunables to very low values. */ + +#define PREVENT_TAIL_CALL asm volatile ("") + +/* Calls REP(n) macro 16 times, for n=0..15. + * You need to define REP(n) before using this. + */ +#define REPS \ + REP(0) REP(1) REP(2) REP(3) REP(4) REP(5) REP(6) REP(7) \ + REP(8) REP(9) REP(10) REP(11) REP(12) REP(13) REP(14) REP(15) + +/* Defines 16 leaf functions named f1_0 to f1_15 */ +#define REP(n) \ + __attribute__ ((noinline, noclone, weak)) void f1_##n (void) {}; +REPS +#undef REP + +/* Calls all 16 leaf functions f1_* in succession */ +__attribute__ ((noinline, noclone, weak)) void +f2 (void) +{ +# define REP(n) f1_##n(); + REPS +# undef REP + PREVENT_TAIL_CALL; +} + +/* Defines 16 functions named f2_0 to f2_15, which all just call f2 */ +#define REP(n) \ + __attribute__ ((noinline, noclone, weak)) void \ + f2_##n (void) { f2(); PREVENT_TAIL_CALL; }; +REPS +#undef REP + +__attribute__ ((noinline, noclone, weak)) void +f3 (int count) +{ + for (int i = 0; i < count; ++i) + { + /* Calls f1_0(), f2_0(), f1_1(), f2_1(), f3_0(), etc */ +# define REP(n) f1_##n(); f2_##n(); + REPS +# undef REP + } +} + +int +main (void) +{ + f3 (1000); + return 0; +} diff --git a/manual/tunables.texi b/manual/tunables.texi index 83cdcdac6d..8bb2f29ea5 100644 --- a/manual/tunables.texi +++ b/manual/tunables.texi @@ -77,6 +77,9 @@ glibc.malloc.check: 0 (min: 0, max: 3) capabilities seen by @theglibc{} * Memory Related Tunables:: Tunables that control the use of memory by @theglibc{}. +* gmon Tunables:: Tunables that control the gmon profiler, used in + conjunction with gprof + @end menu @node Tunable names @@ -612,3 +615,59 @@ support in the kernel if this tunable has any non-zero value. The default value is @samp{0}, which disables all memory tagging. @end deftp + +@node gmon Tunables +@section gmon Tunables +@cindex gmon tunables + +@deftp {Tunable namespace} glibc.gmon +This tunable namespace affects the behaviour of the gmon profiler. +gmon is a component of @theglibc{} which is normally used in +conjunction with gprof. + +When GCC compiles a program with the @code{-pg} option, it instruments +the program with calls to the @code{mcount} function, to record the +program's call graph. At program startup, a memory buffer is allocated +to store this call graph; the size of the buffer is calculated using a +heuristic based on code size. If during execution, the buffer is found +to be too small, profiling will be aborted and no @file{gmon.out} file +will be produced. In that case, you will see the following message +printed to standard error: + +@example +mcount: call graph buffer size limit exceeded, gmon.out will not be generated +@end example + +Most of the symbols discussed in this section are defined in the header +@code{sys/gmon.h}. However, some symbols (for example @code{mcount}) +are not defined in any header file, since they are only intended to be +called from code generated by the compiler. +@end deftp + +@deftp Tunable glibc.mem.minarcs +The heuristic for sizing the call graph buffer is known to be +insufficient for small programs; hence, the calculated value is clamped +to be at least a minimum size. The default minimum (in units of +call graph entries, @code{struct tostruct}), is given by the macro +@code{MINARCS}. If you have some program with an unusually complex +call graph, for which the heuristic fails to allocate enough space, +you can use this tunable to increase the minimum to a larger value. +@end deftp + +@deftp Tunable glibc.mem.maxarcs +To prevent excessive memory consumption when profiling very large +programs, the call graph buffer is allowed to have a maximum of +@code{MAXARCS} entries. For some very large programs, the default +value of @code{MAXARCS} defined in @file{sys/gmon.h} is too small; in +that case, you can use this tunable to increase it. + +Note the value of the @code{maxarcs} tunable must be greater or equal +to that of the @code{minarcs} tunable; if this constraint is violated, +a warning will printed to standard error at program startup, and +the @code{minarcs} value will be used as the maximum as well. + +Setting either tunable too high may result in a call graph buffer +whose size exceeds the available memory; in that case, an out of memory +error will be printed at program startup, the profiler will be +disabled, and no @file{gmon.out} file will be generated. +@end deftp |