Date: Sun, 13 Jul 2008 20:55:48 +1000 From: Peter Jeremy <peterjeremy@optushome.com.au> To: Dmitry Morozovsky <marck@rinet.ru> Cc: freebsd-hackers@freebsd.org, oleg@rinet.ru Subject: Re: profiling broken on RELENG_7/i386 Message-ID: <20080713105548.GA55221@server.vk2pj.dyndns.org> In-Reply-To: <20080704121833.J35668@woozle.rinet.ru> References: <20080704121833.J35668@woozle.rinet.ru>
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On 2008-Jul-04 13:01:11 +0400, Dmitry Morozovsky <marck@rinet.ru> wrote:
>It seems we step on a bug in gcc in RELENG_7/i386
>
>It is triggered at least by profiling program which uses getopt(3):
I think it's actually in the profiling initialisation code. If
you try to run sample code under gdb, you can see that .mcount()
is not preserving %ecx, though main() assumes it does.
(gdb) disas $eip
Dump of assembler code for function main:
0x080481d0 <main+0>: lea 0x4(%esp),%ecx
0x080481d4 <main+4>: and $0xfffffff0,%esp
0x080481d7 <main+7>: pushl 0xfffffffc(%ecx)
0x080481da <main+10>: push %ebp
0x080481db <main+11>: mov %esp,%ebp
0x080481dd <main+13>: push %ecx
0x080481de <main+14>: sub $0x14,%esp
0x080481e1 <main+17>: call 0x8051b50 <.mcount>
0x080481e6 <main+22>: mov 0x4(%ecx),%eax
0x080481e9 <main+25>: mov (%eax),%eax
0x080481eb <main+27>: mov %eax,0x8(%esp)
0x080481ef <main+31>: mov (%ecx),%eax
0x080481f1 <main+33>: mov %eax,0x4(%esp)
0x080481f5 <main+37>: movl $0x8066b0a,(%esp)
0x080481fc <main+44>: call 0x8051b00 <printf>
0x08048201 <main+49>: mov $0x0,%eax
0x08048206 <main+54>: add $0x14,%esp
0x08048209 <main+57>: pop %ecx
0x0804820a <main+58>: pop %ebp
0x0804820b <main+59>: lea 0xfffffffc(%ecx),%esp
0x0804820e <main+62>: ret =20
End of assembler dump.
(gdb) x/10x $esp
0xbfbfeadc: 0x0804815f 0x00000001 0xbfbfeb08 0xbfbfeb10
0xbfbfeaec: 0x00000000 0x00000000 0x00000000 0x00000000
0xbfbfeafc: 0x00000000 0x00000000
(gdb) info regi
eax 0xbfbfeb08 -1077941496
ecx 0x1e968 125288
edx 0x8051d1a 134552858
ebx 0x1 1
esp 0xbfbfeadc 0xbfbfeadc
ebp 0xbfbfeb00 0xbfbfeb00
esi 0xbfbfeb10 -1077941488
edi 0x0 0
eip 0x80481d0 0x80481d0
eflags 0x282 642
cs 0x33 51
ss 0x3b 59
ds 0x3b 59
es 0x3b 59
fs 0x3b 59
gs 0x1b 27
=2E..
[step through .mcount]
=2E..
(gdb) stepi
main (argc=3DError accessing memory address 0x1b: Bad address.
) at x.c:4
4 printf("Hello %d %s\n", argc, argv[0]);
(gdb) info regi
eax 0x1 1
ecx 0x1b 27
edx 0x804815f 134512991
ebx 0x1 1
esp 0xbfbfeab0 0xbfbfeab0
ebp 0xbfbfeac8 0xbfbfeac8
esi 0xbfbfeb10 -1077941488
edi 0x0 0
eip 0x80481e6 0x80481e6
eflags 0x246 582
cs 0x33 51
ss 0x3b 59
ds 0x3b 59
es 0x3b 59
fs 0x3b 59
gs 0x1b 27
--=20
Peter Jeremy
Please excuse any delays as the result of my ISP's inability to implement
an MTA that is either RFC2821-compliant or matches their claimed behaviour.
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