Date: Sun, 13 Jul 2008 18:01:12 +0400 (MSD) From: Dmitry Morozovsky <marck@rinet.ru> To: Peter Jeremy <peterjeremy@optushome.com.au> Cc: kan@freebsd.org, freebsd-hackers@freebsd.org, oleg@rinet.ru Subject: Re: profiling broken on RELENG_7/i386 Message-ID: <20080713175927.R58331@woozle.rinet.ru> In-Reply-To: <20080713105548.GA55221@server.vk2pj.dyndns.org> References: <20080704121833.J35668@woozle.rinet.ru> <20080713105548.GA55221@server.vk2pj.dyndns.org>
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On Sun, 13 Jul 2008, Peter Jeremy wrote:
PJ> On 2008-Jul-04 13:01:11 +0400, Dmitry Morozovsky <marck@rinet.ru> wrote:
PJ> >It seems we step on a bug in gcc in RELENG_7/i386
PJ> >
PJ> >It is triggered at least by profiling program which uses getopt(3):
PJ>
PJ> I think it's actually in the profiling initialisation code. If
PJ> you try to run sample code under gdb, you can see that .mcount()
PJ> is not preserving %ecx, though main() assumes it does.
I see. However, I'm afraid we need knowledge of some gcc guru to bring the fix
in.
Alexander, could you please comment?
PJ>
PJ> (gdb) disas $eip
PJ> Dump of assembler code for function main:
PJ> 0x080481d0 <main+0>: lea 0x4(%esp),%ecx
PJ> 0x080481d4 <main+4>: and $0xfffffff0,%esp
PJ> 0x080481d7 <main+7>: pushl 0xfffffffc(%ecx)
PJ> 0x080481da <main+10>: push %ebp
PJ> 0x080481db <main+11>: mov %esp,%ebp
PJ> 0x080481dd <main+13>: push %ecx
PJ> 0x080481de <main+14>: sub $0x14,%esp
PJ> 0x080481e1 <main+17>: call 0x8051b50 <.mcount>
PJ> 0x080481e6 <main+22>: mov 0x4(%ecx),%eax
PJ> 0x080481e9 <main+25>: mov (%eax),%eax
PJ> 0x080481eb <main+27>: mov %eax,0x8(%esp)
PJ> 0x080481ef <main+31>: mov (%ecx),%eax
PJ> 0x080481f1 <main+33>: mov %eax,0x4(%esp)
PJ> 0x080481f5 <main+37>: movl $0x8066b0a,(%esp)
PJ> 0x080481fc <main+44>: call 0x8051b00 <printf>
PJ> 0x08048201 <main+49>: mov $0x0,%eax
PJ> 0x08048206 <main+54>: add $0x14,%esp
PJ> 0x08048209 <main+57>: pop %ecx
PJ> 0x0804820a <main+58>: pop %ebp
PJ> 0x0804820b <main+59>: lea 0xfffffffc(%ecx),%esp
PJ> 0x0804820e <main+62>: ret
PJ> End of assembler dump.
PJ> (gdb) x/10x $esp
PJ> 0xbfbfeadc: 0x0804815f 0x00000001 0xbfbfeb08 0xbfbfeb10
PJ> 0xbfbfeaec: 0x00000000 0x00000000 0x00000000 0x00000000
PJ> 0xbfbfeafc: 0x00000000 0x00000000
PJ> (gdb) info regi
PJ> eax 0xbfbfeb08 -1077941496
PJ> ecx 0x1e968 125288
PJ> edx 0x8051d1a 134552858
PJ> ebx 0x1 1
PJ> esp 0xbfbfeadc 0xbfbfeadc
PJ> ebp 0xbfbfeb00 0xbfbfeb00
PJ> esi 0xbfbfeb10 -1077941488
PJ> edi 0x0 0
PJ> eip 0x80481d0 0x80481d0
PJ> eflags 0x282 642
PJ> cs 0x33 51
PJ> ss 0x3b 59
PJ> ds 0x3b 59
PJ> es 0x3b 59
PJ> fs 0x3b 59
PJ> gs 0x1b 27
PJ> ...
PJ> [step through .mcount]
PJ> ...
PJ> (gdb) stepi
PJ> main (argc=Error accessing memory address 0x1b: Bad address.
PJ> ) at x.c:4
PJ> 4 printf("Hello %d %s\n", argc, argv[0]);
PJ> (gdb) info regi
PJ> eax 0x1 1
PJ> ecx 0x1b 27
PJ> edx 0x804815f 134512991
PJ> ebx 0x1 1
PJ> esp 0xbfbfeab0 0xbfbfeab0
PJ> ebp 0xbfbfeac8 0xbfbfeac8
PJ> esi 0xbfbfeb10 -1077941488
PJ> edi 0x0 0
PJ> eip 0x80481e6 0x80481e6
PJ> eflags 0x246 582
PJ> cs 0x33 51
PJ> ss 0x3b 59
PJ> ds 0x3b 59
PJ> es 0x3b 59
PJ> fs 0x3b 59
PJ> gs 0x1b 27
PJ>
PJ> --
PJ> Peter Jeremy
PJ> Please excuse any delays as the result of my ISP's inability to implement
PJ> an MTA that is either RFC2821-compliant or matches their claimed behaviour.
PJ>
Sincerely,
D.Marck [DM5020, MCK-RIPE, DM3-RIPN]
[ FreeBSD committer: marck@FreeBSD.org ]
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*** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck@rinet.ru ***
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