Date: Wed, 21 Oct 1998 15:36:51 +0200 (SAT) From: John Hay <jhay@mikom.csir.co.za> To: syssgm@dtir.qld.gov.au (Stephen McKay) Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: 3.0-R on a amd386dx/40 Message-ID: <199810211336.PAA07535@zibbi.mikom.csir.co.za> In-Reply-To: <199810211020.UAA09162@nymph.dtir.qld.gov.au> from Stephen McKay at "Oct 21, 98 08:20:59 pm"
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> >> Try "awk", for example. It uses floating point, and I think it will die.
> >> "df" uses double. "newfs" uses float. "ls" doesn't, and it works. It's
> >> a floating point problem, or I'll eat my copy of the Pointy Hat!
> >>
> >> I still think the "npx" lines from boot are relevant.
> >
> >ok, here are the lines:
> >npx0 on motherboard
> >npx0: 387 emulator
Ok, here is what I have found so far. I used a 3.0 system with a new
kernel with Peter Wemm's commits to i386/math_emulate.c. Then I
recompiled libc.a with vfprintf.c with debugging on and then also
compiled fsck with debugging on and got it to dump core on a 386
machine. Here is some of gdb's output. What is interesting is that
the coredump address (0x806859f) falls between two assembler
instructions... or did disassem get it wrong? Or am I confused?
Is it possible that the emulator in the kernel restarts the program
at the wrong place?
John
--
John Hay -- John.Hay@mikom.csir.co.za
-----------------
Core was generated by `fsck'.
Program terminated with signal 10, Bus error.
#0 0x806859f in cvt (value=5.2716105037754986, ndigits=1, flags=256,
sign=0xefbfd9fb "", decpt=0xefbfd9f4, ch=102, length=0xefbfd9f0)
at /usr/src/lib/libc/../libc/stdio/vfprintf.c:1219
1219 if (value < 0) {
(gdb) bt
#0 0x806859f in cvt (value=5.2716105037754986, ndigits=1, flags=256,
sign=0xefbfd9fb "", decpt=0xefbfd9f4, ch=102, length=0xefbfd9f0)
at /usr/src/lib/libc/../libc/stdio/vfprintf.c:1219
#1 0x8066a5e in vfprintf (fp=0x80765bc,
fmt0=0x80712c7 "(%d frags, %d blocks, %.1f%% fragmentation)\n",
ap=0xefbfdc00 "\t\024\a\b\e\021")
at /usr/src/lib/libc/../libc/stdio/vfprintf.c:608
#2 0x805e488 in printf ()
#3 0x804acef in checkfilesys (filesys=0x8076714 "/dev/rwd0s1e", mntpt=0x0,
auxdata=0, child=0) at main.c:271
#4 0x804a9e1 in main (argc=2, argv=0xefbfdde0) at main.c:136
#5 0x80480c9 in _start ()
(gdb) list
1214 */
1215 if (ch == 'e' || ch == 'E')
1216 ndigits++;
1217 mode = 2; /* ndigits significant digits */
1218 }
1219 if (value < 0) {
1220 value = -value;
1221 *sign = '-';
1222 } else
1223 *sign = '\000';
(gdb) disassem
Dump of assembler code for function cvt:
0x8068568 <cvt>: pushl %ebp
0x8068569 <cvt+1>: movl %esp,%ebp
0x806856b <cvt+3>: subl $0x8,%esp
0x806856e <cvt+6>: pushl %edi
0x806856f <cvt+7>: pushl %esi
0x8068570 <cvt+8>: pushl %ebx
0x8068571 <cvt+9>: movl 0x18(%ebp),%ecx
0x8068574 <cvt+12>: movl 0x20(%ebp),%esi
0x8068577 <cvt+15>: cmpl $0x66,%esi
0x806857a <cvt+18>: jne 0x8068584 <cvt+28>
0x806857c <cvt+20>: movl $0x3,%edx
0x8068581 <cvt+25>: jmp 0x8068596 <cvt+46>
0x8068583 <cvt+27>: nop
0x8068584 <cvt+28>: cmpl $0x65,%esi
0x8068587 <cvt+31>: je 0x806858e <cvt+38>
0x8068589 <cvt+33>: cmpl $0x45,%esi
0x806858c <cvt+36>: jne 0x8068591 <cvt+41>
0x806858e <cvt+38>: incl 0x10(%ebp)
0x8068591 <cvt+41>: movl $0x2,%edx
0x8068596 <cvt+46>: fldz
0x8068598 <cvt+48>: fcompl 0x8(%ebp)
0x806859b <cvt+51>: fnstsw
0x806859e <cvt+54>: andb $0x45,%ah
0x80685a1 <cvt+57>: jne 0x80685b0 <cvt+72>
0x80685a3 <cvt+59>: fldl 0x8(%ebp)
0x80685a6 <cvt+62>: fchs
0x80685a8 <cvt+64>: fstpl 0x8(%ebp)
0x80685ab <cvt+67>: movb $0x2d,(%ecx)
0x80685ae <cvt+70>: jmp 0x80685b3 <cvt+75>
0x80685b0 <cvt+72>: movb $0x0,(%ecx)
0x80685b3 <cvt+75>: leal 0xfffffff8(%ebp),%eax
0x80685b6 <cvt+78>: pushl %eax
0x80685b7 <cvt+79>: leal 0xfffffffc(%ebp),%eax
0x80685ba <cvt+82>: pushl %eax
0x80685bb <cvt+83>: pushl 0x1c(%ebp)
0x80685be <cvt+86>: pushl 0x10(%ebp)
...
-----------------
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