I guessed I asked too much. Can someone please tell me just this:
"How do I translate 48 bit address (segment descriptor:offset) to a
linear address which gdb can understand ?"
Thanks
- Rohit
On Sat, 5 May 2001, Rohit Rakshe wrote:
> Hi !
>
> I modified some TCP and UDP code in FreeBSD 4.1 and suddenly started
> getting (almost repeatable) kernel panics. This is how it looks like
> from remote gdb:
>
> (kgdb) bt
> #0 0xc0192e58 in panic (fmt=0xc035c076 "npxintr from nowhere") at
> ../../kern/kern_shutdown.c:550
> #1 0xc0303c6c in npx_intr (dummy=0x0) at ../../i386/isa/npx.c:721
> #2 0xc02e1052 in Xfpu ()
> #3 0xc019824d in softclock () at ../../kern/kern_timeout.c:131
> .
> .
> .
> (kgdb) list
> 126 } else {
> 127 c->c_flags =
> 128 (c->c_flags &
> ~CALLOUT_PENDING);
> 129 }
> 130 splx(s);
> 131 c_func(c_arg);
> 132 s = splhigh();
> 133 steps = 0;
> 134 c = nextsoftcheck;
> 135 }
> .
> .
> .
> (kgdb)
> #1 0xc0303c6c in npx_intr (dummy=0x0) at ../../i386/isa/npx.c:721
> 721 panic("npxintr from nowhere");
> (kgdb) p npxproc
> $5 = 0
> (kgdb) p npx_exists
> $6 = 1 '\001'
> .
> .
> .
> (kgdb) info all-registers
> eax 0x12 18
> ecx 0xc03a60a0 -1069916000
> edx 0x400000 4194304
> ebx 0xcbc56540 -876255936
> esp 0xc0361354 0xc0361354
> ebp 0xc0361410 0xc0361410
> esi 0x400000 4194304
> edi 0x400000 4194304
> eip 0xc019824d 0xc019824d
> eflags 0x346 838
> cs 0x8 8
> ss 0x10 16
> ds 0x400010 4194320
> es 0x10 16
> fs 0x0 0
> gs 0x0 0
> (kgdb) info float
> status 0xc8f5: exceptions: INVALID DIVZ UNDERF LOS FPSTACK; flags: 1000;
> top 1
> control 0x6620: compute to 53 bits; round DOWN; mask: LOS;
> warning: reserved bits on: 0x6000
>
> last instruction: opcode 0x2825; pc 0x71a4:0x2824c316; operand
> 0xf800:0x8176640
> regno tag msb lsb value
> %st(7) valid 0000000008179a802825 Denormal (0 as a double)
> %st(6) valid 71a42824c31600000000 Unnormal (NaN)
> %st(5) valid 08176640282571a42824 Unnormal (NaN)
> %st(4) valid c8910818f9380818f800 Unnormal (NaN)
> %st(3) valid 282571a42824c316bfbf Unnormal (NaN)
> %st(2) valid e82808176620089c3000 Unnormal (NaN)
> %st(1) valid 00000032000000010001 Denormal (0 as a double)
> %st(0) => valid 0000000000240818f800 Denormal (0 as a double)
>
>
> So, this means that there was a FPU exception in kernel, right ?
>
> 1. The code which I added in kernel does not use any floats. So I am
> wondering why this problem should happen at all.
>
> 2. pc register in FPU should give address of the instruction which caused
> this exception, right ?
>
> 3. If yes, how do I translate this 48 bit address in a linear address
> which gdb can understand ?
>
>
> Thanks for help !
>
>
> - Rohit
>
>
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