Re: BUG()

[Anupam Kapoor <anupam.kapoor@xxxxxxxxx>]

On Fri, 2 Jul 2004 11:44:25 +0200, Borislav Petkov
<borislav.petkov@xxxxxxxxxxx> wrote:
> 
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> Hi there guys,
> a new day - a new question :))
> 
> I've been trying to figure out today how BUG() works, it is inline assembly,
> again:
> 
> <from include/asm-i386/bug.h:12>
> 12 #if 1   /* Set to zero for a slightly smaller kernel */
> 13 #define BUG()                           \
> 14  __asm__ __volatile__(  "ud2\n"         \
> 15                         "\t.word %c0\n" \
> 16                         "\t.long %c1\n" \
> 17                          : : "i" (__LINE__), "i" (__FILE__))
> 
> I know that ud2 means undefined and generates invalid opcode exception, .word
> and .long are as directives, "i" as an input operand constraint is an
> immediate integer operand with constant value, but what I can't understand
> after looking into the as and gcc manuals is:
> 
> 1. what does the c mean in the constraint %c0, %c1 resp.?
i don't know. i will see if i can find something...
> 2. Where does the compiler get those __LINE__ and __FILE__ from?
they are gcc specific. i know of __FUNCTION__ which provides the
function name. i am sure there are others too...

kind regards
anupam

> 
> Thanks in advance for your patience,
> Boris.
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