linux-kernel - i386: Fix null interrupt handler (ignore

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Message-ID: <20070924220817.GA3447@Ahmed>
Date:	Tue, 25 Sep 2007 01:08:17 +0300
From:	"Ahmed S. Darwish" <darwish.07@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	hpa@...or.com
Subject: i386: Fix null interrupt handler (ignore_int) message ?

Hi all,

I'm getting little confused by some ignore_int (null interrupt handler) code in
head.S. Code notifies the user about the unknown raised interrupt by below
string:

int_msg:
	.asciz "Unknown interrupt or fault at EIP %p %p %p\n"

and prints it using below code path:

ignore_int:
	pushl %eax; pushl %ecx; pushl %edx; pushl %es; pushl %ds
	[...]
	pushl 16(%esp); pushl 24(%esp); 
	pushl 32(%esp); pushl 40(%esp); 
	pushl $int_msg
	[...]
	call printk

** But here's the state of stack before calling printk:

     ???            <-- 40(%esp)             
     ???            <-- 36(%esp)
     --> (Automatically pushed by the processor)
     %eflags        <-- 32(%esp)
     %cs	    <-- 28(%esp)
     %eip	    <-- 24(%esp)
     error-code     <-- 20(%esp)
     --> (Pushed by first lines of ignore_int)
     %eax	    <-- 16(%esp)
     %ecx	    <--	12(%esp)
     %edx	    <-- 8(%esp)
     %es	    <-- 4(%esp)
     %ds	    <-- %esp      

Does 40(%esp) hold a meaningfule value here ?. Also why passing 4 arguments after
the string to prinkt while the string only has 3 conversion specifications (i.e.,
3 * %p) ?.

Best regards,

-- 
Ahmed S. Darwish
HomePage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com
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