Re: [Q] x86 - boot/header.S

Cyrill Gorcunov
2008-02-23T09:22:29Z

[Sam Ravnborg - Sat, Feb 23, 2008 at 10:18:17AM +0100]
| On Sat, Feb 23, 2008 at 12:07:39PM +0300, Cyrill Gorcunov wrote:
| > [Yinghai Lu - Sat, Feb 23, 2008 at 12:44:49AM -0800]
| > | On Sat, Feb 23, 2008 at 12:20 AM, Cyrill Gorcunov <gorcunov@gmail.com> wrote:
| > | > Hi Peter, Sam,
| > | >
| > | > could you take a look on x86/boot/header.S:280 please?
| > | >
| > | > # Zero the bss
| > | > movw $__bss_start, %di
| > | > movw $_end+3, %cx
| > | > xorl %eax, %eax
| > | > subw %di, %cx
| > | > shrw $2, %cx
| > | > rep; stosl
| > | >
| > | > I wonder why is $_end there instead of $__bss_stop?
| > | > Well, accroding to vmlinux_32.lsd both _end and __bss_stop
| > | > are the same BUT __bss_stop is more convenient methink.
| > | > Would it be usefull to change?
| > |
| > | we should have head32.c like head64.c
| > | and x86_32_start_kernel.
| > |
| > | Eric's patch long time ago...
| > |
| > | YH
| > |
| >
| > Hi Yinghai,
| >
| > thanks for reply BUT that is not the point (or maybe I miss something).
| >
| > Look, we only have head64.c - there is no head32.c at all. Both
| > vmlinux_32/64.lds defines _end exactly the same as __bss_stop. So in
| > code which DO fillup bss section with zeros the prefered name is
| > __bss_stop. The only thing I'm trying to say that it would be clean
| > naming scheme and I think it would help for further review - instead
| > of searching all over x86 files to find _end definition __bss_stop
| > tell us WHAT we are zeroing from the code.
|
| We should introduce head32.c and then we can use the exact same function
| as 64 bit does:
|
| /* Don't add a printk in there. printk relies on the PDA which is not initialized
| yet. */
| static void __init clear_bss(void)
| {
| memset(__bss_start, 0,
| (unsigned long) __bss_stop - (unsigned long) __bss_start);
| }
|
| This answers your Q.
|
| I already resubmitted Eric's original patch to introduce head32.c as I also
| liked the cleanup in two Makefiles.
|
| Sam
|

thanks Sam, i just saw your patch.

- Cyrill -