[uCsimm] RE: [UCLINUX] uclinux paging

From: Vadim Lebedev (vlebedev@aplio.fr)
Date: Mon Apr 10 2000 - 11:57:38 EDT


Fabien,

I think PAGE_OFFSET should be 0

Vadim

-----Original Message-----
From: owner-uclinux@c3po.kc-inc.net
[mailto:owner-uclinux@c3po.kc-inc.net]On Behalf Of
fabien.klein@conexant.com
Sent: lundi 10 avril 2000 12:34
To: gnucsimm@www.reefhq.org.au
Cc: ucsimm@uClinux.org; uclinux@c3po.kc-inc.net
Subject: [UCLINUX] uclinux paging

Hi

I need some information about page handling in uclinux especially
for file mapping

If a mount an ext2 partition on the ramdisk device (after expanding an ext2
sb,
or doing an mke2fs) , I see that I can copy file to this new partition, see
a correct
directory but each time I try to read a copied file into this fs I get
garbage char

Ex:
expand /etc/ramfs512.img /dev/ram0
mount -t ext2 /dev/ram0 /var
cp /etc/blablabla /var

hexdump /etc/blablabla

0: 73 65 72 76 69 63 65 73-00 72 72 6F 72 2E 74 78 services.rror.tx
10: 74 00 74 78 74 00 EF FE-F0 1E EF FE F0 1E EF FE t.txt...........
20: F0 1E EF FE F0 1E EF FE-F0 1E EF FE F0 1E EF FE ..

(these F0 1E EF FE correspond to
#define STACK_UNTOUCHED_MAGIC 0xfeef1ef0)
==>the read pointer is broken

If we look closer

when I do
cp /etc/blablabla /var
ext2write do this : memcpy_fromfs ( 0x00fd0000, 0x00xxxx, size)

and hexdump /etc/blablabla
generic_file_read do this memcpy_tofs ( 0xyyyyyyyy, 0x00fdf000,size)

the size is correct but the the src address (= page_address(page) + offset)
is wrong

The same problem happens for nfs read but it's OK for romfs or proc file
read

I think that the page used by
page_address(page) is not the good one or parameters have bee overwritten

Can someone tell me how to debug this?
The kernel begins at 0xa00000, and the RAM ends at 0x1000000
(PAGE_OFFSET==kernel .text?????)

Thanks

Fabien

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