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64-bit sysinfo

To: linux-mips@linux-mips.org
Subject: 64-bit sysinfo
From: Trevor Woerner <mips081@vtnet.ca>
Date: Thu, 12 Jun 2003 06:59:26 -0400
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Hi everyone,

(good to see some familiar and friendly faces from the PPC list! :-)

I ran into a problem yesterday and I just don't know how I'm going to 
approach solving it.

I compiled a 64-bit MIPS kernel, then built a busybox-based ramdisk. At 
first I couldn't get busybox's 'init' to work but later solved it by 
disabling the 'check_memory()' call.

Further investigation into why the 'check_memory()' call was failing 
revealed a problem with the 'sysinfo()' system call. The kernel is 
64-bit, therefore when it fills in the 'struct sysinfo' (as it does 
when 'sys_meminfo()' is called) unsigned int's are 64 bits. But back in 
userspace, the 'struct sysinfo' that gets allocated thinks that 
unsigned int's are 32 bits.

This causes a crash if the 'struct sysinfo' is allocated on the stack 
back in userspace, and causes seg faults if it's allocated in the .data 
section (globally).

I'm crossing my fingers and hoping that my solution is to build all 
user-space apps with some switch that will set the sizes of data types 
to be the same between user space and kernel space. Does some such 
option exist?

        Trevor

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