[uml-devel] [PATCH] uml: problem with 2G/2G host address space

[Joris van Rantwijk <jvrantwijk@xs4all.nl>]

Hello,

I believe the current version (2.6.16.2) of UML does not work properly
on a i386 host with non-3G/1G address space split. The included patch
attempts to fix this.

On a i386 2.6.16.2 host configured with "3G/1G user/kernel split for
full 1G low memory" (VMSPLIT_3G_OPT), I found that UML would crash
on boot with the following error message:
  mapping mmap stub failed, errno = 12

It soon made sense to me that a 3G/1G configured UML would crash like
this, but I then found that UML 2.6.16.2 configured for 2G/2G crashed
in exactly the same way. I think this is due to the fact that STUB_CODE
and STUB_DATA are fixed at the 3G/1G settings. After changing these
settings, everything seems to work properly in 2G/2G mode.

Bye,
  Joris.

diff -urN -U 5 linux-2.6.16.2/arch/um/Kconfig.i386 linux-2.6.16.2-joris/arch/um/Kconfig.i386
--- linux-2.6.16.2/arch/um/Kconfig.i386	2006-04-07 18:56:47.000000000 +0200
+++ linux-2.6.16.2-joris/arch/um/Kconfig.i386	2006-04-09 11:33:46.000000000 +0200
@@ -33,15 +33,17 @@
 	However, this it experimental on 32-bit architectures, so if unsure say
 	N (on x86-64 it's automatically enabled, instead, as it's safe there).
 
 config STUB_CODE
 	hex
-	default 0xbfffe000
+	default 0xbfffe000 if !HOST_2G_2G
+	default 0x7fffe000 if HOST_2G_2G
 
 config STUB_DATA
 	hex
-	default 0xbffff000
+	default 0xbffff000 if !HOST_2G_2G
+	default 0x7ffff000 if HOST_2G_2G
 
 config STUB_START
 	hex
 	default STUB_CODE
 
--


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