UML - Fix kernel stack size on x86_64

[ This is 2.6.22 material ]

Having KERNEL_STACK_ORDER in defconfig overrides the value provided by Kconfig, breaking UML/x86_64, which wants 2 page stacks.

Signed-off-by Jeff Dike <[email protected]>

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 arch/um/defconfig |    1 -
 1 file changed, 1 deletion(-)

Index: linux-2.6.21-mm/arch/um/defconfig
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Quoted 4 lines · On Tue, 5 Jun 2007 16:50:55 -0400 Jeff Dike <[email protected]> wrote:

[ This is 2.6.22 material ]

Having KERNEL_STACK_ORDER in defconfig overrides the value provided by Kconfig, breaking UML/x86_64, which wants 2 page stacks.

That means the Kconfig rules are wrong, surely?

Quoted 3 lines · Andrew Morton

On Tue, 5 Jun 2007 16:50:55 -0400
Jeff Dike <[email protected]> wrote:

Quoted 6 lines

Quoted 4 lines

[ This is 2.6.22 material ]

Having KERNEL_STACK_ORDER in defconfig overrides the value provided by Kconfig, breaking UML/x86_64, which wants 2 page stacks.

That means the Kconfig rules are wrong, surely?

I'm far from a Kconfig expert,

but what I have is

config KERNEL_STACK_ORDER
int "Kernel stack size order"
default 1 if 64BIT
default 0 if !64BIT

which seems reasonably clear and simple...

If you do

(quoted diff) +1 -1

-	int "Kernel stack size order"
+	int

then this rule will no longer be offered to the user and `make oldconfig' (actually anythingconfig) will override whatever happens to be in .config for KERNEL_STACK_ORDER.

I'm not sure if that's actually what you want, but if the current situation is that a random CONFIG_KERNEL_STACK_ORDER=0 left over in .config will break the kernel at runtime then I think something sterner than editing defconfig is needed?

Quoted 5 lines · Andrew Morton

If you do

(quoted diff) +1 -1

-	int "Kernel stack size order"
+	int

Quoted 3 lines

then this rule will no longer be offered to the user and `make oldconfig' (actually anythingconfig) will override whatever happens to be in .config for KERNEL_STACK_ORDER.

You're saying that making an option user-visible changes whether *config overrides .config? That's non-intuitive.

Quoted 4 lines

I'm not sure if that's actually what you want, but if the current situation is that a random CONFIG_KERNEL_STACK_ORDER=0 left over in .config will break the kernel at runtime then I think something sterner than editing defconfig is needed?

That's a good point, but I think I do want it user-visible. If someone sees someething I suspect to be a stack overflow, I'd like to be able to tell them to bump KERNEL_STACK_ORDER and see if the problem goes away.

As for something sterner, it turns out that Kbuild provides some support for this. So, drop the previous patch in favor of this one:

Force KERNEL_STACK_ORDER to be at least 1 on UML/x86_64.

Signed-off-by Jeff Dike <[email protected]>

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 arch/um/Kconfig |    1 +
 1 file changed, 1 insertion(+)

Index: linux-2.6.21-mm/arch/um/Kconfig
===================================================================