[OpenBIOS] [PATCH] ppc: fix stack usage in mmu_claim, mem_claim

Mark Cave-Ayland mark.cave-ayland at ilande.co.uk
Thu Jun 18 00:30:37 CEST 2015

On 17/06/15 22:10, Segher Boessenkool wrote:

> On Wed, Jun 17, 2015 at 03:19:41PM -0500, Cormac O'Brien wrote:
>> The 'phys' argument to mem_claim() and 'virt' argument to mmu_claim() are now
>> only popped from the stack if the 'align' argument is provided.
> You probably also want to mention you no longer THROW when the
> return value is -1 (and explain why).

I'm not too worried about missing the throw here right now. As OpenBIOS
randomly switches between C and Forth at various points, not all of them
pick up the throw/catch across the boundaries correctly and make it back
to the caller.

One of the more recent changes I managed to do was to unmap page 0 on
all 3 of SPARC32, SPARC64 and PPC and still have everything boot. By
combining this with a default value of -1 for the OFMEM allocations it
means we die the first time a bad allocation is accessed, and it's easy
to work out where this happened with CONFIG_DEBUG_OFMEM enabled and
looking for values of -1.

>> +	phys_addr_t phys = -1UL;
> Is this the common style in this code?  Will "long int" always fit
> phys_addr_t?  Seems shaky.

In the original OFMEM implementation sizeof(phys_addr_t) == sizeof(virt)
== word size of machine. The only reason phys_addr_t is different here
was since SPARC32 was switched over to OFMEM as SPARC32 has a 36-bit
physical address space vs. a 32-bit virtual address space just to make
things more interesting :)  I haven't compile-tested this yet but if you
can suggest a better alternative, please do.



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