Messages in this thread | | | Date | Mon, 23 Apr 2012 13:49:26 +0200 | Subject | MIPS ASID type conflicts | From | Jean-Christophe PINCE <> |
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Hi,
I am analyzing Linux MIPS tasks memory spaces and found out what I think is a bug in the ASID management.
The structure "struct cpuinfo_mips" defined in arch/mips/include/asm/cpu-info.h uses a "unsigned int" field for asid_cache while the context field defined in arch/mips/include/asm/mmu.h is a "unsigned long".
This is ok with 32bits kernel but leads to 4bytes vs 8bytes fields with a 64bits kernel. And when the scheduler checks if the ASID is of an older ASID_VERSION, the test will always return that the version differs when the context bits above bit31 will be set.
I imagine this should be a quite rare issue but could likely happen on devices running for very long and starting processes very often (or running more than 256 processes per cpu). When this condition (bit 32 or above of asid_cache is set), the effect should be that the TLB will be flushed on each context_switch required by the scheduler but there shouldn't be any crash.
Hope this helps, Thanks and regards, JC
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