On 11/12/13, 2:19 PM, Ingo Molnar wrote:
So this isn't very robust, because it assumes that all sources of SIGBUS are due to that memcpy() hitting -ENOSPC...There are several failure modes: - If mmap_jmp is not set yet and we get a SIGBUS is some other place, then the longjmp() result will be undefined. - If mmap_jmp environment is set, but we've returned from do_mmap_output() already, then the result will be undefined - likely a non-obvious crash. So at minimum we need a flag that tells us whether the jump environment is valid or not - i.e. whether we are executing inside the protected region or not - and only do the longjmp() if that flag is set.
Right I meant to add that -- a flag to know when the jmp should be used. Got distracted.
Is there really no other way to handle the -ENOSPC case robustly? I guess not because the memcpy() really needs memory to write to, but I thought I'd ask ...
You need some means to interrupt memcpy and bounce out of it. longjmp is the only option I know of.
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