On Mon, Feb 9, 2009 at 10:02 AM, Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> wrote: > On Fri, 2009-02-06 at 16:17 -0800, Nauman Rafique wrote: >> The patch sent by Masahiko assumes that all the user-space registers >> are saved on >> the kernel stack on a system call. This is not true for the majority >> of the system calls. The callee saved registers (as defined by x86_64 >> ABI) - rbx, rbp, r12, r13, r14, r15 - are saved only in some special >> cases. That means that these registers would not be available to >> checkpoint code. Moreover, the restore code would have no space in >> stack to restore those registers. > > According to this: > > http://msdn.microsoft.com/en-us/library/6t169e9c(VS.80).aspx > > Those registers all get clobbered on all function calls. I assume that > userspace also considers them to get clobbered on system calls as > well. > > What are those special cases you are talking about? Certain special > cases for entering the kernel where we do save those registers? There are the system calls the use the same stub that I have used to save the full stack (and thus all the registers). sys_clone sys_fork sys_vfork sys_sigaltstack sys_iopl > > Signal handling and ptrace single stepping are two places I would > imagine we have to enter the kernel and preserve those registers. Is > that why you were suggesting overloading signal delivery? > > Thanks for pointing out the problem, though. This one will be > interesting. :) > > -- Dave > > _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
