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    SubjectRe: [PATCH V2 2/3] powerpc, ptrace: Enable support for transactional memory register sets
    On 05/13/2014 10:43 PM, Pedro Alves wrote:
    > On 05/05/14 08:54, Anshuman Khandual wrote:
    >> This patch enables get and set of transactional memory related register
    >> sets through PTRACE_GETREGSET/PTRACE_SETREGSET interface by implementing
    >> four new powerpc specific register sets i.e REGSET_TM_SPR, REGSET_TM_CGPR,
    >> REGSET_TM_CFPR, REGSET_CVMX support corresponding to these following new
    >> ELF core note types added previously in this regard.
    >>
    >> (1) NT_PPC_TM_SPR
    >> (2) NT_PPC_TM_CGPR
    >> (3) NT_PPC_TM_CFPR
    >> (4) NT_PPC_TM_CVMX
    >
    > Sorry that I couldn't tell this from the code, but, what does the
    > kernel return when the ptracer requests these registers and the
    > program is not in a transaction? Specifically I'm wondering whether
    > this follows the same semantics as the s390 port.
    >

    Right now, it still returns the saved state of the registers from thread
    struct. I had assumed that the user must know the state of the transaction
    before initiating the ptrace request. I guess its better to check for
    the transaction status before processing the request. In case if TM is not
    active on that thread, we should return -EINVAL.

    I am not familiar with the s390 side of code. But if we look at the
    s390_tdb_get function it checks for (regs->int_code & 0x200) before
    processing the request. Not sure what 0x200 signifies though.



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