Messages in this thread | | | Date | Wed, 14 May 2014 12:15:16 +0100 | From | Pedro Alves <> | Subject | Re: [PATCH V2 2/3] powerpc, ptrace: Enable support for transactional memory register sets |
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On 05/14/14 06:46, Anshuman Khandual wrote: > 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 think s390 returns ENODATA in that case.
https://sourceware.org/ml/gdb-patches/2013-06/msg00273.html
We'll want some way to tell whether the system actually supports this. That could be ENODATA vs something-else (EINVAL or perhaps better EIO for "request is invalid").
s390 actually screwed that, though it got away because there's a bit in HWCAP to signal transactions support. See:
https://sourceware.org/ml/gdb-patches/2013-11/msg00080.html
Are you adding something to HWCAP too?
> > 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.
-- Pedro Alves
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