On Thursday 13 November 2014 16:02:49 AKASHI Takahiro wrote: > On 11/12/2014 08:19 PM, Arnd Bergmann wrote: > > On Wednesday 12 November 2014 11:13:52 Will Deacon wrote: > >> On Wed, Nov 12, 2014 at 11:06:59AM +0000, AKASHI Takahiro wrote: > >>> On 11/12/2014 08:00 PM, Will Deacon wrote: > >>>> On Wed, Nov 12, 2014 at 10:46:01AM +0000, AKASHI Takahiro wrote: > >>>>> On 11/07/2014 11:04 PM, Oleg Nesterov wrote: > >>>>>> To me the fact that PTRACE_SET_SYSCALL can be undefined and > >>>>>> syscall_set_nr() > >>>>>> is very much arch-dependant (but most probably trivial) means that > >>>>>> this code > >>>>>> should live in arch_ptrace(). > >>>>> > >>>>> Thinking of Oleg's comment above, it doesn't make sense neither to > >>>>> define generic > >>>>> NT_SYSTEM_CALL (user_regset) in uapi/linux/elf.h and implement it in > >>>>> ptrace_regset() > >>>>> in kernel/ptrace.c with arch-defined syscall_(g)set_nr(). > >>>>> > >>>>> Since we should have the same interface on arm and arm64, we'd better > >>>>> implement > >>>>> ptrace(PTRACE_SET_SYSCALL) locally on arm64 for now (as I originally > >>>>> submitted). > >>>> > >>>> I think the regset approach is cleaner. We already do something similar > >>>> for > >>>> TLS. That would be implemented under arch/arm64/ with it's own NT type. > >>> > >>> Okey, so arm64 goes its own way > >>> Or do you want to have a similar regset on arm, too? > >>> (In this case, NT_ARM_SYSTEM_CALL can be shared in uapi/linux/elf.h) > >> > >> Just do arm64. We already have the dedicated request for arch/arm/. > > > > I wonder if we should define NT_ARM64_SYSTEM_CALL to the same value > > as NT_S390_SYSTEM_CALL (0x307), or even define it as an architecture- > > independent NT_SYSTEM_CALL number with that value, so other architectures > > don't have to introduce new types when they also want to implement it. > > I digged into gdb code (gdb/bfd/elf.c): > https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob;f=bfd/elf.c;h=8b207ad872a3992381e93bdfa0a75ef444651613;hb=HEAD > elf_parse_notes()->elfcore_grok_note()->elfcore_grok_s390_system_call() > > It seems to me that NT_S390_SYSTEM_CALL(=0x307) is recognized as a s390 > specific > value (without checking for machine type). So thinking of potential conflict, > it might not be > a good idea to use this value as a common number (of NT_SYSTEM_CALL). > It's very unlikely that a "note" section for NT_(S390_)SYSTEM_CALL appears in > a coredump file, though. > > What do you think?
(adding Ulrich and Andreas) This code was introduced by http://sourceware-org.1504.n7.nabble.com/rfa-s390-bfd-part-Support-extended-register-sets-td50072.html I have to admit that I don't really understand gdb internals, but from a first look I get the impression that it will just do the right thing if you reuse NT_S390_SYSTEM_CALL on ARM64 with the same semantics. If not, we should indeed have a different number for it and duplicate that code. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
