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%3Ba=blob%3Bf=bfd/el... 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-...
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