Dave Martin <dave.mar...@linaro.org> wrote: > On Thu, Mar 24, 2011 at 2:57 PM, Ulrich Weigand <ulrich.weig...@de.ibm.com> wrote: > > 1) Have *two* new note types, one for VFP, and one for NEON > > That may not make sense, since really it's a single register file > shared by VFP and NEON. With NEON, you always have 32 x 64-bit regs, > but it's possible (although rare) to have this many regs on ARMv7 even > if NEON is absent.
OK, agreed. > > 2) Have GDB look into the AT_HWCAP setting in the NT_AUXV note > > > > Option 2) seems preferable to me, since NT_AUXV is already there, > > and it can also be used to detect the integer-only NEON case. > > We could also dump the relevant hardware capability registers, which > can be more informative, though I'm in two minds about whether this is > appropriate / beneficial. A layout something like this might work: > > NT_VFPREGSET* > > unsigned long flags; > unsigned long feature_registers[3]; > unsigned long fpscr; > unsigned long long regs[16 or 32]; > > There are currently 3 relevant feature registers, the main > floating-point ID register FPSID, and the floating-point / SIMD > feature registers MVFR0, MVFR1. > > In either case, we define the contents of the flags field in such a > way as to allow gdb to understand the format, and to allow for future > expansion if this is ever needed. > > (*The note types seem to use different names in linux/elf.h compared > with /usr/include/elf.h and GDB. I've followed the outside world's > convention here.) I would prefer to keep the contents of NT_VFPREGSET identical to the contents of the PTRACE_GETVPFREGS/PTRACE_SETVPFREGS buffer: - This would allow implementation via the new generic user_regset_view mechanism (which the ARM kernel doesn't use yet, but probably should) - In any case, GDB likes to have the same set of information available when debugging core files and native targets So if there is indeed additional information that would be interesting, I'd argue this should be presented as a *new* core file note, *and* as a new set of PTRACE_... APIs. (But for GDB's purpose NT_AUXV right now is sufficent. Everything else could be displayed to the user if of interest.) Mit freundlichen Gruessen / Best Regards Ulrich Weigand -- Dr. Ulrich Weigand | Phone: +49-7031/16-3727 STSM, GNU compiler and toolchain for Linux on System z and Cell/B.E. IBM Deutschland Research & Development GmbH Vorsitzender des Aufsichtsrats: Martin Jetter | Geschäftsführung: Dirk Wittkopp Sitz der Gesellschaft: Böblingen | Registergericht: Amtsgericht Stuttgart, HRB 243294 _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
