Re: [Qemu-devel] [PATCH 4/5] linux-user: Add access to TLS registers

[Riku Voipio <riku.voipio@iki.fi>]

On Tue, Jan 26, 2010 at 05:27:27PM +0100, Laurent Desnogues wrote:
> On Tue, Jan 26, 2010 at 5:00 PM, Riku Voipio <riku.voipio@iki.fi> wrote:
> > From: Riku Voipio <riku.voipio@nokia.com>
> >
> > If you compile applications with gcc -mtp=cp15, __thread
> > access's will generate an abort. Implement accessing allowed
> > cp15.c13 registers on ARMv6K+ in linux-user.
> >
> > Signed-off-by: Riku Voipio <riku.voipio@nokia.com>
> > ---
> >  target-arm/helper.c |   27 ++++++++++++++++++++++++++-
> >  1 files changed, 26 insertions(+), 1 deletions(-)
> >
> > diff --git a/target-arm/helper.c b/target-arm/helper.c
> > index b3aec99..68578ce 100644
> > --- a/target-arm/helper.c
> > +++ b/target-arm/helper.c
> > @@ -505,13 +505,38 @@ uint32_t HELPER(get_cp)(CPUState *env, uint32_t insn)
> >
> >  void HELPER(set_cp15)(CPUState *env, uint32_t insn, uint32_t val)
> >  {
> > +    int op2;
> > +
> > +    op2 = (insn >> 5) & 7;
> > +    /* Allow write access to CP15 User RW Thread ID Register */
> > +    if (arm_feature (env, ARM_FEATURE_V6K) && ((insn >> 16) & 0xf) == 13) {
> > +        switch (op2) {
> > +        case 2:
> > +            env->cp15.c13_tls1 = val;
> > +            return;
> > +        }
> > +    }
> >     cpu_abort(env, "cp15 insn %08x\n", insn);
> >  }
> >
> >  uint32_t HELPER(get_cp15)(CPUState *env, uint32_t insn)
> >  {
> > +    int op2;
> > +    /* Allow read access to CP15 User RW and RO Thread ID Registers */
> > +
> > +    op2 = (insn >> 5) & 7;
> > +    if (arm_feature (env, ARM_FEATURE_V6K) && ((insn >> 16) & 0xf) == 13) {
> > +        switch (op2) {
> > +        case 2:
> > +            return env->cp15.c13_tls1;
> > +        case 3:
> > +            return env->cp15.c13_tls2;
> > +        default:
> > +            goto bad_reg;
> > +        }
> > +    }
> > +bad_reg:
> >     cpu_abort(env, "cp15 insn %08x\n", insn);
> > -    return 0;
> >  }
> >
> >  /* These should probably raise undefined insn exceptions.  */

> Most of the checks you do here could be done in translate.c.
> Wouldn't it be better to do them there?

Indeed, thus we could even avoid the helper completly. I just followed the the
cp15 implementation of system-qemu here.