Re: [PATCH v4 2/6] arm64: Add more test functions to insn.c

[David Long]

On 01/14/15 04:32, Pratyush Anand wrote:
> On Sun, Jan 11, 2015 at 9:33 AM, David Long <dave.long@xxxxxxxxxx> wrote:
> > From: "David A. Long" <dave.long@xxxxxxxxxx>
> >
> > Certain instructions are hard to execute correctly out-of-line (as in
> > kprobes).  Test functions are added to insn.[hc] to identify these.  The
> > instructions include any that use PC-relative addressing, change the PC,
> > or change interrupt masking. For efficiency and simplicity test
> > functions are also added for small collections of related instructions.
> >
> > Signed-off-by: David A. Long <dave.long@xxxxxxxxxx>
> > ---
> >   arch/arm64/include/asm/insn.h | 21 +++++++++++++++++++--
> >   arch/arm64/kernel/insn.c      | 18 ++++++++++++++++++
> >   2 files changed, 37 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
> > index e2ff32a..466afd4 100644
> > --- a/arch/arm64/include/asm/insn.h
> > +++ b/arch/arm64/include/asm/insn.h
> > @@ -223,8 +223,13 @@ static __always_inline bool aarch64_insn_is_##abbr(u32 code) \
> >   static __always_inline u32 aarch64_insn_get_##abbr##_value(void) \
> >   { return (val); }
> >
> > +__AARCH64_INSN_FUNCS(adr,      0x9F000000, 0x10000000)
>
> Should n't it be
> __AARCH64_INSN_FUNCS(adr_adrp,      0x1F000000, 0x10000000)
>
> So, that it also take care about adrp

Yes, that does look like a mistake.

> > +__AARCH64_INSN_FUNCS(prfm_lit, 0xFF000000, 0xD8000000)
>
> [...]
>
> > +bool aarch64_insn_uses_literal(u32 insn)
> > +{
> > +       /* ldr/ldrsw (literal), prfm */
> > +
> > +       return aarch64_insn_is_ldr_lit(insn) ||
> > +               aarch64_insn_is_ldrsw_lit(insn) ||
>
> also aarch64_insn_is_adr_adrp(insn) ||

Yup.

> > +               aarch64_insn_is_prfm_lit(insn);
> > +}
> > +
> > +bool aarch64_insn_is_branch(u32 insn)
> > +{
> > +       /* b, bl, cb*, tb*, b.cond, br, blr */
> > +
> > +       return aarch64_insn_is_b_bl_cb_tb(insn) ||
> > +               aarch64_insn_is_br_blr(insn) ||
>
> also aarch64_insn_is_ret(insn) ||

The goal was to catch intructions that use a PC-relative branch, since 
the PC will not be what is expected.  Of course any instruction that 
changes the PC will have a problem too because the PC will be rewritten 
after the probe is completed.  So, yeah, this needs to be fixed.

> > +               aarch64_insn_is_bcond(insn);
> > +}
> > +
> >   /*

-dl

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