[PATCH v4 06/17] riscv/cfi: Add prctl definitions for RISC-V CFI

[Jesse Huang]

Hi Deepak,

I have a separate commit for updating the interfaces, it's the last one in
this series. Please check it out.
Or you think is better to squash it into the these older commits?

Thanks,

On Wed, May 27, 2026 at 2:33 AM Deepak Gupta <debug@rivosinc.com> wrote:

> Hi Jesse,
>
> comments inline.
>
> On Mon, May 25, 2026 at 11:18 PM Jesse Huang <jesse.huang@sifive.com>
> wrote:
> >
> > These operations are for setting/retrieving/locking the status of the
> > landing pad and the shadow stack extensions.
> > ---
> >  .../unix/sysv/linux/riscv/include/asm/prctl.h | 48 +++++++++++++++++++
> >  1 file changed, 48 insertions(+)
> >  create mode 100644 sysdeps/unix/sysv/linux/riscv/include/asm/prctl.h
> >
> > diff --git a/sysdeps/unix/sysv/linux/riscv/include/asm/prctl.h
> b/sysdeps/unix/sysv/linux/riscv/include/asm/prctl.h
> > new file mode 100644
> > index 0000000000..091a21b70d
> > --- /dev/null
> > +++ b/sysdeps/unix/sysv/linux/riscv/include/asm/prctl.h
> > @@ -0,0 +1,48 @@
> > +/*
> > + * Get the current shadow stack configuration for the current thread,
> > + * this will be the value configured via PR_SET_SHADOW_STACK_STATUS.
> > + */
> > +#define PR_GET_SHADOW_STACK_STATUS     74
> > +
> > +/*
> > + * Set the current shadow stack configuration.  Enabling the shadow
> > + * stack will cause a shadow stack to be allocated for the thread.
> > + */
> > +#define PR_SET_SHADOW_STACK_STATUS     75
> > +# define PR_SHADOW_STACK_ENABLE                (1UL << 0)
> > +# define PR_SHADOW_STACK_WRITE         (1UL << 1)
> > +# define PR_SHADOW_STACK_PUSH          (1UL << 2)
> > +
> > +/*
> > + * Prevent further changes to the specified shadow stack
> > + * configuration.  All bits may be locked via this call, including
> > + * undefined bits.
> > + */
> > +#define PR_LOCK_SHADOW_STACK_STATUS    76
> > +
> > +/*
> > + * Get the current indirect branch tracking configuration for the
> current
> > + * thread, this will be the value configured via
> PR_SET_INDIR_BR_LP_STATUS.
> > + */
> > +#define PR_GET_INDIR_BR_LP_STATUS      79
>
> I think paul has sent out patches for changing names of prctls for landing
> pad.
> Value remains same but names are being changed.
>
> > +
> > +/*
> > + * Set the indirect branch tracking configuration.
> PR_INDIR_BR_LP_ENABLE will
> > + * enable cpu feature for user thread, to track all indirect branches
> and ensure
> > + * they land on arch defined landing pad instruction.
> > + * x86 - If enabled, an indirect branch must land on `ENDBRANCH`
> instruction.
> > + * arch64 - If enabled, an indirect branch must land on `BTI`
> instruction.
> > + * riscv - If enabled, an indirect branch must land on `lpad`
> instruction.
> > + * PR_INDIR_BR_LP_DISABLE will disable feature for user thread and
> indirect
> > + * branches will no more be tracked by cpu to land on arch defined
> landing pad
> > + * instruction.
> > + */
> > +#define PR_SET_INDIR_BR_LP_STATUS      80
> > +# define PR_INDIR_BR_LP_ENABLE         (1UL << 0)
> > +
> > +/*
> > + * Prevent further changes to the specified indirect branch tracking
> > + * configuration.  All bits may be locked via this call, including
> > + * undefined bits.
> > + */
> > +#define PR_LOCK_INDIR_BR_LP_STATUS     81
> > --
> > 2.43.7
> >
>
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