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

[Deepak Gupta]

I think squashing is a better thing to do here.

On Wed, May 27, 2026 at 8:13 PM Jesse Huang <jesse.huang@sifive.com> wrote:
>
> 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
>> >