On 9/9/26 12:57 PM, Bill Roberts wrote:
2. riscv should check that the low bit is set in locking not just
that its
0, it should be 1
I think for ABI compatibility RISC-V will have to continue accepting 0
as being equivalent to locking PR_SHADOW_STACK_ENABLE (or everything,
but it only supports that one bit right now).
TL;DR - No users, lets fix it before risc-v lands the userspace side IIUC
I can't find any libc's that support this for risc-v. It appears the
glibc
patches were not merged and I commented on those patches just now
that the interface is wrong:
-
https://inbox.sourceware.org/libc-alpha/[email protected]/
Additionally, stress-ng does it "generically", and it would be broken
on a riscv system:
-
https://sources.debian.org/src/stress-ng/0.22.00-2/stress-prctl.c?hl=1144#L1144
This is a bug and never followed the convention to begin with. So
risc-v is
non-compliant to the spec and this effectively prevents the a true
unification
of a generic prctl interface. The behavior on riscv doesn't adhere to
there own docs:
-
https://cdn.kernel.org/doc/html/latest/arch/riscv/zicfiss.html#prctl-enabling
Sorry I confused two interfaces here, anyway,
arch_set_shadow_stack_status is fine,
it's the locking interface arch_lock_shadow_stack_status, code snippet
below:
/* If shtstk not supported or not enabled on task, nothing to lock here */
if (!is_user_shstk_enabled() ||
!is_shstk_enabled(task) || arg != 0)
return -EINVAL;
So even the glibc patches will be fine. But definitely something we want
to fix.
I am going to float a patch over to the risc-v folks.
