Merge patch series "riscv: Userspace pointer masking and tagged address ABI"

Samuel Holland <samuel.holland@sifive.com> says:

RISC-V defines three extensions for pointer masking[1]:
 - Smmpm: configured in M-mode, affects M-mode
 - Smnpm: configured in M-mode, affects the next lower mode (S or U-mode)
 - Ssnpm: configured in S-mode, affects the next lower mode (VS, VU, or U-mode)

This series adds support for configuring Smnpm or Ssnpm (depending on
which privilege mode the kernel is running in) to allow pointer masking
in userspace (VU or U-mode), extending the PR_SET_TAGGED_ADDR_CTRL API
from arm64. Unlike arm64 TBI, userspace pointer masking is not enabled
by default on RISC-V. Additionally, the tag width (referred to as PMLEN)
is variable, so userspace needs to ask the kernel for a specific tag
width, which is interpreted as a lower bound on the number of tag bits.

This series also adds support for a tagged address ABI similar to arm64
and x86. Since accesses from the kernel to user memory use the kernel's
pointer masking configuration, not the user's, the kernel must untag
user pointers in software before dereferencing them. And since the tag
width is variable, as with LAM on x86, it must be kept the same across
all threads in a process so untagged_addr_remote() can work.

[1]: https://github.com/riscv/riscv-j-extension/raw/d70011dde6c2/zjpm-spec.pdf

* b4-shazam-merge:
  KVM: riscv: selftests: Add Smnpm and Ssnpm to get-reg-list test
  RISC-V: KVM: Allow Smnpm and Ssnpm extensions for guests
  riscv: hwprobe: Export the Supm ISA extension
  riscv: selftests: Add a pointer masking test
  riscv: Allow ptrace control of the tagged address ABI
  riscv: Add support for the tagged address ABI
  riscv: Add support for userspace pointer masking
  riscv: Add CSR definitions for pointer masking
  riscv: Add ISA extension parsing for pointer masking
  dt-bindings: riscv: Add pointer masking ISA extensions

Link: https://lore.kernel.org/r/20241016202814.4061541-1-samuel.holland@sifive.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>