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Peter Anvin" , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Lorenzo Stoakes , Paul Walmsley , Palmer Dabbelt , Albert Ou , Conor Dooley , Rob Herring , Krzysztof Kozlowski , Arnd Bergmann , Christian Brauner , Peter Zijlstra , Oleg Nesterov , Eric Biederman , Kees Cook , Jonathan Corbet , Shuah Khan , Jann Horn , Conor Dooley , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= , Andreas Hindborg , Alice Ryhl , Trevor Gross , Benno Lossin , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, alistair.francis@wdc.com, richard.henderson@linaro.org, jim.shu@sifive.com, andybnac@gmail.com, kito.cheng@sifive.com, charlie@rivosinc.com, atishp@rivosinc.com, evan@rivosinc.com, cleger@rivosinc.com, alexghiti@rivosinc.com, samitolvanen@google.com, broonie@kernel.org, rick.p.edgecombe@intel.com, rust-for-linux@vger.kernel.org, Zong Li , Andreas Korb , Valentin Haudiquet References: <20251204-v5_user_cfi_series-v24-0-ada7a3ba14dc@rivosinc.com> <20251204-v5_user_cfi_series-v24-25-ada7a3ba14dc@rivosinc.com> Content-Language: en-US From: Randy Dunlap In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 852DA140006 X-Stat-Signature: 853ifda6kq6ded317i3zf838n7p86ssm X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1764963748-224388 X-HE-Meta: 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 FdemtoqC 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 12/5/25 10:24 AM, Deepak Gupta wrote: > On Thu, Dec 04, 2025 at 02:17:27PM -0800, Randy Dunlap wrote: >> >> >> On 12/4/25 12:04 PM, Deepak Gupta wrote: >>> This patch creates a config for shadow stack support and landing pad instr >>> support. Shadow stack support and landing instr support can be enabled by >>> selecting `CONFIG_RISCV_USER_CFI`. Selecting `CONFIG_RISCV_USER_CFI` wires >>> up path to enumerate CPU support and if cpu support exists, kernel will >>> support cpu assisted user mode cfi. >>> >>> If CONFIG_RISCV_USER_CFI is selected, select `ARCH_USES_HIGH_VMA_FLAGS`, >>> `ARCH_HAS_USER_SHADOW_STACK` and DYNAMIC_SIGFRAME for riscv. >>> >>> Reviewed-by: Zong Li >>> Tested-by: Andreas Korb >>> Tested-by: Valentin Haudiquet >>> Signed-off-by: Deepak Gupta >>> --- >>>  arch/riscv/Kconfig                  | 22 ++++++++++++++++++++++ >>>  arch/riscv/configs/hardening.config |  4 ++++ >>>  2 files changed, 26 insertions(+) >>> >>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig >>> index 0c6038dc5dfd..f5574c6f66d8 100644 >>> --- a/arch/riscv/Kconfig >>> +++ b/arch/riscv/Kconfig >>> @@ -1146,6 +1146,28 @@ config RANDOMIZE_BASE >>> >>>            If unsure, say N. >>> >>> +config RISCV_USER_CFI >>> +    def_bool y >>> +    bool "riscv userspace control flow integrity" >>> +    depends on 64BIT && \ >>> +        $(cc-option,-mabi=lp64 -march=rv64ima_zicfiss_zicfilp -fcf-protection=full) >>> +    depends on RISCV_ALTERNATIVE >>> +    select RISCV_SBI >>> +    select ARCH_HAS_USER_SHADOW_STACK >>> +    select ARCH_USES_HIGH_VMA_FLAGS >>> +    select DYNAMIC_SIGFRAME >>> +    help >>> +      Provides CPU assisted control flow integrity to userspace tasks. >> >>                CPU-assisted >> >>> +      Control flow integrity is provided by implementing shadow stack for >>> +      backward edge and indirect branch tracking for forward edge in program. >>> +      Shadow stack protection is a hardware feature that detects function >>> +      return address corruption. This helps mitigate ROP attacks. >>> +      Indirect branch tracking enforces that all indirect branches must land >>> +      on a landing pad instruction else CPU will fault. This mitigates against >>> +      JOP / COP attacks. Applications must be enabled to use it, and old user- >>> +      space does not get protection "for free". >>> +      default y. >> >>       Default is y if hardware supports it. >> ? > > No default Y means support is built in the kernel for cfi. (if the compiler supports it?) > If hardware doesn't support CFI instructions, then kernel will do following > > - prctls to manage shadow stack/landing pad enable/disable will fail. > - vDSO will not have shadow stack instructions in it. Thanks for the info. -- ~Randy