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Thu, 24 Jul 2025 16:37:13 -0700 (PDT) From: Deepak Gupta Date: Thu, 24 Jul 2025 16:36:57 -0700 Subject: [PATCH 04/11] riscv: exception handlers can be software guarded transfers Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250724-riscv_kcfi-v1-4-04b8fa44c98c@rivosinc.com> References: <20250724-riscv_kcfi-v1-0-04b8fa44c98c@rivosinc.com> In-Reply-To: <20250724-riscv_kcfi-v1-0-04b8fa44c98c@rivosinc.com> To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Masahiro Yamada , Nathan Chancellor , Nicolas Schier , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Nick Desaulniers , Bill Wendling , Monk Chiang , Kito Cheng , Justin Stitt Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, rick.p.edgecombe@intel.com, broonie@kernel.org, cleger@rivosinc.com, samitolvanen@google.com, apatel@ventanamicro.com, ajones@ventanamicro.com, conor.dooley@microchip.com, charlie@rivosinc.com, samuel.holland@sifive.com, bjorn@rivosinc.com, fweimer@redhat.com, jeffreyalaw@gmail.com, heinrich.schuchardt@canonical.com, andrew@sifive.com, ved@rivosinc.com, Deepak Gupta X-Mailer: b4 0.13.0 Exception handlers are static and loaded from readonly memory. Control transfers can be software guarded and not requiring lpad on target. Signed-off-by: Deepak Gupta --- arch/riscv/kernel/entry.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 598e17e800ae..3f0890b9c0b9 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -224,12 +224,12 @@ SYM_CODE_START(handle_exception) add t0, t1, t0 /* Check if exception code lies within bounds */ bgeu t0, t2, 3f - REG_L t1, 0(t0) -2: jalr t1 + REG_L t2, 0(t0) +2: jalr t2 j ret_from_exception 3: =20 - la t1, do_trap_unknown + la t2, do_trap_unknown j 2b SYM_CODE_END(handle_exception) ASM_NOKPROBE(handle_exception) --=20 2.43.0