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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 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit 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 X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C971C140002 X-Stat-Signature: nx1kmtr3axe71bk15msq9i9mzi477cc8 X-HE-Tag: 1753400235-438328 X-HE-Meta: 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 XGpL4L96 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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: 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: - la t1, do_trap_unknown + la t2, do_trap_unknown j 2b SYM_CODE_END(handle_exception) ASM_NOKPROBE(handle_exception) -- 2.43.0