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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2001:4860:4864:20::34; envelope-from=richard.henderson@linaro.org; helo=mail-oa1-x34.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 10/30/23 22:32, Ilya Leoshkevich wrote: > +int main(void) > +{ > + register unsigned long r0 asm("r0"); > + unsigned long mem = 42, rhs = 500; > + struct sigaction act; > + int err; > + > + memset(&act, 0, sizeof(act)); > + act.sa_sigaction = handle_sigsegv; > + act.sa_flags = SA_SIGINFO; > + err = sigaction(SIGSEGV, &act, NULL); > + assert(err == 0); > + > + r0 = 100; > + asm("algr %[r0],%[rhs]\n" > + "clc 0(8,%[mem]),0(0)\n" /* The 2nd operand will cause a SEGV. */ > + : [r0] "+r" (r0) > + : [mem] "r" (&mem) > + , [rhs] "r" (rhs) > + : "cc", "memory"); > + You could just as easily set cc based on CHI or something to avoid hard-coding r0, or even clobbering an output register at all. But I guess there's little point bike shedding this too much... r~