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Thu, 24 Oct 2024 20:00:35 +0000 (GMT) From: Ilya Leoshkevich To: Warner Losh , Riku Voipio , Laurent Vivier , Paolo Bonzini , Richard Henderson Cc: Kyle Evans , =?utf-8?q?Philippe_Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org, Ilya Leoshkevich Subject: [PATCH 4/8] user: Introduce host_interrupt_signal Date: Thu, 24 Oct 2024 21:59:11 +0200 Message-ID: <20241024200031.80327-5-iii@linux.ibm.com> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241024200031.80327-1-iii@linux.ibm.com> References: <20241024200031.80327-1-iii@linux.ibm.com> MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: E1DzbJSDmSJh46NHkAColofH41Kq1YrQ X-Proofpoint-GUID: E1DzbJSDmSJh46NHkAColofH41Kq1YrQ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 malwarescore=0 mlxscore=0 phishscore=0 priorityscore=1501 suspectscore=0 impostorscore=0 lowpriorityscore=0 spamscore=0 mlxlogscore=831 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2410240159 Received-SPF: pass client-ip=148.163.158.5; envelope-from=iii@linux.ibm.com; helo=mx0b-001b2d01.pphosted.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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 Attaching to the gdbstub of a running process requires stopping its threads. For threads that run on a CPU, cpu_exit() is enough, but the only way to grab attention of a thread that is stuck in a long-running syscall is to interrupt it with a signal. Reserve a host realtime signal for this, just like it's already done for TARGET_SIGABRT on Linux. This may reduce the number of available guest realtime signals by one, but this is acceptable, since there are quite a lot of them, and it's unlikely that there are apps that need them all. Set signal_pending for the safe_sycall machinery to prevent invoking the syscall. This is a lie, since we don't queue a guest signal, but process_pending_signals() can handle the absence of pending signals. The syscall returns with QEMU_ERESTARTSYS errno, which arranges for the automatic restart. This is important, because it helps avoiding disturbing poorly written guests. Signed-off-by: Ilya Leoshkevich --- bsd-user/signal.c | 12 ++++++++++++ include/user/signal.h | 2 ++ linux-user/signal.c | 11 +++++++++++ 3 files changed, 25 insertions(+) diff --git a/bsd-user/signal.c b/bsd-user/signal.c index a2b11a97131..992736df5c5 100644 --- a/bsd-user/signal.c +++ b/bsd-user/signal.c @@ -49,6 +49,8 @@ static inline int sas_ss_flags(TaskState *ts, unsigned long sp) on_sig_stack(ts, sp) ? SS_ONSTACK : 0; } +int host_interrupt_signal = SIGRTMAX; + /* * The BSD ABIs use the same signal numbers across all the CPU architectures, so * (unlike Linux) these functions are just the identity mapping. This might not @@ -489,6 +491,12 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) uintptr_t pc = 0; bool sync_sig = false; + if (host_sig == host_interrupt_signal) { + ts->signal_pending = 1; + cpu_exit(thread_cpu); + return; + } + /* * Non-spoofed SIGSEGV and SIGBUS are synchronous, and need special * handling wrt signal blocking and unwinding. @@ -852,6 +860,9 @@ void signal_init(void) for (i = 1; i <= TARGET_NSIG; i++) { host_sig = target_to_host_signal(i); + if (host_sig == host_interrupt_signal) { + continue; + } sigaction(host_sig, NULL, &oact); if (oact.sa_sigaction == (void *)SIG_IGN) { sigact_table[i - 1]._sa_handler = TARGET_SIG_IGN; @@ -870,6 +881,7 @@ void signal_init(void) sigaction(host_sig, &act, NULL); } } + sigaction(host_interrupt_signal, &act, NULL); } static void handle_pending_signal(CPUArchState *env, int sig, diff --git a/include/user/signal.h b/include/user/signal.h index 19b6b9e5ddc..7fa33b05d91 100644 --- a/include/user/signal.h +++ b/include/user/signal.h @@ -20,4 +20,6 @@ */ int target_to_host_signal(int sig); +extern int host_interrupt_signal; + #endif diff --git a/linux-user/signal.c b/linux-user/signal.c index 84bb8a34808..f0bcbd367d5 100644 --- a/linux-user/signal.c +++ b/linux-user/signal.c @@ -514,6 +514,8 @@ static int core_dump_signal(int sig) } } +int host_interrupt_signal; + static void signal_table_init(void) { int hsig, tsig, count; @@ -540,6 +542,7 @@ static void signal_table_init(void) hsig = SIGRTMIN; host_to_target_signal_table[SIGABRT] = 0; host_to_target_signal_table[hsig++] = TARGET_SIGABRT; + host_interrupt_signal = hsig++; for (tsig = TARGET_SIGRTMIN; hsig <= SIGRTMAX && tsig <= TARGET_NSIG; @@ -619,6 +622,8 @@ void signal_init(void) } sigact_table[tsig - 1]._sa_handler = thand; } + + sigaction(host_interrupt_signal, &act, NULL); } /* Force a synchronously taken signal. The kernel force_sig() function @@ -966,6 +971,12 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc) bool sync_sig = false; void *sigmask; + if (host_sig == host_interrupt_signal) { + ts->signal_pending = 1; + cpu_exit(thread_cpu); + return; + } + /* * Non-spoofed SIGSEGV and SIGBUS are synchronous, and need special * handling wrt signal blocking and unwinding. Non-spoofed SIGILL,