Merge branch 'feature/increase-signal-safety'

src/daemon/includes.h

@@ -17,8 +17,10 @@
 #include <sys/errno.h>
 #include <sys/ioctl.h>
 #include <sys/signal.h>
+#include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/time.h>
+#include <sys/types.h>
 
 // Unsigned char/short definition
 typedef unsigned char uchar;
@@ -67,5 +69,7 @@ void timespec_add(struct timespec* timespec, long nanoseconds);
 #include "structures.h"
 
 #define THREAD_NAME_MAX 16
+#define SIGHANDLER_SENDER   0
+#define SIGHANDLER_RECEIVER 1
 
 #endif  // INCLUDES_H

src/daemon/main.c

@@ -11,6 +11,8 @@ extern int features_mask;
 // device.c
 extern int hwload_mode;
 
+int sighandler_pipe[2] = { 0, 0 };
+
 // Timespec utility function
 void timespec_add(struct timespec* timespec, long nanoseconds){
     nanoseconds += timespec->tv_nsec;
@@ -40,20 +42,56 @@ static void quit() {
     usbkill();
 }
 
-void sighandler2(int type){
-    // Don't use ckb_warn, we want an extra \n at the beginning
-    printf("\n[W] Ignoring signal %d (already shutting down)\n", type);
+///
+/// \brief ignore_signal
+/// Nested signal handler for previously received signals.
+/// \param type received signal type
+void ignore_signal(int type){
+    // Use signal-safe(7) write(3) call to print warning
+    write(1, "\n[W] Ignoring signal ", 22);
+    switch (type) {
+        case SIGTERM:
+            write(1, "SIGTERM", 7);
+            break;
+        case SIGINT:
+            write(1, "SIGINT", 6);
+            break;
+        case SIGQUIT:
+            write(1, "SIGQUIT", 7);
+            break;
+        default:
+            write(1, "UNKNOWN", 7);
+            break;
+    }
+    write(1, " (already shutting down)\n", 27);
 }
 
-void sighandler(int type){
-    signal(SIGTERM, sighandler2);
-    signal(SIGINT, sighandler2);
-    signal(SIGQUIT, sighandler2);
+///
+/// \brief exithandler
+/// Main signal handler to catch further signals and call shutdown
+/// sequence of daemon. This function is allowed to call unsafe
+/// (signal-safe(7)) function calls, as it is itself executed in another
+/// process via the socket handler.
+/// \param type received signal type
+void exithandler(int type){
+    signal(SIGTERM, ignore_signal);
+    signal(SIGINT, ignore_signal);
+    signal(SIGQUIT, ignore_signal);
+
     printf("\n[I] Caught signal %d\n", type);
     quit();
     exit(0);
 }
 
+///
+/// \brief signalhandler
+/// Write the received signal type to the socketpair for signal-safe(7)
+/// signal handling.
+/// \param type received signal type
+void sighandler(int type){
+    write(sighandler_pipe[SIGHANDLER_SENDER], &type, sizeof(int));
+}
+
 void localecase(char* dst, size_t length, const char* src){
     char* ldst = dst + length;
     char s;
@@ -194,17 +232,14 @@ int main(int argc, char** argv){
     if(!mkdevpath(keyboard))
         ckb_info("Root controller ready at %s0\n", devpath);
 
-    // Set signals
-    sigset_t signals;
-    sigfillset(&signals);
-    sigdelset(&signals, SIGTERM);
-    sigdelset(&signals, SIGINT);
-    sigdelset(&signals, SIGQUIT);
-    // Set up signal handlers for quitting the service.
-    sigprocmask(SIG_SETMASK, &signals, 0);
-    signal(SIGTERM, sighandler);
-    signal(SIGINT, sighandler);
-    signal(SIGQUIT, sighandler);
+    // Attempt to setup signal-safe signal handlers using socketpair(2)
+    if (socketpair(AF_LOCAL, SOCK_STREAM, 0, sighandler_pipe) != -1){
+        signal(SIGTERM, sighandler);
+        signal(SIGINT, sighandler);
+        signal(SIGQUIT, sighandler);
+    } else
+        ckb_warn_nofile("Unable to setup signal handlers\n");
+
 
     // Start the USB system
     int result = usbmain();

src/daemon/usb.h

@@ -217,7 +217,7 @@ const char* product_str(ushort product);
 #define IS_MOUSEPAD_DEV(kb)             IS_MOUSEPAD((kb)->vendor, (kb)->product)
 
 #define USB_DELAY_DEFAULT   5
-        
+
 /// Start the USB main loop. Returns program exit code when finished
 int usbmain();
 
@@ -380,4 +380,8 @@ int usb_tryreset(usbdevice* kb);
 
 void print_urb_buffer(const char* prefix, const unsigned char* buffer, int actual_length, const char* file, int line, const char* function, int devnum);
 
+// receive message from initial sighandler socketpair communication
+extern int sighandler_pipe[2];
+extern void exithandler(int type);
+
 #endif  // USB_H

src/daemon/usb_linux.c

@@ -778,6 +778,7 @@ int usbmain(){
     udev_monitor_enable_receiving(monitor);
     // Get an fd for the monitor
     int fd = udev_monitor_get_fd(monitor);
+
     fd_set fds;
     while(udev){
         FD_ZERO(&fds);
@@ -803,6 +804,18 @@ int usbmain(){
             } else if(!strcmp(action, "remove"))
                 usb_rm_device(dev);
             udev_device_unref(dev);
+        } else {
+            // if select returns -1 there is a chance that the waiting
+            // was interrupted by a signal
+            // check whether there is data available in the
+            // sighandler_pipe, read if there is and manually call the
+            // signal-handling routine
+            int sighandler_msg;
+            ioctl(sighandler_pipe[SIGHANDLER_RECEIVER], FIONREAD, &sighandler_msg);
+            if (sighandler_msg > 0){
+                read(sighandler_pipe[SIGHANDLER_RECEIVER], &sighandler_msg, sizeof(int));
+                exithandler(sighandler_msg);
+            }
         }
     }
     udev_monitor_unref(monitor);

src/daemon/usb_mac.c

@@ -952,6 +952,17 @@ void powerEventCallback(void *refcon, io_service_t service, uint32_t type, void
     }
 }
 
+///
+/// \brief mac_exithandler
+/// Thin layer to deconstruct the CFSocket object into a native one,
+/// reading the received data from that, and passing it on to the main
+/// exithandler function.
+void mac_exithandler(CFSocketRef s, CFSocketCallBackType t, CFDataRef a, const void *data, void *info) {
+    int type;
+    read(CFSocketGetNative(s), &type, sizeof(int));
+    exithandler(type);
+}
+
 int usbmain(){
     int vendor = V_CORSAIR;
 
@@ -1034,6 +1045,18 @@ int usbmain(){
     IORegisterForSystemPower(NULL, &notify, powerEventCallback, &iterator_syspower);
     CFRunLoopAddSource(mainloop, IONotificationPortGetRunLoopSource(notify), kCFRunLoopDefaultMode);
 
+    // setup signal handling via CoreFoundation socket callout mechanism
+    // see mac_exithandler for the reading side of this setup
+    CFSocketRef cf_socket = CFSocketCreateWithNative(
+            NULL,
+            sighandler_pipe[SIGHANDLER_RECEIVER],
+            kCFSocketReadCallBack,
+            mac_exithandler,
+            NULL);
+    CFRunLoopSourceRef socket_source = CFSocketCreateRunLoopSource(NULL, cf_socket, 0);
+
+    CFRunLoopAddSource(mainloop, socket_source, kCFRunLoopCommonModes);
+
     // Enter loop to scan/connect new devices
     CFRunLoopRun();
     return 0;