More robust search for filename in memory at runtime

diff --git a/usb-driver.c b/usb-driver.c
index ed7893262da4be37b5daf90c2b3fb5fe27634b9e..3b8b51d4747d2f8c9edf631f627171000268d78d 100644 (file)
--- a/usb-driver.c
+++ b/usb-driver.c
@@ -674,6 +674,18 @@ long int _Z14isModuleLoadedPci(char *module_name, int i) {
        return 1;
 }
 
+void cpr_segv_handler(int sig, siginfo_t *info, void *context) {
+       void *newmem;
+
+       DPRINTF("SEGV at %p, mapping memory\n", info->si_addr);
+       errno = 0;
+       newmem = mmap(info->si_addr, 1, PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, -1, 0);
+       if (newmem != info->si_addr) {
+               perror("libusb-driver.so: Can't map memory, crashing now");
+               exit(EXIT_FAILURE);
+       }
+}
+
 /* XilCommNS::CPortResources::Instance() */
 void* _ZN9XilCommNS14CPortResources8InstanceEv() {
        static void* (*func) (void) = NULL;
@@ -682,16 +694,33 @@ void* _ZN9XilCommNS14CPortResources8InstanceEv() {
        int i;
 
        if (!func) {
+               struct sigaction act, oldact;
+               int sighand_installed = 0;
+
                func = (void* (*) (void)) dlsym(RTLD_NEXT, "_ZN9XilCommNS14CPortResources8InstanceEv");
 
+               DPRINTF("Installing signal-handler for SIGSEGV\n");
+               bzero(&act, sizeof(struct sigaction));
+               act.sa_sigaction = cpr_segv_handler;
+               act.sa_flags = SA_SIGINFO;
+               if (sigaction(SIGSEGV, &act, &oldact) == 0) {
+                       sighand_installed = 1;
+               }
+
                DPRINTF("Searching for filename starting at %p\n", func);
-               for(i = 0; i < 16384; i++) {
+               for(i = 0; i < 32768; i++) {
                        if (!strcmp(((char*)func)+i, "/proc/sys/dev/parport/%s/base-addr")) {
                                filename = ((char*)func)+i;
                                DPRINTF("Filename found at offset %p\n", (void*)(filename - ((char*)func)));
                                break;
                        }
                }
+               if (sighand_installed) {
+                       DPRINTF("Restoring signal-handler for SIGSEGV\n");
+                       sigaction(SIGSEGV, &oldact, NULL);
+               }
+               if (!filename)
+                       fprintf(stderr, "libusb-driver.so: Can't find memory to patch, parallel cables will probably not work!\n");
        }
 
        if (filename) {