use of memory barriers in the shm server and client code

library/DFHackAPI.cpp

@@ -969,6 +969,10 @@ bool API::Attach()
     {
         d->pm = new ProcessEnumerator (d->xml); // FIXME: handle bad XML better
     }
+    else
+    {
+        d->pm->purge();
+    }
 
     // find a process (ProcessManager can find multiple when used properly)
     if (!d->pm->findProcessess())

library/DFProcess-linux-SHM.cpp

@@ -28,8 +28,50 @@ distribution.
 #include <sys/ipc.h>
 #include <time.h>
 #include "shmserver/dfconnect.h"
+#include <sys/time.h>
+#include <time.h>
+#include <linux/futex.h>
+#include <sys/syscall.h>
 using namespace DFHack;
 
+// a full memory barrier! better be safe than sorry.
+#define gcc_barrier asm volatile("" ::: "memory"); __sync_synchronize();
+
+/*
+* wait for futex
+* futex has to be aligned to 4 bytes
+* futex has to be equal to val (returns EWOULDBLOCK otherwise)
+* wait can be broken by arriving signals (returns EINTR)
+* returns 0 when broken by futex_wake
+*/
+inline int futex_wait(int * futex, int val)
+{
+    return syscall(SYS_futex, futex, FUTEX_WAIT, val, 0, 0, 0);
+}
+/*
+* wait for futex
+* futex has to be aligned to 4 bytes
+* futex has to be equal to val (returns EWOULDBLOCK otherwise)
+* wait can be broken by arriving signals (returns EINTR)
+* returns 0 when broken by futex_wake
+* returns ETIMEDOUT on timeout
+*/
+inline int futex_wait_timed(int * futex, int val, const struct timespec *timeout)
+{
+    return syscall(SYS_futex, futex, FUTEX_WAIT, val, timeout, 0, 0);
+}
+/*
+* wake up futex. returns number of waked processes
+*/
+inline int futex_wake(int * futex)
+{
+    return syscall(SYS_futex, futex, FUTEX_WAKE, 1, 0, 0, 0);
+}
+static timespec one_second = { 1,0 };
+static timespec five_second = { 5,0 };
+
+
+
 class SHMProcess::Private
 {
     public:
@@ -38,6 +80,8 @@ class SHMProcess::Private
         my_datamodel = NULL;
         my_descriptor = NULL;
         my_pid = 0;
+        my_shm = 0;
+        my_shmid = -1;
         my_window = NULL;
         attached = false;
         suspended = false;
@@ -54,6 +98,7 @@ class SHMProcess::Private
     bool attached;
     bool suspended;
     bool identified;
+    
     bool validate(char * exe_file, uint32_t pid, vector <memory_info> & known_versions);
     bool waitWhile (DF_PINGPONG state);
     bool DF_TestBridgeVersion(bool & ret);
@@ -71,6 +116,7 @@ bool SHMProcess::Private::waitWhile (DF_PINGPONG state)
             shmctl(my_shmid, IPC_STAT, &descriptor); 
             if(descriptor.shm_nattch == 1)// DF crashed?
             {
+                gcc_barrier
                 ((shm_cmd *)my_shm)->pingpong = DFPP_RUNNING;
                 attached = suspended = false;
                 return false;
@@ -96,8 +142,10 @@ bool SHMProcess::Private::waitWhile (DF_PINGPONG state)
 bool SHMProcess::Private::DF_TestBridgeVersion(bool & ret)
 {
     ((shm_cmd *)my_shm)->pingpong = DFPP_VERSION;
+    gcc_barrier
     if(!waitWhile(DFPP_VERSION))
         return false;
+    gcc_barrier
     ((shm_cmd *)my_shm)->pingpong = DFPP_SUSPENDED;
     ret =( ((shm_retval *)my_shm)->value == PINGPONG_VERSION );
     return true;
@@ -106,8 +154,10 @@ bool SHMProcess::Private::DF_TestBridgeVersion(bool & ret)
 bool SHMProcess::Private::DF_GetPID(pid_t & ret)
 {
     ((shm_cmd *)my_shm)->pingpong = DFPP_PID;
+    gcc_barrier
     if(!waitWhile(DFPP_PID))
         return false;
+    gcc_barrier
     ((shm_cmd *)my_shm)->pingpong = DFPP_SUSPENDED;
     ret = ((shm_retval *)my_shm)->value;
     return true;
@@ -139,11 +189,12 @@ SHMProcess::SHMProcess(vector <memory_info> & known_versions)
     /*
      * Check if there are two processes connected to the segment
      */
-    struct shmid_ds descriptor;
+    shmid_ds descriptor;
     shmctl(d->my_shmid, IPC_STAT, &descriptor); 
     if(descriptor.shm_nattch != 2)// badness
     {
-        fprintf(stderr,"dfhack: no DF or different client already connected\n");
+        fprintf(stderr,"dfhack: %d : invalid no. of processes connected\n", descriptor.shm_nattch);
+        fprintf(stderr,"detach: %d",shmdt(d->my_shm));
         return;
     }
     
@@ -182,8 +233,10 @@ SHMProcess::SHMProcess(vector <memory_info> & known_versions)
         d->validate(target_name, d->my_pid, known_versions);
         d->my_window = new DFWindow(this);
     }
+    gcc_barrier
     // at this point, DF is stopped and waiting for commands. make it run again
     ((shm_cmd *)d->my_shm)->pingpong = DFPP_RUNNING;
+    fprintf(stderr,"detach: %d",shmdt(d->my_shm));
 }
 
 bool SHMProcess::isSuspended()
@@ -239,6 +292,10 @@ SHMProcess::~SHMProcess()
     {
         delete d->my_window;
     }
+    if(d->my_shm)
+    {
+        fprintf(stderr,"detach: %d",shmdt(d->my_shm));
+    }
     delete d;
 }
 
@@ -341,15 +398,23 @@ bool SHMProcess::attach()
         cerr << "there's already a different process attached" << endl;
         return false;
     }
-    d->attached = true;
-    if(suspend())
+    /*
+    * Attach the segment
+    */
+    if ((d->my_shm = (char *) shmat(d->my_shmid, NULL, 0)) != (char *) -1)
     {
-        d->suspended = true;
-        g_pProcess = this;
-        return true;
+        d->attached = true;
+        if(suspend())
+        {
+            d->suspended = true;
+            g_pProcess = this;
+            return true;
+        }
+        d->attached = false;
+        cerr << "unable to suspend" << endl;
+        return false;
     }
-    d->attached = false;
-    cerr << "unable to suspend" << endl;
+    cerr << "unable to attach" << endl;
     return false;
 }
 
@@ -375,6 +440,7 @@ void SHMProcess::read (const uint32_t offset, const uint32_t size, uint8_t *targ
     assert (size < (SHM_SIZE - sizeof(shm_read)));
     ((shm_read *)d->my_shm)->address = offset;
     ((shm_read *)d->my_shm)->length = size;
+    gcc_barrier
     ((shm_read *)d->my_shm)->pingpong = DFPP_READ;
     d->waitWhile(DFPP_READ);
     memcpy (target, d->my_shm + sizeof(shm_ret_data),size);
@@ -383,6 +449,7 @@ void SHMProcess::read (const uint32_t offset, const uint32_t size, uint8_t *targ
 uint8_t SHMProcess::readByte (const uint32_t offset)
 {
     ((shm_read_small *)d->my_shm)->address = offset;
+    gcc_barrier
     ((shm_read_small *)d->my_shm)->pingpong = DFPP_READ_BYTE;
     d->waitWhile(DFPP_READ_BYTE);
     return ((shm_retval *)d->my_shm)->value;
@@ -391,6 +458,7 @@ uint8_t SHMProcess::readByte (const uint32_t offset)
 void SHMProcess::readByte (const uint32_t offset, uint8_t &val )
 {
     ((shm_read_small *)d->my_shm)->address = offset;
+    gcc_barrier
     ((shm_read_small *)d->my_shm)->pingpong = DFPP_READ_BYTE;
     d->waitWhile(DFPP_READ_BYTE);
     val = ((shm_retval *)d->my_shm)->value;
@@ -399,6 +467,7 @@ void SHMProcess::readByte (const uint32_t offset, uint8_t &val )
 uint16_t SHMProcess::readWord (const uint32_t offset)
 {
     ((shm_read_small *)d->my_shm)->address = offset;
+    gcc_barrier
     ((shm_read_small *)d->my_shm)->pingpong = DFPP_READ_WORD;
     d->waitWhile(DFPP_READ_WORD);
     return ((shm_retval *)d->my_shm)->value;
@@ -407,6 +476,7 @@ uint16_t SHMProcess::readWord (const uint32_t offset)
 void SHMProcess::readWord (const uint32_t offset, uint16_t &val)
 {
     ((shm_read_small *)d->my_shm)->address = offset;
+    gcc_barrier
     ((shm_read_small *)d->my_shm)->pingpong = DFPP_READ_WORD;
     d->waitWhile(DFPP_READ_WORD);
     val = ((shm_retval *)d->my_shm)->value;
@@ -415,6 +485,7 @@ void SHMProcess::readWord (const uint32_t offset, uint16_t &val)
 uint32_t SHMProcess::readDWord (const uint32_t offset)
 {
     ((shm_read_small *)d->my_shm)->address = offset;
+    gcc_barrier
     ((shm_read_small *)d->my_shm)->pingpong = DFPP_READ_DWORD;
     d->waitWhile(DFPP_READ_DWORD);
     return ((shm_retval *)d->my_shm)->value;
@@ -422,6 +493,7 @@ uint32_t SHMProcess::readDWord (const uint32_t offset)
 void SHMProcess::readDWord (const uint32_t offset, uint32_t &val)
 {
     ((shm_read_small *)d->my_shm)->address = offset;
+    gcc_barrier
     ((shm_read_small *)d->my_shm)->pingpong = DFPP_READ_DWORD;
     d->waitWhile(DFPP_READ_DWORD);
     val = ((shm_retval *)d->my_shm)->value;
@@ -435,6 +507,7 @@ void SHMProcess::writeDWord (uint32_t offset, uint32_t data)
 {
     ((shm_write_small *)d->my_shm)->address = offset;
     ((shm_write_small *)d->my_shm)->value = data;
+    gcc_barrier
     ((shm_write_small *)d->my_shm)->pingpong = DFPP_WRITE_DWORD;
     d->waitWhile(DFPP_WRITE_DWORD);
 }
@@ -444,6 +517,7 @@ void SHMProcess::writeWord (uint32_t offset, uint16_t data)
 {
     ((shm_write_small *)d->my_shm)->address = offset;
     ((shm_write_small *)d->my_shm)->value = data;
+    gcc_barrier
     ((shm_write_small *)d->my_shm)->pingpong = DFPP_WRITE_WORD;
     d->waitWhile(DFPP_WRITE_WORD);
 }
@@ -452,6 +526,7 @@ void SHMProcess::writeByte (uint32_t offset, uint8_t data)
 {
     ((shm_write_small *)d->my_shm)->address = offset;
     ((shm_write_small *)d->my_shm)->value = data;
+    gcc_barrier
     ((shm_write_small *)d->my_shm)->pingpong = DFPP_WRITE_BYTE;
     d->waitWhile(DFPP_WRITE_BYTE);
 }
@@ -461,6 +536,7 @@ void SHMProcess::write (uint32_t offset, uint32_t size, const uint8_t *source)
     ((shm_write *)d->my_shm)->address = offset;
     ((shm_write *)d->my_shm)->length = size;
     memcpy(d->my_shm+sizeof(shm_write),source, size);
+    gcc_barrier
     ((shm_write *)d->my_shm)->pingpong = DFPP_WRITE;
     d->waitWhile(DFPP_WRITE);
 }

library/DFProcessEnumerator-linux.cpp

@@ -110,14 +110,19 @@ ProcessEnumerator::ProcessEnumerator( string path_to_xml )
     d->meminfo = new MemInfoManager(path_to_xml);
 }
 
-
-ProcessEnumerator::~ProcessEnumerator()
+void ProcessEnumerator::purge()
 {
-    // delete all processes
     for(uint32_t i = 0;i < d->processes.size();i++)
     {
         delete d->processes[i];
     }
+    d->processes.clear();
+}
+
+ProcessEnumerator::~ProcessEnumerator()
+{
+    // delete all processes
+    purge();
     delete d->meminfo;
     delete d;
 }

library/DFProcessEnumerator-windows.cpp

@@ -115,14 +115,19 @@ ProcessEnumerator::ProcessEnumerator( string path_to_xml )
     d->meminfo = new MemInfoManager(path_to_xml);
 }
 
-
-ProcessEnumerator::~ProcessEnumerator()
+ProcessEnumerator::purge()
 {
-    // delete all processes
     for(uint32_t i = 0;i < d->processes.size();i++)
     {
         delete d->processes[i];
     }
+    d->processes.clear();
+}
+
+ProcessEnumerator::~ProcessEnumerator()
+{
+    // delete all processes
+    purge();
     delete d->meminfo;
     delete d;
 }

library/DFProcessEnumerator.h

@@ -48,6 +48,7 @@ namespace DFHack
         bool findProcessess();
         uint32_t size();
         Process * operator[](uint32_t index);
+        void purge(void);
     };
 }
 #endif // PROCESSMANAGER_H_INCLUDED

library/shmserver/df-hacked

@@ -0,0 +1,14 @@
+#!/bin/sh
+DF_DIR=$(dirname "$0")
+cd "${DF_DIR}"
+export SDL_DISABLE_LOCK_KEYS=1 # Work around for bug in Debian/Ubuntu SDL patch.
+#export SDL_VIDEO_CENTERED=1 # Centre the screen.  Messes up resizing.
+ldd dwarfort.exe | grep SDL_image | grep -qv "not found$"
+if [ $? -eq 0 ]; then
+ mkdir unused_libs
+ mv libs/libSDL* unused_libs/
+fi
+export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:"./libs" # Update library search path.
+export LD_PRELOAD="./libs/dfconnect.so" # Hack DF!
+./dwarfort.exe $* # Go, go, go! :)
+

library/shmserver/dfconnect.c

@@ -25,8 +25,6 @@ distribution.
 /**
  * This is the source for the DF <-> dfhack shm bridge
  */
-#define _GNU_SOURCE
-
 #include <stdio.h>
 #include <dlfcn.h>
 #include <stdint.h>
@@ -37,27 +35,77 @@ distribution.
 #include <sys/ipc.h>
 #include <unistd.h>
 #include "dfconnect.h"
+#include <sys/time.h>
+#include <time.h>
+#include <linux/futex.h>
+#include <sys/syscall.h>
+
+// a full memory barrier! better be safe than sorry.
+#define gcc_barrier asm volatile("" ::: "memory"); __sync_synchronize();
+
+/*
+ * wait for futex
+ * futex has to be aligned to 4 bytes
+ * futex has to be equal to val (returns EWOULDBLOCK otherwise)
+ * wait can be broken by arriving signals (returns EINTR)
+ * returns 0 when broken by futex_wake
+ */
+inline int futex_wait(int * futex, int val)
+{
+    return syscall(SYS_futex, futex, FUTEX_WAIT, val, 0, 0, 0);
+}
+/*
+ * wait for futex
+ * futex has to be aligned to 4 bytes
+ * futex has to be equal to val (returns EWOULDBLOCK otherwise)
+ * wait can be broken by arriving signals (returns EINTR)
+ * returns 0 when broken by futex_wake
+ * returns ETIMEDOUT on timeout
+ */
+inline int futex_wait_timed(int * futex, int val, const struct timespec *timeout)
+{
+    return syscall(SYS_futex, futex, FUTEX_WAIT, val, timeout, 0, 0);
+}
+/*
+ * wake up futex. returns number of waked processes
+ */
+inline int futex_wake(int * futex)
+{
+    return syscall(SYS_futex, futex, FUTEX_WAKE, 1, 0, 0, 0);
+}
+static timespec one_second = { 1,0 };
+static timespec five_second = { 5,0 };
+
 
 // ptr to the real functions
 static void (*_SDL_GL_SwapBuffers)(void) = 0;
 static void (*_SDL_Quit)(void) = 0;
 static int (*_SDL_Init)(uint32_t flags) = 0;
+static int (*_SDL_Flip)(void * some_ptr) = 0;
 // various crud
 int counter = 0;
 int errorstate = 0;
 char *shm;
 int shmid;
 
-static unsigned char * BigFat;
-
 void SHM_Init ( void )
 {
     // name for the segment
     key_t key = 123466;
-    BigFat = (unsigned char *) malloc(SHM_SIZE);
     
-    // create the segment
-    if ((shmid = shmget(key, SHM_SIZE, IPC_CREAT | 0600)) < 0)
+    // find previous segment, check if it's used by some processes. if it isn't, kill it with fire
+    if ((shmid = shmget(key, SHM_SIZE, 0600)) != -1)
+    {
+        shmid_ds descriptor;
+        shmctl(shmid, IPC_STAT, &descriptor);
+        if(descriptor.shm_nattch == 0)
+        {
+            shmctl(shmid,IPC_RMID,NULL);
+            fprintf(stderr,"dfhack: killed dangling resources from crashed DF.\n");
+        }
+    }
+    // create the segment, make sure only ww are really creating it
+    if ((shmid = shmget(key, SHM_SIZE, IPC_CREAT | IPC_EXCL | 0600)) < 0)
     {
         perror("shmget");
         errorstate = 1;
@@ -71,30 +119,40 @@ void SHM_Init ( void )
         errorstate = 1;
         return;
     }
+    gcc_barrier
     ((shm_cmd *)shm)->pingpong = DFPP_RUNNING; // make sure we don't stall or do crazy stuff
 }
 
 void SHM_Destroy ( void )
 {
-    // blah, I don't care
+    shmid_ds descriptor;
+    shmctl(shmid, IPC_STAT, &descriptor);
+    shmdt(shm);
+    while(descriptor.shm_nattch != 0)
+    {
+        shmctl(shmid, IPC_STAT, &descriptor);
+    }
+    shmctl(shmid,IPC_RMID,NULL);
+    fprintf(stderr,"dfhack: destroyed shared segment.\n");
 }
 
 void SHM_Act (void)
 {
-    struct shmid_ds descriptor;
-    uint32_t numwaits = 0;
     if(errorstate)
     {
         return;
     }
+    shmid_ds descriptor;
+    uint32_t numwaits = 0;
     uint32_t length;
     uint32_t address;
     check_again: // goto target!!!
     if(numwaits == 10000)
     {
-        shmctl(shmid, IPC_STAT, &descriptor); 
+        shmctl(shmid, IPC_STAT, &descriptor);
         if(descriptor.shm_nattch == 1)// other guy crashed
         {
+            gcc_barrier
             ((shm_cmd *)shm)->pingpong = DFPP_RUNNING;
             fprintf(stderr,"dfhack: Broke out of loop, other process disappeared.\n");
             return;
@@ -117,23 +175,26 @@ void SHM_Act (void)
             numwaits++;
             goto check_again;
         case DFPP_SUSPEND:
+            gcc_barrier
             ((shm_cmd *)shm)->pingpong = DFPP_SUSPENDED;
             goto check_again;
-            
+            /*
         case DFPP_BOUNCE:
             length = ((shm_bounce *)shm)->length;
             memcpy(BigFat,shm + sizeof(shm_bounce),length);
             memcpy(shm + sizeof(shm_ret_data),BigFat,length);
             ((shm_cmd *)shm)->pingpong = DFPP_RET_DATA;
             goto check_again;
-            
+            */
         case DFPP_PID:
             ((shm_retval *)shm)->value = getpid();
+            gcc_barrier
             ((shm_retval *)shm)->pingpong = DFPP_RET_PID;
             goto check_again;
             
         case DFPP_VERSION:
             ((shm_retval *)shm)->value = PINGPONG_VERSION;
+            gcc_barrier
             ((shm_retval *)shm)->pingpong = DFPP_RET_VERSION;
             goto check_again;
             
@@ -141,24 +202,28 @@ void SHM_Act (void)
             length = ((shm_read *)shm)->length;
             address = ((shm_read *)shm)->address;
             memcpy(shm + sizeof(shm_ret_data), (void *) address,length);
+            gcc_barrier
             ((shm_cmd *)shm)->pingpong = DFPP_RET_DATA;
             goto check_again;
             
         case DFPP_READ_DWORD:
             address = ((shm_read_small *)shm)->address;
             ((shm_retval *)shm)->value = *((uint32_t*) address);
+            gcc_barrier
             ((shm_retval *)shm)->pingpong = DFPP_RET_DWORD;
             goto check_again;
 
         case DFPP_READ_WORD:
             address = ((shm_read_small *)shm)->address;
             ((shm_retval *)shm)->value = *((uint16_t*) address);
+            gcc_barrier
             ((shm_retval *)shm)->pingpong = DFPP_RET_WORD;
             goto check_again;
             
         case DFPP_READ_BYTE:
             address = ((shm_read_small *)shm)->address;
             ((shm_retval *)shm)->value = *((uint8_t*) address);
+            gcc_barrier
             ((shm_retval *)shm)->pingpong = DFPP_RET_BYTE;
             goto check_again;
             
@@ -166,21 +231,25 @@ void SHM_Act (void)
             address = ((shm_write *)shm)->address;
             length = ((shm_write *)shm)->length;
             memcpy((void *)address, shm + sizeof(shm_write),length);
+            gcc_barrier
             ((shm_cmd *)shm)->pingpong = DFPP_SUSPENDED;
             goto check_again;
             
         case DFPP_WRITE_DWORD:
             (*(uint32_t*)((shm_write_small *)shm)->address) = ((shm_write_small *)shm)->value;
+            gcc_barrier
             ((shm_cmd *)shm)->pingpong = DFPP_SUSPENDED;
             goto check_again;
 
         case DFPP_WRITE_WORD:
             (*(uint16_t*)((shm_write_small *)shm)->address) = ((shm_write_small *)shm)->value;
+            gcc_barrier
             ((shm_cmd *)shm)->pingpong = DFPP_SUSPENDED;
             goto check_again;
         
         case DFPP_WRITE_BYTE:
             (*(uint8_t*)((shm_write_small *)shm)->address) = ((shm_write_small *)shm)->value;
+            gcc_barrier
             ((shm_cmd *)shm)->pingpong = DFPP_SUSPENDED;
             goto check_again;
             
@@ -191,12 +260,13 @@ void SHM_Act (void)
             
         default:
             ((shm_retval *)shm)->value = DFEE_INVALID_COMMAND;
+            gcc_barrier
             ((shm_retval *)shm)->pingpong = DFPP_SV_ERROR;
             break;
     }
 }
 
-// hook - called every tick
+// hook - called every tick in OpenGL mode of DF
 extern "C" void SDL_GL_SwapBuffers(void)
 {
     if(_SDL_GL_SwapBuffers)
@@ -210,6 +280,20 @@ extern "C" void SDL_GL_SwapBuffers(void)
     }
 }
 
+// hook - called every tick in the 2D mode of DF
+extern "C" int SDL_Flip(void * some_ptr)
+{
+    if(_SDL_Flip)
+    {
+        if(((shm_cmd *)shm)->pingpong != DFPP_RUNNING)
+        {
+            SHM_Act();
+        }
+        counter ++;
+        return _SDL_Flip(some_ptr);
+    }
+}
+
 // hook - called at program exit
 extern "C" void SDL_Quit(void)
 {
@@ -217,7 +301,8 @@ extern "C" void SDL_Quit(void)
     {
         _SDL_Quit();
     }
-    fprintf(stderr,"dfhack: DF called SwapBuffers %d times, lol\n", counter);
+    fprintf(stderr,"dfhack: DF called SwapBuffers %d times\n", counter);
+    SHM_Destroy();
 }
 
 // hook - called at program start, initialize some stuffs we'll use later
@@ -226,6 +311,7 @@ extern "C" int SDL_Init(uint32_t flags)
     // find real functions
     _SDL_GL_SwapBuffers = (void (*)( void )) dlsym(RTLD_NEXT, "SDL_GL_SwapBuffers");
     _SDL_Init = (int (*)( uint32_t )) dlsym(RTLD_NEXT, "SDL_Init");
+    _SDL_Flip = (int (*)( void * )) dlsym(RTLD_NEXT, "SDL_Flip");
     _SDL_Quit = (void (*)( void )) dlsym(RTLD_NEXT, "SDL_Quit");
 
     // check if we got them

library/shmserver/dfconnect.h

@@ -12,6 +12,14 @@
     * end - sent to DF for breaking out of the wait 
 */
 
+enum DF_SHM_ERRORSTATE
+{
+    SHM_OK, // all OK
+    SHM_CANT_GET_SHM, // getting the SHM ID failed for some reason
+    SHM_CANT_ATTACH, // we can't attach the shm for some reason
+    SHM_SECOND_DF // we are a second DF process, can't use SHM at all
+};
+
 enum DF_PINGPONG
 {
     DFPP_RUNNING = 0, // no command, normal server execution

library/shmserver/readme.txt

@@ -9,3 +9,6 @@ export LD_PRELOAD="./libs/dfconnect.so" # Hack DF!
 save and run the script!
 
 Has to be compiled for 32bit arch, otherwise the library isn't recognised. Client can be any arch.
+
+Precompiled dfconnect library is made available. dfconnect.so goes in DF/libs, df-hacked script goes in DF/
+Run ./df-hacked to use the shared memory API