syscall_emul: file descriptor interface changes

This patch gets rid of unused Process::dup_fd method and does minor
refactoring in the process class files.  The file descriptor max has been
changed to be the number of file descriptors since this clarifies the loop
boundary condition and cleans up the code a bit.  The fd_map field has been
altered to be dynamically allocated as opposed to being an array; the
intention here is to build on this is subsequent patches to allow processes
to share their file descriptors with the clone system call.

3 files changed, 40 insertions, 50 deletions

diff --git a/src/sim/process.cc b/src/sim/process.cc
index 198f05adf..8aca849a6 100644
--- a/src/sim/process.cc
+++ b/src/sim/process.cc
@@ -115,7 +115,8 @@ Process::Process(ProcessParams * params)
         static_cast<PageTableBase *>(new ArchPageTable(name(), M5_pid, system)) :
         static_cast<PageTableBase *>(new FuncPageTable(name(), M5_pid)) ),
       initVirtMem(system->getSystemPort(), this,
-                  SETranslatingPortProxy::Always)
+                  SETranslatingPortProxy::Always),
+      fd_map(new FdMap[NUM_FDS])
 {
     string in = params->input;
     string out = params->output;
@@ -175,7 +176,7 @@ Process::Process(ProcessParams * params)
 
 
     // mark remaining fds as free
-    for (int i = 3; i <= MAX_FD; ++i) {
+    for (int i = 3; i < NUM_FDS; ++i) {
         fdo = &fd_map[i];
         fdo->fd = -1;
     }
@@ -200,6 +201,7 @@ Process::regStats()
 //
 // static helper functions
 //
+
 int
 Process::openInputFile(const string &filename)
 {
@@ -232,14 +234,10 @@ Process::openOutputFile(const string &filename)
 ThreadContext *
 Process::findFreeContext()
 {
-    int size = contextIds.size();
-    ThreadContext *tc;
-    for (int i = 0; i < size; ++i) {
-        tc = system->getThreadContext(contextIds[i]);
-        if (tc->status() == ThreadContext::Halted) {
-            // inactive context, free to use
+    for (int id : contextIds) {
+        ThreadContext *tc = system->getThreadContext(id);
+        if (tc->status() == ThreadContext::Halted)
             return tc;
-        }
     }
     return NULL;
 }
@@ -266,19 +264,6 @@ Process::drain()
     return DrainState::Drained;
 }
 
-// map simulator fd sim_fd to target fd tgt_fd
-void
-Process::dup_fd(int sim_fd, int tgt_fd)
-{
-    if (tgt_fd < 0 || tgt_fd > MAX_FD)
-        panic("Process::dup_fd tried to dup past MAX_FD (%d)", tgt_fd);
-
-    Process::FdMap *fdo = &fd_map[tgt_fd];
-    fdo->fd = sim_fd;
-}
-
-
-// generate new target fd for sim_fd
 int
 Process::alloc_fd(int sim_fd, const string& filename, int flags, int mode,
                   bool pipe)
@@ -288,7 +273,7 @@ Process::alloc_fd(int sim_fd, const string& filename, int flags, int mode,
         return -1;
 
     // find first free target fd
-    for (int free_fd = 0; free_fd <= MAX_FD; ++free_fd) {
+    for (int free_fd = 0; free_fd < NUM_FDS; ++free_fd) {
         Process::FdMap *fdo = &fd_map[free_fd];
         if (fdo->fd == -1 && fdo->driver == NULL) {
             fdo->fd = sim_fd;
@@ -305,14 +290,11 @@ Process::alloc_fd(int sim_fd, const string& filename, int flags, int mode,
     panic("Process::alloc_fd: out of file descriptors!");
 }
 
-
-// free target fd (e.g., after close)
 void
-Process::free_fd(int tgt_fd)
+Process::free_fdmap_entry(int tgt_fd)
 {
     Process::FdMap *fdo = &fd_map[tgt_fd];
-    if (fdo->fd == -1)
-        warn("Process::free_fd: request to free unused fd %d", tgt_fd);
+    assert(fd_map[tgt_fd].fd > -1);
 
     fdo->fd = -1;
     fdo->filename = "NULL";
@@ -324,26 +306,30 @@ Process::free_fd(int tgt_fd)
     fdo->driver = NULL;
 }
 
-
-// look up simulator fd for given target fd
 int
 Process::sim_fd(int tgt_fd)
 {
-    if (tgt_fd < 0 || tgt_fd > MAX_FD)
-        return -1;
-
-    return fd_map[tgt_fd].fd;
+    FdMap *obj = sim_fd_obj(tgt_fd);
+    return obj ? obj->fd : -1;
 }
 
 Process::FdMap *
 Process::sim_fd_obj(int tgt_fd)
 {
-    if (tgt_fd < 0 || tgt_fd > MAX_FD)
+    if (tgt_fd < 0 || tgt_fd >= NUM_FDS)
         return NULL;
-
     return &fd_map[tgt_fd];
 }
 
+int
+Process::tgt_fd(int sim_fd)
+{
+    for (int index = 0; index < NUM_FDS; ++index)
+        if (fd_map[index].fd == sim_fd)
+            return index;
+    return -1;
+}
+
 void
 Process::allocateMem(Addr vaddr, int64_t size, bool clobber)
 {
@@ -433,7 +419,7 @@ Process::fix_file_offsets()
     fdo_stderr->fd = stderr_fd;
 
 
-    for (int free_fd = 3; free_fd <= MAX_FD; ++free_fd) {
+    for (int free_fd = 3; free_fd < NUM_FDS; ++free_fd) {
         Process::FdMap *fdo = &fd_map[free_fd];
         if (fdo->fd != -1) {
             if (fdo->isPipe){
@@ -476,7 +462,7 @@ Process::fix_file_offsets()
 void
 Process::find_file_offsets()
 {
-    for (int free_fd = 0; free_fd <= MAX_FD; ++free_fd) {
+    for (int free_fd = 0; free_fd < NUM_FDS; ++free_fd) {
         Process::FdMap *fdo = &fd_map[free_fd];
         if (fdo->fd != -1) {
             fdo->fileOffset = lseek(fdo->fd, 0, SEEK_CUR);
@@ -529,7 +515,7 @@ Process::serialize(CheckpointOut &cp) const
     SERIALIZE_SCALAR(nxm_start);
     SERIALIZE_SCALAR(nxm_end);
     pTable->serialize(cp);
-    for (int x = 0; x <= MAX_FD; x++) {
+    for (int x = 0; x < NUM_FDS; x++) {
         fd_map[x].serializeSection(cp, csprintf("FdMap%d", x));
     }
     SERIALIZE_SCALAR(M5_pid);
@@ -549,7 +535,7 @@ Process::unserialize(CheckpointIn &cp)
     UNSERIALIZE_SCALAR(nxm_start);
     UNSERIALIZE_SCALAR(nxm_end);
     pTable->unserialize(cp);
-    for (int x = 0; x <= MAX_FD; x++) {
+    for (int x = 0; x < NUM_FDS; x++) {
         fd_map[x].unserializeSection(cp, csprintf("FdMap%d", x));
     }
     fix_file_offsets();
@@ -557,7 +543,7 @@ Process::unserialize(CheckpointIn &cp)
     // The above returns a bool so that you could do something if you don't
     // find the param in the checkpoint if you wanted to, like set a default
     // but in this case we'll just stick with the instantianted value if not
-    // found.   
+    // found.
 }
 
 
diff --git a/src/sim/process.hh b/src/sim/process.hh
index cdb3826ff..fe41a35e4 100644
--- a/src/sim/process.hh
+++ b/src/sim/process.hh
@@ -161,10 +161,10 @@ class Process : public SimObject
     SETranslatingPortProxy initVirtMem;
 
   private:
-    // file descriptor remapping support
-    static const int MAX_FD = 256;    // max legal fd value
-    FdMap fd_map[MAX_FD+1];
+    static const int NUM_FDS = 1024;
 
+    // File descriptor remapping support.
+    FdMap *fd_map;
 
   public:
     // static helper functions to generate file descriptors for constructor
@@ -187,15 +187,12 @@ class Process : public SimObject
     // provide program name for debug messages
     virtual const char *progName() const { return "<unknown>"; }
 
-    // map simulator fd sim_fd to target fd tgt_fd
-    void dup_fd(int sim_fd, int tgt_fd);
-
     // generate new target fd for sim_fd
     int alloc_fd(int sim_fd, const std::string& filename, int flags, int mode,
                  bool pipe);
 
-    // free target fd (e.g., after close)
-    void free_fd(int tgt_fd);
+    // disassociate target fd with simulator fd and cleanup subsidiary fields
+    void free_fdmap_entry(int tgt_fd);
 
     // look up simulator fd for given target fd
     int sim_fd(int tgt_fd);
@@ -203,6 +200,13 @@ class Process : public SimObject
     // look up simulator fd_map object for a given target fd
     FdMap *sim_fd_obj(int tgt_fd);
 
+    // look up target fd for given host fd
+    // Assumes a 1:1 mapping between target file descriptor and host file
+    // descriptor. Given the current API, this must be true given that it's
+    // not possible to map multiple target file descriptors to the same host
+    // file descriptor
+    int tgt_fd(int sim_fd);
+
     // fix all offsets for currently open files and save them
     void fix_file_offsets();
 
diff --git a/src/sim/syscall_emul.cc b/src/sim/syscall_emul.cc
index b1d3edde4..00506125e 100644
--- a/src/sim/syscall_emul.cc
+++ b/src/sim/syscall_emul.cc
@@ -216,7 +216,7 @@ closeFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
     if (sim_fd > 2)
         status = close(sim_fd);
     if (status >= 0)
-        p->free_fd(target_fd);
+        p->free_fdmap_entry(target_fd);
     return status;
 }