syscall_emul: add retry flag to SyscallReturn

This hook allows blocking emulated system calls to indicate
that they would block, but return control to the simulator
so that the simulation does not hang.  The actual retry
functionality requires additional support, to be provided
in a future changeset.

diff --git a/src/sim/syscall_emul.cc b/src/sim/syscall_emul.cc
index d8df891dde4a5c223953b1b5cc9974d6eb5f2db0..cb592e33812a2b538700194c0b790864258de488 100644 (file)
--- a/src/sim/syscall_emul.cc
+++ b/src/sim/syscall_emul.cc
@@ -71,10 +71,15 @@ SyscallDesc::doSyscall(int callnum, LiveProcess *process, ThreadContext *tc)
 
     SyscallReturn retval = (*funcPtr)(this, callnum, process, tc);
 
-    DPRINTFR(SyscallVerbose, "%d: %s: syscall %s returns %d\n",
-             curTick(), tc->getCpuPtr()->name(), name, retval.encodedValue());
+    if (retval.needsRetry()) {
+        DPRINTFS(SyscallVerbose, tc->getCpuPtr(), "syscall %s needs retry\n",
+                 name);
+    } else {
+        DPRINTFS(SyscallVerbose, tc->getCpuPtr(), "syscall %s returns %d\n",
+                 name, retval.encodedValue());
+    }
 
-    if (!(flags & SyscallDesc::SuppressReturnValue))
+    if (!(flags & SyscallDesc::SuppressReturnValue) && !retval.needsRetry())
         process->setSyscallReturn(tc, retval);
 }
 

diff --git a/src/sim/syscallreturn.hh b/src/sim/syscallreturn.hh
index 547d7661076cd5cb219cc4501d503b5648fb050a..fdd740775edb6144bd45839739002d907db834d0 100644 (file)
--- a/src/sim/syscallreturn.hh
+++ b/src/sim/syscallreturn.hh
@@ -64,9 +64,17 @@ class SyscallReturn
     /// value is expected, e.g., as the return value from a system
     /// call emulation function ('return 0;' or 'return -EFAULT;').
     SyscallReturn(int64_t v)
-        : value(v)
+        : value(v), retryFlag(false)
     {}
 
+    /// Pseudo-constructor to create an instance with the retry flag set.
+    static SyscallReturn retry()
+    {
+        SyscallReturn s(0);
+        s.retryFlag = true;
+        return s;
+    }
+
     ~SyscallReturn() {}
 
     /// Was the system call successful?
@@ -75,6 +83,9 @@ class SyscallReturn
         return (value >= 0 || value <= -4096);
     }
 
+    /// Does the syscall need to be retried?
+    bool needsRetry() const { return retryFlag; }
+
     /// The return value
     int64_t returnValue() const
     {
@@ -98,6 +109,8 @@ class SyscallReturn
   private:
 
     int64_t value;
+
+    bool retryFlag;
 };
 
 #endif