2 files changed, 110 insertions, 5 deletions

diff --git a/sim/system.cc b/sim/system.cc
index 3da92c447..e67cae333 100644
--- a/sim/system.cc
+++ b/sim/system.cc
@@ -124,9 +124,7 @@ System::System(Params *p)
 
     Addr addr = 0;
 #ifdef DEBUG
-    consolePanicEvent = new BreakPCEvent(&pcEventQueue, "console panic");
-    if (consoleSymtab->findAddress("panic", addr))
-        consolePanicEvent->schedule(addr);
+    consolePanicEvent = addConsoleFuncEvent<BreakPCEvent>("panic");
 #endif
 
     /**
@@ -180,6 +178,65 @@ System::~System()
 #endif
 }
 
+
+/**
+ * This function fixes up addresses that are used to match PCs for
+ * hooking simulator events on to target function executions.
+ *
+ * Alpha binaries may have multiple global offset table (GOT)
+ * sections.  A function that uses the GOT starts with a
+ * two-instruction prolog which sets the global pointer (gp == r29) to
+ * the appropriate GOT section.  The proper gp value is calculated
+ * based on the function address, which must be passed by the caller
+ * in the procedure value register (pv aka t12 == r27).  This sequence
+ * looks like the following:
+ *
+ *			opcode Ra Rb offset
+ *	ldah gp,X(pv)     09   29 27   X
+ *	lda  gp,Y(gp)     08   29 29   Y
+ *
+ * for some constant offsets X and Y.  The catch is that the linker
+ * (or maybe even the compiler, I'm not sure) may recognize that the
+ * caller and callee are using the same GOT section, making this
+ * prolog redundant, and modify the call target to skip these
+ * instructions.  If we check for execution of the first instruction
+ * of a function (the one the symbol points to) to detect when to skip
+ * it, we'll miss all these modified calls.  It might work to
+ * unconditionally check for the third instruction, but not all
+ * functions have this prolog, and there's some chance that those
+ * first two instructions could have undesired consequences.  So we do
+ * the Right Thing and pattern-match the first two instructions of the
+ * function to decide where to patch.
+ *
+ * Eventually this code should be moved into an ISA-specific file.
+ */
+Addr
+System::fixFuncEventAddr(Addr addr)
+{
+    // mask for just the opcode, Ra, and Rb fields (not the offset)
+    const uint32_t inst_mask = 0xffff0000;
+    // ldah gp,X(pv): opcode 9, Ra = 29, Rb = 27
+    const uint32_t gp_ldah_pattern = (9 << 26) | (29 << 21) | (27 << 16);
+    // lda  gp,Y(gp): opcode 8, Ra = 29, rb = 29
+    const uint32_t gp_lda_pattern  = (8 << 26) | (29 << 21) | (29 << 16);
+    // instruction size
+    const int sz = sizeof(uint32_t);
+
+    Addr paddr = vtophys(physmem, addr);
+    uint32_t i1 = *(uint32_t *)physmem->dma_addr(paddr, sz);
+    uint32_t i2 = *(uint32_t *)physmem->dma_addr(paddr+sz, sz);
+
+    if ((i1 & inst_mask) == gp_ldah_pattern &&
+        (i2 & inst_mask) == gp_lda_pattern) {
+        Addr new_addr = addr + 2*sz;
+        DPRINTF(Loader, "fixFuncEventAddr: %p -> %p", addr, new_addr);
+        return new_addr;
+    } else {
+        return addr;
+    }
+}
+
+
 void
 System::setAlphaAccess(Addr access)
 {
@@ -197,6 +254,7 @@ System::setAlphaAccess(Addr access)
         panic("could not find m5AlphaAccess\n");
 }
 
+
 bool
 System::breakpoint()
 {
diff --git a/sim/system.hh b/sim/system.hh
index 870805e4c..c4ecc9458 100644
--- a/sim/system.hh
+++ b/sim/system.hh
@@ -33,6 +33,7 @@
 #include <vector>
 
 #include "base/statistics.hh"
+#include "base/loader/symtab.hh"
 #include "cpu/pc_event.hh"
 #include "kern/system_events.hh"
 #include "sim/sim_object.hh"
@@ -45,7 +46,6 @@ class ObjectFile;
 class PhysicalMemory;
 class Platform;
 class RemoteGDB;
-class SymbolTable;
 namespace Kernel { class Binning; }
 
 class System : public SimObject
@@ -68,7 +68,7 @@ class System : public SimObject
         return numcpus;
     }
 
-    /** kernel Symbol table */
+    /** kernel symbol table */
     SymbolTable *kernelSymtab;
 
     /** console symbol table */
@@ -102,6 +102,53 @@ class System : public SimObject
     BreakPCEvent *consolePanicEvent;
 #endif
 
+  protected:
+
+    /**
+     * Fix up an address used to match PCs for hooking simulator
+     * events on to target function executions.  See comment in
+     * system.cc for details.
+     */
+    Addr fixFuncEventAddr(Addr addr);
+
+    /**
+     * Add a function-based event to the given function, to be looked
+     * up in the specified symbol table.
+     */
+    template <class T>
+    T *System::addFuncEvent(SymbolTable *symtab, const char *lbl)
+    {
+        Addr addr;
+
+        if (symtab->findAddress(lbl, addr)) {
+            T *ev = new T(&pcEventQueue, lbl, fixFuncEventAddr(addr));
+            return ev;
+        }
+
+        return NULL;
+    }
+
+    /** Add a function-based event to kernel code. */
+    template <class T>
+    T *System::addKernelFuncEvent(const char *lbl)
+    {
+        return addFuncEvent<T>(kernelSymtab, lbl);
+    }
+
+    /** Add a function-based event to PALcode. */
+    template <class T>
+    T *System::addPalFuncEvent(const char *lbl)
+    {
+        return addFuncEvent<T>(palSymtab, lbl);
+    }
+
+    /** Add a function-based event to the console code. */
+    template <class T>
+    T *System::addConsoleFuncEvent(const char *lbl)
+    {
+        return addFuncEvent<T>(consoleSymtab, lbl);
+    }
+
   public:
     std::vector<RemoteGDB *> remoteGDB;
     std::vector<GDBListener *> gdbListen;