Stack: Tidy up some comments, a warning, and make stack extension consistent.

Do some minor cleanup of some recently added comments, a warning, and change
other instances of stack extension to be like what's now being done for x86.

7 files changed, 22 insertions, 31 deletions

diff --git a/src/arch/alpha/faults.cc b/src/arch/alpha/faults.cc
index b6a0d965e..c66c6f8ab 100644
--- a/src/arch/alpha/faults.cc
+++ b/src/arch/alpha/faults.cc
@@ -201,8 +201,8 @@ NDtbMissFault::invoke(ThreadContext *tc, StaticInstPtr inst)
     TlbEntry entry;
     bool success = p->pTable->lookup(vaddr, entry);
     if (!success) {
-        p->checkAndAllocNextPage(vaddr);
-        success = p->pTable->lookup(vaddr, entry);
+        if (p->fixupStackFault(vaddr))
+            success = p->pTable->lookup(vaddr, entry);
     }
     if (!success) {
         panic("Tried to access unmapped address %#x.\n", (Addr)vaddr);
diff --git a/src/arch/sparc/faults.cc b/src/arch/sparc/faults.cc
index 814a33bd3..01d57e627 100644
--- a/src/arch/sparc/faults.cc
+++ b/src/arch/sparc/faults.cc
@@ -643,8 +643,8 @@ FastDataAccessMMUMiss::invoke(ThreadContext *tc, StaticInstPtr inst)
     TlbEntry entry;
     bool success = p->pTable->lookup(vaddr, entry);
     if (!success) {
-        p->checkAndAllocNextPage(vaddr);
-        success = p->pTable->lookup(vaddr, entry);
+        if (p->fixupStackFault(vaddr))
+            success = p->pTable->lookup(vaddr, entry);
     }
     if (!success) {
         panic("Tried to access unmapped address %#x.\n", vaddr);
diff --git a/src/arch/x86/tlb.cc b/src/arch/x86/tlb.cc
index 9ba20f8d7..9d02a00c7 100644
--- a/src/arch/x86/tlb.cc
+++ b/src/arch/x86/tlb.cc
@@ -619,22 +619,11 @@ TLB::translate(RequestPtr req, ThreadContext *tc, Translation *translation,
                 TlbEntry newEntry;
                 bool success = p->pTable->lookup(vaddr, newEntry);
                 if (!success && mode != Execute) {
-                    // This may fail because for some reason the requested
-                    // address is not allocatable on the stack.  If it's a stack
-                    // address, then it's because the address fell outside of
-                    // max stack range and user should increase max size of
-                    // stack.  Otherwise, it could be a random address that was
-                    // not in the page table and not on the stack.  Either way,
-                    // you'll end up with a page fault.
-                    if (p->checkAndAllocNextPage(vaddr))
-                        // Might as well not check this if you failed to
-                        // allocate.  Partially nested this just so code
-                        // maintainers can understand this is a separate and
-                        // necessary step not sufficient just by reading return
-                        // value of checkAndAlloc call because there is a side
-                        // effect.  This call will populate (it's called by 
-                        // reference).
+                    // Check if we just need to grow the stack.
+                    if (p->fixupStackFault(vaddr)) {
+                        // If we did, lookup the entry for the new page.
                         success = p->pTable->lookup(vaddr, newEntry);
+                    }
                 }
                 if (!success) {
                     return new PageFault(vaddr, true, mode, true, false);
diff --git a/src/mem/translating_port.cc b/src/mem/translating_port.cc
index 210f9beb3..80c68c6bd 100644
--- a/src/mem/translating_port.cc
+++ b/src/mem/translating_port.cc
@@ -90,7 +90,7 @@ TranslatingPort::tryWriteBlob(Addr addr, uint8_t *p, int size)
                                  VMPageSize);
             } else if (allocating == NextPage) {
                 // check if we've accessed the next page on the stack
-                if (!process->checkAndAllocNextPage(gen.addr()))
+                if (!process->fixupStackFault(gen.addr()))
                     panic("Page table fault when accessing virtual address %#x "
                             "during functional write\n", gen.addr());
             } else {
diff --git a/src/sim/faults.cc b/src/sim/faults.cc
index 8e9b8e094..3f1369bcc 100644
--- a/src/sim/faults.cc
+++ b/src/sim/faults.cc
@@ -61,7 +61,7 @@ void GenericPageTableFault::invoke(ThreadContext *tc, StaticInstPtr inst)
 {
     Process *p = tc->getProcessPtr();
 
-    if (!p->checkAndAllocNextPage(vaddr))
+    if (!p->fixupStackFault(vaddr))
         panic("Page table fault when accessing virtual address %#x\n", vaddr);
 
 }
diff --git a/src/sim/process.cc b/src/sim/process.cc
index bec33c70b..62b9b7002 100644
--- a/src/sim/process.cc
+++ b/src/sim/process.cc
@@ -329,29 +329,31 @@ Process::sim_fd_obj(int tgt_fd)
 }
 
 bool
-Process::checkAndAllocNextPage(Addr vaddr)
+Process::fixupStackFault(Addr vaddr)
 {
-    // if this is an initial write we might not have
+    // Check if this is already on the stack and there's just no page there
+    // yet.
     if (vaddr >= stack_min && vaddr < stack_base) {
         pTable->allocate(roundDown(vaddr, VMPageSize), VMPageSize);
         return true;
     }
 
-    // We've accessed the next page of the stack, so extend the stack
-    // to cover it.
+    // We've accessed the next page of the stack, so extend it to include
+    // this address.
     if (vaddr < stack_min && vaddr >= stack_base - max_stack_size) {
         while (vaddr < stack_min) {
             stack_min -= TheISA::PageBytes;
-            if(stack_base - stack_min > max_stack_size)
+            if (stack_base - stack_min > max_stack_size)
                 fatal("Maximum stack size exceeded\n");
-            if(stack_base - stack_min > 8*1024*1024)
+            if (stack_base - stack_min > 8 * 1024 * 1024)
                 fatal("Over max stack size for one thread\n");
             pTable->allocate(stack_min, TheISA::PageBytes);
             inform("Increasing stack size by one page.");
         };
         return true;
     }
-    warn("Not increasing stack: requested vaddr is outside of stack range.");
+    warn("Not extending stack: address %#x isn't at the end of the stack.",
+        vaddr);
     return false;
 }
 
diff --git a/src/sim/process.hh b/src/sim/process.hh
index 94f6d1800..d48b1b463 100644
--- a/src/sim/process.hh
+++ b/src/sim/process.hh
@@ -212,9 +212,9 @@ class Process : public SimObject
 
     virtual void syscall(int64_t callnum, ThreadContext *tc) = 0;
 
-    // check if the this addr is on the next available page and allocate it
-    // if it's not we'll panic
-    bool checkAndAllocNextPage(Addr vaddr);
+    /// Attempt to fix up a fault at vaddr by allocating a page on the stack.
+    /// @return Whether the fault has been fixed.
+    bool fixupStackFault(Addr vaddr);
 
     void serialize(std::ostream &os);
     void unserialize(Checkpoint *cp, const std::string &section);