syscalls: fix latent brk/obreak bug.

Bogus calls to ChunkGenerator with negative size were triggering
a new assertion that was added there.
Also did a little renaming and cleanup in the process.

2 files changed, 15 insertions, 9 deletions

diff --git a/src/sim/syscall_emul.cc b/src/sim/syscall_emul.cc
index e0e703815..fb6af0b0c 100644
--- a/src/sim/syscall_emul.cc
+++ b/src/sim/syscall_emul.cc
@@ -107,21 +107,27 @@ getpagesizeFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 
 
 SyscallReturn
-obreakFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
+brkFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
-    Addr junk;
-
     // change brk addr to first arg
     Addr new_brk = tc->getSyscallArg(0);
-    if (new_brk != 0) {
+
+    // in Linux at least, brk(0) returns the current break value
+    // (note that the syscall and the glibc function have different behavior)
+    if (new_brk == 0)
+        return p->brk_point;
+
+    if (new_brk > p->brk_point) {
+        // might need to allocate some new pages
         for (ChunkGenerator gen(p->brk_point, new_brk - p->brk_point,
                                 VMPageSize); !gen.done(); gen.next()) {
-            if (!p->pTable->translate(gen.addr(), junk))
+            if (!p->pTable->translate(gen.addr()))
                 p->pTable->allocate(roundDown(gen.addr(), VMPageSize),
                                     VMPageSize);
         }
-        p->brk_point = new_brk;
     }
+
+    p->brk_point = new_brk;
     DPRINTF(SyscallVerbose, "Break Point changed to: %#X\n", p->brk_point);
     return p->brk_point;
 }
diff --git a/src/sim/syscall_emul.hh b/src/sim/syscall_emul.hh
index 2e8071196..57403ab27 100644
--- a/src/sim/syscall_emul.hh
+++ b/src/sim/syscall_emul.hh
@@ -191,9 +191,9 @@ SyscallReturn exitFunc(SyscallDesc *desc, int num,
 SyscallReturn getpagesizeFunc(SyscallDesc *desc, int num,
                               LiveProcess *p, ThreadContext *tc);
 
-/// Target obreak() handler: set brk address.
-SyscallReturn obreakFunc(SyscallDesc *desc, int num,
-                         LiveProcess *p, ThreadContext *tc);
+/// Target brk() handler: set brk address.
+SyscallReturn brkFunc(SyscallDesc *desc, int num,
+                      LiveProcess *p, ThreadContext *tc);
 
 /// Target close() handler.
 SyscallReturn closeFunc(SyscallDesc *desc, int num,