Syscalls: Make system calls access arguments like a stack, not an array.

When accessing arguments for a syscall, the position of an argument depends on
the policies of the ISA, how much space preceding arguments took up, and the
"alignment" of the index for this particular argument into the number of
possible storate locations. This change adjusts getSyscallArg to take its
index parameter by reference instead of value and to adjust it to point to the
possible location of the next argument on the stack, basically just after the
current one. This way, the rules for the new argument can be applied locally
without knowing about other arguments since those have already been taken into
account implicitly.

All system calls have also been changed to reflect the new interface. In a
number of cases this made the implementation clearer since it encourages
arguments to be collected in one place in order and then used as necessary
later, as opposed to scattering them throughout the function or using them in
place in long expressions. It also discourages using getSyscallArg over and
over to retrieve the same value when a temporary would do the job.

1 files changed, 94 insertions, 59 deletions

diff --git a/src/sim/syscall_emul.cc b/src/sim/syscall_emul.cc
index 13ad04311..d25f7b9fa 100644
--- a/src/sim/syscall_emul.cc
+++ b/src/sim/syscall_emul.cc
@@ -52,11 +52,14 @@ using namespace TheISA;
 void
 SyscallDesc::doSyscall(int callnum, LiveProcess *process, ThreadContext *tc)
 {
+    int index = 0;
     DPRINTFR(SyscallVerbose,
              "%d: %s: syscall %s called w/arguments %d,%d,%d,%d\n",
              curTick, tc->getCpuPtr()->name(), name,
-             process->getSyscallArg(tc, 0), process->getSyscallArg(tc, 1),
-             process->getSyscallArg(tc, 2), process->getSyscallArg(tc, 3));
+             process->getSyscallArg(tc, index),
+             process->getSyscallArg(tc, index),
+             process->getSyscallArg(tc, index),
+             process->getSyscallArg(tc, index));
 
     SyscallReturn retval = (*funcPtr)(this, callnum, process, tc);
 
@@ -82,8 +85,9 @@ SyscallReturn
 ignoreFunc(SyscallDesc *desc, int callnum, LiveProcess *process,
            ThreadContext *tc)
 {
+    int index = 0;
     warn("ignoring syscall %s(%d, %d, ...)", desc->name,
-         process->getSyscallArg(tc, 0), process->getSyscallArg(tc, 1));
+         process->getSyscallArg(tc, index), process->getSyscallArg(tc, index));
 
     return 0;
 }
@@ -95,8 +99,9 @@ exitFunc(SyscallDesc *desc, int callnum, LiveProcess *process,
 {
     if (process->system->numRunningContexts() == 1) {
         // Last running context... exit simulator
+        int index = 0;
         exitSimLoop("target called exit()",
-                    process->getSyscallArg(tc, 0) & 0xff);
+                    process->getSyscallArg(tc, index) & 0xff);
     } else {
         // other running threads... just halt this one
         tc->halt();
@@ -112,8 +117,9 @@ exitGroupFunc(SyscallDesc *desc, int callnum, LiveProcess *process,
 {
     // really should just halt all thread contexts belonging to this
     // process in case there's another process running...
+    int index = 0;
     exitSimLoop("target called exit()",
-                process->getSyscallArg(tc, 0) & 0xff);
+                process->getSyscallArg(tc, index) & 0xff);
 
     return 1;
 }
@@ -130,7 +136,8 @@ SyscallReturn
 brkFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
     // change brk addr to first arg
-    Addr new_brk = p->getSyscallArg(tc, 0);
+    int index = 0;
+    Addr new_brk = p->getSyscallArg(tc, index);
 
     // in Linux at least, brk(0) returns the current break value
     // (note that the syscall and the glibc function have different behavior)
@@ -174,7 +181,8 @@ brkFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 SyscallReturn
 closeFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
-    int target_fd = p->getSyscallArg(tc, 0);
+    int index = 0;
+    int target_fd = p->getSyscallArg(tc, index);
     int status = close(p->sim_fd(target_fd));
     if (status >= 0)
         p->free_fd(target_fd);
@@ -185,9 +193,11 @@ closeFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 SyscallReturn
 readFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
-    int fd = p->sim_fd(p->getSyscallArg(tc, 0));
-    int nbytes = p->getSyscallArg(tc, 2);
-    BufferArg bufArg(p->getSyscallArg(tc, 1), nbytes);
+    int index = 0;
+    int fd = p->sim_fd(p->getSyscallArg(tc, index));
+    Addr bufPtr = p->getSyscallArg(tc, index);
+    int nbytes = p->getSyscallArg(tc, index);
+    BufferArg bufArg(bufPtr, nbytes);
 
     int bytes_read = read(fd, bufArg.bufferPtr(), nbytes);
 
@@ -200,9 +210,11 @@ readFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 SyscallReturn
 writeFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
-    int fd = p->sim_fd(p->getSyscallArg(tc, 0));
-    int nbytes = p->getSyscallArg(tc, 2);
-    BufferArg bufArg(p->getSyscallArg(tc, 1), nbytes);
+    int index = 0;
+    int fd = p->sim_fd(p->getSyscallArg(tc, index));
+    Addr bufPtr = p->getSyscallArg(tc, index);
+    int nbytes = p->getSyscallArg(tc, index);
+    BufferArg bufArg(bufPtr, nbytes);
 
     bufArg.copyIn(tc->getMemPort());
 
@@ -217,9 +229,10 @@ writeFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 SyscallReturn
 lseekFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
-    int fd = p->sim_fd(p->getSyscallArg(tc, 0));
-    uint64_t offs = p->getSyscallArg(tc, 1);
-    int whence = p->getSyscallArg(tc, 2);
+    int index = 0;
+    int fd = p->sim_fd(p->getSyscallArg(tc, index));
+    uint64_t offs = p->getSyscallArg(tc, index);
+    int whence = p->getSyscallArg(tc, index);
 
     off_t result = lseek(fd, offs, whence);
 
@@ -230,11 +243,12 @@ lseekFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 SyscallReturn
 _llseekFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
-    int fd = p->sim_fd(p->getSyscallArg(tc, 0));
-    uint64_t offset_high = p->getSyscallArg(tc, 1);
-    uint32_t offset_low = p->getSyscallArg(tc, 2);
-    Addr result_ptr = p->getSyscallArg(tc, 3);
-    int whence = p->getSyscallArg(tc, 4);
+    int index = 0;
+    int fd = p->sim_fd(p->getSyscallArg(tc, index));
+    uint64_t offset_high = p->getSyscallArg(tc, index);
+    uint32_t offset_low = p->getSyscallArg(tc, index);
+    Addr result_ptr = p->getSyscallArg(tc, index);
+    int whence = p->getSyscallArg(tc, index);
 
     uint64_t offset = (offset_high << 32) | offset_low;
 
@@ -273,8 +287,10 @@ const char *hostname = "m5.eecs.umich.edu";
 SyscallReturn
 gethostnameFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
-    int name_len = p->getSyscallArg(tc, 1);
-    BufferArg name(p->getSyscallArg(tc, 0), name_len);
+    int index = 0;
+    Addr bufPtr = p->getSyscallArg(tc, index);
+    int name_len = p->getSyscallArg(tc, index);
+    BufferArg name(bufPtr, name_len);
 
     strncpy((char *)name.bufferPtr(), hostname, name_len);
 
@@ -287,8 +303,10 @@ SyscallReturn
 getcwdFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
     int result = 0;
-    unsigned long size = p->getSyscallArg(tc, 1);
-    BufferArg buf(p->getSyscallArg(tc, 0), size);
+    int index;
+    Addr bufPtr = p->getSyscallArg(tc, index);
+    unsigned long size = p->getSyscallArg(tc, index);
+    BufferArg buf(bufPtr, size);
 
     // Is current working directory defined?
     string cwd = p->getcwd();
@@ -320,14 +338,17 @@ readlinkFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
     string path;
 
-    if (!tc->getMemPort()->tryReadString(path, p->getSyscallArg(tc, 0)))
+    int index = 0;
+    if (!tc->getMemPort()->tryReadString(path, p->getSyscallArg(tc, index)))
         return (TheISA::IntReg)-EFAULT;
 
     // Adjust path for current working directory
     path = p->fullPath(path);
 
-    size_t bufsiz = p->getSyscallArg(tc, 2);
-    BufferArg buf(p->getSyscallArg(tc, 1), bufsiz);
+    Addr bufPtr = p->getSyscallArg(tc, index);
+    size_t bufsiz = p->getSyscallArg(tc, index);
+
+    BufferArg buf(bufPtr, bufsiz);
 
     int result = readlink(path.c_str(), (char *)buf.bufferPtr(), bufsiz);
 
@@ -341,7 +362,8 @@ unlinkFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
     string path;
 
-    if (!tc->getMemPort()->tryReadString(path, p->getSyscallArg(tc, 0)))
+    int index = 0;
+    if (!tc->getMemPort()->tryReadString(path, p->getSyscallArg(tc, index)))
         return (TheISA::IntReg)-EFAULT;
 
     // Adjust path for current working directory
@@ -357,13 +379,14 @@ mkdirFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
     string path;
 
-    if (!tc->getMemPort()->tryReadString(path, p->getSyscallArg(tc, 0)))
+    int index = 0;
+    if (!tc->getMemPort()->tryReadString(path, p->getSyscallArg(tc, index)))
         return (TheISA::IntReg)-EFAULT;
 
     // Adjust path for current working directory
     path = p->fullPath(path);
 
-    mode_t mode = p->getSyscallArg(tc, 1);
+    mode_t mode = p->getSyscallArg(tc, index);
 
     int result = mkdir(path.c_str(), mode);
     return (result == -1) ? -errno : result;
@@ -374,12 +397,13 @@ renameFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
     string old_name;
 
-    if (!tc->getMemPort()->tryReadString(old_name, p->getSyscallArg(tc, 0)))
+    int index = 0;
+    if (!tc->getMemPort()->tryReadString(old_name, p->getSyscallArg(tc, index)))
         return -EFAULT;
 
     string new_name;
 
-    if (!tc->getMemPort()->tryReadString(new_name, p->getSyscallArg(tc, 1)))
+    if (!tc->getMemPort()->tryReadString(new_name, p->getSyscallArg(tc, index)))
         return -EFAULT;
 
     // Adjust path for current working directory
@@ -395,10 +419,11 @@ truncateFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
     string path;
 
-    if (!tc->getMemPort()->tryReadString(path, p->getSyscallArg(tc, 0)))
+    int index = 0;
+    if (!tc->getMemPort()->tryReadString(path, p->getSyscallArg(tc, index)))
         return -EFAULT;
 
-    off_t length = p->getSyscallArg(tc, 1);
+    off_t length = p->getSyscallArg(tc, index);
 
     // Adjust path for current working directory
     path = p->fullPath(path);
@@ -411,12 +436,13 @@ SyscallReturn
 ftruncateFunc(SyscallDesc *desc, int num,
               LiveProcess *process, ThreadContext *tc)
 {
-    int fd = process->sim_fd(process->getSyscallArg(tc, 0));
+    int index = 0;
+    int fd = process->sim_fd(process->getSyscallArg(tc, index));
 
     if (fd < 0)
         return -EBADF;
 
-    off_t length = process->getSyscallArg(tc, 1);
+    off_t length = process->getSyscallArg(tc, index);
 
     int result = ftruncate(fd, length);
     return (result == -1) ? -errno : result;
@@ -426,13 +452,13 @@ SyscallReturn
 ftruncate64Func(SyscallDesc *desc, int num,
                 LiveProcess *process, ThreadContext *tc)
 {
-    int fd = process->sim_fd(process->getSyscallArg(tc, 0));
+    int index = 0;
+    int fd = process->sim_fd(process->getSyscallArg(tc, index));
 
     if (fd < 0)
         return -EBADF;
 
-    // I'm not sure why, but the length argument is in arg reg 3
-    loff_t length = process->getSyscallArg(tc, 3);
+    loff_t length = process->getSyscallArg(tc, index, 64);
 
     int result = ftruncate64(fd, length);
     return (result == -1) ? -errno : result;
@@ -454,13 +480,14 @@ chownFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 {
     string path;
 
-    if (!tc->getMemPort()->tryReadString(path, p->getSyscallArg(tc, 0)))
+    int index = 0;
+    if (!tc->getMemPort()->tryReadString(path, p->getSyscallArg(tc, index)))
         return -EFAULT;
 
     /* XXX endianess */
-    uint32_t owner = p->getSyscallArg(tc, 1);
+    uint32_t owner = p->getSyscallArg(tc, index);
     uid_t hostOwner = owner;
-    uint32_t group = p->getSyscallArg(tc, 2);
+    uint32_t group = p->getSyscallArg(tc, index);
     gid_t hostGroup = group;
 
     // Adjust path for current working directory
@@ -473,15 +500,16 @@ chownFunc(SyscallDesc *desc, int num, LiveProcess *p, ThreadContext *tc)
 SyscallReturn
 fchownFunc(SyscallDesc *desc, int num, LiveProcess *process, ThreadContext *tc)
 {
-    int fd = process->sim_fd(process->getSyscallArg(tc, 0));
+    int index = 0;
+    int fd = process->sim_fd(process->getSyscallArg(tc, index));
 
     if (fd < 0)
         return -EBADF;
 
     /* XXX endianess */
-    uint32_t owner = process->getSyscallArg(tc, 1);
+    uint32_t owner = process->getSyscallArg(tc, index);
     uid_t hostOwner = owner;
-    uint32_t group = process->getSyscallArg(tc, 2);
+    uint32_t group = process->getSyscallArg(tc, index);
     gid_t hostGroup = group;
 
     int result = fchown(fd, hostOwner, hostGroup);
@@ -492,11 +520,12 @@ fchownFunc(SyscallDesc *desc, int num, LiveProcess *process, ThreadContext *tc)
 SyscallReturn
 dupFunc(SyscallDesc *desc, int num, LiveProcess *process, ThreadContext *tc)
 {
-    int fd = process->sim_fd(process->getSyscallArg(tc, 0));
+    int index = 0;
+    int fd = process->sim_fd(process->getSyscallArg(tc, index));
     if (fd < 0)
         return -EBADF;
 
-    Process::FdMap *fdo = process->sim_fd_obj(process->getSyscallArg(tc, 0));
+    Process::FdMap *fdo = process->sim_fd_obj(fd);
 
     int result = dup(fd);
     return (result == -1) ? -errno :
@@ -508,12 +537,13 @@ SyscallReturn
 fcntlFunc(SyscallDesc *desc, int num, LiveProcess *process,
           ThreadContext *tc)
 {
-    int fd = process->getSyscallArg(tc, 0);
+    int index = 0;
+    int fd = process->getSyscallArg(tc, index);
 
     if (fd < 0 || process->sim_fd(fd) < 0)
         return -EBADF;
 
-    int cmd = process->getSyscallArg(tc, 1);
+    int cmd = process->getSyscallArg(tc, index);
     switch (cmd) {
       case 0: // F_DUPFD
         // if we really wanted to support this, we'd need to do it
@@ -550,12 +580,13 @@ SyscallReturn
 fcntl64Func(SyscallDesc *desc, int num, LiveProcess *process,
             ThreadContext *tc)
 {
-    int fd = process->getSyscallArg(tc, 0);
+    int index = 0;
+    int fd = process->getSyscallArg(tc, index);
 
     if (fd < 0 || process->sim_fd(fd) < 0)
         return -EBADF;
 
-    int cmd = process->getSyscallArg(tc, 1);
+    int cmd = process->getSyscallArg(tc, index);
     switch (cmd) {
       case 33: //F_GETLK64
         warn("fcntl64(%d, F_GETLK64) not supported, error returned\n", fd);
@@ -639,7 +670,8 @@ setuidFunc(SyscallDesc *desc, int callnum, LiveProcess *process,
            ThreadContext *tc)
 {
     // can't fathom why a benchmark would call this.
-    warn("Ignoring call to setuid(%d)\n", process->getSyscallArg(tc, 0));
+    int index = 0;
+    warn("Ignoring call to setuid(%d)\n", process->getSyscallArg(tc, index));
     return 0;
 }
 
@@ -695,17 +727,20 @@ SyscallReturn
 cloneFunc(SyscallDesc *desc, int callnum, LiveProcess *process,
            ThreadContext *tc)
 {
+    int index = 0;
+    IntReg flags = process->getSyscallArg(tc, index);
+    IntReg newStack = process->getSyscallArg(tc, index);
+
     DPRINTF(SyscallVerbose, "In sys_clone:\n");
-    DPRINTF(SyscallVerbose, " Flags=%llx\n", process->getSyscallArg(tc, 0));
-    DPRINTF(SyscallVerbose, " Child stack=%llx\n",
-            process->getSyscallArg(tc, 1));
+    DPRINTF(SyscallVerbose, " Flags=%llx\n", flags);
+    DPRINTF(SyscallVerbose, " Child stack=%llx\n", newStack);
 
 
-    if (process->getSyscallArg(tc, 0) != 0x10f00) {
+    if (flags != 0x10f00) {
         warn("This sys_clone implementation assumes flags "
              "CLONE_VM|CLONE_FS|CLONE_FILES|CLONE_SIGHAND|CLONE_THREAD "
              "(0x10f00), and may not work correctly with given flags "
-             "0x%llx\n", process->getSyscallArg(tc, 0));
+             "0x%llx\n", flags);
     }
 
     ThreadContext* ctc; // child thread context
@@ -738,7 +773,7 @@ cloneFunc(SyscallDesc *desc, int callnum, LiveProcess *process,
         #endif
 
         // Set up stack register
-        ctc->setIntReg(TheISA::StackPointerReg, process->getSyscallArg(tc, 1));
+        ctc->setIntReg(TheISA::StackPointerReg, newStack);
 
         // Set up syscall return values in parent and child
         ctc->setIntReg(ReturnValueReg, 0); // return value, child