From 46bf4043976a8c4eb6310db917a4560da9548cb1 Mon Sep 17 00:00:00 2001
From: Gabe Black <gabeblack@google.com>
Date: Sat, 7 Dec 2019 03:31:58 -0800
Subject: [PATCH] sim: Convert the various flavors of pipe to GuestABI.

Change-Id: I44aaff417ea6a3ce311208b084fe4013bb93a48e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23457
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Gabe Black <gabeblack@google.com>
---
 src/sim/syscall_emul.cc | 59 ++++++++++++++---------------------------
 src/sim/syscall_emul.hh | 10 +++----
 2 files changed, 24 insertions(+), 45 deletions(-)

diff --git a/src/sim/syscall_emul.cc b/src/sim/syscall_emul.cc
index 731cf247e..2dbd9d547 100644
--- a/src/sim/syscall_emul.cc
+++ b/src/sim/syscall_emul.cc
@@ -810,19 +810,22 @@ fcntl64Func(SyscallDesc *desc, int num, ThreadContext *tc,
 }
 
 SyscallReturn
-pipeImpl(SyscallDesc *desc, int callnum, ThreadContext *tc, bool pseudo_pipe,
-         bool is_pipe2)
+pipePseudoFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
+{
+    return pipe2Func(desc, callnum, tc, 0, 0);
+}
+
+SyscallReturn
+pipeFunc(SyscallDesc *desc, int callnum, ThreadContext *tc, Addr tgt_addr)
+{
+    return pipe2Func(desc, callnum, tc, tgt_addr, 0);
+}
+
+SyscallReturn
+pipe2Func(SyscallDesc *desc, int callnum, ThreadContext *tc,
+          Addr tgt_addr, int flags)
 {
-    Addr tgt_addr = 0;
-    int flags = 0;
     auto p = tc->getProcessPtr();
-    if (!pseudo_pipe) {
-        int index = 0;
-        tgt_addr = p->getSyscallArg(tc, index);
-        if (is_pipe2) {
-            flags = p->getSyscallArg(tc, index);
-        }
-    }
 
     int sim_fds[2], tgt_fds[2];
 
@@ -847,13 +850,12 @@ pipeImpl(SyscallDesc *desc, int callnum, ThreadContext *tc, bool pseudo_pipe,
     rpfd->setPipeReadSource(tgt_fds[1]);
 
     /**
-     * Alpha Linux convention for pipe() is that fd[0] is returned as
-     * the return value of the function, and fd[1] is returned in r20.
+     * On some architectures, it's possible to use more than one register for
+     * a return value. In those cases, pipe returns its values rather than
+     * write them into a buffer.
      */
-    if (pseudo_pipe) {
-        tc->setIntReg(SyscallPseudoReturnReg, tgt_fds[1]);
-        return tgt_fds[0];
-    }
+    if (tgt_addr == 0)
+        return SyscallReturn(tgt_fds[0], tgt_fds[1]);
 
     /**
      * Copy the target file descriptors into buffer space and then copy
@@ -865,8 +867,7 @@ pipeImpl(SyscallDesc *desc, int callnum, ThreadContext *tc, bool pseudo_pipe,
     buf_ptr[1] = tgt_fds[1];
     tgt_handle.copyOut(tc->getVirtProxy());
 
-    // pipe2 has additional behavior if flags != 0
-    if (is_pipe2 && flags) {
+    if (flags) {
         // pipe2 only uses O_NONBLOCK, O_CLOEXEC, and (O_NONBLOCK | O_CLOEXEC)
         // if flags set to anything else, return EINVAL
         if ((flags != O_CLOEXEC) && (flags != O_NONBLOCK) &&
@@ -906,26 +907,6 @@ pipeImpl(SyscallDesc *desc, int callnum, ThreadContext *tc, bool pseudo_pipe,
     return 0;
 }
 
-SyscallReturn
-pipePseudoFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
-{
-    return pipeImpl(desc, callnum, tc, true);
-}
-
-SyscallReturn
-pipeFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
-{
-    return pipeImpl(desc, callnum, tc, false);
-}
-
-SyscallReturn
-pipe2Func(SyscallDesc *desc, int callnum, ThreadContext *tc)
-{
-    // call pipeImpl since the only difference between pipe and pipe2 is
-    // the flags values and what they do (at the end of pipeImpl)
-    return pipeImpl(desc, callnum, tc, false, true);
-}
-
 SyscallReturn
 getpgrpFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
 {
diff --git a/src/sim/syscall_emul.hh b/src/sim/syscall_emul.hh
index 2df5579de..cc079537c 100644
--- a/src/sim/syscall_emul.hh
+++ b/src/sim/syscall_emul.hh
@@ -276,14 +276,12 @@ SyscallReturn fcntl64Func(SyscallDesc *desc, int num, ThreadContext *tc,
                           int tgt_fd, int cmd);
 
 /// Target pipe() handler.
-SyscallReturn pipeFunc(SyscallDesc *desc, int num, ThreadContext *tc);
-
-/// Internal pipe() handler.
-SyscallReturn pipeImpl(SyscallDesc *desc, int num, ThreadContext *tc,
-                       bool pseudo_pipe, bool is_pipe2=false);
+SyscallReturn pipeFunc(SyscallDesc *desc, int num, ThreadContext *tc,
+                       Addr tgt_addr);
 
 /// Target pipe() handler.
-SyscallReturn pipe2Func(SyscallDesc *desc, int num, ThreadContext *tc);
+SyscallReturn pipe2Func(SyscallDesc *desc, int num, ThreadContext *tc,
+                        Addr tgt_addr, int flags);
 
 /// Target getpid() handler.
 SyscallReturn getpidFunc(SyscallDesc *desc, int num, ThreadContext *tc);
-- 
2.30.2