sim-se: add new getpgrp system call

This changeset adds new (relatively simple) system call
support. The getpgrp call returns a thread context's
pgid.

Change-Id: I361bdbfb9c01b761ddd5a4923d23f86971f8d614
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/17111
Maintainer: Brandon Potter <Brandon.Potter@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Ayaz Akram <yazakram@ucdavis.edu>

src/arch/x86/linux/process.cc

@@ -373,7 +373,7 @@ static SyscallDesc syscallDescs64[] = {
     /* 108 */ SyscallDesc("getegid", getegidFunc),
     /* 109 */ SyscallDesc("setpgid", setpgidFunc),
     /* 110 */ SyscallDesc("getppid", getppidFunc),
-    /* 111 */ SyscallDesc("getpgrp", unimplementedFunc),
+    /* 111 */ SyscallDesc("getpgrp", getpgrpFunc),
     /* 112 */ SyscallDesc("setsid", unimplementedFunc),
     /* 113 */ SyscallDesc("setreuid", unimplementedFunc),
     /* 114 */ SyscallDesc("setregid", unimplementedFunc),

src/sim/syscall_emul.cc

@@ -982,6 +982,13 @@ pipe2Func(SyscallDesc *desc, int callnum, ThreadContext *tc)
     return pipeImpl(desc, callnum, tc, false, true);
 }
 
+SyscallReturn
+getpgrpFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
+{
+    auto process = tc->getProcessPtr();
+    return process->pgid();
+}
+
 SyscallReturn
 setpgidFunc(SyscallDesc *desc, int callnum, ThreadContext *tc)
 {

src/sim/syscall_emul.hh

@@ -226,6 +226,9 @@ SyscallReturn gettidFunc(SyscallDesc *desc, int num, ThreadContext *tc);
 /// Target chown() handler.
 SyscallReturn chownFunc(SyscallDesc *desc, int num, ThreadContext *tc);
 
+/// Target getpgrpFunc() handler.
+SyscallReturn getpgrpFunc(SyscallDesc *desc, int num, ThreadContext *tc);
+
 /// Target setpgid() handler.
 SyscallReturn setpgidFunc(SyscallDesc *desc, int num, ThreadContext *tc);