syscall-emul: Add functionality to open syscalls

This changeset adds refactors the existing open system call,
adds the openat variant (enabled for x86 builds), and adds
additional "special file" test cases for /proc/meminfo and
/etc/passwd.

Change-Id: I6f429db65bbf2a28ffa3fd12df518c2d0de49663
Reviewed-on: https://gem5-review.googlesource.com/2265
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Tony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Michael LeBeane <Michael.Lebeane@amd.com>

3 files changed, 32 insertions, 7 deletions

diff --git a/src/kern/linux/linux.cc b/src/kern/linux/linux.cc
index 493be9611..bd0b4d09a 100644
--- a/src/kern/linux/linux.cc
+++ b/src/kern/linux/linux.cc
@@ -33,6 +33,7 @@
 #include <cstdio>
 #include <string>
 
+#include "cpu/base.hh"
 #include "debug/SyscallVerbose.hh"
 #include "sim/process.hh"
 #include "sim/system.hh"
@@ -41,21 +42,35 @@ int
 Linux::openSpecialFile(std::string path, Process *process,
                        ThreadContext *tc)
 {
-    DPRINTF(SyscallVerbose, "Opening special file: %s\n", path.c_str());
+    DPRINTFR(SyscallVerbose,
+             "%d: %s: generic-open: opening special file: %s\n",
+             curTick(), tc->getCpuPtr()->name(), path.c_str());
+
+    bool matched = false;
+    std::string data;
+
     if (path.compare(0, 13, "/proc/meminfo") == 0) {
-        std::string data = Linux::procMeminfo(process, tc);
+        data = Linux::procMeminfo(process, tc);
+        matched = true;
+    } else if (path.compare(0, 11, "/etc/passwd") == 0) {
+        data = Linux::etcPasswd(process, tc);
+        matched = true;
+    }
+
+    if (matched) {
         FILE *f = tmpfile();
         int fd = fileno(f);
         size_t ret M5_VAR_USED = fwrite(data.c_str(), 1, data.size(), f);
         assert(ret == data.size());
         rewind(f);
         return fd;
+    } else {
+        warn("Attempting to open special file: %s. Ignoring. Simulation may "
+             "take un-expected code path or be non-deterministic until proper "
+             "handling is implemented.\n", path.c_str());
+        errno = EACCES;
+        return -1;
     }
-
-    warn("Attempting to open special file: %s. Ignoring. Simulation may"
-            " take un-expected code path or be non-deterministic until proper"
-            "  handling is implemented.\n", path.c_str());
-    return -1;
 }
 
 std::string
@@ -66,3 +81,9 @@ Linux::procMeminfo(Process *process, ThreadContext *tc)
             process->system->freeMemSize() >> 10);
 }
 
+std::string
+Linux::etcPasswd(Process *process, ThreadContext *tc)
+{
+    return csprintf("gem5-user:x:1000:1000:gem5-user,,,:%s:/bin/bash\n",
+                    process->getcwd());
+}
diff --git a/src/kern/linux/linux.hh b/src/kern/linux/linux.hh
index e6899a9ca..b24ee3895 100644
--- a/src/kern/linux/linux.hh
+++ b/src/kern/linux/linux.hh
@@ -226,6 +226,7 @@ class Linux : public OperatingSystem
     static int openSpecialFile(std::string path, Process *process,
                                ThreadContext *tc);
     static std::string procMeminfo(Process *process, ThreadContext *tc);
+    static std::string etcPasswd(Process *process, ThreadContext *tc);
 
     // For futex system call
     static const unsigned TGT_FUTEX_WAIT  = 0;
diff --git a/src/kern/solaris/solaris.hh b/src/kern/solaris/solaris.hh
index 9cd5af16f..d875f4402 100644
--- a/src/kern/solaris/solaris.hh
+++ b/src/kern/solaris/solaris.hh
@@ -114,6 +114,9 @@ class Solaris : public OperatingSystem
         char machine[_SYS_NMLN];        //!< Machine type.
     } utsname;
 
+    // for *at syscalls
+    static const int TGT_AT_FDCWD   = -100;
+
 };  // class Solaris
 
 #endif // __SOLARIS_HH__