arch-arm: Add aarch64 semihosting support

Add basic support for Arm Semihosting 2.0 simulation calls [1]. These
calls let the guest system call a simulator or debugger to request
OS-like support when running bare metal code.

With the exception of SYS_SYSTEM, this implementation supports all of
the Semihosting 2.0 specification in aarch64.

[1] https://developer.arm.com/docs/100863/latest/preface

Change-Id: I08c153c18a4a4fb9f95d318e2a029724935192a7
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Jack Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/8147
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/src/arch/arm/system.cc b/src/arch/arm/system.cc
index 50ac4aeeb..caef6dc8f 100644
--- a/src/arch/arm/system.cc
+++ b/src/arch/arm/system.cc
@@ -44,6 +44,7 @@
 
 #include <iostream>
 
+#include "arch/arm/semihosting.hh"
 #include "base/loader/object_file.hh"
 #include "base/loader/symtab.hh"
 #include "cpu/thread_context.hh"
@@ -70,6 +71,7 @@ ArmSystem::ArmSystem(Params *p)
       _m5opRange(p->m5ops_base ?
                  RangeSize(p->m5ops_base, 0x10000) :
                  AddrRange(1, 0)), // Create an empty range if disabled
+      semihosting(p->semihosting),
       multiProc(p->multi_proc)
 {
     // Check if the physical address range is valid
@@ -268,6 +270,28 @@ ArmSystem::haveLargeAsid64(ThreadContext *tc)
     return getArmSystem(tc)->haveLargeAsid64();
 }
 
+bool
+ArmSystem::haveSemihosting(ThreadContext *tc)
+{
+    return getArmSystem(tc)->haveSemihosting();
+}
+
+uint64_t
+ArmSystem::callSemihosting64(ThreadContext *tc,
+                             uint32_t op, uint64_t param)
+{
+    ArmSystem *sys = getArmSystem(tc);
+    return sys->semihosting->call64(tc, op, param);
+}
+
+uint32_t
+ArmSystem::callSemihosting32(ThreadContext *tc,
+                             uint32_t op, uint32_t param)
+{
+    ArmSystem *sys = getArmSystem(tc);
+    return sys->semihosting->call32(tc, op, param);
+}
+
 ArmSystem *
 ArmSystemParams::create()
 {