From 6815ccdf68d995acd9a93842753e48448696d2da Mon Sep 17 00:00:00 2001
From: Michael Scire <SciresM@gmail.com>
Date: Tue, 24 Sep 2019 21:43:18 -0700
Subject: [PATCH] mitm: fix long-standing C descriptor issue.

---
 include/stratosphere/mitm/mitm_session.hpp | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/stratosphere/mitm/mitm_session.hpp b/include/stratosphere/mitm/mitm_session.hpp
index 71c45cbb..13110ce8 100644
--- a/include/stratosphere/mitm/mitm_session.hpp
+++ b/include/stratosphere/mitm/mitm_session.hpp
@@ -80,6 +80,23 @@ class MitmSession final : public ServiceSession {
         }
 
         Result ForwardRequest(IpcResponseContext *ctx) {
+            /* Mitm forward specific preprocessing. */
+            if (ctx->request.NumStaticsOut) {
+                u32 *cmdbuf = (u32 *)armGetTls();
+                /* Overwrite the number of C descriptors to only use a single buffer. */
+                cmdbuf[1] = (cmdbuf[1] & (~u32(0xF << 10))) | (0x2 << 10);
+
+                IpcStaticRecvDescriptor *c_desc = (IpcStaticRecvDescriptor *)(reinterpret_cast<uintptr_t>(ctx->request.RawWithoutPadding) + ctx->request.RawSize);
+                /* Don't write out of bounds, though this should never happen. */
+                if (reinterpret_cast<uintptr_t>(c_desc) + sizeof(*c_desc) <= reinterpret_cast<uintptr_t>(cmdbuf) + 0x100) {
+                    uintptr_t ptr = reinterpret_cast<uintptr_t>(this->pointer_buffer.data());
+                    c_desc->Addr = ptr;
+                    c_desc->Packed = (ptr >> 32) | (this->pointer_buffer.size() << 16);
+                } else {
+                    std::abort();
+                }
+            }
+
             /* Dispatch forwards. */
             R_TRY(serviceIpcDispatch(this->forward_service.get()));