From 68d07bdfaae35cb954f55c88366755eb2e387c0b Mon Sep 17 00:00:00 2001
From: Yury Popov <github@phoenix.dj>
Date: Thu, 23 May 2019 19:55:57 +0300
Subject: [PATCH] Fix stack-related exception on process exit

---
 src/platform/syscall.cpp | 7 +++++--
 src/process/process.cpp  | 8 +++++---
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/platform/syscall.cpp b/src/platform/syscall.cpp
index b38d018..7b57af1 100644
--- a/src/platform/syscall.cpp
+++ b/src/platform/syscall.cpp
@@ -17,11 +17,14 @@ static void syscall_puts(uintptr_t strptr) {
 static void syscall_exit(int code) {
   ProcessManager *manager = ProcessManager::getManager();
   Process *process = manager->currentProcess();
+  void *rsp; asm volatile("mov %%rsp, %q0; and $~0xFFF, %q0":"=r"(rsp));
+  Pagetable::Entry *pt; asm volatile("mov %%cr3, %q0":"=r"(pt));
+  Pagetable::Entry *pte = Pagetable::Entry::find(rsp, pt);
   asm volatile(
       "callq _ZN7Process4exitEi;"
-      "sti;"
+      "sti; movq $0, %q2;"
       "jmp _ZN14ProcessManager12process_loopEv"
-      ::"D"(process), "S"(code)
+      ::"D"(process), "S"(code), "a"(pte)
       );
 }
 
diff --git a/src/process/process.cpp b/src/process/process.cpp
index d89b373..683bcab 100644
--- a/src/process/process.cpp
+++ b/src/process/process.cpp
@@ -16,6 +16,7 @@ Process::Process() {
   _aslrStack = RAND::get<uintptr_t>(0x40000000llu, 0x80000000llu) << 12;
 }
 Process::~Process() {
+  void *rsp; asm volatile("mov %%rsp, %q0; and $~0xFFF, %q0":"=r"(rsp));
   if (pagetable != nullptr) {
     PTE addr;
     for (uintptr_t ptx = 0; ptx < 512; ptx++) {
@@ -38,10 +39,11 @@ Process::~Process() {
             if (!addr.present)
               continue;
             void *page = addr.getPtr();
-            if (uintptr_t(page) == ((ptx << (12 + 9 + 9 + 9))
+            uintptr_t ptaddr = ((ptx << (12 + 9 + 9 + 9))
                 | (pdx << (12 + 9 + 9))
-                | (pdpx << (12 + 9)) | (pml4x << (12))))
-              continue;
+                | (pdpx << (12 + 9)) | (pml4x << (12)));
+            if (page == rsp) continue;
+            if (uintptr_t(page) == ptaddr) continue;
             Pagetable::free(page);
           }
           Pagetable::free(ppml4e);