From eaa3df9cbadd8737da8a3c76acdaabdaeb52b378 Mon Sep 17 00:00:00 2001
From: Ryan Houdek <Sonicadvance1@gmail.com>
Date: Sun, 20 Jun 2021 01:07:58 -0700
Subject: [PATCH] Fixes fixed stack offset for 32-bit applications

Instead of forcing a fixed offset for the stack. Allow it to get placed automatically.
64-bit was already doing this; Now we can also do it in 32-bit.
This is possible because the mapper that is mapping the code will always map in the 32-bit space
for a 32-bit guest.
---
 Source/Tests/ELFCodeLoader.h  | 13 +++----------
 Source/Tests/ELFCodeLoader2.h | 17 ++++++-----------
 2 files changed, 9 insertions(+), 21 deletions(-)

diff --git a/Source/Tests/ELFCodeLoader.h b/Source/Tests/ELFCodeLoader.h
index 65c8225ed..7ad521d6d 100644
--- a/Source/Tests/ELFCodeLoader.h
+++ b/Source/Tests/ELFCodeLoader.h
@@ -194,13 +194,7 @@ public:
 
   uint64_t GetStackPointer() override {
     uintptr_t StackPointer{};
-    if (File.GetMode() == ::ELFLoader::ELFContainer::MODE_64BIT) {
-      StackPointer = reinterpret_cast<uintptr_t>(FEXCore::Allocator::mmap(nullptr, StackSize(), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
-    }
-    else {
-      StackPointer = reinterpret_cast<uintptr_t>(FEXCore::Allocator::mmap(reinterpret_cast<void*>(STACK_OFFSET), StackSize(), PROT_READ | PROT_WRITE, MAP_FIXED_NOREPLACE | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
-      LOGMAN_THROW_A(StackPointer != ~0ULL, "Get Stack Pointer mmap failed");
-    }
+    StackPointer = reinterpret_cast<uintptr_t>(FEXCore::Allocator::mmap(nullptr, StackSize(), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
 
     StackPointer += StackSize();
     // Set up our initial CPU state
@@ -307,13 +301,13 @@ public:
   }
 
   char const *FindSymbolNameInRange(uint64_t Address) {
-    
+
     ELFLoader::ELFSymbol const *Sym;
     Sym = DB.GetSymbolInRange(std::make_pair(Address, 1));
     if (Sym) {
       return Sym->Name;
     }
-    
+
     return nullptr;
   }
 
@@ -356,7 +350,6 @@ private:
   uint64_t EnvironmentBackingSize{};
 
   constexpr static uint64_t STACK_SIZE = 8 * 1024 * 1024;
-  constexpr static uint64_t STACK_OFFSET = 0xc000'0000;
 };
 
 }
diff --git a/Source/Tests/ELFCodeLoader2.h b/Source/Tests/ELFCodeLoader2.h
index 2c6493afb..0ae450b99 100644
--- a/Source/Tests/ELFCodeLoader2.h
+++ b/Source/Tests/ELFCodeLoader2.h
@@ -56,7 +56,7 @@ class ELFCodeLoader2 final : public FEXCore::CodeLoader {
 
     if (first == headers.end())
       return 0;
-    
+
     return PAGE_ALIGN(last->p_vaddr + last->p_memsz) - PAGE_START(first->p_vaddr);
   }
 
@@ -106,7 +106,7 @@ class ELFCodeLoader2 final : public FEXCore::CodeLoader {
   std::optional<uintptr_t> LoadElfFile(ELFParser& Elf, uintptr_t *BrkBase, TMap Mapper, TUnmap Unmapper) {
 
     uintptr_t LoadBase = 0;
-       
+
     if (Elf.ehdr.e_type == ET_DYN) {
       // needs base address
       auto TotalSize  = CalculateTotalElfSize(Elf.phdrs) + (BrkBase ? BRK_SIZE : 0);
@@ -135,7 +135,7 @@ class ELFCodeLoader2 final : public FEXCore::CodeLoader {
 			if (!MapFile(Elf, LoadBase, Header, MapProt, MapType, Mapper)) {
         return {};
       }
-	
+
       if (Header.p_memsz > Header.p_filesz) {
         // clear bss
         auto BSSStart = LoadBase + Header.p_vaddr + Header.p_filesz;
@@ -297,12 +297,8 @@ class ELFCodeLoader2 final : public FEXCore::CodeLoader {
     // ADDR_LIMIT_3GB STACK -> 0xc0000000 else -> 0xFFFFe000
 
     // map stack here, so that nothing gets mapped there
-    if (Is64BitMode()) {
-      StackPointer = reinterpret_cast<uintptr_t>(Mapper(nullptr, StackSize(), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK | MAP_GROWSDOWN, -1, 0));
-    }
-    else {
-      StackPointer = reinterpret_cast<uintptr_t>(Mapper(reinterpret_cast<void*>(STACK_OFFSET), StackSize(), PROT_READ | PROT_WRITE, MAP_FIXED_NOREPLACE | MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK | MAP_GROWSDOWN, -1, 0));
-    }
+    // This works with both 64-bit and 32-bit. The mapper will only give us a function in the correct region
+    StackPointer = reinterpret_cast<uintptr_t>(Mapper(nullptr, StackSize(), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK | MAP_GROWSDOWN, -1, 0));
 
     if (StackPointer == ~0ULL) {
       LogMan::Msg::E("Allocating stack failed");
@@ -325,7 +321,7 @@ class ELFCodeLoader2 final : public FEXCore::CodeLoader {
     // XXX Randomise brk?
 
     BrkStart = (uint64_t)Mapper((void*)BrkBase, BRK_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED_NOREPLACE, 0, 0);
-    
+
     if ((void*)BrkStart == MAP_FAILED) {
       LogMan::Msg::E("Failed to allocate BRK @ %lx, %d\n", BrkBase, errno);
       return false;
@@ -585,7 +581,6 @@ class ELFCodeLoader2 final : public FEXCore::CodeLoader {
 
   constexpr static uint64_t BRK_SIZE = 8 * 1024 * 1024;
   constexpr static uint64_t STACK_SIZE = 8 * 1024 * 1024;
-  constexpr static uint64_t STACK_OFFSET = 0xc000'0000;
 
   std::vector<std::string> Args;
   std::vector<std::string> EnvironmentVariables;