From c829dc3dab47b9d1643535424f222ffde3135262 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sat, 9 Mar 2024 21:29:48 +0100
Subject: [PATCH 01/32] - Added support for SMEP not being available on the
 CPU.

---
 src/common/cpuid.cpp         | 6 ++++++
 src/common/include/cpuid.hpp | 3 +++
 src/x86_32/arch.cpp          | 2 +-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/common/cpuid.cpp b/src/common/cpuid.cpp
index 573a275..dab22a2 100644
--- a/src/common/cpuid.cpp
+++ b/src/common/cpuid.cpp
@@ -47,3 +47,9 @@ bool has_nx()
   return get_cpuid_max_ext_level() >= 0x80000001
     and (get_cpuid(0x80000001).edx & (1 << 20));
 }
+
+bool has_smep()
+{
+    return get_cpuid_max_std_level() >= 7
+        and (get_cpuid(0x7).ebx & (1 << 7));
+}
diff --git a/src/common/include/cpuid.hpp b/src/common/include/cpuid.hpp
index 05d6462..ebaee49 100644
--- a/src/common/include/cpuid.hpp
+++ b/src/common/include/cpuid.hpp
@@ -26,3 +26,6 @@ uint32_t get_cpuid_max_ext_level();
 
 // Returns true, if the CPU reports being able to use the NX bit.
 bool has_nx();
+
+// Returns true, if the CPU reports being able to use SMEP.
+bool has_smep();
diff --git a/src/x86_32/arch.cpp b/src/x86_32/arch.cpp
index 27cac9a..829a6f1 100644
--- a/src/x86_32/arch.cpp
+++ b/src/x86_32/arch.cpp
@@ -69,7 +69,7 @@ static void setup_paging()
   pdt[bit_select(32, 22, up)] = reinterpret_cast<uintptr_t>(user_pt) | PTE_U | PTE_P;
   user_pt[bit_select(22, 12, up)] = reinterpret_cast<uintptr_t>(get_user_page_backing()) | PTE_U | PTE_P;
 
-  set_cr4(get_cr4() | CR4_PSE | CR4_SMEP);
+  set_cr4(get_cr4() | CR4_PSE | (has_smep()?CR4_SMEP:0));
   set_cr3((uintptr_t)pdt);
   set_cr0(get_cr0() | CR0_PG | CR0_WP);
 }

From d6923538e30795055d2d2c28952ed2f47de95bd8 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sun, 10 Mar 2024 04:24:07 +0100
Subject: [PATCH 02/32] - Implemented 80386 paging and CPUID support.

---
 src/common/cpuid.cpp         | 46 ++++++++++++++++++++++++++++++++++++
 src/common/include/cpuid.hpp |  3 +++
 src/x86_32/arch.cpp          | 46 +++++++++++++++++++++++++++++++++---
 3 files changed, 92 insertions(+), 3 deletions(-)

diff --git a/src/common/cpuid.cpp b/src/common/cpuid.cpp
index dab22a2..309ed17 100644
--- a/src/common/cpuid.cpp
+++ b/src/common/cpuid.cpp
@@ -2,9 +2,49 @@
 
 #include "cpuid.hpp"
 
+bool cpuid_supported()
+{
+    #ifndef __x86_64__
+    //We need to check for the existence of CPUID on 32-bit platforms!
+    unsigned int res1,res2;
+    asm(
+        "pushfd\n\t", //Save original interrupt state
+        "cli\n\t", //Block interrupts to be safe, as we're modifying the stack alignment, making this a critical section
+        "push %%ebp\n\t", //Save original stack base pointer
+        "mov %%esp,%%ebp\n\t", //Save original stack alignment
+        "and -4,%%esp\n\t", //align stack
+        "pushfd\n\t", //Load...
+        "pop %%eax\n\t", //... old EFLAGS
+        "mov %%ebx,%%eax\n\t" //Copy of it for the result check
+        "xor %%eax,$200000\n\t", //Flip CPUID bit now
+        "push %%eax\n\t",
+        "popfd\n\t", //Store changed bit into flags
+        "pushfd\n\t", //New eflags back on the stack
+        "pop %%eax\n\t", //Get if it changed
+        "mov %%eax, %0\n\t", //Original eflags result
+        "mov %%ebx, %1\n\t", //Flipped eflags result
+        "mov %%ebp,%%esp\n\t", //Restore original stack alignment
+        "pop %%ebp\n\t", //Restore stack base pointer
+        "popfd", //Restore original interrupt state
+        : "=a" (res1), "=b" (res2)
+        :
+        : "=a", "=b");
+    return (((res1 ^ res2) & 0x200000)!=0); //Has the CPUID bit changed and is supported?
+    #else
+    return true; //Always assumed supported!
+    #endif
+}
+
 cpuid_result get_cpuid(uint32_t leaf, uint32_t subleaf)
 {
   cpuid_result res;
+  if (!cpuid_supported()) //CPUID not supported?
+  {
+      res.eax = res.ebx = reg.edx = res.ecx = 0; //Simply give empty result!
+      return res; //Give empty result!
+  }
+
+  //CPUID is supported!
   asm ("cpuid"
        : "=a" (res.eax), "=b" (res.ebx),
          "=d" (res.edx), "=c" (res.ecx)
@@ -53,3 +93,9 @@ bool has_smep()
     return get_cpuid_max_std_level() >= 7
         and (get_cpuid(0x7).ebx & (1 << 7));
 }
+
+bool has_pse()
+{
+    return get_cpuid_max_std_level() >= 1
+        and (get_cpuid(0x1).edx & (1 << 3));
+}
\ No newline at end of file
diff --git a/src/common/include/cpuid.hpp b/src/common/include/cpuid.hpp
index ebaee49..dcb9be7 100644
--- a/src/common/include/cpuid.hpp
+++ b/src/common/include/cpuid.hpp
@@ -29,3 +29,6 @@ bool has_nx();
 
 // Returns true, if the CPU reports being able to use SMEP.
 bool has_smep();
+
+// Returns true, if the CPU reports being able to use PSE.
+bool has_pse();
diff --git a/src/x86_32/arch.cpp b/src/x86_32/arch.cpp
index 829a6f1..e60cccc 100644
--- a/src/x86_32/arch.cpp
+++ b/src/x86_32/arch.cpp
@@ -51,15 +51,52 @@ static bool is_aligned(uint64_t v, int order)
 
 static void setup_paging()
 {
+  int pse_supported = has_pse(); //pse is supported on the CPU?
   uintptr_t istart = reinterpret_cast<uintptr_t>(_image_start);
   uintptr_t iend = reinterpret_cast<uintptr_t>(_image_end);
+  uintptr_t page_tables_start = iend+(1U<<22); //Point to the end of the image to store our page tables!
+  //For now just store it there if required (assuming enough memory is installed)!
+  if (page_tables_start & 0xFFF) //Make sure to start on the next 4KB boundary if needed!
+  {
+      page_tables_start = (page_table_start + 0xFFF) & ~0xFFF; //4KB boundary of next page!
+  }
 
   assert(is_aligned(istart, 22), "Image needs to start on large page boundary");
 
+  uintptr_t tablepos = page_tables_start; //For looping sub-page tables in the PDE entries!
+
   // Map our binary 1:1
   for (uintptr_t c = istart; c <= iend; c += (1U << 22)) {
-    uintptr_t idx = c >> 22;
-    pdt[idx] = c | PTE_P | PTE_W | PTE_PS;
+      uintptr_t idx;
+      uintptr_t p; //The physical location!
+      idx = c >> 22; //What index in the page directory
+      if (pse_supported) //PSE supported? Map 4MB page tables!
+      {
+          p = c | PTE_PS; //Directly mapped!
+      }
+      else //Map 4KB PDE page directories to their page tables
+      {
+          p = tablepos; //Page table position!
+          tablepos += (1 << 12); //Move in 4KB chunks!
+      }
+      pdt[idx] = PTE_P | PTE_W | p; //Map PDE to page table or page
+  }
+  // Map additional page tables, if required (non-PSE systems).
+  if (!pse_supported) //4KB page tables are required?
+  {
+      tablepos = page_table_start; //Generating pagetables here, requiring up to 4MB!
+      for (uintptr_t c = istart; c <= iend;) //Process our range again for the page tables!
+      {
+          uintptr_t m = c; //Where to start mapping 4MB to!
+          uint32_t* t = tablepos; //Backing page table in physical memory!
+          for (uintptr_t d = 0; d <= 1024;) //Map one 4MB page to linear memory
+          {
+              t[d] = m | PTE_P | PTE_W; //4KB PTE
+              m += 4096; //Mapped 4KB of memory!
+          }
+          tablepos += 4096; //Next page table to fill!
+          c += (1U << 22); //Mapped 4MB of memory
+      }
   }
 
   // Map user page
@@ -69,7 +106,10 @@ static void setup_paging()
   pdt[bit_select(32, 22, up)] = reinterpret_cast<uintptr_t>(user_pt) | PTE_U | PTE_P;
   user_pt[bit_select(22, 12, up)] = reinterpret_cast<uintptr_t>(get_user_page_backing()) | PTE_U | PTE_P;
 
-  set_cr4(get_cr4() | CR4_PSE | (has_smep()?CR4_SMEP:0));
+  if (pse_supported || has_smep()) //Enable either pse or smep and supported?
+  {
+      set_cr4(get_cr4() | (pse_supported ? CR4_PSE : 0) | (has_smep() ? CR4_SMEP : 0));
+  }
   set_cr3((uintptr_t)pdt);
   set_cr0(get_cr0() | CR0_PG | CR0_WP);
 }

From 10a6ad05a9bd91c379db72ffce4e5b6c23444153 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sun, 10 Mar 2024 04:44:21 +0100
Subject: [PATCH 03/32] - Fixed some compiler warnings.

---
 src/common/cpuid.cpp | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/src/common/cpuid.cpp b/src/common/cpuid.cpp
index 309ed17..e5bb4d8 100644
--- a/src/common/cpuid.cpp
+++ b/src/common/cpuid.cpp
@@ -8,24 +8,24 @@ bool cpuid_supported()
     //We need to check for the existence of CPUID on 32-bit platforms!
     unsigned int res1,res2;
     asm(
-        "pushfd\n\t", //Save original interrupt state
-        "cli\n\t", //Block interrupts to be safe, as we're modifying the stack alignment, making this a critical section
-        "push %%ebp\n\t", //Save original stack base pointer
-        "mov %%esp,%%ebp\n\t", //Save original stack alignment
-        "and -4,%%esp\n\t", //align stack
-        "pushfd\n\t", //Load...
-        "pop %%eax\n\t", //... old EFLAGS
+        "pushfd\n\t" //Save original interrupt state
+        "cli\n\t" //Block interrupts to be safe, as we're modifying the stack alignment, making this a critical section
+        "push %%ebp\n\t" //Save original stack base pointer
+        "mov %%esp,%%ebp\n\t" //Save original stack alignment
+        "and -4,%%esp\n\t" //align stack
+        "pushfd\n\t" //Load...
+        "pop %%eax\n\t" //... old EFLAGS
         "mov %%ebx,%%eax\n\t" //Copy of it for the result check
-        "xor %%eax,$200000\n\t", //Flip CPUID bit now
-        "push %%eax\n\t",
-        "popfd\n\t", //Store changed bit into flags
-        "pushfd\n\t", //New eflags back on the stack
-        "pop %%eax\n\t", //Get if it changed
-        "mov %%eax, %0\n\t", //Original eflags result
-        "mov %%ebx, %1\n\t", //Flipped eflags result
-        "mov %%ebp,%%esp\n\t", //Restore original stack alignment
-        "pop %%ebp\n\t", //Restore stack base pointer
-        "popfd", //Restore original interrupt state
+        "xor %%eax,$200000\n\t" //Flip CPUID bit now
+        "push %%eax\n\t"
+        "popfd\n\t" //Store changed bit into flags
+        "pushfd\n\t" //New eflags back on the stack
+        "pop %%eax\n\t" //Get if it changed
+        "mov %%eax, %0\n\t" //Original eflags result
+        "mov %%ebx, %1\n\t" //Flipped eflags result
+        "mov %%ebp,%%esp\n\t" //Restore original stack alignment
+        "pop %%ebp\n\t" //Restore stack base pointer
+        "popfd" //Restore original interrupt state
         : "=a" (res1), "=b" (res2)
         :
         : "=a", "=b");
@@ -40,7 +40,7 @@ cpuid_result get_cpuid(uint32_t leaf, uint32_t subleaf)
   cpuid_result res;
   if (!cpuid_supported()) //CPUID not supported?
   {
-      res.eax = res.ebx = reg.edx = res.ecx = 0; //Simply give empty result!
+      res.eax = res.ebx = res.edx = res.ecx = 0; //Simply give empty result!
       return res; //Give empty result!
   }
 

From 11b08593ba700f7a1e312178d96600e4d456ec89 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sun, 10 Mar 2024 04:46:43 +0100
Subject: [PATCH 04/32] - Improved CPUID check code.

---
 src/common/cpuid.cpp | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/common/cpuid.cpp b/src/common/cpuid.cpp
index e5bb4d8..47f7aca 100644
--- a/src/common/cpuid.cpp
+++ b/src/common/cpuid.cpp
@@ -26,9 +26,7 @@ bool cpuid_supported()
         "mov %%ebp,%%esp\n\t" //Restore original stack alignment
         "pop %%ebp\n\t" //Restore stack base pointer
         "popfd" //Restore original interrupt state
-        : "=a" (res1), "=b" (res2)
-        :
-        : "=a", "=b");
+        : "=a" (res1), "=b" (res2));
     return (((res1 ^ res2) & 0x200000)!=0); //Has the CPUID bit changed and is supported?
     #else
     return true; //Always assumed supported!

From 31a916c2da02d64ee37801d3684c5104b6563746 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sun, 10 Mar 2024 04:50:41 +0100
Subject: [PATCH 05/32] - Fixed issues with CPUID detection assembly code.

---
 src/common/cpuid.cpp | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/common/cpuid.cpp b/src/common/cpuid.cpp
index 47f7aca..ef960cd 100644
--- a/src/common/cpuid.cpp
+++ b/src/common/cpuid.cpp
@@ -8,24 +8,24 @@ bool cpuid_supported()
     //We need to check for the existence of CPUID on 32-bit platforms!
     unsigned int res1,res2;
     asm(
-        "pushfd\n\t" //Save original interrupt state
+        "pushfl\n\t" //Save original interrupt state
         "cli\n\t" //Block interrupts to be safe, as we're modifying the stack alignment, making this a critical section
         "push %%ebp\n\t" //Save original stack base pointer
         "mov %%esp,%%ebp\n\t" //Save original stack alignment
         "and -4,%%esp\n\t" //align stack
-        "pushfd\n\t" //Load...
+        "pushfl\n\t" //Load...
         "pop %%eax\n\t" //... old EFLAGS
         "mov %%ebx,%%eax\n\t" //Copy of it for the result check
-        "xor %%eax,$200000\n\t" //Flip CPUID bit now
+        "xor $200000,%%eax\n\t" //Flip CPUID bit now
         "push %%eax\n\t"
-        "popfd\n\t" //Store changed bit into flags
-        "pushfd\n\t" //New eflags back on the stack
+        "popfl\n\t" //Store changed bit into flags
+        "pushfl\n\t" //New eflags back on the stack
         "pop %%eax\n\t" //Get if it changed
         "mov %%eax, %0\n\t" //Original eflags result
         "mov %%ebx, %1\n\t" //Flipped eflags result
         "mov %%ebp,%%esp\n\t" //Restore original stack alignment
         "pop %%ebp\n\t" //Restore stack base pointer
-        "popfd" //Restore original interrupt state
+        "popfl" //Restore original interrupt state
         : "=a" (res1), "=b" (res2));
     return (((res1 ^ res2) & 0x200000)!=0); //Has the CPUID bit changed and is supported?
     #else

From e288d53438831be6fa84eae87ade477adfac6e30 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sun, 10 Mar 2024 05:01:40 +0100
Subject: [PATCH 06/32] - Implemented various code 4KB page table compilation
 bugfixes.

---
 src/x86_32/arch.cpp | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/src/x86_32/arch.cpp b/src/x86_32/arch.cpp
index e60cccc..1a03e0b 100644
--- a/src/x86_32/arch.cpp
+++ b/src/x86_32/arch.cpp
@@ -58,7 +58,7 @@ static void setup_paging()
   //For now just store it there if required (assuming enough memory is installed)!
   if (page_tables_start & 0xFFF) //Make sure to start on the next 4KB boundary if needed!
   {
-      page_tables_start = (page_table_start + 0xFFF) & ~0xFFF; //4KB boundary of next page!
+      page_tables_start = (page_tables_start + 0xFFF) & ~0xFFF; //4KB boundary of next page!
   }
 
   assert(is_aligned(istart, 22), "Image needs to start on large page boundary");
@@ -84,18 +84,17 @@ static void setup_paging()
   // Map additional page tables, if required (non-PSE systems).
   if (!pse_supported) //4KB page tables are required?
   {
-      tablepos = page_table_start; //Generating pagetables here, requiring up to 4MB!
-      for (uintptr_t c = istart; c <= iend;) //Process our range again for the page tables!
+      tablepos = page_tables_start; //Generating pagetables here, requiring up to 4MB!
+      for (uintptr_t c = istart; c <= iend; c += (1U << 22)) //Process our range again for the page tables!
       {
           uintptr_t m = c; //Where to start mapping 4MB to!
-          uint32_t* t = tablepos; //Backing page table in physical memory!
+          uint32_t* t = reinterpret_cast<uint32_t*>tablepos; //Backing page table in physical memory!
           for (uintptr_t d = 0; d <= 1024;) //Map one 4MB page to linear memory
           {
-              t[d] = m | PTE_P | PTE_W; //4KB PTE
+              t[d++] = m | PTE_P | PTE_W; //4KB PTE
               m += 4096; //Mapped 4KB of memory!
           }
           tablepos += 4096; //Next page table to fill!
-          c += (1U << 22); //Mapped 4MB of memory
       }
   }
 

From 23fc0dc92d960a866717f92b2dbdadcf7a560582 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sun, 10 Mar 2024 05:03:31 +0100
Subject: [PATCH 07/32] - Fixed invalid reinterpret_cast on 4KB page table
 pointer.

---
 src/x86_32/arch.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/x86_32/arch.cpp b/src/x86_32/arch.cpp
index 1a03e0b..5aab872 100644
--- a/src/x86_32/arch.cpp
+++ b/src/x86_32/arch.cpp
@@ -88,7 +88,7 @@ static void setup_paging()
       for (uintptr_t c = istart; c <= iend; c += (1U << 22)) //Process our range again for the page tables!
       {
           uintptr_t m = c; //Where to start mapping 4MB to!
-          uint32_t* t = reinterpret_cast<uint32_t*>tablepos; //Backing page table in physical memory!
+          uint32_t* t = reinterpret_cast<uint32_t*>(tablepos); //Backing page table in physical memory!
           for (uintptr_t d = 0; d <= 1024;) //Map one 4MB page to linear memory
           {
               t[d++] = m | PTE_P | PTE_W; //4KB PTE

From 7e9dcd5d3ab4902323a39f251eab4620a5ddc895 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sun, 10 Mar 2024 06:40:01 +0100
Subject: [PATCH 08/32] - Fixed issues with the assembly code for detecting
 CPUID support.

---
 src/common/cpuid.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/common/cpuid.cpp b/src/common/cpuid.cpp
index ef960cd..4c661ec 100644
--- a/src/common/cpuid.cpp
+++ b/src/common/cpuid.cpp
@@ -15,14 +15,14 @@ bool cpuid_supported()
         "and -4,%%esp\n\t" //align stack
         "pushfl\n\t" //Load...
         "pop %%eax\n\t" //... old EFLAGS
-        "mov %%ebx,%%eax\n\t" //Copy of it for the result check
-        "xor $200000,%%eax\n\t" //Flip CPUID bit now
+        "mov %%eax,%%ebx\n\t" //Copy of it for the result check
+        "xor $0x200000,%%eax\n\t" //Flip CPUID bit now
         "push %%eax\n\t"
         "popfl\n\t" //Store changed bit into flags
         "pushfl\n\t" //New eflags back on the stack
         "pop %%eax\n\t" //Get if it changed
-        "mov %%eax, %0\n\t" //Original eflags result
-        "mov %%ebx, %1\n\t" //Flipped eflags result
+        "mov %%eax, %0\n\t" //Flipped eflags result
+        "mov %%ebx, %1\n\t" //Original eflags result
         "mov %%ebp,%%esp\n\t" //Restore original stack alignment
         "pop %%ebp\n\t" //Restore stack base pointer
         "popfl" //Restore original interrupt state

From 5a5db401ff339422153e73e068e69fbdf691dc6b Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sun, 10 Mar 2024 07:12:54 +0100
Subject: [PATCH 09/32] - Fixed masking of ESP to align the stack when checking
 for CPUID capability.

---
 src/common/cpuid.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/common/cpuid.cpp b/src/common/cpuid.cpp
index 4c661ec..2210b38 100644
--- a/src/common/cpuid.cpp
+++ b/src/common/cpuid.cpp
@@ -12,7 +12,7 @@ bool cpuid_supported()
         "cli\n\t" //Block interrupts to be safe, as we're modifying the stack alignment, making this a critical section
         "push %%ebp\n\t" //Save original stack base pointer
         "mov %%esp,%%ebp\n\t" //Save original stack alignment
-        "and -4,%%esp\n\t" //align stack
+        "and $-4,%%esp\n\t" //align stack
         "pushfl\n\t" //Load...
         "pop %%eax\n\t" //... old EFLAGS
         "mov %%eax,%%ebx\n\t" //Copy of it for the result check

From 24b98d463400a686848e5db97236960469d9c283 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sun, 10 Mar 2024 08:09:44 +0100
Subject: [PATCH 10/32] - Added support for CPUs without the alignment flag
 supported to not set the WP bit in CR0.

---
 src/common/cpuid.cpp         | 31 +++++++++++++++++++++++++++++++
 src/common/include/cpuid.hpp |  3 +++
 src/x86_32/arch.cpp          |  5 +++--
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/src/common/cpuid.cpp b/src/common/cpuid.cpp
index 2210b38..3618fc9 100644
--- a/src/common/cpuid.cpp
+++ b/src/common/cpuid.cpp
@@ -96,4 +96,35 @@ bool has_pse()
 {
     return get_cpuid_max_std_level() >= 1
         and (get_cpuid(0x1).edx & (1 << 3));
+}
+
+bool has_wp()
+{
+#ifndef __x86_64__
+    //We need to check for the existence of CR0 WP on 32-bit platforms!
+    unsigned int res1, res2;
+    asm(
+        "pushfl\n\t" //Save original interrupt state
+        "cli\n\t" //Block interrupts to be safe, as we're modifying the stack alignment, making this a critical section
+        "push %%ebp\n\t" //Save original stack base pointer
+        "mov %%esp,%%ebp\n\t" //Save original stack alignment
+        "and $-4,%%esp\n\t" //align stack. Important to prevent faulting on this down the road!
+        "pushfl\n\t" //Load...
+        "pop %%eax\n\t" //... old EFLAGS
+        "mov %%eax,%%ebx\n\t" //Copy of it for the result check
+        "xor $0x40000,%%eax\n\t" //Flip AC bit now
+        "push %%eax\n\t"
+        "popfl\n\t" //Store changed bit into flags
+        "pushfl\n\t" //New eflags back on the stack
+        "pop %%eax\n\t" //Get if it changed
+        "mov %%eax, %0\n\t" //Flipped eflags result
+        "mov %%ebx, %1\n\t" //Original eflags result
+        "mov %%ebp,%%esp\n\t" //Restore original stack alignment
+        "pop %%ebp\n\t" //Restore stack base pointer
+        "popfl" //Restore original interrupt state
+        : "=a" (res1), "=b" (res2));
+    return (((res1 ^ res2) & 0x40000) != 0); //Has the AC bit changed and is supported (indicates WP bit is supported)?
+#else
+    return true; //Always assumed supported!
+#endif
 }
\ No newline at end of file
diff --git a/src/common/include/cpuid.hpp b/src/common/include/cpuid.hpp
index dcb9be7..9bb4148 100644
--- a/src/common/include/cpuid.hpp
+++ b/src/common/include/cpuid.hpp
@@ -32,3 +32,6 @@ bool has_smep();
 
 // Returns true, if the CPU reports being able to use PSE.
 bool has_pse();
+
+// Returns true, if the CPU reports being able to use the WP bit in CR0.
+bool has_wp();
diff --git a/src/x86_32/arch.cpp b/src/x86_32/arch.cpp
index 5aab872..342c0ec 100644
--- a/src/x86_32/arch.cpp
+++ b/src/x86_32/arch.cpp
@@ -51,7 +51,8 @@ static bool is_aligned(uint64_t v, int order)
 
 static void setup_paging()
 {
-  int pse_supported = has_pse(); //pse is supported on the CPU?
+  bool pse_supported = has_pse(); //pse is supported on the CPU?
+  bool wp_supported = has_wp(); //wp is supported on the CPU?
   uintptr_t istart = reinterpret_cast<uintptr_t>(_image_start);
   uintptr_t iend = reinterpret_cast<uintptr_t>(_image_end);
   uintptr_t page_tables_start = iend+(1U<<22); //Point to the end of the image to store our page tables!
@@ -110,7 +111,7 @@ static void setup_paging()
       set_cr4(get_cr4() | (pse_supported ? CR4_PSE : 0) | (has_smep() ? CR4_SMEP : 0));
   }
   set_cr3((uintptr_t)pdt);
-  set_cr0(get_cr0() | CR0_PG | CR0_WP);
+  set_cr0(get_cr0() | CR0_PG | (wp_supported?CR0_WP:0));
 }
 
 static void setup_gdt()

From ce99ac006ea7e0b4066bc3a7478e1f5c77328b54 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Sun, 10 Mar 2024 13:08:36 +0100
Subject: [PATCH 11/32] - Compile for i386 instead of i686.

---
 src/SConstruct | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/SConstruct b/src/SConstruct
index 19988c6..4e134ce 100644
--- a/src/SConstruct
+++ b/src/SConstruct
@@ -35,7 +35,7 @@ bare64_env.Append(CCFLAGS=" -m64 -march=x86-64 -mno-red-zone",
                   ASFLAGS=" -felf64")
 
 bare32_env = common_bare_env.Clone(ARCH_NAME="x86_32")
-bare32_env.Append(CCFLAGS=" -m32 -march=i686 -mregparm=3 -fomit-frame-pointer",
+bare32_env.Append(CCFLAGS=" -m32 -march=i386 -mregparm=3 -fomit-frame-pointer",
                   ASFLAGS=" -felf32")
 
 bins = []

From ffa417c53df4976c3d6586e0d5272b77d126b6b8 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Mon, 11 Mar 2024 20:26:06 +0100
Subject: [PATCH 12/32] - There are no REX prefixes on x86.

---
 src/common/search.cpp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index 62831c4..14473fa 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -32,10 +32,12 @@ static constexpr int opcode_to_prefix_group(uint8_t byte)
   case 0x67:                    // address size override
     group = 3;
     break;
+#ifndef __x86_64__
   case 0x40 ... 0x4F:           // REX prefixes
     group = 4;
     break;
   }
+#endif
 
   return group;
 }

From a53485ca4fd4628c8c7f64680cbb62167634687e Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Mon, 11 Mar 2024 20:39:41 +0100
Subject: [PATCH 13/32] - Fixed x64 vs x86 REX prefixes.

---
 src/common/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index 14473fa..7a41d8d 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -32,7 +32,7 @@ static constexpr int opcode_to_prefix_group(uint8_t byte)
   case 0x67:                    // address size override
     group = 3;
     break;
-#ifndef __x86_64__
+#ifdef __x86_64__
   case 0x40 ... 0x4F:           // REX prefixes
     group = 4;
     break;

From c322510584fee84226c94b0419202fbf04b7f56e Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Mon, 11 Mar 2024 21:12:49 +0100
Subject: [PATCH 14/32] - Fixed REX prefix code to compile again on x86.

---
 src/common/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index 7a41d8d..da2bea1 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -36,8 +36,8 @@ static constexpr int opcode_to_prefix_group(uint8_t byte)
   case 0x40 ... 0x4F:           // REX prefixes
     group = 4;
     break;
-  }
 #endif
+  }
 
   return group;
 }

From b5c886deac04091a3a71206570170f159c2d8d3e Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 14:32:24 +0100
Subject: [PATCH 15/32] Update search.hpp

Added support for used prefixes.
---
 src/common/include/search.hpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/common/include/search.hpp b/src/common/include/search.hpp
index 455b7b7..be0729b 100644
--- a/src/common/include/search.hpp
+++ b/src/common/include/search.hpp
@@ -18,6 +18,7 @@ class search_engine {
   size_t increment_at_ = 0;
 
   const size_t max_prefixes_;
+  const size_t used_prefixes_;
 
 public:
 
@@ -37,7 +38,7 @@ class search_engine {
     return current_;
   }
 
-  search_engine(size_t max_prefixes = 0, instruction_bytes const &start = {})
-    : current_(start), max_prefixes_(max_prefixes)
+  search_engine(size_t max_prefixes = 0, size_t used_prefixes = 0xFF, instruction_bytes const &start = {})
+    : current_(start), max_prefixes_(max_prefixes), used_prefixes_(used_prefixes)
   {}
 };

From 72305e1a09cec2340142caa6931257d28f803a69 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 14:37:18 +0100
Subject: [PATCH 16/32] - Pass detect and used prefixes settings to the search
 engine.

---
 src/main.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/main.cpp b/src/main.cpp
index 78a0415..db62ab2 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -140,6 +140,12 @@ struct options {
 
   // After how many instructions do we stop. Zero means don't stop.
   size_t stop_after = 0;
+
+  // What prefixes to use. Zero means no prefixes are valid to use. The bits of the number are the opcode groups.
+  size_t used_prefixes = 0xFF;
+
+  // What prefixes to detect. Zero means no prefixes are valid. The bits of the number are the opcode groups.
+  size_t detect_prefixes = 0xFF;
 };
 
 // This will modify cmdline.
@@ -182,7 +188,7 @@ void start(cpu_features const &features, char *cmdline)
   if (options.stop_after)
     format(">>> Stopping after ", options.stop_after, " execution attemps.\n");
 
-  search_engine search { options.prefixes };
+  search_engine search { options.prefixes, options.used_prefixes, options.detect_prefixes };
   execution_attempt last_attempt;
 
   do {

From 9929cff11753ab45c4644ba1689a996118c307a3 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 14:39:54 +0100
Subject: [PATCH 17/32] Update search.hpp

- Full used and detected prefixes storage in the search engine.
---
 src/common/include/search.hpp | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/common/include/search.hpp b/src/common/include/search.hpp
index be0729b..c28c29e 100644
--- a/src/common/include/search.hpp
+++ b/src/common/include/search.hpp
@@ -17,8 +17,9 @@ class search_engine {
   instruction_bytes current_;
   size_t increment_at_ = 0;
 
-  const size_t max_prefixes_;
-  const size_t used_prefixes_;
+  const size_t max_prefixes_; //How many prefixes to use at once.
+  const size_t used_prefixes_; //What prefixes to scan through.
+  const size_t detect_prefixes_; //What prefixes to detect as prefixes.
 
 public:
 
@@ -38,7 +39,7 @@ class search_engine {
     return current_;
   }
 
-  search_engine(size_t max_prefixes = 0, size_t used_prefixes = 0xFF, instruction_bytes const &start = {})
-    : current_(start), max_prefixes_(max_prefixes), used_prefixes_(used_prefixes)
+  search_engine(size_t max_prefixes = 0, size_t used_prefixes = 0xFF, size_t detect_prefixes = 0xFF, instruction_bytes const &start = {})
+    : current_(start), max_prefixes_(max_prefixes), used_prefixes_(used_prefixes), detect_prefixes_(detect_prefixes)
   {}
 };

From e81dbc8bbbdda15b362f90e165f7cc38bcb2b992 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 14:47:10 +0100
Subject: [PATCH 18/32] Update search.cpp

Implemented the filter on detecting of prefixes.
---
 src/common/search.cpp | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index da2bea1..68c2555 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -16,7 +16,10 @@ static constexpr int opcode_to_prefix_group(uint8_t byte)
   case 0xF0:                    // LOCK
   case 0xF2:                    // REPNE
   case 0xF3:                    // REP
-    group = 0;
+    if (detect_prefixes & (1<<0)) //To detect?
+    {
+      group = 0;
+    }
     break;
   case 0x2E:                    // CS
   case 0x36:                    // SS
@@ -24,19 +27,29 @@ static constexpr int opcode_to_prefix_group(uint8_t byte)
   case 0x26:                    // ES
   case 0x64:                    // FS
   case 0x65:                    // GS
+    if (detect_prefixes & (1<<0)) //To detect?
+    {
     group = 1;
+    }
     break;
   case 0x66:                    // operand size override
+    if (detect_prefixes & (1<<1)) //To detect?
+    {
     group = 2;
+    }
     break;
   case 0x67:                    // address size override
-    group = 3;
+    if (detect_prefixes & (1<<2)) //To detect?
+    {
+      group = 3;
+    }
     break;
-#ifdef __x86_64__
   case 0x40 ... 0x4F:           // REX prefixes
-    group = 4;
+    if (detect_prefixes & (1<<3)) //To detect?
+    {
+      group = 4;
+    }
     break;
-#endif
   }
 
   return group;
@@ -77,6 +90,7 @@ struct prefix_state {
       if (c >= 2)
         return true;
     }
+    //TODO: detect used_prefixed and filter them out.
 
     return false;
   }

From 379731b8069256666141d768eb3ea62c5e958660 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 14:48:10 +0100
Subject: [PATCH 19/32] Update search.cpp

- Fixed detecting of prefixes.
---
 src/common/search.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index 68c2555..f49c125 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -27,25 +27,25 @@ static constexpr int opcode_to_prefix_group(uint8_t byte)
   case 0x26:                    // ES
   case 0x64:                    // FS
   case 0x65:                    // GS
-    if (detect_prefixes & (1<<0)) //To detect?
+    if (detect_prefixes & (1<<1)) //To detect?
     {
     group = 1;
     }
     break;
   case 0x66:                    // operand size override
-    if (detect_prefixes & (1<<1)) //To detect?
+    if (detect_prefixes & (1<<2)) //To detect?
     {
     group = 2;
     }
     break;
   case 0x67:                    // address size override
-    if (detect_prefixes & (1<<2)) //To detect?
+    if (detect_prefixes & (1<<3)) //To detect?
     {
       group = 3;
     }
     break;
   case 0x40 ... 0x4F:           // REX prefixes
-    if (detect_prefixes & (1<<3)) //To detect?
+    if (detect_prefixes & (1<<4)) //To detect?
     {
       group = 4;
     }

From 7e2159ed0c14925a2e741ba9508a00962b240cb0 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 15:48:39 +0100
Subject: [PATCH 20/32] Update search.cpp

Implemented prefix groups not to be used if specified to exclude.
---
 src/common/search.cpp | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index f49c125..68bca87 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -29,13 +29,13 @@ static constexpr int opcode_to_prefix_group(uint8_t byte)
   case 0x65:                    // GS
     if (detect_prefixes & (1<<1)) //To detect?
     {
-    group = 1;
+      group = 1;
     }
     break;
   case 0x66:                    // operand size override
     if (detect_prefixes & (1<<2)) //To detect?
     {
-    group = 2;
+      group = 2;
     }
     break;
   case 0x67:                    // address size override
@@ -90,8 +90,17 @@ struct prefix_state {
       if (c >= 2)
         return true;
     }
-    //TODO: detect used_prefixed and filter them out.
+    
+    return false;
+  }
 
+  bool has_unused_prefixes() const
+  {
+    //Detect used_prefixes and filter them out.
+    for (size_t i = 0; i < array_size(count); i++)
+      if (count[i] and ((used_prefixes&(1<<i))==0)) //Prefix not to be used?
+        return true;
+    
     return false;
   }
 
@@ -158,8 +167,10 @@ bool search_engine::find_next_candidate()
 
   // Duplicated prefixes make the search space explode without generating
   // insight. Also enforce order on prefixes to further reduce search space.
+  // And also filter out prefixes that are declared not to be used.
   if (state.total_prefix_bytes() > max_prefixes_ or
       state.has_duplicated_prefixes() or
+      state.has_unused_prefixes() or
       not state.has_ordered_prefixes()) {
     goto again;
   }

From 4dbe1a2ab7b4ccccadf66722afe901dd7216cc87 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 15:54:03 +0100
Subject: [PATCH 21/32] Update main.cpp

- Implemented proper parsing of used and detected prefixes on the command line.
---
 src/main.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/main.cpp b/src/main.cpp
index db62ab2..1b11d95 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -164,6 +164,10 @@ static options parse_and_destroy_cmdline(char *cmdline)
 
     if (strcmp(key, "prefixes") == 0)
       res.prefixes = atoi(value);
+    if (strcmp(key, "used_prefixes") == 0)
+      res.used_prefixes = atoi(value);
+    if (strcmp(key, "detect_prefixes") == 0)
+      res.detect_prefixes = atoi(value);
     if (strcmp(key, "stop_after") == 0)
       res.stop_after = atoi(value);
   }

From 2ffd34e1093a010e4e12541ded04380d251a4a9e Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 16:21:57 +0100
Subject: [PATCH 22/32] - Optimized unused prefix check using a variable to
 shift. - Fixed detect_prefixes and used_prefixes variable names.

---
 src/common/search.cpp | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index 68bca87..a882a1f 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -16,7 +16,7 @@ static constexpr int opcode_to_prefix_group(uint8_t byte)
   case 0xF0:                    // LOCK
   case 0xF2:                    // REPNE
   case 0xF3:                    // REP
-    if (detect_prefixes & (1<<0)) //To detect?
+    if (detect_prefixes_ & (1<<0)) //To detect?
     {
       group = 0;
     }
@@ -27,25 +27,25 @@ static constexpr int opcode_to_prefix_group(uint8_t byte)
   case 0x26:                    // ES
   case 0x64:                    // FS
   case 0x65:                    // GS
-    if (detect_prefixes & (1<<1)) //To detect?
+    if (detect_prefixes_ & (1<<1)) //To detect?
     {
       group = 1;
     }
     break;
   case 0x66:                    // operand size override
-    if (detect_prefixes & (1<<2)) //To detect?
+    if (detect_prefixes_ & (1<<2)) //To detect?
     {
       group = 2;
     }
     break;
   case 0x67:                    // address size override
-    if (detect_prefixes & (1<<3)) //To detect?
+    if (detect_prefixes_ & (1<<3)) //To detect?
     {
       group = 3;
     }
     break;
   case 0x40 ... 0x4F:           // REX prefixes
-    if (detect_prefixes & (1<<4)) //To detect?
+    if (detect_prefixes_ & (1<<4)) //To detect?
     {
       group = 4;
     }
@@ -97,9 +97,11 @@ struct prefix_state {
   bool has_unused_prefixes() const
   {
     //Detect used_prefixes and filter them out.
-    for (size_t i = 0; i < array_size(count); i++)
-      if (count[i] and ((used_prefixes&(1<<i))==0)) //Prefix not to be used?
-        return true;
+      for (size_t i = 0, size_t b = 1;; i < array_size(count); i++, b <<= 1)
+      {
+          if (count[i] and ((used_prefixes_ & b) == 0)) //Prefix not to be used?
+              return true;
+      }
     
     return false;
   }

From a39f50ca4aaed69439b25bd497331fd823d6a89e Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 16:42:05 +0100
Subject: [PATCH 23/32] - Moved the prefix group LUT into the search engine
 class. - Made the prefix group LUT depend on the prefixes specified.

---
 src/common/include/search.hpp |  9 ++++++++-
 src/common/search.cpp         | 14 ++++----------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/src/common/include/search.hpp b/src/common/include/search.hpp
index c28c29e..1e4aa04 100644
--- a/src/common/include/search.hpp
+++ b/src/common/include/search.hpp
@@ -13,8 +13,15 @@ struct instruction_bytes {
   {}
 };
 
+typedef struct prefix_lut {
+    int8_t data[256];
+};
+
+static constexpr prefix_lut create_prefix_group_lut(uint8_t detect_prefixes_); //Prototype!
+
 class search_engine {
   instruction_bytes current_;
+  prefix_lut prefix_group_lut;
   size_t increment_at_ = 0;
 
   const size_t max_prefixes_; //How many prefixes to use at once.
@@ -40,6 +47,6 @@ class search_engine {
   }
 
   search_engine(size_t max_prefixes = 0, size_t used_prefixes = 0xFF, size_t detect_prefixes = 0xFF, instruction_bytes const &start = {})
-    : current_(start), max_prefixes_(max_prefixes), used_prefixes_(used_prefixes), detect_prefixes_(detect_prefixes)
+      : current_(start), max_prefixes_(max_prefixes), used_prefixes_(used_prefixes), detect_prefixes_(detect_prefixes), prefix_group_lut{create_prefix_group_lut(detect_prefixes)}
   {}
 };
diff --git a/src/common/search.cpp b/src/common/search.cpp
index a882a1f..57cad82 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -4,11 +4,7 @@
 #include "search.hpp"
 #include "util.hpp"
 
-struct prefix_lut {
-  int8_t data[256];
-};
-
-static constexpr int opcode_to_prefix_group(uint8_t byte)
+static constexpr int opcode_to_prefix_group(uint8_t byte, uint8_t detect_prefixes_)
 {
   int group = -1;
 
@@ -55,19 +51,17 @@ static constexpr int opcode_to_prefix_group(uint8_t byte)
   return group;
 }
 
-static constexpr prefix_lut create_prefix_group_lut()
+static constexpr prefix_lut create_prefix_group_lut(uint8_t detect_prefixes_)
 {
   prefix_lut group_lut {};
 
   for (size_t i = 0; i < array_size(group_lut.data); i++) {
-    group_lut.data[i] = (int8_t)opcode_to_prefix_group((uint8_t)i);
+    group_lut.data[i] = (int8_t)opcode_to_prefix_group((uint8_t)i,detect_prefixes_);
   }
 
   return group_lut;
 }
 
-static prefix_lut prefix_group_lut {create_prefix_group_lut()};
-
 // Encapsulates which prefixes are there, where and how many there are.
 struct prefix_state {
   uint8_t count[5] {};          // Count of prefixes in each group.
@@ -97,7 +91,7 @@ struct prefix_state {
   bool has_unused_prefixes() const
   {
     //Detect used_prefixes and filter them out.
-      for (size_t i = 0, size_t b = 1;; i < array_size(count); i++, b <<= 1)
+      for (size_t i = 0, size_t b = 1; i < array_size(count); i++, b <<= 1)
       {
           if (count[i] and ((used_prefixes_ & b) == 0)) //Prefix not to be used?
               return true;

From 64dd5cb5638bb70359580b9406fe90161745f889 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 16:45:55 +0100
Subject: [PATCH 24/32] - More code fixes.

---
 src/common/include/search.hpp | 4 ++--
 src/common/search.cpp         | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/common/include/search.hpp b/src/common/include/search.hpp
index 1e4aa04..829d11a 100644
--- a/src/common/include/search.hpp
+++ b/src/common/include/search.hpp
@@ -13,9 +13,9 @@ struct instruction_bytes {
   {}
 };
 
-typedef struct prefix_lut {
+typedef struct {
     int8_t data[256];
-};
+} prefix_lut;
 
 static constexpr prefix_lut create_prefix_group_lut(uint8_t detect_prefixes_); //Prototype!
 
diff --git a/src/common/search.cpp b/src/common/search.cpp
index 57cad82..55fb12b 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -91,7 +91,8 @@ struct prefix_state {
   bool has_unused_prefixes() const
   {
     //Detect used_prefixes and filter them out.
-      for (size_t i = 0, size_t b = 1; i < array_size(count); i++, b <<= 1)
+      size_t b = 1;
+      for (size_t i = 0; i < array_size(count); i++, b <<= 1)
       {
           if (count[i] and ((used_prefixes_ & b) == 0)) //Prefix not to be used?
               return true;

From f068892389263068468713b1907763c5a1749be6 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 16:52:05 +0100
Subject: [PATCH 25/32] - Fixed prefix LUT initialization.

---
 src/common/include/search.hpp | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/common/include/search.hpp b/src/common/include/search.hpp
index 829d11a..b6c7217 100644
--- a/src/common/include/search.hpp
+++ b/src/common/include/search.hpp
@@ -21,12 +21,10 @@ static constexpr prefix_lut create_prefix_group_lut(uint8_t detect_prefixes_); /
 
 class search_engine {
   instruction_bytes current_;
-  prefix_lut prefix_group_lut;
   size_t increment_at_ = 0;
 
   const size_t max_prefixes_; //How many prefixes to use at once.
   const size_t used_prefixes_; //What prefixes to scan through.
-  const size_t detect_prefixes_; //What prefixes to detect as prefixes.
 
 public:
 
@@ -47,6 +45,6 @@ class search_engine {
   }
 
   search_engine(size_t max_prefixes = 0, size_t used_prefixes = 0xFF, size_t detect_prefixes = 0xFF, instruction_bytes const &start = {})
-      : current_(start), max_prefixes_(max_prefixes), used_prefixes_(used_prefixes), detect_prefixes_(detect_prefixes), prefix_group_lut{create_prefix_group_lut(detect_prefixes)}
+      : current_(start), max_prefixes_(max_prefixes), used_prefixes_(used_prefixes), prefix_group_lut{create_prefix_group_lut(detect_prefixes)}
   {}
 };

From dba24809e33da5ad7a7d02adc3e14b5826d8f29a Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 17:14:45 +0100
Subject: [PATCH 26/32] - Modified the prefix group LUT into a class.

---
 src/common/include/search.hpp | 12 +++++++-----
 src/common/search.cpp         | 14 +++++---------
 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/src/common/include/search.hpp b/src/common/include/search.hpp
index b6c7217..1805b2f 100644
--- a/src/common/include/search.hpp
+++ b/src/common/include/search.hpp
@@ -13,18 +13,20 @@ struct instruction_bytes {
   {}
 };
 
-typedef struct {
+class prefix_group_lut {
+public:
     int8_t data[256];
-} prefix_lut;
 
-static constexpr prefix_lut create_prefix_group_lut(uint8_t detect_prefixes_); //Prototype!
+    prefix_group_lut(uint8_t detect_prefixes_); //Prototype!
+};
 
-class search_engine {
+class search_engine :  {
   instruction_bytes current_;
   size_t increment_at_ = 0;
 
   const size_t max_prefixes_; //How many prefixes to use at once.
   const size_t used_prefixes_; //What prefixes to scan through.
+  prefix_group_lut group_lut_; //What group lut to use!
 
 public:
 
@@ -45,6 +47,6 @@ class search_engine {
   }
 
   search_engine(size_t max_prefixes = 0, size_t used_prefixes = 0xFF, size_t detect_prefixes = 0xFF, instruction_bytes const &start = {})
-      : current_(start), max_prefixes_(max_prefixes), used_prefixes_(used_prefixes), prefix_group_lut{create_prefix_group_lut(detect_prefixes)}
+      : current_(start), max_prefixes_(max_prefixes), used_prefixes_(used_prefixes), group_lut_(detect_prefixes)
   {}
 };
diff --git a/src/common/search.cpp b/src/common/search.cpp
index 55fb12b..2a80764 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -4,7 +4,7 @@
 #include "search.hpp"
 #include "util.hpp"
 
-static constexpr int opcode_to_prefix_group(uint8_t byte, uint8_t detect_prefixes_)
+static constexpr int opcode_to_prefix_group(uint8_t byte, size_t detect_prefixes_)
 {
   int group = -1;
 
@@ -51,15 +51,11 @@ static constexpr int opcode_to_prefix_group(uint8_t byte, uint8_t detect_prefixe
   return group;
 }
 
-static constexpr prefix_lut create_prefix_group_lut(uint8_t detect_prefixes_)
+prefix_group_lut::prefix_group_lut(size_t detect_prefixes_)
 {
-  prefix_lut group_lut {};
-
-  for (size_t i = 0; i < array_size(group_lut.data); i++) {
-    group_lut.data[i] = (int8_t)opcode_to_prefix_group((uint8_t)i,detect_prefixes_);
+  for (size_t i = 0; i < array_size(data); i++) {
+    data[i] = (int8_t)opcode_to_prefix_group((uint8_t)i,detect_prefixes_);
   }
-
-  return group_lut;
 }
 
 // Encapsulates which prefixes are there, where and how many there are.
@@ -123,7 +119,7 @@ static prefix_state analyze_prefixes(instruction_bytes const &instr)
   prefix_state state;
 
   for (size_t i = 0; i < sizeof(instr.raw); i++) {
-    int group = prefix_group_lut.data[instr.raw[i]];
+    int group = group_lut_.data[instr.raw[i]];
     if (group < 0)
       break;
 

From d217a479a8028856381a1efea94baf16ae486b06 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 17:15:34 +0100
Subject: [PATCH 27/32] - Fixed search engine class.

---
 src/common/include/search.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/common/include/search.hpp b/src/common/include/search.hpp
index 1805b2f..ba76998 100644
--- a/src/common/include/search.hpp
+++ b/src/common/include/search.hpp
@@ -20,7 +20,7 @@ class prefix_group_lut {
     prefix_group_lut(uint8_t detect_prefixes_); //Prototype!
 };
 
-class search_engine :  {
+class search_engine {
   instruction_bytes current_;
   size_t increment_at_ = 0;
 

From 86e7ce84e00c1e2701fda863a2c7c47058bf5511 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 17:21:19 +0100
Subject: [PATCH 28/32] - Improved prefix_group_lut initialization.

---
 src/common/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index 2a80764..ae3a56a 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -51,7 +51,7 @@ static constexpr int opcode_to_prefix_group(uint8_t byte, size_t detect_prefixes
   return group;
 }
 
-prefix_group_lut::prefix_group_lut(size_t detect_prefixes_)
+constexpr prefix_group_lut::prefix_group_lut(size_t detect_prefixes_)
 {
   for (size_t i = 0; i < array_size(data); i++) {
     data[i] = (int8_t)opcode_to_prefix_group((uint8_t)i,detect_prefixes_);

From 2e65fadc13e2f3e616abdec68ea37839412d6ac1 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 17:24:37 +0100
Subject: [PATCH 29/32] - More prefix group LUT code fixes.

---
 src/common/include/search.hpp | 2 +-
 src/common/search.cpp         | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/common/include/search.hpp b/src/common/include/search.hpp
index ba76998..2e320f0 100644
--- a/src/common/include/search.hpp
+++ b/src/common/include/search.hpp
@@ -17,7 +17,7 @@ class prefix_group_lut {
 public:
     int8_t data[256];
 
-    prefix_group_lut(uint8_t detect_prefixes_); //Prototype!
+    prefix_group_lut(size_t detect_prefixes_); //Prototype!
 };
 
 class search_engine {
diff --git a/src/common/search.cpp b/src/common/search.cpp
index ae3a56a..2a80764 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -51,7 +51,7 @@ static constexpr int opcode_to_prefix_group(uint8_t byte, size_t detect_prefixes
   return group;
 }
 
-constexpr prefix_group_lut::prefix_group_lut(size_t detect_prefixes_)
+prefix_group_lut::prefix_group_lut(size_t detect_prefixes_)
 {
   for (size_t i = 0; i < array_size(data); i++) {
     data[i] = (int8_t)opcode_to_prefix_group((uint8_t)i,detect_prefixes_);

From 9203312f850435dd4185421e817d39f7af1c30c6 Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 17:27:03 +0100
Subject: [PATCH 30/32] - Fixed unused prefixes detection.

---
 src/common/search.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index 2a80764..6f03319 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -84,7 +84,7 @@ struct prefix_state {
     return false;
   }
 
-  bool has_unused_prefixes() const
+  bool search_engine::has_unused_prefixes(size_t used_prefixes_) const
   {
     //Detect used_prefixes and filter them out.
       size_t b = 1;
@@ -163,7 +163,7 @@ bool search_engine::find_next_candidate()
   // And also filter out prefixes that are declared not to be used.
   if (state.total_prefix_bytes() > max_prefixes_ or
       state.has_duplicated_prefixes() or
-      state.has_unused_prefixes() or
+      state.has_unused_prefixes(used_prefixes_) or
       not state.has_ordered_prefixes()) {
     goto again;
   }

From 34e58a1f6e1514d4b156c141e1adc18e228e7e9c Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 17:27:58 +0100
Subject: [PATCH 31/32] - Restored unused prefix detection code.

---
 src/common/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index 6f03319..718cffb 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -84,7 +84,7 @@ struct prefix_state {
     return false;
   }
 
-  bool search_engine::has_unused_prefixes(size_t used_prefixes_) const
+  bool has_unused_prefixes(size_t used_prefixes_) const
   {
     //Detect used_prefixes and filter them out.
       size_t b = 1;

From 576c00e8eeb10464b318458334a595ebd824f47d Mon Sep 17 00:00:00 2001
From: superfury <superfury@live.nl>
Date: Wed, 13 Mar 2024 17:30:29 +0100
Subject: [PATCH 32/32] - Fixed group LUT lookups.

---
 src/common/search.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/common/search.cpp b/src/common/search.cpp
index 718cffb..15d3e65 100644
--- a/src/common/search.cpp
+++ b/src/common/search.cpp
@@ -114,7 +114,7 @@ struct prefix_state {
   }
 };
 
-static prefix_state analyze_prefixes(instruction_bytes const &instr)
+static prefix_state analyze_prefixes(prefix_group_lut const &group_lut_, instruction_bytes const &instr)
 {
   prefix_state state;
 
@@ -156,7 +156,7 @@ bool search_engine::find_next_candidate()
     goto again;
   }
 
-  auto const state = analyze_prefixes(current_);
+  auto const state = analyze_prefixes(group_lut_, current_);
 
   // Duplicated prefixes make the search space explode without generating
   // insight. Also enforce order on prefixes to further reduce search space.