From 76ddf6b8dad8b98f46a8f47ddfa1e3f536069961 Mon Sep 17 00:00:00 2001
From: Kornel Pal <kornelpal@gmail.com>
Date: Wed, 22 Dec 2021 02:58:09 +0100
Subject: [PATCH] PE: Add position independent decompressor stub for i386

---
 src/p_w32pe.cpp              | 14 +++++++++-----
 src/p_w64pep.cpp             |  4 +++-
 src/pefile.cpp               |  1 +
 src/pefile.h                 |  1 +
 src/stub/src/i386-win32.pe.S |  7 +++++++
 5 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/src/p_w32pe.cpp b/src/p_w32pe.cpp
index c9584836..6a346935 100644
--- a/src/p_w32pe.cpp
+++ b/src/p_w32pe.cpp
@@ -110,14 +110,17 @@ void PackW32Pe::buildLoader(const Filter *ft)
 
     // prepare loader
     initLoader(stub_i386_win32_pe, sizeof(stub_i386_win32_pe), 2);
-    addLoader(isdll ? "PEISDLL1" : "",
-              "PEMAIN01",
+    if (isdll)
+        addLoader("PEISDLL1");
+    addLoader("PEMAIN01",
+              use_stub_relocs ? "PESOCREL" : "PESOCPIC",
+              "PESOUNC0",
               icondir_count > 1 ? (icondir_count == 2 ? "PEICONS1" : "PEICONS2") : "",
               tmp_tlsindex ? "PETLSHAK" : "",
               "PEMAIN02",
               ph.first_offset_found == 1 ? "PEMAIN03" : "",
               getDecompressorSections(),
-              /*multipass ? "PEMULTIP" :  */  "",
+              //multipass ? "PEMULTIP" : "",
               "PEMAIN10",
               nullptr
              );
@@ -255,7 +258,7 @@ void PackW32Pe::defineSymbols(unsigned ncsection, unsigned upxsection,
 
     const unsigned esi0 = s1addr + ic;
     linker->defineSymbol("start_of_uncompressed", 0u - esi0 + rvamin);
-    linker->defineSymbol("start_of_compressed", esi0 + ih.imagebase);
+    linker->defineSymbol("start_of_compressed", use_stub_relocs ? esi0 + ih.imagebase : esi0);
 
     if (use_tls_callbacks)
     {
@@ -270,7 +273,8 @@ void PackW32Pe::defineSymbols(unsigned ncsection, unsigned upxsection,
 
 void PackW32Pe::addNewRelocations(Reloc &rel, unsigned base)
 {
-    rel.add(base + linker->getSymbolOffset("PEMAIN01") + 2, 3);
+    if (use_stub_relocs)
+        rel.add(base + linker->getSymbolOffset("PESOCREL") + 1, 3);
 }
 
 void PackW32Pe::setOhDataBase(const pe_section_t *osection)
diff --git a/src/p_w64pep.cpp b/src/p_w64pep.cpp
index 5ef28833..bb509a9e 100644
--- a/src/p_w64pep.cpp
+++ b/src/p_w64pep.cpp
@@ -47,7 +47,9 @@ static const
 **************************************************************************/
 
 PackW64Pep::PackW64Pep(InputFile *f) : super(f)
-{}
+{
+    use_stub_relocs = false;
+}
 
 
 PackW64Pep::~PackW64Pep()
diff --git a/src/pefile.cpp b/src/pefile.cpp
index f319a936..86ebdd62 100644
--- a/src/pefile.cpp
+++ b/src/pefile.cpp
@@ -117,6 +117,7 @@ PeFile::PeFile(InputFile *f) : super(f)
 
     use_dep_hack = true;
     use_clear_dirty_stack = true;
+    use_stub_relocs = true;
     isrtm = false;
 }
 
diff --git a/src/pefile.h b/src/pefile.h
index ce97741b..501c1da2 100644
--- a/src/pefile.h
+++ b/src/pefile.h
@@ -214,6 +214,7 @@ protected:
     bool isrtm;
     bool use_dep_hack;
     bool use_clear_dirty_stack;
+    bool use_stub_relocs;
 
 
     static unsigned virta2objnum (unsigned, pe_section_t *, unsigned);
diff --git a/src/stub/src/i386-win32.pe.S b/src/stub/src/i386-win32.pe.S
index 98b1d123..c8995953 100644
--- a/src/stub/src/i386-win32.pe.S
+++ b/src/stub/src/i386-win32.pe.S
@@ -40,7 +40,14 @@ section         PEISDLL1
                 jnz     reloc_end_jmp
 section         PEMAIN01
                 pusha
+section         PESOCREL
                 mov     esi, offset start_of_compressed       // relocated
+section         PESOCPIC
+                call    get_eip
+get_eip:
+                pop     eax
+                lea     esi, [eax + start_of_compressed - get_eip]
+section         PESOUNC0
                 lea     edi, [esi + start_of_uncompressed]
 section         PEICONS1
                 incw    [edi + icon_offset]