From 97e0d75bcbdde4ba166de8cd9e36b87b4823f30a Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Thu, 18 Oct 2018 15:38:04 +0200
Subject: [PATCH] ELFLoader works inside the kernel!

We load /_hello.o which just prints out a simple message.
It executes inside the kernel itself, so no fancy userspace process
or anything, but this is still so cool!
---
 ELFLoader/ELFImage.cpp  |   8 ++++----
 ELFLoader/ELFImage.h    |   4 ++--
 ELFLoader/ELFLoader.cpp |   8 ++++++--
 ELFLoader/ELFLoader.h   |   4 ++++
 ELFLoader/ExecSpace.cpp |  28 ++++++++++++++++++++++------
 ELFLoader/ExecSpace.h   |   4 ++++
 Kernel/_fs_contents     | Bin 1024000 -> 1024000 bytes
 Kernel/_hello.cpp       |   7 +++++++
 Kernel/_test.cpp        |   2 +-
 Kernel/init.cpp         |  22 ++++++++++++++++++++++
 10 files changed, 72 insertions(+), 15 deletions(-)
 create mode 100644 Kernel/_hello.cpp

diff --git a/ELFLoader/ELFImage.cpp b/ELFLoader/ELFImage.cpp
index 58a0798071..092ff94e1c 100644
--- a/ELFLoader/ELFImage.cpp
+++ b/ELFLoader/ELFImage.cpp
@@ -2,8 +2,8 @@
 #include <AK/kstdio.h>
 
 #ifdef SERENITY_KERNEL
-ELFImage::ELFImage(const byte* data)
-    : m_data(data)
+ELFImage::ELFImage(ByteBuffer&& buffer)
+    : m_buffer(buffer)
 {
     m_isValid = parse();
 }
@@ -137,7 +137,7 @@ const char* ELFImage::tableString(unsigned offset) const
 const char* ELFImage::rawData(unsigned offset) const
 {
 #ifdef SERENITY_KERNEL
-    return reinterpret_cast<const char*>(m_data) + offset;
+    return reinterpret_cast<const char*>(m_buffer.pointer()) + offset;
 #else
     return reinterpret_cast<const char*>(m_file.pointer()) + offset;
 #endif
@@ -178,7 +178,7 @@ const ELFImage::RelocationSection ELFImage::Section::relocations() const
 {
     // FIXME: This is ugly.
     char relocationSectionName[128];
-    ksprintf(relocationSectionName, ".rel%s", name());
+    int x = ksprintf(relocationSectionName, ".rel%s", name());
 
     kprintf("looking for '%s'\n", relocationSectionName);
     auto relocationSection = m_image.lookupSection(relocationSectionName);
diff --git a/ELFLoader/ELFImage.h b/ELFLoader/ELFImage.h
index dc83410c92..78f1c28621 100644
--- a/ELFLoader/ELFImage.h
+++ b/ELFLoader/ELFImage.h
@@ -12,7 +12,7 @@
 class ELFImage {
 public:
 #ifdef SERENITY_KERNEL
-    explicit ELFImage(const byte* data);
+    explicit ELFImage(ByteBuffer&&);
 #else
     explicit ELFImage(MappedFile&&);
 #endif
@@ -132,7 +132,7 @@ private:
     const char* sectionIndexToString(unsigned index);
 
 #ifdef SERENITY_KERNEL
-    const byte* m_data;
+    ByteBuffer m_buffer;
 #else
     MappedFile m_file;
 #endif
diff --git a/ELFLoader/ELFLoader.cpp b/ELFLoader/ELFLoader.cpp
index 60e91937c5..6b5b0c928b 100644
--- a/ELFLoader/ELFLoader.cpp
+++ b/ELFLoader/ELFLoader.cpp
@@ -1,7 +1,11 @@
 #include "ELFLoader.h"
 #include <AK/kstdio.h>
 
+#ifdef SERENITY_KERNEL
+ELFLoader::ELFLoader(ExecSpace& execSpace, ByteBuffer&& file)
+#else
 ELFLoader::ELFLoader(ExecSpace& execSpace, MappedFile&& file)
+#endif
     : m_execSpace(execSpace)
 {
     m_image = make<ELFImage>(move(file));
@@ -104,9 +108,9 @@ void ELFLoader::performRelocations()
 void ELFLoader::exportSymbols()
 {
     m_image->forEachSymbol([&] (const ELFImage::Symbol symbol) {
-        kprintf("symbol: %u, type=%u, name=%s\n", symbol.index(), symbol.type(), symbol.name());
+        kprintf("symbol: %u, type=%u, name=%s, section=%u\n", symbol.index(), symbol.type(), symbol.name(), symbol.sectionIndex());
         if (symbol.type() == STT_FUNC)
-            m_execSpace.addSymbol(symbol.name(), areaForSectionName(".text") + symbol.value(), symbol.size());
+            m_execSpace.addSymbol(symbol.name(), areaForSection(symbol.section()) + symbol.value(), symbol.size());
         // FIXME: What about other symbol types?
     });
 }
diff --git a/ELFLoader/ELFLoader.h b/ELFLoader/ELFLoader.h
index f62745484a..e7249ee8c7 100644
--- a/ELFLoader/ELFLoader.h
+++ b/ELFLoader/ELFLoader.h
@@ -9,7 +9,11 @@
 
 class ELFLoader {
 public:
+#ifdef SERENITY_KERNEL
+    ELFLoader(ExecSpace&, ByteBuffer&&);
+#else
     ELFLoader(ExecSpace&, MappedFile&&);
+#endif
     ~ELFLoader();
 
     bool load();
diff --git a/ELFLoader/ExecSpace.cpp b/ELFLoader/ExecSpace.cpp
index ca625b4311..8fe97a76ce 100644
--- a/ELFLoader/ExecSpace.cpp
+++ b/ELFLoader/ExecSpace.cpp
@@ -12,19 +12,31 @@ ExecSpace::~ExecSpace()
 {
 }
 
+#ifdef SERENITY_KERNEL
+int puts(const char* str)
+{
+    kprintf("%s\n", str);
+    return 0;
+}
+#endif
+
 void ExecSpace::initializeBuiltins()
 {
     m_symbols.set("puts", { (char*)puts, 0 });
 }
 
+#ifdef SERENITY_KERNEL
+bool ExecSpace::loadELF(ByteBuffer&& file)
+#else
 bool ExecSpace::loadELF(MappedFile&& file)
+#endif
 {
     ELFLoader loader(*this, move(file));
     if (!loader.load())
         return false;
-    printf("[ExecSpace] ELF loaded, symbol map now:\n");
+    kprintf("[ExecSpace] ELF loaded, symbol map now:\n");
     for (auto& s : m_symbols) {
-        printf("> %p: %s (%u)\n",
+        kprintf("> %p: %s (%u)\n",
                 s.value.ptr,
                 s.key.characters(),
                 s.value.size);
@@ -34,11 +46,15 @@ bool ExecSpace::loadELF(MappedFile&& file)
 
 static void disassemble(const char* data, size_t length)
 {
-#ifdef SERENITY_KERNEL
-#else
     if (!length)
         return;
 
+#ifdef SERENITY_KERNEL
+    for (unsigned i = 0; i < length; ++i) {
+        kprintf("%b ", (unsigned char)data[i]);
+    }
+    kprintf("\n");
+#else
     TemporaryFile temp;
     if (!temp.isValid()) {
         fprintf(stderr, "Unable to create temp file for disassembly.\n");
@@ -52,7 +68,7 @@ static void disassemble(const char* data, size_t length)
     temp.sync();
 
     char cmdbuf[128];
-    sprintf(cmdbuf, "nasm -f bin -o /dev/stdout %s | ndisasm -b32 -", temp.fileName().characters());
+    ksprintf(cmdbuf, "nasm -f bin -o /dev/stdout %s | ndisasm -b32 -", temp.fileName().characters());
     system(cmdbuf);
 #endif
 }
@@ -60,7 +76,7 @@ static void disassemble(const char* data, size_t length)
 char* ExecSpace::symbolPtr(const char* name)
 {
     if (auto it = m_symbols.find(name); it != m_symbols.end()) {
-        printf("[ELFLoader] symbolPtr(%s) dump:\n", name);
+        kprintf("[ELFLoader] symbolPtr(%s) dump:\n", name);
         auto& symbol = (*it).value;
         disassemble(symbol.ptr, symbol.size);
         return symbol.ptr;
diff --git a/ELFLoader/ExecSpace.h b/ELFLoader/ExecSpace.h
index 1086ac17f2..2b175d473a 100644
--- a/ELFLoader/ExecSpace.h
+++ b/ELFLoader/ExecSpace.h
@@ -37,7 +37,11 @@ public:
     ExecSpace();
     ~ExecSpace();
 
+#ifdef SERENITY_KERNEL
+    bool loadELF(ByteBuffer&&);
+#else
     bool loadELF(MappedFile&&);
+#endif
 
     char* symbolPtr(const char* name);
 
diff --git a/Kernel/_fs_contents b/Kernel/_fs_contents
index 53da2581e1b1535107805fd3abd73f613fced14e..e477e526b93abf23e44644000936533dc3e3e541 100644
GIT binary patch
delta 876
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zeva?_jO-H`Et&o^Ph_;(TqDuJ%)`up0GkD6-ZM}BFW;#MGDfZaL^KFP<k=XQAPfdJ
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z%p^4ywFG7c29WVE3{uR%zzDYnq>-IzBBK?HeqCMV=0XDr{YeQAWCR%48RJV*i%azK
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z-|*}JX?pSJ|NsAn2bz!Y9G=K1JUM}tXY!8=DPBAvIR*v>VFm^UAqG|kF(@BI34jQw
z3zG{97*cc6;#2cViYgfjN=u3v7+4q>7#LX@7&sXi7??OGcU{)kF3L|yEJ@UZtJEtl
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z3=9klpr&w4{&-!QRe+I!L3*;_4P{mvMh1q=$qz4xPY$>-XVL`)rXMVul`c3jbHaVN
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FWB`Ja)E@u<

delta 356
zcmZoTVApWKZUYYs>uP2OhWN>XEYh4JStp|Fvrj~`Z8l|bW@L=s$k@&_iGzoEHFNxC
zeva?_jP?^5EkT6!<{F6(W*$Zc1lTMn^PYL~fB8<un(PzNl~4?kXJcT3Fc?@F7#Jir
zGKMp4QfA@R_2FP(fT;x05Jij(Y!C(m$b1t91_o0G1_rZ<jK-5w3}hA=>Q5ACn3V8<
zTZNgOF}@_VxI{01BcmvDQ%YM3V_OPSTMBbq3QJoGYg-E2vK00miwyM#2<ZR-3*KUP

diff --git a/Kernel/_hello.cpp b/Kernel/_hello.cpp
new file mode 100644
index 0000000000..36be71125f
--- /dev/null
+++ b/Kernel/_hello.cpp
@@ -0,0 +1,7 @@
+extern "C" int puts(const char*);
+
+extern "C" int elf_entry()
+{
+    puts("Home, where you are supposed to be...");
+    return 0;
+}
diff --git a/Kernel/_test.cpp b/Kernel/_test.cpp
index 125020cb8c..467b29db62 100644
--- a/Kernel/_test.cpp
+++ b/Kernel/_test.cpp
@@ -2,7 +2,7 @@
 
 using namespace Userspace;
 
-int elf_entry()
+extern "C" int elf_entry()
 {
     int fd = open("/Banner.txt");
     char buf[2048];
diff --git a/Kernel/init.cpp b/Kernel/init.cpp
index 70e4ad2426..85f6dbb537 100644
--- a/Kernel/init.cpp
+++ b/Kernel/init.cpp
@@ -23,6 +23,7 @@
 #include <VirtualFileSystem/FileHandle.h>
 #include <AK/OwnPtr.h>
 #include "MemoryManager.h"
+#include <ELFLoader/ELFLoader.h>
 
 #if 0
 /* Keyboard LED disco task ;^) */
@@ -82,6 +83,8 @@ static void user_kprintf_main()
     DO_SYSCALL_A1(0x4000, 0);
     kprintf("This should not work!\n");
     HANG;
+    for (;;) {
+    }
 }
 
 system_t system;
@@ -179,6 +182,25 @@ void init()
     }
 #endif
 
+    {
+        auto testExecutable = vfs->open("/_hello.o");
+        ASSERT(testExecutable);
+        auto testExecutableData = testExecutable->readEntireFile();
+        ASSERT(testExecutableData);
+        
+        ExecSpace space;
+        space.loadELF(move(testExecutableData));
+        auto* elf_entry = space.symbolPtr("elf_entry");
+        ASSERT(elf_entry);
+
+        typedef int (*MainFunctionPtr)(void);
+        kprintf("elf_entry: %p\n", elf_entry);
+        int rc = reinterpret_cast<MainFunctionPtr>(elf_entry)();
+        kprintf("it returned %d\n", rc);
+
+        HANG;
+    }
+
     // The idle task will spend its eternity here for now.
     for (;;) {
         asm("hlt");