Kernel: Move syscall implementations out of Process.cpp

This is something I've been meaning to do for a long time, and here we
finally go. This patch moves all sys$foo functions out of Process.cpp
and into files in Kernel/Syscalls/.

It's not exactly one syscall per file (although it could be, but I got
a bit tired of the repetitive work here..)

This makes hacking on individual syscalls a lot less painful since you
don't have to rebuild nearly as much code every time. I'm also hopeful
that this makes it easier to understand individual syscalls. :^)

1 files changed, 188 insertions, 0 deletions

diff --git a/Kernel/Syscalls/module.cpp b/Kernel/Syscalls/module.cpp
new file mode 100644
index 0000000000..85d0ef49b8
--- /dev/null
+++ b/Kernel/Syscalls/module.cpp
@@ -0,0 +1,188 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <Kernel/FileSystem/FileDescription.h>
+#include <Kernel/FileSystem/VirtualFileSystem.h>
+#include <Kernel/KSyms.h>
+#include <Kernel/Module.h>
+#include <Kernel/Process.h>
+#include <LibELF/Loader.h>
+
+namespace Kernel {
+
+extern HashMap<String, OwnPtr<Module>>* g_modules;
+
+int Process::sys$module_load(const char* user_path, size_t path_length)
+{
+    if (!is_superuser())
+        return -EPERM;
+
+    REQUIRE_NO_PROMISES;
+
+    auto path = get_syscall_path_argument(user_path, path_length);
+    if (path.is_error())
+        return path.error();
+    auto description_or_error = VFS::the().open(path.value(), O_RDONLY, 0, current_directory());
+    if (description_or_error.is_error())
+        return description_or_error.error();
+    auto& description = description_or_error.value();
+    auto payload_or_error = description->read_entire_file();
+    if (payload_or_error.is_error())
+        return payload_or_error.error();
+
+    auto payload = payload_or_error.value();
+    auto storage = KBuffer::create_with_size(payload.size());
+    memcpy(storage.data(), payload.data(), payload.size());
+    payload.clear();
+
+    auto elf_image = make<ELF::Image>(storage.data(), storage.size());
+    if (!elf_image->parse())
+        return -ENOEXEC;
+
+    HashMap<String, u8*> section_storage_by_name;
+
+    auto module = make<Module>();
+
+    elf_image->for_each_section_of_type(SHT_PROGBITS, [&](const ELF::Image::Section& section) {
+        if (!section.size())
+            return IterationDecision::Continue;
+        auto section_storage = KBuffer::copy(section.raw_data(), section.size(), Region::Access::Read | Region::Access::Write | Region::Access::Execute);
+        section_storage_by_name.set(section.name(), section_storage.data());
+        module->sections.append(move(section_storage));
+        return IterationDecision::Continue;
+    });
+
+    bool missing_symbols = false;
+
+    elf_image->for_each_section_of_type(SHT_PROGBITS, [&](const ELF::Image::Section& section) {
+        if (!section.size())
+            return IterationDecision::Continue;
+        auto* section_storage = section_storage_by_name.get(section.name()).value_or(nullptr);
+        ASSERT(section_storage);
+        section.relocations().for_each_relocation([&](const ELF::Image::Relocation& relocation) {
+            auto& patch_ptr = *reinterpret_cast<ptrdiff_t*>(section_storage + relocation.offset());
+            switch (relocation.type()) {
+            case R_386_PC32: {
+                // PC-relative relocation
+                dbg() << "PC-relative relocation: " << relocation.symbol().name();
+                u32 symbol_address = address_for_kernel_symbol(relocation.symbol().name());
+                if (symbol_address == 0)
+                    missing_symbols = true;
+                dbg() << "   Symbol address: " << (void*)symbol_address;
+                ptrdiff_t relative_offset = (char*)symbol_address - ((char*)&patch_ptr + 4);
+                patch_ptr = relative_offset;
+                break;
+            }
+            case R_386_32: // Absolute relocation
+                dbg() << "Absolute relocation: '" << relocation.symbol().name() << "' value:" << relocation.symbol().value() << ", index:" << relocation.symbol_index();
+
+                if (relocation.symbol().bind() == STB_LOCAL) {
+                    auto* section_storage_containing_symbol = section_storage_by_name.get(relocation.symbol().section().name()).value_or(nullptr);
+                    ASSERT(section_storage_containing_symbol);
+                    u32 symbol_address = (ptrdiff_t)(section_storage_containing_symbol + relocation.symbol().value());
+                    if (symbol_address == 0)
+                        missing_symbols = true;
+                    dbg() << "   Symbol address: " << (void*)symbol_address;
+                    patch_ptr += symbol_address;
+                } else if (relocation.symbol().bind() == STB_GLOBAL) {
+                    u32 symbol_address = address_for_kernel_symbol(relocation.symbol().name());
+                    if (symbol_address == 0)
+                        missing_symbols = true;
+                    dbg() << "   Symbol address: " << (void*)symbol_address;
+                    patch_ptr += symbol_address;
+                } else {
+                    ASSERT_NOT_REACHED();
+                }
+                break;
+            }
+            return IterationDecision::Continue;
+        });
+
+        return IterationDecision::Continue;
+    });
+
+    if (missing_symbols)
+        return -EINVAL;
+
+    auto* text_base = section_storage_by_name.get(".text").value_or(nullptr);
+    if (!text_base) {
+        dbg() << "No .text section found in module!";
+        return -EINVAL;
+    }
+
+    elf_image->for_each_symbol([&](const ELF::Image::Symbol& symbol) {
+        dbg() << " - " << symbol.type() << " '" << symbol.name() << "' @ " << (void*)symbol.value() << ", size=" << symbol.size();
+        if (symbol.name() == "module_init") {
+            module->module_init = (ModuleInitPtr)(text_base + symbol.value());
+        } else if (symbol.name() == "module_fini") {
+            module->module_fini = (ModuleFiniPtr)(text_base + symbol.value());
+        } else if (symbol.name() == "module_name") {
+            const u8* storage = section_storage_by_name.get(symbol.section().name()).value_or(nullptr);
+            if (storage)
+                module->name = String((const char*)(storage + symbol.value()));
+        }
+        return IterationDecision::Continue;
+    });
+
+    if (!module->module_init)
+        return -EINVAL;
+
+    if (g_modules->contains(module->name)) {
+        dbg() << "a module with the name " << module->name << " is already loaded; please unload it first";
+        return -EEXIST;
+    }
+
+    module->module_init();
+
+    auto name = module->name;
+    g_modules->set(name, move(module));
+
+    return 0;
+}
+
+int Process::sys$module_unload(const char* user_name, size_t name_length)
+{
+    if (!is_superuser())
+        return -EPERM;
+
+    REQUIRE_NO_PROMISES;
+
+    auto module_name = validate_and_copy_string_from_user(user_name, name_length);
+    if (module_name.is_null())
+        return -EFAULT;
+
+    auto it = g_modules->find(module_name);
+    if (it == g_modules->end())
+        return -ENOENT;
+
+    if (it->value->module_fini)
+        it->value->module_fini();
+
+    g_modules->remove(it);
+    return 0;
+}
+
+}