Start adding a basic /proc filesystem and a "ps" utility.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/ed2422d7afb

AK/Function.h

@@ -51,7 +51,7 @@ public:
     {
     }
 
-    Out operator()(In... in)
+    Out operator()(In... in) const
     {
         ASSERT(m_callableWrapper);
         return m_callableWrapper->call(forward<In>(in)...);
@@ -83,7 +83,7 @@ private:
     class CallableWrapperBase {
     public:
         virtual ~CallableWrapperBase() { }
-        virtual Out call(In...) = 0;
+        virtual Out call(In...) const = 0;
     };
 
     template<typename CallableType>
@@ -97,7 +97,7 @@ private:
         CallableWrapper(const CallableWrapper&) = delete;
         CallableWrapper& operator=(const CallableWrapper&) = delete;
 
-        Out call(In... in) final { return m_callable(forward<In>(in)...); }
+        Out call(In... in) const final { return m_callable(forward<In>(in)...); }
 
     private:
         CallableType m_callable;

Kernel/Makefile

@@ -21,7 +21,8 @@ KERNEL_OBJS = \
        MemoryManager.o \
        Console.o \
        IRQHandler.o \
-       kprintf.o
+       kprintf.o \
+       ProcFileSystem.o
 
 VFS_OBJS = \
     ../VirtualFileSystem/DiskDevice.o \
@@ -35,7 +36,8 @@ VFS_OBJS = \
     ../VirtualFileSystem/Ext2FileSystem.o \
     ../VirtualFileSystem/InodeIdentifier.o \
     ../VirtualFileSystem/VirtualFileSystem.o \
-    ../VirtualFileSystem/FileHandle.o
+    ../VirtualFileSystem/FileHandle.o \
+    ../VirtualFileSystem/SyntheticFileSystem.o
 
 ELFLOADER_OBJS = \
     ../ELFLoader/ELFImage.o \

Kernel/ProcFileSystem.cpp

@@ -0,0 +1,29 @@
+#include "ProcFileSystem.h"
+#include <AK/StdLib.h>
+
+RetainPtr<ProcFileSystem> ProcFileSystem::create()
+{
+    return adopt(*new ProcFileSystem);
+}
+
+ProcFileSystem::ProcFileSystem()
+{
+}
+
+ProcFileSystem::~ProcFileSystem()
+{
+}
+
+bool ProcFileSystem::initialize()
+{
+    SyntheticFileSystem::initialize();
+    addFile(createGeneratedFile("summary", [] {
+        return String("Process summary!").toByteBuffer();
+    }));
+    return true;
+}
+
+const char* ProcFileSystem::className() const
+{
+    return "procfs";
+}

Kernel/ProcFileSystem.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <AK/Types.h>
+#include <VirtualFileSystem/SyntheticFileSystem.h>
+
+class ProcFileSystem final : public SyntheticFileSystem {
+public:
+    virtual ~ProcFileSystem() override;
+    static RetainPtr<ProcFileSystem> create();
+
+    virtual bool initialize() override;
+    virtual const char* className() const override;
+
+private:
+    ProcFileSystem();
+};
+

Kernel/Task.cpp

@@ -645,7 +645,9 @@ FileHandle* Task::openFile(String&& path)
 {
     auto handle = VirtualFileSystem::the().open(move(path));
     if (!handle) {
+#ifdef DEBUG_IO
         kprintf("vfs::open() failed\n");
+#endif
         return nullptr;
     }
     handle->setFD(m_fileHandles.size());

Kernel/init.cpp

@@ -25,6 +25,7 @@
 #include "MemoryManager.h"
 #include <ELFLoader/ELFLoader.h>
 #include "Console.h"
+#include "ProcFileSystem.h"
 
 #define TEST_VFS
 //#define TEST_ELF_LOADER
@@ -132,7 +133,9 @@ static void init_stage2()
 
     vfs->mountRoot(e2fs.copyRef());
 
-    //vfs->listDirectory("/");
+    auto procfs = ProcFileSystem::create();
+    procfs->initialize();
+    vfs->mount(procfs.copyRef(), "/proc");
 
     {
         auto motdFile = vfs->open("/motd.txt");

Kernel/sync-sh

@@ -1,5 +1,7 @@
 mkdir mnt
 mount -o loop _fs_contents mnt/
 cp ../Userland/sh mnt/bin/sh
+cp ../Userland/id mnt/bin/id
+cp ../Userland/ps mnt/bin/ps
 umount mnt
 sync

Userland/.gitignore

@@ -1,3 +1,4 @@
 id
 sh
+ps
 *.o

Userland/Makefile

@@ -1,10 +1,12 @@
 OBJS = \
        id.o \
-       sh.o
+       sh.o \
+       ps.o
 
 APPS = \
        id \
-       sh
+       sh \
+       ps
 
 ARCH_FLAGS =
 STANDARD_FLAGS = -std=c++17 -nostdinc++ -nostdlib
@@ -30,6 +32,9 @@ id: id.o
 sh: sh.o
 	$(LD) -o $@ $(LDFLAGS) $< ../LibC/LibC.a
 
+ps: ps.o
+	$(LD) -o $@ $(LDFLAGS) $< ../LibC/LibC.a
+
 .cpp.o:
 	@echo "CXX $<"; $(CXX) $(CXXFLAGS) -o $@ -c $<
 

Userland/ps.cpp

@@ -0,0 +1,25 @@
+#include <LibC/stdio.h>
+#include <LibC/unistd.h>
+
+int main(int c, char** v)
+{
+    int fd = open("/proc/summary");
+    if (fd == -1) {
+        printf("failed to open /proc/summary :(\n");
+        return 1;
+    }
+    for (;;) {
+        char buf[16];
+        ssize_t nread = read(fd, buf, sizeof(buf));
+        if (nread == 0)
+            break;
+        if (nread < 0) {
+            printf("failed to read :(\n");
+            return 2;
+        }
+        for (ssize_t i = 0; i < nread; ++i) {
+            putchar(buf[i]);
+        }
+    }
+    return 0;
+}

VirtualFileSystem/SyntheticFileSystem.cpp

@@ -1,6 +1,8 @@
 #include "SyntheticFileSystem.h"
 #include <AK/StdLib.h>
 
+//#define SYNTHFS_DEBUG
+
 RetainPtr<SyntheticFileSystem> SyntheticFileSystem::create()
 {
     return adopt(*new SyntheticFileSystem);
@@ -25,10 +27,12 @@ bool SyntheticFileSystem::initialize()
     rootDir->metadata.gid = 0;
     rootDir->metadata.size = 0;
     rootDir->metadata.mtime = mepoch;
-    m_files.append(std::move(rootDir));
+    m_files.append(move(rootDir));
 
+#ifndef SERENITY
     addFile(createTextFile("file", "I'm a synthetic file!\n"));
     addFile(createTextFile("message", "Hey! This isn't my bottle!\n"));
+#endif
     return true;
 }
 
@@ -36,7 +40,7 @@ auto SyntheticFileSystem::createTextFile(String&& name, String&& text) -> OwnPtr
 {
     auto file = make<File>();
     file->data = text.toByteBuffer();
-    file->name = std::move(name);
+    file->name = move(name);
     file->metadata.size = file->data.size();
     file->metadata.uid = 100;
     file->metadata.gid = 200;
@@ -45,11 +49,24 @@ auto SyntheticFileSystem::createTextFile(String&& name, String&& text) -> OwnPtr
     return file;
 }
 
+auto SyntheticFileSystem::createGeneratedFile(String&& name, Function<ByteBuffer()>&& generator) -> OwnPtr<File>
+{
+    auto file = make<File>();
+    file->generator = move(generator);
+    file->name = move(name);
+    file->metadata.size = 0;
+    file->metadata.uid = 0;
+    file->metadata.gid = 0;
+    file->metadata.mode = 0100644;
+    file->metadata.mtime = mepoch;
+    return file;
+}
+
 void SyntheticFileSystem::addFile(OwnPtr<File>&& file)
 {
     ASSERT(file);
     file->metadata.inode = { id(), m_files.size() + 1 };
-    m_files.append(std::move(file));
+    m_files.append(move(file));
 }
 
 const char* SyntheticFileSystem::className() const
@@ -66,7 +83,7 @@ bool SyntheticFileSystem::enumerateDirectoryInode(InodeIdentifier inode, Functio
 {
     ASSERT(inode.fileSystemID() == id());
 #ifdef SYNTHFS_DEBUG
-    printf("[synthfs] enumerateDirectoryInode %u\n", inode.index());
+    kprintf("[synthfs] enumerateDirectoryInode %u\n", inode.index());
 #endif
     if (inode.index() != 1)
         return false;
@@ -83,17 +100,21 @@ InodeMetadata SyntheticFileSystem::inodeMetadata(InodeIdentifier inode) const
 {
     ASSERT(inode.fileSystemID() == id());
 #ifdef SYNTHFS_DEBUG
-    printf("[synthfs] inodeMetadata(%u)\n", inode.index);
+    kprintf("[synthfs] inodeMetadata(%u)\n", inode.index());
 #endif
     if (inode.index() == 0 || inode.index() > m_files.size())
         return InodeMetadata();
-    return m_files[inode.index() - 1]->metadata;
+    auto& file = *m_files[inode.index() - 1];
+    auto metadata = file.metadata;
+    if (file.generator)
+        metadata.size = file.generator().size();
+    return metadata;
 }
 
 bool SyntheticFileSystem::setModificationTime(InodeIdentifier, dword timestamp)
 {
     (void) timestamp;
-    printf("FIXME: Implement SyntheticFileSystem::setModificationTime().\n");
+    kprintf("FIXME: Implement SyntheticFileSystem::setModificationTime().\n");
     return false;
 }
 
@@ -102,13 +123,13 @@ InodeIdentifier SyntheticFileSystem::createInode(InodeIdentifier parentInode, co
     (void) parentInode;
     (void) name;
     (void) mode;
-    printf("FIXME: Implement SyntheticFileSystem::createDirectoryInode().\n");
+    kprintf("FIXME: Implement SyntheticFileSystem::createDirectoryInode().\n");
     return { };
 }
 
 bool SyntheticFileSystem::writeInode(InodeIdentifier, const ByteBuffer&)
 {
-    printf("FIXME: Implement SyntheticFileSystem::writeInode().\n");
+    kprintf("FIXME: Implement SyntheticFileSystem::writeInode().\n");
     return false;
 }
 
@@ -116,7 +137,7 @@ Unix::ssize_t SyntheticFileSystem::readInodeBytes(InodeIdentifier inode, Unix::o
 {
     ASSERT(inode.fileSystemID() == id());
 #ifdef SYNTHFS_DEBUG
-    printf("[synthfs] readInode %u\n", inode.index());
+    kprintf("[synthfs] readInode %u\n", inode.index());
 #endif
     ASSERT(inode.index() != 1);
     ASSERT(inode.index() <= m_files.size());
@@ -124,13 +145,18 @@ Unix::ssize_t SyntheticFileSystem::readInodeBytes(InodeIdentifier inode, Unix::o
     ASSERT(buffer);
 
     auto& file = *m_files[inode.index() - 1];
-    Unix::ssize_t nread = min(static_cast<Unix::off_t>(file.data.size() - offset), static_cast<Unix::off_t>(count));
-    memcpy(buffer, file.data.pointer() + offset, nread);
+    ByteBuffer generatedData;
+    if (file.generator)
+        generatedData = file.generator();
+    auto* data = generatedData ? &generatedData : &file.data;
+
+    Unix::ssize_t nread = min(static_cast<Unix::off_t>(data->size() - offset), static_cast<Unix::off_t>(count));
+    memcpy(buffer, data->pointer() + offset, nread);
     return nread;
 }
 
 InodeIdentifier SyntheticFileSystem::makeDirectory(InodeIdentifier parentInode, const String& name, Unix::mode_t)
 {
-    printf("FIXME: Implement SyntheticFileSystem::makeDirectory().\n");
+    kprintf("FIXME: Implement SyntheticFileSystem::makeDirectory().\n");
     return { };
 }

VirtualFileSystem/SyntheticFileSystem.h

@@ -4,7 +4,7 @@
 #include "UnixTypes.h"
 #include <AK/HashMap.h>
 
-class SyntheticFileSystem final : public FileSystem {
+class SyntheticFileSystem : public FileSystem {
 public:
     virtual ~SyntheticFileSystem() override;
     static RetainPtr<SyntheticFileSystem> create();
@@ -20,18 +20,22 @@ public:
     virtual Unix::ssize_t readInodeBytes(InodeIdentifier, Unix::off_t offset, Unix::size_t count, byte* buffer) const override;
     virtual InodeIdentifier makeDirectory(InodeIdentifier parentInode, const String& name, Unix::mode_t) override;
 
-private:
+protected:
     SyntheticFileSystem();
 
     struct File {
         String name;
         InodeMetadata metadata;
         ByteBuffer data;
+        Function<ByteBuffer()> generator;
     };
 
     OwnPtr<File> createTextFile(String&& name, String&& text);
+    OwnPtr<File> createGeneratedFile(String&& name, Function<ByteBuffer()>&&);
+
     void addFile(OwnPtr<File>&&);
 
+private:
     Vector<OwnPtr<File>> m_files;
 };