kernel+libc+apps: Add support for environment variables

apps/CMakeLists.txt

@@ -8,6 +8,7 @@ endfunction()
 
 luna_app(init.cpp init)
 luna_app(sh.cpp sh)
+luna_app(env.cpp env)
 
 luna_app(cat.cpp cat)
 target_link_libraries(cat PRIVATE os)

apps/env.cpp

@@ -0,0 +1,9 @@
+#include <stdio.h>
+
+extern char** environ;
+
+int main()
+{
+    char** env = environ;
+    while (*env) { puts(*(env++)); }
+}

apps/init.cpp

@@ -43,7 +43,8 @@ int main()
     if (ret == 0)
     {
         char* argv[] = { "/bin/sh", NULL };
-        execv(argv[0], argv);
+        char* envp[] = { "PATH=/bin:/sbin", NULL };
+        execve(argv[0], argv, envp);
         perror("execv");
         return 1;
     }

kernel/src/sys/exec.cpp

@@ -31,12 +31,13 @@ static Result<Vector<String>> copy_string_vector_from_userspace(u64 address)
     return result;
 }
 
-Result<u64> sys_exec(Registers* regs, SyscallArgs args)
+Result<u64> sys_execve(Registers* regs, SyscallArgs args)
 {
     auto path = TRY(MemoryManager::strdup_from_user(args[0]));
     auto argv = TRY(copy_string_vector_from_userspace(args[1]));
+    auto envp = TRY(copy_string_vector_from_userspace(args[2]));
 
-    // FIXME: Make sure argv is not too big.
+    // FIXME: Make sure argv & envp are not too big.
 
     auto inode = TRY(VFS::resolve_path(path.chars()));
 
@@ -56,6 +57,11 @@ Result<u64> sys_exec(Registers* regs, SyscallArgs args)
     u64 user_argv = TRY(image->push_string_vector_on_stack(argv));
     usize user_argc = argv.size();
 
+    kdbgln("exec: copying envp to image memory (envc = %zu)", envp.size());
+
+    u64 user_envp = TRY(image->push_string_vector_on_stack(envp));
+    usize user_envc = envp.size();
+
     // From now on, nothing should fail.
 
     kinfoln("exec: image load ok, will now replace existing process image");
@@ -77,7 +83,7 @@ Result<u64> sys_exec(Registers* regs, SyscallArgs args)
 
     MMU::switch_page_directory(current->directory);
 
-    current->set_arguments(user_argc, user_argv, 0, 0);
+    current->set_arguments(user_argc, user_argv, user_envc, user_envp);
 
     memcpy(regs, &current->regs, sizeof(*regs));
 

kernel/src/thread/Scheduler.cpp

@@ -115,13 +115,22 @@ namespace Scheduler
         thread->name = name;
         thread->parent_id = 0;
 
+        Vector<String> args;
+        auto name_string = TRY(String::from_cstring(name));
+        TRY(args.try_append(move(name_string)));
+
+        Vector<String> env;
+
         auto guard = make_scope_guard([&] { delete thread; });
 
         auto image = TRY(ThreadImage::try_load_from_elf(inode));
+        u64 argv = TRY(image->push_string_vector_on_stack(args));
+        u64 envp = TRY(image->push_string_vector_on_stack(env));
 
         guard.deactivate();
 
         image->apply(thread);
+        thread->set_arguments(args.size(), argv, env.size(), envp);
 
         kinfoln("Created userspace thread: id %lu with ip %#.16lx and sp %#.16lx (ksp %#lx)", thread->id, thread->ip(),
                 thread->sp(), thread->kernel_stack.top());

libc/CMakeLists.txt

@@ -15,6 +15,7 @@ set(SOURCES
     src/init.cpp
     src/dirent.cpp
     src/setjmp.cpp
+    src/env.cpp
     src/sys/stat.cpp
     src/sys/mman.cpp
     src/sys/wait.cpp

libc/include/stdlib.h

@@ -102,7 +102,8 @@ extern "C"
 
     int system(const char*);
 
-    char* getenv(const char*);
+    /* Get the value of an environment variable. */
+    char* getenv(const char* key);
 
     void qsort(void*, size_t, size_t, int (*)(const void*, const void*));
     void* bsearch(const void*, const void*, size_t, size_t, int (*)(const void*, const void*));

libc/include/unistd.h

@@ -34,7 +34,9 @@ extern "C"
     /* Replace the current process with another one. On success, does not return. */
     int execl(const char* path, const char* arg, ...);
 
-    int execve(const char*, char* const*, char* const*);
+    /* Replace the current process with another one. On success, does not return. */
+    int execve(const char* path, char* const* argv, char* const* envp);
+
     int execvp(const char*, char* const*);
 
     /* Call the operating system kernel for a specific service. */

libc/src/arch/x86_64/crt0.S

@@ -12,12 +12,14 @@ _start:
 
 	pushq %rsi
 	pushq %rdi
+	pushq %rcx
 
 	call libc_init
 
 	# Run the global constructors.
 	call _init
 
+	popq %rdx
 	popq %rdi
 	popq %rsi
 

libc/src/env.cpp

@@ -0,0 +1,31 @@
+#include <string.h>
+
+extern "C"
+{
+    char** environ = nullptr;
+
+    char* getenv(const char* key)
+    {
+        char** env = environ;
+        size_t len = strlen(key);
+
+        while (*env)
+        {
+            // Retrieve an environment variable from environ.
+            char* var = *(env++);
+
+            // Check for an equals sign, else we just skip this one.
+            char* delim = strchr(var, '=');
+            if (!delim) continue;
+
+            // Get the length of this variable's key (the part before the equals sign)
+            size_t key_length = strcspn(var, "=");
+            if (len != key_length) continue;
+
+            // If the keys match, we found it! Return the value (which is just after the equals sign)
+            if (!memcmp(key, var, key_length)) { return delim + 1; }
+        }
+
+        return nullptr;
+    }
+}

libc/src/init.cpp

@@ -1,10 +1,16 @@
+#include <luna/Ignore.h>
 #include <stdio.h>
 #include <unistd.h>
 
+extern char** environ;
+
 extern "C"
 {
-    void libc_init()
+    void libc_init(int argc, char** argv, int envc, char** envp)
     {
+        ignore(argc, argv, envc);
+        environ = envp;
+
         stdin = fdopen(STDIN_FILENO, "r");
         stdout = fdopen(STDOUT_FILENO, "w");
         stderr = fdopen(STDERR_FILENO, "w");

libc/src/unistd.cpp

@@ -9,6 +9,8 @@
 
 extern "C" long arch_invoke_syscall(long, uintptr_t, uintptr_t, uintptr_t, uintptr_t, uintptr_t);
 
+extern char** environ;
+
 extern "C"
 {
     pid_t fork(void)
@@ -29,7 +31,12 @@ extern "C"
 
     int execv(const char* path, char* const* argv)
     {
-        long rc = syscall(SYS_exec, path, argv);
+        return execve(path, argv, environ);
+    }
+
+    int execve(const char* path, char* const* argv, char* const* envp)
+    {
+        long rc = syscall(SYS_execve, path, argv, envp);
         __errno_return(rc, int);
     }
 

libluna/include/luna/Syscall.h

@@ -2,7 +2,7 @@
 
 #define enumerate_syscalls(_e)                                                                                         \
     _e(exit) _e(clock_gettime) _e(mmap) _e(munmap) _e(usleep) _e(open) _e(close) _e(read) _e(getpid) _e(write)         \
-        _e(lseek) _e(mkdir) _e(exec) _e(mknod) _e(fork) _e(waitpid) _e(getppid) _e(fcntl) _e(getdents)
+        _e(lseek) _e(mkdir) _e(execve) _e(mknod) _e(fork) _e(waitpid) _e(getppid) _e(fcntl) _e(getdents)
 
 enum Syscalls
 {