Kernel, libc, userspace: Implement command-line arguments (argv)

The only thing missing now is for sh to pass them on.

apps/Makefile

@@ -1,4 +1,4 @@
-APPS := init sym sh crash uname uptime hello ps ls
+APPS := init sym sh crash uname uptime hello ps ls args
 
 APPS_DIR := $(LUNA_ROOT)/apps
 APPS_SRC := $(APPS_DIR)/src

apps/src/args.c

@@ -0,0 +1,7 @@
+#include <stdio.h>
+#include <unistd.h>
+
+int main(int argc, char** argv)
+{
+    for (int i = 0; i < argc; i++) puts(argv[i]);
+}

apps/src/init.c

@@ -50,7 +50,8 @@ int main()
     }
     if (child == 0)
     {
-        execv("/bin/sh", NULL);
+        char* argv[] = {"/bin/sh", NULL};
+        execv(argv[0], argv);
         perror("execv");
         return 1;
     }

apps/src/sh.c

@@ -113,11 +113,15 @@ void command_execute(command* cmd)
                 char* buf = malloc(cmd->size + 6);
                 strlcpy(buf, "/bin/", 6);
                 strncat(buf, cmd->buffer, cmd->size);
-                execv(buf, NULL);
+                char* argv[] = {buf, NULL};
+                execv(argv[0], argv);
             }
         }
         else
-            execv(cmd->buffer, NULL);
+        {
+            char* argv[] = {cmd->buffer, NULL};
+            execv(argv[0], argv);
+        }
         perror(cmd->buffer);
         exit(127);
     }

kernel/include/std/errno.h

@@ -4,6 +4,7 @@
 #define ENOENT 2
 #define ESRCH 3
 #define EINTR 4
+#define E2BIG 7
 #define ENOEXEC 8
 #define EBADF 9
 #define EAGAIN 11

kernel/include/sys/Syscall.h

@@ -14,7 +14,7 @@
 #define SYS_read 9
 #define SYS_close 10
 #define SYS_seek 11
-#define SYS_exec 12
+#define SYS_execv 12
 #define SYS_fcntl 13
 #define SYS_mprotect 14
 #define SYS_clock 15
@@ -49,7 +49,7 @@ void sys_open(Context* context, const char* filename, int flags);
 void sys_read(Context* context, int fd, size_t size, char* buffer);
 void sys_close(Context* context, int fd);
 void sys_seek(Context* context, int fd, long offset, int whence);
-void sys_exec(Context* context, const char* pathname);
+void sys_execv(Context* context, const char* pathname, char** argv);
 void sys_fcntl(Context* context, int fd, int command, uintptr_t arg);
 void sys_mprotect(Context* context, void* address, size_t size, int prot);
 void sys_clock(Context* context);

kernel/src/sys/Syscall.cpp

@@ -23,7 +23,7 @@ void Syscall::entry(Context* context)
     case SYS_read: sys_read(context, (int)context->rdi, context->rsi, (char*)context->rdx); break;
     case SYS_close: sys_close(context, (int)context->rdi); break;
     case SYS_seek: sys_seek(context, (int)context->rdi, (long)context->rsi, (int)context->rdx); break;
-    case SYS_exec: sys_exec(context, (const char*)context->rdi); break;
+    case SYS_execv: sys_execv(context, (const char*)context->rdi, (char**)context->rsi); break;
     case SYS_fcntl: sys_fcntl(context, (int)context->rdi, (int)context->rsi, context->rdx); break;
     case SYS_mprotect: sys_mprotect(context, (void*)context->rdi, context->rsi, (int)context->rdx); break;
     case SYS_clock: sys_clock(context); break;

kernel/src/sys/exec.cpp

@@ -2,6 +2,7 @@
 
 #include "interrupts/Interrupts.h"
 #include "log/Log.h"
+#include "memory/Memory.h"
 #include "memory/MemoryManager.h"
 #include "memory/PMM.h"
 #include "memory/VMM.h"
@@ -56,7 +57,16 @@ void sys_fork(Context* context)
     return;
 }
 
-void sys_exec(Context* context, const char* pathname)
+void push_on_user_stack(uint64_t* rsp, char* value,
+                        size_t size) // FIXME: Handle segments of stack that extend beyond one page.
+{
+    (*rsp) -= size;
+    char* kvalue = (char*)VMM::get_physical(*rsp);
+    ASSERT(kvalue != (char*)UINT64_MAX);
+    memcpy(kvalue, value, size);
+}
+
+void sys_execv(Context* context, const char* pathname, char** argv)
 {
     char* kpathname = strdup_from_user(pathname);
     if (!kpathname)
@@ -97,6 +107,85 @@ void sys_exec(Context* context, const char* pathname)
         return;
     }
 
+    uint64_t kargc = 0;
+    char** kargv = nullptr;
+    char** arg;
+
+    auto free_kernel_argv_copy = [&]() {
+        for (uint64_t i = 0; i < kargc; i++)
+        {
+            if (kargv[i]) kfree(kargv[i]);
+        }
+        if (kargv) kfree(kargv);
+    };
+
+    do {
+        if (Memory::is_kernel_address((uintptr_t)argv))
+        {
+            free_kernel_argv_copy();
+            context->rax = -EFAULT;
+            return;
+        }
+        arg = (char**)VMM::get_physical((uint64_t)argv);
+        if (arg == (char**)UINT64_MAX)
+        {
+            free_kernel_argv_copy();
+            context->rax = -EFAULT;
+            return;
+        }
+        kargv = (char**)krealloc(kargv, (kargc + 1) * sizeof(char*));
+        if (!kargv)
+        {
+            free_kernel_argv_copy();
+            context->rax = -ENOMEM;
+            return;
+        }
+        if (*arg)
+        {
+            char* kcopy = strdup_from_user(*arg);
+            if (!kcopy)
+            {
+                free_kernel_argv_copy();
+                context->rax = -ENOMEM;
+                return;
+            }
+            kargv[kargc] = kcopy;
+        }
+        else
+        {
+            kargv[kargc] = nullptr;
+            break;
+        }
+        kargc++;
+        argv++;
+    } while (arg != nullptr);
+
+    kinfoln("Copied %lu arguments from user process", kargc);
+
+    size_t stack_size = 0;
+    for (uint64_t i = 0; i <= kargc; i++)
+    {
+        stack_size += sizeof(char*);
+        if (kargv[i]) { stack_size += strlen(kargv[i]); }
+    }
+
+    if (stack_size >
+        ((TASK_PAGES_IN_STACK / 2) *
+         PAGE_SIZE)) // FIXME: Maybe we should allocate a larger stack in this case, but still set a larger upper limit.
+    {
+        free_kernel_argv_copy();
+        context->rax = -E2BIG;
+        return;
+    }
+
+    char** user_argv = (char**)kcalloc(kargc + 1, sizeof(char*));
+    if (!user_argv)
+    {
+        free_kernel_argv_copy();
+        context->rax = -ENOMEM;
+        return;
+    }
+
     Interrupts::disable();
     ASSERT(!Interrupts::are_enabled()); // This part is pretty sensitive.
 
@@ -129,9 +218,29 @@ void sys_exec(Context* context, const char* pathname)
         if (file.close_on_exec()) { file.close(); }
     }
 
-    task->restore_context(context);
+    for (uint64_t i = 0; i <= kargc; i++)
+    {
+        if (kargv[i])
+        {
+            push_on_user_stack(&task->regs.rsp, kargv[i], strlen(kargv[i]) + 1);
+            user_argv[i] = (char*)task->regs.rsp;
+        }
+        else
+            user_argv[i] = nullptr;
+    }
+    push_on_user_stack(&task->regs.rsp, (char*)user_argv, (kargc + 1) * sizeof(char*));
+    task->regs.rdi = kargc;          // argc
+    task->regs.rsi = task->regs.rsp; // argv
+
+    task->regs.rsp &= (UINT64_MAX ^ 15); // align it
+
+    free_kernel_argv_copy();
+
+    kfree(user_argv);
 
     kfree(kpathname);
 
+    task->restore_context(context);
+
     return;
 }

libs/libc/crt0.asm

@@ -6,8 +6,6 @@ extern _fini
 extern initialize_libc
 extern exit
 
-extern __argv
-
 global _start
 _start:
 	; Set up end of the stack frame linked list.
@@ -16,12 +14,15 @@ _start:
 	push rbp ; rbp=0
 	mov rbp, rsp
 
+	push rdi
+	push rsi
+
 	call initialize_libc
 
 	call _init
 
-    mov rdi, 0 ; argc = 0
+	pop rsi ; argv
-    mov rsi, __argv ; Dummy argv which is equal to {NULL}
+	pop rdi ; argc
 
 	call main
 

libs/libc/include/errno.h

@@ -8,6 +8,7 @@ extern int errno;
 #define ENOENT 2      // No such file or directory
 #define ESRCH 3       // No such process
 #define EINTR 4       // Interrupted system call. Not implemented.
+#define E2BIG 7       // Argument list too long
 #define ENOEXEC 8     // Exec format error
 #define EBADF 9       // Bad file descriptor
 #define EAGAIN 11     // Resource temporarily unavailable

libs/libc/include/sys/syscall.h

@@ -13,7 +13,7 @@
 #define SYS_read 9
 #define SYS_close 10
 #define SYS_seek 11
-#define SYS_exec 12
+#define SYS_execv 12
 #define SYS_fcntl 13
 #define SYS_mprotect 14
 #define SYS_clock 15

libs/libc/include/unistd.h

@@ -20,9 +20,8 @@ extern "C"
 {
 #endif
 
-    /* Executes the program program. On success, does not return. The second parameter (arguments) is not implemented
+    /* Executes the program program, passing the arguments in the argument list argv. On success, does not return. */
-     * for now. You can pass NULL to it. */
+    int execv(const char* program, char* const argv[]);
-    int execv(const char* program, char* const[]);
 
     /* Not implemented. */
     int execve(const char*, char* const[], char* const[]);

libs/libc/src/init.cpp

@@ -4,8 +4,6 @@
 #include <stdlib.h>
 #include <unistd.h>
 
-__lc_used const char* __argv[] = {NULL}; // For now.
-
 static void terminate_libc()
 {
     fclose(stdout);

libs/libc/src/string.cpp

@@ -261,6 +261,7 @@ extern "C"
         case ENOENT: return "No such file or directory";
         case ESRCH: return "No such process";
         case EINTR: return "Interrupted system call";
+        case E2BIG: return "Argument list too long";
         case ENOEXEC: return "Exec format error";
         case EBADF: return "Bad file descriptor";
         case EAGAIN: return "Resource temporarily unavailable";

libs/libc/src/syscall.cpp

@@ -18,10 +18,10 @@ extern "C" long syscall(long number, ...)
     case SYS_exit:
     case SYS_getprocid:
     case SYS_close:
-    case SYS_exec:
     case SYS_mkdir:
     case SYS_sleep: result = __luna_syscall1(number, va_arg(ap, arg)); break;
     case SYS_munmap:
+    case SYS_execv:
     case SYS_access:
     case SYS_fstat:
     case SYS_stat:

libs/libc/src/unistd.cpp

@@ -8,9 +8,9 @@
 
 extern "C"
 {
-    int execv(const char* program, char* const[])
+    int execv(const char* program, char* const argv[])
     {
-        return (int)syscall(SYS_exec, program);
+        return (int)syscall(SYS_execv, program, argv);
     }
 
     int execve(const char*, char* const[], char* const[])