Initial Upload

exec.c

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+#include "types.h"
+#include "param.h"
+#include "memlayout.h"
+#include "mmu.h"
+#include "proc.h"
+#include "defs.h"
+#include "x86.h"
+#include "elf.h"
+
+void cleanupexec(pde_t * pgdir, struct inode *ip) {
+    if (pgdir) {
+        freevm(pgdir);
+    }
+    if (ip) {
+        iunlockput(ip);
+        end_op();
+    }    
+}
+
+int exec(char *path, char **argv) {
+    char *s, *last;
+    int i, off;
+    uint argc, sz, sp, ustack[3 + MAXARG + 1];
+    struct elfhdr elf;
+    struct inode *ip;
+    struct proghdr ph;
+    pde_t *pgdir, *oldpgdir;
+    struct proc *curproc = myproc();
+
+    begin_op();
+
+    if ((ip = namei(path)) == 0) {
+        end_op();
+        cprintf("exec: fail\n");
+        return -1;
+    }
+    ilock(ip);
+    pgdir = 0;
+
+    // Check ELF header
+    if (readi(ip, (char*)&elf, 0, sizeof(elf)) != sizeof(elf)) {
+        cleanupexec(pgdir, ip);
+        return -1;
+    }
+    if (elf.magic != ELF_MAGIC) {
+        cleanupexec(pgdir, ip);
+        return -1;        
+    }
+
+    if ((pgdir = setupkvm()) == 0) {
+        cleanupexec(pgdir, ip);
+        return -1;    
+    }
+
+    // Load program into memory.
+    sz = 0;
+    for (i = 0, off = elf.phoff; i < elf.phnum; i++, off += sizeof(ph)) {
+        if (readi(ip, (char*)&ph, off, sizeof(ph)) != sizeof(ph)) {
+            cleanupexec(pgdir, ip);
+            return -1;    
+        }
+        if (ph.type != ELF_PROG_LOAD) {
+            continue;
+        }
+        if (ph.memsz < ph.filesz) {
+            cleanupexec(pgdir, ip);
+            return -1;    
+        }
+        if (ph.vaddr + ph.memsz < ph.vaddr) {
+            cleanupexec(pgdir, ip);
+            return -1;    
+        }
+        if ((sz = allocuvm(pgdir, sz, ph.vaddr + ph.memsz)) == 0) {
+            cleanupexec(pgdir, ip);
+            return -1;    
+        }
+        if (ph.vaddr % PGSIZE != 0) {
+            cleanupexec(pgdir, ip);
+            return -1;    
+        }
+        if (loaduvm(pgdir, (char*)ph.vaddr, ip, ph.off, ph.filesz) < 0) {
+            cleanupexec(pgdir, ip);
+            return -1;    
+        }
+    }
+    iunlockput(ip);
+    end_op();
+    ip = 0;
+
+    // Allocate two pages at the next page boundary.
+    // Make the first inaccessible.  Use the second as the user stack.
+    sz = PGROUNDUP(sz);
+    if ((sz = allocuvm(pgdir, sz, sz + 2 * PGSIZE)) == 0) {
+        cleanupexec(pgdir, ip);
+        return -1;    
+    }
+    clearpteu(pgdir, (char*)(sz - 2 * PGSIZE));
+    sp = sz;
+
+    // Push argument strings, prepare rest of stack in ustack.
+    for (argc = 0; argv[argc]; argc++) {
+        if (argc >= MAXARG) {
+            cleanupexec(pgdir, ip);
+            return -1;    
+        }
+        sp = (sp - (strlen(argv[argc]) + 1)) & ~3;
+        if (copyout(pgdir, sp, argv[argc], strlen(argv[argc]) + 1) < 0) {
+            cleanupexec(pgdir, ip);
+            return -1;    
+        }
+        ustack[3 + argc] = sp;
+    }
+    ustack[3 + argc] = 0;
+
+    ustack[0] = 0xffffffff;  // fake return PC
+    ustack[1] = argc;
+    ustack[2] = sp - (argc + 1) * 4;  // argv pointer
+
+    sp -= (3 + argc + 1) * 4;
+    if (copyout(pgdir, sp, ustack, (3 + argc + 1) * 4) < 0) {
+        cleanupexec(pgdir, ip);
+        return -1;    
+    }
+
+    // Save program name for debugging.
+    for (last = s = path; *s; s++) {
+        if (*s == '/') {
+            last = s + 1;
+        }
+    }
+    safestrcpy(curproc->name, last, sizeof(curproc->name));
+
+    // Commit to the user image.
+    oldpgdir = curproc->pgdir;
+    curproc->pgdir = pgdir;
+    curproc->sz = sz;
+    curproc->tf->eip = elf.entry;  // main
+    curproc->tf->esp = sp;
+    switchuvm(curproc);
+    freevm(oldpgdir);
+    return 0;
+}