dev(sell): add simple libc and implement shell

please see the log for detail.

1 files changed, 210 insertions, 0 deletions

diff --git a/src/kernel/proc/exec.cc b/src/kernel/proc/exec.cc
new file mode 100644
index 0000000..d0e75ef
--- /dev/null
+++ b/src/kernel/proc/exec.cc
@@ -0,0 +1,210 @@
+#include "common/types.h"
+#include "kernel/riscv.h"
+#include "kernel/proc.h"
+#include "kernel/mm.h"
+#include "kernel/elf.h"
+#include "fs/fs.h"
+#include "lib/string.h"
+#include "drivers/uart.h"
+#include "kernel/trap.h"
+#include "drivers/uart.h"
+
+extern char trampoline[];
+
+// RAII: Page Table Resource Management
+class VmGuard
+{
+public:
+    uint64 *pagetable = nullptr;
+    uint64 sz = 0;
+
+    VmGuard() : pagetable(VM::uvmcreate()) {}
+
+    ~VmGuard()
+    {
+        if (pagetable)
+        {
+            VM::uvmfree(pagetable, sz);
+        }
+    }
+
+    // Copying is prohibited
+    VmGuard(const VmGuard &) = delete;
+    VmGuard &operator=(const VmGuard &) = delete;
+
+    // Submit resources: Ownership transfer, destructor no longer releases
+    uint64 *commit()
+    {
+        uint64 *pt = pagetable;
+        pagetable = nullptr;
+        return pt;
+    }
+};
+
+// RAII: Inode Lock Management
+class InodeGuard
+{
+public:
+    Inode *ip;
+    InodeGuard(Inode *i) : ip(i)
+    {
+        if (ip)
+            VFS::ilock(ip);
+    }
+    ~InodeGuard()
+    {
+        if (ip)
+        {
+            VFS::iunlockput(ip); // Automatically unlock and release references
+        }
+    }
+    // Copying is prohibited
+    InodeGuard(const InodeGuard &) = delete;
+    InodeGuard &operator=(const InodeGuard &) = delete;
+};
+
+// laod segment
+static int loadseg(uint64 *pagetable, uint64 va, Inode *ip, uint64 offset, uint64 sz)
+{
+    for (uint64 i = 0; i < sz; i += PGSIZE)
+    {
+        uint64 pa = VM::walkaddr(pagetable, va + i);
+        if (pa == 0)
+            return -1;
+
+        uint64 n = PGSIZE - (va + i) % PGSIZE;
+        if (i + n > sz)
+            n = sz - i;
+
+        // Read physical address (isUser=0)
+        if (ip->read((char *)(pa + (va + i) % PGSIZE), offset + i, n, 0) != (int)n)
+            return -1;
+    }
+    return 0;
+}
+
+namespace Exec
+{
+    int exec(char *path, char **argv)
+    {
+        // Get Inode
+        Inode *raw_ip = VFS::namei(path);
+        if (!raw_ip)
+            return -1;
+        InodeGuard iguard(raw_ip);
+
+        // Get ELF head
+        struct elfhdr elf;
+        if (raw_ip->read((char *)&elf, 0, sizeof(elf), 0) != sizeof(elf))
+            return -1;
+        if (elf.magic != ELF_MAGIC)
+            return -1;
+        // Create new pagetable
+        VmGuard vm_guard;
+        if (!vm_guard.pagetable)
+            return -1;
+        // Load Program Segment
+        struct proghdr ph;
+        for (int i = 0; i < elf.phnum; i++)
+        {
+            uint64 off = elf.phoff + i * sizeof(ph);
+            if (raw_ip->read((char *)&ph, off, sizeof(ph), 0) != sizeof(ph))
+                return -1;
+
+            if (ph.type != ELF_PROG_LOAD)
+                continue;
+            if (ph.memsz < ph.filesz)
+                return -1;
+            if (ph.vaddr + ph.memsz < ph.vaddr)
+                return -1;
+
+            uint64 sz1 = VM::uvmalloc(vm_guard.pagetable, vm_guard.sz, ph.vaddr + ph.memsz, PTE_W | PTE_X | PTE_R | PTE_U);
+            if (sz1 == 0)
+                return -1;
+            vm_guard.sz = sz1;
+
+            if (loadseg(vm_guard.pagetable, ph.vaddr, raw_ip, ph.off, ph.filesz) < 0)
+                return -1;
+        }
+
+        // Prepare user stack
+        uint64 sz = PGROUNDUP(vm_guard.sz);
+        uint64 sz1 = VM::uvmalloc(vm_guard.pagetable, sz, sz + 2 * PGSIZE, PTE_W | PTE_R | PTE_U);
+        if (sz1 == 0)
+            return -1;
+        vm_guard.sz = sz1;
+
+        VM::uvmunmap(vm_guard.pagetable, sz1 - 2 * PGSIZE, 1, 0); // protected pagetable
+
+        uint64 sp = sz1;
+        uint64 stackbase = sp - PGSIZE;
+        uint64 ustack[32];
+        uint64 argc = 0;
+
+        // Push parameter string
+        for (; argv[argc]; argc++)
+        {
+            if (argc >= 31)
+                return -1;
+            sp -= strlen(argv[argc]) + 1;
+            sp -= sp % 16;
+            if (sp < stackbase)
+                return -1;
+
+            if (VM::copyout(vm_guard.pagetable, sp, argv[argc], strlen(argv[argc]) + 1) < 0)
+                return -1;
+            ustack[argc] = sp;
+        }
+        ustack[argc] = 0;
+
+        // Push into parameter array
+        sp -= (argc + 1) * sizeof(uint64);
+        sp -= sp % 16;
+        if (sp < stackbase)
+            return -1;
+        if (VM::copyout(vm_guard.pagetable, sp, (char *)ustack, (argc + 1) * sizeof(uint64)) < 0)
+            return -1;
+
+        // Commit Changes
+        struct Proc *p = myproc();
+        if (VM::mappages(vm_guard.pagetable, TRAPFRAME, PGSIZE, (uint64)p->tf, PTE_R | PTE_W) < 0)
+            return -1;
+
+        uint64 oldsz = p->sz;
+        uint64 *oldpagetable = p->pagetable;
+
+        // setup Trapframe
+        p->tf->a0 = argc;
+        p->tf->a1 = sp;
+        p->tf->sp = sp;
+        p->tf->epc = elf.entry;
+
+        // update process name
+        char *s = path, *last = path;
+        while (*s)
+        {
+            if (*s == '/')
+                last = s + 1;
+            s++;
+        }
+        // memmove(p->name, last, sizeof(p->name));
+        size_t len = 0;
+        while (last[len] && len < sizeof(p->name) - 1)
+        {
+            p->name[len] = last[len];
+            len++;
+        }
+        p->name[len] = '\0';
+
+        // change pagetable
+        p->pagetable = vm_guard.commit();
+        p->sz = vm_guard.sz;
+
+        // release old pagetable
+        VM::uvmfree(oldpagetable, oldsz);
+
+        asm volatile("fence.i");
+
+        return 0; // iguard unlocks and releases IP upon destruction
+    }
+}
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