feat: implement utime libc function, SYS_UTIME syscall, filesystem support (ext2 only)

kernel/src/Fs/Boot.cpp

@@ -101,6 +101,7 @@ namespace Fs {
             .GetLabel  = RdGetLabel,
             .ReadDirAt = RdReadDirAt,
             .Stat      = RdStat,
+            .SetTimes  = nullptr,
             // Statically allocated: nothing to release.
             .Unmount   = nullptr,
         };

kernel/src/Fs/Ext2.cpp

@@ -1234,6 +1234,31 @@ namespace Fs::Ext2 {
         return 0;
     }
 
+    static int SetTimesImpl(int inst, const char* path, int64_t atime, int64_t mtime) {
+        if (InstanceAt(inst) == nullptr) return -4;
+        if (atime < 0 || atime > 0xFFFFFFFFLL ||
+            mtime < 0 || mtime > 0xFFFFFFFFLL) return -3;
+        auto& self = g_instances[inst];
+
+        uint32_t inodeNum;
+        Inode inode;
+        if (!TraversePath(self, path, &inodeNum, &inode)) return -1;
+
+        inode.i_atime = (uint32_t)atime;
+        inode.i_mtime = (uint32_t)mtime;
+        inode.i_ctime = Ext2Now();
+        if (!WriteInode(self, inodeNum, &inode)) return -4;
+
+        // Open files cache their inode. Keep every alias coherent so a later
+        // write through an existing handle cannot restore stale metadata.
+        for (int i = 0; i < MaxFilesPerInstance; i++) {
+            if (self.files[i].inUse && self.files[i].inodeNum == inodeNum) {
+                self.files[i].inode = inode;
+            }
+        }
+        return 0;
+    }
+
     static int ReadImpl(int inst, int handle, uint8_t* buffer,
                          uint64_t offset, uint64_t size) {
         if (InstanceAt(inst) == nullptr) return -1;
@@ -1830,6 +1855,7 @@ namespace Fs::Ext2 {
     static int DrvRename(void* c, const char* o, const char* n) { return RenameImpl(CtxToInst(c), o, n); }
     static const char* DrvGetLabel(void* c) { return GetLabelImpl(CtxToInst(c)); }
     static int DrvStat(void* c, const char* p, Vfs::StatInfo* o) { return StatImpl(CtxToInst(c), p, o); }
+    static int DrvSetTimes(void* c, const char* p, int64_t a, int64_t m) { return SetTimesImpl(CtxToInst(c), p, a, m); }
 
     // Release everything the mount owns. The driver is either not registered
     // yet, or the VFS has deactivated its drive and drained dispatches.
@@ -2040,6 +2066,7 @@ namespace Fs::Ext2 {
             .GetLabel  = DrvGetLabel,
             .ReadDirAt = DrvReadDirAt,
             .Stat      = DrvStat,
+            .SetTimes  = DrvSetTimes,
             .Unmount   = DrvUnmount,
         };
 

kernel/src/Fs/Fat32.cpp

@@ -2099,6 +2099,7 @@ namespace Fs::Fat32 {
             .GetLabel  = DrvGetLabel,
             .ReadDirAt = DrvReadDirAt,
             .Stat      = DrvStat,
+            .SetTimes  = nullptr,
             .Unmount   = DrvUnmount,
         };
 

kernel/src/Fs/Vfs.cpp

@@ -307,6 +307,21 @@ namespace Fs::Vfs {
         return result;
     }
 
+    int VfsSetTimes(const char* path, int64_t atime, int64_t mtime) {
+        int drive;
+        const char* localPath;
+
+        if (!ParsePath(path, drive, localPath)) return -1;
+
+        vfsLock.Acquire();
+        FsDriver* driver = DriverForLocked(drive);
+        int result = (driver != nullptr && driver->SetTimes != nullptr)
+            ? driver->SetTimes(driver->ctx, localPath, atime, mtime)
+            : -2;
+        vfsLock.Release();
+        return result;
+    }
+
     int VfsMkdir(const char* path) {
         int drive;
         const char* localPath;

kernel/src/Fs/Vfs.hpp

@@ -65,6 +65,10 @@ namespace Fs::Vfs {
         // Optional: fill metadata for a path. Drivers that leave this null do
         // not support stat and VfsStat returns -1 for their paths.
         int (*Stat)(void* ctx, const char* path, StatInfo* out);
+        // Optional: set access and modification times for a path. Return 0 on
+        // success, -1 for a missing path, -3 for an unrepresentable time, or
+        // -4 for an I/O error. A null hook yields -2 (unsupported).
+        int (*SetTimes)(void* ctx, const char* path, int64_t atime, int64_t mtime);
         // Optional: release everything this mount owns, including the FsDriver
         // itself. Called either when registration fails, before the driver has
         // become reachable, or by UnregisterDrive once the slot is deactivated
@@ -90,6 +94,7 @@ namespace Fs::Vfs {
 
     int VfsDelete(const char* path);
     int VfsStat(const char* path, StatInfo& out);
+    int VfsSetTimes(const char* path, int64_t atime, int64_t mtime);
     int VfsReadDir(const char* path, const char** outNames, int maxEntries);
     int VfsReadDirAt(const char* path, const char** outNames, int maxEntries, int startIndex);
     int VfsMkdir(const char* path);