diff --git a/liblfi/arch/x64/arch_sys.h b/liblfi/arch/x64/arch_sys.h
index 8094ca67..4f0d4f1e 100644
--- a/liblfi/arch/x64/arch_sys.h
+++ b/liblfi/arch/x64/arch_sys.h
@@ -25,6 +25,9 @@ enum {
     TUX_SYS_readv              = 19,
     TUX_SYS_writev             = 20,
     TUX_SYS_access             = 21,
+    TUX_SYS_dup                = 32,
+    TUX_SYS_dup2               = 33,
+    TUX_SYS_dup3               = 292,
     TUX_SYS_sched_yield        = 24,
     TUX_SYS_mremap             = 25,
     TUX_SYS_madvise            = 28,
@@ -82,6 +85,7 @@ enum {
     TUX_SYS_unlinkat           = 263,
     TUX_SYS_renameat           = 264,
     TUX_SYS_readlinkat         = 267,
+    TUX_SYS_fchmodat           = 268,
     TUX_SYS_faccessat          = 269,
     TUX_SYS_set_robust_list    = 273,
     TUX_SYS_utimensat          = 280,
diff --git a/liblfi/sys.c b/liblfi/sys.c
index 0b3e424d..0ca03a4d 100644
--- a/liblfi/sys.c
+++ b/liblfi/sys.c
@@ -27,6 +27,8 @@ syshandle(struct TuxThread* p, uintptr_t sysno, uintptr_t a0, uintptr_t a1,
     SYS(brk,               sys_brk(proc, a0))
     SYS(openat,            sys_openat(proc, a0, a1, a2, a3))
     SYS(close,             sys_close(proc, a0))
+    SYS(dup,               sys_dup(proc, a0))
+    SYS(dup3,              sys_dup3(proc, a0, a1, a2))
     SYS(writev,            sys_writev(proc, a0, a1, a2))
     SYS(readv,             sys_readv(proc, a0, a1, a2))
     SYS(pread64,           sys_pread64(proc, a0, a1, a2, a3))
@@ -37,6 +39,7 @@ syshandle(struct TuxThread* p, uintptr_t sysno, uintptr_t a0, uintptr_t a1,
     SYS(newfstatat,        sys_newfstatat(proc, a0, a1, a2, a3))
     SYS(fstat,             sys_newfstatat(proc, a0, 0, a1, TUX_AT_EMPTY_PATH))
     SYS(fchmod,            sys_fchmod(proc, a0, a1))
+    SYS(fchmodat,          sys_fchmodat(proc, a0, a1, a2, a3))
     SYS(truncate,          sys_truncate(proc, a0, a1))
     SYS(ftruncate,         sys_ftruncate(proc, a0, a1))
     SYS(fchown,            sys_fchown(proc, a0, a1, a2))
diff --git a/liblfi/syscalls/strace.c b/liblfi/syscalls/strace.c
index f4d32959..6ef7af85 100644
--- a/liblfi/syscalls/strace.c
+++ b/liblfi/syscalls/strace.c
@@ -14,6 +14,8 @@ sysname(uint64_t sysno)
     STRACE_CASE(brk)
     STRACE_CASE(openat)
     STRACE_CASE(close)
+    STRACE_CASE(dup)
+    STRACE_CASE(dup3)
     STRACE_CASE(writev)
     STRACE_CASE(readv)
     STRACE_CASE(pread64)
@@ -25,6 +27,7 @@ sysname(uint64_t sysno)
     STRACE_CASE(getrandom)
     STRACE_CASE(clock_gettime)
     STRACE_CASE(ioctl)
+    STRACE_CASE(fcntl)
     STRACE_CASE(set_tid_address)
     STRACE_CASE(set_robust_list)
     STRACE_CASE(uname)
diff --git a/liblfi/syscalls/sys_fcntl.c b/liblfi/syscalls/sys_fcntl.c
index bba07435..562422ac 100644
--- a/liblfi/syscalls/sys_fcntl.c
+++ b/liblfi/syscalls/sys_fcntl.c
@@ -1,11 +1,61 @@
 #include <assert.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
 
 #include "syscalls/syscalls.h"
+#include "fd.h"
+#include "file.h"
+#include "host.h"
+#include "host/posix/file.h"
 
 int
 sys_fcntl(struct TuxProc* p, int fd, int cmd, uintptr_t va0, uintptr_t va1,
         uintptr_t va2, uintptr_t va3)
 {
-    WARN(p->tux, "fcntl ignored");
-    return 0;
+    switch (cmd) {
+    case F_DUPFD: {
+        int minfd = va0;
+        struct FDFile* FD_DEFER(f) = fdget(&p->fdtable, fd);
+        if (!f)
+            return -TUX_EBADF;
+        
+        // Find the lowest available fd >= minfd
+        for (int newfd = minfd; newfd < TUX_NOFILE; newfd++) {
+            if (!fdhas(&p->fdtable, newfd)) {
+                fdassign(&p->fdtable, newfd, f);
+                return newfd;
+            }
+        }
+        return -TUX_EMFILE;
+    }
+    
+    case F_DUPFD_CLOEXEC:
+        // Close-on-exec not supported yet
+        return -TUX_ENOSYS;
+    
+    case F_GETFD:
+    case F_SETFD:
+    case F_GETFL:
+    case F_SETFL: {
+        struct FDFile* FD_DEFER(f) = fdget(&p->fdtable, fd);
+        if (!f)
+            return -TUX_EBADF;
+        
+        // Get the underlying host file descriptor
+        struct HostFile* hf = f->file ? f->file(f->dev) : NULL;
+        if (!hf)
+            return -TUX_EBADF;
+        
+        // Pass through to system fcntl
+        int result = fcntl(hf->fd, cmd, va0);
+        if (result < 0)
+            return -errno;
+        return result;
+    }
+    
+    default:
+        WARN(p->tux, "fcntl command %d not implemented", cmd);
+        return -TUX_ENOSYS;
+    }
 }
diff --git a/liblfi/syscalls/sys_file.c b/liblfi/syscalls/sys_file.c
index bd6aeba1..76abe3a7 100644
--- a/liblfi/syscalls/sys_file.c
+++ b/liblfi/syscalls/sys_file.c
@@ -142,6 +142,42 @@ sys_close(struct TuxProc* p, int fd)
     return 0;
 }
 
+int
+sys_dup(struct TuxProc* p, int oldfd)
+{
+    struct FDFile* FD_DEFER(f) = fdget(&p->fdtable, oldfd);
+    if (!f)
+        return -TUX_EBADF;
+
+    int newfd = fdalloc(&p->fdtable);
+    if (newfd < 0)
+        return -TUX_EMFILE;
+
+    fdassign(&p->fdtable, newfd, f);
+    return newfd;
+}
+
+int
+sys_dup3(struct TuxProc* p, int oldfd, int newfd, int flags)
+{
+    if (oldfd == newfd)
+        return -TUX_EINVAL;
+
+    struct FDFile* FD_DEFER(f) = fdget(&p->fdtable, oldfd);
+    if (!f)
+        return -TUX_EBADF;
+
+    if (newfd < 0 || newfd >= TUX_NOFILE)
+        return -TUX_EBADF;
+
+    if (flags != 0 && flags != TUX_O_CLOEXEC)
+        return -TUX_EINVAL;
+
+    fdremove(&p->fdtable, newfd);
+    fdassign(&p->fdtable, newfd, f);
+    return newfd;
+}
+
 ssize_t
 sys_readlinkat(struct TuxProc* p, int dirfd, lfiptr_t pathp, lfiptr_t bufp, size_t size)
 {
@@ -322,6 +358,18 @@ sys_fchmod(struct TuxProc* p, int fd, tux_mode_t mode)
     return f->chmod(f->dev, mode);
 }
 
+int
+sys_fchmodat(struct TuxProc* p, int dirfd, lfiptr_t pathp, tux_mode_t mode, int flags)
+{
+    struct HostFile* dir = getfdir(p, dirfd);
+    if (dirfd != TUX_AT_FDCWD && !dir)
+        return -TUX_EBADF;
+    const char* path = procpath(p, pathp);
+    if (!path)
+        return -TUX_EFAULT;
+    return host_fchmodat(dir, path, mode, flags);
+}
+
 int
 sys_fsync(struct TuxProc* p, int fd)
 {
diff --git a/liblfi/syscalls/syscalls.h b/liblfi/syscalls/syscalls.h
index b0d97ec2..09fb378d 100644
--- a/liblfi/syscalls/syscalls.h
+++ b/liblfi/syscalls/syscalls.h
@@ -104,6 +104,10 @@ ssize_t sys_readlink(struct TuxProc* p, lfiptr_t pathp, lfiptr_t bufp, size_t si
 
 int sys_close(struct TuxProc* p, int fd);
 
+int sys_dup(struct TuxProc* p, int oldfd);
+
+int sys_dup3(struct TuxProc* p, int oldfd, int newfd, int flags);
+
 ssize_t sys_read(struct TuxProc* p, int fd, lfiptr_t bufp, size_t size);
 
 ssize_t sys_readv(struct TuxProc* p, int fd, lfiptr_t iovp, size_t iovcnt);
@@ -122,6 +126,8 @@ int sys_fchmod(struct TuxProc* p, int fd, tux_mode_t mode);
 
 int sys_chmod(struct TuxProc* p, uintptr_t pathp, tux_mode_t mode);
 
+int sys_fchmodat(struct TuxProc* p, int dirfd, lfiptr_t pathp, tux_mode_t mode, int flags);
+
 int sys_fchown(struct TuxProc* p, int fd, tux_uid_t owner, tux_gid_t group);
 
 int sys_chown(struct TuxProc* p, uintptr_t pathp, tux_uid_t owner, tux_gid_t group);
diff --git a/liblfi/test/meson.build b/liblfi/test/meson.build
index 6b8941a2..b4f762db 100644
--- a/liblfi/test/meson.build
+++ b/liblfi/test/meson.build
@@ -11,7 +11,12 @@ test('test_init', executable(
   dependencies: [liblfi_dep]
 ), suite: ['liblfi'])
 
-lficc = find_program(cpu + '-lfi-linux-musl-clang', required: false)
+lficc = find_program([
+  cpu + '-lfi-linux-musl-clang',
+  '/opt/aarch64-lfi-clang-new/lfi-clang/' + cpu + '-lfi-linux-musl-clang',
+  '/opt/aarch64-lfi-clang/lfi-clang/' + cpu + '-lfi-linux-musl-clang',
+  '/opt/lfi/bin/' + cpu + '-lfi-linux-musl-clang'
+], required: false)
 if not lficc.found()
   warning('lficc not found: cannot test liblfi')
   subdir_done()
@@ -49,6 +54,8 @@ testdata = [
   {'bin': test_tux, 'file': 'tux/file.c', 'inputs': ['tux/inputs/file.txt'], 'cflags': []},
   {'bin': test_tux, 'file': 'tux/chdir.c', 'inputs': ['tux/inputs', 'file.txt'], 'cflags': []},
   {'bin': test_tux, 'file': 'tux/thread.c', 'inputs': [], 'cflags': []},
+  {'bin': test_tux, 'file': 'tux/dup.c', 'inputs': [], 'cflags': []},
+  {'bin': test_tux, 'file': 'tux/fcntl.c', 'inputs': [], 'cflags': []},
   {'bin': test_fs, 'file': 'tux/fs.c', 'inputs': '/proc/self/test.txt', 'cflags': []}
 ]
 
diff --git a/liblfi/test/tux/dup.c b/liblfi/test/tux/dup.c
new file mode 100644
index 00000000..5df2c16f
--- /dev/null
+++ b/liblfi/test/tux/dup.c
@@ -0,0 +1,40 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+
+int main() {
+    // Test dup() syscall
+    int fd1 = open("/dev/null", O_WRONLY);
+    if (fd1 < 0) {
+        printf("failed to open /dev/null\n");
+        return 1;
+    }
+    
+    int fd2 = dup(fd1);
+    if (fd2 < 0) {
+        printf("dup() failed\n");
+        return 1;
+    }
+    
+    printf("dup: original fd=%d, dup fd=%d\n", fd1, fd2);
+    
+    // Test dup3() syscall
+    int fd3 = 10; // arbitrary target fd
+    int fd4 = dup3(fd1, fd3, 0);
+    if (fd4 != fd3) {
+        printf("dup3() failed: expected %d, got %d\n", fd3, fd4);
+        return 1;
+    }
+    
+    printf("dup3: original fd=%d, target fd=%d\n", fd1, fd3);
+    
+    // Test writing to all fds to verify they work
+    const char* msg = "test\n";
+    write(fd1, msg, strlen(msg));
+    write(fd2, msg, strlen(msg));
+    write(fd3, msg, strlen(msg));
+    
+    printf("dup test passed\n");
+    return 0;
+}
\ No newline at end of file
diff --git a/liblfi/test/tux/dup.c.out b/liblfi/test/tux/dup.c.out
new file mode 100644
index 00000000..c1cc119e
--- /dev/null
+++ b/liblfi/test/tux/dup.c.out
@@ -0,0 +1,3 @@
+dup: original fd=3, dup fd=4
+dup3: original fd=3, target fd=10
+dup test passed
diff --git a/liblfi/test/tux/fchmodat_test.c b/liblfi/test/tux/fchmodat_test.c
new file mode 100644
index 00000000..8798f69c
--- /dev/null
+++ b/liblfi/test/tux/fchmodat_test.c
@@ -0,0 +1,105 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <fcntl.h>
+
+int main() {
+    const char* testfile = "fchmodat_test_file.txt";
+    const char* testdir = "fchmodat_test_dir";
+    
+    // Create a test directory
+    if (mkdir(testdir, 0755) != 0 && errno != EEXIST) {
+        fprintf(stderr, "Failed to create test directory: %s\n", strerror(errno));
+        return 1;
+    }
+    
+    // Create a test file in the directory
+    char filepath[256];
+    snprintf(filepath, sizeof(filepath), "%s/%s", testdir, testfile);
+    FILE* f = fopen(filepath, "w");
+    if (!f) {
+        fprintf(stderr, "Failed to create test file: %s\n", strerror(errno));
+        rmdir(testdir);
+        return 1;
+    }
+    fprintf(f, "test content\n");
+    fclose(f);
+    
+    // Open the directory for fchmodat
+    int dirfd = open(testdir, O_RDONLY);
+    if (dirfd < 0) {
+        fprintf(stderr, "Failed to open test directory: %s\n", strerror(errno));
+        unlink(filepath);
+        rmdir(testdir);
+        return 1;
+    }
+    
+    // Test fchmodat - make file read-only using directory fd
+    printf("Testing fchmodat to make file read-only...\n");
+    if (fchmodat(dirfd, testfile, 0444, 0) != 0) {
+        fprintf(stderr, "fchmodat failed: %s\n", strerror(errno));
+        close(dirfd);
+        unlink(filepath);
+        rmdir(testdir);
+        return 1;
+    }
+    
+    // Verify the permissions changed
+    struct stat st;
+    if (stat(filepath, &st) != 0) {
+        fprintf(stderr, "stat failed: %s\n", strerror(errno));
+        close(dirfd);
+        unlink(filepath);
+        rmdir(testdir);
+        return 1;
+    }
+    
+    if ((st.st_mode & 0777) == 0444) {
+        printf("fchmodat test PASSED - file is now read-only\n");
+    } else {
+        printf("fchmodat test FAILED - expected mode 0444, got %o\n", st.st_mode & 0777);
+        close(dirfd);
+        unlink(filepath);
+        rmdir(testdir);
+        return 1;
+    }
+    
+    // Test fchmodat with AT_FDCWD
+    printf("Testing fchmodat with AT_FDCWD...\n");
+    if (fchmodat(AT_FDCWD, filepath, 0644, 0) != 0) {
+        fprintf(stderr, "fchmodat with AT_FDCWD failed: %s\n", strerror(errno));
+        close(dirfd);
+        unlink(filepath);
+        rmdir(testdir);
+        return 1;
+    }
+    
+    // Verify the permissions changed back
+    if (stat(filepath, &st) != 0) {
+        fprintf(stderr, "stat failed: %s\n", strerror(errno));
+        close(dirfd);
+        unlink(filepath);
+        rmdir(testdir);
+        return 1;
+    }
+    
+    if ((st.st_mode & 0777) == 0644) {
+        printf("fchmodat with AT_FDCWD test PASSED - file is now writable\n");
+    } else {
+        printf("fchmodat with AT_FDCWD test FAILED - expected mode 0644, got %o\n", st.st_mode & 0777);
+        close(dirfd);
+        unlink(filepath);
+        rmdir(testdir);
+        return 1;
+    }
+    
+    // Clean up
+    close(dirfd);
+    unlink(filepath);
+    rmdir(testdir);
+    printf("All fchmodat tests PASSED\n");
+    return 0;
+}
\ No newline at end of file
diff --git a/liblfi/test/tux/fchmodat_test.c.out b/liblfi/test/tux/fchmodat_test.c.out
new file mode 100644
index 00000000..63780ea5
--- /dev/null
+++ b/liblfi/test/tux/fchmodat_test.c.out
@@ -0,0 +1,5 @@
+Testing fchmodat to make file read-only...
+fchmodat test PASSED - file is now read-only
+Testing fchmodat with AT_FDCWD...
+fchmodat with AT_FDCWD test PASSED - file is now writable
+All fchmodat tests PASSED
diff --git a/liblfi/test/tux/fcntl.c b/liblfi/test/tux/fcntl.c
new file mode 100644
index 00000000..2595574c
--- /dev/null
+++ b/liblfi/test/tux/fcntl.c
@@ -0,0 +1,80 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+
+int main() {
+    // Test fcntl() syscall
+    int fd1 = open("/dev/null", O_WRONLY);
+    if (fd1 < 0) {
+        printf("failed to open /dev/null\n");
+        return 1;
+    }
+    
+    // Test F_DUPFD - duplicate fd with minimum fd number
+    int fd2 = fcntl(fd1, F_DUPFD, 5);
+    if (fd2 < 0) {
+        printf("fcntl F_DUPFD failed\n");
+        return 1;
+    }
+    if (fd2 < 5) {
+        printf("fcntl F_DUPFD returned fd %d, expected >= 5\n", fd2);
+        return 1;
+    }
+    
+    printf("fcntl F_DUPFD: original fd=%d, dup fd=%d\n", fd1, fd2);
+    
+    // Test F_GETFL - get file status flags
+    int flags = fcntl(fd1, F_GETFL);
+    if (flags < 0) {
+        printf("fcntl F_GETFL failed\n");
+        return 1;
+    }
+    
+    printf("fcntl F_GETFL: fd=%d has flags=0x%x\n", fd1, flags);
+    
+    // Test F_GETFD - get file descriptor flags
+    int fd_flags = fcntl(fd1, F_GETFD);
+    if (fd_flags < 0) {
+        printf("fcntl F_GETFD failed\n");
+        return 1;
+    }
+    
+    printf("fcntl F_GETFD: fd=%d has fd_flags=0x%x\n", fd1, fd_flags);
+    
+    // Test F_SETFD - set file descriptor flags (should work)
+    int result = fcntl(fd1, F_SETFD, FD_CLOEXEC);
+    if (result < 0) {
+        printf("fcntl F_SETFD failed\n");
+        return 1;
+    }
+    
+    // Verify the flag was set
+    fd_flags = fcntl(fd1, F_GETFD);
+    if (fd_flags < 0) {
+        printf("fcntl F_GETFD after F_SETFD failed\n");
+        return 1;
+    }
+    
+    printf("fcntl F_SETFD: fd=%d now has fd_flags=0x%x\n", fd1, fd_flags);
+    
+    // Test F_DUPFD_CLOEXEC - should return ENOSYS
+    int fd3 = fcntl(fd1, F_DUPFD_CLOEXEC, 8);
+    if (fd3 >= 0) {
+        printf("fcntl F_DUPFD_CLOEXEC should have failed but returned fd=%d\n", fd3);
+        return 1;
+    }
+    
+    printf("fcntl F_DUPFD_CLOEXEC correctly returned error (not supported)\n");
+    
+    // Test writing to duplicated fd to verify it works
+    const char* msg = "test\n";
+    write(fd1, msg, strlen(msg));
+    write(fd2, msg, strlen(msg));
+    
+    close(fd1);
+    close(fd2);
+    
+    printf("fcntl test passed\n");
+    return 0;
+}
\ No newline at end of file
diff --git a/liblfi/test/tux/fcntl.c.out b/liblfi/test/tux/fcntl.c.out
new file mode 100644
index 00000000..80ad22c1
--- /dev/null
+++ b/liblfi/test/tux/fcntl.c.out
@@ -0,0 +1,6 @@
+fcntl F_DUPFD: original fd=3, dup fd=5
+fcntl F_GETFL: fd=3 has flags=0x20001
+fcntl F_GETFD: fd=3 has fd_flags=0x0
+fcntl F_SETFD: fd=3 now has fd_flags=0x1
+fcntl F_DUPFD_CLOEXEC correctly returned error (not supported)
+fcntl test passed