Kernel+LibC+UserspaceEmulator: Remove sys$dup() and sys$dup2()

We can just implement these in userspace, so yay two less syscalls!
fleximus · Aug 14, 2020 · bf247fb · bf247fb
1 parent 5f3d384
commit bf247fb
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Showing 7 changed files with 15 additions and 74 deletions.
diff --git a/DevTools/UserspaceEmulator/Emulator.cpp b/DevTools/UserspaceEmulator/Emulator.cpp
@@ -253,8 +253,6 @@ u32 Emulator::virt_syscall(u32 function, u32 arg1, u32 arg2, u32 arg3)
  switch (function) {
  case SC_chdir:
  return virt$chdir(arg1, arg2);
- case SC_dup2:
- return virt$dup2(arg1, arg2);
  case SC_access:
  return virt$access(arg1, arg2, arg3);
  case SC_waitid:
@@ -1350,9 +1348,4 @@ int Emulator::virt$chdir(FlatPtr path, size_t path_length)
  return syscall(SC_chdir, host_path.data(), host_path.size());
 }
 
-int Emulator::virt$dup2(int old_fd, int new_fd)
-{
- return syscall(SC_dup2, old_fd, new_fd);
-}
-
 }
diff --git a/DevTools/UserspaceEmulator/Emulator.h b/DevTools/UserspaceEmulator/Emulator.h
@@ -138,7 +138,6 @@ class Emulator {
  ssize_t virt$getrandom(FlatPtr buffer, size_t buffer_size, unsigned int flags);
  int virt$sleep(unsigned);
  int virt$chdir(FlatPtr, size_t);
- int virt$dup2(int, int);
  int virt$getpgrp();
  int virt$getpgid(pid_t);
  int virt$setpgid(pid_t pid, pid_t pgid);

diff --git a/Kernel/API/Syscall.h b/Kernel/API/Syscall.h
@@ -86,8 +86,6 @@ namespace Kernel {
  S(getpgrp) \
  S(fork) \
  S(execve) \
- S(dup) \
- S(dup2) \
  S(sigaction) \
  S(umask) \
  S(getgroups) \

diff --git a/Kernel/CMakeLists.txt b/Kernel/CMakeLists.txt
@@ -100,7 +100,6 @@ set(KERNEL_SOURCES
  Syscalls/clock.cpp
  Syscalls/debug.cpp
  Syscalls/disown.cpp
- Syscalls/dup.cpp
  Syscalls/execve.cpp
  Syscalls/exit.cpp
  Syscalls/fcntl.cpp

diff --git a/Kernel/Process.h b/Kernel/Process.h
@@ -258,8 +258,6 @@ class Process
  int sys$ptsname(int fd, Userspace<char*>, size_t);
  pid_t sys$fork(RegisterState&);
  int sys$execve(Userspace<const Syscall::SC_execve_params*>);
- int sys$dup(int oldfd);
- int sys$dup2(int oldfd, int newfd);
  int sys$sigaction(int signum, const sigaction* act, sigaction* old_act);
  int sys$sigprocmask(int how, Userspace<const sigset_t*> set, Userspace<sigset_t*> old_set);
  int sys$sigpending(Userspace<sigset_t*>);

diff --git a/Kernel/Syscalls/dup.cpp b/Kernel/Syscalls/dup.cpp
diff --git a/Libraries/LibC/unistd.cpp b/Libraries/LibC/unistd.cpp
@@ -410,14 +410,25 @@ int isatty(int fd)
 
 int dup(int old_fd)
 {
- int rc = syscall(SC_dup, old_fd);
- __RETURN_WITH_ERRNO(rc, rc, -1);
+ return fcntl(old_fd, F_DUPFD, 0);
 }
 
 int dup2(int old_fd, int new_fd)
 {
- int rc = syscall(SC_dup2, old_fd, new_fd);
- __RETURN_WITH_ERRNO(rc, rc, -1);
+ if (new_fd < 0) {
+ errno = EBADF;
+ return -1;
+ }
+
+ if (old_fd == new_fd)
+ return old_fd;
+
+ // Validate `old_fd` so we don't close `new_fd` and then fail the `F_DUPFD`.
+ if (fcntl(old_fd, F_GETFL) < 0)
+ return -1;
+
+ close(new_fd);
+ return fcntl(old_fd, F_DUPFD, new_fd);
 }
 
 int setgroups(size_t size, const gid_t* list)