Merge "add new Linux close_range() system call to bionic" am: c66cb5ba6a

Original change: https://android-review.googlesource.com/c/platform/bionic/+/1957446

Change-Id: I45251562b5b51e8b19ed778607aad790c057d478
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

libc/SECCOMP_ALLOWLIST_COMMON.TXT

@@ -76,5 +76,3 @@ int futex_time64(int*, int, int, const timespec64*, int*, int) lp32
 int sched_rr_get_interval_time64(pid_t, timespec64*) lp32
 # Since Linux 5.4, not in glibc. Probed for and conditionally used by ART.
 int userfaultfd(int) all
-# Since Linux 5.9, used by POSIX_SPAWN_CLOEXEC_DEFAULT
-int close_range(unsigned int, unsigned int, int) all

libc/SYSCALLS.TXT

@@ -107,6 +107,7 @@ ssize_t     __preadv64v2:preadv2(int, const struct iovec*, int, long, long, int)
 ssize_t     __pwritev64v2:pwritev2(int, const struct iovec*, int, long, long, int) all
 
 int         __close:close(int)  all
+int         close_range(unsigned int, unsigned int, int) all
 pid_t       __getpid:getpid()  all
 int memfd_create(const char*, unsigned) all
 int         munmap(void*, size_t)  all

libc/bionic/spawn.cpp

@@ -52,7 +52,7 @@ static int set_cloexec(int i) {
 // mark all open fds except stdin/out/err as close-on-exec
 static int cloexec_except_stdioe() {
   // requires 5.11+ or ACK 5.10-T kernel, otherwise returns ENOSYS or EINVAL
-  if (!syscall(SYS_close_range, 3, ~0U, CLOSE_RANGE_CLOEXEC)) return 0;
+  if (!close_range(3, ~0U, CLOSE_RANGE_CLOEXEC)) return 0;
 
   // unfortunately getrlimit can lie:
   // - both soft and hard limits can be lowered to 0, with fds still open, so it can underestimate

libc/include/unistd.h

@@ -317,6 +317,22 @@ int setdomainname(const char* __name, size_t __n) __INTRODUCED_IN(26);
 void swab(const void* __src, void* __dst, ssize_t __byte_count) __INTRODUCED_IN(28);
 #endif
 
+/**
+ * [close_range(2)](https://man7.org/linux/man-pages/man2/close_range.2.html)
+ * performs an action (which depends on value of flags) on an inclusive range
+ * of file descriptors.
+ *
+ * Available since API level 34.
+ *
+ * Note: there is no emulation on too old kernels, hence this will fail with
+ * -1/ENOSYS on pre-5.9 kernels, -1/EINVAL for unsupported flags.  In particular
+ * CLOSE_RANGE_CLOEXEC requires 5.11, though support was backported to Android
+ * Common Kernel 5.10-T.
+ *
+ * Returns 0 on success, and returns -1 and sets `errno` on failure.
+ */
+int close_range(unsigned int __min_fd, unsigned int __max_fd, int __flags) __INTRODUCED_IN(34);
+
 #if defined(__BIONIC_INCLUDE_FORTIFY_HEADERS)
 #define _UNISTD_H_
 #include <bits/fortify/unistd.h>

libc/libc.map.txt

@@ -1576,6 +1576,11 @@ LIBC_T { # introduced=Tiramisu
     pwritev64v2;
 } LIBC_S;
 
+LIBC_U { # introduced=UpsideDownCake
+  global:
+    close_range;
+} LIBC_T;
+
 LIBC_PRIVATE {
   global:
     __accept4; # arm x86

tests/unistd_test.cpp

@@ -1648,3 +1648,23 @@ TEST(UNISTD_TEST, sleep) {
   auto t1 = std::chrono::steady_clock::now();
   ASSERT_GE(t1-t0, 1s);
 }
+
+TEST(UNISTD_TEST, close_range) {
+#if defined(__GLIBC__)
+  GTEST_SKIP() << "glibc too old";
+#else   // __GLIBC__
+  int fd = open("/proc/version", O_RDONLY);
+  ASSERT_GE(fd, 0);
+
+  // Try to close the file descriptor (this requires a 5.9+ kernel)
+  if (close_range(fd, fd, 0) == 0) {
+    // we can't close it *again*
+    ASSERT_EQ(close(fd), -1);
+    ASSERT_EQ(errno, EBADF);
+  } else {
+    ASSERT_EQ(errno, ENOSYS);
+    // since close_range() failed, we can close it normally
+    ASSERT_EQ(close(fd), 0);
+  }
+#endif  // __GLIBC__
+}