Implement getrlimit(RLIMIT_NOFILE) (#23774)

Also, remove the unnecessary setrlimit and ugetrlimit syscalls. Musl
will use __syscall_prlimit64 instead of both of these (See
musl/src/misc/getrlimit.c and musl/src/misc/setrlimit.c).

Author: sbc100

system/lib/libc/emscripten_syscall_stubs.c

@@ -126,10 +126,6 @@ weak int __syscall_umask(int mask) {
   return old;
 }
 
-weak int __syscall_setrlimit(int resource, intptr_t limit) {
-  return 0; // no-op
-}
-
 weak int __syscall_getrusage(int who, intptr_t usage) {
   REPORT(getrusage);
   struct rusage *u = (struct rusage *)usage;
@@ -228,21 +224,23 @@ weak int __syscall_munlockall() {
 weak int __syscall_prlimit64(int pid, int resource, intptr_t new_limit, intptr_t old_limit) {
   REPORT(prlimit64);
   struct rlimit *old = (struct rlimit *)old_limit;
-  if (old) { // just report no limits
-    old->rlim_cur = RLIM_INFINITY;
-    old->rlim_max = RLIM_INFINITY;
+  if (new_limit) {
+    return -EPERM;
+  }
+  if (old) {
+    if (resource == RLIMIT_NOFILE) {
+      // See FS.MAX_OPEN_FDS in src/lib/libfs.js
+      old->rlim_cur = 4096;
+      old->rlim_max = 4096;
+    } else {
+      // Just report no limits
+      old->rlim_cur = RLIM_INFINITY;
+      old->rlim_max = RLIM_INFINITY;
+    }
   }
   return 0;
 }
 
-weak int __syscall_ugetrlimit(int resource, intptr_t rlim) {
-  REPORT(ugetrlimit);
-  struct rlimit * limits = (struct rlimit *)rlim;
-  limits->rlim_cur = RLIM_INFINITY;
-  limits->rlim_max = RLIM_INFINITY;
-  return 0; // just report no limits
-}
-
 weak int __syscall_setsockopt(int sockfd, int level, int optname, intptr_t optval, size_t optlen, int dummy) {
   REPORT(setsockopt);
   return -ENOPROTOOPT; // The option is unknown at the level indicated.

system/lib/libc/musl/arch/emscripten/bits/syscall.h

@@ -12,7 +12,6 @@
 #define SYS_umask		 __syscall_umask
 #define SYS_getppid		 __syscall_getppid
 #define SYS_setsid		 __syscall_setsid
-#define SYS_setrlimit		 __syscall_setrlimit
 #define SYS_getrusage		 __syscall_getrusage
 #define SYS_munmap		 __syscall_munmap
 #define SYS_fchmod		 __syscall_fchmod
@@ -35,7 +34,6 @@
 #define SYS_mremap		__syscall_mremap
 #define SYS_poll		__syscall_poll
 #define SYS_getcwd		__syscall_getcwd
-#define SYS_ugetrlimit		__syscall_ugetrlimit
 #define SYS_mmap2		__syscall_mmap2
 #define SYS_truncate64		__syscall_truncate64
 #define SYS_ftruncate64	__syscall_ftruncate64

system/lib/libc/musl/arch/emscripten/syscall_arch.h

@@ -29,7 +29,6 @@ int __syscall_umask(int mask);
 int __syscall_getppid(void);
 int __syscall_getpgrp(void);
 int __syscall_setsid(void);
-int __syscall_setrlimit(int resource, intptr_t limit);
 int __syscall_getrusage(int who, intptr_t usage);
 int __syscall_munmap(intptr_t addr, size_t len);
 int __syscall_fchmod(int fd, int mode);
@@ -53,7 +52,6 @@ int __syscall_munlockall(void);
 int __syscall_mremap(intptr_t old_addr, size_t old_size, size_t new_size, int flags, intptr_t new_addr);
 int __syscall_poll(intptr_t fds, int nfds, int timeout);
 int __syscall_getcwd(intptr_t buf, size_t size);
-int __syscall_ugetrlimit(int resource, intptr_t rlim);
 intptr_t __syscall_mmap2(intptr_t addr, size_t len, int prot, int flags, int fd, off_t offset);
 int __syscall_truncate64(intptr_t path, off_t length);
 int __syscall_ftruncate64(int fd, off_t length);

test/other/test_rlimit.c

@@ -0,0 +1,22 @@
+#include <assert.h>
+#include <errno.h>
+#include <stdio.h>
+#include <sys/resource.h>
+
+int main() {
+  struct rlimit rlim;
+
+  assert(getrlimit(RLIMIT_NOFILE, &rlim) == 0);
+  printf("RLIMIT_NOFILE: rlim_cur: %lld\n", rlim.rlim_cur);
+  printf("RLIMIT_NOFILE: rlim_max: %lld\n", rlim.rlim_max);
+
+  assert(getrlimit(RLIMIT_CORE, &rlim) == 0);
+  printf("RLIMIT_CORE: rlim_cur: %lld\n", rlim.rlim_cur);
+  printf("RLIMIT_CORE: rlim_max: %lld\n", rlim.rlim_max);
+
+  // setrlimit should always fail with EPERM
+  assert(setrlimit(RLIMIT_NOFILE, &rlim) == -1);
+  assert(errno == EPERM);
+
+  return 0;
+}

test/other/test_rlimit.out

@@ -0,0 +1,4 @@
+RLIMIT_NOFILE: rlim_cur: 4096
+RLIMIT_NOFILE: rlim_max: 4096
+RLIMIT_CORE: rlim_cur: -1
+RLIMIT_CORE: rlim_max: -1

test/test_other.py

@@ -15696,3 +15696,6 @@ def test_rollup(self):
     self.run_process([EMCC, test_file('hello_world.c'), '-sEXPORT_ES6', '-sEXIT_RUNTIME', '-sENVIRONMENT=node', '-sMODULARIZE', '-o', 'hello.mjs'])
     self.run_process(shared.get_npm_cmd('rollup') + ['--config'])
     self.assertContained('hello, world!', self.run_js('bundle.mjs'))
+
+  def test_rlimit(self):
+    self.do_other_test('test_rlimit.c', emcc_args=['-O1'])