SYS_ppoll fallback

Author: nickdesaulniers

libc/config/linux/aarch64/entrypoints.txt

@@ -32,6 +32,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.fcntl.open
     libc.src.fcntl.openat
 
+    # poll.h entrypoints
+    libc.src.poll.poll
+
     # sched.h entrypoints
     libc.src.sched.sched_get_priority_max
     libc.src.sched.sched_get_priority_min

libc/config/linux/arm/entrypoints.txt

@@ -20,6 +20,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     # errno.h entrypoints
     libc.src.errno.errno
 
+    # poll.h entrypoints
+    libc.src.poll.poll
+
     # string.h entrypoints
     libc.src.string.memccpy
     libc.src.string.memchr

libc/config/linux/riscv/entrypoints.txt

@@ -32,6 +32,9 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.fcntl.open
     libc.src.fcntl.openat
 
+    # poll.h entrypoints
+    libc.src.poll.poll
+
     # sched.h entrypoints
     libc.src.sched.sched_get_priority_max
     libc.src.sched.sched_get_priority_min

libc/src/poll/linux/CMakeLists.txt

@@ -7,6 +7,7 @@ add_entrypoint_object(
   DEPENDS
     libc.hdr.types.nfds_t
     libc.hdr.types.struct_pollfd
+    libc.hdr.types.struct_timespec
     libc.include.poll
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil

libc/src/poll/linux/poll.cpp

@@ -10,17 +10,35 @@
 
 #include "hdr/types/nfds_t.h"
 #include "hdr/types/struct_pollfd.h"
+#include "hdr/types/struct_timespec.h"
 #include "src/__support/OSUtil/syscall.h" // syscall_impl
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
 #include "src/errno/libc_errno.h"
 
-#include <sys/syscall.h> // SYS_poll
+#include <sys/syscall.h> // SYS_poll, SYS_ppoll
 
 namespace LIBC_NAMESPACE_DECL {
 
 LLVM_LIBC_FUNCTION(int, poll, (struct pollfd * fds, nfds_t nfds, int timeout)) {
+
+#ifdef SYS_poll
   int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_poll, fds, nfds, timeout);
+#elif defined(SYS_ppoll)
+  struct timespec ts, *tsp;
+  if (timeout >= 0) {
+    ts.tv_sec = timeout / 1000;
+    ts.tv_nsec = (timeout % 1000) * 1000000;
+    tsp = &ts;
+  } else {
+    tsp = nullptr;
+  }
+  int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_ppoll, fds, nfds, tsp,
+                                              nullptr, 0);
+#else
+#error "SYS_ppoll_time64?"
+#endif
+
   if (ret < 0) {
     libc_errno = -ret;
     return -1;