diff --git a/libc/config/linux/riscv64/entrypoints.txt b/libc/config/linux/riscv64/entrypoints.txt
--- a/libc/config/linux/riscv64/entrypoints.txt
+++ b/libc/config/linux/riscv64/entrypoints.txt
@@ -431,6 +431,14 @@
     libc.src.signal.sigfillset
     libc.src.signal.signal
 
+    # spawn.h entrypoints
+    libc.src.spawn.posix_spawn
+    libc.src.spawn.posix_spawn_file_actions_addclose
+    libc.src.spawn.posix_spawn_file_actions_adddup2
+    libc.src.spawn.posix_spawn_file_actions_addopen
+    libc.src.spawn.posix_spawn_file_actions_destroy
+    libc.src.spawn.posix_spawn_file_actions_init
+
     # threads.h entrypoints
     libc.src.threads.call_once
     libc.src.threads.cnd_broadcast
diff --git a/libc/config/linux/riscv64/headers.txt b/libc/config/linux/riscv64/headers.txt
--- a/libc/config/linux/riscv64/headers.txt
+++ b/libc/config/linux/riscv64/headers.txt
@@ -9,6 +9,7 @@
     libc.include.pthread
     libc.include.sched
     libc.include.signal
+    libc.include.spawn
     libc.include.stdio
     libc.include.stdlib
     libc.include.string
diff --git a/libc/src/spawn/linux/posix_spawn.cpp b/libc/src/spawn/linux/posix_spawn.cpp
--- a/libc/src/spawn/linux/posix_spawn.cpp
+++ b/libc/src/spawn/linux/posix_spawn.cpp
@@ -14,6 +14,7 @@
 #include "src/spawn/file_actions.h"
 
 #include <fcntl.h>
+#include <signal.h> // For SIGCHLD
 #include <spawn.h>
 #include <sys/syscall.h> // For syscall numbers.
 
@@ -50,8 +51,15 @@
 
 void close(int fd) { __llvm_libc::syscall_impl(SYS_close, fd); }
 
+// We use dup3 if dup2 is not available, similar to our implementation of dup2
 bool dup2(int fd, int newfd) {
+#ifdef SYS_dup2
   long ret = __llvm_libc::syscall_impl(SYS_dup2, fd, newfd);
+#elif defined(SYS_dup3)
+  long ret = __llvm_libc::syscall_impl(SYS_dup3, fd, newfd, 0);
+#else
+#error "SYS_dup2 and SYS_dup3 not available for the target."
+#endif
   return ret < 0 ? false : true;
 }