diff --git a/libc/bionic/bionic_call_ifunc_resolver.cpp b/libc/bionic/bionic_call_ifunc_resolver.cpp
index 410eb78..3cfb8b5 100644
--- a/libc/bionic/bionic_call_ifunc_resolver.cpp
+++ b/libc/bionic/bionic_call_ifunc_resolver.cpp
@@ -58,12 +58,12 @@
   }
   return reinterpret_cast<ifunc_resolver_t>(resolver_addr)(hwcap);
 #elif defined(__riscv)
-  // This argument and its value is just a placeholder for now,
-  // but it means that if we do pass something in future (such as
-  // getauxval() and/or hwprobe key/value pairs), callees will be able to
-  // recognize what they're being given.
-  typedef ElfW(Addr) (*ifunc_resolver_t)(void*);
-  return reinterpret_cast<ifunc_resolver_t>(resolver_addr)(nullptr);
+  // The pointer argument is currently unused, but reserved for future
+  // expansion. If we pass nullptr from the beginning, it'll be easier
+  // to recognize if/when we pass actual data (and matches glibc).
+  typedef ElfW(Addr) (*ifunc_resolver_t)(uint64_t, void*);
+  static uint64_t hwcap = getauxval(AT_HWCAP);
+  return reinterpret_cast<ifunc_resolver_t>(resolver_addr)(hwcap, nullptr);
 #else
   typedef ElfW(Addr) (*ifunc_resolver_t)(void);
   return reinterpret_cast<ifunc_resolver_t>(resolver_addr)();
diff --git a/libc/bionic/libc_init_static.cpp b/libc/bionic/libc_init_static.cpp
index d7a2856..a3c66d4 100644
--- a/libc/bionic/libc_init_static.cpp
+++ b/libc/bionic/libc_init_static.cpp
@@ -356,7 +356,7 @@
       if (memtag_stack) {
         void* pg_start =
             reinterpret_cast<void*>(page_start(reinterpret_cast<uintptr_t>(stack_top)));
-        if (mprotect(pg_start, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_MTE | PROT_GROWSDOWN)) {
+        if (mprotect(pg_start, page_size(), PROT_READ | PROT_WRITE | PROT_MTE | PROT_GROWSDOWN)) {
           async_safe_fatal("error: failed to set PROT_MTE on main thread stack: %m");
         }
       }
diff --git a/libc/bionic/pthread_internal.h b/libc/bionic/pthread_internal.h
index 7efbf6d..3b9e6a4 100644
--- a/libc/bionic/pthread_internal.h
+++ b/libc/bionic/pthread_internal.h
@@ -38,6 +38,8 @@
 #define __hwasan_thread_exit()
 #endif
 
+#include "platform/bionic/page.h"
+
 #include "private/bionic_elf_tls.h"
 #include "private/bionic_lock.h"
 #include "private/bionic_tls.h"
@@ -236,7 +238,7 @@
 // On LP64, we could use more but there's no obvious advantage to doing
 // so, and the various media processes use RLIMIT_AS as a way to limit
 // the amount of allocation they'll do.
-#define PTHREAD_GUARD_SIZE PAGE_SIZE
+#define PTHREAD_GUARD_SIZE max_page_size()
 
 // SIGSTKSZ (8KiB) is not big enough.
 // An snprintf to a stack buffer of size PATH_MAX consumes ~7KiB of stack.
diff --git a/libc/include/bits/page_size.h b/libc/include/bits/page_size.h
new file mode 100644
index 0000000..ca434e5
--- /dev/null
+++ b/libc/include/bits/page_size.h
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#if !defined(__BIONIC_NO_PAGE_SIZE_MACRO)
+#define PAGE_SIZE 4096
+#define PAGE_MASK (~(PAGE_SIZE - 1))
+#endif
+
+__END_DECLS
diff --git a/libc/include/pthread.h b/libc/include/pthread.h
index 1f08628..4feade5 100644
--- a/libc/include/pthread.h
+++ b/libc/include/pthread.h
@@ -34,6 +34,7 @@
  */
 
 #include <limits.h>
+#include <bits/page_size.h>
 #include <bits/pthread_types.h>
 #include <sched.h>
 #include <sys/cdefs.h>
@@ -73,9 +74,14 @@
 #define PTHREAD_BARRIER_SERIAL_THREAD (-1)
 #endif
 
+
 #if defined(__LP64__)
+#if defined(PAGE_SIZE)
 #define PTHREAD_STACK_MIN (4 * PAGE_SIZE)
 #else
+#define PTHREAD_STACK_MIN 65536
+#endif
+#else
 #define PTHREAD_STACK_MIN (2 * PAGE_SIZE)
 #endif
 
diff --git a/libc/include/setjmp.h b/libc/include/setjmp.h
index 6d047ae..0aaaac5 100644
--- a/libc/include/setjmp.h
+++ b/libc/include/setjmp.h
@@ -66,12 +66,14 @@
 /**
  * The size in words of a riscv64 jmp_buf. Room for callee-saved registers,
  * including floating point, stack pointer and program counter, various
- * internal implementation details, and leaving some free space.
+ * internal implementation details, and leaving lots of free space.
  *
- * Coincidentally matches OpenBSD, though they also save/restore the
- * floating point status register too.
+ * Deliberately very large given the uncertainty around the final form of
+ * hardware shadow stack, and the fact that x86-64 glibc needed to steal
+ * space from their enormous sigset_t (which we don't have) to be able to
+ * implement the CET shadow stack.
  */
-#define _JBLEN 32
+#define _JBLEN 64
 #elif defined(__x86_64__)
 /** The size in words of an x86-64 jmp_buf. Inherited from OpenBSD. */
 #define _JBLEN 11
diff --git a/libc/include/sys/user.h b/libc/include/sys/user.h
index 0ea0285..1d20034 100644
--- a/libc/include/sys/user.h
+++ b/libc/include/sys/user.h
@@ -32,12 +32,9 @@
 #include <stddef.h> /* For size_t. */
 #include <stdint.h>
 
-__BEGIN_DECLS
+#include <bits/page_size.h>
 
-#if !defined(__BIONIC_NO_PAGE_SIZE_MACRO)
-#define PAGE_SIZE 4096
-#define PAGE_MASK (~(PAGE_SIZE - 1))
-#endif
+__BEGIN_DECLS
 
 #if defined(__i386__)
 
diff --git a/tests/ifunc_test.cpp b/tests/ifunc_test.cpp
index e3c437e..1fdbf1a 100644
--- a/tests/ifunc_test.cpp
+++ b/tests/ifunc_test.cpp
@@ -60,6 +60,26 @@
   return ret42;
 }
 
+#elif defined(__riscv)
+
+#include <sys/hwprobe.h>
+
+static uint64_t g_hwcap;
+
+static riscv_hwprobe g_hwprobes[] = {{.key = RISCV_HWPROBE_KEY_IMA_EXT_0}};
+
+extern "C" fn_ptr_t hwcap_resolver(uint64_t hwcap, void* null) {
+  // Check hwcap like arm32/arm64.
+  g_hwcap = hwcap;
+
+  // For now, the pointer argument is reserved for future expansion.
+  if (null != NULL) abort();
+
+  // Ensure that __riscv_hwprobe() can be called from an ifunc.
+  if (__riscv_hwprobe(g_hwprobes, 1, 0, nullptr, 0) != 0) return nullptr;
+  return ret42;
+}
+
 #else
 
 extern "C" fn_ptr_t hwcap_resolver() {
@@ -81,6 +101,12 @@
   EXPECT_EQ(getauxval(AT_HWCAP2), g_arg._hwcap2);
 #elif defined(__arm__)
   EXPECT_EQ(getauxval(AT_HWCAP), g_hwcap);
+#elif defined(__riscv)
+  EXPECT_EQ(getauxval(AT_HWCAP), g_hwcap);
+
+  riscv_hwprobe probes[] = {{.key = RISCV_HWPROBE_KEY_IMA_EXT_0}};
+  ASSERT_EQ(0, __riscv_hwprobe(probes, 1, 0, nullptr, 0));
+  EXPECT_EQ(probes[0].value, g_hwprobes[0].value);
 #endif
 }