Fixup support for io_pgetevents_time64 syscall

This is a fixup for the original commit 5b5e2985f3
"Add support for io_pgetevents_time64 syscall" that didn't correctly
work for 32-bit architecutres with a 64-bit time_t that aren't RISC-V.

For a full discussion of the issue see:
5b5e2985f3

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14432)

engines/e_afalg.c

@@ -124,27 +124,56 @@ static ossl_inline int io_read(aio_context_t ctx, long n, struct iocb **iocb)
     return syscall(__NR_io_submit, ctx, n, iocb);
 }
 
+/* A version of 'struct timespec' with 32-bit time_t and nanoseconds.  */
+struct __timespec32
+{
+  __kernel_long_t tv_sec;
+  __kernel_long_t tv_nsec;
+};
+
 static ossl_inline int io_getevents(aio_context_t ctx, long min, long max,
                                struct io_event *events,
                                struct timespec *timeout)
 {
+#if defined(__NR_io_pgetevents_time64)
+    /* Check if we are a 32-bit architecture with a 64-bit time_t */
+    if (sizeof(*timeout) != sizeof(struct __timespec32)) {
+        int ret = syscall(__NR_io_pgetevents_time64, ctx, min, max, events,
+                          timeout, NULL);
+        if (ret == 0 || errno != ENOSYS)
+            return ret;
+    }
+#endif
+
 #if defined(__NR_io_getevents)
-    return syscall(__NR_io_getevents, ctx, min, max, events, timeout);
+    if (sizeof(*timeout) == sizeof(struct __timespec32))
-#elif defined(__NR_io_pgetevents_time64)
+        /*
-    /* Let's only support the 64 suffix syscalls for 64-bit time_t.
+         * time_t matches our architecture length, we can just use
-     * This simplifies the code for us as we don't need to use a 64-bit
+         * __NR_io_getevents
-     * version of timespec with a 32-bit time_t and handle converting
-     * between 64-bit and 32-bit times and check for overflows.
          */
-    if (sizeof(timeout->tv_sec) == 8)
+        return syscall(__NR_io_getevents, ctx, min, max, events, timeout);
-        return syscall(__NR_io_pgetevents_time64, ctx, min, max, events, timeout, NULL);
     else {
+        /*
+         * We don't have __NR_io_pgetevents_time64, but we are using a
+         * 64-bit time_t on a 32-bit architecture. If we can fit the
+         * timeout value in a 32-bit time_t, then let's do that
+         * and then use the __NR_io_getevents syscall.
+         */
+        if (timeout && timeout->tv_sec == (long)timeout->tv_sec) {
+            struct __timespec32 ts32;
+
+            ts32.tv_sec = (__kernel_long_t) timeout->tv_sec;
+            ts32.tv_nsec = (__kernel_long_t) timeout->tv_nsec;
+
+            return syscall(__NR_io_getevents, ctx, min, max, events, ts32);
+        } else {
+            return syscall(__NR_io_getevents, ctx, min, max, events, NULL);
+        }
+    }
+#endif
+
     errno = ENOSYS;
     return -1;
-    }
-#else
-# error "We require either the io_getevents syscall or __NR_io_pgetevents_time64."
-#endif
 }
 
 static void afalg_waitfd_cleanup(ASYNC_WAIT_CTX *ctx, const void *key,