From d4ec702fafe437f1ef094112991a5a870f083529 Mon Sep 17 00:00:00 2001
From: Norman Maurer <norman_maurer@apple.com>
Date: Thu, 5 Dec 2019 09:01:59 +0100
Subject: [PATCH] Correctly take architecture into account when define syscalls
 for recvmmsg and sendmmsg usage (#9844)

Motivation:

https://github.com/netty/netty/pull/9797 changed the code for recvmmsg and sendmmsg to use the syscalls directly to remvove the dependency on newer GLIBC versions. Unfortunally it made the assumption that the syscall numbers are the same for different architectures, which is not the case.

Thanks to @jayv for pointing it out

Modifications:

Add #if, #elif and #else declarations to ensure we pick the correct syscall number (or not support if if the architecture is not supported atm).

Result:

Pick the correct syscall number depending on the architecture.
---
 .../src/main/c/netty_epoll_native.c           | 24 +++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/transport-native-epoll/src/main/c/netty_epoll_native.c b/transport-native-epoll/src/main/c/netty_epoll_native.c
index 06c923d970..a480d90d08 100644
--- a/transport-native-epoll/src/main/c/netty_epoll_native.c
+++ b/transport-native-epoll/src/main/c/netty_epoll_native.c
@@ -66,12 +66,30 @@ struct mmsghdr {
 
 // All linux syscall numbers are stable so this is safe.
 #ifndef SYS_recvmmsg
+// Only support SYS_recvmmsg for __x86_64__ / __i386__ for now
+#if defined(__x86_64__)
+// See https://github.com/torvalds/linux/blob/v5.4/arch/x86/entry/syscalls/syscall_64.tbl
 #define SYS_recvmmsg 299
+#elif defined(__i386__)
+// See https://github.com/torvalds/linux/blob/v5.4/arch/x86/entry/syscalls/syscall_32.tbl
+#define SYS_recvmmsg 337
+#else
+#define SYS_recvmmsg -1
 #endif
+#endif // SYS_recvmmsg
 
 #ifndef SYS_sendmmsg
+// Only support SYS_sendmmsg for __x86_64__ / __i386__ for now
+#if defined(__x86_64__)
+// See https://github.com/torvalds/linux/blob/v5.4/arch/x86/entry/syscalls/syscall_64.tbl
 #define SYS_sendmmsg 307
+#elif defined(__i386__)
+// See https://github.com/torvalds/linux/blob/v5.4/arch/x86/entry/syscalls/syscall_32.tbl
+#define SYS_sendmmsg 345
+#else
+#define SYS_sendmmsg -1
 #endif
+#endif // SYS_sendmmsg
 
 // Those are initialized in the init(...) method and cached for performance reasons
 static jfieldID packetAddrFieldId = NULL;
@@ -400,6 +418,9 @@ static jstring netty_epoll_native_kernelVersion(JNIEnv* env, jclass clazz) {
     return NULL;
 }
 static jboolean netty_epoll_native_isSupportingSendmmsg(JNIEnv* env, jclass clazz) {
+    if (SYS_sendmmsg == -1) {
+        return JNI_FALSE;
+    }
     if (syscall(SYS_sendmmsg, -1, NULL, 0, 0) == -1) {
         if (errno == ENOSYS) {
             return JNI_FALSE;
@@ -409,6 +430,9 @@ static jboolean netty_epoll_native_isSupportingSendmmsg(JNIEnv* env, jclass claz
 }
 
 static jboolean netty_epoll_native_isSupportingRecvmmsg(JNIEnv* env, jclass clazz) {
+    if (SYS_recvmmsg == -1) {
+        return JNI_FALSE;
+    }
     if (syscall(SYS_recvmmsg, -1, NULL, 0, 0, NULL) == -1) {
         if (errno == ENOSYS) {
             return JNI_FALSE;