Allow for syscall with empty implementation to hide warning message

so3/kernel/syscalls.c

@@ -36,12 +36,24 @@ extern uint32_t __get_syscall_stack_arg(uint32_t nr);
 
 extern void test_malloc(int test_no);
 
+static long __sys_empty(syscall_args_t *args);
+
 static const syscall_fn_t syscall_table[NR_SYSCALLS] = {
 	[0 ... NR_SYSCALLS - 1] = NULL,
 /* Generated file with table element matching number to functions. */
 #include <generated/syscall_table.h.in>
 };
 
+/**
+ * Callback for syscalls with empty implementation to remove the unhandled message for them.
+ * This is useful as MUSL will use some syscalls that aren't implemented in SO3 due to simplification
+ * over Linux.
+ */
+static long __sys_empty(syscall_args_t *args)
+{
+	return -ENOSYS;
+}
+
 /*
  * Process syscalls according to the syscall number passed in r7 on ARM and x8 on ARM64.
  * According to SO3 ABI, the syscall arguments are passed in r0-r5 on ARM and x0-x5 on ARM64.

so3/scripts/syscall_gen.sh

@@ -24,6 +24,9 @@
 #  - syscall.tbl: Declares all syscalls available on SO3 without taking into
 #                 account the CPU arch. This also provides configuration
 #                 requirement for a given syscall.
+#                 Requirement can be set to EMPTY_IMPLEMENTATION, which will
+#                 set a default function returning -ENOSYS for syscalls that
+#                 are intentionally not implemented.
 #  - syscall.h.in: Contains all syscall number which are necessary implemented
 #                  in SO3. This is a copy of the same file from musl library.
 #
@@ -81,9 +84,13 @@ file_header "__SYSCALL_TABLE_H__" > "$outfile_table"
 valid_syscalls="$(grep -E "^[^#]" "$infile_table")"
 while read name requirement; do
 	sys_cond["$name"]="$requirement"
-	
+
 	echo "#ifdef SYSCALL_$name"
-	echo -e "\t[SYSCALL_$name] = &__sys_$name,"
+	if [ "$requirement" = "EMPTY_IMPLEMENTATION" ]; then
+		echo -e "\t[SYSCALL_$name] = &__sys_empty,"
+	else
+		echo -e "\t[SYSCALL_$name] = &__sys_$name,"
+	fi
 	echo "#endif"
 done < <(echo "$valid_syscalls") >> "$outfile_table"
 
@@ -100,13 +107,13 @@ grep -E "^#define " "$infile_number" | sed "s/^#define __NR_//" | {
 			continue
 		fi
 
-		if [ -n "${sys_cond[$name]}" ]; then
+		if [ -n "${sys_cond[$name]}" -a "${sys_cond[$name]}" != "EMPTY_IMPLEMENTATION" ]; then
 			echo "#ifdef CONFIG_${sys_cond[$name]}"
 		fi
 
 		echo "#define SYSCALL_$name $number"
 
-		if [ -n "${sys_cond[$name]}" ]; then
+		if [ -n "${sys_cond[$name]}" -a "${sys_cond[$name]}" != "EMPTY_IMPLEMENTATION" ]; then
 			echo "#endif"
 		fi
 	done

so3/syscall.tbl

@@ -68,3 +68,9 @@ send                    NET
 sendto                  NET
 setsockopt              NET
 brk                     PROC_ENV
+
+# TODO: implement. Heavily used in MUSL, so remove warning about it for now.
+munmap                  EMPTY_IMPLEMENTATION
+
+# mprotect allows to set memory protection (read/write/execute), which isn't supported.
+mprotect                EMPTY_IMPLEMENTATION