process struct: replace the generic saved_addr with an union

2 files changed, 15 insertions, 13 deletions

diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index 0efccde..5d9e7eb 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -24,11 +24,13 @@ struct process {
 
 	uint32_t id; // only for debugging, don't expose to userland
 
-	// meaning changes depending on the state
-	// PS_DEAD - death message
-	// PS_WAITS4CHILDDEATH - buffer for said message
-	user_ptr saved_addr;
-	size_t saved_len;
+	// saved value, meaning depends on .state
+	union {
+		struct { // PS_DEAD, PS_WAITS4CHILDDEATH
+			user_ptr buf;
+			size_t len;
+		} death_msg;
+	};
 
 	struct vfs_mount *mount;
 
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index ddc3d4b..124333a 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -17,11 +17,11 @@ _Noreturn static void await_finish(struct process *dead, struct process *listene
 	dead->state = PS_DEADER;
 	listener->state = PS_RUNNING;
 
-	len = listener->saved_len < dead->saved_len
-	    ? listener->saved_len : dead->saved_len;
+	len = listener->death_msg.len < dead->death_msg.len
+	    ? listener->death_msg.len : dead->death_msg.len;
 	res = virt_cpy(
-			listener->pages, listener->saved_addr,
-			dead->pages, dead->saved_addr, len);
+			listener->pages, listener->death_msg.buf,
+			dead->pages, dead->death_msg.buf, len);
 	regs_savereturn(&listener->regs, res ? len : -1);
 	process_switch(listener);
 }
@@ -29,8 +29,8 @@ _Noreturn static void await_finish(struct process *dead, struct process *listene
 
 _Noreturn void _syscall_exit(const user_ptr msg, size_t len) {
 	process_current->state = PS_DEAD;
-	process_current->saved_addr = msg;
-	process_current->saved_len  = len;
+	process_current->death_msg.buf = msg;
+	process_current->death_msg.len = len;
 
 	if (process_current->parent->state == PS_WAITS4CHILDDEATH)
 		await_finish(process_current, process_current->parent);
@@ -44,8 +44,8 @@ _Noreturn void _syscall_exit(const user_ptr msg, size_t len) {
 
 int _syscall_await(user_ptr buf, int len) {
 	process_current->state = PS_WAITS4CHILDDEATH;
-	process_current->saved_addr = buf;
-	process_current->saved_len  = len;
+	process_current->death_msg.buf = buf;
+	process_current->death_msg.len = len;
 
 	// find any already dead children
 	for (struct process *iter = process_current->child;