From 2a16c1f6f9118e7127d532421ae19b959b3f1d87 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sat, 20 Aug 2022 00:00:52 +0200
Subject: user/libc: don't access the old stack from the new thread at all

---
 src/user/app/tests/kernel/threads.c | 12 +++++++++-
 src/user/lib/thread.S               | 46 +++++++++++++++++++++++++++++++------
 src/user/lib/thread.c               | 11 ---------
 src/user/lib/thread.h               |  9 ++++++--
 4 files changed, 57 insertions(+), 21 deletions(-)
 delete mode 100644 src/user/lib/thread.c

diff --git a/src/user/app/tests/kernel/threads.c b/src/user/app/tests/kernel/threads.c
index 2964883..cb7111d 100644
--- a/src/user/app/tests/kernel/threads.c
+++ b/src/user/app/tests/kernel/threads.c
@@ -18,7 +18,6 @@ static void test_basic_thread(void) {
 	test(global_n == 10);
 }
 
-
 handle_t global_h;
 static void shared_handle(void *sem) {
 	handle_t ends[2];
@@ -39,7 +38,18 @@ static void test_shared_handle(void) {
 	test(!strcmp("Hello!", buf));
 }
 
+static void many_thread(void *arg) {
+	*(uint64_t*)arg += 10;
+}
+static void test_many_threads(void) {
+	uint64_t n = 0;
+	for (int i = 0; i < 10; i++) thread_create(0, many_thread, &n);
+	for (int i = 0; i < 10; i++) _syscall_await();
+	test(n == 100);
+}
+
 void r_k_threads(void) {
 	run_test(test_basic_thread);
 	run_test(test_shared_handle);
+	run_test(test_many_threads);
 }
diff --git a/src/user/lib/thread.S b/src/user/lib/thread.S
index 3cd3500..1a27c30 100644
--- a/src/user/lib/thread.S
+++ b/src/user/lib/thread.S
@@ -1,8 +1,40 @@
+#define ASM_FILE 1
+#include <camellia/syscalls.h>
+#include <camellia/flags.h>
+
 .section .text
-.global chstack
-.type chstack, @function
-// _Noreturn void chstack(void *arg, void (*fn)(void*), void *esp);
-chstack:
-	mov %rdx, %rsp
-	call *%rsi
-	jmp 0 // "exit"
+.global thread_creates
+.type thread_creates, @function
+// void thread_creates(int flags, void (*fn)(void*), void *arg, void *stack);
+thread_creates:
+	push %r12
+	push %r13
+	push %r14
+
+	/* save fn, arg, stack */
+	mov %rsi, %r12
+	mov %rdx, %r13
+	mov %rcx, %r14
+
+	mov %rdi, %rsi
+	or $(FORK_SHAREMEM | FORK_SHAREHANDLE), %rsi
+	mov $_SYSCALL_FORK, %rdi
+	xor %rdx, %rdx
+	syscall
+
+	test %rax, %rax
+	jz 1f
+	/* in parent, return normally */
+	pop %r14
+	pop %r13
+	pop %r12
+	ret
+1:	/* in child */
+	mov %r14, %rsp
+	mov %r13, %rdi
+	call *%r12
+
+	mov $_SYSCALL_EXIT, %rdi
+	xor %rsi, %rsi
+	syscall
+	hlt /* if all else fails... */
diff --git a/src/user/lib/thread.c b/src/user/lib/thread.c
deleted file mode 100644
index f7353ad..0000000
--- a/src/user/lib/thread.c
+++ /dev/null
@@ -1,11 +0,0 @@
-#include <camellia/flags.h>
-#include <camellia/syscalls.h>
-#include <stdlib.h>
-#include <user/lib/thread.h>
-
-void thread_create(int flags, void (*fn)(void*), void *arg) {
-	if (!_syscall_fork(flags | FORK_SHAREMEM | FORK_SHAREHANDLE, NULL)) {
-		void *stack = malloc(4096);
-		chstack(arg, fn, stack + 4096);
-	}
-}
diff --git a/src/user/lib/thread.h b/src/user/lib/thread.h
index 0d7376a..5a5ddc0 100644
--- a/src/user/lib/thread.h
+++ b/src/user/lib/thread.h
@@ -1,4 +1,9 @@
 #pragma once
+#include <stdlib.h>
 
-void thread_create(int flags, void (*fn)(void*), void *arg);
-_Noreturn void chstack(void *arg, void (*fn)(void*), void *esp);
+void thread_creates(int flags, void (*fn)(void*), void *arg, void *stack);
+
+static inline void thread_create(int flags, void (*fn)(void*), void *arg) {
+	/* error checking is for WIMPS. */
+	thread_creates(flags, fn, arg, malloc(4096) + 4096);
+}
-- 
cgit v1.2.3