[amd64] Fix RSP0 not getting saved (threads restarting), add int $0x80

conf/make/amd64.mk

@@ -24,7 +24,8 @@ OBJS+=$(O)/arch/amd64/kernel.o \
 	  $(O)/arch/amd64/mm/heap.o \
 	  $(O)/arch/amd64/mm/vmalloc.o \
 	  $(O)/arch/amd64/sys/thread.o \
-	  $(O)/arch/amd64/ctxsw.o
+	  $(O)/arch/amd64/ctxsw.o \
+	  $(O)/arch/amd64/sys/syscall.o
 kernel_OBJS=$(O)/arch/amd64/entry.o \
 			$(OBJS)
 kernel_LINKER=$(S)/arch/amd64/link.ld

src/arch/amd64/ctxsw.c

@@ -1,23 +1,31 @@
 #include "sys/debug.h"
 #include "sys/thread.h"
 
+#define KSTACK_SIZE 32768
+
 // TODO: move to sched.c
 thread_t *amd64_thread_current = NULL;
 thread_t *amd64_thread_first = NULL;
 thread_t *amd64_thread_last = NULL;
 
 static thread_t threads[2];
-static char kstacks[2 * 16384];
+static char kstacks[2 * KSTACK_SIZE];
 
 static void kthread0(void) {
     while (1) {
+        asm volatile ("int $0x80");
         kdebug("A\n");
+        for (int i = 0; i < 10000000; ++i);
     }
 }
 
 static void kthread1(void) {
+    kdebug("Start\n");
     while (1) {
         kdebug("B\n");
+        for (int i = 0; i < 10000000; ++i);
+        kdebug("C\n");
+        for (int i = 0; i < 10000000; ++i);
     }
 }
 
@@ -37,16 +45,14 @@ void amd64_ctx_add(thread_t *t) {
 }
 
 void amd64_init_test_threads(void) {
+    amd64_thread_current = NULL;
+
     for (size_t i = 0; i < (sizeof(threads) / sizeof(threads[0])); ++i) {
         thread_info_init(&threads[i].info);
 
-        threads[i].kstack_base = (uintptr_t) &kstacks[i * 16384];
-        threads[i].kstack_size = 16384;
+        threads[i].kstack_base = (uintptr_t) &kstacks[i * KSTACK_SIZE];
+        threads[i].kstack_size = KSTACK_SIZE;
         threads[i].kstack_ptr = threads[i].kstack_base + threads[i].kstack_size - sizeof(amd64_thread_context_t);
-        kdebug("base = %p, kstacks = %p, ptr = %p\n", threads[i].kstack_base,
-                                                      kstacks,
-                                                      threads[i].kstack_ptr);
-
 
         threads[i].info.flags = THREAD_KERNEL;
 

src/arch/amd64/hw/idt.c

@@ -53,6 +53,8 @@ extern void amd64_isr_29();
 extern void amd64_isr_30();
 extern void amd64_isr_31();
 
+extern void amd64_isr_syscall();
+
 // 8259 PIC IRQs
 extern void amd64_irq_0();  // Timer
 extern void amd64_irq_1();  // TODO
@@ -138,6 +140,8 @@ void amd64_idt_init(void) {
     amd64_idt_set(30, (uintptr_t) amd64_isr_30, 0x08, IDT_FLG_P | IDT_FLG_R0 | IDT_FLG_INT32);
     amd64_idt_set(31, (uintptr_t) amd64_isr_31, 0x08, IDT_FLG_P | IDT_FLG_R0 | IDT_FLG_INT32);
 
+    amd64_idt_set(0x80, (uintptr_t) amd64_isr_syscall, 0x08, IDT_FLG_P | IDT_FLG_R0 | IDT_FLG_INT32);
+
     amd64_idt_set(IRQ_BASE + 0 , (uintptr_t) amd64_irq_0 , 0x08, IDT_FLG_P | IDT_FLG_R0 | IDT_FLG_INT32);
     amd64_idt_set(IRQ_BASE + 1 , (uintptr_t) amd64_irq_1 , 0x08, IDT_FLG_P | IDT_FLG_R0 | IDT_FLG_INT32);
     amd64_idt_set(IRQ_BASE + 2 , (uintptr_t) amd64_irq_2 , 0x08, IDT_FLG_P | IDT_FLG_R0 | IDT_FLG_INT32);

src/arch/amd64/hw/ints.S

@@ -1,6 +1,8 @@
 #include "arch/amd64/hw/int_macros.inc"
 .section .text
 .extern amd64_err_num
+// For legacy system call interface (via int $0x80)
+.global amd64_isr_syscall
 
 __isr_generic:
     cli
@@ -71,3 +73,12 @@ __isr_nerr 28
 __isr_nerr 29
 __isr_yerr 30
 __isr_nerr 31
+
+amd64_isr_syscall:
+    cli
+
+    __int_push_ctx
+    call amd64_syscall_int
+    __int_pop_ctx
+
+    iretq

src/arch/amd64/hw/irq0.S

@@ -7,6 +7,14 @@ amd64_irq_0:
 
     __int_push_ctx
 
+    // Store current RSP
+    movq %rsp, %rax
+    movq amd64_thread_current(%rip), %rdi
+    test %rdi, %rdi
+    jz 1f
+    movq %rax, (%rdi)
+1:
+
     movq amd64_timer_tick(%rip), %rax
     callq *%rax
 

src/arch/amd64/sys/syscall.c

@@ -0,0 +1,17 @@
+#include "sys/thread.h"
+#include "sys/debug.h"
+
+/**
+ * @brief Interrupt-based syscall entry
+ */
+void amd64_syscall_int(void) {
+    // TODO: write something meaningful here
+    uint64_t cnt = 1000000;
+
+    kdebug("Waiting\n");
+    while (cnt != 1) {
+        asm volatile ("sti");
+        --cnt;
+    }
+    kdebug("Waking up\n");
+}