Implemented basic syscalls and user mode

Doesn't completely work right now

1 files changed, 45 insertions, 0 deletions

diff --git a/src/kernel/syscall/syscall.c b/src/kernel/syscall/syscall.c
new file mode 100644
index 0000000..d1dbd6b
--- /dev/null
+++ b/src/kernel/syscall/syscall.c
@@ -0,0 +1,45 @@
+#include <stdint.h>
+#include <kernel/syscall/syscall.h>
+#include <kernel/interrupts/interrupts.h>
+#include <kernel/graphics/vesa.h>
+#include <kernel/io/io.h>
+
+DEFN_SYSCALL1(vesa_draw_string, 0, const char *);
+
+DEFN_SYSCALL1(vesa_draw_number, 1, int);
+
+DEFN_SYSCALL1(serial_write, 2, const char *);
+
+static void *syscalls[3] = {
+        &vesa_draw_string,
+        &vesa_draw_number,
+        &serial_write,
+};
+uint32_t num_syscalls = 3;
+
+void syscall_handler(struct regs *r) {
+    if (r->eax >= num_syscalls)
+        return;
+
+    void *location = syscalls[r->eax];
+
+    int ret;
+    asm volatile (" \
+     push %1; \
+     push %2; \
+     push %3; \
+     push %4; \
+     push %5; \
+     call *%6; \
+     pop %%ebx; \
+     pop %%ebx; \
+     pop %%ebx; \
+     pop %%ebx; \
+     pop %%ebx; \
+   " : "=a" (ret) : "r" (r->edi), "r" (r->esi), "r" (r->edx), "r" (r->ecx), "r" (r->ebx), "r" (location));
+    r->eax = ret;
+}
+
+void syscalls_install() {
+    irq_install_handler(0x80, &syscall_handler);
+}