Implemented basic syscalls and user mode

Doesn't completely work right now

2 files changed, 89 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);
+}
diff --git a/src/kernel/syscall/syscall.h b/src/kernel/syscall/syscall.h
new file mode 100644
index 0000000..d35c4e6
--- /dev/null
+++ b/src/kernel/syscall/syscall.h
@@ -0,0 +1,44 @@
+#ifndef MELVIX_SYSCALL_H
+#define MELVIX_SYSCALL_H
+
+#include <kernel/interrupts/interrupts.h>
+
+void syscalls_install();
+
+void syscall_handler(struct regs *r);
+
+#define DECL_SYSCALL0(fn) int syscall_##fn();
+#define DECL_SYSCALL1(fn, p1) int syscall_##fn(p1);
+#define DECL_SYSCALL2(fn, p1, p2) int syscall_##fn(p1,p2);
+#define DECL_SYSCALL3(fn, p1, p2, p3) int syscall_##fn(p1,p2,p3);
+#define DECL_SYSCALL4(fn, p1, p2, p3, p4) int syscall_##fn(p1,p2,p3,p4);
+#define DECL_SYSCALL5(fn, p1, p2, p3, p4, p5) int syscall_##fn(p1,p2,p3,p4,p5);
+
+#define DEFN_SYSCALL0(fn, num) \
+int syscall_##fn() { \
+ int a; \
+ asm volatile("int $0x80" : "=a" (a) : "0" (num)); \
+ return a; \
+}
+
+#define DEFN_SYSCALL1(fn, num, P1) \
+int syscall_##fn(P1 p1) { \
+ int a; \
+ asm volatile("int $0x80" : "=a" (a) : "0" (num), "b" ((int)p1)); \
+ return a; \
+}
+
+#define DEFN_SYSCALL2(fn, num, P1, P2) \
+int syscall_##fn(P1 p1, P2 p2) { \
+ int a; \
+ asm volatile("int $0x80" : "=a" (a) : "0" (num), "b" ((int)p1), "c" ((int)p2)); \
+ return a; \
+}
+
+DECL_SYSCALL1(vesa_draw_string, const char *)
+
+DECL_SYSCALL1(vesa_draw_number, int)
+
+DECL_SYSCALL1(serial_write, const char *)
+
+#endif