kernel syscall handler

3 files changed, 134 insertions, 3 deletions

diff --git a/kernel/cpu/idt.S b/kernel/cpu/idt.S
index 0ba35f8..177d3b1 100644
--- a/kernel/cpu/idt.S
+++ b/kernel/cpu/idt.S
@@ -1,10 +1,13 @@
 	.global isr_stub_table
+	.global isr_restore
+	.global awd
 
 	.extern idt_exception_handler
 	.extern idt_pic_timer
 	.extern idt_pic_keyboard
 	.extern idt_pic_mouse
 	.extern idt_pic_eoi
+	.extern syscall_handler
 
 .macro PUSHALL
 	pushq	%rax
@@ -78,6 +81,16 @@ isr_stub_\num:
 	iretq
 .endm
 
+.macro SYSCALL num
+	.align 8
+isr_stub_\num:
+	PUSHALL
+	cld
+	movq	%rsp, %rdi				# top of stack
+	callq	syscall_handler
+	jmp		isr_restore
+.endm
+
 .macro PICGeneric num
 	.align 8
 isr_stub_\num:
@@ -402,10 +415,21 @@ isr_stub_table:
 	.quad isr_stub_254
 	.quad isr_stub_255
 
-# isr stubs
 	.section .text
 	.code64
 
+# isr restore
+isr_restore:
+	movw $(0x20 | 3), %ax
+	movw %ax, %ds
+	movw %ax, %es
+	movw %ax, %fs
+	movw %ax, %gs
+
+	POPALL
+	iretq
+
+# isr stubs
 ISRException 0
 ISRException 1
 ISRException 2
@@ -536,7 +560,7 @@ ISRIgnore 124
 ISRIgnore 125
 ISRIgnore 126
 ISRIgnore 127
-ISRIgnore 128
+SYSCALL 128
 ISRIgnore 129
 ISRIgnore 130
 ISRIgnore 131
diff --git a/kernel/include/comus/syscalls.h b/kernel/include/comus/syscalls.h
index 3dc128d..3b9ea70 100644
--- a/kernel/include/comus/syscalls.h
+++ b/kernel/include/comus/syscalls.h
@@ -29,7 +29,7 @@
 #define SYS_sbrk 16
 
 // UPDATE THIS DEFINITION IF MORE SYSCALLS ARE ADDED!
-#define N_SYSCALLS 13
+#define N_SYSCALLS 17
 
 // interrupt vector entry for system calls
 #define VEC_SYSCALL 0x80
diff --git a/kernel/syscall.c b/kernel/syscall.c
new file mode 100644
index 0000000..7887e83
--- /dev/null
+++ b/kernel/syscall.c
@@ -0,0 +1,107 @@
+#include <comus/cpu.h>
+#include <comus/syscalls.h>
+#include <comus/drivers/uart.h>
+#include <comus/memory.h>
+#include <comus/procs.h>
+
+#define ARG1(type, name) type name = (type)(current_pcb->regs->rdi)
+#define ARG2(type, name) type name = (type)(current_pcb->regs->rsi)
+#define ARG3(type, name) type name = (type)(current_pcb->regs->rdx)
+#define ARG4(type, name) type name = (type)(current_pcb->regs->rcx)
+
+static int sys_exit(void)
+{
+	ARG1(int, status);
+	(void) status;
+
+	// FIXME: schedule somthing else
+	while (1)
+		;
+
+	return 1;
+}
+
+static int sys_write(void)
+{
+	ARG1(int, fd);
+	ARG2(const void *, buffer);
+	ARG3(size_t, nbytes);
+
+	const char *map_buf = kmapuseraddr(current_pcb->memctx, buffer, nbytes);
+	if (map_buf == NULL)
+		return 0;
+
+	// cannot write to stdin
+	if (fd == 0)
+		nbytes = 0;
+
+	// write to stdout
+	else if (fd == 1) {
+		for (size_t i = 0; i < nbytes; i++)
+			kputc(map_buf[i]);
+	}
+
+	// files
+	else {
+		// TODO: write to files
+		nbytes = 0;
+	}
+
+	kunmapaddr(map_buf);
+
+	return nbytes;
+}
+
+static int (*syscall_tbl[N_SYSCALLS])(void) = {
+	[SYS_exit] = sys_exit,
+	[SYS_waitpid] = NULL,
+	[SYS_fork] = NULL,
+	[SYS_exec] = NULL,
+	[SYS_open] = NULL,
+	[SYS_close] = NULL,
+	[SYS_read] = NULL,
+	[SYS_write] = sys_write,
+	[SYS_getpid] = NULL,
+	[SYS_getppid] = NULL,
+	[SYS_gettime] = NULL,
+	[SYS_getprio] = NULL,
+	[SYS_setprio] = NULL,
+	[SYS_kill] = NULL,
+	[SYS_sleep] = NULL,
+	[SYS_brk] = NULL,
+	[SYS_sbrk] = NULL,
+};
+
+void syscall_handler(struct cpu_regs *regs)
+{
+	uint64_t num;
+	int (*handler)(void);
+	int ret = 1;
+
+	// make sure were in the kernel memory context
+	mem_ctx_switch(kernel_mem_ctx);
+
+	// update data
+	current_pcb->regs = regs;
+	num = current_pcb->regs->rax;
+
+	// syscall number
+
+	// check for invalid syscall
+	if (num >= N_SYSCALLS) {
+		// invalid syscall
+		// FIXME: kill user process
+		while(1);
+	}
+
+	// run syscall handler (if exists)
+	handler = syscall_tbl[num];
+	if (handler != NULL)
+		handler();
+
+	// save return value
+	current_pcb->regs->rax = ret;
+
+	// switch back to process ctx
+	mem_ctx_switch(current_pcb->memctx);
+}