barebones syscall

6 files changed, 49 insertions, 0 deletions

diff --git a/src/init/linker.ld b/src/init/linker.ld
index 9f3f4b5..a59308d 100644
--- a/src/init/linker.ld
+++ b/src/init/linker.ld
@@ -6,6 +6,7 @@ SECTIONS
 	. = 2M;
 	.text BLOCK(4K) : ALIGN(4K)
 	{
+		*(.text.startup)
 		*(.text)
 	}
 	.rodata BLOCK(4K) : ALIGN(4K)
diff --git a/src/init/main.c b/src/init/main.c
index ce1600c..cb3fa1d 100644
--- a/src/init/main.c
+++ b/src/init/main.c
@@ -1,6 +1,10 @@
 #include <stdint.h>
 
+void _syscall();
+
 int main() {
+	_syscall();
+
 	// change the colors of VGA text
 	// doesn't require a lot of code, but still shows that it's working
 	uint8_t *vga = (void*) 0xB8000;
diff --git a/src/init/syscall.s b/src/init/syscall.s
new file mode 100644
index 0000000..ebd9d0e
--- /dev/null
+++ b/src/init/syscall.s
@@ -0,0 +1,9 @@
+.section .text
+.global _syscall
+.type _syscall, @function
+_syscall:
+	mov %esp, %ecx
+	mov $_syscall_ret, %edx
+	sysenter
+_syscall_ret:
+	ret
diff --git a/src/kernel/arch/generic.h b/src/kernel/arch/generic.h
index a535514..08f26a7 100644
--- a/src/kernel/arch/generic.h
+++ b/src/kernel/arch/generic.h
@@ -17,6 +17,7 @@ void halt_cpu();
 // src/arch/i386/sysenter.s
 void sysexit(void (*fun)(), void *stack_top);
 void sysenter_setup();
+void syscall_handler();
 
 // all of those can allocate memory
 struct pagedir *pagedir_new();
diff --git a/src/kernel/arch/i386/sysenter.s b/src/kernel/arch/i386/sysenter.s
index 0cfeb10..3fcd4c3 100644
--- a/src/kernel/arch/i386/sysenter.s
+++ b/src/kernel/arch/i386/sysenter.s
@@ -4,6 +4,8 @@
 .set SEG_r3data, 4
 
 .set IA32_SYSENTER_CS, 0x174
+.set IA32_SYSENTER_ESP, 0x175
+.set IA32_SYSENTER_EIP, 0x176
 
 .section .text
 .global sysexit
@@ -30,7 +32,33 @@ sysexit:
 .type sysenter_setup, @function
 sysenter_setup:
 	xor %edx, %edx
+
 	mov $(SEG_r0code << 3), %eax
 	mov $IA32_SYSENTER_CS, %ecx
 	wrmsr
+
+	mov $IA32_SYSENTER_ESP, %ecx
+	mov $_bss_end, %eax
+	wrmsr
+
+	mov $IA32_SYSENTER_EIP, %ecx
+	mov $sysenter_handler, %eax
+	wrmsr
+
 	ret
+
+sysenter_handler:
+	pushal
+
+	mov %cr0, %eax
+	and $0x7FFFFFFF, %eax  // disable paging
+	mov %eax, %cr0
+
+	call syscall_handler
+
+	mov %cr0, %eax
+	or  $0x80000000, %eax  // enable paging
+	mov %eax, %cr0
+
+	popal
+	sysexit
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
new file mode 100644
index 0000000..25b8eb5
--- /dev/null
+++ b/src/kernel/syscalls.c
@@ -0,0 +1,6 @@
+#include <kernel/arch/generic.h>
+#include <kernel/panic.h>
+
+void syscall_handler() {
+	log_const("in a syscall!");
+}