[USER] System calls

init/init.c

@@ -1,8 +1,10 @@
+#include <stdio.h>
+#include <unistd.h>
 int main(int argc, char **argv)
 {
   (void) argc;
   (void) argv;
-  int i=0;
-  for(;;)i++;
+  asm("syscall" :: "a" (0x3FF), "D" ("Hello, world!\n"));
+  for(;;);
   return 0;
 }

kernel/boot/kmain.c

@@ -9,6 +9,8 @@
 #include <string.h>
 #include <cpu.h>
 #include <elf.h>
+#include <syscall.h>
+#include <cpuid.h>
 
 int kmain(uint64_t multiboot_magic, void *multiboot_data)
 {
@@ -24,6 +26,8 @@ int kmain(uint64_t multiboot_magic, void *multiboot_data)
   cpu_init();
   pit_init();
 
+  debug_info("Syscall enabled:%d\n", CPUID_FEATURE_SYSCALL);
+
   process_t *p1 = process_spawn(0);
   thread_t *th = exec_elf(p1, mboot_data.init);
   scheduler_insert(th);

kernel/cpu/cpu.c

@@ -7,6 +7,7 @@
 #include <mem.h>
 #include <gdt.h>
 #include <string.h>
+#include <syscall.h>
 
 cpu_t cpus[MAX_NUMCPU];
 unsigned int num_cpu = 0;
@@ -38,6 +39,7 @@ void init_cpu()
   gdt_init();
   sse_init();
   scheduler_init();
+  syscall_init();
 }
 
 void cpu_init()

kernel/include/cpu.h

@@ -14,6 +14,7 @@
 #define GS_OFFSET_CPU 0
 #define GS_OFFSET_STATE 40
 #define GS_OFFSET_STACK 48
+#define GS_OFFSET_SCTEMP 56
 
 #ifndef __ASSEMBLER__
 #include <stdint.h>
@@ -31,6 +32,7 @@ typedef struct cpu_t
   uint64_t is_bsp;
   uint64_t current_state; // 40
   void *kernel_stack; // 48
+  uint64_t syscall_temp; // 56
   thread_t *current_thread;
   thread_t *last_thread;
   process_t *current_process;

kernel/include/int.h

@@ -66,6 +66,7 @@
 #define   INT_APIC_ERROR     0x45
 #define   INT_APIC_SPUR      0xFF
 
+#define INT_SYSCALL 0x80
 
 #define RFLAGS_IOPL (3<<12)
 #define RFLAGS_IOPL1 (1<<12)

kernel/include/syscall.h

@@ -0,0 +1,41 @@
+#pragma once
+
+void syscall_init();
+
+typedef long (*syscall_handler_t)(long num, long, long, long, long, long, long);
+
+#define SYSCALL_DECL(name) \
+  long syscall_##name(long, long, long, long, long, long, long)
+
+#define SYSCALL_DEF(name) \
+  long syscall_##name(long num, long _a1, long _a2, long _a3, long _a4, long _a5, long _a6)
+
+#define _SYSCALL_INIT6(t1,n1,t2,n2,t3,n3,t4,n4,t5,n5,t6,n6) \
+  (void)num; \
+  t1 n1 = (t1)_a1; \
+  (void)n1; \
+  t2 n2 = (t2)_a2; \
+  (void)n2; \
+  t3 n3 = (t3)_a3; \
+  (void)n3; \
+  t4 n4 = (t4)_a4; \
+  (void)n4; \
+  t5 n5 = (t5)_a5; \
+  (void)n5; \
+  t6 n6 = (t6)_a6; \
+  (void)n6;
+#define _SYSCALL_INIT5(t1,n1,t2,n2,t3,n3,t4,n4,t5,n5) _SYSCALL_INIT6(t1,n1,t2,n2,t3,n3,t4,n4,t5,n5,long,__a6)
+#define _SYSCALL_INIT4(t1,n1,t2,n2,t3,n3,t4,n4) _SYSCALL_INIT6(t1,n1,t2,n2,t3,n3,t4,n4,long,__a5,long,__a6)
+#define _SYSCALL_INIT3(t1,n1,t2,n2,t3,n3) _SYSCALL_INIT6(t1,n1,t2,n2,t3,n3,long,__a4,long,__a5,long,__a6)
+#define _SYSCALL_INIT2(t1,n1,t2,n2) _SYSCALL_INIT6(t1,n1,t2,n2,long,__a3,long,__a4,long,__a5,long,__a6)
+#define _SYSCALL_INIT1(t1,n1) _SYSCALL_INIT6(t1,n1,long,__a2,long,__a3,long,__a4,long,__a5,long,__a6)
+#define _SYSCALL_INIT0() _SYSCALL_INIT6(long,__a1,long,__a2,long,__a3,long,__a4,long,__a5,long,__a6)
+
+#define __SYSCALL_NARGS(a0,b0,a1,b1,a2,b2,a3,b3,a4,b4,a5,b5,a6,n,...) n
+#define _SYSCALL_NARGS(...) __SYSCALL_NARGS(__VA_ARGS__,6,6,5,5,4,4,3,3,2,2,1,1,0,0)
+#define __SYSCALL_CONCAT(a,b) a##b
+#define _SYSCALL_CONCAT(a,b) __SYSCALL_CONCAT(a,b)
+#define _SYSCALL_INIT(a,...) _SYSCALL_CONCAT(a, _SYSCALL_NARGS(__VA_ARGS__))(__VA_ARGS__)
+#define SYSCALL_INIT(...) _SYSCALL_INIT(_SYSCALL_INIT,__VA_ARGS__)
+
+#define SYSCALL_REGISTER(name, num) syscall_handlers[num] = syscall_##name

kernel/interrupts/isr_common.S

@@ -64,6 +64,15 @@ isr_return:
   pop r13
   pop r14
   pop r15
+
+  // Jump to syscall_return if we're in a syscall
+  push rax
+  mov rax, [rsp + 8]
+  cmp rax, INT_SYSCALL
+  .extern syscall_return
+  jz syscall_return
+  pop rax
+
   // Pop error code and fault number
   add rsp, 16
   iretq

kernel/syscall/syscall.c

@@ -0,0 +1,65 @@
+#include <syscall.h>
+#include <debug.h>
+#include <int.h>
+#include <msr.h>
+#include <gdt.h>
+#include <registers.h>
+
+extern void syscall_entry();
+
+syscall_handler_t syscall_handlers[1024];
+
+SYSCALL_DECL(debug);
+
+registers_t *syscall_handler(registers_t *r)
+{
+  // Syscall number: RAX
+  // Order of arguments:
+  // RDI
+  // RSI
+  // RDX
+  // R10
+  // R8
+  // R9
+  // stack
+  //
+  // Return value:
+  // RAX
+
+  if(syscall_handlers[r->rax])
+  {
+    r->rax = syscall_handlers[r->rax](r->rax, r->rdi, r->rsi, r->rdx, r->r10, r->r8, r->r9);
+    return r;
+  }
+
+  debug_error("Unknown syscall, No:%d\n", r->rax);
+  debug("syscall_%d(%x, %x, %x, %x, %x, %x)\n", r->rax, r->rdi, r->rsi, r->rdx, r->r10, r->r8, r->r9);
+  for(;;);
+}
+
+int syscall_installed = 0;
+
+void syscall_init()
+{
+  msr_write(MSR_REG_STAR, (((uint64_t)SEG_KDATA | 0x3)<<48 | ((uint64_t)SEG_KCODE)<<32));
+  msr_write(MSR_REG_LSTAR, (uint64_t)syscall_entry);
+  msr_write(MSR_REG_EFER, msr_read(MSR_REG_EFER)| 1);
+  msr_write(MSR_REG_FMASK, RFLAGS_IF);
+
+  if(!syscall_installed)
+  {
+    register_int_handler(INT_SYSCALL, syscall_handler);
+    syscall_installed = 1;
+    memset(syscall_handlers, 0, 1024*sizeof(syscall_handler_t));
+
+    SYSCALL_REGISTER(debug, 0x3FF);
+  }
+
+}
+
+SYSCALL_DEF(debug)
+{
+  SYSCALL_INIT(char*, message);
+  debug_puts(message);
+  return 0;
+}

kernel/syscall/syscall_entry.S

@@ -0,0 +1,38 @@
+#include <mem.h>
+#include <gdt.h>
+#include <int.h>
+#include <cpu.h>
+.intel_syntax noprefix
+
+
+.global syscall_entry
+.global syscall_return
+.extern syscall_handler
+
+syscall_entry:
+
+  swapgs
+  mov [gs:GS_OFFSET_SCTEMP], rsp
+  mov rsp, [gs:GS_OFFSET_STACK]
+
+  // Prepare a fake interrupt stack
+  pushq SEG_UDATA // SS
+  push [gs:GS_OFFSET_SCTEMP] // RSP
+  push r11 // RFLAGS
+  pushq SEG_UCODE // CS
+  push rcx // RIP
+  pushq 0 // Error code
+  pushq INT_SYSCALL // Interrupt id
+  swapgs
+
+  jmp isr_common
+syscall_return:
+
+  pop rax
+  add rsp, 16
+  pop rcx
+  add rsp, 8
+  pop r11
+  pop rsp
+
+  sysretq