Pass system call arguments via registers.

3769917c · Silas Boyd-Wickizer · a938d2bd · 3769917c · 3769917c · 3769917c
--- a/TODO
+++ b/TODO
@@ -4,8 +4,6 @@
  - (is there a way to use address_space(256) attributes?)
 * bring mtrace back
 * finish syscall/sysret implementation
-  - pass syscall args via argument registers
-  - (adjust argint and friends)
 * make uart console work over IPMI SOL
 * make syslinux/pxelinux work over IPMI SOL
 * the elf loader in exec.c is a bit sketchy

--- a/initcode.S
+++ b/initcode.S
@@ -6,9 +6,8 @@
 # exec(init, argv)
 .globl start
 start:
-  pushq $argv
+  movq $argv, %rsi
-  pushq $init
+  movq $init, %rdi
-  pushq $0  // where caller pc would be
  movq $SYS_exec, %rax
  int $T_SYSCALL

--- a/syscall.c
+++ b/syscall.c
@@ -53,7 +53,19 @@ fetchstr(uptr addr, char **pp)
 int
 argint64(int n, u64 *ip)
 {
-  return fetchint64(myproc()->tf->rsp + 8 + 8*n, ip);
+  switch(n) {
+  case 0: *ip = myproc()->tf->rdi; break;
+  case 1: *ip = myproc()->tf->rsi; break;
+  case 2: *ip = myproc()->tf->rdx; break;
+  case 3: *ip = myproc()->tf->rcx; break;
+  case 4: *ip = myproc()->tf->r8;  break;
+  case 5: *ip = myproc()->tf->r9;  break;
+  default:
+    cprintf("argint64: bad arg %d\n", n);
+    return -1;
+  }
+  return 0;
 }
 int
@@ -62,7 +74,7 @@ argint32(int n, int *ip)
  int r;
  u64 i;
-  r = fetchint64(myproc()->tf->rsp + 8 + 8*n, &i);
+  r = argint64(n, &i);
  if (r >= 0)
    *ip = i;
  return r;

--- a/usys.S
+++ b/usys.S
@@ -4,16 +4,8 @@
 #define SYSCALL(name) \
  .globl name; \
  name: \
-    pushq %r9; \
-    pushq %r8; \
-    pushq %rcx; \
-    pushq %rdx; \
-    pushq %rsi; \
-    pushq %rdi; \
-    pushq $0; \
    movq $SYS_ ## name, %rax; \
    int $T_SYSCALL; \
-    addq $(7 * 8), %rsp; \
    ret
 SYSCALL(fork)