1 files changed, 46 insertions, 12 deletions

diff --git a/lib/include/syscall.h b/lib/include/syscall.h
index 4947155..10dc545 100644
--- a/lib/include/syscall.h
+++ b/lib/include/syscall.h
@@ -19,6 +19,7 @@
 //
 //   Machine specific constraints (x86_64):
 //     a  | a register (eg rax)
+//     c  | c register (eg rcx)
 //     d  | d register (eg rdx)
 //     D  | di register (eg rdi)
 //     S  | si register (eg rsi)
@@ -35,29 +36,62 @@
 //   https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html
 //   https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html#Machine-Constraints
 //   https://gcc.gnu.org/onlinedocs/gcc/Local-Register-Variables.html
-
-// Linux syscall ABI
-//  x86-64
-//    #syscall: rax
-//    ret     : rax
-//    instr   : syscall
-//    args    : rdi   rsi   rdx   r10   r8    r9
+//
+//
+// Linux syscall ABI - x86-64
+//   #syscall: rax
+//   ret     : rax
+//   instr   : syscall
+//   args    : rdi   rsi   rdx   r10   r8    r9
 //
 // Reference:
 //   syscall(2)
+//
+//
+// X86_64 `syscall` instruction additionally clobbers following registers:
+//   rcx   Store return address.
+//   r11   Store RFLAGS.
+//
+// Reference:
+//   https://www.felixcloutier.com/x86/syscall
 
-#define argcast(A)              ((long)(A))
-#define syscall1(n, a1)         _syscall1(n, argcast(a1))
-#define syscall3(n, a1, a2, a3) _syscall3(n, argcast(a1), argcast(a2), argcast(a3))
+#define argcast(A)                          ((long)(A))
+#define syscall1(n, a1)                     _syscall1(n, argcast(a1))
+#define syscall2(n, a1, a2)                 _syscall2(n, argcast(a1), argcast(a2))
+#define syscall3(n, a1, a2, a3)             _syscall3(n, argcast(a1), argcast(a2), argcast(a3))
+#define syscall4(n, a1, a2, a3, a4)         _syscall4(n, argcast(a1), argcast(a2), argcast(a3), argcast(a4))
+#define syscall6(n, a1, a2, a3, a4, a5, a6) _syscall6(n, argcast(a1), argcast(a2), argcast(a3), argcast(a4), argcast(a5), argcast(a6))
 
 static inline long _syscall1(long n, long a1) {
     long ret;
-    asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1) : "memory");
+    asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1) : "rcx", "r11", "memory");
+    return ret;
+}
+
+static inline long _syscall2(long n, long a1, long a2) {
+    long ret;
+    asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1), "S"(a2) : "rcx", "r11", "memory");
     return ret;
 }
 
 static inline long _syscall3(long n, long a1, long a2, long a3) {
     long ret;
-    asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1), "S"(a2), "d"(a3) : "memory");
+    asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1), "S"(a2), "d"(a3) : "rcx", "r11", "memory");
+    return ret;
+}
+
+static inline long _syscall4(long n, long a1, long a2, long a3, long a4) {
+    long ret;
+    register long r10 asm("r10") = a4;
+    asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1), "S"(a2), "d"(a3), "r"(r10) : "rcx", "r11", "memory");
+    return ret;
+}
+
+static inline long _syscall6(long n, long a1, long a2, long a3, long a4, long a5, long a6) {
+    long ret;
+    register long r10 asm("r10") = a4;
+    register long r8 asm("r8") = a5;
+    register long r9 asm("r9") = a6;
+    asm volatile("syscall" : "=a"(ret) : "a"(n), "D"(a1), "S"(a2), "d"(a3), "r"(r10), "r"(r8), "r"(r9) : "rcx", "r11", "memory");
     return ret;
 }