klibc/klibc/arch/x86_64/syscall.S

   1 /*
   2  * arch/x86-64/syscall.S
   3  *
   4  * Common tail-handling code for system calls.
   5  *
   6  * The arguments are in the standard argument registers; the system
   7  * call number in %eax.
   8  */
   9         .text
  10         .align  4
  11         .globl  __syscall_common
  12         .type   __syscall_common,@function
  13 __syscall_common:
  14         movq    %rcx,%r10               # The kernel uses %r10 istf %rcx
  15         syscall
  16
  17         cmpq    $-4095,%rax
  18         jnb     1f
  19         ret
  20
  21         # Error return, must set errno
  22 1:
  23         negl    %eax
  24         movl    %eax,errno(%rip)        # errno is type int, so 32 bits
  25         orq     $-1,%rax                # orq $-1 smaller than movq $-1
  26         ret
  27
  28         .size   __syscall_common,.-__syscall_common