arch/arm64/kvm/hyp.S

   1 /*
   2  * Copyright (C) 2012,2013 - ARM Ltd
   3  * Author: Marc Zyngier <marc.zyngier@arm.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #include <linux/linkage.h>
  19
  20 #include <asm/alternative.h>
  21 #include <asm/assembler.h>
  22 #include <asm/cpufeature.h>
  23
  24 /*
  25  * u64 __kvm_call_hyp(void *hypfn, ...);
  26  *
  27  * This is not really a variadic function in the classic C-way and care must
  28  * be taken when calling this to ensure parameters are passed in registers
  29  * only, since the stack will change between the caller and the callee.
  30  *
  31  * Call the function with the first argument containing a pointer to the
  32  * function you wish to call in Hyp mode, and subsequent arguments will be
  33  * passed as x0, x1, and x2 (a maximum of 3 arguments in addition to the
  34  * function pointer can be passed).  The function being called must be mapped
  35  * in Hyp mode (see init_hyp_mode in arch/arm/kvm/arm.c).  Return values are
  36  * passed in x0.
  37  *
  38  * A function pointer with a value less than 0xfff has a special meaning,
  39  * and is used to implement hyp stubs in the same way as in
  40  * arch/arm64/kernel/hyp_stub.S.
  41  */
  42 ENTRY(__kvm_call_hyp)
  43         hvc     #0
  44         ret
  45 ENDPROC(__kvm_call_hyp)