arch/ia64/kernel/efi_stub.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * EFI call stub.
   4  *
   5  * Copyright (C) 1999-2001 Hewlett-Packard Co
   6  *      David Mosberger <davidm@hpl.hp.com>
   7  *
   8  * This stub allows us to make EFI calls in physical mode with interrupts
   9  * turned off.  We need this because we can't call SetVirtualMap() until
  10  * the kernel has booted far enough to allow allocation of struct vma_struct
  11  * entries (which we would need to map stuff with memory attributes other
  12  * than uncached or writeback...).  Since the GetTime() service gets called
  13  * earlier than that, we need to be able to make physical mode EFI calls from
  14  * the kernel.
  15  */
  16
  17 /*
  18  * PSR settings as per SAL spec (Chapter 8 in the "IA-64 System
  19  * Abstraction Layer Specification", revision 2.6e).  Note that
  20  * psr.dfl and psr.dfh MUST be cleared, despite what this manual says.
  21  * Otherwise, SAL dies whenever it's trying to do an IA-32 BIOS call
  22  * (the br.ia instruction fails unless psr.dfl and psr.dfh are
  23  * cleared).  Fortunately, SAL promises not to touch the floating
  24  * point regs, so at least we don't have to save f2-f127.
  25  */
  26 #define PSR_BITS_TO_CLEAR                                               \
  27         (IA64_PSR_I | IA64_PSR_IT | IA64_PSR_DT | IA64_PSR_RT |         \
  28          IA64_PSR_DD | IA64_PSR_SS | IA64_PSR_RI | IA64_PSR_ED |        \
  29          IA64_PSR_DFL | IA64_PSR_DFH)
  30
  31 #define PSR_BITS_TO_SET                                                 \
  32         (IA64_PSR_BN)
  33
  34 #include <asm/processor.h>
  35 #include <asm/asmmacro.h>
  36
  37 /*
  38  * Inputs:
  39  *      in0 = address of function descriptor of EFI routine to call
  40  *      in1..in7 = arguments to routine
  41  *
  42  * Outputs:
  43  *      r8 = EFI_STATUS returned by called function
  44  */
  45
  46 GLOBAL_ENTRY(efi_call_phys)
  47         .prologue ASM_UNW_PRLG_RP|ASM_UNW_PRLG_PFS, ASM_UNW_PRLG_GRSAVE(8)
  48         alloc loc1=ar.pfs,8,7,7,0
  49         ld8 r2=[in0],8                  // load EFI function's entry point
  50         mov loc0=rp
  51         .body
  52         ;;
  53         mov loc2=gp                     // save global pointer
  54         mov loc4=ar.rsc                 // save RSE configuration
  55         mov ar.rsc=0                    // put RSE in enforced lazy, LE mode
  56         ;;
  57         ld8 gp=[in0]                    // load EFI function's global pointer
  58         movl r16=PSR_BITS_TO_CLEAR
  59         mov loc3=psr                    // save processor status word
  60         movl r17=PSR_BITS_TO_SET
  61         ;;
  62         or loc3=loc3,r17
  63         mov b6=r2
  64         ;;
  65         andcm r16=loc3,r16      // get psr with IT, DT, and RT bits cleared
  66         br.call.sptk.many rp=ia64_switch_mode_phys
  67 .ret0:  mov out4=in5
  68         mov out0=in1
  69         mov out1=in2
  70         mov out2=in3
  71         mov out3=in4
  72         mov out5=in6
  73         mov out6=in7
  74         mov loc5=r19
  75         mov loc6=r20
  76         br.call.sptk.many rp=b6         // call the EFI function
  77 .ret1:  mov ar.rsc=0                    // put RSE in enforced lazy, LE mode
  78         mov r16=loc3
  79         mov r19=loc5
  80         mov r20=loc6
  81         br.call.sptk.many rp=ia64_switch_mode_virt // return to virtual mode
  82 .ret2:  mov ar.rsc=loc4                 // restore RSE configuration
  83         mov ar.pfs=loc1
  84         mov rp=loc0
  85         mov gp=loc2
  86         br.ret.sptk.many rp
  87 END(efi_call_phys)