arch/powerpc/kernel/optprobes_head.S

   1 /*
   2  * Code to prepare detour buffer for optprobes in Kernel.
   3  *
   4  * Copyright 2017, Anju T, IBM Corp.
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <asm/ppc_asm.h>
  13 #include <asm/ptrace.h>
  14 #include <asm/asm-offsets.h>
  15
  16 #define OPT_SLOT_SIZE   65536
  17
  18         .balign 4
  19
  20         /*
  21          * Reserve an area to allocate slots for detour buffer.
  22          * This is part of .text section (rather than vmalloc area)
  23          * as this needs to be within 32MB of the probed address.
  24          */
  25         .global optinsn_slot
  26 optinsn_slot:
  27         .space  OPT_SLOT_SIZE
  28
  29         /*
  30          * Optprobe template:
  31          * This template gets copied into one of the slots in optinsn_slot
  32          * and gets fixed up with real optprobe structures et al.
  33          */
  34         .global optprobe_template_entry
  35 optprobe_template_entry:
  36         /* Create an in-memory pt_regs */
  37         stdu    r1,-INT_FRAME_SIZE(r1)
  38         SAVE_GPR(0,r1)
  39         /* Save the previous SP into stack */
  40         addi    r0,r1,INT_FRAME_SIZE
  41         std     r0,GPR1(r1)
  42         SAVE_10GPRS(2,r1)
  43         SAVE_10GPRS(12,r1)
  44         SAVE_10GPRS(22,r1)
  45         /* Save SPRS */
  46         mfmsr   r5
  47         std     r5,_MSR(r1)
  48         li      r5,0x700
  49         std     r5,_TRAP(r1)
  50         li      r5,0
  51         std     r5,ORIG_GPR3(r1)
  52         std     r5,RESULT(r1)
  53         mfctr   r5
  54         std     r5,_CTR(r1)
  55         mflr    r5
  56         std     r5,_LINK(r1)
  57         mfspr   r5,SPRN_XER
  58         std     r5,_XER(r1)
  59         mfcr    r5
  60         std     r5,_CCR(r1)
  61         lbz     r5,PACASOFTIRQEN(r13)
  62         std     r5,SOFTE(r1)
  63         mfdar   r5
  64         std     r5,_DAR(r1)
  65         mfdsisr r5
  66         std     r5,_DSISR(r1)
  67
  68         /*
  69          * We may get here from a module, so load the kernel TOC in r2.
  70          * The original TOC gets restored when pt_regs is restored
  71          * further below.
  72          */
  73         ld      r2,PACATOC(r13)
  74
  75         .global optprobe_template_op_address
  76 optprobe_template_op_address:
  77         /*
  78          * Parameters to optimized_callback():
  79          * 1. optimized_kprobe structure in r3
  80          */
  81         nop
  82         nop
  83         nop
  84         nop
  85         nop
  86         /* 2. pt_regs pointer in r4 */
  87         addi    r4,r1,STACK_FRAME_OVERHEAD
  88
  89         .global optprobe_template_call_handler
  90 optprobe_template_call_handler:
  91         /* Branch to optimized_callback() */
  92         nop
  93
  94         /*
  95          * Parameters for instruction emulation:
  96          * 1. Pass SP in register r3.
  97          */
  98         addi    r3,r1,STACK_FRAME_OVERHEAD
  99
 100         .global optprobe_template_insn
 101 optprobe_template_insn:
 102         /* 2, Pass instruction to be emulated in r4 */
 103         nop
 104         nop
 105
 106         .global optprobe_template_call_emulate
 107 optprobe_template_call_emulate:
 108         /* Branch to emulate_step()  */
 109         nop
 110
 111         /*
 112          * All done.
 113          * Now, restore the registers...
 114          */
 115         ld      r5,_MSR(r1)
 116         mtmsr   r5
 117         ld      r5,_CTR(r1)
 118         mtctr   r5
 119         ld      r5,_LINK(r1)
 120         mtlr    r5
 121         ld      r5,_XER(r1)
 122         mtxer   r5
 123         ld      r5,_CCR(r1)
 124         mtcr    r5
 125         ld      r5,_DAR(r1)
 126         mtdar   r5
 127         ld      r5,_DSISR(r1)
 128         mtdsisr r5
 129         REST_GPR(0,r1)
 130         REST_10GPRS(2,r1)
 131         REST_10GPRS(12,r1)
 132         REST_10GPRS(22,r1)
 133         /* Restore the previous SP */
 134         addi    r1,r1,INT_FRAME_SIZE
 135
 136         .global optprobe_template_ret
 137 optprobe_template_ret:
 138         /* ... and jump back from trampoline */
 139         nop
 140
 141         .global optprobe_template_end
 142 optprobe_template_end: