sysdeps/s390/s390-64/s390x-mcount.h

   1 /* 64 bit S/390-specific implementation of profiling support.
   2    Copyright (C) 2001-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <sysdep.h>
  20
  21 /* How profiling works on 64 bit S/390:
  22    On the start of each function _mcount is called with the address of a
  23    data word in %r1 (initialized to 0, used for counting). The compiler
  24    with the option -p generates code of the form:
  25
  26            STM    6,15,24(15)
  27            BRAS   13,.LTN0_0
  28    .LT0_0:
  29    .LC13:  .long  .LP0
  30            .data
  31            .align 4
  32    .LP0:   .long  0
  33            .text
  34    # function profiler
  35            stg    14,8(15)
  36            lg     1,.LC13-.LT0_0(13)
  37            brasl  14,_mcount
  38            lg     14,8(15)
  39
  40    The _mcount implementation now has to call __mcount_internal with the
  41    address of .LP0 as first parameter and the return address as second
  42    parameter. &.LP0 was loaded to %r1 and the return address is in %r14.
  43    _mcount may not modify any register.
  44
  45    Alternatively, at the start of each function __fentry__ is called using a
  46    single
  47
  48    # function profiler
  49            brasl  0,__fentry__
  50
  51    instruction.  In this case %r0 points to the callee, and %r14 points to the
  52    caller.  These values need to be passed to __mcount_internal using the same
  53    sequence as for _mcount, so the code below is shared between both functions.
  54    The only major difference is that __fentry__ cannot return through %r0, in
  55    which the return address is located, because br instruction is a no-op with
  56    this register.  Therefore %r1, which is clobbered by the PLT anyway, is
  57    used.  */
  58
  59 #define xglue(x, y) x ## y
  60 #define glue(x, y) xglue(x, y)
  61
  62         .globl C_SYMBOL_NAME(MCOUNT_SYMBOL)
  63         .type C_SYMBOL_NAME(MCOUNT_SYMBOL), @function
  64         cfi_startproc
  65         .align ALIGNARG(4)
  66 C_LABEL(MCOUNT_SYMBOL)
  67         cfi_return_column (glue(r, MCOUNT_CALLEE_REG))
  68         /* Save the caller-clobbered registers.  */
  69         aghi  %r15,-224
  70         cfi_adjust_cfa_offset (224)
  71         /* binutils 2.28+: .cfi_val_offset r15, -160 */
  72         .cfi_escape \
  73                 /* DW_CFA_val_offset */ 0x14, \
  74                 /* r15 */               0x0f, \
  75                 /* scaled offset */     0x14
  76         stmg  %r14,%r5,160(%r15)
  77         cfi_offset (r14, -224)
  78         cfi_offset (r0, -224+16)
  79         lg    %r2,MCOUNT_CALLER_OFF(%r15)       # callers address  = 1st param
  80         lgr   %r3,glue(%r, MCOUNT_CALLEE_REG)   # callees address  = 2nd param
  81
  82 #ifdef PIC
  83         brasl %r14,__mcount_internal@PLT
  84 #else
  85         brasl %r14,__mcount_internal
  86 #endif
  87
  88         /* Pop the saved registers.  Please note that `mcount' has no
  89            return value.  */
  90         lmg   %r14,%r5,160(%r15)
  91         aghi  %r15,224
  92         cfi_adjust_cfa_offset (-224)
  93 #if MCOUNT_RETURN_REG != MCOUNT_CALLEE_REG
  94         lgr   glue(%r, MCOUNT_RETURN_REG),glue(%r, MCOUNT_CALLEE_REG)
  95 #endif
  96         br    glue(%r, MCOUNT_RETURN_REG)
  97         cfi_endproc
  98         ASM_SIZE_DIRECTIVE(C_SYMBOL_NAME(MCOUNT_SYMBOL))