1 /* S/390-specific implementation of profiling support.
2 Copyright (C) 2000-2018 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com)
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
23 * How profiling works on S/390:
24 * On the start of each function _mcount is called with the address of a
25 * data word in %r1 (initialized to 0, used for counting). The compiler
26 * with the option -p generates code of the form:
31 * .LC12: .long _mcount
39 * l 14,.LC12-.LT0_0(13)
40 * l 1,.LC13-.LT0_0(13)
44 * The _mcount implementation now has to call __mcount_internal with the
45 * address of .LP0 as first parameter and the return address as second
46 * parameter. &.LP0 was loaded to %r1 and the return address is in %r14.
47 * _mcount may not modify any register.
50 .globl C_SYMBOL_NAME(_mcount)
51 .type C_SYMBOL_NAME(_mcount), @function
55 /* Save the caller-clobbered registers. */
57 cfi_adjust_cfa_offset (128)
58 /* binutils 2.28+: .cfi_val_offset r15, -96 */
60 /* DW_CFA_val_offset */ 0x14, \
62 /* scaled offset */ 0x18
64 cfi_offset (r14, -128)
65 l %r2,132(%r15) # callers address = first parameter
66 la %r2,0(%r2) # clear bit 0
67 la %r3,0(%r14) # callees address = second parameter
71 .long _GLOBAL_OFFSET_TABLE_-.
73 l %r14,__mcount_internal@GOT(%r14)
76 .long __mcount_internal
82 * Pop the saved registers. Please note that `mcount' has no
87 cfi_adjust_cfa_offset (-128)
90 ASM_SIZE_DIRECTIVE(C_SYMBOL_NAME(_mcount))
93 weak_alias (_mcount, mcount)