mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-29 16:21:07 +00:00
71c01af52f
* Since __fentry__ is almost the same as _mcount, reuse the code by #including it twice with different #defines around. * Remove LA usages - they are needed in 31-bit mode to clear the top bit, but in 64-bit they appear to do nothing. * Add CFI rule for the nonstandard return register. This rule applies to the current function (binutils generates a new CIE - see gas/dw2gencfi.c:select_cie_for_fde()), so it is not necessary to put __fentry__ into a new file. * Fix CFI offset for %r14. * Add CFI rule for %r0. * Fix unwound value of %r15 being off by 244 bytes. * Unwinding in __fentry__@plt does not work, no plan to fix it - it would require asking linker to generate CFI for return address in %r0. From functional perspective keeping it broken is fine, since the callee did not have a chance to do anything yet. From convenience perspective it would be possible to enhance GDB in the future to treat __fentry__@plt in a special way. * Fix whitespace. * Fix offsets in comments, which were copied from 32-bit code. * 32-bit version will not be implemented, since it's not compatible with the corresponding PLT stubs: they assume %r12 points to GOT, which is not the case for gcc-emitted __fentry__ stub, which runs before the prolog. This patch adds the runtime support in glibc for the -mfentry gcc feature introduced in [1] and [2]. [1] https://gcc.gnu.org/ml/gcc-patches/2018-07/msg00784.html [2] https://gcc.gnu.org/ml/gcc-patches/2018-07/msg00912.html ChangeLog: * sysdeps/s390/s390-64/Versions (__fentry__): Add. * sysdeps/s390/s390-64/s390x-mcount.S: Move the common code to s390x-mcount.h and #include it. * sysdeps/s390/s390-64/s390x-mcount.h: New file. * sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist (__fentry__): Add.
100 lines
3.5 KiB
C
100 lines
3.5 KiB
C
/* 64 bit S/390-specific implementation of profiling support.
|
|
Copyright (C) 2001-2018 Free Software Foundation, Inc.
|
|
Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com)
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include <sysdep.h>
|
|
|
|
/* How profiling works on 64 bit S/390:
|
|
On the start of each function _mcount is called with the address of a
|
|
data word in %r1 (initialized to 0, used for counting). The compiler
|
|
with the option -p generates code of the form:
|
|
|
|
STM 6,15,24(15)
|
|
BRAS 13,.LTN0_0
|
|
.LT0_0:
|
|
.LC13: .long .LP0
|
|
.data
|
|
.align 4
|
|
.LP0: .long 0
|
|
.text
|
|
# function profiler
|
|
stg 14,8(15)
|
|
lg 1,.LC13-.LT0_0(13)
|
|
brasl 14,_mcount
|
|
lg 14,8(15)
|
|
|
|
The _mcount implementation now has to call __mcount_internal with the
|
|
address of .LP0 as first parameter and the return address as second
|
|
parameter. &.LP0 was loaded to %r1 and the return address is in %r14.
|
|
_mcount may not modify any register.
|
|
|
|
Alternatively, at the start of each function __fentry__ is called using a
|
|
single
|
|
|
|
# function profiler
|
|
brasl 0,__fentry__
|
|
|
|
instruction. In this case %r0 points to the callee, and %r14 points to the
|
|
caller. These values need to be passed to __mcount_internal using the same
|
|
sequence as for _mcount, so the code below is shared between both functions.
|
|
The only major difference is that __fentry__ cannot return through %r0, in
|
|
which the return address is located, because br instruction is a no-op with
|
|
this register. Therefore %r1, which is clobbered by the PLT anyway, is
|
|
used. */
|
|
|
|
#define xglue(x, y) x ## y
|
|
#define glue(x, y) xglue(x, y)
|
|
|
|
.globl C_SYMBOL_NAME(MCOUNT_SYMBOL)
|
|
.type C_SYMBOL_NAME(MCOUNT_SYMBOL), @function
|
|
cfi_startproc
|
|
.align ALIGNARG(4)
|
|
C_LABEL(MCOUNT_SYMBOL)
|
|
cfi_return_column (glue(r, MCOUNT_CALLEE_REG))
|
|
/* Save the caller-clobbered registers. */
|
|
aghi %r15,-224
|
|
cfi_adjust_cfa_offset (224)
|
|
/* binutils 2.28+: .cfi_val_offset r15, -160 */
|
|
.cfi_escape \
|
|
/* DW_CFA_val_offset */ 0x14, \
|
|
/* r15 */ 0x0f, \
|
|
/* scaled offset */ 0x14
|
|
stmg %r14,%r5,160(%r15)
|
|
cfi_offset (r14, -224)
|
|
cfi_offset (r0, -224+16)
|
|
lg %r2,MCOUNT_CALLER_OFF(%r15) # callers address = 1st param
|
|
lgr %r3,glue(%r, MCOUNT_CALLEE_REG) # callees address = 2nd param
|
|
|
|
#ifdef PIC
|
|
brasl %r14,__mcount_internal@PLT
|
|
#else
|
|
brasl %r14,__mcount_internal
|
|
#endif
|
|
|
|
/* Pop the saved registers. Please note that `mcount' has no
|
|
return value. */
|
|
lmg %r14,%r5,160(%r15)
|
|
aghi %r15,224
|
|
cfi_adjust_cfa_offset (-224)
|
|
#if MCOUNT_RETURN_REG != MCOUNT_CALLEE_REG
|
|
lgr glue(%r, MCOUNT_RETURN_REG),glue(%r, MCOUNT_CALLEE_REG)
|
|
#endif
|
|
br glue(%r, MCOUNT_RETURN_REG)
|
|
cfi_endproc
|
|
ASM_SIZE_DIRECTIVE(C_SYMBOL_NAME(MCOUNT_SYMBOL))
|