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Re: [PATCH] Rework -fno-omit-frame-pointer support on i386
- From: "H.J. Lu" <hjl dot tools at gmail dot com>
- To: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Date: Thu, 16 Feb 2017 11:24:55 -0800
- Subject: Re: [PATCH] Rework -fno-omit-frame-pointer support on i386
- Authentication-results: sourceware.org; auth=none
- References: <1483966550-21038-1-git-send-email-adhemerval.zanella@linaro.org>
On Mon, Jan 9, 2017 at 4:55 AM, Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
> Commit 6b1df8b27f fixed the -OS build issue on i386 (BZ#20729) by
> expliciting disabling frame pointer (-fomit-frame-pointer) on the
> faulty objects. Although it does fix the issue, it is a subpar
> workaround that adds complexity in build process (a rule for each
> object to add the required compiler option and pontentially more
> rules for objects that call {INLINE,INTERNAL}_SYSCALL) and does not
> allow the implementations to get all the possible debug/calltrack
> information possible (used mainly in debuggers and performance
> measurement tools).
>
> This patch fixes it by adding an explicit configure check to see
> if -fno-omit-frame-pointer is set and to act accordingly (set or
> not OPTIMIZE_FOR_GCC_5). The make rules is simplified and only
> one is required: to add libc-do-syscall on loader due mmap
> (which will be empty anyway for default build with
> -fomit-frame-pointer).
>
> Checked on i386-linux-gnu with GCC 6.2.1 with CFLAGS sets as
> '-Os', '-O2 -fno-omit-frame-pointer', and '-O2 -fomit-frame-pointer'.
> For '-Os' the testsuite issues described by BZ#19463 and BZ#15105
> still applied.
>
> It fixes BZ #21029, although it is marked as duplicated of #20729
> (I reopened to track this cleanup).
>
> [BZ #21029]
> * config.h.in [NO_OMIT_FRAME_POINTER]: New define.
> * sysdeps/unix/sysv/linux/i386/Makefile
> [$(subdir) = elf] (sysdep-dl-routines): Add libc-do-syscall.
> (uses-6-syscall-arguments): Remove.
> [$(subdir) = misc] (CFLAGS-epoll_pwait.o): Likewise.
> [$(subdir) = misc] (CFLAGS-epoll_pwait.os): Likewise.
> [$(subdir) = misc] (CFLAGS-mmap.o): Likewise.
> [$(subdir) = misc] (CFLAGS-mmap.os): Likewise.
> [$(subdir) = misc] (CFLAGS-mmap64.o): Likewise.
> [$(subdir) = misc] (CFLAGS-mmap64.os): Likewise.
> [$(subdir) = misc] (CFLAGS-pselect.o): Likewise.
> [$(subdir) = misc] (cflags-pselect.o): Likewise.
> [$(subdir) = misc] (cflags-pselect.os): Likewise.
> [$(subdir) = misc] (cflags-rtld-mmap.os): Likewise.
> [$(subdir) = sysvipc] (cflags-semtimedop.o): Likewise.
> [$(subdir) = sysvipc] (cflags-semtimedop.os): Likewise.
> [$(subdir) = io] (CFLAGS-posix_fadvise64.o): Likewise.
> [$(subdir) = io] (CFLAGS-posix_fadvise64.os): Likewise.
> [$(subdir) = io] (CFLAGS-posix_fallocate.o): Likewise.
> [$(subdir) = io] (CFLAGS-posix_fallocate.os): Likewise.
> [$(subdir) = io] (CFLAGS-posix_fallocate64.o): Likewise.
> [$(subdir) = io] (CFLAGS-posix_fallocate64.os): Likewise.
> [$(subdir) = io] (CFLAGS-sync_file_range.o): Likewise.
> [$(subdir) = io] (CFLAGS-sync_file_range.os): Likewise.
> [$(subdir) = io] (CFLAGS-fallocate.o): Likewise.
> [$(subdir) = io] (CFLAGS-fallocate.os): Likewise.
> [$(subdir) = io] (CFLAGS-fallocate64.o): Likewise.
> [$(subdir) = io] (CFLAGS-fallocate64.os): Likewise.
> [$(subdir) = nptl] (CFLAGS-pthread_rwlock_timedrdlock.o):
> Likewise.
> [$(subdir) = nptl] (CFLAGS-pthread_rwlock_timedrdlock.os):
> Likewise.
> [$(subdir) = nptl] (CFLAGS-pthread_rwlock_timedrwlock.o):
> Likewise.
> [$(subdir) = nptl] (CFLAGS-pthread_rwlock_timedrwlock.os):
> Likewise.
> [$(subdir) = nptl] (CFLAGS-sem_wait.o): Likewise.
> [$(subdir) = nptl] (CFLAGS-sem_wait.os): Likewise.
> [$(subdir) = nptl] (CFLAGS-sem_timedwait.o): Likewise.
> [$(subdir) = nptl] (CFLAGS-sem_timedwait.os): Likewise.
> * sysdeps/unix/sysv/linux/i386/configure.ac: Add check for
> -fno-omit-frame-pointer usage.
> * sysdeps/unix/sysv/linux/i386/configure: Regenerate.
> * sysdeps/unix/sysv/linux/i386/sysdep.h (OPTIMIZE_FOR_GCC_5):
> Set iff NO_OMIT_FRAME_POINTER is not defined.
> (check_consistency): Likewise.
> ---
> ChangeLog | 50 +++++++++++++++++++++++++++++++
> config.h.in | 3 ++
> sysdeps/unix/sysv/linux/i386/Makefile | 39 +-----------------------
> sysdeps/unix/sysv/linux/i386/configure | 31 +++++++++++++++++++
> sysdeps/unix/sysv/linux/i386/configure.ac | 19 ++++++++++++
> sysdeps/unix/sysv/linux/i386/sysdep.h | 9 +++---
> 6 files changed, 109 insertions(+), 42 deletions(-)
>
> diff --git a/config.h.in b/config.h.in
> index 7bfe923..50da4ba 100644
> --- a/config.h.in
> +++ b/config.h.in
> @@ -259,4 +259,7 @@
> /* Build glibc with tunables support. */
> #define HAVE_TUNABLES 0
>
> +/* Define if compiler flags sets -fno-omit-frame-pointer. */
> +#undef NO_OMIT_FRAME_POINTER
> +
> #endif
> diff --git a/sysdeps/unix/sysv/linux/i386/Makefile b/sysdeps/unix/sysv/linux/i386/Makefile
> index 9609752..6aac0df 100644
> --- a/sysdeps/unix/sysv/linux/i386/Makefile
> +++ b/sysdeps/unix/sysv/linux/i386/Makefile
> @@ -1,47 +1,18 @@
> # The default ABI is 32.
> default-abi := 32
>
> -# %ebp is used to pass the 6th argument to system calls, so these
> -# system calls are incompatible with a frame pointer.
> -uses-6-syscall-arguments = -fomit-frame-pointer
> -
> ifeq ($(subdir),misc)
> sysdep_routines += ioperm iopl vm86
> -CFLAGS-epoll_pwait.o += $(uses-6-syscall-arguments)
> -CFLAGS-epoll_pwait.os += $(uses-6-syscall-arguments)
> -CFLAGS-mmap.o += $(uses-6-syscall-arguments)
> -CFLAGS-mmap.os += $(uses-6-syscall-arguments)
> -CFLAGS-mmap64.o += $(uses-6-syscall-arguments)
> -CFLAGS-mmap64.os += $(uses-6-syscall-arguments)
> -CFLAGS-pselect.o += $(uses-6-syscall-arguments)
> -CFLAGS-pselect.os += $(uses-6-syscall-arguments)
> -CFLAGS-rtld-mmap.os += $(uses-6-syscall-arguments)
> -endif
> -
> -ifeq ($(subdir),sysvipc)
> -CFLAGS-semtimedop.o += $(uses-6-syscall-arguments)
> -CFLAGS-semtimedop.os += $(uses-6-syscall-arguments)
> endif
>
> ifeq ($(subdir),elf)
> +sysdep-dl-routines += libc-do-syscall
> sysdep-others += lddlibc4
> install-bin += lddlibc4
> endif
>
> ifeq ($(subdir),io)
> sysdep_routines += libc-do-syscall
> -CFLAGS-posix_fadvise64.o += $(uses-6-syscall-arguments)
> -CFLAGS-posix_fadvise64.os += $(uses-6-syscall-arguments)
> -CFLAGS-posix_fallocate.o += $(uses-6-syscall-arguments)
> -CFLAGS-posix_fallocate.os += $(uses-6-syscall-arguments)
> -CFLAGS-posix_fallocate64.o += $(uses-6-syscall-arguments)
> -CFLAGS-posix_fallocate64.os += $(uses-6-syscall-arguments)
> -CFLAGS-sync_file_range.o += $(uses-6-syscall-arguments)
> -CFLAGS-sync_file_range.os += $(uses-6-syscall-arguments)
> -CFLAGS-fallocate.o += $(uses-6-syscall-arguments)
> -CFLAGS-fallocate.os += $(uses-6-syscall-arguments)
> -CFLAGS-fallocate64.o += $(uses-6-syscall-arguments)
> -CFLAGS-fallocate64.os += $(uses-6-syscall-arguments)
> endif
>
> ifeq ($(subdir),nptl)
> @@ -61,14 +32,6 @@ ifeq ($(subdir),nptl)
> # pull in __syscall_error routine
> libpthread-routines += sysdep
> libpthread-shared-only-routines += sysdep
> -CFLAGS-pthread_rwlock_timedrdlock.o += $(uses-6-syscall-arguments)
> -CFLAGS-pthread_rwlock_timedrdlock.os += $(uses-6-syscall-arguments)
> -CFLAGS-pthread_rwlock_timedwrlock.o += $(uses-6-syscall-arguments)
> -CFLAGS-pthread_rwlock_timedwrlock.os += $(uses-6-syscall-arguments)
> -CFLAGS-sem_wait.o += $(uses-6-syscall-arguments)
> -CFLAGS-sem_wait.os += $(uses-6-syscall-arguments)
> -CFLAGS-sem_timedwait.o += $(uses-6-syscall-arguments)
> -CFLAGS-sem_timedwait.os += $(uses-6-syscall-arguments)
> endif
>
> ifeq ($(subdir),rt)
> diff --git a/sysdeps/unix/sysv/linux/i386/configure b/sysdeps/unix/sysv/linux/i386/configure
> index eb72659..a1381e6 100644
> --- a/sysdeps/unix/sysv/linux/i386/configure
> +++ b/sysdeps/unix/sysv/linux/i386/configure
> @@ -3,5 +3,36 @@
>
> arch_minimum_kernel=2.6.32
>
> +# Check if CFLAGS sets -fno-omit-frame-pointer
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for if compiler flags sets -fno-omit-frame-pointer" >&5
> +$as_echo_n "checking for if compiler flags sets -fno-omit-frame-pointer... " >&6; }
> +if ${libc_cv_no_omit_frame_pointer+:} false; then :
> + $as_echo_n "(cached) " >&6
> +else
> + cat > conftest.c << EOF
> + void foo (void) { }
> +EOF
> + libc_cv_no_omit_frame_pointer=no
> + if { ac_try='${CC-cc} $CFLAGS -S conftest.c -o conftest.s 1>&5'
> + { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
> + (eval $ac_try) 2>&5
> + ac_status=$?
> + $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
> + test $ac_status = 0; }; }; then
> + if grep 'push.*%ebp' conftest.s >/dev/null &&
> + grep 'pop.*%ebp' conftest.s >/dev/null; then
> + libc_cv_no_omit_frame_pointer=yes
> + fi
> + fi
> + rm -f conftest.c conftest.s
> +
> +fi
> +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_no_omit_frame_pointer" >&5
> +$as_echo "$libc_cv_no_omit_frame_pointer" >&6; }
> +if test $libc_cv_no_omit_frame_pointer = yes; then
> + $as_echo "#define NO_OMIT_FRAME_POINTER 1" >>confdefs.h
> +
> +fi
> +
> libc_cv_gcc_unwind_find_fde=yes
> ldd_rewrite_script=sysdeps/unix/sysv/linux/ldd-rewrite.sed
> diff --git a/sysdeps/unix/sysv/linux/i386/configure.ac b/sysdeps/unix/sysv/linux/i386/configure.ac
> index 1a11da6..06ccb7b 100644
> --- a/sysdeps/unix/sysv/linux/i386/configure.ac
> +++ b/sysdeps/unix/sysv/linux/i386/configure.ac
> @@ -3,5 +3,24 @@ GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
>
> arch_minimum_kernel=2.6.32
>
> +# Check if CFLAGS sets -fno-omit-frame-pointer
> +AC_CACHE_CHECK(for if compiler flags sets -fno-omit-frame-pointer,
> + libc_cv_no_omit_frame_pointer,
> + [cat > conftest.c << EOF
> + void foo (void) { }
> +EOF
> + libc_cv_no_omit_frame_pointer=no
> + if AC_TRY_COMMAND(${CC-cc} $CFLAGS -S conftest.c -o conftest.s 1>&AS_MESSAGE_LOG_FD); then
> + if grep 'push.*%ebp' conftest.s >/dev/null &&
> + grep 'pop.*%ebp' conftest.s >/dev/null; then
> + libc_cv_no_omit_frame_pointer=yes
> + fi
> + fi
> + rm -f conftest.c conftest.s
> + ])
I prefer something like
[hjl@gnu-6 tmp]$ cat ebp.c
void
foo (int i)
{
register int reg asm ("ebp") = i;
asm ("# %0" : : "r" (reg));
}
[hjl@gnu-6 tmp]$ gcc -S -m32 -Os ebp.c
ebp.c: In function ‘foo’:
ebp.c:6:1: error: bp cannot be used in asm here
}
^
[hjl@gnu-6 tmp]$ gcc -S -m32 -O2 ebp.c
[hjl@gnu-6 tmp]$
> +if test $libc_cv_no_omit_frame_pointer = yes; then
> + AC_DEFINE(NO_OMIT_FRAME_POINTER)
> +fi
How about something like CAN_USE_REGISTER_ASM_EBP?
> +
> libc_cv_gcc_unwind_find_fde=yes
> ldd_rewrite_script=sysdeps/unix/sysv/linux/ldd-rewrite.sed
> diff --git a/sysdeps/unix/sysv/linux/i386/sysdep.h b/sysdeps/unix/sysv/linux/i386/sysdep.h
> index baf4642..591aaf7 100644
> --- a/sysdeps/unix/sysv/linux/i386/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/i386/sysdep.h
> @@ -44,9 +44,9 @@
> /* Since GCC 5 and above can properly spill %ebx with PIC when needed,
> we can inline syscalls with 6 arguments if GCC 5 or above is used
> to compile glibc. Disable GCC 5 optimization when compiling for
> - profiling since asm ("ebp") can't be used to put the 6th argument
> - in %ebp for syscall. */
> -#if __GNUC_PREREQ (5,0) && !defined PROF
> + profiling or when -fno-omit-frame-pointer is used since asm ("ebp")
> + can't be used to put the 6th argument in %ebp for syscall. */
> +#if __GNUC_PREREQ (5,0) && !defined PROF && !defined NO_OMIT_FRAME_POINTER
> # define OPTIMIZE_FOR_GCC_5
> #endif
>
> @@ -611,7 +611,8 @@ struct libc_do_syscall_args
> #endif
>
> /* Consistency check for position-independent code. */
> -#if defined __PIC__ && !defined OPTIMIZE_FOR_GCC_5
> +#if defined __PIC__ && !defined OPTIMIZE_FOR_GCC_5 \
> + && !defined NO_OMIT_FRAME_POINTER
> # define check_consistency() \
> ({ int __res; \
> __asm__ __volatile__ \
> --
> 2.7.4
>
--
H.J.