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Re: PowerPC SIGSTKSZ
- From: "Ryan S. Arnold" <ryan dot arnold at gmail dot com>
- To: Alan Modra <amodra at gmail dot com>
- Cc: libc-alpha <libc-alpha at sourceware dot org>
- Date: Tue, 13 Aug 2013 09:11:07 -0500
- Subject: Re: PowerPC SIGSTKSZ
- References: <20130809045657 dot GD3294 at bubble dot grove dot modra dot org>
On Thu, Aug 8, 2013 at 11:56 PM, Alan Modra <amodra@gmail.com> wrote:
> This copies the sparc version of sigstack.h, which gives powerpc
> #define MINSIGSTKSZ 4096
> #define SIGSTKSZ 16384
>
> Before the VSX changes, struct rt_sigframe size was 1920 plus 128 for
> __SIGNAL_FRAMESIZE giving ppc64 exactly the default MINSIGSTKSZ of
> 2048.
>
> After VSX, ucontext increased by 256 bytes. Oops, we're over
> MINSIGSTKSZ, so powerpc has been using the wrong value for quite a
> while. Add another ucontext for TM and rt_sigframe is now at 3872,
> giving actual MINSIGSTKSZ of 4000.
>
> The glibc testcase that I was looking at was tst-cancel21, which
> allocates 2*SIGSTKSZ (not because the test is trying to be
> conservative, but because the test actually has nested signal stack
> frames). We blew the allocation by 48 bytes when using current
> mainline gcc to compile glibc (le ppc64).
>
> The required stack depth in _dl_lookup_symbol_x from the top of the
> next signal frame was 10944 bytes. I guess you'd want to add 288 to
> that, implying an actual SIGSTKSZ of 11232.
>
> * sysdeps/unix/sysv/linux/powerpc/bits/sigstack.h: New file.
>
> diff --git a/sysdeps/unix/sysv/linux/powerpc/bits/sigstack.h b/sysdeps/unix/sysv/linux/powerpc/bits/sigstack.h
> new file mode 100644
> index 0000000..33be9e8
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/powerpc/bits/sigstack.h
> @@ -0,0 +1,54 @@
> +/* sigstack, sigaltstack definitions.
> + Copyright (C) 1998-2013 Free Software Foundation, Inc.
> + 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/>. */
> +
> +#ifndef _SIGNAL_H
> +# error "Never include this file directly. Use <signal.h> instead"
> +#endif
> +
> +
> +/* Structure describing a signal stack (obsolete). */
> +struct sigstack
> + {
> + void *ss_sp; /* Signal stack pointer. */
> + int ss_onstack; /* Nonzero if executing on this stack. */
> + };
> +
> +
> +/* Possible values for `ss_flags.'. */
> +enum
> +{
> + SS_ONSTACK = 1,
> +#define SS_ONSTACK SS_ONSTACK
> + SS_DISABLE
> +#define SS_DISABLE SS_DISABLE
> +};
> +
> +/* Minimum stack size for a signal handler. */
> +#define MINSIGSTKSZ 4096
> +
> +/* System default stack size. */
> +#define SIGSTKSZ 16384
> +
> +
> +/* Alternate, preferred interface. */
> +typedef struct sigaltstack
> + {
> + void *ss_sp;
> + int ss_flags;
> + size_t ss_size;
> + } stack_t;
I tested a version of this as well for PowerPC. Please commit this.
I'd like to have this backported to glibc 2.17 glibc 2.18.
Ryan S. Arnold