From owner-freebsd-arch  Sun Nov  5 23:50:19 2000
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Date: Sun, 05 Nov 2000 23:50:15 -0800
From: Marcel Moolenaar <marcel@cup.hp.com>
Organization: Hewlett-Packard
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To: arch@FreeBSD.org
Subject: Request for Review: ABI/arch dependent MINSIGSTKSZ
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Hi,

With the different ABIs and architectures and thus different signal
frames or stack requirements, having a single MINSIGSTKSZ is not really
sufficient. I've put a patch on:

	http://people.FreeBSD.org/~marcel/minsigstksz.diff

to allow for a more flexible or variable MINSIGSTKSZ. In general this is
what's changing:

o  Add a sv_minsigstksz field to struct sysentvec,
o  Have sigaltstack use this field to compare the
   supplied stack size with the minimum required.
o  Move MINSIGSTKSZ from <sys/signal.h> to
   <machine/signal.h> to better have it match the
   requirements of the different architectures.
   Especially the ia64 ports needs enough stack.
o  Define a MINSIGSTKSZ for each "emulator" to the
   value defined by the "emulated" OS for improved
   compatibility.

A note about the values of MINSIGSTKSZ used in the patch:

o  alpha & ia64: sizeof(struct sigframe) is rounded
   to the nearest multiple of 1024. A multiplication
   of 4 allows for recursion/nesting and is somewhat
   arbitrary.
o  i386: sizeof(struct sigframe) is rounded to the
   nearest multiple of 512. A multiplication of 4
   allows for recursion/nesting and is somewhat
   arbitrary.
o  iBCS2: No real value known. Use 8192 to maintain
   current behaviour.
o  OSF1 & SVR4: Wait for maintainers to report real
   values before committing.
o  Linux: Values are equal to those used in a Linux
   kernel.

Credit: The idea of a variable MINSIGSTKSZ is bde's, not mine.

Your comments please,

-- 
Marcel Moolenaar
  mail: marcel@cup.hp.com / marcel@FreeBSD.org
  tel:  (408) 447-4222


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