From mboxrd@z Thu Jan  1 00:00:00 1970
X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/3025
Path: news.gmane.org!not-for-mail
From: Szabolcs Nagy <nsz@port70.net>
Newsgroups: gmane.linux.lib.musl.general
Subject: Re: pthread_getattr_np
Date: Mon, 1 Apr 2013 01:31:35 +0200
Message-ID: <20130331233135.GK30576@port70.net>
References: <20130331173518.GH30576@port70.net>
 <20130331180717.GI20323@brightrain.aerifal.cx>
 <20130331205139.GI30576@port70.net>
Reply-To: musl@lists.openwall.com
NNTP-Posting-Host: plane.gmane.org
Mime-Version: 1.0
Content-Type: multipart/mixed; boundary="+HP7ph2BbKc20aGI"
X-Trace: ger.gmane.org 1364772710 14138 80.91.229.3 (31 Mar 2013 23:31:50 GMT)
X-Complaints-To: usenet@ger.gmane.org
NNTP-Posting-Date: Sun, 31 Mar 2013 23:31:50 +0000 (UTC)
To: musl@lists.openwall.com
Original-X-From: musl-return-3026-gllmg-musl=m.gmane.org@lists.openwall.com Mon Apr 01 01:32:18 2013
Return-path: <musl-return-3026-gllmg-musl=m.gmane.org@lists.openwall.com>
Envelope-to: gllmg-musl@plane.gmane.org
Original-Received: from mother.openwall.net ([195.42.179.200])
	by plane.gmane.org with smtp (Exim 4.69)
	(envelope-from <musl-return-3026-gllmg-musl=m.gmane.org@lists.openwall.com>)
	id 1UMRjR-0006LJ-1J
	for gllmg-musl@plane.gmane.org; Mon, 01 Apr 2013 01:32:13 +0200
Original-Received: (qmail 17988 invoked by uid 550); 31 Mar 2013 23:31:47 -0000
Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm
Precedence: bulk
List-Post: <mailto:musl@lists.openwall.com>
List-Help: <mailto:musl-help@lists.openwall.com>
List-Unsubscribe: <mailto:musl-unsubscribe@lists.openwall.com>
List-Subscribe: <mailto:musl-subscribe@lists.openwall.com>
Original-Received: (qmail 17980 invoked from network); 31 Mar 2013 23:31:47 -0000
Content-Disposition: inline
In-Reply-To: <20130331205139.GI30576@port70.net>
User-Agent: Mutt/1.5.21 (2010-09-15)
Xref: news.gmane.org gmane.linux.lib.musl.general:3025
Archived-At: <http://permalink.gmane.org/gmane.linux.lib.musl.general/3025>


--+HP7ph2BbKc20aGI
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

* Szabolcs Nagy <nsz@port70.net> [2013-03-31 22:51:39 +0200]:
> 1) parse /proc/self/maps which gives the current [low,high] mapping
> and 'prev' the high end of the last mapping below the stack
> 2) if we are the main thread check if low <= sp <= high
> 3) check rlimit
> 
> lowend = min(max(prev, high-rlimit, high-1G), low)

attached a getstack for the main thread

--+HP7ph2BbKc20aGI
Content-Type: text/x-csrc; charset=us-ascii
Content-Disposition: attachment; filename="getstack.c"

#include <stdio.h>
#include <limits.h>
#include <sys/resource.h>

#ifndef PAGE_SIZE
#include <unistd.h>
#define PAGE_SIZE sysconf(_SC_PAGE_SIZE)
#endif

/* get the stack [start,end] of the main thread:
   start is heuristic (smallest possible based on current rlimit
   and current mappings, but stack size is limited for sanity)
   end is precise, parsing /proc may fail */
static int getstack(size_t *start, size_t *end)
{
	size_t limit, prevend;
	struct rlimit r;
	FILE *f;
	char buf[PATH_MAX+80], s[8];
	int n;

	f = fopen("/proc/self/maps", "re");
	if (!f)
		return -1;
	n = 0;
	while (fgets(buf, sizeof buf, f)) {
		n = sscanf(buf, "%zx-%zx %*s %*s %*s %*s %7s", start, end, s);
		if (n >= 2) {
			if (n == 3 && strcmp(s, "[stack]") == 0)
				break;
			prevend = *end;
		}
		n = 0;
	}
	fclose(f);
	if (n == 0)
		return -1;

	limit = 100 << 20; /* 100MB stack limit */
	if (getrlimit(RLIMIT_STACK, &r)==0 && r.rlim_cur < limit)
		limit = r.rlim_cur & -PAGE_SIZE;
	if (limit > *end) limit = *end;
	if (prevend < *end - limit) prevend = *end - limit;
	if (*start > prevend) *start = prevend;
	return 0;
}

int main()
{
	size_t s,e;

	if (getstack(&s, &e)) {
		printf("getstack failed\n");
		return -1;
	}
	printf("%zx-%zx %zu\n", s, e, e-s);
	return 0;
}

--+HP7ph2BbKc20aGI--