From: Szabolcs Nagy <nsz@port70.net>
To: musl@lists.openwall.com
Subject: Re: pthread_getattr_np
Date: Mon, 1 Apr 2013 01:31:35 +0200 [thread overview]
Message-ID: <20130331233135.GK30576@port70.net> (raw)
In-Reply-To: <20130331205139.GI30576@port70.net>
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* 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
[-- Attachment #2: getstack.c --]
[-- Type: text/x-csrc, Size: 1258 bytes --]
#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;
}
prev parent reply other threads:[~2013-03-31 23:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-31 17:35 pthread_getattr_np Szabolcs Nagy
2013-03-31 18:07 ` pthread_getattr_np Rich Felker
2013-03-31 20:51 ` pthread_getattr_np Szabolcs Nagy
2013-03-31 21:00 ` pthread_getattr_np Rich Felker
2013-03-31 21:37 ` pthread_getattr_np Szabolcs Nagy
2013-03-31 23:31 ` Szabolcs Nagy [this message]
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