x86_64: 32bit emulation problems

From: Bernd Schubert (bernd.schubert_at_pci.uni-heidelberg.de)
Date: 02/28/05

  • Next message: Hugh Dickins: "Re: [PATCH] allow vma merging with mlock et. al." 
    To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Andi Kleen <ak@muc.de>
Date:	Mon, 28 Feb 2005 21:54:03 +0100

    Hi,

    I'm just looking into a very strange problem. Some of our systems have
    athlon64 CPUs. Due to our diskless nfs environment we currently still prefer
    a 32bit userspace environment, but would like to be able to use a 64-bit
    chroot environment.

    Well, currently there seems to be a stat64() NFS problem when a x86_64 kernel
    is booted and stat64() comes from a 32bit libc.

    Here's just an example:

    hitch***:/home/bernd/src/tests# ./test_stat64 /mnt/test/yp
    stat() works fine.

    hitch***:/home/bernd/src/tests# ./test_stat32 /mnt/test/yp
    stat for /mnt/test/yp failed

    The test program looks rather simple:

    #include <sys/types.h>
    #include <sys/stat.h>
    #include <unistd.h>
    #include <stdio.h>
    #include <errno.h>
    #include <string.h>
    #include <stdlib.h>

    int main(int argc, char **argv)
    {
            char *dir;
            struct stat buf;

            dir = argv[1];

            if (stat (dir, &buf) == -1)
                    fprintf(stderr, "stat for %s failed \n", dir);
            else
                    fprintf(stderr, "stat() works fine.\n");
            return (0);
    }

    Here are the strace outputs:
    =====================

    32bit:
    ------
    hitch***:/home/bernd/src/tests# strace32 ./test_stat32 /mnt/test/yp
    execve("./test_stat32", ["./test_stat32", "/mnt/test/yp"], [/* 39 vars */]) =
    0
    uname({sys="Linux", node="hitch***", ...}) = 0
    brk(0) = 0x80ad000
    brk(0x80ce000) = 0x80ce000
    stat64("/mnt/test/yp", {st_mode=S_IFDIR|0755, st_size=2704, ...}) = 0
    write(2, "stat for /mnt/test/yp failed \n", 30stat for /mnt/test/yp failed
    ) = 30
    exit_group(0) = ?

    64bit:
    -------
    hitch***:/home/bernd/src/tests# strace ./test_stat64 /mnt/test/yp
    execve("./test_stat64", ["./test_stat64", "/mnt/test/yp"], [/* 39 vars */]) =
    0
    uname({sys="Linux", node="hitch***", ...}) = 0
    brk(0) = 0x572000
    brk(0x593000) = 0x593000
    stat("/mnt/test/yp", {st_mode=S_IFDIR|0755, st_size=2704, ...}) = 0
    write(2, "stat() works fine.\n", 19stat() works fine.
    ) = 19
    _exit(0) = ?

    Anyone having an idea whats going on? The ethereal capture also looks pretty
    normal. The kernel of this system is 2.6.9, but it also happens on another
    system with 2.6.11-rc5.
    As usual we are using unfs3 for /etc and /var, but for me that looks like a
    client problem. I'm even not sure if this is limited to NFS at all.

    Thanks in advance,
     Bernd
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  • Next message: Hugh Dickins: "Re: [PATCH] allow vma merging with mlock et. al."