2.6.25-rc3-mm1 - PROFILE_LIKELY redux..

[Valdis.Kletnieks@vt.edu]

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On Tue, 04 Mar 2008 01:19:28 PST, Andrew Morton said:
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.25-rc3/2.6.25-rc3-mm1/

x86_64, mostly 64-bit userspace, Dell Latitude D820, T7200 Core2 Duo...

So I gave CONFIG_PROFILE_LIKELY another try, and this time the thing actually
booted and got into userspace, but stuff started dying in rc.sysinit.

According to dmesg, they all died at the same place:

[    4.841459] rename_device[686]: segfault at ffffffffff7009be ip ffffffffff7009be sp 7fff7ccfb958 error 14
[    4.842384] rename_device[984]: segfault at ffffffffff7009be ip ffffffffff7009be sp 7fffb6fe9c68 error 14
[    4.843298] rename_device[981]: segfault at ffffffffff7009be ip ffffffffff7009be sp 7fffc18504c8 error 14
[    4.844184] rename_device[983]: segfault at ffffffffff7009be ip ffffffffff7009be sp 7fff512c8f48 error 14
[    6.099486] rename_device[1513]: segfault at ffffffffff7009be ip ffffffffff7009be sp 7fff47e88ad8 error 14
[    5.769289] rename_device[1516]: segfault at ffffffffff7009be ip ffffffffff7009be sp 7fffa317edd8 error 14
[    7.457229] fsck.ext3[1576]: segfault at ffffffffff7009be ip ffffffffff7009be sp 7fff3be947f8 error 14

(Note that not everything died - some renames, an fsck, and maybe I missed
something - but a lot of other stuff worked (dmesg, grep, cat, uname that I
ran, and a lot of things that rc.sysinit invoked - so that may tell us
something...)

/proc/self/maps says that's near:

ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]

And my System.map says:

ffffffff80855a0c A __bss_stop
ffffffff80855a0c A _end
ffffffffff600000 T vgettimeofday
ffffffffff600100 t vread_tsc
ffffffffff600122 t vread_hpet
ffffffffff600140 D __vsyscall_gtod_data
ffffffffff600400 T vtime
ffffffffff600800 T vgetcpu
ffffffffff600870 D __vgetcpu_mode
ffffffffff600880 D __jiffies
ffffffffff600c00 T venosys_1
ffffffffff700000 A VDSO64_PRELINK
ffffffffff7005b0 A VDSO64_jiffies
ffffffffff7005b8 A VDSO64_vgetcpu_mode
ffffffffff7005c0 A VDSO64_vsyscall_gtod_data
<file ends there>

So we're in the same 4K as the VDSO64_* values, but some 0x4fe past the
gtod_data.  Anybody got a hint as to what the heck it was doing?



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