Bug 170052 - elf_core_dump is a stack hog (1192 bytes)
elf_core_dump is a stack hog (1192 bytes)
Product: Red Hat Enterprise Linux 3
Classification: Red Hat
Component: kernel (Show other bugs)
i386 Linux
medium Severity medium
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Assigned To: Eric Sandeen
Brian Brock
Depends On:
  Show dependency treegraph
Reported: 2005-10-06 16:31 EDT by Eric Sandeen
Modified: 2007-11-30 17:07 EST (History)
2 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2007-02-23 16:34:37 EST
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
elf_core_dump stack reduction patch (5.91 KB, patch)
2005-10-06 16:35 EDT, Eric Sandeen
no flags Details | Diff

  None (edit)
Description Eric Sandeen 2005-10-06 16:31:09 EDT
Please note: I'm submitting this as a suggestion from an RHEL3 user, not as
a corporate request from SGI.

Description of problem:

elf_core_dump uses over 1k of stack (about 20% of what's available) on ia32,
due to large stack variables.  Dumping core to a filesystem that is over
stacked volume managers, or over a networked filesytem could cause the stack
to overflow.

A patch went into the 2.5 series to remedy this:


I've attached a backport of this patch that gets elf_core_dump down under 200
bytes.  It was quick work and could bear some scrutiny that I'm sure you'd
give it anyway.  :)

Version-Release number of selected component (if applicable):



Comment 1 Eric Sandeen 2005-10-06 16:35:14 EDT
Created attachment 119685 [details]
elf_core_dump stack reduction patch

er, try that patch attachment one more time.
Comment 2 John Hesterberg 2007-02-15 11:42:09 EST
Eric, still an issue?
Do you want to push as a RH employee now?
Comment 3 Eric Sandeen 2007-02-15 12:30:53 EST
Yep looks like it's still an issue...

c0191f50 <elf_core_dump>:
c0191f50:       55                      push   %ebp
c0191f51:       57                      push   %edi
c0191f52:       56                      push   %esi
c0191f53:       53                      push   %ebx
c0191f54:       bb 00 e0 ff ff          mov    $0xffffe000,%ebx
c0191f59:       21 e3                   and    %esp,%ebx
c0191f5b:       81 ec ac 04 00 00       sub    $0x4ac,%esp

1196 bytes... ouch.

I'll see what people think of fixing this.  Maybe I can come up with a non-cxfs
testcase ;-)
Comment 5 Eric Sandeen 2007-02-23 14:49:14 EST
The problem isn't the stack above, it's what's below - 

        ... and down into whatever stacked IO stuff you may have

OTOH 2.4.21 still has 8k to work withg, right, so it's not quite as bad (which
is probably why this -was- cleaned up upstream in 2.6)

If nobody's hit it in the wild on RHEL3, perhaps it's not worth worrying about
at this point.
Comment 8 Eric Sandeen 2007-02-23 16:34:37 EST
If this hasn't been an issue for our customers yet, it's probably not worth the

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