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Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files |
Date: |
Sun, 26 May 2013 10:35:40 +0300 |
On Sat, May 25, 2013 at 05:32:24PM +0000, Blue Swirl wrote:
> On Wed, May 22, 2013 at 11:35 AM, Michael S. Tsirkin <address@hidden> wrote:
> > On Wed, May 22, 2013 at 01:12:15PM +0200, Paolo Bonzini wrote:
> >> Il 22/05/2013 13:09, Michael S. Tsirkin ha scritto:
> >> > > Usually I do the same---I just do slightly more thorough testing for
> >> > > configure patches.
> >> >
> >> > I've no idea what happens with ccache on a crash by the way.
> >> > It's possible that it's careful to do renames in order to not leave
> >> > corrupted output files behind.
> >>
> >> It doesn't, it leave 0-sized files. (Or at least it didn't last time
> >> power failed during a compilation. :))
> >>
> >> Paolo
> >
> > Well looking at the source, there's quite a bit of
> > handling of renames, so maybe ccache hackers will be
> > interested in fixing this.
> >
> > Manpage says:
> > It should be noted that ccache is susceptible to general storage
> > problems. If a bad object file sneaks into the cache for some
> > reason, it
> > will of course stay bad. Some possible reasons for erroneous object
> > files are bad hardware (disk drive, disk controller, memory, etc),
> > buggy
> > drivers or file systems, a bad CCACHE_PREFIX command or compiler
> > wrapper.
> >
> > ...
> >
> >
> > There are no reported issues about ccache producing broken object
> > files reproducibly. That doesn’t mean it can’t happen, so if you find
> > a repeatable case, please report it.
> >
> > power failure is not listed ...
>
> Neither is kill -9 issued by evil BOFH.
So presumably ccache will not fill with junk if you do this.
> IIRC I've also had bad builds
> and weird errors because the disk was almost completely full (not
> necessarily due to ccache). Once I overclocked a machine but I had to
> reduce the speed because of random compile errors.
This could be a parallel build, and possibly we have some
missing dependencies in the makefile.
>
> But I think your patch is way too simple to cover possible failure
> cases when you can't trust the compile environment.
That's not the intent. Merely to address the common failure
which I personally observe all the time.
> Maybe you should
> build in two separate directories and compare the resulting objects or
> just the final executables. For added paranoia, build using two
> machines which have different set of components from different
> manufacturers, but identical userland.
>
> Another way to handle this would be to enhance GCC and linker to use
> atomic operations when producing or combining object files. The tools
> could also print a SHA of the object which the next user should
> verify. Even better, the object files should include a robust checksum
> to ensure integrity.
I think we can make the makefile more robust. It can create a temporary
file in same directory and rename when ready. This will prevent
corrupted files from appearing in the first place.
> >
> > --
> > MST
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, (continued)
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Michael S. Tsirkin, 2013/05/22
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Paolo Bonzini, 2013/05/22
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Michael S. Tsirkin, 2013/05/22
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Paolo Bonzini, 2013/05/22
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Michael S. Tsirkin, 2013/05/22
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Paolo Bonzini, 2013/05/22
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Michael S. Tsirkin, 2013/05/22
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Paolo Bonzini, 2013/05/22
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Michael S. Tsirkin, 2013/05/22
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Blue Swirl, 2013/05/25
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Peter Maydell, 2013/05/26
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Michael S. Tsirkin, 2013/05/26
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Stefan Weil, 2013/05/26
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Michael S. Tsirkin, 2013/05/26
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Peter Maydell, 2013/05/26
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Michael S. Tsirkin, 2013/05/26
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Blue Swirl, 2013/05/26
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Michael S. Tsirkin, 2013/05/26
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Blue Swirl, 2013/05/26
- Re: [Qemu-devel] [PATCH] makefile: detect corrupted elf files, Michael S. Tsirkin, 2013/05/26