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    SubjectRe: [RFC] status of execve() work - per-architecture patches solicited
    On 09/11/2012 02:49 AM, Al Viro wrote:
    > On Mon, Sep 10, 2012 at 11:40:11PM +1000, Greg Ungerer wrote:
    >> Hi Al,
    >> On 09/08/2012 04:20 AM, Al Viro wrote:
    >>> To architecture maintainers: please, review the current
    >>> situation in #execve2
    >>> and consider sending the corresponding patches for missing architectures.
    >> I can see you have some m68k patches in there as well.
    >> They tested good on standard m68k (under emulator) and good on non-mmu
    >> ColdFire. But it is geting an exception when I run on ColdFire with MMU
    >> enabled:
    >> ...
    >> Creating 1 MTD partitions on "RAM":
    >> 0x000000000000-0x0000001b8000 : "ROMfs"
    >> TCP: cubic registered
    >> NET: Registered protocol family 17
    >> VFS: Mounted root (romfs filesystem) readonly on device 31:0.
    >> *** FORMAT ERROR *** FORMAT=4
    >> Current process id is 1
    >> BAD KERNEL TRAP: 00000000
    >> Modules linked in:
    >> PC: [<0002562a>] 0x02562a
    >> SR: 2704 SP: 0383dfc4 a2: 00000000
    >> d0: 00000000 d1: 00000000 d2: 00000000 d3: 00000000
    >> d4: 00000000 d5: 00000000 a0: 00000000 a1: 00000000
    >> Process init (pid: 1, task=0383a000)
    >> Frame format=4 eff addr=00000000 pc=6000169a
    >> Stack from 0383e000:
    >> Call Trace:
    >> Code: 6610 4cd7 073e 4fef 0020 201f 588f dfdf <4e73> 2228 0004 46fc
    >> 2000 0801 0007 66ff ffff c2ea 598f 4fef ffe8 48d7 78c0 486f
    >> Disabling lock debugging due to kernel taint
    >> It is trapping at the return from exception (rte) in Lreturn.
    >> Looks like it doesn't like the "format" field of the new stack frame
    >> for some reason. If I get a few minutes tomorrow I'll dig into it.
    > Interesting... What it should get is format 0, same as before the change.

    Thats a problem on ColdFire. The format field of the stack frame would
    normally be 0x4 for a long-word aligned user stack pointer. The current
    start_thread code doesn't set this on the ColdFire/MMU case, though we
    do for the non-mmu case. The old code inherited this from the stack
    frame of exec calling process.

    So I will rework the m68k start_thread() code so it sets it explicitly
    for all ColdFire cases.

    With this fixed up the new exec code works in all cases I have tested
    with ColdFire/MMU then.

    > BTW, is there any convenient way to get an emulated coldfire-MMU system?

    I only test it on real hardware. But it looks like qemu has coldfire
    emulation. I haven't tried it, but as of version 1.0 it listed supported
    ColdFire CPU's as:


    The cfv4e core is capable of having an MMU, so maybe someone is working
    on it. I must go and check 1.2.0, it might be better.

    > For m68k I'm using aranym with sid/m68k from and it seems
    > to work fine these days, but that obviously won't do for coldfire - neither
    > the emulator itself, nor the userland (AFAICS, gcc will happily generate
    > instructions that use weird addressing modes unless told not to, so I would
    > be extremely surprised if normal debian m68k binaries would run on coldfire,
    > MMU or no MMU).

    Yeah, no way it will work without the appropriate compiler switches on
    when generating even userland binaries.


    > BTW, the same question goes for many other embedded targets - I'm using
    > qemu for arm and mips and hercules for s390; alpha, parisc, ppc32 and sparc64 -
    > on actual hardware, amd64 and i386 - on kvm guests (all with debian userland);
    > ia64 kinda-sorta works with ski, but it's very much imperfect... I think
    > sh (at least sh4) should be usable with qemu as well, but I hadn't set that
    > up yet. sparc32 is usable on qemu, but only with very old userland.
    > Everything else... In theory, quite a few ought to be usable if one
    > bootstraps uclinux userland with qemu, but I've no idea how well does that
    > work in practice. And seeing that e.g. FRV eval boards go for several
    > hundred dollars even on ebay, let alone from manufacturer, I'd rather not
    > add the actual hardware to the pile here ;-/
    > What do people actually use?
    > --
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