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    SubjectRe: [PATCH v2 16/31] arm64: ELF definitions
    Date
    On Tuesday 21 August 2012, Catalin Marinas wrote:
    > On Thu, Aug 16, 2012 at 01:37:53PM +0100, Arnd Bergmann wrote:
    > > On Thursday 16 August 2012, Will Deacon wrote:
    > > > > This looks wrong: PER_LINUX/PER_LINUX32 decides over the output of the
    > > > > uname system call, while TIF_32BIT decides over the instruction set
    > > > > when returning to user space. You definitely should not set the personality
    > > > > to the value you pass from the elf loader. Instead, just do
    > > > >
    > > > > #define SET_PERSONALITY(ex) clear_thread_flag(TIF_32BIT);
    > > > > #defined COMPAT_SET_PERSONALITY(ex) set_thread_flag(TIF_32BIT);
    > > >
    > > > In this case, won't uname be incorrect (aarch64l) for aarch32 tasks (which
    > > > expect something like armv8l)?
    > >
    > > No, the uname output is meant to tell you about the system, not the
    > > instruction set that you are using (you already know that in compiled
    > > code).
    >
    > OK, so we assumed that compat tasks should get a uname as close as
    > possible to a 32-bit system, i.e. armv8l, for full compatibility. This
    > would allow us to run something like 32-bit Debian on an AArch64 kernel
    > without worrying about any scripts failing.

    You can still do that, just boot with init="/sbin/setarch armv7 /sbin/init".

    > But I can see on x86 that it always reports x86_64 even if the task is
    > x86_32.

    Not just x86, the same behavior is used on powerpc, s390, mips, sparc and
    parisc. Not sure about tile though.

    Arnd


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