Re: [Xen-devel] [PATCH v10 17/24] build_id: Provide ld-embedded build-ids

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.05.16 at 13:19, <wei.liu2@xxxxxxxxxx> wrote:
> On Mon, May 02, 2016 at 05:13:24AM -0600, Jan Beulich wrote:
>> >>> On 02.05.16 at 13:05, <wei.liu2@xxxxxxxxxx> wrote:
>> > On Mon, May 02, 2016 at 12:02:43AM -0600, Jan Beulich wrote:
>> >> >>> On 29.04.16 at 19:23, <konrad.wilk@xxxxxxxxxx> wrote:
>> >> > On Fri, Apr 29, 2016 at 10:38:07AM -0600, Jan Beulich wrote:
>> >> >> >>> On 27.04.16 at 21:27, <konrad.wilk@xxxxxxxxxx> wrote:
>> >> >> > @@ -304,6 +338,32 @@ int main(int argc, char **argv)
>> >> >> >      /*mem_siz = (u32)in64_phdr.p_memsz;*/
>> >> >> >      mem_siz = (u32)(final_exec_addr - in64_phdr.p_vaddr);
>> >> >> >  
>> >> >> > +    note_sz = note_base = offset = 0;
>> >> >> > +    if ( num_phdrs > 1 )
>> >> >> > +    {
>> >> >> > +        offset = in64_phdr.p_offset;
>> >> >> > +        note_base = in64_phdr.p_vaddr;
>> >> >> > +
>> >> >> > +        (void)lseek(infd, in64_ehdr.e_phoff+sizeof(in64_phdr), 
>> >> >> > SEEK_SET);
>> >> >> > +        do_read(infd, &in64_phdr, sizeof(in64_phdr));
>> >> >> > +        endianadjust_phdr64(&in64_phdr);
>> >> >> > +
>> >> >> > +        (void)lseek(infd, offset, SEEK_SET);
>> >> >> > +
>> >> >> > +        note_sz = in64_phdr.p_memsz;
>> >> >> > +        note_base = in64_phdr.p_vaddr - note_base;
>> >> >> > +
>> >> >> > +        if ( in64_phdr.p_offset > dat_siz || offset > 
>> >> >> > in64_phdr.p_offset )
>> >> >> > +        {
>> >> >> > +            fprintf(stderr, "Expected .note section within .text 
>> >> > section!\n" \
>> >> >> > +                    "Offset %ld not within %d!\n",
>> >> >> > +                    in64_phdr.p_offset, dat_siz);
>> >> >> 
>> >> >> This fails to build on a 32-bit build host (which is one of the two
>> >> >> post-commit, pre-push checks I normally do).
>> >> > 
>> >> > I hadn't realized that it was possible to build an 64-bit hypervisor on 
>> >> > 32-bit
>> >> > GCC toolchain. I've never done that - always built the hypervisor in 
>> >> > 64-bit 
>> >> > env and the 32-bit toolstack in 32-bit environment. Then booted it.
>> >> 
>> >> 32-bit toolchain? No. A 64-bit cross tool chain (similar to what I use
>> >> for ARM build testing, except that here I also actively run the
>> >> resulting hypervisor).
>> > 
>> > Then I'm a bit confused what you meant by "32-bit build host" in your
>> > previous email.
>> 
>> What's confusing you here? Running a 64-bit hypervisor and/or a
>> 64-bit kernel underneath a 32-bit distro is working quite fine.
>> 
> 
> Hmm... How did you discover that problem if you did not cross-compile
> with 32-bit toolchain? That's how I discovered the breakage.

Hmm, so maybe we're just meaning "32-bit" for different things: I
imply it to stand for the target architecture, but maybe you mean
the (build) host architecture instead. Konrad's original reply meant
to me that he somehow expected the _native_ tool chain on a
32-bit host to be capable of that (where host arch == target arch),
which in theory was possible too, but I don't think is in actual use
anywhere.

Jan


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