[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20160416170934.GG21636@brightrain.aerifal.cx>
Date: Sat, 16 Apr 2016 13:09:34 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH v2] add powerpc64 port
On Fri, Apr 15, 2016 at 10:38:33PM +0200, Szabolcs Nagy wrote:
> * Szabolcs Nagy <nsz@...t70.net> [2016-04-14 15:42:13 +0200]:
> > * Bobby Bingham <koorogi@...rogi.info> [2016-04-14 03:01:38 -0500]:
> > >
> > > How important is it to match glibc here?
> > >
> >
> > i think we don't care about abi compat
> > (but it might be interesting to check how much abi
> > difference there is between glibc and musl, i can
> > do this if i can build a musl+glibc toolchain)
> >
>
> attached some c++ abi comparisions
Thanks!
> (the comparision was not entirely clean, it involved
> various manual hacks, but most types and functions
> should be compared correctly glibc vs musl)
>
> two interesting gcc warnings:
>
> powerpc64 elf_vrreg_t (both musl and glibc):
> note: the ABI of passing aggregates with 16-byte alignment has changed in GCC 5
This could be mildly problematic, but it's in a junk interface that's
unlikely to be used cross-library anyway.
> x86_64 struct inotify_event (musl only):
> note: the ABI of passing struct with a flexible array member has changed in GCC 4.4
This looks irrelevant; passing the struct by value does not make sense.
> --- abi_type.powerpc64le.glibc 2016-04-15 21:00:27.432246225 +0100
> +++ abi_type.powerpc64le.musl 2016-04-15 20:57:39.000149371 +0100
> @@ -97 +96 @@
> -fexcept_t: unsigned int, unsigned int*, size (*) [4], align (*) [4]
> +fexcept_t: unsigned long, unsigned long*, size (*) [8], align (*) [8]
Is this right?
> @@ -100,2 +99,2 @@
> -fpos_t: _G_fpos_t, _G_fpos_t*, size (*) [16], align (*) [8]
> +fpos_t: _G_fpos64_t, _G_fpos64_t*, size (*) [16], align (*) [8]
You should probably be testing with -D_FILE_OFFSET_BITS=64. musl
implements that ABI, and it matters in a few places even on 64-bit
archs, like here.
> @@ -130 +130 @@
> -jmp_buf: __jmp_buf_tag*, __jmp_buf_tag (*) [1], size (*) [656], align (*) [16]
> +jmp_buf: __jmp_buf_tag*, __jmp_buf_tag (*) [1], size (*) [664], align (*) [8]
Let's fix at least alignment and hopefully size.
> @@ -141 +141 @@
> -mcontext_t: mcontext_t, mcontext_t*, size (*) [1272], align (*) [8]
> +mcontext_t: sigcontext, sigcontext*, size (*) [1528], align (*) [8]
IIRC on other archs we made an effort to make the tag here match ABI
(duplicating the struct def if needed). Not sure if it matters.
> @@ -183,2 +183,2 @@
> -pthread_rwlockattr_t: pthread_rwlockattr_t, pthread_rwlockattr_t*, size (*) [8], align (*) [8]
> +pthread_rwlockattr_t: pthread_rwlockattr_t, pthread_rwlockattr_t*, size (*) [8], align (*) [4]
Alignment difference was unintentional here but seems bad to try to
fix for existing archs and I don't want to make the pthread types
arch-specific; actually I want to move them to the shared
alltypes.h.in or new arch/generic* with just a dependency on 32/64
bit.
> -pthread_spinlock_t: int, int volatile*, size (*) [4], align (*) [4]
> +pthread_spinlock_t: int, int*, size (*) [4], align (*) [4]
Did glibc add volatile here? IIRC it was not there to begin with. If
so they broke their own C++ ABI. I'd like to change this too, and if
glibc did change it without anyone noticing/caring, we probably could
too.
> @@ -195 +195 @@
> -sem_t: sem_t, sem_t*, size (*) [32], align (*) [8]
> +sem_t: sem_t, sem_t*, size (*) [32], align (*) [4]
> @@ -229,2 +229,2 @@
> -cmsghdr: cmsghdr, cmsghdr*, size (*) [16], align (*) [8]
> +cmsghdr: cmsghdr, cmsghdr*, size (*) [16], align (*) [4]
This is likely going to hit the same issue we're trying to debug on
mips64.
> @@ -416 +417 @@
> -ucontext_t: ucontext, ucontext*, size (*) [1440], align (*) [8]
> +ucontext_t: ucontext, ucontext*, size (*) [1696], align (*) [8]
This may be a real problem. ucontext_t is ABI between kernel and
userspace and if it's wrong cancellation won't work right.
Rich
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
