From: Sergey Bugaev <bugaevc@gmail.com>
To: Samuel Thibault <samuel.thibault@gnu.org>
Cc: bug-hurd@gnu.org, libc-alpha@sourceware.org,
"Flávio Cruz" <flaviocruz@gmail.com>
Subject: Re: [RFC PATCH glibc 9/12] mach: Look for mach_i386.defs on x86_64 too
Date: Sun, 12 Feb 2023 18:38:03 +0300 [thread overview]
Message-ID: <CAN9u=HeCOHKP8M4foPCPYFtwCKH1kkBgx9+4DCOP1pgFORQmpg@mail.gmail.com> (raw)
In-Reply-To: <20230212150710.zuzw5nqdtwvflkrj@begin>
> > # Translate GNU names for CPUs into the names used in Mach header files.
> > -mach-machine = $(patsubst powerpc,ppc,$(base-machine))
> > +mach-machine := $(patsubst powerpc,ppc,$(base-machine))
> > +mach-machine := $(patsubst x86_64,i386,$(mach-machine))
>
> Mmm, no, it's not actually a translation. What exactly does this fix?
The only thing the mach-machine variable is used for (as the comment
above it kind of explains) is for guessing the include guard name in
the machine-specific Mach header. They need this because, uh,
For generating mach-syscalls.mk, the build system passes '#include
<mach/syscall_sw.h>' to the compiler to be macro-expanded.
<mach/syscall_sw.h> contains lines like
kernel_trap(mach_msg_trap,-25,7), and at the very top, this:
/*
* The machine-dependent "syscall_sw.h" file should
* define a macro for
* kernel_trap(trap_name, trap_number, arg_count)
* which will expand into assembly code for the
* trap.
*
* N.B.: When adding calls, do not put spaces in the macros.
*/
#include <mach/machine/syscall_sw.h>
So when using <mach/syscall_sw.h> normally, those kernel_trap() macros
get expanded into arch-specific assembly definitions, such as on i386:
#define kernel_trap(trap_name,trap_number,number_args) \
ENTRY(trap_name) \
movl $ trap_number,%eax; \
SVC; \
ret; \
END(trap_name)
Now back to the glibc buildsystem and the generation of
mach-syscalls.mk: the glibc buildsystem preprocesses
<mach/syscall_sw.h> (the one that contains all those kernel_trap ()
"calls") with the -D_MACH_`echo $(mach-machine) | tr a-z
A-Z`_SYSCALL_SW_H_=1 incantation. This expands to something like
-D_MACH_I386_SYSCALL_SW_H_, which "fakes" the include guard of the
<mach/machine/syscall_sw.h>! So those kernel_trap () "calls" do not
get expanded, and the glibc buildsystem then postprocesses them with a
sed invocation to strip those kernel_trap () calls:
sed -n -e 's/^kernel_trap(\(.*\),\([-0-9]*\),\([0-9]*\))$$/\1 \2 \3/p'
And *that* (faking the include guard) is what the mach-machine
variable is used for. As another comment there says, "Go kludges!!!"
Since mach/machine/syscall_sw.h is the i386 version on x86_64 (or --
is it not supposed to be?), the _MACH_I386_SYSCALL_SW_H_ guard is the
one to fake, hence setting mach-machine to i386.
P.S. As you can see, even when the patch is a simple one-line change,
there can be quite a story (and some pulled hairs) behind it :)
> To build a 64bit glibc, we'll use headers installed by a 64bit gnumach,
> i.e. into /usr/include/x86_64-gnu/
Yes, sure, I'm building with the headers from the 64-bit Mach (gnumach
master configured with --host=x86_64-gnu).
Sergey
> I have applied the rest, thanks!
>
> Samuel
next prev parent reply other threads:[~2023-02-12 15:38 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-12 11:10 [RFC PATCH 0/12] Towards glibc on x86_64-gnu Sergey Bugaev
2023-02-12 11:10 ` [RFC PATCH glibc 1/12] hurd: Refactor readlinkat() Sergey Bugaev
2023-02-12 14:49 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH glibc 2/12] hurd: Use mach_msg_type_number_t where appropriate Sergey Bugaev
2023-02-12 14:52 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH glibc 3/12] mach, hurd: Cast through uintptr_t Sergey Bugaev
2023-02-12 14:55 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH glibc 4/12] hurd: Fix xattr error value Sergey Bugaev
2023-02-12 14:56 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH glibc 5/12] htl: Fix semaphore reference Sergey Bugaev
2023-02-12 14:57 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH hurd 6/12] hurd: Fix modes_t and speeds_t types on 64-bit Sergey Bugaev
2023-02-12 15:00 ` Samuel Thibault
2023-02-12 15:15 ` Sergey Bugaev
2023-02-12 15:22 ` Samuel Thibault
2023-02-12 16:13 ` Sergey Bugaev
2023-02-12 16:30 ` Samuel Thibault
2023-02-12 19:03 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH mig 7/12] Drop -undef -ansi from cpp flags Sergey Bugaev
2023-02-12 15:01 ` Samuel Thibault
2023-02-12 18:43 ` Flávio Cruz
2023-02-12 18:44 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH mig 8/12] Set max type alignment to sizeof(long) Sergey Bugaev
2023-02-12 11:10 ` [RFC PATCH glibc 9/12] mach: Look for mach_i386.defs on x86_64 too Sergey Bugaev
2023-02-12 15:07 ` Samuel Thibault
2023-02-12 15:38 ` Sergey Bugaev [this message]
2023-02-12 15:46 ` Samuel Thibault
2023-02-12 16:01 ` Sergey Bugaev
2023-02-16 20:22 ` Joseph Myers
2023-02-12 11:10 ` [RFC PATCH glibc 10/12] hurd: Set up the basic tree for x86_64-gnu Sergey Bugaev
2023-02-12 15:15 ` Samuel Thibault
2023-02-12 11:10 ` [RFC PATCH glibc 11/12] hurd, htl: Add some x86_64-specific code Sergey Bugaev
2023-02-12 16:11 ` Samuel Thibault
2023-02-12 16:25 ` Sergey Bugaev
2023-02-12 16:36 ` Samuel Thibault
2023-02-12 16:40 ` Florian Weimer
2023-02-12 16:46 ` Samuel Thibault
2023-02-12 19:29 ` Florian Weimer
2023-02-12 19:37 ` Samuel Thibault
2023-02-12 16:51 ` Sergey Bugaev
2023-02-12 17:02 ` Samuel Thibault
2023-02-12 17:06 ` Sergey Bugaev
2023-02-12 11:10 ` [RFC PATCH glibc 12/12] C11 thrd: Downgrade the default alignment of mtx_t Sergey Bugaev
2023-02-12 15:18 ` Samuel Thibault
2023-02-12 15:52 ` Sergey Bugaev
2023-02-12 16:29 ` Samuel Thibault
2023-02-12 16:12 ` [RFC PATCH 0/12] Towards glibc on x86_64-gnu Samuel Thibault
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