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Message-ID: <20160511215311.GI21636@brightrain.aerifal.cx>
Date: Wed, 11 May 2016 17:53:12 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: Deduplicating __NR_* and SYS_* syscall defines
On Mon, May 09, 2016 at 07:26:37PM -0500, Bobby Bingham wrote:
> During the powerpc64 review, Rich mentioned wanting to replace the
> arch/*/bits/syscall.h files with .in files that would be preprocessed with
> something like:
>
> sed -e p -e s/__NR_/SYS_/ < $< > $@
>
> This would eliminate a lot of intra-file duplication here.
>
> I took a look, and this won't quite work as-is, because the following
> lines in the arm version would end up outputting duplicate definitions:
>
> #define __ARM_NR_breakpoint 0x0f0001
> #define __ARM_NR_cacheflush 0x0f0002
> #define __ARM_NR_usr26 0x0f0003
> #define __ARM_NR_usr32 0x0f0004
> #define __ARM_NR_set_tls 0x0f0005
This is easily fixed by something like:
sed -e /__NR_/p -e s/__NR_/SYS_/ < $< > $@
> Same thing for this line in x32:
>
> #define __X32_SYSCALL_BIT 0x40000000
In general we've tried to eliminate this sort of macro and direct-code
the values. I would be in favor of doing the same for x32 I think. But
with my fixed sed command (above) I think that change is unnecssary
and orthogonal to the deduplication.
> I'm thinking something like the following awk script would work:
>
> {
> print
> }
>
> $1 ~ /^#(define|undef)$/ && $2 ~ /^__NR_/ {
> sub(/__NR_/, "SYS_", $2)
> print
> }
>
> The handling for #undef is for the x32 file. It looks like only the
> `#undef __NR_getdents' in that file is actually necessary, and even that
> could be avoided by just omitting the earlier line:
>
> #define __NR_getdents (__X32_SYSCALL_BIT + 78)
I don't see why any #undef is needed here; this looks like leftover
cruft that was not properly cleaned up. All the logic for replacing
syscall numbers belongs in src/internal/syscall.h or
arch/$ARCH/syscall_arch.h, I think.
> So maybe we can get rid of the #undefs there, and simplify the awk script
> accordingly.
>
> Thoughts on this approach? If this sounds ok, I'll submit a patch.
I'd rather use sed than awk if possible since it's more universally
available and understood.
Rich
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