Path: ...!weretis.net!feeder9.news.weretis.net!news.quux.org!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Muttley@DastardlyHQ.org
Newsgroups: comp.unix.programmer
Subject: Re: (interposers): How to workaround the "strong symbols" problem?
Date: Mon, 20 Jan 2025 09:41:41 -0000 (UTC)
Organization: A noiseless patient Spider
Lines: 24
Message-ID: <vml5ol$31d1s$1@dont-email.me>
References: <vmeibp$33sam$1@news.xmission.com>
	<wwved112g19.fsf@LkoBDZeT.terraraq.uk>
	<vmetdr$341gl$1@news.xmission.com> <vmj4hg$2bf6s$1@gwaiyur.mb-net.net>
 <wwvsepessby.fsf@LkoBDZeT.terraraq.uk>
Injection-Date: Mon, 20 Jan 2025 10:41:41 +0100 (CET)
Injection-Info: dont-email.me; posting-host="814144b7c7b1a7e5b7bbd80827eada59";
	logging-data="3191868"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX18d1QCqZvcOmIadvc7AtB+N"
Cancel-Lock: sha1:1WSKwItwSuxbILck7j365C2qPHM=
Bytes: 2038

On Sun, 19 Jan 2025 16:04:33 +0000
Richard Kettlewell <invalid@invalid.invalid> wibbled:
>Marcel Mueller <news.5.maazl@spamgourmet.org> writes:
>> Am 18.01.25 um 01:42 schrieb Kenny McCormack:
>>> Right.  It seems to boil down to:
>>>      You can't interpose a syscall.
>>> I.e., so if a library function calls the syscall directly (rather
>>> than going through the Glibc wrapper), you can't interpose it.  This
>>> is, of course, as it should be.
>>
>> Hmm, it may be related to optimizations. Assuming the openat call is
>> inlined in another compilation unit there is no option to change this
>> at link time.
>
>Inlining and compiler optimization aren’t relevant here.
>
>“System call” can mean two things:
>
>1) The actual transfer to the kernel, via an instruction such as SYSCALL
>   (x86) or SVC (Arm). This is what appears in strace.

On a slight tangent, does anyone know of a good reference for how to use
the ptrace() call on Linux? The man page is somewhat obtuse.